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1

Just Breathe Green: Measuring Transpiration Rates  

NSDL National Science Digital Library

Through multi-trial experiments, students are able to see and measure something that is otherwise invisible to themâseeing plants breathe. Student groups are given two small plants of native species and materials to enclose them after watering with colored water. After being enclosed for 5, 10 and 15 minutes, teams collect and measure the condensed water from the plants' "breathing," and then calculate the rates at which the plants breathe. A plant's breath is known as transpiration, which is the flow of water from the ground where it is taken up by roots (plant uptake) and then lost through the leaves. Students plot volume/time data for three different native plant species, determine and compare their transpiration rates to see which had the highest reaction rate and consider how a plant's unique characteristics (leaf surface area, transpiration rate) might figure into engineers' designs for neighborhood stormwater management plans.

Water Awareness Research and Education (WARE) Research Experience for Teachers (RET),

2

Transpiration: Water Movement Through Plants  

NSDL National Science Digital Library

Learn the basics of transpiration -- the transportation of water through plants from soil to leaves to atmosphere -- with this playful animation created by weed physiologist Tracy Sterling and animator Matt Byrnes. Interactive features allow you to explore the process including how changing environmental conditions can impact how fast water moves.

Tracy Sterling (New Mexico State University;)

2005-09-23

3

External Pressures Based on Leaf Water Potentials Do Not Induce Xylem Sap to Flow at Rates of Whole Plant Transpiration from Roots of Flooded or Well-drained Tomato and Maize Plants. Impact of Shoot Hydraulic Resistances  

Microsoft Academic Search

We tested the hypothesis that leaf water potentials (?L) are good guides to the positive pneumatic pressure needed to drive water flow through detopped root systems at the rate of whole plant transpiration. Unless sap flows at this rate, solute concentrations and rates of delivery are poor estimates of those carried by the transpiration stream of intact plants. In flooded

A. E. Tiekstra; M. A. Else; M. B. Jackson

2000-01-01

4

Hydraulic Limits on Maximum Plant Transpiration  

NASA Astrophysics Data System (ADS)

Photosynthesis occurs at the expense of water losses through transpiration. As a consequence of this basic carbon-water interaction at the leaf level, plant growth and ecosystem carbon exchanges are tightly coupled to transpiration. In this contribution, the hydraulic constraints that limit transpiration rates under well-watered conditions are examined across plant functional types and climates. The potential water flow through plants is proportional to both xylem hydraulic conductivity (which depends on plant carbon economy) and the difference in water potential between the soil and the atmosphere (the driving force that pulls water from the soil). Differently from previous works, we study how this potential flux changes with the amplitude of the driving force (i.e., we focus on xylem properties and not on stomatal regulation). Xylem hydraulic conductivity decreases as the driving force increases due to cavitation of the tissues. As a result of this negative feedback, more negative leaf (and xylem) water potentials would provide a stronger driving force for water transport, while at the same time limiting xylem hydraulic conductivity due to cavitation. Here, the leaf water potential value that allows an optimum balance between driving force and xylem conductivity is quantified, thus defining the maximum transpiration rate that can be sustained by the soil-to-leaf hydraulic system. To apply the proposed framework at the global scale, a novel database of xylem conductivity and cavitation vulnerability across plant types and biomes is developed. Conductivity and water potential at 50% cavitation are shown to be complementary (in particular between angiosperms and conifers), suggesting a tradeoff between transport efficiency and hydraulic safety. Plants from warmer and drier biomes tend to achieve larger maximum transpiration than plants growing in environments with lower atmospheric water demand. The predicted maximum transpiration and the corresponding leaf water potential compare well with measured peak transpiration and minimum water potentials across plant types and biomes, suggesting that plant water transport system and stomatal regulation co-evolved to meet peak atmospheric demands, thus sustaining carbon uptake while avoiding tissue damage even in such harsh conditions.

Manzoni, S.; Vico, G.; Katul, G. G.; Palmroth, S.; Jackson, R. B.; Porporato, A. M.

2011-12-01

5

Plant Transpiration and its Sensitivity to Increasing Carbon Dioxide Concentration at Leaf, Canopy and Regional Scales  

Microsoft Academic Search

This thesis assembles simulation models for plant transpiration and uses these models to investigate the sensitivity of transpiration rates to the elevation of atmospheric CO_2 concentration at leaf, canopy and regional scales. The leaf transpiration model assembly (LTMA) simulates stomatal conductance, leaf net photosynthesis, leaf boundary layer conductance, mass and energy transfer, leaf energy balance. The stomatal conductance model and

Xiwu Zhan

1995-01-01

6

Transpiration - Water Movement through Plants  

NSDL National Science Digital Library

This lesson and its animation follows the journey of water through a plant from its uptake by roots to its evaporation from the leaf surface. How this journey is altered by plant characteristics such as stomata and cuticles as well as by changes in the environment will be described.

7

Measuring Transpiration to Regulate Winter Irrigation Rates  

SciTech Connect

Periodic transpiration (monthly sums) in a young loblolly pine plantation between ages 3 and 6 was measured using thermal dissipation probes. Fertilization and fertilization with irrigation were better than irrigation alone in increasing transpiration of young loblolly pines during winter months, apparently because of increased leaf area in fertilized trees. Irrigation alone did not significantly increase transpiration compared with the non-fertilized and non-irrigated control plots.

Samuelson, Lisa [Auburn University

2006-11-08

8

How-to-Do-It: Using Computers in Measuring Transpiration Rate.  

ERIC Educational Resources Information Center

Described is an activity in which a computer is used to acquire temperature and humidity data useful in investigating transpiration in plants. Materials and procedures are discussed and examples of results are presented. Factors which influence the rate of transpiration are discussed. (CW)

Seligmann, Peter F.; Thompson, Steven R.

1989-01-01

9

Whole-plant capacitance, embolism resistance and slow transpiration rates all contribute to longer desiccation times in woody angiosperms from arid and wet habitats.  

PubMed

Low water potentials in xylem can result in damaging levels of cavitation, yet little is understood about which hydraulic traits have most influence in delaying the onset of hydraulic dysfunction during periods of drought. We examined three traits contributing to longer desiccation times in excised shoots of 11 species from two sites of contrasting aridity: (i) the amount of water released from plant tissues per decrease in xylem water potential (W?); (ii) the minimum xylem water potential preceding acute water stress (defined as P50L; water potential at 50% loss of leaf conductance); and (iii) the integrated transpiration rate between the points of full hydration and P50L (Wtime). The time required for species to reach P50L varied markedly, ranging from 1.3 h to nearly 3 days. W?, P50L and Wtime all contributed significantly to longer desiccation times, explaining 28, 22 and 50% of the variance in the time required to reach P50L. Interestingly, these three traits were nearly orthogonal to one another, suggesting that they do not represent alternative hydraulic strategies, but likely trade off with other ecological strategies not evaluated in this study. The majority of water lost during desiccation (60-91%) originated from leaves, suggesting an important role for leaf capacitance in small plants when xylem water potentials decrease below -2 MPa. PMID:24550089

Gleason, Sean M; Blackman, Chris J; Cook, Alicia M; Laws, Claire A; Westoby, Mark

2014-03-01

10

[Plant transpiration in a maize/soybean intercropping system measured with heat balance method].  

PubMed

In an experimental field with maize/soybean strip intercropping, the transpiration of maize and soybean plants was measured with sap flow gauge based on heat balance method. In the intercropping system, the diurnal change of the sap flow rates of the plants fitted single-peak curve in sunny day and multi-peak curve in cloudy day. The plant sap flow rates were affected by many environmental factors, among which, solar radiation was the most important meteorological factor. The daily sap flow per maize or soybean plant showed significant correlations with solar radiation, air temperature, relative humidity, wind speed, and soil heat flux. During the observation period (June 1-30, 2008), the mean daily transpiration of maize plant (1.44 mm x d(-1)) was about 1.8 times of that of soybean plant (0.79 mm x d(-1)). Maize transpiration and soybean transpiration contributed 64% and 36% to the total transpiration of the intercropping system, respectively. Due to the spatial variation of stem diameter and leaf area, it would be necessary to install more sap flow gauges to accurately measure the sap flow of maize and soybean plants. PMID:20707114

Gao, Yang; Duan, Ai-wang; Qiu, Xin-qiang; Zhang, Jun-peng; Sun, Jing-sheng; Wang, He-zhou

2010-05-01

11

Parameters determining plant transpiration under conditions of sufficient soil moisture  

NASA Astrophysics Data System (ADS)

The transpiration of a forest growth during the growing season when sufficient soil moisture is available can be estimated by means of a simple model on the basis of the requirement of water for cooling plants (Pražák et al., J. Hydrol., 162: 409-427, 1994). The properties of the plants in the model are described by means of a set of phenomenological parameters. In this paper, these parameters are discussed in detail together with the corresponding physical meaning. It is shown that, where only the amount of water used for the transpiration is of interest, the number of parameters can be reduced.

Pražák, J.; Šír, M.; Tesa?, M.

1996-09-01

12

Predicting the effects of gas diffusivity on photosynthesis and transpiration of plants grown under hypobaria  

NASA Astrophysics Data System (ADS)

As part of a Bio-regenerative Life Support System (BLSS) for long-term space missions, plants will likely be grown at reduced pressure. This low pressure will minimize structural requirements for growth chambers on missions to the Moon or Mars. However, at reduced pressures the diffusivity of gases increases. This will affect the rates at which CO2 is assimilated and water is transpired through stomata. To understand quantitatively the possible effects of reduced pressure on plant growth, CO2 and H2O transport were calculated for atmospheres of various total pressures (101, 66, 33, 22, 11 kPa) and CO2 concentrations (0.04, 0.1 and 0.18 kPa). The diffusivity of a gas is inversely proportional to total pressure and shows dramatic increases at pressures below 33 kPa (1/3 atm). A mathematical relationship based on the principle of thermodynamics was applied to low pressure conditions and can be used for calculating the transpiration and photosynthesis of plants grown in hypobaria. At 33 kPa total pressure, the stomatal conductance increases by a factor of three with the boundary layer conductance increasing by a factor of ˜1.7, since the leaf conductance is a function of both stomatal and the boundary layer conductance, the overall conductance will increase resulting in significantly higher levels of transpiration as the pressure drops. The conductance of gases is also regulated by stomatal aperture in an inverse relationship. The higher CO2 concentration inside the leaf air space during low pressure treatments may result in higher CO2 assimilation and partial stomata closure, resulting in a decrease in transpiration rate. The results of this analysis offer guidelines for experiments in pressure and high CO2 environments to establish ideal conditions for minimizing transpiration and maximizing the plant biomass yield in BLSS.

Gohil, Hemant L.; Correll, Melanie J.; Sinclair, Thomas

2011-01-01

13

Plant Transpiration and its Sensitivity to Increasing Carbon Dioxide Concentration at Leaf, Canopy and Regional Scales  

NASA Astrophysics Data System (ADS)

This thesis assembles simulation models for plant transpiration and uses these models to investigate the sensitivity of transpiration rates to the elevation of atmospheric CO_2 concentration at leaf, canopy and regional scales. The leaf transpiration model assembly (LTMA) simulates stomatal conductance, leaf net photosynthesis, leaf boundary layer conductance, mass and energy transfer, leaf energy balance. The stomatal conductance model and the leaf photosynthesis model are selected from two candidate stomatal models and four candidate biochemical photosynthesis models, based on the comparison of the model results with literature-surveyed observations. Integration of the LTMA for all the leaves within a plant canopy, with the modeled canopy structure, wind speed profile, radiation distribution, and soil surface fluxes, produces a canopy evapotranspiration model assembly (CEMA). Coupling the CEMA with an atmospheric boundary layer model, a larger model assembly (REMA) for simulating the evapotranspiration from a region covered with a homogeneous canopy is obtained. From the outputs of the LTMA, it is found that in response to a doubling of atmospheric CO_2 concentration the modeled leaf transpiration rate will be reduced by around -23.0% for C _3 plants and -26.6% for C4 plants. The simulated reduction in stomatal conductance resulting from the CO_2 doubling is 37.0% for C_3 plants and 37.7% for C_4 plants. The difference of the responses of stomatal conductance and leaf transpiration to CO_2 changes is found to be the results of the leaf boundary layer damping effect and the leaf temperature feedback effect. The CO_2 sensitivity of canopy evapotranspiration is found to be smaller still than that of leaf transpiration: the corresponding percentage changes with a CO_2 doubling are -15.7% and -16.1% respectively for C_3 and C_4 canopies. The cause is found to be the extension of the air within the canopy to the leaf boundary layers. The temperature feedback and the water vapor feedback mechanisms between the atmospheric boundary layer and the land surface fluxes produce the result that the percent change with a CO_2 doubling for regional evapotranspiration is -8.7% for C_3 plants and -13.0% for C_4 plants. Implications of the results of the models have been discussed.

Zhan, Xiwu

1995-01-01

14

A microfluidic pump/valve inspired by xylem embolism and transpiration in plants.  

PubMed

In plants, transpiration draws the water upward from the roots to the leaves. However, this flow can be blocked by air bubbles in the xylem conduits, which is called xylem embolism. In this research, we present the design of a biomimetic microfluidic pump/valve based on water transpiration and xylem embolism. This micropump/valve is mainly composed of three parts: the first is a silicon sheet with an array of slit-like micropores to mimic the stomata in a plant leaf; the second is a piece of agarose gel to mimic the mesophyll cells in the sub-cavities of a stoma; the third is a micro-heater which is used to mimic the xylem embolism and its self-repairing. The solution in the microchannels of a microfluidic chip can be driven by the biomimetic "leaf" composed of the silicon sheet and the agarose gel. The halting and flowing of the solution is controlled by the micro-heater. Results have shown that a steady flow rate of 1.12 µl/min can be obtained by using this micropump/valve. The time interval between the turning on/off of the micro-heater and the halt (or flow) of the fluid is only 2?3 s. This micropump/valve can be used as a "plug and play" fluid-driven unit. It has the potential to be used in many application fields. PMID:23209709

Jingmin, Li; Chong, Liu; Zheng, Xu; Kaiping, Zhang; Xue, Ke; Liding, Wang

2012-01-01

15

FPGA-based Fused Smart Sensor for Real-Time Plant-Transpiration Dynamic Estimation  

PubMed Central

Plant transpiration is considered one of the most important physiological functions because it constitutes the plants evolving adaptation to exchange moisture with a dry atmosphere which can dehydrate or eventually kill the plant. Due to the importance of transpiration, accurate measurement methods are required; therefore, a smart sensor that fuses five primary sensors is proposed which can measure air temperature, leaf temperature, air relative humidity, plant out relative humidity and ambient light. A field programmable gate array based unit is used to perform signal processing algorithms as average decimation and infinite impulse response filters to the primary sensor readings in order to reduce the signal noise and improve its quality. Once the primary sensor readings are filtered, transpiration dynamics such as: transpiration, stomatal conductance, leaf-air-temperature-difference and vapor pressure deficit are calculated in real time by the smart sensor. This permits the user to observe different primary and calculated measurements at the same time and the relationship between these which is very useful in precision agriculture in the detection of abnormal conditions. Finally, transpiration related stress conditions can be detected in real time because of the use of online processing and embedded communications capabilities.

Millan-Almaraz, Jesus Roberto; de Jesus Romero-Troncoso, Rene; Guevara-Gonzalez, Ramon Gerardo; Contreras-Medina, Luis Miguel; Carrillo-Serrano, Roberto Valentin; Osornio-Rios, Roque Alfredo; Duarte-Galvan, Carlos; Rios-Alcaraz, Miguel Angel; Torres-Pacheco, Irineo

2010-01-01

16

[Photosynthetic rate, transpiration rate, and water use efficiency of cotton canopy in oasis edge of Linze].  

PubMed

The measurement system of Li-8100 carbon flux and the modified assimilation chamber were used to study the photosynthetic characteristics of cotton (Gossypium hirsutum L.) canopy in the oasis edge region in middle reach of Heihe River Basin, mid Hexi Corridor of Gansu. At the experimental site, soil respiration and evaporation rates were significantly higher in late June than in early August, and the diurnal variation of canopy photosynthetic rate showed single-peak type. The photosynthetic rate was significantly higher (P < 0.01) in late June than in early August, with the daily average value being (43.11 +/- 1.26) micromol CO2 x m(-2) x s(-1) and (24.53 +/- 0.60) micromol CO2 x m(-2) x s(-1), respectively. The diurnal variation of canopy transpiration rate also presented single-peak type, with the daily average value in late June and early August being (3.10 +/- 0.34) mmol H2O x m(-2) x s(-1) and (1.60 +/- 0.26) mmol H2O x m(-2) x s(-1), respectively, and differed significantly (P < 0.01). The daily average value of canopy water use efficiency in late June and early August was (15.67 +/- 1.77) mmol CO2 x mol(-1) H2O and (23.08 +/- 5.54) mmol CO2 x mol(-1) H2O, respectively, but the difference was not significant (P > 0.05). Both in late June and in early August, the canopy photosynthetic rate was positively correlated with air temperature, PAR, and soil moisture content, suggesting that there was no midday depression of photosynthesis in the two periods. In August, the canopy photosynthetic rate and transpiration rate decreased significantly, because of the lower soil moisture content and leaf senescence, but the canopy water use efficiency had no significant decrease. PMID:20873616

Xie, Ting-Ting; Su, Pei-Xi; Gao, Song

2010-06-01

17

Transpiration estimation of banana ( Musa sp.) plants with the thermal dissipation method  

Microsoft Academic Search

The banana (Musa sp.) plant is one of the largest monocotyledoneous terrestrial herbaceous plants in the world. The measurement of transpiration\\u000a (Tr) for a whole banana plant is always difficult to perform due to its size. However, the sap flow (SF) of the plant has\\u000a been successfully measured by using the thermal dissipation probe (TDP) or ‘Granier’ method in the

Hai-Jun Liu; Shabtai Cohen; Josef Tanny; Jorge Hugo Lemcoff; Guanhua Huang

2008-01-01

18

Interannual environmental-soil thawing rate variation and its control on transpiration from Larix cajanderi, Central Yakutia, Eastern Siberia  

Microsoft Academic Search

Sapflow measurements were carried out in a larch forest in eastern Siberia, an area of wide permafrost distribution. Canopy transpiration and canopy conductance were scaled up from these values. The objective was to analyze the relationship between environmental variables, mainly vapour pressure deficit (D), soil moisture and soil thawing rate with canopy transpiration and canopy conductance. Maximum sapflow rate was

M. L. Lopez C; H. Saito; Y. Kobayashi; T. Shirota; G. Iwahana; T. C. Maximov; M. Fukuda

2007-01-01

19

Relative Importance of Reradiation, Convection, and Transpiration in Heat Transfer from Plants  

PubMed Central

For a plant of average spectral properties and average diffusion resistance (2 sec/cm), diurnal variations in the energy dissipated by reradiation, convection, and transpiration have been explicitly calculated and plotted for certain environmental conditions as measured at St. Paul, Minnesota. These conditions represent the environments of characteristic types of days and of characteristic types of leaves. In all situations reradiation is overwhelmingly the dominant mode of heat transfer. A new method for the calculation of Bowen's ratio is also presented which gives results in very good agreement with older procedures. For certain individual leaves the energy dissipated by convection is found to be greater than that dissipated by transpiration. For a crop as a whole, however, transpiration is found to be by far the most important.

Idso, Sherwood B.; Baker, Donald G.

1967-01-01

20

Deuterium excess as a proxy for continental moisture recycling and plant transpiration  

NASA Astrophysics Data System (ADS)

Studying the evaporation process and its link to the atmospheric circulation is central for a better understanding of the feedbacks between the surface water components and the atmosphere. In this study, we use 5 months of deuterium excess (d) measurements at the hourly to daily timescale from a cavity ring-down laser spectrometer to characterise the evaporation source of low-level continental water vapour at the long-term hydrometeorological monitoring site Rietholzbach in northeastern Switzerland. To reconstruct the phase change history of the air masses in which we measure the d signature and to diagnose its area of surface evaporation we apply a Lagrangian moisture source diagnostic. With the help of a correlation analysis we investigate the strength of the relation between d measurements and the moisture source conditions. Temporal episodes with a duration of a few days of strong anticorrelation between d and relative humidity as well as temperature are identified. The role of plant transpiration, the large-scale advection of remotely evaporated moisture, the local boundary layer dynamics at the measurement site and recent precipitation at the site of evaporation are discussed as reasons for the existence of these modes of strong anticorrelation between d and moisture source conditions. We show that the importance of continental moisture recycling and the contribution of plant transpiration to the continental evaporation flux may be deduced from the d-relative humidity relation at the seasonal timescale as well as for individual events. The methodology and uncertainties associated with these estimates of the transpiration fraction of evapotranspiration are presented and the proposed novel framework is applied to individual events from our data set. Over the whole analysis period (August to December 2011) a transpiration fraction of the evapotranspiration flux over the continental part of the moisture source region of 62% is found albeit with a large event-to-event variability (0% to 89%) for continental Europe. During days of strong local moisture recycling a higher overall transpiration fraction of 76% (varying between 65% and 86%) is found. These estimates are affected by uncertainties in the assumptions involved in our method as well as by parameter uncertainties. An average uncertainty of 11% results from the strong dependency of the transpiration estimates on the choice of the non-equilibrium fractionation factor. Other uncertainty sources like the influence of boundary layer dynamics are probably large but more difficult to quantify. Nevertheless, such Lagrangian estimates of the transpiration part of continental evaporation could potentially be useful for the verification of model estimates of this important land-atmosphere coupling parameter.

Aemisegger, F.; Pfahl, S.; Sodemann, H.; Lehner, I.; Seneviratne, S. I.; Wernli, H.

2014-04-01

21

Physiological action of smog on plants. I. Initial growth and transpiration studies  

Microsoft Academic Search

The effect of synthetic smog (1-n-hexene plus ozone) on growth and transpiration of tomato plants (Lycopersicon esculentum) and on elongation of etiolated pea sections (Pisum sativum) has been studied. Use has been made of hidden damage (growth decrease in the absence of visible injury) to measure the effect of light, sucrose spray, ..beta..-naphthoxyacetic acid, and water supply on smog injury.

H. G. Koritz; F. W. Went

1953-01-01

22

Factors controlling transpiration of mature field-grown tea and its relationship with yield  

Microsoft Academic Search

The objective of this experiment was to determine the factors influencing the transpiration rates of mature, clonal tea (Camellia sinensis L.) and estimate its transpiration efficiency. The heat pulse technique was used to measure transpiration rates of tea plants growing in the field as part of extensive canopies at Talawakelle, Sri Lanka during the period between 1 January and 19

A Anandacoomaraswamy; W. A. J. M De Costa; H. W Shyamalie; G. S Campbell

2000-01-01

23

The stable isotope composition of transpired water and the rate of change in leaf water enrichment in response to variable environments  

NASA Astrophysics Data System (ADS)

Previous research has shown that during daylight hours the isotope composition of leaf water is generally well approximated by steady-state leaf water isotope enrichment models. However, there is little direct confirmation of isotopic steady state (ISS) transpiration. Here we use a novel method to evaluate the frequency (or infrequency) of ISS transpiration and the rate of change in leaf water enrichment when leaves are exposed to a variable environment. Specifically, our study had three goals. First, we wanted to develop a new method to measure the isotope fluxes of transpiration that relies on isotope ratio infrared spectroscopy (IRIS) and highlight how an IRIS instrument can be coupled to plant gas exchange systems. In doing so, we also developed a method for controlling the absolute humidity entering the gas exchange cuvettes across a wide range of concentrations (approximately 4000 ppmv to 22000 ppmv) without changing the isotope composition of water vapour entering the cuvette. Second, we quantified variation in the isotope composition of transpired water vapor and the rate of change in leaf water enrichment that can occur as a result of changes in relative humidity, leaf surface conductance to water vapour, leaf temperature and the isotope composition of atmospheric water vapor. Third, we examine the differences between steady state and non-steady state model predictions of leaf water enrichment at the site of evaporation. In our measurements the isotopic compositions of transpired water were neither stable nor equal to source water until leaves had been maintained at physiological steady state for at least 40 minutes. Additionally when transpiration was not at ISS, the steady state model predictions of leaf water enrichment at the site of evaporation exceeded non steady-state model predictions by up to 8 per mil. Further, the rate of change in leaf water enrichment was highly sensitive to variation in leaf water content. Our results suggest that a variable environment is likely to preclude isotopic steady-state transpiration and that this effect would be exacerbated by lengthy leaf water turnover times.

Simonin, K. A.; Roddy, A. B.; Link, P.; Apodaca, R. L.; Tu, K. P.; Hu, J.; Dawson, T. E.; Barbour, M.

2012-12-01

24

Partitioning of Evapotranspiration Into Soil Evaporation and Plant Transpiration Using Isotopes of Water in Controlled Conditions  

NASA Astrophysics Data System (ADS)

Rainfall recycling by evapotranspiration from continental surfaces is certainly the most unknown component of the global water cycle. This is due to the large variability of rainfall as well as the heterogeneity of these continental surfaces, both in time and space. Traditional measuring methods such as sap flow, micro lysimeter, water and energy balance estimation (Bowen ratio, eddy correlation) have been used since the 70s for a monitoring of real evapotranspiration fluxes over crops and others plant covers. A complementary method consists in using isotopic biogeochemistry. When making specific hypothesis, it is possible to identify and quantify the different sources of the atmospheric water vapour (vegetation and soil at different scales). Analysis of the heavy stable isotopic ratios of water in both liquid and vapour phases: 18O and 2H can allow determining the history of the water in the soil since the last rainfall event (infiltration, re-evaporation) or the root extraction depths. Field campaigns measurements (plants and soils), interpreted using the Keeling Plot method allowed some progress in the partition between evaporation and transpiration understanding. But the experimental design is not sufficient to mechanistically describe the water processes involved. The study of all the interactions is difficult due to the large number of controlling variables describing climate, vegetation and soil characteristics. A monolith experiment (including soil and growing plant) was carried out in a reactor called RUBIC (Reactor Used for Continental Isotopic Biogeochemistry, Bariac et al., Geochim. Cosmochim. Acta., 1991). Controlled conditions allowed a monitoring and regulation of climatic parameters (net radiation, air temperature, vapour pressure deficit, CO2 partial pressure, and wind speed). It was also necessary to fix soil (structure, texture, and water content) and vegetation (specie and seeding density) parameters. The collected data allow us to improve our understanding of the partition of evapotranspiration into soil evaporation and plant transpiration and to assess the hypothesis (often made in isotopic biochemistry) of a stationary state reached in the two reservoirs (soil and plant). These data also allow the evaluation of the hypothesis included in a transfer module of heavy stable isotopes of water within the bare soil and the plant (Braud et al., Journ. of Hydrol., 2005). The latter is coupled to a SVAT model (Soil-Plant-Atmosphere Transfer) called SiSPAT (Simple Soil Plant Atmosphere Transfer model, Braud et al., Journ. of Hydrol., 1995) and was extended to take into account isotopes transfer within the vegetation (root extraction and transpiration). The experimental design of RUBIC as well as the first modelling results will be presented.

Rothfuss, Y.; Bariac, T.; Braud, I.; Biron, P.; Richard, P.; Canale, L.; Durand, J.; Gaudet, J.

2007-12-01

25

The porous media model for the hydraulic system of a conifer tree: Linking sap flux data to transpiration rate  

Microsoft Academic Search

Linking sap flow in tree boles to plant transpiration continues to be a fundamental and practical research problem in physiological ecology and forest hydrology. Many models have been proposed to describe water movement within trees with varying degrees of success. The prevailing resistance–capacitance (RC)-circuit models have the advantage of being easy to implement. However, RC models are ordinary differential equation

Yao-Li Chuang; Ram Oren; Andrea L. Bertozzi; Nathan Phillips; Gabriel G. Katul

2006-01-01

26

The Arabidopsis outward K+ channel GORK is involved in regulation of stomatal movements and plant transpiration  

PubMed Central

Microscopic pores present in the epidermis of plant aerial organs, called stomata, allow gas exchanges between the inner photosynthetic tissue and the atmosphere. Regulation of stomatal aperture, preventing excess transpirational vapor loss, relies on turgor changes of two highly differentiated epidermal cells surrounding the pore, the guard cells. Increased guard cell turgor due to increased solute accumulation results in stomatal opening, whereas decreased guard cell turgor due to decreased solute accumulation results in stomatal closing. Here we provide direct evidence, based on reverse genetics approaches, that the Arabidopsis GORK Shaker gene encodes the major voltage-gated outwardly rectifying K+ channel of the guard cell membrane. Expression of GORK dominant negative mutant polypeptides in transgenic Arabidopsis was found to strongly reduce outwardly rectifying K+ channel activity in the guard cell membrane, and disruption of the GORK gene (T-DNA insertion knockout mutant) fully suppressed this activity. Bioassays on epidermal peels revealed that disruption of GORK activity resulted in impaired stomatal closure in response to darkness or the stress hormone azobenzenearsonate. Transpiration measurements on excised rosettes and intact plants (grown in hydroponic conditions or submitted to water stress) revealed that absence of GORK activity resulted in increased water consumption. The whole set of data indicates that GORK is likely to play a crucial role in adaptation to drought in fluctuating environments.

Hosy, Eric; Vavasseur, Alain; Mouline, Karine; Dreyer, Ingo; Gaymard, Frederic; Poree, Fabien; Boucherez, Jossia; Lebaudy, Anne; Bouchez, David; Very, Anne-Alienor; Simonneau, Thierry; Thibaud, Jean-Baptiste; Sentenac, Herve

2003-01-01

27

Validation of canopy transpiration in a mixed-species foothill eucalypt forest using a soil-plant-atmosphere model  

NASA Astrophysics Data System (ADS)

Studies of the hydrology of native eucalypt forests in south-east Australia have focused on ash-type eucalypt species that are largely confined to Victoria and Tasmania. Mixed species foothill forests comprise the largest proportion of the forest estate in south-east Australia, yet are poorly known hydrologically. The ability to predict forest transpiration, both with reasonable accuracy and in response to changes in the environment, is essential for catchment management. A soil-plant-atmosphere model (SPA) was validated for 222 days in a mature, mixed species forest of north-east Victoria using measurements of overstorey transpiration (Eucalyptus radiata and Eucalyptus goniocalyx) and site-specific climate and vegetation parameters. There was a stronger relationship between average daily transpiration (0.71 mm day-1) and daily minimum relative humidity (R2 = 0.71), than between average daily transpiration and daily maximum temperature (R2 = 0.65). Stand water use could be predicted best from vapour pressure deficit (R2 = 0.89). SPA successfully predicted stand transpiration (R2 = 0.85) over a range of soil water and climatic conditions. A sensitivity analysis suggests that among the various required inputs, leaf area index (LAI) was the most important, and accurate estimates of LAI could significantly improve estimation of stand transpiration.

Gharun, Mana; Turnbull, Tarryn L.; Adams, Mark A.

2013-06-01

28

TRANSPIRATION EFFECT ON THE UPTAKE AND DISTRIBUTION OF BROMACIL, NITROBENZENE, AND PHENOL IN SOYBEAN PLANTS (JOURNAL VERSION)  

EPA Science Inventory

The influence of transpiration rate on the uptake and translocation of two industrial waste compounds, phenol and nitrobenzene, and one pesticide, 5-bromo-3-sec-butyl-6-methyluracil (bromacil), was examined. Carbon-14 moieties of each compound were provided separately in hydropon...

29

On the enrichment of H 2 18 O in the leaves of transpiring plants  

Microsoft Academic Search

Summary The vapor pressure difference between H218O and H216O is the reason for the accumulation of the heavy molecule in transpiring leaves. Since photosynthesis on land is the main source of atmospheric oxygen, this mechanism is important for the remarkable enrichment of18O in atmospheric O2 (Dole effect). Using a simple box model for transpiring leaves a quantitative understanding of the

G. Dongmann; H. W. Nuernberg; H. Foerstel; K. Wagener

1974-01-01

30

Effects of air current speed, light intensity and co2 concentration on photosynthesis and transpiration of plant leaves  

NASA Astrophysics Data System (ADS)

To obtain basic data for adequate air circulation to promote gas exchange and growth of plants in closed plant culture modules in bioregenerative life support systems in space, the effects of air current speeds less than 0.8 m s-1 on transpiration (Tr) and net photosynthetic rates (Pn) of sweetpotato and barley leaves were determined using a leaf chamber method under different photosynthetic photon flux densities (PPFDs) and CO_2 concentrations. The air current speed inside the leaf chamber was controlled by controlling the input voltages for an air circulation fan. The leaf surface boundary layer resistance was determined by the evaporation rate of wet paper and the water vapor pressure difference between the paper and surrounding air in the leaf chamber. The Tr and Pn of leaves rapidly increased as the air current speed increased from 0.01 to 0.1 m s-1 and gradually increased from 0.1 to 0.8 m s-1. These changes are correspondent to the change of the leaf surface boundary layer resistance. The depression of Tr by low air current speeds was greater than that of Pn. Tr and Pn decreased by 0.5 and 0.7 times, respectively, as the air current speed decreased from 0.8 to 0.01 m s-1. The depressions of Tr and Pn by low air current speeds were most notable at PPFDs of 500 and 250 ?mol m-2 s-1, respectively. The air current speeds affected Tr and Pn at a CO_2 concentration of 700 ?mol mol-1 as well as at 400 ?mol mol-1. The results confirmed the importance of controlling air movement for enhancing Tr and Pn under the relatively high PPFD and elevated CO_2 levels likely in plant culture systems in space.

Kitaya, Y.; Tsuruyama, J.; Shibuya, T.; Kiyota, M.

31

Measuring forest evaporation and transpiration rates with fibre optic temperature sensing  

NASA Astrophysics Data System (ADS)

Evaporation is one of the most important fluxes of the water balance as it accounts for 55-80% of the precipitation. However, measuring evaporation remains difficult and requires sophisticated and expensive equipment. In this paper we propose a new measuring technique based on the existing Bowen ratio method. With a fibre optic cable a temperature and a vapour pressure profile can be measured by the principle of a psychrometer and combined with the net radiation (and ground heat flux) the latent heat can be calculated. Compared to the conventional Bowen ratio method the advantages of this method is that the profiles are measured with a single sensor (resulting in a smaller error), and contain more measuring points in the vertical and therefore give more insight into the developed profiles. The method also allows to measure through a forest canopy. Applying the Bowen ratio above and below the canopy an estimation of the transpiration flux can be obtained. As a first test, we compared in a pine forest in The Netherlands (Loobos) the transpiration estimates of the fibre optic cable with sapflow measurements, and eddy covariance measurements above and below the canopy. The experiment was carried out on three days in September 2013 and the preliminary results show reasonable correlation with the eddy covariance estimates, but not with the sapflow observations. To explain the differences further investigation is needed and a longer measuring period is required.

Coenders-Gerrits, Miriam; Luxemburg, Wim; Hessels, Tim; de Kloe, Arjan; Elbers, Jan

2014-05-01

32

Transpiration rates and canopy conductance of Pinus radiata growing with different pasture understories in agroforestry systems.  

PubMed

We measured tree transpiration and canopy conductance in Pinus radiata D. Don at two low rainfall sites of differing soil fertility in Canterbury, New Zealand. At the more fertile Lincoln site, we also assessed the effects of two common pasture grasses on tree transpiration and canopy conductance. At the less fertile Eyrewell Forest site, the effect of no understory, and the effects of irrigation in combination with mixtures of grass or legume species were determined. Tree xylem sap flux (F(d)') was measured by the heat pulse method. Total canopy conductance to diffusion of water vapor (G(t)) was calculated by inverting a simplified Penman-Monteith model. The different treatment effects were modeled by the simple decaying exponential relationship G(t) = G(tmax)e((-bD)), where D = air saturation deficit. At the Lincoln site, trees with an understory of cocksfoot had lower F(d)' and G(tmax) than trees with an understory of ryegrass, although the sensitivity of G(t) to increasing D (i.e., the value of b) did not differ between treatments. At the Eyrewell site, irrigation only increased F(d)' in the absence of an understory, whereas the presence of understory vegetation, or lack of irrigation, or both, significantly reduced G(tmax) and increased b. We conclude that the selection of understory species is critical in designing successful agroforestry systems for low rainfall areas. PMID:12651344

Miller, Blair J.; Clinton, Peter W.; Buchan, Graeme D.; Robson, A. Bruce

1998-01-01

33

Rates of nocturnal transpiration in two evergreen temperate woodland species with differing water-use strategies.  

PubMed

Nocturnal fluxes may be a significant factor in the annual water budget of forested ecosystems. Here, we assessed sap flow in two co-occurring evergreen species (Eucalyptus parramattensis and Angophora bakeri) in a temperate woodland for 2 years in order to quantify the magnitude of seasonal nocturnal sap flow (E(n)) under different environmental conditions. The two species showed different diurnal water relations, demonstrated by different diurnal curves of stomatal conductance, sap flow and leaf water potential. The relative influence of several microclimatic variables, including wind speed (U), vapour pressure deficit (D), the product of U and D (UD) and soil moisture content, were quantified. D exerted the strongest influence on E(n) (r² = 0.59-0.86), soil moisture content influenced E(n) when D was constant, but U and UD did not generally influence E(n). In both species, cuticular conductance (G(c)) was a small proportion of total leaf conductance (G(s)) and was not a major pathway for E(n). We found that E(n) was primarily a function of transpiration from the canopy rather than refilling of stem storage, with canopy transpiration accounting for 50-70% of nocturnal flows. Mean E(n) was 6-8% of the 24-h flux across seasons (spring, summer and winter), but was up to 19% of the 24-h flux on some days in both species. Despite different daytime strategies in water use of the two species, both species demonstrated low night-time water loss, suggesting similar controls on water loss at night. In order to account for the impact of E(n) on pre-dawn leaf water potential arising from the influence of disequilibria between root zone and leaf water potential, we also developed a simple model to more accurately predict soil water potential (?(s)). PMID:20566582

Zeppel, Melanie; Tissue, David; Taylor, Daniel; Macinnis-Ng, Catriona; Eamus, Derek

2010-08-01

34

Estimation of plant transpiration from meteorological data under conditions of sufficient soil moisture  

NASA Astrophysics Data System (ADS)

The transpiration of forest growth during the growing season when sufficient soil moisture is available is estimated on the basis of the requirement of water for cooling trees. Tree growth is regarded as a cooler with water as a coolant (evaporative latent heat). Trees are simultaneously warmed up by incident solar radiation and cooled down by the ambient air and by the evaporation of water from the leaf. These parallel, mutually competing processes are described in their simplest form and provide the algorithm for the calculation of the cooling-water requirement. The calculation uses hourly values of air temperature and of global-radiation totals. Properties of the forest growth are expressed in terms of two phenomenological constants — effective absorptivity and effective thickness of leaves. Both are obtained by calibration. The applicability of the proposed calculation was subjected to experimental verification during the course of the growing seasons for 1985-1989 in the mountain watershed LIZ, situated in the National Park S?umava in the southern part of the Czech Republic. The error in determining evapotranspiration/transpiration is about 5% of the precipitation over the growing season.

Pražák, J.; Šír, M.; Tesar?, M.

1994-11-01

35

Sap flow measurements to determine the transpiration of facade greenings  

NASA Astrophysics Data System (ADS)

Facade greening is expected to make a major contribution to the mitigation of the urban heat-island effect through transpiration cooling, thermal insulation and shading of vertical built structures. However, no studies are available on water demand and the transpiration of urban vertical green. Such knowledge is needed as the plants must be sufficiently watered, otherwise the posited positive effects of vertical green can turn into disadvantages when compared to a white wall. Within the framework of the German Research Group DFG FOR 1736 "Urban Climate and Heat Stress" this study aims to test the practicability of the sap flow technique for transpiration measurements of climbing plants and to obtain potential transpiration rates for the most commonly used species. Using sap flow measurements we determined the transpiration of Fallopia baldschuanica, Parthenocissus tricuspidata and Hedera helix in pot experiments (about 1 m high) during the hot summer period from August 17th to August 30th 2012 under indoor conditions. Sap flow measurements corresponded well to simultaneous weight measurement on a daily base (factor 1.19). Fallopia baldschuanica has the highest daily transpiration rate based on leaf area (1.6 mm d-1) and per base area (5.0 mm d-1). Parthenocissus tricuspidata and Hedera helix show transpiration rates of 3.5 and 0.4 mm d-1 (per base area). Through water shortage, transpiration strongly decreased and leaf temperature measured by infrared thermography increased by 1 K compared to a well watered plant. We transferred the technique to outdoor conditions and will present first results for facade greenings in the inner-city of Berlin for the hottest period in summer 2013.

Hölscher, Marie-Therese; Nehls, Thomas; Wessolek, Gerd

2014-05-01

36

Impacts of forest thinning and climate change on transpiration and runoff rates in Sierra Nevada mixed-conifer headwater catchments  

NASA Astrophysics Data System (ADS)

Using a spatially explicit hydro-ecological model, impacts from forest thinning and climate change on snowpack, evapotranspiration (ET) rates, soil moisture storage, and runoff were investigated in Sierra Nevada headwater catchments spanning elevations of 1,500 to 2,000-m. Along this elevation gradient, precipitation changes from rain-dominated to snow-dominated, so precipitation phase will be strongly impacted by increases in temperature. Mixed-conifer forests in the Sierra Nevada near the 2,000-m elevation band also transpire at a high rate relative to upper elevation forests that are more restricted by colder winter temperatures and lower elevation forests that are more restricted by lower summer soil moisture, increasing the potential of reduced transpiration with vegetation thinning. Forest treatment and climate change scenarios were modeled using the Regional Hydro-Ecological Simulation System (RHESSys), calibrated with two years of snow, soil moisture, and streamflow observations. Simulations of forest thinning at moderate (66% of current vegetation density) and restoration (33% density) levels were combined with precipitation changes up to 20% and temperature increases up to 6?C for projecting impacts on ET and runoff rates. Model results indicated that moderate thinning alone could increase runoff by 3%, but additional temperature increases of 2-4?C could increase runoff rates another 6% - similar to a restoration level thinning. Modifying temperature and precipitation separately showed that the two methods of climate forcing both led to fluctuations in soil moisture, caused by changes in precipitation phase (snow/rain) and final day of snowpack melt. The snowmelt timing affected runoff rates by causing changes in the spring soil moisture recession, and showed that it may be one of the critical processes that affects annual runoff rates, not just runoff timing. Simulations of precipitation and temperature changes together showed that precipitation would be the main driver of runoff change in the current vegetation and restoration thinning scenarios, while both precipitation and temperature would drive runoff rates in a moderate thinning scenario. Ultimately, the forest thinning scenarios directly led to decreases in evapotranspiration and increases in runoff as expected, with a warmer climate potentially enhancing these changes.

Saksa, P. C.; Ray, R. L.; Bales, R. C.; Conklin, M. H.

2013-12-01

37

Development of a simplified plant stomatal resistance model and its validation for potentially transpiring and water-stressed water hyacinths  

NASA Astrophysics Data System (ADS)

A simple model of upper-canopy plant stomatal resistance ( ruC) was developed which requires but four input parameters: canopy aerodynamic resistance, upper-canopy foliage temperature, and air vapor pressure deficit and temperature. The model was tested against upper-canopy sunlit leaf stomatal resistance ( r l) measurements of both potentially and non-potentially transpiring water hyacinth plants over the upper-canopy-intercepted net radiation range of 300-450 W m -2 and over a 10-fold range of r l. In all instances, and indicative of the model's good performance, the ratio of r uC/r l consistently averaged about 1.25, due to partial self-shading of the upper-canopy foliage. The significance of this finding to air pollution studies arises from the facts that (1) contemporary knowledge of a plant canopy's leaf area index would allow the transformation of ruC to rC, the total canopy diffusive resistance, and (2) the proper accounting for different trace gas diffusivities would allow the transformation of rc for water vapor to the variety of rC values required to infer the gaseous deposition of important pollutant gas species at vegetated surfaces.

Idso, Sherwood B.

38

The effects of CO2 on growth and transpiration of radish (Raphanus sativus) in hypobaria  

NASA Astrophysics Data System (ADS)

Plants grown on long-term space missions will likely be grown in low pressure environments (i.e., hypobaria). However, in hypobaria the transpiration rates of plants can increase and may result in wilting if the water is not readily replaced. It is possible to reduce transpiration by increasing the partial pressure of CO2 (pCO2), but the effects of pCO2 at high levels (>120 Pa) on the growth and transpiration of plants in hypobaria are not known. Therefore, the effects of pCO2 on the growth and transpiration of radish (Raphanus sativus var. Cherry Bomb II) in hypobaria were studied. The fresh weight (FW), leaf area, dry weight (DW), CO2 assimilation rates (CA), dark respiration rates (DR), and transpiration rates from 26 day-old radish plants that were grown for an additional seven days at different total pressures (33, 66 or 101 kPa) and pCO2 (40 Pa, 100 Pa and 180 Pa) were measured. In general, the dry weight of plants increased with CO2 enrichment and with lower total pressure. In limiting pCO2 (40 Pa) conditions, the transpiration for plants grown at 33 kPa was approximately twice that of controls (101 kPa total pressure with 40 Pa pCO2). Increasing the pCO2 from 40 Pa to 180 Pa reduced the transpiration rates for plants grown in hypobaria and in standard atmospheric pressures. However, for plants grown in hypobaria and high pCO2 (180 Pa) leaf damage was evident. Radish growth can be enhanced and transpiration reduced in hypobaria by enriching the gas phase with CO2 although at high levels leaf damage may occur.

Gohil, H. L.; Bucklin, R. A.; Correll, M. J.

2010-04-01

39

Estimation of whole-plant transpiration of bananas using sap flow measurements.  

PubMed

Banana, one of the largest rhizomatous herbs in the world, is the fourth most important global food crop. It has a high water requirement, but the whole-plant water use in the field has not been determined satisfactorily. In this study, whole-plant water use in potted and field-grown banana plants (Musa 'Cavendish' cv. Williams) was successfully determined using a xylem sap flow method. This was achieved using Granier sensor probes implanted into the central cylinder of the banana corm. The whole-plant water use in field-grown bananas was 9-10 l plant(-1) d(-1). The values of daily total sap flow in potted plants correlated closely with gravimetric measurements (r(2)=0.92) and with changes in soil water status (r(2)=0.77). In well-watered, mature, field-grown plants, hourly sap flow also closely correlated with changes in solar radiation, vapour pressure deficit and evapotranspiration. The study indicates that sap flow measurement is a sensitive and accurate method for determining whole-plant water use in bananas under potted as well as field conditions. PMID:12147727

Lu, Ping; Woo, Kam-Chau; Liu, Zhu-Tian

2002-08-01

40

Control of transpiration by radiation.  

PubMed

The terrestrial hydrological cycle is strongly influenced by transpiration--water loss through the stomatal pores of leaves. In this report we present studies showing that the energy content of radiation absorbed by the leaf influences stomatal control of transpiration. This observation is at odds with current concepts of how stomata sense and control transpiration, and we suggest an alternative model. Specifically, we argue that the steady-state water potential of the epidermis in the intact leaf is controlled by the difference between the radiation-controlled rate of water vapor production in the leaf interior and the rate of transpiration. Any difference between these two potentially large fluxes is made up by evaporation from (or condensation on) the epidermis, causing its water potential to pivot around this balance point. Previous work established that stomata in isolated epidermal strips respond by opening with increasing (and closing with decreasing) water potential. Thus, stomatal conductance and transpiration rate should increase when there is condensation on (and decrease when there is evaporation from) the epidermis, thus tending to maintain homeostasis of epidermal water potential. We use a model to show that such a mechanism would have control properties similar to those observed with leaves. This hypothesis provides a plausible explanation for the regulation of leaf and canopy transpiration by the radiation load and provides a unique framework for studies of the regulation of stomatal conductance by CO(2) and other factors. PMID:20624981

Pieruschka, Roland; Huber, Gregor; Berry, Joseph A

2010-07-27

41

The isotopic signature of transpiration in mixed conifer forest  

Microsoft Academic Search

Isotopic measurements of water vapor in forest air provide insights into ecosystem level responses to variability in surface hydrology. Studies of isotopic water balance of ecosystems should account for variation in the isotopic signature of transpired vapor in the non-steady state as well as isotopic differences in source water among dominant forest plants. Generally low rates of leaf gas exchange

D. G. Williams; B. Ewers; J. L. Angstmann; N. Guemouria; A. Chehbouni

2008-01-01

42

Where do roots take up water? Neutron radiography of water flow into the roots of transpiring plants growing in soil.  

PubMed

Where and how fast does water flow from soil into roots? The answer to this question requires direct and in situ measurement of local flow of water into roots of transpiring plants growing in soil. We used neutron radiography to trace the transport of deuterated water (D?O) in lupin (Lupinus albus) roots. Lupins were grown in aluminum containers (30 × 25 × 1 cm) filled with sandy soil. D?O was injected in different soil regions and its transport in soil and roots was monitored by neutron radiography. The transport of water into roots was then quantified using a convection-diffusion model of D?O transport into roots. The results showed that water uptake was not uniform along roots. Water uptake was higher in the upper soil layers than in the lower ones. Along an individual root, the radial flux was higher in the proximal segments than in the distal segments. In lupins, most of the water uptake occurred in lateral roots. The function of the taproot was to collect water from laterals and transport it to the shoot. This function is ensured by a low radial conductivity and a high axial conductivity. Lupin root architecture seems well designed to take up water from deep soil layers. PMID:23692148

Zarebanadkouki, Mohsen; Kim, Yangmin X; Carminati, Andrea

2013-09-01

43

Impact of photosynthesis and transpiration on nitrogen removal in constructed wetlands  

Microsoft Academic Search

To determine the impact of photosynthesis and transpiration on nitrogen removal in wetlands, an artificial wetland planted\\u000a with reeds was constructed to treat highly concentrated domestic wastewater. Under different meteorological and hydraulic\\u000a conditions, the daily changes of photosynthesis and transpiration of reeds, as well as nitrogen removal efficiency were measured.\\u000a It was found that net photosynthesis rate per unit leaf

Weiguo Luo; Shihe Wang; Juan Huang; Lu Yan; Jun Huang

2007-01-01

44

Transpiration cooled throat for hydrocarbon rocket engines  

NASA Technical Reports Server (NTRS)

The objective for the Transpiration Cooled Throat for Hydrocarbon Rocket Engines Program was to characterize the use of hydrocarbon fuels as transpiration coolants for rocket nozzle throats. The hydrocarbon fuels investigated in this program were RP-1 and methane. To adequately characterize the above transpiration coolants, a program was planned which would (1) predict engine system performance and life enhancements due to transpiration cooling of the throat region using analytical models, anchored with available data; (2) a versatile transpiration cooled subscale rocket thrust chamber was designed and fabricated; (3) the subscale thrust chamber was tested over a limited range of conditions, e.g., coolant type, chamber pressure, transpiration cooled length, and coolant flow rate; and (4) detailed data analyses were conducted to determine the relationship between the key performance and life enhancement variables.

May, Lee R.; Burkhardt, Wendel M.

1991-01-01

45

Environmental control of whole-plant transpiration, canopy conductance and estimates of the decoupling coefficient for large red maple trees  

Microsoft Academic Search

There is a strong need to extend whole-tree measurements of sap flow into broad-leaved forests where characteristics of stand structure, surface roughness, leaf dimension, and aerodynamic and canopy conductance may interact to partially decouple the canopy from the atmosphere. The implications of this partial decoupling to understanding the environmental control of canopy transpiration and to the modeling of forest water

Stan D Wullschleger; Kell B Wilson; Paul J Hanson

2000-01-01

46

Leaf senescence in rice due to magnesium deficiency mediated defect in transpiration rate before sugar accumulation and chlorosis.  

PubMed

Magnesium (Mg) is an essential macronutrient supporting various functions, including photosynthesis. However, the specific physiological responses to Mg deficiency remain elusive. In this study, 2-week-old rice seedlings (Oryza sativa. cv. Nipponbare) with three expanded leaves (L2-L4) were transferred to Mg-free nutrient solution for 8 days. In the absence of Mg, on day 8, L5 and L6 were completely developed, while L7 just emerged. We also studied several mineral deficiencies to identify specific responses to Mg deficiency. Each leaf was analyzed in terms of chlorophyll, starch, anthocyanin and carbohydrate metabolites, and only absence of Mg was found to cause irreversible senescence of L5. Resupply of Mg at various time points confirmed that the borderline of L5 death was between days 6 and 7 of Mg deficiency treatment. Decrease in chlorophyll concentration and starch accumulation occurred simultaneously in L5 and L6 blades on day 8. However, nutrient transport drastically decreased in L5 as early as day 6. These data suggest that the predominant response to Mg deficiency is a defect in transpiration flow. Furthermore, changes in myo-inositol and citrate concentrations were detected only in L5 when transpiration decreased, suggesting that they may constitute new biological markers of Mg deficiency. PMID:23176135

Kobayashi, Natsuko I; Saito, Takayuki; Iwata, Naoko; Ohmae, Yoshimi; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M

2013-08-01

47

Leaf senescence in rice due to magnesium deficiency-mediated defect in transpiration rate before sugar accumulation and chlorosis.  

PubMed

Magnesium (Mg) is an essential macronutrient supporting various functions, including photosynthesis. However, the specific physiological responses to Mg deficiency remain elusive. In this study, 2-week-old rice seedlings (Oryza sativa. cv. Nipponbare) with 3 expanded leaves (L2-L4) were transferred to Mg-free nutrient solution for 8 days. In the absence of Mg, on day 8, L5 and L6 were completely developed, while L7 just emerged. We also studied several mineral deficiencies to identify specific responses to Mg deficiency. Each leaf was analyzed in terms of chlorophyll, starch, anthocyanin, and carbohydrate metabolites, and only absence of Mg was found to cause irreversible senescence of L5. Resupply of Mg at various time points confirmed that the borderline of L5 death was between days 6 and 7 of Mg deficiency treatment. Decrease in chlorophyll concentration and starch accumulation occurred simultaneously in L5 and L6 blades on day 8. However, nutrient transport drastically decreased in L5 as early as day 6. These data suggest that the predominant response to Mg deficiency is a defect in transpiration flow. Furthermore, changes in myo-inositol and citrate concentrations were detected only in L5 when transpiration decreased, suggesting that they may constitute new biological markers of Mg deficiency. PMID:23106221

Kobayashi, Natsuko I; Saito, Takayuki; Iwata, Naoko; Ohmae, Yoshimi; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M

2012-10-26

48

The function of nocturnal transpiration  

NASA Astrophysics Data System (ADS)

Nocturnal transpiration is an important source of water loss, accounting for up to 25% of daytime transpiration in some species. Nocturnal water losses cannot be explained under the prevailing 'paradigm' of optimizing carbon gain while minimizing water loss because carbon fixation does not occur at night. Alternative explanations regarding the function and potential evolutionary advantage of nocturnal transpiration have been proposed, such as enhanced nutrient uptake and transport or delivery of O2 to parenchyma cells for respiration. However, recent evidence suggests that the role of nocturnal transpiration in supplementing the overall plant nutrient budget is relatively small, and the O2 hypothesis is difficult to test experimentally. Here, we propose that the main function of nocturnal transpiration (and water transport) is to prevent catastrophic xylem failure by restoring depleted stem 'capacitors' and enhancing early morning CO2 uptake, as stomata 'prepare' for daytime conditions. Nocturnal sap flux was highest in Eucalyptus grandis trees in the field following a heat wave (reaching 47C with VPDs > 8kPa in the daytime) generating maximal daytime water losses compared with cooler and lower VPD periods, indicating the importance of nocturnal stomatal conductance for stem refilling. Moreover, we observed that the time for stomata to respond to light early in the morning (dawn) across 25 different genotypes of E. camaldulensis in a glasshouse was shortest in those genotypes with highest nocturnal stomatal conductance, which was also correlated with higher daytime photosynthesis. This observation is consistent with previous observations that nocturnal stomatal conductance is partially controlled by the clock, which is utilised to anticipate daytime conditions. Data from the literature suggests that eucalypts respond similarly to other C3 species, suggesting that mechanisms regulating night-time transpiration may be universal.

Pfautsch, Sebastian; Resco de Dios, Víctor; Loik, Michael; Tissue, David

2014-05-01

49

Control of Leaf Expansion Rate of Droughted Maize Plants under Fluctuating Evaporative Demand (A Superposition of Hydraulic and Chemical Messages?).  

PubMed Central

We have analyzed the possibility that chemical signaling does not entirely account for the effect of water deficit on the maize (Zea mays L.) leaf elongation rate (LER) under high evaporative demand. We followed time courses of LER (0.2-h interval) and spatial distribution of elongation rate in leaves of either water-deficient or abscisic acid (ABA)-fed plants subjected to varying transpiration rates in the field, in the greenhouse, and in the growth chamber. At low transpiration rates the effect of the soil water status on LER was related to the concentration of ABA in the xylem sap and could be mimicked by feeding artificial ABA. Transpiring plants experienced a further reduction in LER, directly linked to the transpiration rate or leaf water status. Leaf zones located at more than 20 mm from the ligule stopped expanding during the day and renewed expansion during the night. Neither ABA concentration in the xylem sap, which did not appreciably vary during the day, nor ABA flux into shoots could account for the effect of evaporative demand. In particular, maximum LER was observed simultaneously with a minimum ABA flux in the droughted plants, but with a maximum ABA flux in ABA-fed plants. All data were interpreted as the superposition of two additive effects: the first involved ABA signaling and was observed during the night and in ABA-fed plants, and the second involved the transpiration rate and was observed even in well-watered plants. We suggest that a hydraulic signal is the most likely candidate for this second effect.

Salah, HBH.; Tardieu, F.

1997-01-01

50

The contribution of large trees to total transpiration rates in a pre-montane tropical forest and its implications for selective logging practices  

NASA Astrophysics Data System (ADS)

In the humid tropics, conservationists generally prefer selective logging practices over clearcutting. Large valuable timber is removed while the remaining forest is left relatively undisturbed. However, little is known about the impact of selective logging on site water balance. Because large trees have very deep sapwood and exposed canopies, they tend to have high transpiration. The first objective was to evaluate the methods used for scaling sap flow measurements to the watershed with particular emphasis on large trees. The second objective of this study was to determine the relative contribution of large trees to site water balance. Our study was conducted in a pre-montane transitional forest at the Texas A&M University Soltis Center in north-central Costa Rica. During the period between January and July 2012, sap flux was monitored in a 30-m diameter plot within a 10-ha watershed. Two pairs of heat dissipation sensors were installed in the outer 0-20 mm of each of 15 trees selected to represent the full range of tree sizes. In six of the largest trees, depth profiles were recorded at 10-mm intervals to a depth of 60 mm using compensation heat pulse sensors. To estimate sapwood basal area of the entire watershed, a stand survey was conducted in three 30-m-diameter plots. In each plot, we measured basal area of all trees and estimated sapwood basal area from sapwood depth measured in nearly half of the trees. An estimated 36.5% of the total sapwood area in this watershed comes from the outer 20 mm of sapwood, with the remaining 63.5% of sapwood from depths deeper than 20 mm. Nearly 13% of sapwood is from depths beyond 60 mm. Sap velocity profiles indicate the highest flow rates occurred in the 0-2 cm depths, with declines of 17% and 25% in the 20-40 mm and 40-60 mm ranges, respectively. Our results demonstrate the need to measure sap velocity profiles in large tropical trees. If total transpiration had been estimated solely from the 0-20 mm heat dissipation probes, it would have been overestimated by at least 15%. Total transpiration averaged 1.49 mm over the 6-month study period. However, the largest 10% of trees contributed disproportionately to this amount. Trees greater than 110 cm in diameter represented over half of the total basal area and 32% of the total sapwood area. These results highlight the importance of large trees in estimating watershed-scale transpiration. From a forest management perspective, selectively logging only the very largest trees, a common practice among these tropical forests of Costa Rica, is likely to disproportionately impact the site water balance unless water use of smaller trees can fully compensate.

Orozco, G.; Moore, G. W.; Miller, G. R.

2012-12-01

51

Interannual variation in transpiration peak of a hill evergreen forest in northern Thailand in the late dry season: Simulation of evapotranspiration with a soil-plant-air continuum model  

NASA Astrophysics Data System (ADS)

Previous research showed that transpiration in an evergreen broad-leaved forest in northern Thailand peaked at the end of the dry season for a few years period. To effectively simulate the peak and annual discharge, a rooting depth of 4 - 5 m was needed, assuming a soil texture, whose modeled relationship between soil hydraulic conductivity and soil water potential is similar to the measured values, under unsaturated conditions. The numerical simulation indicated that the late dry season transpiration peak is theoretically possible on the basis of rooting depth limitations to soil water use because the routing depth is within the reported maximum rooting depth of trees. Nonetheless, the late dry season transpiration peak may weaken when the soil moisture becomes dry beyond the rooting depth limitations to soil water use. But the interannual variations in the peak were not investigated. In this study, a soil-plant-air (SPAC) continuum multilayer model was used to numerically simulate evapotranspiration for an 8-year period in the forest in a dry tropical climate of northern Thailand, and the inter-annual variations in the transpiration peak were investigated. The numerical simulation indicated that the late dry season transpiration peak could weaken during the longest duration of soil drought in the 8-year period.

Tanaka, K.; Yoshifuji, N.; Suzuki, M.

2009-12-01

52

Compensation heat-pulse measurements of sap flow for estimating transpiration in young lemon trees  

Microsoft Academic Search

Potted two-year-old lemon trees [Citrus limon (L.) Burm. f.], cv. Verna grafted on sour orange (C. aurantium L.) rootstock, growing in greenhouse, were subjected to drought for 33 d. Control plants were daily irrigated at field capacity. Values of sap flow (SF) were compared with transpiration (E) rates measured gravimetrically. The results underlined the robustness and high sensitivity of the

J. J. Alarcon; M. F. Ortuno; E. Nicolas; R. Torres; A. Torrecillas

2005-01-01

53

Estimation of Transpiration and Water Use Efficiency Using Satellite and Field Observations  

NASA Technical Reports Server (NTRS)

Structure and function of terrestrial plant communities bring about intimate relations between water, energy, and carbon exchange between land surface and atmosphere. Total evaporation, which is the sum of transpiration, soil evaporation and evaporation of intercepted water, couples water and energy balance equations. The rate of transpiration, which is the major fraction of total evaporation over most of the terrestrial land surface, is linked to the rate of carbon accumulation because functioning of stomata is optimized by both of these processes. Thus, quantifying the spatial and temporal variations of the transpiration efficiency (which is defined as the ratio of the rate of carbon accumulation and transpiration), and water use efficiency (defined as the ratio of the rate of carbon accumulation and total evaporation), and evaluation of modeling results against observations, are of significant importance in developing a better understanding of land surface processes. An approach has been developed for quantifying spatial and temporal variations of transpiration, and water-use efficiency based on biophysical process-based models, satellite and field observations. Calculations have been done using concurrent meteorological data derived from satellite observations and four dimensional data assimilation for four consecutive years (1987-1990) over an agricultural area in the Northern Great Plains of the US, and compared with field observations within and outside the study area. The paper provides substantive new information about interannual variation, particularly the effect of drought, on the efficiency values at a regional scale.

Choudhury, Bhaskar J.; Quick, B. E.

2003-01-01

54

Numerical Analysis of Convection/Transpiration Cooling  

NASA Technical Reports Server (NTRS)

An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary, layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.

Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale

1999-01-01

55

Numerical Analysis of Convection/Transpiration Cooling  

NASA Technical Reports Server (NTRS)

An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.

Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale

1999-01-01

56

Tritium Concentrations in Environmental Samples and Transpiration Rates from the Vicinity of Mary's Branch Creek and Background Areas, Barnwell, South Carolina, 2007-2009  

USGS Publications Warehouse

Tritium in groundwater from a low-level radioactive waste disposal facility near Barnwell, South Carolina, is discharging to Mary's Branch Creek. The U.S. Geological Survey conducted an investigation from 2007 to 2009 to examine the tritium concentration in trees and air samples near the creek and in background areas, in groundwater near the creek, and in surface water from the creek. Tritium was found in trees near the creek, but not in trees from background areas or from sites unlikely to be in direct root contact with tritium-contaminated groundwater. Tritium was found in groundwater near the creek and in the surface water of the creek. Analysis of tree material has the potential to be a useful tool in locating shallow tritium-contaminated groundwater. A tritium concentration of 1.4 million picocuries per liter was measured in shallow groundwater collected near a tulip poplar located in an area of tritium-contaminated groundwater discharge. Evapotranspiration rates from the tree and tritium concentrations in water extracted from tree cores indicate that during the summer, this tulip poplar may remove more than 17.1 million picocuries of tritium per day from the groundwater that otherwise would discharge to Mary's Branch Creek. Analysis of air samples near the tree showed no evidence that the transpirative release of tritium to the air created a vapor hazard in the forest.

Vroblesky, Don A.; Canova, Judy L.; Bradley, Paul M.; Landmeyer, James E.

2009-01-01

57

Pressure Probe Measurements of the Driving Forces for Water Transport in Intact Higher Plants: Effects of Transpiration and Salinity  

Microsoft Academic Search

Effects of salinity on the driving forces for water transport in higher plants can only be accurately determined when the\\u000a “common” reaction pattern of the plant in the absence of salinity stress is known. We will demonstrate that in the absence\\u000a of salinity xylem and turgor pressures react very sensitively to changes in the environmental conditions (especially to light\\u000a intensity

Ulrich Zimmermann; Heike Schneider; Frank Thürmer; LARS H. WEGNER

58

Do hydraulic redistribution and nocturnal transpiration facilitate nutrient acquisition in Aspalathus linearis?  

PubMed

The significance of soil water redistribution by roots and nocturnal transpiration for nutrient acquisition were assessed for deep-rooted 3-year-old leguminous Aspalathus linearis shrubs of the Cape Floristic Region (South Africa). We hypothesised that hydraulic redistribution and nocturnal transpiration facilitate nutrient acquisition by releasing moisture in shallow soil to enable acquisition of shallow-soil nutrients during the summer drought periods and by driving water fluxes from deep to shallow soil powering mass-flow nutrient acquisition, respectively. A. linearis was supplied with sub-surface (1-m-deep) irrigation rates of 0, 2 or 4 L day(-1 )plant(-1). Some plants were unfertilized, whilst others were surface- or deep-fertilized (1 m depth) with Na(15)NO3 and CaP/FePO4. We also supplied deuterium oxide ((2)H2O) at 1 m depth at dusk and measured its predawn redistribution to shallow soil and plant stems. Hydraulic redistribution of deep water was substantial across all treatments, accounting for 34-72 % of surface-soil predawn moisture. Fourteen days after fertilization, the surface-fertilized plants exhibited increased hydraulic redistribution and increased (15)N and P acquisition with higher rates of deep-irrigation. Deep-fertilization also increased hydraulic redistribution to surface soils, although these plants additionally accumulated (2)H2O in their stem tissue overnight, probably due to nocturnal transpiration. Plants engaged in nocturnal transpiration also increased (15)N and P acquisition from deep fertilizer sources. Thus, both nocturnal transpiration and hydraulic redistribution increased acquisition of shallow soil N and P, possibly through a combination of increased nutrient availability and mobility. PMID:24972698

Matimati, Ignatious; Anthony Verboom, G; Cramer, Michael D

2014-08-01

59

A high CO2 -driven decrease in plant transpiration leads to perturbations in the hydrological cycle and may link terrestrial and marine loss of biodiversity: deep-time evidence.  

NASA Astrophysics Data System (ADS)

CO2 is obtained and water vapor simultaneously transpired through plant stomata, driving the water uptake of roots. Stomata are key elements of the Earth's hydrological cycle, since a large part of the evapotranspiration from the surface to the atmosphere takes place via stomatal pores. Plants exercise stomatal control, by adjusting stomatal size and/or density in order to preserve water while maintaining carbon uptake for photosynthesis. A global decrease in stomatal density and/or size causes a decrease in transpiration and has the potential to increase global runoff. Here we show, from 91 fossil leaf cuticle specimens from the Triassic/Jurassic boundary transition (Tr-J) of East Greenland, that both stomatal size and density decreased dramatically during the Tr-J, coinciding with mass extinctions, major environmental upheaval and a negative C-isotope excursion. We estimate that these developmental and structural changes in stomata resulted in a 50-60% drop in stomatal and canopy transpiration as calibrated using a stomatal model, based on empirical measurements and adjusted for fossil plants. We additionally present new field evidence indicating a change to increased erosion and bad-land formation at the Tr-J. We hypothesize that plant physiological responses to high carbon dioxide concentrations at the Tr-J may have increased runoff at the local and perhaps even regional scale. Increased runoff may result in increased flux of nutrients from land to oceans, leading to eutrophication, anoxia and ultimately loss of marine biodiversity. High-CO2 driven changes in stomatal and canopy transpiration therefore provide a possible mechanistic link between terrestrial ecological crisis and marine mass extinction at the Tr-J.

Steinthorsdottir, Margret; Woodward, F. Ian; Surlyk, Finn; McElwain, Jennifer C.

2013-04-01

60

Genetic variability for leaf growth rate and duration under water deficit in sunflower: analysis of responses at cell, organ, and plant level  

Microsoft Academic Search

Plants under water deficit reduce leaf growth, thereby reducing transpiration rate at the expense of reduced photosynthesis. The objective of this work was to analyse the response of leaf growth to water deficit in several sunflower genotypes in order to identify and quantitatively describe sources of genetic variability for this trait that could be used to develop crop varieties adapted

Gustavo A. Pereyra-Irujo; Luciano Velazquez; Leandra Lechner; Luis A. N. Aguirrezabal

2008-01-01

61

Determining the Amount of Transpiration from a Schoolyard Tree  

NSDL National Science Digital Library

Sttudents determine transpiration rate of five leaves, then estimate the number of leaves on the tree and total leaf surface area. Pounds of water transpired by the tree in a 24 hour period can then be estimated. Additional calculations are suggested.

Laurence Pomeroy (Santiago High School REV)

1994-07-30

62

Measurement of transpiration in Pinus taeda L. and Liquidambar styraciflua L. in an environmental chamber using tritiated water  

NASA Technical Reports Server (NTRS)

Transpiration rates of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were measured at two different atmospheric water vapor pressure deficits (V.P.D.) in a controlled environment growth chamber using tritiated water as a tracer. The trees were maintained in a sealed plant bed containing a hydroponic nutrient solution into which labeled water (spike) was introduced. Samples of leaves, chamber air, spiked nutrient solution and control water were assayed for ratio-activity using liquid scintillation techniques to determine transpiration rates. The transpiration rate of sweetgum in ml./hr./gm. (4.95) was found to be 5 times greater than that of loblolly pine (1.03) at 1.84 V.P.D. and 8 times greater at 6.74 V.P.D. (15.99 for sweetgum vs. 2.19 for pine). Transpiration (based on measurements of leaf radioactivity) in both species rose with increasing deficit; however sweetgum increased its output by 3 times while pine only doubled its rate. Cyclical changes in transpiration rates were noted in both species; the sweetgum cycle required a 6 hour interval whereas the pine cycle required a 9 hour interval.

Levy, G. F.; Sonenshine, D. E.; Czoch, J. K.

1976-01-01

63

Transpiration purged optical probe  

DOEpatents

An optical apparatus for clearly viewing the interior of a containment vessel by applying a transpiration fluid to a volume directly in front of the external surface of the optical element of the optical apparatus. The fluid is provided by an external source and transported by means of an annular tube to a capped end region where the inner tube is perforated. The perforation allows the fluid to stream axially towards the center of the inner tube and then axially away from an optical element which is positioned in the inner tube just prior to the porous sleeve. This arrangement draws any contaminants away from the optical element keeping it free of contaminants. In one of several embodiments, the optical element can be a lens, a viewing port or a laser, and the external source can provide a transpiration fluid having either steady properties or time varying properties.

2004-01-06

64

PILOT PLANT EXPLORATION OF SLOW RATE FILTRATION  

EPA Science Inventory

Alternatives to conventional coagulation water filtration plants (those that utilize coagulation, flocculation, sedimentation and filtration) may be appropriate for some small water utilities. One such alternative is slow rate filtration. This paper describes pilot plant studies ...

65

Does transpiration limit the growth of vegetation or vice versa?  

NASA Astrophysics Data System (ADS)

For hydrological or agronomic purposes, the potential rate of transpiration from vegetation is often calculated as a function of climatological variables, sometimes with the inclusion of a canopy resistance to water vapour diffusion. If, within leaves, the intercellular concentration of CO 2 is conservative, the canopy resistance must depend on the photosynthesis rate implying that potential transpiration depends on potential growth. The relevant form of the Penman-Monteith equation is developed to link water use efficiency with the conversion coefficient for solar radiation. When water is limiting, the maximum rate at which transpiration can occur depends mainly on the rate of extension of the root system and on the water "available" per unit soil volume. It follows that both potential and subpotential rates of transpiration are consequences of the assimilation of carbon by vegetation and its subsequent redistribution to form shoots and roots.

Monteith, J. L.

1988-07-01

66

Transpiration Cooling Experiment  

NASA Technical Reports Server (NTRS)

The transpiration cooling method was considered for a scram-jet engine to accommodate thermally the situation where a very high heat flux (200 Btu/sq. ft sec) from hydrogen fuel combustion process is imposed to the engine walls. In a scram-jet engine, a small portion of hydrogen fuel passes through the porous walls of the engine combustor to cool the engine walls and at the same time the rest passes along combustion chamber walls and is preheated. Such a regenerative system promises simultaneously cooling of engine combustor and preheating the cryogenic fuel. In the experiment, an optical heating method was used to provide a heat flux of 200 Btu/sq. ft sec to the cylindrical surface of a porous stainless steel specimen which carried helium gas. The cooling efficiencies by transpiration were studied for specimens with various porosity. The experiments of various test specimens under high heat flux have revealed a phenomenon that chokes the medium flow when passing through a porous structure. This research includes the analysis of the system and a scaling conversion study that interprets the results from helium into the case when hydrogen medium is used.

Song, Kyo D.; Ries, Heidi R.; Scotti, Stephen J.; Choi, Sang H.

1997-01-01

67

Native Trees and Salt Cedar: Quantifying Transpiration at Intermittent and Perennial Streamflows on the San Pedro River  

NASA Astrophysics Data System (ADS)

Native cottonwood-willow forests that historically dominated south-western riparian areas are being replaced by salt cedar (Tamarix ramosissima) on the majority of regulated western rivers. Some studies of salt cedar have indicated its water use is considerably greater than native trees and depletes alluvial aquifers of groundwater; however, other studies have shown low to moderate water use by salt cedar. Results have varied on temporal and spatial scales making it difficult to draw firm conclusions. We compared whole plant transpiration by native riparian cottonwood (Populus fremontii) trees and salt cedar in co-occurring communities at the upper and lower San Pedro River in Arizona during 2006 and 2007, respectively. Water use by both species was monitored and quantified using the heat balance sap flow technique at intermittent and perennial reaches during the pre- monsoon season, a period of high atmospheric water demand. Our 2006 measurements in a riparian transition zone at an intermittent reach of the San Pedro River appeared to differ with earlier studies that salt cedar has higher transpiration rates, as cottonwoods and salt cedar demonstrated similar, low transpiration rates. However transpiration results from a 2007 study on these same species at a perennial reach of the San Pedro River indicate significantly higher transpiration by salt cedar and moderate increases for cottonwoods compared to the intermittent site.

McGuire, R. R.; Glenn, E. P.; Scott, R. L.; Moran, M. S.

2007-12-01

68

Coordination of Leaf Photosynthesis, Transpiration, and Structural Traits in Rice and Wild Relatives (Genus Oryza).  

PubMed

The genus Oryza, which includes rice (Oryza sativa and Oryza glaberrima) and wild relatives, is a useful genus to study leaf properties in order to identify structural features that control CO(2) access to chloroplasts, photosynthesis, water use efficiency, and drought tolerance. Traits, 26 structural and 17 functional, associated with photosynthesis and transpiration were quantified on 24 accessions (representatives of 17 species and eight genomes). Hypotheses of associations within, and between, structure, photosynthesis, and transpiration were tested. Two main clusters of positively interrelated leaf traits were identified: in the first cluster were structural features, leaf thickness (Thick(leaf)), mesophyll (M) cell surface area exposed to intercellular air space per unit of leaf surface area (S(mes)), and M cell size; a second group included functional traits, net photosynthetic rate, transpiration rate, M conductance to CO(2) diffusion (g(m)), stomatal conductance to gas diffusion (g(s)), and the g(m)/g(s) ratio.While net photosynthetic rate was positively correlated with gm, neither was significantly linked with any individual structural traits. The results suggest that changes in gm depend on covariations of multiple leaf (S(mes)) and M cell (including cell wall thickness) structural traits. There was an inverse relationship between Thick(leaf) and transpiration rate and a significant positive association between Thick(leaf) and leaf transpiration efficiency. Interestingly, high g(m) together with high g(m)/g(s) and a low S(mes)/g(m) ratio (M resistance to CO(2) diffusion per unit of cell surface area exposed to intercellular air space) appear to be ideal for supporting leaf photosynthesis while preserving water; in addition, thick M cell walls may be beneficial for plant drought tolerance. PMID:23669746

Giuliani, Rita; Koteyeva, Nuria; Voznesenskaya, Elena; Evans, Marc A; Cousins, Asaph B; Edwards, Gerald E

2013-07-01

69

Export of Abscisic Acid, 1-Aminocyclopropane-1-Carboxylic Acid, Phosphate, and Nitrate from Roots to Shoots of Flooded Tomato Plants (Accounting for Effects of Xylem Sap Flow Rate on Concentration and Delivery).  

PubMed Central

We determined whether root stress alters the output of physiologically active messages passing from roots to shoots in the transpiration stream. Concentrations were not good measures of output. This was because changes in volume flow of xylem sap caused either by sampling procedures or by effects of root stress on rates of whole-plant transpiration modified concentrations simply by dilution. Thus, delivery rate (concentration x sap flow rate) was preferred to concentration as a measure of solute output from roots. To demonstrate these points, 1-aminocyclopropane-1-carboxylic acid (ACC), abscisic acid, phosphate, nitrate, and pH were measured in xylem sap of flooded and well-drained tomato (Lycopersicon esculentum Mill., cv Ailsa Craig) plants expressed at various rates from pressurized detopped roots. Concentrations decreased as sap flow rates were increased. However, dilution of solutes was often less than proportional to flow, especially in flooded plants. Thus, sap flowing through detopped roots at whole-plant transpiration rates was used to estimate solute delivery rates in intact plants. On this basis, delivery of ACC from roots to shoots was 3.1-fold greater in plants flooded for 24 h than in well-drained plants, and delivery of phosphate was 2.3-fold greater. Delivery rates of abscisic acid and nitrate in flooded plants were only 11 and 7%, respectively, of those in well-drained plants.

Else, M. A.; Hall, K. C.; Arnold, G. M.; Davies, W. J.; Jackson, M. B.

1995-01-01

70

Estimating transpiration in an intercropping system: measuring sap flow inside the oasis  

Microsoft Academic Search

The quantity of water transpired by a plant is an important factor in investigating irrigation control, biomass production, and, in studies of plant–water relations. Measuring sap flow in plant stems provides a method for estimating transpiration. Sap flow within the xylem of date palm and apricot, inside an oasis in the south of Tunisia, was monitored continuously using the Granier’s

Mohamed Habib Sellami; Mohamed Salah Sifaoui

2003-01-01

71

Performance of a transpiration-regenerative cooled rocket thrust chamber  

NASA Technical Reports Server (NTRS)

The analysis, design, fabrication, and testing of a liquid rocket engine thrust chamber which is gas transpiration cooled in the high heat flux convergent portion of the chamber and water jacket cooled (simulated regenerative) in the barrel and divergent sections of the chamber are described. The engine burns LOX-hydrogen propellants at a chamber pressure of 600 psia. Various transpiration coolant flow rates were tested with resultant local hot gas wall temperatures in the 800 F to 1400 F range. The feasibility of transpiration cooling with hydrogen and helium, and the use of photo-etched copper platelets for heat transfer and coolant metering was successfully demonstrated.

Valler, H. W.

1979-01-01

72

Energy balance and transpiration from tussock grassland in New Zealand  

NASA Astrophysics Data System (ADS)

The energy balance was measured for the dry canopy of narrow-leaved snow tussock ( Chionochloa rigida), and measurements of transpiration were obtained from a large weighing lysimeter. Typical maximum summer transpiration rates of 0.21 0.43 mmhr-1 (140 290 W m-2) were recorded. The latent heat flux accounted for less than 40% of net radiation. The estimated value of the bulk stomatal resistance ( r ST) for 29 days was 158 s m-1, and the decoupling parameter (?) was 0.17. Transpiration rates were not driven directly by net radiation, but were closely linked to the size of the regional saturation deficit imposed at the level of the canopy by efficient overhead mixing, and were constrained by a large bulk stomatal resistance. A linear relationship between r ST and the saturation deficit is proposed as a realistic method for estimating transpiration for water yield studies of tussock catchments.

Campbell, D. I.

1989-01-01

73

Effect of transpiration on Pb uptake by lettuce and on water soluble low molecular weight organic acids in rhizosphere.  

PubMed

The effect of transpiration (high and low) on Pb uptake by leaf lettuce and on water soluble low molecular weight organic acids (LMWOAs) in rhizosphere has been studied. After two weeks of growth the plants were cultured in greenhouse for more four weeks and two days. Pb(NO(3))(2) solutions of different concentrations (100, 200, and 300 mg l(-1) of Pb) were then added to the quartz sand pots of different plants and studies were initiated. Blank experiments (without treating the quartz sand pots with Pb(NO(3))(2) solutions) were also run in parallel. No significant differences in the growth of the plants with the concentrations of added Pb(NO(3))(2) solutions were observed by both low and high transpirations at the end of the 0, 3rd, and 10th days of studies. The total evaporation of the volatiles during 10 days did not depend on the concentration of Pb(2+) but with high transpiration the rate of evaporation was significantly higher than with low transpiration. Uptake of Pb by shoots and roots of the plants was found to be proportional to the concentration of various Pb(NO(3))(2) solutions added and more accumulation was observed in roots than in shoots at the end of 3rd and 10th days. High transpiration created more Pb uptake than low transpiration did. One volatile acid, propionic acid and nine non-volatile acids, lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, D-tartaric, trans-aconitic, and citric acids in rhizosphere quartz sands were identified and quantified by gas chromatography (GC) analysis. D-Tartaric and citric acids were major among the non-volatile acids. The amount of LMWOAs in rhizosphere quartz sands increased with the higher amount of Pb uptake and also with the duration of studies. The total quantities of the LMWOAs in the rhizosphere quartz sands were significantly higher under high transpiration with 300 mg l(-1) Pb solution addition at the end of 10th day. The present study shows prominent correlation between transpiration and uptake of heavy metal and interesting correlation between Pb contaminated level and quantity of water soluble LMWOAs in rhizosphere quartz sands. The latter thus deserves of further studies. PMID:16554084

Liao, Y C; Chien, S W Chang; Wang, M C; Shen, Y; Hung, P L; Das, Biswanath

2006-10-01

74

Quantifying Understory Transpiration in a Semiarid Riparian Area  

NASA Astrophysics Data System (ADS)

One of the most challenging components to estimate when determining water budgets in semiarid basins is riparian evapotranspiration (ET). Much research has been conducted upon riparian overstory vegetation in these areas; however understory vegetation water use has been ignored due to measurement difficulties and the belief that its quantity is negligible. To better understand the magnitude of understory water use in a semiarid riparian ecosystem, we measured whole plant transpiration of the dominant understory shrub, seep willow (Baccharis salicifolia), along a perennial reach of the San Pedro River in southeastern Arizona. . Shrub transpiration was monitored using the heat balance sap flow technique and was compared under two environmental conditions: a shrub patch located in a more open environment with decreased overstory canopy cover, and a more closed shrub patch situated more directly underneath a cottonwood (Populus fremontii) forest canopy. Despite the differences in atmospheric forcing, stand-level transpiration at both sites was similar and indicated that transpiration was rarely demand-limited. Growing season transpiration totals for seep willow were much greater than precipitation and of comparable magnitude to the overstory cottonwood transpiration. These results suggest that understory water use can be an important component of a riparian water budget, especially in regions like the western U.S. where evaporative demand is often high.

McGuire, R. R.; Scott, R. L.

2005-12-01

75

Effect of plant growth on dehydration rates and microbial populations in sewage biosolids.  

PubMed

The high water content of sewage biosolids makes them expensive to transport. Two experiments were done to see if it was practical to use transpiration by plants as a low cost method to dehydrate biosolids. (i) To assess biosolids as a growth-medium for plants, maize, beans, pumpkin, forage oats and an annual ryegrass were grown in pots of fresh biosolids. Plant growth varied between species and potassium deficiency was found to be a limiting factor for barley. Roots were slow to penetrate anoxic biosolids in the bottom of the pots. (ii) Dehydration rates were measured in 30 litre boxes of biosolids from two different sources. Boxes were planted with maize or beans, or kept fallow. Despite the high (73-83%) initial water content of the biosolids, plants were susceptible to wilting on warm days which suggested that a significant proportion of the water in biosolids is not freely available to plants. Shrinkage caused a major reduction in biosolids volume in both experiments. When change in volume of the biosolids residue was accounted for, there was a 56% average water loss in planted treatments and 34% water loss in the fallow treatment. This indicates that planting may have some potential as a technique to accelerate dehydration of biosolids. Water contents were not reduced sufficiently to influence biosolids microbial populations. PMID:16797975

Crush, J R; Sarathchandra, U; Donnison, A

2006-12-01

76

Does night-time transpiration contribute to anisohydric behaviour in a Vitis vinifera cultivar?  

PubMed Central

The hypothesis that vines of the Semillon wine grape variety show anisohydric behaviour was tested, i.e. that tissue hydration is unstable under fluctuating environmental conditions. Stomatal conductance and transpiration rates from leaves were measured during the day and at night. Leaf water potential (?l) in Semillon was negatively correlated to vapour pressure deficit (VPD) both predawn and during the day. Furthermore, ?l fell to significantly lower values than in any of the nine other varieties examined. Night-time values of stomatal conductance (gn) and transpiration (En) in Semillon were up to four times higher than in other varieties; plants enclosed in plastic bags overnight to reduce En resulted in better plant–soil equilibration so that predawn ?l in Semillon was the same as in Grenache. These data indicate that the hypothesis is supported, and that night-time transpiration contributes significantly to the low ?l values in Semillon during warm, dry nights. The other contributing factor is daytime stomatal conductance (gday), which in Semillon leaves was higher than in other varieties, although the decline in gday with increasing VPD was greater in Semillon than in Shiraz or Grenache. The high values of gday were associated with high rates of transpiration (Eday) by Semillon through a day when VPD reached 4.5 kPa. When compared to other varieties, Semillon was not unusual in terms of root length density, stomatal density, xylem sap abscisic acid, or leaf electrolyte leakage. Night-time and daytime water loss and insufficient stomatal regulation therefore account for the tendency to anisohydric behaviour shown by Semillon.

Rogiers, Suzy Y.; Greer, Dennis H.; Hutton, Ron J.; Landsberg, Joe J.

2009-01-01

77

CCMR: Modeling Transpiration with Porous Silicon Membranes  

NSDL National Science Digital Library

The purpose of the project was to better understand the characteristics of porous silicon membranes and assess their possible applications, especially in the area of heat transfer. Porous silicon can be used in the modeling of transpiration in plants, where water is transported under negative pressure. If porous silicon is found to be able to hold high enough levels of tension (negative pressure), then it has great potential in cooling systems; it could act as a âself-driving pumpâ that would not need large amounts of external energy like most current systems.

Jilo, Allen

2010-08-15

78

Effect of downy mildew development on transpiration of cucumber leaves visualized by digital infrared thermography.  

PubMed

ABSTRACT Disease progress of downy mildew on cucumber leaves, caused by the obligate biotrophic pathogen Pseudoperonospora cubensis, was shown to be associated with various changes in transpiration depending on the stage of pathogenesis. Spatial and temporal changes in the transpiration rate of infected and noninfected cucumber leaves were visualized by digital infrared thermography in combination with measurements of gas exchange as well as microscopic observations of pathogen growth within plant tissue and stomatal aperture during pathogenesis. Transpiration of cucumber leaf tissue was correlated to leaf temperature in a negative linear manner (r = -0.762, P < 0.001, n = 18). Leaf areas colonized by Pseudoperonospora cubensis exhibited a presymptomatic decrease in leaf tem perature up to 0.8 degrees C lower than noninfected tissue due to abnormal stomata opening. The appearance of chlorosis was associated with a cooling effect caused by the loss of integrity of cell membranes leading to a larger amount of apoplastic water in infected tissue. Increased water loss from damaged cells and the inability of infected plant tissue to regulate stomatal opening promoted cell death and desiccation of dying tissue. Ultimately, the lack of natural cooling from necrotic tissue was associated with an increase in leaf temperature. These changes in leaf temperature during downy mildew development resulted in a considerable heterogeneity in temperature distribution of infected leaves. The maximum temperature difference within a thermogram of cucumber leaves allowed the discrimination between healthy and infected leaves before visible symptoms appeared. PMID:18943115

Lindenthal, Miriam; Steiner, Ulrike; Dehne, H-W; Oerke, E-C

2005-03-01

79

Spatial patterns of simulated transpiration response to climate variability in a snow dominated mountain ecosystem  

USGS Publications Warehouse

Transpiration is an important component of soil water storage and stream-flow and is linked with ecosystem productivity, species distribution, and ecosystem health. In mountain environments, complex topography creates heterogeneity in key controls on transpiration as well as logistical challenges for collecting representative measurements. In these settings, ecosystem models can be used to account for variation in space and time of the dominant controls on transpiration and provide estimates of transpiration patterns and their sensitivity to climate variability and change. The Regional Hydro-Ecological Simulation System (RHESSys) model was used to assess elevational differences in sensitivity of transpiration rates to the spatiotemporal variability of climate variables across the Upper Merced River watershed, Yosemite Valley, California, USA. At the basin scale, predicted annual transpiration was lowest in driest and wettest years, and greatest in moderate precipitation years (R2 = 0.32 and 0.29, based on polynomial regression of maximum snow depth and annual precipitation, respectively). At finer spatial scales, responsiveness of transpiration rates to climate differed along an elevational gradient. Low elevations (1200-1800 m) showed little interannual variation in transpiration due to topographically controlled high soil moistures along the river corridor. Annual conifer stand transpiration at intermediate elevations (1800-2150 m) responded more strongly to precipitation, resulting in a unimodal relationship between transpiration and precipitation where highest transpiration occurred during moderate precipitation levels, regardless of annual air temperatures. Higher elevations (2150-2600 m) maintained this trend, but air temperature sensitivities were greater. At these elevations, snowfall provides enough moisture for growth, and increased temperatures influenced transpiration. Transpiration at the highest elevations (2600-4000 m) showed strong sensitivity to air temperature, little sensitivity to precipitation. Model results suggest elevational differences in vegetation water use and sensitivity to climate were significant and will likely play a key role in controlling responses and vulnerability of Sierra Nevada ecosystems to climate change. Copyright ?? 2008 John Wiley & Sons, Ltd.

Christensen, L.; Tague, C. L.; Baron, J. S.

2008-01-01

80

Role of transpiration suppression by evaporation of intercepted water in improving irrigation efficiency  

Microsoft Academic Search

Sprinkler irrigation efficiency declines when applied water intercepted by the crop foliage, or gross interception (Igross), as well as airborne droplets and ponded water at the soil surface evaporate before use by the crop. However, evaporation of applied water can also supply some of the atmospheric demands usually met by plant transpiration. Any suppression of crop transpiration from the irrigated

J. A. Tolk; T. A. Howell; J. L. Steiner; D. R. Krieg; A. D. Schneider

1995-01-01

81

Coordination of Leaf Photosynthesis, Transpiration, and Structural Traits in Rice and Wild Relatives (Genus Oryza)1[W][OA  

PubMed Central

The genus Oryza, which includes rice (Oryza sativa and Oryza glaberrima) and wild relatives, is a useful genus to study leaf properties in order to identify structural features that control CO2 access to chloroplasts, photosynthesis, water use efficiency, and drought tolerance. Traits, 26 structural and 17 functional, associated with photosynthesis and transpiration were quantified on 24 accessions (representatives of 17 species and eight genomes). Hypotheses of associations within, and between, structure, photosynthesis, and transpiration were tested. Two main clusters of positively interrelated leaf traits were identified: in the first cluster were structural features, leaf thickness (Thickleaf), mesophyll (M) cell surface area exposed to intercellular air space per unit of leaf surface area (Smes), and M cell size; a second group included functional traits, net photosynthetic rate, transpiration rate, M conductance to CO2 diffusion (gm), stomatal conductance to gas diffusion (gs), and the gm/gs ratio. While net photosynthetic rate was positively correlated with gm, neither was significantly linked with any individual structural traits. The results suggest that changes in gm depend on covariations of multiple leaf (Smes) and M cell (including cell wall thickness) structural traits. There was an inverse relationship between Thickleaf and transpiration rate and a significant positive association between Thickleaf and leaf transpiration efficiency. Interestingly, high gm together with high gm/gs and a low Smes/gm ratio (M resistance to CO2 diffusion per unit of cell surface area exposed to intercellular air space) appear to be ideal for supporting leaf photosynthesis while preserving water; in addition, thick M cell walls may be beneficial for plant drought tolerance.

Giuliani, Rita; Koteyeva, Nuria; Voznesenskaya, Elena; Evans, Marc A.; Cousins, Asaph B.; Edwards, Gerald E.

2013-01-01

82

Idaho Chemical Processing Plant failure rate database  

Microsoft Academic Search

This report represents the first major upgrade to the Idaho Chemical Processing Plant (ICPP) Failure Rate Database. This upgrade incorporates additional site-specific and generic data while improving on the previous data reduction techniques. In addition, due to a change in mission at the ICPP, the status of certain equipment items has changed from operating to standby or off-line. A discussion

T. G. Alber; C. R. Hunt; S. P. Fogarty; J. R. Wilson

1995-01-01

83

Night-time transpiration can decrease hydraulic redistribution  

Microsoft Academic Search

C3 plants dominate many landscapes and are critically important for ecosystem water cycling.At night,plant water losses can include transpiration (Enight) from the canopy and hydraulic redistribution (HR) from roots. We tested whether Enight limits the magnitude of HR in a greenhouse study using Artemisia tridentata, Helianthus anomalus and Quercus laevis. Plants were grown with their roots split between two compartments.

AVA R. HOWARD; MARC W. VAN IERSEL; JAMES H. RICHARDS; LISA A. DONOVAN

2009-01-01

84

Assessing transpiration in the tussock grass Stipa tenacissima L.: the crucial role of the interplay between morphology and physiology  

NASA Astrophysics Data System (ADS)

Plant transpiration has a key role on both plant performance and ecosystem functioning in arid zones, but realistic estimates at appropriate spatial-temporal scales are scarce. Leaf and tiller morphology and crown architecture were studied together with leaf physiology and whole plant water balance in four individual plants of Stipa tenacissima of different sizes to determine the relative influence of processes taking place at different spatial and temporal scales on whole plant transpiration. Transpiration was estimated in potted plants by leaf-level gas exchange techniques (infrared gas analyzer and porometer), by sap flow measurements, and by integrating leaf physiology and crown architecture with the 3-D computer model Yplant. Daily transpiration of each individual plant was monitored using a gravimetric method, which rendered the reference values. Leaves on each individual plant significantly varied in their physiological status. Young and green parts of the leaves showed five times higher chlorophyll concentration and greater photosynthetic capacity than the senescent parts of the foliage. Instantaneous leaf-level transpiration measurements should not be used to estimate plant transpiration, owing to the fact that extrapolations overestimated individual transpiration by more than 100%. Considering leaf age effects and scaling the estimates according to the relative amount of each foliage category reduced this difference to 46% though it was still significantly higher than gravimetric measurements. Sap flow calculations also overestimated tussock transpiration. However, 3-D reconstruction of plants with Yplant and transpiration estimates, considering both the physiological status and the daily pattern of radiation experienced by each individual leaf section within the crown, matched the gravimetric measurements (differences were only 4.4%). The complex interplay of leaf physiology and crown structure must be taken into account in scaling up plant transpiration from instantaneous, leaf-level measurements, and our study indicates that transpiration of complex crowns is easily overestimated.

Ramírez, David A.; Valladares, Fernando; Blasco, Adela; Bellot, Juan

2006-11-01

85

Thermographic measurements on plant leaves  

NASA Astrophysics Data System (ADS)

An important process of plant physiology is the transpiration of plant leaves. It is actively controlled by pores (stomata) in the leaf and the governing feature for vital factors such as gas exchange and water transport affixed to which is the nutrient transport from the root to the shoot. Because of its importance, the transpiration and water transport in leaves have been extensively studied. However, current measurement techniques provide poor spatial and temporal resolution. With the use of one single low-NETD infrared camera important parameter of plant physiology such as transpiration rates, heat capacity per unit area of the leaf and the water flow velocity can be measured to high temporal and special resolution by techniques presented in this paper. The latent heat flux of a plant, which is directly proportional to the transpiration rate, can be measured with passive thermography. Here use is made of the linear relationship between the temperature difference between a non transpiring reference body and the transpiring leaf and the latent heat flux. From active thermography the heat capacity per unit area of the leaf can be measured. This method is termed active, because the response of the leaf temperature to an imposed energy flux is measured. Through the use of digital image processing techniques simultaneous measurements of the velocity field and temporal change of heated water parcels traveling through the leaf can be estimated from thermal image sequences.

Garbe, Christoph; Schurr, Ulrich; Jaehne, Bernd

2002-03-01

86

Use of high-resolution thermal infrared remote sensing and “three-temperature model” for transpiration monitoring in arid inland river catchment  

NASA Astrophysics Data System (ADS)

Based on high-resolution thermal infrared remote sensing and the three-temperature model (3T model), we developed a new algorithm for mapping transpiration. The necessary input parameters were surface temperature, air temperature, and solar radiation only. Therefore, in comparison with conventional methods, it is a simple and potentially valuable way to employ the thermal infrared remote sensing application. By using the proposed method, transpiration of sixteen types of typical vegetation in the upper and middle reaches of the Heihe River Basin in Northwestern China were calculated pixel by pixel. We evaluated modeled evapotranspiration with an eddy covariance (EC) result from the established regression equation, and a scatter correlation plot for the measured and estimated transpiration indicated that the model estimate is within acceptable limits, with a correlation coefficient of R2 = 0.796. Compared with the desert-oasis transitional zone, the maximum transpiration rate at the Gobi Desert presented a little earlier but was smaller. This great difference may imply that different types of plants have different water-use abilities and drought tolerances. Thus, the transpiration estimation with the 3T model, using high-resolution thermal infrared remote sensing data, can provide not only a bridge between large-scale and point observation with a measure of m2 from the infrared thermal imager, but also provide decision support for operational water management issues.

Tian, Fei; Qiu, GuoYu; Lü, YiHe; Yang, YongHui; Xiong, Yujiu

2014-07-01

87

Thermodynamic balance of photosynthesis and transpiration at increasing CO2 concentrations and rapid light fluctuations.  

PubMed

Experimental and theoretical flux models have been developed to reveal the influence of sun flecks and increasing CO2 concentrations on the energy and entropy balances of the leaf. The rapid and wide range of fluctuations in light intensity under field conditions were simulated in a climatic gas exchange chamber and we determined the energy and entropy balance of the leaf based on radiation and gas exchange measurements. It was estimated that the energy of photosynthetic active radiation (PAR) accounts for half of transpiration, which is the main factor responsible for the exportation of the entropy generated in photosynthesis (Sg) out of the leaf in order to maintain functional the photosynthetic machinery. Although the response of net photosynthetic production to increasing concentrations of CO2 under fluctuating light is similar to that under continuous light, rates of transpiration respond slowly to changes of light intensity and are barely affected by the concentration of CO2 in the range of 260-495 ppm, in which net photosynthesis increases by more than 100%. The analysis of the results confirms that future increases of CO2 will improve the efficiency of the conversion of radiant energy into biomass, but will not reduce the contribution of plant transpiration to the leaf thermal balance. PMID:24345393

Marín, Dolores; Martín, Mercedes; Serrot, Patricia H; Sabater, Bartolomé

2014-02-01

88

Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients.  

PubMed

Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 ?m mesh from which nutrients could move by diffusion or mass-flow (termed 'mass-flow' treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed 'interception' treatment). 'Mass-flow' plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (gs), 1.2-fold higher intercellular [CO2] (Ci), and 3.4-fold lower water use efficiency than 'interception' plants, despite comparable values of photosynthetic rate (A). E, gs, and Ci first increased and then decreased with increasing distance from the N source to values even lower than those of 'interception' plants. 'Mass-flow' plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties. PMID:24231035

Matimati, Ignatious; Verboom, G Anthony; Cramer, Michael D

2014-01-01

89

Oxygen isotope signatures of transpired water vapor: the role of isotopic non-steady-state transpiration under natural conditions.  

PubMed

The oxygen isotope signature of water is a powerful tracer of water movement from plants to the global scale. However, little is known about the short-term variability of oxygen isotopes leaving the ecosystem via transpiration, as high-frequency measurements are lacking. A laser spectrometer was coupled to a gas-exchange chamber directly estimating branch-level fluxes in order to evaluate the short-term variability of the isotopic composition of transpiration (?E ) and to investigate the role of isotopic non-steady-state transpiration under natural conditions in cork-oak trees (Quercus suber) during distinct Mediterranean seasons. The measured ?(18) O of transpiration (?E ) deviated from isotopic steady state throughout most of the day even when leaf water at the evaporating sites was near isotopic steady state. High agreement was found between estimated and modeled ?E values assuming non-steady-state enrichment of leaf water. Isoforcing, that is, the influence of the transpirational ?(18) O flux on atmospheric values, deviated from steady-state calculations but daily means were similar between steady state and non-steady state. However, strong daytime isoforcing on the atmosphere implies that short-term variations in ?E are likely to have consequences for large-scale applications, for example, partitioning of ecosystem fluxes or satellite-based applications. PMID:24909361

Dubbert, Maren; Cuntz, Matthias; Piayda, Arndt; Werner, Christiane

2014-09-01

90

Variability of Recombination Rates in Higher Plants  

Microsoft Academic Search

\\u000a Recombination and chiasma frequency, like other features of meiosis, are subject to various genetic control mechanisms. Here,\\u000a we give an overview of the genetic and environmental factors as well as the genomic structures that play a role for the variability\\u000a of recombination rates in plant genomes. Suppressed or greatly reduced recombination is observed in chromosomal regions that\\u000a contain repetitive sequences

Elisabeth Esch; Renate Horn

91

The positive effect of skin transpiration in peach fruit growth.  

PubMed

The effect of fruit transpiration on the mechanisms driving peach (Prunus persica (L.) Batsch) daily growth was investigated. In peach, fruit water losses increase during the season and might play a key role in determining fruit growth. Skin transpiration was reduced during the cell expansion stage by enclosing fruit in plastic bags fitted with holes. In the first year, diameter changes of bagged and control fruit were precisely monitored for 15 days, and percentage dry matter and soluble solids content were determined during the experiment and at harvest. In the second year, midday fruit water potential, daily patterns of fruit growth and of vascular and transpiration flows were monitored. Bagging reduced fruit daily growth on some days, and negatively affected both fruit dry matter percentage and soluble solids content. Fruit transpiration rate was reduced during the midday hours, thus increasing midday fruit water potential and lowering xylem inflows. In accordance with the Münch hypothesis on traslocation, these conditions likely decreased the necessary gradient needed for the transport of phloem sap to sink organs, as in the afternoon, bagged fruit showed lower phloem inflows. These data suggest that skin transpiration in peach has a positive effect on fruit growth, as it enhances fruit phloem import. PMID:20417987

Morandi, Brunella; Manfrini, Luigi; Losciale, Pasquale; Zibordi, Marco; Corelli-Grappadelli, Luca

2010-09-01

92

Transpiration and evaporation from heather Moorland  

NASA Astrophysics Data System (ADS)

The energy balance of an upland heath dominated by heather ( Calluna vulgaris) was measured in dry and wet weather. Median values of both transpiration and evaporation rates were ca. 2 mm hr-1. The median Bowen ratio for the dry canopy was 2.0 and for the wet canopy 0.6. On dry days the median value of the saturation deficit was only 3.8 mb and that of the climatological resistance was 30 s m-1. The bulk stomatal resistance increased from ca. 50 s m -2 in the morning to over 290 s m-1 in the afternoon with an overall median value of 110 s m-1. Transpiration from the dry canopy was controlled by a combination of small saturation deficits and large stomatal resistances. The median value of the boundary-layer resistance of the canopy was 22 s m-1 and was low partly because of a large low-level drag coefficient. Saturation deficits on wet days were close to zero and evaporation of intercepted water proceeded at close to the equilibrium rate, being largely limited by the low fluxes of available energy. The water loss from heather was compared with simulated losses from coniferous forest, herbaceous crops and grassland in the same conditions to evaluate the effects of vegetation on water loss from catchments.

Miranda, A. C.; Jarvis, P. G.; Grace, J.

1984-03-01

93

Environmental controls on saltcedar (Tamarix spp.) transpiration and stomatal conductance and implications for determining evapotranspiration by remote sensing  

NASA Astrophysics Data System (ADS)

Saltcedar is an introduced, salt-tolerant shrub that now dominates many flow-regulated western U.S. rivers. Saltcedar control programs have been implemented to salvage water and to allow the return of native vegetation to infested rivers. However, there is much debate about how much water saltcedar actually uses and the range of ecohydrological niches it occupies. Ground methods for measuring riparian zone ET have improved and there is considerable interest in developing remote sensing methods for saltcedar to conduct wide-area monitoring of water use. Both thermal band and vegetation index methods have been used to estimate riparian ET. However, several problems present themselves in applying existing remote sensing methods to riparian corridors. First, many riparian corridors are narrow and are surrounded by arid uplands, hence they cannot be treated as energetically closed systems, an assumption of thermal band methods that calculate ET as a residual in the surface energy balance. Second, contrary to the assumption that riparian phreatophytes typically grow under unstressed conditions since they are rooted into groundwater, we find that saltcedar stands are under substantial degrees of apparent moisture stress, exhibiting midday depression of transpiration and stomatal conductance, and decreases in stomatal conductance over the growing season as depth to groundwater increases. Furthermore, the degree of stress is site-specific, depending on local soil texture, salinity of the groundwater and distance from the river. This violates a key assumption of vegetation index methods for estimating ET. The implications of these findings for arid-zone riparian ecohydrology and for remote sensing methods that assume either a constant daily evaporative fraction or rate of stomatal conductance will be discussed using saltcedar stands measured in the Cibola NWR on the lower Colorado River as a case study. Daily rates of saltcedar transpiration ranged from 1.6-3.0 mm/m2 leaf/day, while LAI varied over a narrower range, from 2.0 - 2.9. Differences in leaf-level transpiration were due to differences in stomatal conductance among sites. Sites close to the river had higher transpiration rates than sites further away, and sites with more saline water had lower leaf-level transpiration rates. Leaf-level transpiration rates were higher in June and July, when aquifers were closer to the surface, than in August and September, when water levels had dropped. High transpiration rates were associated with finer textured soil compared to plants growing in sandy soils. Low transpiration rates were manifested by moderate to severe midday depression of stomatal conductance and transpiration. These limitations constrained the rate of saltcedar ET to about 40% of ETo, and also reduced the accuracy of remote sensing estimates of ET, which assume a constant rate of stomatal conductance during midday.

Nagler, P. L.; Glenn, E. P.; morino, K.

2012-12-01

94

Transpiring Cooling of a Scram-Jet Engine Combustion Chamber  

NASA Technical Reports Server (NTRS)

The peak cold-wall heating rate generated in a combustion chamber of a scram-jet engine can exceed 2000 Btu/sq ft sec (approx. 2344 W/sq cm). Therefore, a very effective heat dissipation mechanism is required to sustain such a high heating load. This research focused on the transpiration cooling mechanism that appears to be a promising approach to remove a large amount of heat from the engine wall. The transpiration cooling mechanism has two aspects. First, initial computations suggest that there is a reduction, as much as 75%, in the heat flux incident on the combustion chamber wall due to the transpirant modifying the combustor boundary layer. Secondly, the heat reaching the combustor wall is removed from the structure in a very effective manner by the transpirant. It is the second of these two mechanisms that is investigated experimentally in the subject paper. A transpiration cooling experiment using a radiant heating method, that provided a heat flux as high as 200 Btu/sq ft sec ( approx. 234 W/sq cm) on the surface of a specimen, was performed. The experiment utilized an arc-lamp facility (60-kW radiant power output) to provide a uniform heat flux to a test specimen. For safety reasons, helium gas was used as the transpirant in the experiments. The specimens were 1.9-cm diameter sintered, powdered-stainless-steel tubes of various porosities and a 2.54cm square tube with perforated multi-layered walls. A 15-cm portion of each specimen was heated. The cooling effectivenes and efficiencies by transpiration for each specimen were obtained using the experimental results. During the testing, various test specimens displayed a choking phenomenon in which the transpirant flow was limited as the heat flux was increased. The paper includes a preliminary analysis of the transpiration cooling mechanism and a scaling conversion study that translates the results from helium tests into the case when a hydrogen medium is used.

Choi, Sang H.; Scotti, Stephen J.; Song, Kyo D.; Ries,Heidi

1997-01-01

95

Photosynthesis and Transpiration of Monterey Pine Seedlings as a Function of Soil Water Suction and Soil Temperature  

PubMed Central

Rates of photosynthesis, respiration, and transpiration of Monterey pine (Pinus radiata D. Don) were measured under controlled conditions of soil water suction and soil temperature. Air temperature, relative humidity, light intensity, and air movement were maintained constant. Rates of net photosynthesis, respiration, and transpiration decreased with increasing soil water suction. The decrease in the rates of net photosynthesis and transpiration as a function of the soil temperature at low soil water suctions may be attributed to changes in the viscosity of water. At soil water suctions larger than 0.70 bars rates of transpiration and net photosynthesis may be affected in the same proportion by changes in stomatal apertures. Images

Babalola, O.; Boersma, L.; Youngberg, C. T.

1968-01-01

96

Measures of Thermal Transpiration Flow  

NASA Astrophysics Data System (ADS)

Thermal transpiration is the macroscopic movement of gas-particles induced by a temperature gradient. The gas-particles move from the lower to the higher temperature zone. The main aim of the present work is to measure experimentally the flow created by thermal transpiration in a tube heated at its outlet. The experimental system is composed by a circular cross section micro-tube and two reservoirs settled respectively at the inlet and outlet of the capillary. The reservoirs are coupled to two high-speed response time capacitance diaphragm gauges which monitor the pressure variation in time. By monitoring the pressure variation in time is possible to measure the macroscopic movement of gas-particles along the tube: by thermal transpiration gas-particles move from the cold to the hot region of the tube increasing the hot-side reservoir absolute pressure; while a drop of pressure is registered in the cold-side reservoir. The experiments are conducted for three different gases, Argon, Helium and Nitrogen, in a pressure range from 0.1 to 10 torr and for three different temperature differences: ?T=30,,0,,0 degrees. The gas rarefaction conditions go from transitional to slip regime.

Rojas, Marcos; Graur, Irina; Perrier, Pierre

2010-11-01

97

A hierarchical analysis of the interactive effects of elevated CO2 and water availability on the nitrogen and transpiration productivities of velvet mesquite seedlings.  

PubMed

In this study we apply new extensions of classical growth analysis to assess the interactive effects of elevated CO2 and differences in water availability on the leaf-nitrogen and transpiration productivities of velvet mesquite (Prosopis velutina Woot.) seedlings. The models relate transpiration productivity (biomass gained per mass of water transpired per day) and leaf-nitrogen productivity (biomass gain per unit leaf N per day) to whole-plant relative growth rate (RGR) and to each other, allowing a comprehensive hierarchical analysis of how physiological and morphological responses to the treatments interact with each other to affect plant growth. Elevated CO2 led to highly significant increases in N and transpiration productivities but reduced leaf N per unit leaf area and transpiration per unit leaf area, resulting in no net effect of CO2 on the RGR of seedlings. In contrast, higher water availability led to an increase in leaf-tissue thickness or density without affecting leaf N concentration, resulting in a higher leaf N per unit leaf area and consequently a higher assimilatory capacity per unit leaf area. The net effect was a marginal increase in seedling RGR. Perhaps most important from an ecological perspective was a 41% reduction in whole-plant water use due to elevated CO2. These results demonstrate that even in the absence of CO2 effects on integrative measures of plant growth such as RGR, highly significant effects may be observed at the physiological and morphological level that effectively cancel each other out. The quantitative framework presented here enables some of these tradeoffs to be identified and related directly to each other and to plant growth. PMID:15322897

Peterson, Andrew G; Neofotis, Peter G

2004-12-01

98

Effects of Light, Carbon Dioxide, and Temperature on Photosynthesis, Oxygen Inhibition of Photosynthesis, and Transpiration in Solanum tuberosum1  

PubMed Central

Individual leaves of potato (Solanum tuberosum L. W729R), a C3 plant, were subjected to various irradiances (400-700 nm), CO2 levels, and temperatures in a controlled-environment chamber. As irradiance increased, stomatal and mesophyll resistance exerted a strong and some-what paralleled regulation of photosynthesis as both showed a similar decrease reaching a minimum at about 85 neinsteins·cm?2·sec?1 (about ½ of full sunlight). Also, there was a proportional hyperbolic increase in transpiration and photosynthesis with increasing irradiance up to 85 neinsteins·cm?2·sec?1. These results contrast with many C3 plants that have a near full opening of stomata at much less light than is required for saturation of photosynthesis. Inhibition of photosynthesis by 21% O2 was nearly overcome by a 2-fold increase in atmospheric levels of CO2 (about 1,200 ng·cm?3). Photosynthesis at 25 C, high irradiance, 2.5% O2 and atmospheric levels of CO2 was about 80% of the CO2-saturated rate, suggesting that CO2 can be rate-limiting even without O2 inhibition of photosynthesis. With increasing CO2 concentration, mesophyll resistance decreased slightly while stomatal resistance increased markedly above 550 ng·cm?3 which resulted in a significant reduction in transpiration. Although potato is a very productive C3 crop, there is substantial O2 inhibition of photosynthesis. The level of O2 inhibition was maximum around 25 C but the percentage inhibition of photosynthesis by O2 increased steadily from 38% at 16 C to 56% at 36 C. Photosynthesis and transpiration showed broad temperature optima (16-25 C). At higher temperatures, both the increased percentage inhibition of photosynthesis by O2 and the increased stomatal resistance limit photosynthesis, while increased stomatal resistance limits transpiration. Water use efficiency, when considered at a constant vapor pressure gradient, increased with increasing irradiance, CO2 concentration, and temperature.

Ku, Sun-Ben; Edwards, Gerald E.; Tanner, Champ B.

1977-01-01

99

Comparison of photosynthesis, transpiration, and water use efficiency in two desert shrubs  

NASA Astrophysics Data System (ADS)

Photosynthesis and transpiration are the most important physiological activities for plants. They are closely related not only to photosynthesis active radiation (PAR), air temperature (Ta), relative humility (RH) and ambient CO2 concentration, but also to plant stomatal conductance and intercellular CO2 concentration. Their relationship can be analyzed through statistic methods to indicate plant eco-physiological ability bearing to environment. By means of measuring the photosynthesis of Haloxylon ammodendron and Reaumuria soongorica in the Sangonghe River valley we have dealt with similarities and differences of two species. Results show that net photosynthesis rate of Reaumuria soongorica is slight higher than Haloxylon ammodendron, but water use efficiency of Haloxylon ammodendron is evidently higher than Reaumuria soongorica. It suggests that Haloxylon ammodendron has strong bearing ability to drought in natural habitat.

Wei, Ruyi; Pan, Xiaoling

2003-07-01

100

Sap velocity and canopy transpiration in a sweetgum stand exposed to free-air CO 2 enrichment (FACE)  

Microsoft Academic Search

Summary • Canopy transpiration rates, as a major component of forest hydrologic budgets, are reported for 12-yr-old sweetgum ( Liquidambar styraciflua ) trees growing in a free-air CO 2 enrichment (FACE) study in eastern Tennessee, USA. • The compensated heat-pulse technique was used to measure rates of sap velocity, and stand transpiration was estimated as a function of measured sap

Stan D. Wullschleger; Richard J. Norby

101

Transpiration Cooling Of Hypersonic Blunt Body  

NASA Technical Reports Server (NTRS)

Results on analytical approximation and numerical simulation compared. Report presents theoretical study of degree to which transpiration blocks heating of blunt, axisymmetric body by use of injected air. Transpiration cooling proposed to reduce operating temperatures on nose cones of proposed hypersonic aerospace vehicles. Analyses important in design of thermal protection for such vehicles.

Henline, William D.

1991-01-01

102

Towards modeling hydrodynamic stress limitations on transpiration  

NASA Astrophysics Data System (ADS)

Evapotranspiration is one of the major forcing functions of Earth's climate, providing the link for the soil-plant-water continuum. Current models for transpiration assume a coupling between stomatal conductance and soil moisture through empirical relationships that do not resolve the hydrodynamic process of water movement from the soil to the leaves. This approach does not take advantage of recent advances in our understanding of water flow and storage in the trees, or of tree and canopy structure. It has been suggested that stomata respond to water potential in the leaf and branch, and that this hydrodynamic response is a mechanism for hydraulic limitation of stomatal conductance. Hydraulic limitations in forest ecosystems are common and are known to control transpiration when the soil is drying or when vapor pressure deficit (VPD) is very large. Hydraulic limitation can also impact stomatal apertures under conditions of adequate soil moisture and lower evaporative demand. Hydrodynamic stresses at the tree level act at several time scales, including the fast, minute-hour scale. These dynamics are faster than the time scales of hours to days at which drying soil will affect stomata conductance. The lack of representation of the tree-hydrodynamic process should therefore lead to atypical intra-daily patterns of error in results of current models. We use a large-scale comparison between observations and land-surface models to characterize the patterns of intra-daily error in simulated water flux. Through the use of the North American Carbon Program (NACP) dataset, more than 10 years of water flux data for 35 Fluxnet sites in the US and Canada have been analyzed. The diurnal error for each of the 24 models represented in this dataset allows the models to be categorized and evaluated on their ability to accurately predict the fast temporal dynamics of transpiration in different ecosystems and atmospheric forcing. Among well calibrated models, two general error patterns prevail: (1) a daytime underestimation followed by nighttime overestimation of latent heat exchange; and (2) an underestimation during the morning and an afternoon overestimation. Although model error patterns are site specific, there are models that are more likely to favor one pattern above the other based on the model's sensitivity to VPD and soil moisture. The second error pattern occurs more frequently in sites where non-limiting soil moisture conditions exist. We hypothesize that the afternoon overestimation of transpiration in these scenarios can be explained by the models' lack of a mechanism to handle midday stomata closure due to hydrodynamic stresses. We introduce FETCH - a tree hydrodynamic model that can resolve the fast dynamics of stomatal conductance. We propose that coupling FETCH to other land-surface models would reduce intra-daily errors and improve the representation of canopy structure in atmospheric and hydrologic simulations.

Matheny, A. M.; Bohrer, G.; Ivanov, V. Y.; Stoy, P. C.

2011-12-01

103

Reduced atmospheric pressure in Radish: Alteration of NCER and transpiration at decreased oxygen partial pressures  

NASA Astrophysics Data System (ADS)

Fundamental to the future of space exploration is the development of advanced life support systems capable of maintaining crews for significant periods without re-supply from Earth. Significant research is focused on the development of bioregenerative life support systems to be used in conjunction with the current physico-chemical methods. These bioregenerative life support systems harness natural ecosystem processes and employ plant photosynthesis and transpiration to produce food, oxygen and regenerate water while consuming carbon dioxide. The forthcoming exploration of the Moon and Mars has prompted interest into the effects of hypobaria on plant development. Reduced atmospheric pressures will lessen the pressure gradient between the structure and the local environment thereby decreasing gas leakage and possibly the structural mass of the plant growth facility. In order to establish the optimal specifications for reduced pressure plant growth structures it is essential to determine the atmospheric pressure limits required for conventional plant development and growth. Due to its physiological importance, oxygen will compose a significant portion of these minimal environments. The objective of this study was to test the hypothesis that reduced atmospheric pressure and decreased oxygen partial pressures had no effect on radish productivity. Radishes (Raphanus sativa L. cv. Cherry Bomb II) were grown from seed in the University of Guelph's Hypobaric Plant Growth Chambers for a period of 21 days. Treatments included total pressures of 10, 33, 66 and 96 kPa and oxygen partial pressures of 2, 7, 14 and 20 kPa. Experiments demonstrated that reduced partial pressures of oxygen had a greater effect on radish growth than hypobaria. Results showed a reduction in net carbon exchange rate and transpiration with decreasing oxygen partial pressures leading to diminished productivity. Keywords: hypobaric, radish, oxygen partial pressure, variable pressure chamber, bioregenerative life support

Wehkamp, Cara Ann; Stasiak, Michael; Wheeler, Raymond; Dixon, Mike

104

Comparison of photosynthesis, transpiration, and water use efficiency in two desert shrubs  

Microsoft Academic Search

Photosynthesis and transpiration are the most important physiological activities for plants. They are closely related not only to photosynthesis active radiation (PAR), air temperature (Ta), relative humility (RH) and ambient CO2 concentration, but also to plant stomatal conductance and intercellular CO2 concentration. Their relationship can be analyzed through statistic methods to indicate plant eco-physiological ability bearing to environment. By means

Ruyi Wei; Xiaoling Pan

2003-01-01

105

PILOT-PLANT STUDIES OF SLOW-RATE FILTRATION  

EPA Science Inventory

Alternatives to conventional coagulation water filtration plants (those that utilize coagulation, flocculation, sedimentation and filtration) may be appropriate for some small water utilities. One such alternative is slow rate filtration. This paper describes pilot plant studies ...

106

Factors affecting transpiration of Pinus tabulaeformis in a semi-arid region of the Loess Plateau  

Microsoft Academic Search

The effects of soil water and meteorological factors affecting transpiration of Pinus tabulaeformis were studied under different levels of soil water content to offer a scientific basis for increasing efforts in afforestation\\u000a survival and management of soil water in forested land. Under artificial control methods for soil water and potting experiments,\\u000a the transpiration rate (T\\u000a r) of P. tabulaeformis and

Weiqiang Zhang; Yunqi Wang; Kangning He; Yi Zhou; Xianhua Gan

2008-01-01

107

Effects of air current speed on gas exchange in plant leaves and plant canopies  

NASA Astrophysics Data System (ADS)

To obtain basic data on adequate air circulation to enhance plant growth in a closed plant culture system in a controlled ecological life support system (CELSS), an investigation was made of the effects of the air current speed ranging from 0.01 to 1.0 m s-1 on photosynthesis and transpiration in sweetpotato leaves and photosynthesis in tomato seedlings canopies. The gas exchange rates in leaves and canopies were determined by using a chamber method with an infrared gas analyzer. The net photosynthetic rate and the transpiration rate increased significantly as the air current speeds increased from 0.01 to 0.2 m s-1. The transpiration rate increased gradually at air current speeds ranging from 0.2 to 1.0 m s-1 while the net photosynthetic rate was almost constant at air current speeds ranging from 0.5 to 1.0 m s-1. The increase in the net photosynthetic and transpiration rates were strongly dependent on decreased boundary-layer resistances against gas diffusion. The net photosynthetic rate of the plant canopy was doubled by an increased air current speed from 0.1 to 1.0 m s-1 above the plant canopy. The results demonstrate the importance of air movement around plants for enhancing the gas exchange in the leaf, especially in plant canopies in the CELSS.

Kitaya, Y.; Tsuruyama, J.; Shibuya, T.; Yoshida, M.; Kiyota, M.

108

Transpiration Regulation of silver firs during and after severe droughts in relation to soil properties  

NASA Astrophysics Data System (ADS)

Silver fir is declining and dying in the Mediterranean area, at its southern margin where climate is expected to become warmer and drier. At regional scale, silver fir death seems to be located on dry areas while it depends on soil water availability at forest stand scale. To understand silver firs vulnerability to drought, factors involved in their transpiration regulation were studied. An experiment was carried out on Mont Ventoux (in Provence region in south of France) which is a karstic area. Soil properties were characterised by electric resistivity tomography for estimating soil water storage capacity through the determination of soil depth and stones content. Transpiration, predawn leaf water potential dynamic and crown surface temperature were measured on trees during three years. Vulnerability curves to embolism of coarse roots and branches were established. Finally, tree growth rate history was analysed using tree ring width analysis. The experiment covered three very different climatic years. 2008 was a wet year, whereas a severe drought occurred in summer 2009 and in less extent in 2010. Soils were well watered during winters thanks to exceptional snow falls. In the context of the experiment, silver firs strongly regulate their transpiration. Transpiration/potential transpiration ratio is mostly far below 1. The decrease in transpiration rate during drying periods were the quickest on soil having small and large water storage capacity whereas on the intermediate cases, the decrease was more gradual. Moreover, the water stress intensity, derived from predawn leaf water potential, was the largest on soil having large water storage capacity. After the 2009 severe drought, transpiration rate remains much low after fall rainfalls. The transpiration drop persisted after the winter while soils were well watered. Sap flow radial distributions have suggested that the deeps roots were not reactivated after the drought. Tring ring width analysis showed that the impact of a severe drought as that of 1976 may impact the tree physiology over very long periods (>10 years). The aboveground/belowground development during the juvenile period appeared as a key to understand the tree regulation to water stress. Long term regulation mechanisms based on carbon availability allocation should be accounted for to represent the transpiration regulation. Our observations have shown that transpiration modelling schemes, based on energy balance and stomatal regulation only, are not appropriate to represent silver transpiration rate during and after drought. Some additional regulation processes have been proposed.

Chanzy, A.; Nourtier, M.

2011-12-01

109

Transpiring wall supercritical water oxidation reactor salt deposition studies  

SciTech Connect

Sandia National Laboratories has teamed with Foster Wheeler Development Corp. and GenCorp, Aerojet to develop and evaluate a new supercritical water oxidation reactor design using a transpiring wall liner. In the design, pure water is injected through small pores in the liner wall to form a protective boundary layer that inhibits salt deposition and corrosion, effects that interfere with system performance. The concept was tested at Sandia on a laboratory-scale transpiring wall reactor that is a 1/4 scale model of a prototype plant being designed for the Army to destroy colored smoke and dye at Pine Bluff Arsenal in Arkansas. During the tests, a single-phase pressurized solution of sodium sulfate (Na{sub 2}SO{sub 4}) was heated to supercritical conditions, causing the salt to precipitate out as a fine solid. On-line diagnostics and post-test observation allowed us to characterize reactor performance at different flow and temperature conditions. Tests with and without the protective boundary layer demonstrated that wall transpiration provides significant protection against salt deposition. Confirmation tests were run with one of the dyes that will be processed in the Pine Bluff facility. The experimental techniques, results, and conclusions are discussed.

Haroldsen, B.L.; Mills, B.E.; Ariizumi, D.Y.; Brown, B.G. [and others

1996-09-01

110

Measurement of sap flow in plant stems  

Microsoft Academic Search

Transpiration rates for whole plants, individual branches or tillers can be determined by techniques which measure the rate at which sap ascends stems. All of these methods use heat as a tracer for sap movement, but they are fundamentally different in their operating principles. Two methods commonly employed, the stem heat balance and trunk sector heat balance methods, use the

D. M. Smith; S. J. Allen

1996-01-01

111

Transpiration from forest dwelling and woodland Mygalomorphae (Araneae)  

NASA Astrophysics Data System (ADS)

Rates of water loss in dry air at room temperature (21±2°C) have been measured from seven species of forest-dwelling mygalomorph spiders. They range from 0.260% body wt h-1 in the tube-dwelling trapdoor spider Dyarcyops sp. (from the humid coastal regions of eastern Australia) to 0.030% wt h-1 in Brachypelma smithi (from drier environments in Mexico). There is a tendency for rates of transpiration to be related to the humidities of the spiders' normal environments and micro-habitats.

Cloudsley-Thompson, J. L.; Constantinou, C.

1983-03-01

112

PLANT CULTURAL SYSTEM FOR MONITORING EVAPOTRANSPIRATION AND PHYSIOLOGICAL RESPONSES UNDER FIELD CONDITIONS  

EPA Science Inventory

A plant culture system incorporating the water-table root-screen method for controlling plant water status was adapted for use in open-top field exposure chambers for studying the effects of drought stress on physiological responses. The daily transpiration rates of the plants we...

113

Effects of plant gross morphology on predator consumption rates.  

PubMed

We find that spatial structure, and in particular, differences in gross plant morphology, can alter the consumption rates of generalist insect predators. We compared Asian lady beetle, Harmonia axyridis Pallas, and green lacewing larvae, Chrysoperla carnea Stephens, consumption rates of pea aphids, Acyrthosiphon pisum Harris, in homogeneous environments (petri dishes) and heterogeneous environments (whole plants). Spatial complexity is often described as reducing predator success, and we did find that predators consumed significantly more aphids on leaf tissue in petri dishes than on whole plants with the same surface area. However, subtle differences in plant morphology may have more unexpected effects. A comparison of consumption rates on four different isogenic pea morphs (Pisum sativum L.) controlled for surface area indicated that both lady beetles and lacewings were more successful on morphologies that were highly branched. We speculate that predators move more easily over highly branched plants because there are more edges to grasp. PMID:22732608

Reynolds, Paula G; Cuddington, Kim

2012-06-01

114

Separating foliar physiology from morphology reveals the relative roles of vertically structured transpiration factors within red maple crowns and limitations of larger scale models  

PubMed Central

A spatially explicit mechanistic model, MAESTRA, was used to separate key parameters affecting transpiration to provide insights into the most influential parameters for accurate predictions of within-crown and within-canopy transpiration. Once validated among Acer rubrum L. genotypes, model responses to different parameterization scenarios were scaled up to stand transpiration (expressed per unit leaf area) to assess how transpiration might be affected by the spatial distribution of foliage properties. For example, when physiological differences were accounted for, differences in leaf width among A. rubrum L. genotypes resulted in a 25% difference in transpiration. An in silico within-canopy sensitivity analysis was conducted over the range of genotype parameter variation observed and under different climate forcing conditions. The analysis revealed that seven of 16 leaf traits had a ?5% impact on transpiration predictions. Under sparse foliage conditions, comparisons of the present findings with previous studies were in agreement that parameters such as the maximum Rubisco-limited rate of photosynthesis can explain ?20% of the variability in predicted transpiration. However, the spatial analysis shows how such parameters can decrease or change in importance below the uppermost canopy layer. Alternatively, model sensitivity to leaf width and minimum stomatal conductance was continuous along a vertical canopy depth profile. Foremost, transpiration sensitivity to an observed range of morphological and physiological parameters is examined and the spatial sensitivity of transpiration model predictions to vertical variations in microclimate and foliage density is identified to reduce the uncertainty of current transpiration predictions.

Bauerle, William L.; Bowden, Joseph D.

2011-01-01

115

Plant respirometer enables high resolution of oxygen consumption rates  

NASA Technical Reports Server (NTRS)

Plant respirometer permits high resolution of relatively small changes in the rate of oxygen consumed by plant organisms undergoing oxidative metabolism in a nonphotosynthetic state. The two stage supply and monitoring system operates by a differential pressure transducer and provides a calibrated output by digital or analog signals.

Foster, D. L.

1966-01-01

116

A Remote Sensing Study of the NDVI– T s Relationship and the Transpiration from Sparse Vegetation in the Sahel Based on High-Resolution Satellite Data  

Microsoft Academic Search

This article proposes a new approach for estimation of the transpiration rate in sparse canopies. The method relies on a combination of techniques; some of which having a successful background of solid experimental and theoretical justification, while others having only recently been introduced as promising tools for the extraction of environmental information from satellite data. The transpiration rate (?Ev) is

E. Boegh; H. Soegaard; N. Hanan; P. Kabat; L. Lesch

1999-01-01

117

Experimental studies of transpiration cooling with shock interaction in hypersonic flow, part B  

NASA Technical Reports Server (NTRS)

This report describes the result of experimental studies conducted to examine the effects of the impingement of an oblique shock on the flowfield and surface characteristics of a transpiration-cooled wall in turbulent hypersonic flow. The principal objective of this work was to determine whether the interaction between the oblique shock and the low-momentum region of the transpiration-cooled boundary layer created a highly distorted flowfield and resulted in a significant reduction in the cooling effectiveness of the transpiration-cooled surface. As a part of this program, we also sought to determine the effectiveness of transpiration cooling with nitrogen and helium injectants for a wide range of blowing rates under constant-pressure conditions in the absence of shock interaction. This experimental program was conducted in the Calspan 48-Inch Shock Tunnel at nominal Mach numbers of 6 and 8, for a Reynolds number of 7.5 x 10(exp 6). For these test conditions, we obtained fully turbulent boundary layers upstream of the interaction regions over the transpiration-cooled segment of the flat plate. The experimental program was conducted in two phases. In the first phase, we examined the effects of mass-addition level and coolant properties on the cooling effectiveness of transpiration-cooled surfaces in the absence of shock interaction. In the second phase of the program, we examined the effects of oblique shock impingement on the flowfield and surface characteristics of a transpiration-cooled surface. The studies were conducted for a range of shock strengths with nitrogen and helium coolants to examine how the distribution of heat transfer and pressure and the characteristics of the flowfield in the interaction region varied with shock strength and the level of mass addition from the transpiration-cooled section of the model. The effects of the distribution of the blowing rate along the interaction regions were also examined for a range of blowing rates through the transpiration-cooled panels. The regions of shockwave/boundary layer interaction examined in these studies were induced by oblique shocks generated with a sharp, flat plate, inclined to the freestream at angles of 5 degrees, 7.5 degrees, and 10 degrees. It was found that, in the absence of an incident shock, transpiration cooling was a very effective method for reducing both the heat transfer and the skin friction loads on the surface. The helium coolant was found to be significantly more effective than nitrogen, because of its low molecular weight and high specific heat. The studies of shock-wave/transpiration-cooled surface interaction demonstrated that the interaction region between the incident shock and the low-momentum transpiration-cooled boundary layer did not result in a significant increase in the size of attached or separated interaction regions, and did not result in significant flowfield distortions above the interaction region. The increase in heating downstream of the shock-impingement point could easily be reduced to the values without shock impingement by a relatively small increase in the transpiration cooling in this region. Surprisingly, this increase in cooling rate did not result in a significant increase in size of the region ahead of the incident shock or create a significantly enlarged interaction region with a resultant increase in the distortion level in the inviscid flow. Thus, transpiration cooling appears to be a very effective technique to cool the internal surfaces of scramjet engines, where shocks in the engine would induce large local increases in wall heating and create viscous/inviscid interactions that could significantly disturb the smooth flow through the combustor. However, if hydrogen is used as the coolant, burning upstream of shock impingement might result in localized hot spots. Clearly, further research is needed in this area.

Holden, Michael S.

1994-01-01

118

Application of crop gas exchange and transpiration data obtained with CEEF to global change problem  

NASA Astrophysics Data System (ADS)

In order to predict carbon sequestration of vegetation with the future rise in atmospheric CO 2 concentration, [CO 2] and temperature, long term effects of high [CO 2] and high temperature on responses of both photosynthesis and transpiration of plants as a whole community to environmental parameters need to be elucidated. Especially in the last decade, many studies on photosynthetic acclimation to elevated [CO 2] at gene, cell, tissue or leaf level for only vegetative growth phase ( i.e. before formation of reproductive organs) have been conducted all over the world. However, CO 2 acclimation studies at population or community level for a whole growing season are thus far very rare. Data obtained from repeatable experiments at population or community level for a whole growing season are necessary for modeling carbon sequestration of a plant community. On the other hand, in order to stabilize material circulation in the artificial ecological system of Closed Ecology Experiment Facilities (CEEF), it is necessary to predict material exchange rates in the biological systems. In particular, the material exchange rate in higher plant systems is highly variable during growth periods and there is a strong dependence on environmental conditions. For this reason, dependencies of both CO 2 exchange rate and transpiration rate of three rice populations grown from seed under differing conditions of [CO 2] and day/night air temperature (350 ?L CO 2 L -1, 24/17°C (population A); 700 ?L CO 2 L -1, 24/17°C (population B) and 700 ?L CO 2 L -1, 26/19°C (population C)) upon PPFD, leaf temperature and [CO 2] were investigated every two weeks during whole growing season. Growth of leaf lamina, leaf sheath, panicle and root was also compared. From this experiment, it was elucidated that acclimation of instantaneous photosynthetic response of rice population to [CO 2] occurs in vegetative phase through changes in ratio of leaf area to whole plant dry weight, LAR. But, in reproductive growth phase ( i.e. after initiation of panicle formation), the difference between photosynthetic response to [CO 2] of population A and that of population B decreased. Although LAR of population C was almost always less than that of population A, there was no difference between the photosynthetic response to [CO 2] of population A at 24°C and that of population C at 26°C for its whole growth period. These results are useful to make a model to predict carbon sequestration of rice community, which is an important type of vegetation especially in Asia in future global environmental change.

Tako, Y.; Arai, R.; Otsubo, K.; Nitta, K.

119

Application of crop gas exchange and transpiration data obtained with CEEF to global change problem.  

PubMed

In order to predict carbon sequestration of vegetation with the future rise in atmospheric CO2 concentration, [CO2] and temperature, long term effects of high [CO2] and high temperature on responses of both photosynthesis and transpiration of plants as a whole community to environmental parameters need to be elucidated. Especially in the last decade, many studies on photosynthetic acclimation to elevated [CO2] at gene, cell, tissue or leaf level for only vegetative growth phase (i.e. before formation of reproductive organs) have been conducted all over the world. However, CO2 acclimation studies at population or community level for a whole growing season are thus far very rare. Data obtained from repeatable experiments at population or community level for a whole growing season are necessary for modeling carbon sequestration of a plant community. On the other hand, in order to stabilize material circulation in the artificial ecological system of Closed Ecology Experiment Facilities (CEEF), it is necessary to predict material exchange rates in the biological systems. In particular, the material exchange rate in higher plant systems is highly variable during growth periods and there is a strong dependence on environmental conditions. For this reason, dependencies of both CO2 exchange rate and transpiration rate of three rice populations grown from seed under differing conditions of [CO2] and day/night air temperature (350 microL CO2 L-1, 24/17 degrees C (population A); 700 microL CO2 L-1, 24/17 degrees C (population B) and 700 microL CO2 L-1, 26/19 degrees C (population C)) upon PPFD, leaf temperature and [CO2] were investigated every two weeks during whole growing season. Growth of leaf lamina, leaf sheath, panicle and root was also compared. From this experiment, it was elucidated that acclimation of instantaneous photosynthetic response of rice population to [CO2] occurs in vegetative phase through changes in ratio of leaf area to whole plant dry weight, LAR. But, in reproductive growth phase (i.e. after initiation of panicle formation), the difference between photosynthetic response to [CO2] of population A and that of population B decreased. Although LAR of population C was almost always less than that of population A, there was no difference between the photosynthetic response to [CO2] of population A at 24 degrees C and that of population C at 26 degrees C for its whole growth period. These results are useful to make a model to predict carbon sequestration of rice community, which is an important type of vegetation especially in Asia in future global environmental change. PMID:11695434

Tako, Y; Arai, R; Otsubo, K; Nitta, K

2001-01-01

120

Responses of canopy transpiration and canopy conductance of peach (Prunus persica) trees to alternate partial root zone drip irrigation  

NASA Astrophysics Data System (ADS)

We investigated canopy transpiration and canopy conductance of peach trees under three irrigation patterns: fixed 1/2 partial root zone drip irrigation (FPRDI), alternate 1/2 partial root zone drip irrigation (APRDI) and full root zone drip irrigation (FDI). Canopy transpiration was measured using heat pulse sensors, and canopy conductance was calculated using the Jarvis model and the inversion of the Penman-Monteith equation. Results showed that the transpiration rate and canopy conductance in FPRDI and APRDI were smaller than those in FDI. More significantly, the total irrigation amount was greatly reduced, by 34.7% and 39.6%, respectively for APRDI and FPRDI in the PRDI (partial root zone drip irrigation) treatment period. The daily transpiration was linearly related to the reference evapotranspiration in the three treatments, but daily transpiration of FDI is more than that of APRDI and FPRDI under the same evaporation demand, suggesting a restriction of transpiration water loss in the APRDI and FPRDI trees. FDI needed a higher soil water content to carry the same amount of transpiration as the APRDI and FPRDI trees, suggesting the hydraulic conductance of roots of APRDI and FPRDI trees was enhanced, and the roots had a greater water uptake than in FDI when the average soil water content in the root zone was the same. By a comparison between the transpiration rates predicted by the Penman-Monteith equation and the measured canopy transpiration rates for 60 days during the experimental period, an excellent correlation along the 1:1 line was found for all the treatments (R2 > 0.80), proving the reliability of the methodology.

Gong, Daozhi; Kang, Shaozhong; Zhang, Jianhua

2005-08-01

121

Transpiration Driven Hydrologic Transport in vegetated shallow water environments: Implications on Diel and Seasonal Soil Biogeochemical Processes and System Management  

NASA Astrophysics Data System (ADS)

Hydrology arguably plays the most important role in biogeochemical cycling of mercury in wetlands and other shallow aquatic systems. CFSTR, PFR and non-ideal reactor models are oftentimes currently used to hydrologically assess these systems and to account for the fate, transport and cycling of constituents of concern (COC) with systems assumed to be non-leaky and with diffusion dominating soil transport. Yet a number of results in the literature imply transpiration drives soil transport: transpiration into the root zone is in the range of 50 - 75% of ET seasonally; gaseous emissions from aquatic systems show a diel pattern that tracks diel ET patterns; in long detention time aquatic systems ET is the largest sink for applied surface waters; and non-reactive tracers when applied to surface waters can find themselves in the root zone and within plants. All these findings strongly suggest transpiration driven infiltration into the root zone, is a significant hydrologic pathway for constituents and is an important transport mechanism. This paper examines the annual water budget for four shallow aquatic land uses in the Yolo Bypass, California: rice, wild rice, fallowed fields and wetlands. Results indicate that differences in hydrology between the fields, particularly the temporal nature of transpiration, play a significant role in mercury transformations and transport. During the irrigation period, fallowed fields discharged 6 cm of surface water (15% applied water), rice fields 31 - 43 cm (27 - 31% applied water), and wild rice fields 16 - 39 cm (15 - 31% applied water). Evapotranspiration rates were in the range of 120 - 130 cm/y for all land uses (i.e. rice, wild rice, fallowed fields and seasonal wetlands) except for the permanent wetland which was about 1/3 higher at about 170 cm/y. During the summer, approximately 50% of the applied surface water was drawn into the root zone to meet transpiration demands. Based upon results from our water budget and utilizing modified Peclet No. calculations, we quantified the relative importance of upward diffusion from the sediments and downward advection from transpiration as hydrologic transport mechanisms in the root zone. Transpiration driven infiltration moves water past the diffusive zone within 1 - 2 days in this system during the summer months. With the waning seasons, evapotranspiration diminishes until by winter diffusion dominates throughout the entire root zone. This model has great implications on the analyses of soil biogeochemical process in the root zone of shallow aquatic systems. Downward advection is a major transport mechanism into the root zone of shallow flooded aquatic systems and provides an important physical mechanism that drives variability in the seasonal and diel storage; release and cycling of COCs; and the creation of both a physical and chemical barrierd to upward diffusion of soil-borne COCs into the water column. Models that do not account for root zone interactions may not be able to capture diel and seasonal differences. Moreover, these interactions may lead to unanticipated environmental consequences as a result of cultural practices.

Bachand, P.; Bachand, S. M.; Fleck, J.; Anderson, F.

2011-12-01

122

Ash, Carbon Isotope Discrimination, and Silicon as Estimators of Transpiration Efficiency in Crested Wheatgrass  

Microsoft Academic Search

Breeding and selection for higher transpiration efficiency (W) has been hampered by tedious and costly methodology. Rapid and less costly methods are needed for screening W in plant improvement programmes. We report the relationship of ash, silicon (Si) concentration, and Si uptake to W in crested wheatgrass (Agropyron desertorum (Fischer ex Link) Schultes), an important C3 range grass in western

H. F. Mayland; D. A. Johnson; K. H. Asay; A USDA-ARS; B USDA-ARS

123

Make Your Own Transpiring Tree  

ERIC Educational Resources Information Center

In this paper we present a simple set-up that illustrates the mechanism of sap ascent in plants and demonstrates that it can easily draw water up to heights of a few meters. The set-up consists of a tube with the lower end submerged in water and the upper one connected to a filter supported by a standard filter-holder. The evaporation of water…

Martinez Vilalta, Jordi; Sauret, Miquel; Duro, Alicia; Pinol, Josep

2003-01-01

124

Dose rate outside cryostat of the SEAFP-2 fusion plant  

Microsoft Academic Search

The results of biological dose rate calculations for different locations in the vicinity of the concrete shield wall of the cryostat pit of the SEAFP-2 fusion plant are given in this paper. The plant model assessed considers low-activation martensitic steel for first wall and blanket, Li17Pb83 as breeder\\/multiplier material and water as coolant. For many analyses in the frame of

D. G Cepraga; G Cambi; M Frisoni; L Di Pace

2001-01-01

125

Transpiration characteristics of a rubber plantation in central Cambodia.  

PubMed

The rapid and widespread expansion of rubber plantations in Southeast Asia necessitates a greater understanding of tree physiology and the impacts of water consumption on local hydrology. Sap flow measurements were used to study the intra- and inter-annual variations in transpiration rate (Et) in a rubber stand in the low-elevation plain of central Cambodia. Mean stand sap flux density (JS) indicates that rubber trees actively transpire in the rainy season, but become inactive in the dry season. A sharp, brief drop in JS occurred simultaneously with leaf shedding in the middle of the dry season in January. Although the annual maxima of JS were approximately the same in the two study years, the maximum daily stand Et of ?2.0 mm day(-1) in 2010 increased to ?2.4 mm day(-1) in 2011. Canopy-level stomatal response was well explained by changes in solar radiation, vapor pressure deficit, soil moisture availability, leaf area, and stem diameter. Rubber trees had a relatively small potential to transpire at the beginning of the study period, compared with average diffuse-porous species. After 2 years of growth in stem diameter, transpiration potential was comparable to other species. The sensitivity of canopy conductance (gc) to atmospheric drought indicates isohydric behavior of rubber trees. Modeling also predicted a relatively small sensitivity of gc to the soil moisture deficit and a rapid decrease in gc under extreme drought conditions. However, annual observations suggest the possibility of a change in leaf characteristics with tree maturity and/or initiation of latex tapping. The estimated annual stand Et was 469 mm year(-1) in 2010, increasing to 658 mm year(-1) in 2011. Diagnostic analysis using the derived gc model showed that inter-annual change in stand Et in the rapidly growing young rubber stand was determined mainly by tree growth rate, not by differences in air and soil variables in the surrounding environment. Future research should focus on the potentially broad applicability of the relationship between Et and tree size as well as environmental factors at stands different in terms of clonal type and age. PMID:24646689

Kobayashi, Nakako; Kumagai, Tomo'omi; Miyazawa, Yoshiyuki; Matsumoto, Kazuho; Tateishi, Makiko; Lim, Tiva K; Mudd, Ryan G; Ziegler, Alan D; Giambelluca, Thomas W; Yin, Song

2014-03-01

126

Analysis of transpiration results from the RICE and PILPS workshop  

NASA Astrophysics Data System (ADS)

Results from the 14 land surface parameterization schemes involved in the PILPS-RICE Workshop are compared for a soya crop growing season (from June to September). During this period, the transpiration flux dominates the total surface evapotranspiration and observed data from HAPEX-MOBILHY are available for comparison. Results indicate that during the month of June half of the models fall within the uncertainty range of the observations. The scatter between models behaviour is explained by three major reasons: The functional dependency between soil moisture and transpiration; the initial moisture content at the beginning of the period; the vertical discretization within the soil and the extension of the root system that defines the soil water holding capacity for plants Examination of diurnal cycles of evaporation reveals that formulations based on the supply-demand concept are very sensitive to the specification of the root zone. This analysis underlines the need for more sensitivity experiments to be done with the current forcing data set and more detailed datasets to be collected in future field experiments (e.g. latent heat flux during all the growing season, root zone distribution).

Mahfouf, J.-F.; Ciret, C.; Ducharne, A.; Irannejad, P.; Noilhan, J.; Shao, Y.; Thornton, P.; Xue, Y.; Yang, Z.-L.

1996-06-01

127

PATHWAYS, MECHANISMS, AND RATES OF POLYPLOID FORMATION IN FLOWERING PLANTS  

Microsoft Academic Search

Polyploidy is widely acknowledged as a major mechanism of adaptation and speciation in plants. The stages in polyploid evolution include frequent fertility bottlenecks and infrequent events such as gametic nonreduction and interspecific hybridization, yet little is known about how these and other factors influence over- all rates of polyploid formation. Here we review the literature regarding polyploid origins, and quantify

Justin Ramsey; Douglas W. Schemske

1998-01-01

128

Improvements in plant growth rate using underwater discharge  

NASA Astrophysics Data System (ADS)

The drainage water from plant pots was irradiated by plasma and then recycled to irrigate plants for improving the growth rate by supplying nutrients to plants and inactivating the bacteria in the bed-soil. Brassica rapa var. perviridis (Chinese cabbage; Brassica campestris) plants were cultivated in pots filled with artificial soil, which included the use of chicken droppings as a fertiliser. The water was recycled once per day from a drainage water pool and added to the bed-soil in the pots. A magnetic compression type pulsed power generator was used to produce underwater discharge with repetition rate of 250 pps. The plasma irradiation times were set as 10 and 20 minutes per day over 28 days of cultivation. The experimental results showed that the growth rate increased significantly with plasma irradiation into the drainage water. The growth rate increased with the plasma irradiation time. The nitrogen concentration of the leaves increased as a result of plasma irradiation based on chlorophyll content analysis. The bacteria in the drainage water were inactivated by the plasma irradiation.

Takaki, K.; Takahata, J.; Watanabe, S.; Satta, N.; Yamada, O.; Fujio, T.; Sasaki, Y.

2013-03-01

129

Numerical analysis of thermal transpiration flows for a nano-pore aerogel membrane.  

PubMed

Thermal transpiration flows in nano-pore aero-gel membranes are investigated for the performance optimization of a Knudsen compressor. Critical elements that drive the Knudsen compressor are its thermal transpiration membranes. The membranes are based on aerogel, or on machined aerogel. In our study, aerogel is modeled as a single microflow channel. The effects of wall temperature distribution on thermal transpiration flow patterns are examined. The flow has a pumping effect, and the mass flow rates through the channel are calculated. The results show that a steady one-way flow is induced for a wide range of Knudsen numbers. The direct simulation Monte Carlo (DSMC) method, with a variable hard sphere (VHS) model and no time counter (NTC) technique, is applied to obtain numerical solutions. PMID:19908799

Heo, Joong-Sik; Hwang, Young-Kyu

2009-12-01

130

HYDROLOGICAL IMPACTS OF WOODY PLANT ENCROACHMENT IN ARID AND SEMIARID GRASSLANDS  

EPA Science Inventory

Woody plants may be able to access deeper groundwater for year-round transpiration and thus consume more water than grasses, affecting recharge, soil moisture and runoff. Amount of water available to plants from precipitation is determined in part by nfiltration rates into...

131

EFFECT, UPTAKE AND DISPOSITION OF NITROBENZENE IN SEVERAL TERRESTRIAL PLANTS  

EPA Science Inventory

Eight species of plants were exposed to nitrobenzene in a hydroponic solution. our species experienced no depression of either transpiration or photosynthetic rates, while one was rapidly killed and the other three were temporarily affected but recovered from the treatment. ptake...

132

Urban tree transpiration over turf and asphalt surfaces  

Microsoft Academic Search

We used a two-layer canopy model to study transpiration of tree species as affected by energy-balance properties of a vegetated and paved surface. During several dawn-to-dusk studies, tree transpiration, stomatal conductance, leaf temperature (Tl), and several microclimate variables, were measured over turf and an asphalt surface. Cumulative transpiration was estimated from a leaf energy-balance equation applied to a tree crown

Roger Kjelgren; Thayne Montague

1998-01-01

133

Toward an improved understanding of the role of transpiration in critical zone dynamics  

NASA Astrophysics Data System (ADS)

Evapotranspiration (ET) is an important component of the total water balance across any ecosystem. In subalpine mixed-conifer ecosystems, transpiration (T) often dominates the total water flux and therefore improved understanding of T is critical for accurate assessment of catchment water balance and for understanding of the processes that governs the complex dynamics across critical zone (CZ). The interaction between T and plant vegetation not only modulates soil water balance but also influences water transit time and hydrochemical flux - key factors in our understanding of how the CZ evolves and responds. Unlike an eddy covariance system which provides only an integrated ET flux from an ecosystem, a sap flow system can provide an estimate of the T flux from the ecosystem. By isolating T, the ecohydrological drivers of this major water loss from the CZ can be identified. Still, the species composition of mixed-conifer ecosystems vary and the drivers of T associated with each species are expected to be different. Therefore, accurate quantification of T from a mixed-conifer requires knowledge of the unique transpiration dynamics of each of the tree species. Here, we installed a sap flow system within two mixed-conifer study sites of the Jemez River Basin - Santa Catalina Mountains Critical Zone Observatory (JRB - SCM CZO). At both sites, we identified the dominant tree species and installed sap flow sensors on healthy representatives for each of those species. At the JRB CZO site, sap sensors were installed in fir (4) and spruce (4) trees; at the SCM CZO site, sap sensors were installed at white fir (4) and maple (4) and one dead tree. Meteorological data as well as soil temperature (Ts) and soil moisture (?) at multiple depths were also collected from each of the two sites. Preliminary analysis of two years of sap flux rate at JRB - SCM CZO shows that the environmental drivers of fir, spruce, and maple are different and also vary throughout the year. For JRB fir, during the snowmelt period, Ts across multiple depths was the primary control on the sap flux rate (R2 ? 0.7). During the dry and monsoon periods only net radiation (Rn) was found to be a driver of the flux rate (R2 ? 0.4). For JRB spruce, a combination of Ts across multiple depths as well as air temperature (R2 ? 0.5) were the dominant drivers of sap flux rate during the snowmelt period. During the monsoon period, Rn (R2 ? 0.4) was the dominant driver. For SCM maple, during the dry period, ? across multiple depths was the primary driver of the sap flux rate (R2 ? 0.8); the strength of the correlation with the control of ? on sap flux rate drastically dropping (R2 ? 0.2) during the monsoon period. For SCM white fir, ? across multiple depths was a weak driver of sap flux rate during the dry (R2 ? 0.1) and monsoon periods (R2 ? 0.2). This study highlights the importance of species-specific information for understanding the role of transpiration in critical zone processes. Specifically, unique environmental drivers that vary throughout the year for different vegetation types complicate the assessment of both catchment-scale water and carbon balances and for understanding of the processes that govern the complex dynamics across the CZ.

Mitra, B.; Papuga, S. A.

2012-12-01

134

Heat exchanger with transpired, highly porous fins  

DOEpatents

The heat exchanger includes a fin and tube assembly with increased heat transfer surface area positioned within a hollow chamber of a housing to provide effective heat transfer between a gas flowing within the hollow chamber and a fluid flowing in the fin and tube assembly. A fan is included to force a gas, such as air, to flow through the hollow chamber and through the fin and tube assembly. The fin and tube assembly comprises fluid conduits to direct the fluid through the heat exchanger, to prevent mixing with the gas, and to provide a heat transfer surface or pathway between the fluid and the gas. A heat transfer element is provided in the fin and tube assembly to provide extended heat transfer surfaces for the fluid conduits. The heat transfer element is corrugated to form fins between alternating ridges and grooves that define flow channels for directing the gas flow. The fins are fabricated from a thin, heat conductive material containing numerous orifices or pores for transpiring the gas out of the flow channel. The grooves are closed or only partially open so that all or substantially all of the gas is transpired through the fins so that heat is exchanged on the front and back surfaces of the fins and also within the interior of the orifices, thereby significantly increasing the available the heat transfer surface of the heat exchanger. The transpired fins also increase heat transfer effectiveness of the heat exchanger by increasing the heat transfer coefficient by disrupting boundary layer development on the fins and by establishing other beneficial gas flow patterns, all at desirable pressure drops.

Kutscher, Charles F. (Golden, CO); Gawlik, Keith (Boulder, CO)

2002-01-01

135

Multi-objective parameter estimation for simulating canopy transpiration in forested watersheds  

NASA Astrophysics Data System (ADS)

A Jarvis based [Philos. Trans. R. Soc. London, Ser. B 273 (1976) 593] model of canopy stomatal conductance was evaluated in context of its application to simulating transpiration in a conifer forest covered watershed in the Central Sierra Nevada of California, USA. Parameters influencing stomatal conductance were assigned values using Monte Carlo sampling. Model calibration was conducted by evaluating predicted latent heat fluxes against thermal remote sensing estimates of surface temperature. A fuzzy logic approach was used to select or reject simulations and form a restricted set of ensemble parameter solutions. Parameter estimates derived from the ensembles were evaluated using theory on how stomatal conductance regulates leaf water potential to prevent runaway cavitation. Canopy level parameters were found to be sufficient for predicting hydraulically consistent transpiration when soils were well watered. A rooting length parameter controlling the amount of plant available water was a sufficient addition to the parameter set to predict hydraulically consistent transpiration when soil moisture stress was occurring. Variations in maximum stomatal conductance among different hillslopes within the watershed were explained by a light threshold parameter. The results demonstrate that the Jarvis model can be reliably parameterized using thermal remote sensing data for estimating transpiration in meso-scale watersheds.

Mackay, D. Scott; Samanta, Sudeep; Nemani, Ramakrishna R.; Band, Lawrence E.

2003-06-01

136

Savanna Grassland Transpiration Fluxes After A Water Pulse Using Stable Isotope And Eddy Covariance Techniques  

NASA Astrophysics Data System (ADS)

The ratio of carbon uptake to transpiration water losses, also known as plant water use efficiency (WUE), is an important indicator of vegetation status. However the accurate measurement of WUE at the plot and/or landscape scale remains a challenge. The difficulty lies in directly quantifying transpiration losses, as typical eddy covariance systems only allow for determination of bulk evapotranspiration (ET) fluxes. Decomposing tower based measurements of ET into transpiration (T) and evaporation (E) is necessary in arid and semi-arid environments where evaporation is a non-trival component of the local water balance. We present results from a field campaign directed at quantifying landscape WUE in a grassland savanna in central Kenya. A 30mm rainfall event was was created during the long dry season, a period when all perennial grass cover had entered dormancy. Following the water input grass cover proceeded to green-up and subsequently wither. Using stable isotope techniques we partition ET by utilizing a laser based water vapor isotope analyzer mounted in concert with an eddy covariance system. These tower based measurements of evapotranspiration isotope composition are contrasted with direct measurements of leaf and soil water isotope fluxes during both the grassland green-up and dry-down period, a period of 15 days. The direct quantification of landscape transpiration, a key component in landscape WUE, provides an important indicator of the evolving status of a dynamic ecohydrologic system.

Caylor, K. K.; Good, S. P.; Soderberg, K.; King, E.

2011-12-01

137

Cyclic Variations in Nitrogen Uptake Rate of Soybean Plants 1  

PubMed Central

When NO3? is the sole nitrogen source in flowing solution culture, the net rate of nitrogen uptake by nonnodulated soybean (Glycine max L. Merr. cv Ransom) plants cycles between maxima and minima with a periodicity of oscillation that corresponds with the interval of leaf emergence. Since soybean plants accumulate similar quantities of nitrogen when either NH4+ or NO3? is the sole source in solution culture controlled at pH 6.0, an experiment was conducted to determine if the oscillations in net rate of nitrogen uptake also occur when NH4+ is the nitrogen source. During a 21-day period of vegetative development, net uptake of NH4+ was measured daily by ion chromatography as depletion of NH4+ from a replenished nutrient solution containing 1.0 millimolar NH4+. The net rate of NH4+ uptake oscillated with a periodicity that was similar to the interval of leaf emergence. Instances of negative net rates of uptake indicate that the transition between maxima and minima involved changes in influx and efflux components of net NH4+ uptake.

Henry, Leslie Tolley; Raper, C. David

1989-01-01

138

Desiccant cooling using unglazed transpired solar collectors  

SciTech Connect

The use of unglazed solar collectors for desiccant regeneration in a solid desiccant cooling cycle was investigated because these collectors are lower in cost than conventional glazed flat-plate collectors. Using computer models, the performance of a desiccant cooling ventilation cycle integrated with either unglazed transpired collectors or conventional glazed flat-plate collectors was obtained. We found that the thermal performance of the unglazed system was lower than the thermal performance of the glazed system because the unglazed system could not take advantage of the heat of adsorption released during the dehumidification process. For a 3-ton cooling system, although the area required for the unglazed collector was 69% more than that required for the glazed collector, the cost of the unglazed collector array was 44% less than the cost of the glazed collector array. The simple payback period of the unglazed system was half of the payback period of the glazed collector when compared to an equivalent gas-fired system. Although the use of unglazed transpired collectors makes economic sense, some practical considerations may limit their use in desiccant regeneration. 8 refs.

Pesaran, A.A. (National Renewable Energy Lab., Golden, CO (United States)); Wipke, K. (Stanford Univ., CA (United States))

1992-05-01

139

The Dynamics of Embolism Refilling in Abscisic Acid (ABA)-Deficient Tomato Plants  

PubMed Central

Plants are in danger of embolism formation in xylem vessels when the balance between water transport capacity and transpirational demand is compromised. To maintain this delicate balance, plants must regulate the rate of transpiration and, if necessary, restore water transport in embolized vessels. Abscisic acid (ABA) is the dominant long-distance signal responsible for plant response to stress, and it is possible that it plays a role in the embolism/refilling cycle. To test this idea, a temporal analysis of embolism and refilling dynamics, transpiration rate and starch content was performed on ABA-deficient mutant tomato plants. ABA-deficient mutants were more vulnerable to embolism formation than wild-type plants, and application of exogenous ABA had no effect on vulnerability. However, mutant plants treated with exogenous ABA had lower stomatal conductance and reduced starch content in the xylem parenchyma cells. The lower starch content could have an indirect effect on the plant’s refilling activity. The results confirm that plants with high starch content (moderately stressed mutant plants) were more likely to recover from loss of water transport capacity than plants with low starch content (mutant plants with application of exogenous ABA) or plants experiencing severe water stress. This study demonstrates that ABA most likely does not play any direct role in embolism refilling, but through the modulation of carbohydrate content, it could influence the plant’s capacity for refilling.

Secchi, Francesca; Perrone, Irene; Chitarra, Walter; Zwieniecka, Anna K.; Lovisolo, Claudio; Zwieniecki, Maciej A.

2013-01-01

140

Plant responses to atmospheric carbon dioxide enrichment: interactions with some soil and atmospheric conditions  

Microsoft Academic Search

In general, C3 plant species are more responsive to atmospheric carbon dioxide (CO2) enrichment than C4-plants. Increased relative growth rate at elevated CO2 primarily relates to increased Net Assimilation Rate (NAR), and enhancement of net photosynthesis and reduced photorespiration. Transpiration and stomatal conductance decrease with elevated CO2, water use efficiency and shoot water potential increase, particularly in plants grown at

J. Rozema; H. Lambers

1993-01-01

141

The positive effect of skin transpiration in peach fruit growth  

Microsoft Academic Search

The effect of fruit transpiration on the mechanisms driving peach (Prunus persica (L.) Batsch) daily growth was investigated. In peach, fruit water losses increase during the season and might play a key role in determining fruit growth. Skin transpiration was reduced during the cell expansion stage by enclosing fruit in plastic bags fitted with holes. In the first year, diameter

Brunella Morandi; Luigi Manfrini; Pasquale Losciale; Marco Zibordi; Luca Corelli-Grappadelli

2010-01-01

142

Risk-taking plants  

PubMed Central

Water scarcity is a critical limitation for agricultural systems. Two different water management strategies have evolved in plants: an isohydric strategy and an anisohydric strategy. Isohydric plants maintain a constant midday leaf water potential (?leaf) when water is abundant, as well as under drought conditions, by reducing stomatal conductance as necessary to limit transpiration. Anisohydric plants have more variable ?leaf and keep their stomata open and photosynthetic rates high for longer periods, even in the presence of decreasing leaf water potential. This risk-taking behavior of anisohydric plants might be beneficial when water is abundant, as well as under moderately stressful conditions. However, under conditions of intense drought, this behavior might endanger the plant. We will discuss the advantages and disadvantages of these two water-usage strategies and their effects on the plant’s ability to tolerate abiotic and biotic stress. The involvement of plant tonoplast AQPs in this process will also be discussed.

Sade, Nir; Gebremedhin, Alem; Moshelion, Menachem

2012-01-01

143

AGRONOMY AND SOILS Effects of Different Seeding Rates and Plant Growth Regulators on Early-planted Cotton  

Microsoft Academic Search

Although the early-planted cotton production system offers the potential of improved lint yield, production techniques need to be optimized to ensure consistent yield enhancement. The objec- tives of this study were to determine how different seeding rates and application rates of mepiquat- type plant growth regulator compounds (PGR) affected cotton growth and production under early planting conditions. A field study

W. T. Pettigrew; J. T. Johnson

2005-01-01

144

Parameterisation of the Shuttleworth-Wallace model to estimate daily maximum transpiration for use in crop models  

Microsoft Academic Search

In crop models maximum transpiration is an important component of the computation of water stress factors. It depends on reference climatic variables and leaf area index, and also on soil evaporation which modifies the actual air properties around the plants. This last effect is not accounted for in classical approaches used in crop models. Yet Shuttleworth and Wallace theory offers

Nadine Brisson; Bernard Itier; Jean Claude L'Hotel; Jean Yves Lorendeau

1998-01-01

145

Reference Canopy Stomatal Conductance Explains Spatiotemporal Patterns of Tree Transpiration  

NASA Astrophysics Data System (ADS)

Increased heterogeneity in patterns of whole tree transpiration (EC) with increasing atmospheric vapor pressure deficit (D) suggests a dynamic response of sap flow velocity (JS) to environmental drivers. We hypothesized that differences in reference stomatal conductance (GSref), stomatal conductance at D = 1kPa, would explain the spatiotemporal dynamics of JS. Using a coupled model of plant hydraulic and biochemical processes we tested this hypothesis with sap flux data for 106 aspen ( Populus tremuloides) and 108 sugar maple ( Acer saccharum) trees collected from plots using in 2-D cyclic sampling scheme during the summer of 2005 in northern Wisconsin. Inverse modeling is used to estimate GSref for each tree. For each species, trees from across the ranges of JS and diameter distributions are compared. GSref explained temporal variability in spatial patterns of EC We explore several possible mechanistic explanations for differences in GSref among trees. Topoedaphic factors are considered to determine if location within a stand has an effect. We also consider competition with neighboring individuals as a possible explanation. Variations in GSref in aspen were explained in part by competition for light between neighboring individuals, while competition for light was not a significant factor for sugar maple. Based on simulation analysis we identify possible biochemical feedbacks as drivers of the variability in plant hydraulics. Other factors examined included micro-topography within both sites.

Loranty, M. M.; Mackay, D. S.; Ewers, B. E.; Kruger, E. L.; Traver, E.

2007-12-01

146

Transpiration affects soil CO2 production in a dry grassland  

NASA Astrophysics Data System (ADS)

Although soil CO2 efflux can be highly variable on the diel time scale, it is often measured during daytime only. However, to get a full understanding of soil CO2 efflux and its impact on carbon cycle processes, looking at diurnal processes is crucial. Therefore, our aim was to investigate how diel variation in soil CO2 efflux from a dry, sandy grassland in Hungary depends on variations in potential drivers, such as gross primary production (GPP) and evapotranspiration (ET). In order to reach this goal, we combined measurements of CO2 and H2O fluxes by eddy covariance, soil chambers and soil CO2 gradient system. Surface CO2 fluxes were partitioned into the three CO2 production components originating from the three soil layers to clarify the timing and the source of the CO2 within the top 50 cm of the soil. CO2 production rates during the growing season were higher during nighttime than during daytime. This diel course was not only driven by soil temperature and soil moisture, but also by ET. This was shown by changes of ET causing a hysteresis loop in the diel response of CO2 production to soil temperature. CO2 production was coupled to soil temperature at night and during midday (12-14 h), when ET remained relatively constant. However, when ET was changing over time, CO2 production was decoupled from soil temperature. In order to disentangle these effects, we carried out time-lag analyses between CO2 production and efflux residuals after having subtracted the main effects of soil temperature and soil water content from measured CO2 fluxes. The results showed a strong negative correlation between ET rates and residuals of soil CO2 production, and a less strong, but still significantly time-lagged positive correlation between GPP and residuals of soil CO2 production. Thus, we could show that there is a rapid negative response of soil CO2 production rates to transpiration (suggesting CO2 transport in the xylem stream) and a delayed positive response to GPP, indicating the importance of newly synthesized non-structural carbohydrates for soil respiration. We conclude that the instant effect of soil temperature and transpiration in combination with the time-lagged effect of GPP governed the diel changes in soil CO2 production at our site. If measurements are carried out at night or during daytime only, then this can lead to considerable misinterpretations of CO2 production rates. Hence we recommend that estimates of respiration rates at a specific site should include both nocturnal and daytime processes.

Balogh, János; Fóti, Szilvia; Pintér, Krisztina; Burri, Susanne; Eugster, Werner; Papp, Marianna; Nagy, Zoltán

2014-05-01

147

Evaluating potential impacts of species conversion on transpiration in the Piedmont of North Carolina  

NASA Astrophysics Data System (ADS)

Land management practices that include species conversion or vegetation manipulation can have consequences to surface water availability, groundwater recharge, streamflow generation, and water quality through altering the transpiration processes in forested watersheds. Our objective in this study is to compare stand water use or transpiration in a piedmont mixed hardwood stand (i.e., present stand) to five hypothetical single species stands (i.e., management scenarios), [Quercus spp. (oak), Acer Rubrum (red maple), Liquidambar styraciflua (sweetgum), Liriodendron tulipifera (tulip poplar), and Pinus Taeda (loblolly pine]. Since October 2007, six watersheds with a flume or v-notch weir installed at the watershed outlet have been monitored for baseline streamflow rates (mm d-1). In the summer of 2010, five trees from each of the above species were instrumented with sap flow sensors in the riparian upland of one watershed to develop linkages between stand stream runoff and transpiration. The sap flow or thermal heat dissipation method was used to calculate tree sap flux density for the mixed hardwood stand. Tree sapwood area and stand tree density were then used to compute stand transpiration rates, mm d-1, from June - August 2010. The parameters of the hypothetical single species stands were based on values determined from mixed hardwood stand conditions (e.g., the same stand sapwood area and stand tree density were applied to each option). The diameter at beast height of the monitored trees ranged from 10 cm to 38 cm with a water use range of 1.8 kg d-1 to 104 kg d-1. From our preliminary data, we found daily transpiration from the mixed hardwood stand (2.8 mm d-1 ± 0.06) was significantly (p < 0.05) lower than daily transpiration from the red maple (3.7 mm d-1 ± 0.14) and tulip poplar (3.5 mm d-1 ± 0.12) single species stand management option and significantly (p < 0.05) higher than the loblolly pine (2.3 mm d-1 ± 0.08), sweetgum (2.1 mm d-1 ± 0.08) and oak spp. (1.4 mm d-1 ± 0.04) option. Given that our data represent growing season conditions, these daily transpiration differences are likely a result of physical and physiological differences related to species canopy properties or root distribution and functions. Daily streamflow rates could be reduced by as much as 40% in the red maple scenario because of the increase in daily transpiration. This reduction in flow could have long-term implications and risk to water quality conditions and aquatic species habitat. We will continue to monitor transpiration rates in this mixed hardwood stand to quantify the seasonal variability in water use.

Boggs, J.; Treasure, E.; Simpson, G.; Domec, J.; Sun, G.; McNulty, S.

2010-12-01

148

Transpiration and root development of urban trees in structural soil stormwater reservoirs.  

PubMed

Stormwater management that relies on ecosystem processes, such as tree canopy interception and rhizosphere biology, can be difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation. Yet such systems offer a potentially valuable tool for achieving both sustainable urban forests and stormwater management. We evaluated tree water uptake and root distribution in a novel stormwater mitigation facility that integrates trees directly into detention reservoirs under pavement. The system relies on structural soils: highly porous engineered mixes designed to support tree root growth and pavement. To evaluate tree performance under the peculiar conditions of such a stormwater detention reservoir (i.e., periodically inundated), we grew green ash (Fraxinus pennsylvanica Marsh.) and swamp white oak (Quercus bicolor Willd.) in either CUSoil or a Carolina Stalite-based mix subjected to three simulated below-system infiltration rates for two growing seasons. Infiltration rate affected both transpiration and rooting depth. In a factorial experiment with ash, rooting depth always increased with infiltration rate for Stalite, but this relation was less consistent for CUSoil. Slow-drainage rates reduced transpiration and restricted rooting depth for both species and soils, and trunk growth was restricted for oak, which grew the most in moderate infiltration. Transpiration rates under slow infiltration were 55% (oak) and 70% (ash) of the most rapidly transpiring treatment (moderate for oak and rapid for ash). We conclude this system is feasible and provides another tool to address runoff that integrates the function of urban green spaces with other urban needs. PMID:19707704

Bartens, Julia; Day, Susan D; Harris, J Roger; Wynn, Theresa M; Dove, Joseph E

2009-10-01

149

Canopy Transpiration in a Chronosequence of Central Siberian Pine Forests  

NASA Technical Reports Server (NTRS)

Tree transpiration was measured in 28, 67, 204 and 383 - year old uniform stands and in a multi-cohort stand (140 t0 430) of Pinus sylvestris ssp. sibirica Lebed. in Central Siberia during August of 1995.

Reiner, Z.; Ernst-Detler, S.; Christian, W.; Ernst-Eckart, S.; Waldemar, Z.

1998-01-01

150

Transpiration during life cycle in controlled wheat growth  

NASA Technical Reports Server (NTRS)

A previously developed model of wheat growth, designed for convenient incorporation into system level models of advanced space life support systems is described. The model is applied to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. The adequacy of modeling the transpiration as proportional to the inedible biomass and an age factor that varies during the life cycle are discussed.

Volk, Tyler; Rummel, John D.

1990-01-01

151

Thermographic measurements on plant leaves  

Microsoft Academic Search

An important process of plant physiology is the transpiration of plant leaves. It is actively controlled by pores (stomata) in the leaf and the governing feature for vital factors such as gas exchange and water transport affixed to which is the nutrient transport from the root to the shoot. Because of its importance, the transpiration and water transport in leaves

Christoph Garbe; Ulrich Schurr; Bernd Jaehne

2002-01-01

152

ESTIMATES OF ISOPRENE AND MONOTERPENE EMISSION RATES IN PLANTS  

EPA Science Inventory

A range of plant species, including crops, shrubs, herbs, and trees, was surveyed to determine the magnitude of isoprene emissions. In studies to determine if plants emitted isoprene, greenhouse-grown plants were encapsulated in impermeable plastic bags and kept in a growth chamb...

153

An experimental study on the efficiency of transpiration cooling in laminar and turbulent hypersonic flows  

NASA Astrophysics Data System (ADS)

An experimental study on the efficiency of transpiration cooling in hypersonic laminar and turbulent flow regimes is carried out in the Hypersonic Windtunnel Cologne with a focus on the aerothermal problems downstream of the cooled model part. The model is made of a material of low thermal conductivity (PEEK) with an integrated probe of a porous material. The experimental setup allows the direct comparison of the thermal behavior of transpiration cooling to a well-defined and radiatively cooled reference surface. Experiments are performed at Mach number of 6 and two different Reynolds numbers. Air, argon and helium are used as coolants at various flow rates, in order to identify the influence of coolant medium on cooling efficiency. The cooling efficiency of air and argon is comparable. Helium provides significantly higher cooling efficiency at the same blowing ratio, i.e. same coolant mass flow rate. The experimental data shows that the efficiency of the transpiration cooling in turbulent flows is much lower than in laminar flow.

Gülhan, A.; Braun, S.

2011-03-01

154

Biological and environmental controls on tree transpiration in a suburban landscape  

NASA Astrophysics Data System (ADS)

Tree transpiration provides a variety of ecosystem services in urban areas, including amelioration of urban heat island effects and storm water management. Tree species vary in the magnitude and seasonality of transpiration owing to differences in physiology, response to climate, and biophysical characteristics, thereby complicating efforts to manage evapotranspiration at city scales. We report sap flux measurements during the 2007 and 2008 growing seasons for dominant tree species in a suburban neighborhood of Minneapolis-Saint Paul, Minnesota, USA. Evergreen needleleaf trees had significantly higher growing season means and annual transpiration per unit canopy area (1.90 kg H2O m-2 d-1 and 307 kg H2O m-2 yr-1, respectively) than deciduous broadleaf trees (1.11 kg H2O m-2 d-1 and 153 kg H2O m-2 yr-1, respectively) because of a smaller projected canopy area (31.1 and 73.6 m2, respectively), a higher leaf area index (8.8 and 5.5 m2 m-2, respectively), and a longer growth season (8 and 4 months, respectively). Measurements also showed patterns consistent with the species' differences in xylem anatomy (conifer, ring porous, and diffuse porous). As the growing season progressed, conifer and diffuse porous genera had increased stomatal regulation to high vapor pressure deficit, while ring porous genera maintained greater and more constant stomatal regulation. These results suggest that evaporative responses to climate change in urban ecosystems will depend in part on species composition. Overall, plant functional type differences in canopy structure and growing season length were most important in explaining species' differences in midsummer and annual transpiration, offering an approach to predicting the evapotranspiration component of urban water budgets.

Peters, Emily B.; McFadden, Joseph P.; Montgomery, Rebecca A.

2010-12-01

155

Multiple major increases and decreases in mitochondrial substitution rates in the plant family Geraniaceae  

Microsoft Academic Search

BACKGROUND: Rates of synonymous nucleotide substitutions are, in general, exceptionally low in plant mitochondrial genomes, several times lower than in chloroplast genomes, 10–20 times lower than in plant nuclear genomes, and 50–100 times lower than in many animal mitochondrial genomes. Several cases of moderate variation in mitochondrial substitution rates have been reported in plants, but these mostly involve correlated changes

Christopher L Parkinson; Jeffrey P Mower; Yin-Long Qiu; Andrew J Shirk; Keming Song; Nelson D Young; Claude W dePamphilis; Jeffrey D Palmer

2005-01-01

156

Common cause failure rate estimates for diesel generators in nuclear power plants  

SciTech Connect

Common cause fault rates for diesel generators in nuclear power plants are estimated, using Licensee Event Reports for the years 1976 through 1978. The binomial failure rate method, used for obtaining the estimates, is briefly explained. Issues discussed include correct classification of common cause events, grouping of the events into homogeneous data subsets, and dealing with plant-to-plant variation.

Steverson, J.A.; Atwood, C.L.

1981-09-01

157

The effect of wind velocity on transpiration in a mixed broadleaved deciduous forest  

NASA Astrophysics Data System (ADS)

Wind velocity (U) within and above forest canopies can alter the coupling between the vapor-saturated sub-stomatal airspace and the drier atmosphere aloft, thereby influencing transpiration rates. In practice, however, the actual increase in transpiration with increasing U depends on the aerodynamic resistance (RA) to vapor transfer compared to canopy resistance to water vapor flux out of leaves (RC, dominated by stomatal resistance, Rstom), and the rate at which RA decreases with increasing U. We investigated the effect of U on transpiration at the canopy scale using filtered meteorological data and sap flux measurements gathered from six diverse species of a mature broadleaved deciduous forest. Only under high light conditions, stand transpiration (EC) increased slightly (6.5%) with increasing U ranging from ~0.7 to ~4.7 m s-1. Under other conditions, sap flux density (Js) and EC responded weakly or did not change with U. RA, estimated from Monin-Obukhov similarity theory, decreased with increasing U, but this decline was offset by increasing RC, estimated from a rearranged Penman-Monteith equation, due to a concurrent increase in vapor pressure deficit (D). The increase of RC with D over the observed range of U was consistent with increased Rstom by ~40% based on hydraulic theory. Except for very rare half-hourly values, the proportion of RA to total resistance (RT) remained < 15% over the observed range of conditions. These results suggest that in similar forests and conditions, accounting for the effects of U-D relationship on Rstom would reduce the uncertainty of modeling canopy gas exchange more than accounting for the direct effect of U on RA.

Kim, D.; Oren, R.; Oishi, A. C.; Hsieh, C.; Phillips, N. G.; Novick, K. A.; Stoy, P. C.

2013-12-01

158

Seasonal changes in Cyclobalanopsis glauca transpiration and canopy stomatal conductance and their dependence on subterranean water and climatic factors in rocky karst terrain  

NASA Astrophysics Data System (ADS)

SummaryThe presence of forest on south China karst is presumed to increase perennial epikarst spring flow, partly because there is adequate storage in bedrock fractures underlying the shallow soil in the forest. If true, transpiration of the ecosystem would not be strongly reduced by temperate drought if trees develop deep roots to reach the perched epikarst water. Therefore, in karst ecosystem the epikarst-soil-plant-atmosphere continuum (ESPAC) would be different from the SPAC in non-karst system. We measured transpiration and canopy conductance from a Cyclobalanopsis glauca (syn. Quercus glauca) stand on a rocky hill slope in South China during 2006-2007 by using the Granier's sap-flow method. Annual stand transpiration (836 mm y -1) accounted for 48.7% of the rainfall during the experimental year. Per month, daily stand transpiration ( E c) maximums varied between 2.1 mm d -1 in January (cool season) to 5.1 mm d -1 in July (hot season). In the driest months, September and October, E c of C. glauca was still high with maximum E c 3.82 mm d -1 and 2.96 mm d -1 respectively. Solar radiation ( PAR), vapor pressure deficiency ( VPD), and air temperature were simple influences on transpiration of C. glauca, which contributed to a quadratic power model, while soil water content ( SWC) moisture influence on transpiration was complicated, which SWC influenced E c greatly under higher VPD, but did not influence E c under low VPD. High stomatal openness occurred in C. glauca in the early morning and declined throughout the day. The relation coefficient between canopy stomatal conductance ( G c) and E c was high when VPD was more than 1.0 kPa, moderate when 0.5 kPa < VPD < 1.0 kPa, and low with VPD of less than 0.5 kPa. Under high VPD, stomatal control of transpiration is high. The pattern of seasonal change of transpiration and canopy stomatal conductance of the plant in karst regions is different from that in non-karst regions, with the stand transpiration and canopy stomatal conductance being high even during the dry season in the karst region because karst plants obtain water partially from the epikarst. With high stand transpiration and canopy stomatal conductance, karst vegetation is presumed to be the most important "pathway" for ESPAC.

Huang, Yuqing; Li, Xiankun; Zhang, Zhongfeng; He, Chengxin; Zhao, Ping; You, Yeming; Mo, Ling

2011-05-01

159

Photosynthesis, transpiration, and primary productivity: Scaling up from leaves to canopies and regions using process models and remotely sensed data  

NASA Astrophysics Data System (ADS)

Biophysical and physiological processes in plants and ecosystems occur over a wide range of spatial and temporal scales. Our knowledge (or models) of these processes is largely at small scales. It is, however, difficult to directly apply mechanistic process-oriented models over large scales due to heterogeneities in the distributions of processes, and nonlinearities in the functional responses of processes to environmental variables. On the other hand, simple parametric/empirical models in which system complexity is lumped into a small number of parameters have been widely employed to describe processes at larger scales. The variation of these parameters in these simple parametric/empirical models depends on the underlying biophysical processes. In this work, we showed that detailed process models and simple parametric models for primary production and transpiration could be effectively combined to scale leaf photosynthesis and transpiration up to large spatial scales. The integrated process model, General Energy Mass Transfer Model (GEMTM), was used to identify major factors contributing to the variability of the parameters in the parametric models for regional transpiration and primary production and quantify their responses to these factors. Simulations with the GEMTM showed that net carbon assimilation was proportional to intercepted photosynthetically active radiation (IPAR), but the radiation use efficiency (RUE) changed with leaf N concentration, temperature, and atmospheric CO2 concentration; transpiration was linearly correlated with the product of net primary production (NPP) and atmospheric water vapor pressure deficit (VPD), and the slope varied with leaf N concentration. RUE increased with leaf N content asymptotically, and responded to temperature in an asymmetric bell shape pattern with a 22°C and 26°C optimal temperature under current ambient and doubled CO2 concentration, respectively. A simple parametric NPP model and a regional transpiration model (Tr model) were developed from the relationships and parameter values obtained using the GEMTM. The NPP model reasonably simulated the seasonal and interannual variations of accumulated NPP estimated from field data. Simulated regional distribution of NPP over the Central Grassland Region of the United States was consistent with estimates obtained using other models. NPP increased from 120 gC/m2/year in the northwest to 956 gC/m2/year in the southeast. Simulated regional transpiration had a similar spatial distribution pattern as NPP, ranging from about 16 cmH2O/year to 136 cmH2O/year. The transpiration model introduced in this study provides a mechanism to explicitly couple transpiration and NPP in large-scale analyses, although more complete analysis and validation are required.

Chen, D.-X.; Coughenour, M. B.

2004-12-01

160

The partitioning of evapotranspiration into evaporation and transpiration: an experimental design assessing the effects of changes in vegetation cover  

NSDL National Science Digital Library

This project seeks to improve the studentÃÂs understanding of the terrestrial water budget by exploring the dynamics of one of its major components: evapotranspiration, a process that includes the accumulation of both evaporation from the soil and plant surfaces and plant transpiration. Traditionally in both hydrological and ecological sciences, evapotranspiration has been treated as a single component. However, the partitioning into its major components, soil evaporation and plant transpiration, can have important ecological and hydrological implications, especially in the context of current and predicted changes in climate and vegetation. Notably, this project helps our understanding of the effects of changes in vegetation (as expected from current changes in climate and land use) on the partitioning of evapotranspiration into its major components and how they feedback into other ecological and hydrological processes.

Gerst, Katharine L.

2010-02-16

161

Thermal transpiration through single walled carbon nanotubes and graphene channels  

SciTech Connect

Thermal transpiration through carbon nanotubes (CNTs) and graphene channels is studied using molecular dynamics (MD) simulations. The system consists of two reservoirs connected by a CNT. It is observed that a flow is developed inside the CNT from the low temperature reservoir to the high temperature reservoir when the two reservoirs are maintained at different temperatures. The influence of channel size and temperature gradient on the mean velocity is analysed by varying the CNT diameter and the temperature of one of the reservoirs. Larger flow rate is observed in the smaller diameter CNTs showing an increase in the mean velocity with increase in the temperature gradient. For the flow developed inside the CNTs, slip boundaries occur and the slip length is calculated using the velocity profile. We examine the effect of fluid-wall interaction strength (?{sub fw}), diffusivity (D), and viscosity of the fluid (?) on the temperature induced fluid transport through the CNTs. Similar investigations are also carried out by replacing the CNT with a graphene channel. Results show that the mean velocity of the fluid atoms in the graphene channel is lower than that through the CNTs. This can be attributed to the higher degree of confinement observed in the CNTs.

Thekkethala, Joe Francis; Sathian, Sarith P., E-mail: sarith@nitc.ac.in [Computational Nanotechnology Laboratory, School of Nano Science and Technology, National Institute of Technology Calicut, Kozhikode, Kerala - 673601 (India)

2013-11-07

162

Glutathione and transpiration as key factors conditioning oxidative stress in Arabidopsis thaliana exposed to uranium.  

PubMed

Although oxidative stress has been previously described in plants exposed to uranium (U), some uncertainty remains about the role of glutathione and tocopherol availability in the different responsiveness of plants to photo-oxidative damage. Moreover, in most cases, little consideration is given to the role of water transport in shoot heavy metal accumulation. Here, we investigated the effect of uranyl nitrate exposure (50 ?M) on PSII and parameters involved in water transport (leaf transpiration and aquaporin gene expression) of Arabidopsis wild type (WT) and mutant plants that are deficient in tocopherol (vte1: null ?/?-tocopherol and vte4: null ?-tocopherol) and glutathione biosynthesis (high content: cad1.3 and low content: cad2.1). We show how U exposure induced photosynthetic inhibition that entailed an electron sink/source imbalance that caused PSII photoinhibition in the mutants. The WT was the only line where U did not damage PSII. The increase in energy thermal dissipation observed in all the plants exposed to U did not avoid photo-oxidative damage of mutants. The maintenance of control of glutathione and malondialdehyde contents probed to be target points for the overcoming of photoinhibition in the WT. The relationship between leaf U content and leaf transpiration confirmed the relevance of water transport in heavy metals partitioning and accumulation in leaves, with the consequent implication of susceptibility to oxidative stress. PMID:24389672

Aranjuelo, Iker; Doustaly, Fany; Cela, Jana; Porcel, Rosa; Müller, Maren; Aroca, Ricardo; Munné-Bosch, Sergi; Bourguignon, Jacques

2014-04-01

163

Time-dependent experimental analysis of a thermal transpiration rarefied gas flow  

NASA Astrophysics Data System (ADS)

Thermal transpiration is the macroscopic movement induced in a rarefied gas by a temperature gradient. The gas moves from the lower to the higher temperature zone. An original method is proposed here to measure the stationary mass flow rate of gas created by thermal transpiration in a micro-tube heated at its outlet. In addition, by means of a time-dependent study, parameters such as the pressure variation, the pressure variation speed, and the characteristic time of the system are analyzed. The experimental system is composed of a glass tube of circular cross section and two reservoirs positioned one at the inlet and one at the outlet of the capillary. The reservoirs are connected to two fast response time capacitance diaphragm gauges. By monitoring the pressure variation with time inside both reservoirs, it is possible to measure the macroscopic movement of the gas along the tube. Three gases, nitrogen, argon, and helium, are studied and three temperature differences ?T = 37, 53.5, and 71 K are applied to the tube. The analyzed gas rarefaction conditions vary from near free molecular to slip regime. Finally, Poiseuille counter flows consistent with the experimental zero flow conditions of the thermal transpiration process are proved to be possible.

Rojas-Cárdenas, Marcos; Graur, Irina; Perrier, Pierre; Méolans, J. Gilbert

2013-07-01

164

Overproduction of abscisic acid in tomato increases transpiration efficiency and root hydraulic conductivity and influences leaf expansion.  

PubMed

Overexpression of genes that respond to drought stress is a seemingly attractive approach for improving drought resistance in crops. However, the consequences for both water-use efficiency and productivity must be considered if agronomic utility is sought. Here, we characterize two tomato (Solanum lycopersicum) lines (sp12 and sp5) that overexpress a gene encoding 9-cis-epoxycarotenoid dioxygenase, the enzyme that catalyzes a key rate-limiting step in abscisic acid (ABA) biosynthesis. Both lines contained more ABA than the wild type, with sp5 accumulating more than sp12. Both had higher transpiration efficiency because of their lower stomatal conductance, as demonstrated by increases in delta(13)C and delta(18)O, and also by gravimetric and gas-exchange methods. They also had greater root hydraulic conductivity. Under well-watered glasshouse conditions, mature sp5 plants were found to have a shoot biomass equal to the wild type despite their lower assimilation rate per unit leaf area. These plants also had longer petioles, larger leaf area, increased specific leaf area, and reduced leaf epinasty. When exposed to root-zone water deficits, line sp12 showed an increase in xylem ABA concentration and a reduction in stomatal conductance to the same final levels as the wild type, but from a different basal level. Indeed, the main difference between the high ABA plants and the wild type was their performance under well-watered conditions: the former conserved soil water by limiting maximum stomatal conductance per unit leaf area, but also, at least in the case of sp5, developed a canopy more suited to light interception, maximizing assimilation per plant, possibly due to improved turgor or suppression of epinasty. PMID:17277097

Thompson, Andrew J; Andrews, John; Mulholland, Barry J; McKee, John M T; Hilton, Howard W; Horridge, Jon S; Farquhar, Graham D; Smeeton, Rachel C; Smillie, Ian R A; Black, Colin R; Taylor, Ian B

2007-04-01

165

Overproduction of Abscisic Acid in Tomato Increases Transpiration Efficiency and Root Hydraulic Conductivity and Influences Leaf Expansion1[OA  

PubMed Central

Overexpression of genes that respond to drought stress is a seemingly attractive approach for improving drought resistance in crops. However, the consequences for both water-use efficiency and productivity must be considered if agronomic utility is sought. Here, we characterize two tomato (Solanum lycopersicum) lines (sp12 and sp5) that overexpress a gene encoding 9-cis-epoxycarotenoid dioxygenase, the enzyme that catalyzes a key rate-limiting step in abscisic acid (ABA) biosynthesis. Both lines contained more ABA than the wild type, with sp5 accumulating more than sp12. Both had higher transpiration efficiency because of their lower stomatal conductance, as demonstrated by increases in ?13C and ?18O, and also by gravimetric and gas-exchange methods. They also had greater root hydraulic conductivity. Under well-watered glasshouse conditions, mature sp5 plants were found to have a shoot biomass equal to the wild type despite their lower assimilation rate per unit leaf area. These plants also had longer petioles, larger leaf area, increased specific leaf area, and reduced leaf epinasty. When exposed to root-zone water deficits, line sp12 showed an increase in xylem ABA concentration and a reduction in stomatal conductance to the same final levels as the wild type, but from a different basal level. Indeed, the main difference between the high ABA plants and the wild type was their performance under well-watered conditions: the former conserved soil water by limiting maximum stomatal conductance per unit leaf area, but also, at least in the case of sp5, developed a canopy more suited to light interception, maximizing assimilation per plant, possibly due to improved turgor or suppression of epinasty.

Thompson, Andrew J.; Andrews, John; Mulholland, Barry J.; McKee, John M.T.; Hilton, Howard W.; Horridge, Jon S.; Farquhar, Graham D.; Smeeton, Rachel C.; Smillie, Ian R.A.; Black, Colin R.; Taylor, Ian B.

2007-01-01

166

Effect of aerosols on evapo-transpiration  

NASA Astrophysics Data System (ADS)

Aerosol direct radiative forcing (ARF) at surface is estimated from instantaneous, simultaneous observations of global radiation and aerosol optical depth (AOD) during winter, pre-monsoon and monsoon seasons over a tropical Indian station at the south-eastern end of Indo Gangetic basin. A comparison of observed and model derived ARFs is made and possible reasons for mismatch are discussed. Aerosol-induced reduction in solar visible (0.4-0.7 ?m) spectrum energy (SWvis), contributing 44% to total broad band (0.3-3.0 ?m) energy (SW), and its effect on surface energy fluxes are discussed in this study. Aerosols on an average reduce SWvis at surface by ?27%. SWvis reduces by 14.5 W m-2 for a 0.1 increase in AOD when single scattering albedo (SSA) is 0.979 where as it reduces by 67.5 W m-2 when SSA is 0.867 indicating the significant effect of absorbing aerosols. Effect of ARF on net radiation, Rn, sensible heat flux, H and latent heat flux/evapo-transpiration, LE are estimated using the observed ratios of Rn/SW, H/Rn and LE/Rn, having reasonably good correlation. Observed Rn/SW varies between 0.59 and 0.75 with a correlation of 0.99 between them. LE, calculated by energy balance method, varies from 56% to 74% of Rn but with a lesser correlation, the possible reasons are discussed. For a given ARF, LE decreases by ?14% and Rn by ?15% with respect to observed LE and Rn respectively. The reduction in LE increases from 37% to 54% of ARF when LE increases from 220 W m-2 to 440 W m-2, suggesting that wet soil induces relatively larger reduction in evaporation. The results agree with earlier model sensitivity studies that Rn reduces more with increase in aerosol absorption which is compensated by proportionate reductions in H and LE depending on soil and atmospheric conditions.

Murthy, B. S.; Latha, R.; Kumar, Manoj; Mahanti, N. C.

2014-06-01

167

Modeled hydraulic redistribution by Helianthus annuus L. matches observed data only after model modification to include nighttime transpiration  

NASA Astrophysics Data System (ADS)

The movement of water from moist to dry soil layers through the root systems of plants, referred to as hydraulic redistribution (HR), occurs throughout the world and is thought to influence carbon and water budgets and ecosystem functioning. The realized hydrologic, biogeochemical, and ecological consequences of HR depend on the amount of redistributed water, while the ability to assess these impacts requires models that correctly capture HR magnitude and timing. Using several soil types and two eco-types of Helianthus annuus L. in split-pot experiments, we examined how well the widely used HR modeling formulation developed by Ryel et al. (2002) could match experimental determination of HR across a range of water potential driving gradients. H. annuus carries out extensive nighttime transpiration, and though over the last decade it has become more widely recognized that nighttime transpiration occurs in multiple species and many ecosystems, the original Ryel et al. (2002) formulation does not include the effect of nighttime transpiration on HR. We developed and added a representation of nighttime transpiration into the formulation, and only then was the model able to capture the dynamics and magnitude of HR we observed as soils dried and nighttime stomatal behavior changed, both influencing HR.

Neumann, R. B.; Cardon, Z. G.; Rockwell, F. E.; Teshera-Levye, J.; Zwieniecki, M.; Holbrook, N. M.

2013-12-01

168

Digital control of working fluid flow rate for an OTEC plant  

Microsoft Academic Search

The role of control in operating an OTEC plant efficiently is of great importance. This paper describes digital control of working fluid rate based on an adaptive control theory for the ''Imari2'' OTEC plant at Saga University. Provisions have been made for linkage between the software of the adaptive control theory and the hardware of the OTEC plant. The authors

M. Nakamura; N. Egashira; H. Uehara

1986-01-01

169

Relationship between lead uptake by lettuce and water-soluble low-molecular-weight organic acids in rhizosphere as influenced by transpiration.  

PubMed

The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce plants under high and low transpiration. A physiological mechanism of the roots of lettuce plants governing the relationship between Pb contamination level and quantity of water-soluble LMWOAs in rhizosphere quartz sand and resin, as influenced by transpiration, was proposed. PMID:17894455

Liao, Yuan Chung; Chang Chien, Shui-Wen; Wang, Min-Chao; Shen, Yuan; Seshaiah, Kalluru

2007-10-17

170

Effects of elevated atmospheric CO{sub 2} on canopy transpiration in senescent spring wheat  

SciTech Connect

The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring wheat crop were simulated for atmospheric CO{sub 2} concentrations of 370 {micro}mol mol{sup {minus}1} and 550 {micro}mol mol{sup {minus}1}. The hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air Carbon Dioxide Enrichment wheat experiment in Arizona (1992/93) were used to drive the model. The simulation results were tested against field measurements with special emphasis on the period between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance was scaled to a canopy level in order to be used in the wheat growth model. The simulated intercellular CO{sub 2} concentration, C{sub i} was determined from the ratio of C{sub i} to the CO{sub 2} concentration at the leaf surface, C{sub s}, the leaf to air specific humidity deficit and a possibly unfulfilled transpiration demand. After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their stomatal conductances, leading to a rise in the C{sub i}/C{sub s} ratio. In order to describe this observation, an empirical model approach was developed which took into account the leaf nitrogen content for the calculation of the C{sub i}/C{sub s} ratio. Simulation results obtained with the new model version were in good agreement with the measurements. If changes in the C{sub i}/C{sub s} ratio accorded to the decrease in leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed an underestimation of the daily canopy transpiration of up to twenty percent and a decrease in simulated seasonal canopy transpiration by ten percent. The measured reduction in the seasonal sum of canopy transpiration and soil evaporation owing to CO{sub 2} enrichment, in comparison, was only about five percent.

Grossman, S.; Kimball, B.A.; Hunsaker, D.J.; Long, S.P. et al

1998-12-31

171

Integrating high-rate DAF technology into plant design  

Microsoft Academic Search

Compared with sedimentation, dissolved-air flotation (DAF) is a more efficient clarification process for separating floc particles, which are often low in density. This article investigates the use of short flocculation times with high DAF and filter hydraulic loading rates and examines the feasibility of integrating high-rate DAF technology into water facility design. Research was conducted at pilot scale using two

James K. Edzwald; John E. Tobiason; Tony Amato; Lawrence J. Maggi

1999-01-01

172

Hydrogen isotope ratios of leaf wax n-alkanes in grasses are insensitive to transpiration  

NASA Astrophysics Data System (ADS)

We analyzed hydrogen isotope ratios of high-molecular weight n-alkanes ( ?D l) and oxygen isotope ratios of ?-cellulose ( ?18O C) for C 3 and C 4 grasses grown in the field and in controlled-environment growth chambers. The relatively firm understanding of 18O-enrichment in leaf water and ?-cellulose was used to elucidate fractionation patterns of ?D l signatures. In the different relative humidity environments of the growth chambers, we observed clear and predictable effects of leaf-water enrichment on ?18O C values. Using a Craig-Gordon model, we demonstrate that leaf water in the growth chamber grasses should have experienced significant D-enriched due to transpiration. Nonetheless, we found no effect of transpirational D-enrichment on the ?D l values. In field samples, we saw clear evidence of enrichment (correlating with relative humidity of the field sites) in both ?18O C and ?D l. These seemingly contrasting results could be explained if leaf waxes are synthesized in an environment that is isotopically similar to water entering plant roots due to either temporal or spatial isolation from evaporatively enriched leaf waters. For grasses in the controlled environment, there was no enrichment of source water, whereas enrichment of grass source water via evaporation from soils and/or stems was likely for grass samples grown in the field. Based on these results, evaporation from soils and/or stems appears to affect ?D l, but transpiration from leaves does not. Further evidence for this conclusion is found in modeling expected net evapotranspirational enrichment. A Craig-Gordon model applied to each of the field sites yields leaf water oxygen isotope ratios that can be used to accurately predict the observed ?18O C values. In contrast, the calculated leaf water hydrogen isotope ratios are more enriched than what is required to predict observed ?D l values. These calculations lend support to the conclusion that while ?18O C reflects both soil evaporation and transpiration, ?D l appears to only record evaporation from soils and/or stems. Therefore, the ?D of n-alkanes can likely be used to reconstruct the ?D of water entering a leaf, supporting the soil-enrichment model of Smith and Freeman (2006). In both the field and controlled studies, we found significant photosynthetic pathway effects on n-alkane ?D suggesting that biochemical pathways or plant phylogeny have a greater effect on leaf wax ?D than leaf-water enrichment in grasses.

McInerney, Francesca A.; Helliker, Brent R.; Freeman, Katherine H.

2011-01-01

173

Oxygen isotopic composition of soil water: Quantifying evaporation and transpiration  

Microsoft Academic Search

The oxygen isotopic composition of soil water provides an extra quantitative dimension in water balance analysis which allows separation of evaporation from transpiration. Spatial and temporal variations in water content and oxygen isotopic composition in soils along an arid to humid transect in Hawaii reflect the processes of recharge by rain, mixing with antecedent moisture, and evapotranspiration. Rainwater is always

Jean C. C Hsieh; Oliver A Chadwick; Eugene F Kelly; Samuel M Savin

1998-01-01

174

A Comparative Analysis of Transpiration and Bare Soil Evaporation  

Microsoft Academic Search

Transpiration Ev and bare soil evaporation Eb processes are comparatively analysed assuming homogeneous and inhomogeneous areal distributions of volumetric soil moisture content ?. For a homogeneous areal distribution of ? we use a deterministic model, while for inhomogeneous distributions a statistical-deterministic diagnostic surface energy balance model is applied. The areal variations of ? are simulated by Monte-Carlo runs assuming normal

Ferenc Ács

2003-01-01

175

ARC Ignition Phenomena with a Transpiration Cooled Anode  

Microsoft Academic Search

This paper deals with the problem of ignition to the porous transpiration cooled anode of an arc in 1 atm. argon. This was observed for both porous graphite and sintered porous tungsten anodes, in the latter case causing melt spots to form which limited the useful life of the anode. A study was undertaken to overcome this problem in which

C. Sheer; S. Korman

1973-01-01

176

The Competition between Liquid and Vapor Transport in Transpiring Leaves.  

PubMed

In leaves, the transpirational flux of water exits the veins as liquid and travels toward the stomata in both the vapor and liquid phases before exiting the leaf as vapor. Yet, whether most of the evaporation occurs from the vascular bundles (perivascular), from the photosynthetic mesophyll cells, or within the vicinity of the stomatal pore (peristomatal) remains in dispute. Here, a one-dimensional model of the competition between liquid and vapor transport is developed from the perspective of nonisothermal coupled heat and water molecule transport in a composite medium of airspace and cells. An analytical solution to the model is found in terms of the energy and transpirational fluxes from the leaf surfaces and the absorbed solar energy load, leading to mathematical expressions for the proportions of evaporation accounted for by the vascular, mesophyll, and epidermal regions. The distribution of evaporation in a given leaf is predicted to be variable, changing with the local environment, and to range from dominantly perivascular to dominantly peristomatal depending on internal leaf architecture, with mesophyll evaporation a subordinate component. Using mature red oak (Quercus rubra) trees, we show that the model can be solved for a specific instance of a transpiring leaf by combining gas-exchange data, anatomical measurements, and hydraulic experiments. We also investigate the effect of radiation load on the control of transpiration, the potential for condensation on the inside of an epidermis, and the impact of vapor transport on the hydraulic efficiency of leaf tissue outside the xylem. PMID:24572172

Rockwell, Fulton Ewing; Holbrook, N Michele; Stroock, Abraham Duncan

2014-04-01

177

Extensive variation in synonymous substitution rates in mitochondrial genes of seed plants  

PubMed Central

Background It has long been known that rates of synonymous substitutions are unusually low in mitochondrial genes of flowering and other land plants. Although two dramatic exceptions to this pattern have recently been reported, it is unclear how often major increases in substitution rates occur during plant mitochondrial evolution and what the overall magnitude of substitution rate variation is across plants. Results A broad survey was undertaken to evaluate synonymous substitution rates in mitochondrial genes of angiosperms and gymnosperms. Although most taxa conform to the generality that plant mitochondrial sequences evolve slowly, additional cases of highly accelerated rates were found. We explore in detail one of these new cases, within the genus Silene. A roughly 100-fold increase in synonymous substitution rate is estimated to have taken place within the last 5 million years and involves only one of ten species of Silene sampled in this study. Examples of unusually slow sequence evolution were also identified. Comparison of the fastest and slowest lineages shows that synonymous substitution rates vary by four orders of magnitude across seed plants. In other words, some plant mitochondrial lineages accumulate more synonymous change in 10,000 years than do others in 100 million years. Several perplexing cases of gene-to-gene variation in sequence divergence within a plant were uncovered. Some of these probably reflect interesting biological phenomena, such as horizontal gene transfer, mitochondrial-to-nucleus transfer, and intragenomic variation in mitochondrial substitution rates, whereas others are likely the result of various kinds of errors. Conclusion The extremes of synonymous substitution rates measured here constitute by far the largest known range of rate variation for any group of organisms. These results highlight the utility of examining absolute substitution rates in a phylogenetic context rather than by traditional pairwise methods. Why substitution rates are generally so low in plant mitochondrial genomes yet occasionally increase dramatically remains mysterious.

Mower, Jeffrey P; Touzet, Pascal; Gummow, Julie S; Delph, Lynda F; Palmer, Jeffrey D

2007-01-01

178

Response of ammonium removal to growth and transpiration of Juncus effusus during the treatment of artificial sewage in laboratory-scale wetlands.  

PubMed

The correlation between nitrogen removal and the role of the plants in the rhizosphere of constructed wetlands are the subject of continuous discussion, but knowledge is still insufficient. Since the influence of plant growth and physiological activity on ammonium removal has not been well characterized in constructed wetlands so far, this aspect is investigated in more detail in model wetlands under defined laboratory conditions using Juncus effusus for treating an artificial sewage. Growth and physiological activity, such as plant transpiration, have been found to correlate with both the efficiency of ammonium removal within the rhizosphere of J. effusus and the methane formation. The uptake of ammonium by growing plant stocks is within in a range of 45.5%, but under conditions of plant growth stagnation, a further nearly complete removal of the ammonium load points to the likely existence of additional nitrogen removal processes. In this way, a linear correlation between the ammonium concentration inside the rhizosphere and the transpiration of the plant stocks implies that an influence of plant physiological activity on the efficiency of N-removal exists. Furthermore, a linear correlation between methane concentration and plant transpiration has been estimated. The findings indicate a fast response of redox processes to plant activities. Accordingly, not only the influence of plant transpiration activity on the plant-internal convective gas transport, the radial oxygen loss by the plant roots and the efficiency of nitrification within the rhizosphere, but also the nitrogen gas released by phytovolatilization are discussed. The results achieved by using an unplanted control system are different in principle and characterized by a low efficiency of ammonium removal and a high methane enrichment of up to a maximum of 72.7% saturation. PMID:23764577

Wiessner, A; Kappelmeyer, U; Kaestner, M; Schultze-Nobre, L; Kuschk, P

2013-09-01

179

Transpiration and groundwater uptake from farm forest plots of Casuarina glauca and Eucalyptus camaldulensis in saline areas of southeast Queensland, Australia  

Microsoft Academic Search

Plantings of salt-tolerant tree species are commonly used to manage shallow saline water tables in agricultural lands in Australia. Eucalyptus camaldulensis is often used for this purpose due to its salt tolerance and ability to use groundwater. Salt tolerance studies suggest that Casuarina glauca would also have groundwater management potential, however, little is known about its transpiration and groundwater uptake

Viki A. Cramer; Peter J. Thorburn; Grant W. Fraser

1999-01-01

180

Numerical Simulation of Supercritical Water Oxidation with a Transpiring Wall Reactor  

Microsoft Academic Search

Transpiring wall reactor is a promising engineering solution to corrosion and salt precipitation for the technology of supercritical water oxidation. Characteristics of flow conditions and species concentrations in the reactor and around the transpiring wall are hardly accessible to measurements. So a computational fluid dynamic model of the transpiring wall reactor was developed. The influence of different operating parameters on

Fengming Zhang; Shouyan Chen; Zhiqiang Wang; Chunyuan Ma; Guifang Chen; Jiaming Zhang

2010-01-01

181

Enhanced transpiration by riparian buffer trees in response to advection in a humid temperate agricultural landscape  

USGS Publications Warehouse

Riparian buffers are designed as management practices to increase infiltration and reduce surface runoff and transport of sediment and nonpoint source pollutants from crop fields to adjacent streams. Achieving these ecosystem service goals depends, in part, on their ability to remove water from the soil via transpiration. In these systems, edges between crop fields and trees of the buffer systems can create advection processes, which could influence water use by trees. We conducted a field study in a riparian buffer system established in 1994 under a humid temperate climate, located in the Corn Belt region of the Midwestern U.S. (Iowa). The goals were to estimate stand level transpiration by the riparian buffer, quantify the controls on water use by the buffer system, and determine to what extent advective energy and tree position within the buffer system influence individual tree transpiration rates. We primarily focused on the water use response (determined with the Heat Ratio Method) of one of the dominant species (Acer saccharinum) and a subdominant (Juglans nigra). A few individuals of three additional species (Quercus bicolor, Betula nigra, Platanus occidentalis) were monitored over a shorter time period to assess the generality of responses. Meteorological stations were installed along a transect across the riparian buffer to determine the microclimate conditions. The differences found among individuals were attributed to differences in species sap velocities and sapwood depths, location relative to the forest edge and prevailing winds and canopy exposure and dominance. Sapflow rates for A. saccharinum trees growing at the SE edge (prevailing winds) were 39% greater than SE interior trees and 30% and 69% greater than NW interior and edge trees, respectively. No transpiration enhancement due to edge effect was detected in the subdominant J. nigra. The results were interpreted as indicative of advection effects from the surrounding crops. Further, significant differences were document in sapflow rates between the five study species, suggesting that selection of species is important for enhancing specific riparian buffer functions. However, more information is needed on water use patterns among diverse species growing under different climatic and biophysical conditions to assist policy and management decisions regarding effective buffer design. ?? 2011.

Hernandez-Santana, V.; Asbjornsen, H.; Sauer, T.; Isenhart, T.; Schilling, K.; Schultz, R.

2011-01-01

182

Dioecy is associated with higher diversification rates in flowering plants.  

PubMed

In angiosperms, dioecious clades tend to have fewer species than their nondioecious sister clades. This departure from the expected equal species richness in the standard sister clade test has been interpreted as implying that dioecious clades diversify less and has initiated a series of studies suggesting that dioecy might be an 'evolutionary dead end'. However, two of us recently showed that the 'equal species richness' null hypothesis is not valid in the case of derived char acters, such as dioecy, and proposed a new test for sister clade comparisons; preliminary results, using a data set available in the litterature, indicated that dioecious clades migth diversify more than expected. However, it is crucial for this new test to distinguish between ancestral and derived cases of dioecy, a criterion that was not taken into account in the available data set. Here, we present a new data set that was obtained by searching the phylogenetic literature on more than 600 completely dioecious angiosperm genera and identifying 115 sister clade pairs for which dioecy is likely to be derived (including > 50% of the dioecious species). Applying the new sister clade test to this new dataset, we confirm the preliminary result that dioecy is associated with an increased diversification rate, a result that does not support the idea that dioecy is an evolutionary dead end in angiosperms. The traits usually associated with dioecy, that is, an arborescent growth form, abiotic pollination, fleshy fruits or a tropical distribution, do not influence the diversification rate. Rather than a low diversification rate, the observed species richness patterns of dioecious clades seem to be better explained by a low transition rate to dioecy and frequent losses. PMID:24797166

Käfer, J; de Boer, H J; Mousset, S; Kool, A; Dufay, M; Marais, G A B

2014-07-01

183

Adapting FAO-56 Spreadsheet Program to estimate olive orchard transpiration fluxes under soil water stress condition  

NASA Astrophysics Data System (ADS)

In the Mediterranean environment, where the period of crops growth does not coincide with the rainy season, the crop is subject to water stress periods that may be amplified with improper irrigation management. Agro-hydrological models can be considered an economic and simple tool to optimize irrigation water use, mainly when water represents a limiting factor for crop production. In the last two decades, agro-hydrological physically based models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere system (Feddes et al., 1978; Bastiaanssen et al., 2007). Unfortunately these models, although very reliable, as a consequence of the high number of required variables and the complex computational analysis, cannot often be used. Therefore, simplified agro-hydrological models may represent an useful and simple tool for practical irrigation scheduling. The main objective of the work is to assess, for an olive orchard, the suitability of FAO-56 spreadsheet agro-hydrological model to estimate a long time series of field transpiration, soil water content and crop water stress dynamic. A modification of the spreadsheet is suggested in order to adapt the simulations to a crop tolerant to water stress. In particular, by implementing a new crop water stress function, actual transpiration fluxes and an ecophysiological stress indicator, i. e. the relative transpiration, are computed in order to evaluate a plant-based irrigation scheduling parameter. Validation of the proposed amendment is carried out by means of measured sap fluxes, measured on different plants and up-scaled to plot level. Spatial and temporal variability of soil water contents in the plot was measured, at several depths, using the Diviner 2000 capacitance probe (Sentek Environmental Technologies, 2000) and TDR-100 (Campbell scientific, Inc.) system. The detailed measurements of soil water content, allowed to explore the high spatial variability of soil water content due to the combined effect of the punctual irrigation and the non-uniform root density distribution. A further validation of the plant-based irrigation-timing indicator will be carried out by considering another ecophysiological stress variable like the predawn leaf water potential. Accuracy of the model output was assessed using the Mean Absolute Difference, the Root Mean Square Difference and the efficiency index of Nash and Sutcliffe. Experimental data, recorded during three years of field observation, allowed, with a great level of detail, to investigate on the dynamic of water fluxes from the soil to atmosphere as well as to validate the proposed amendment of the FAO-56 spreadsheet. The modified model simulated with a satisfactory approximation the measured values of average soil water content in the root zone, with error of estimation equal to about 2.0%. These differences can be considered acceptable for practical applications taking into account the intrinsic variability of the data especially in the soil moisture point measurements. An error less than 1 mm was calculated in the daily transpiration estimation. A good performance was observed in the estimation of the cumulate transpiration fluxes.

Rallo, G.; Provenzano, G.; Manzano-Juárez, J.

2012-04-01

184

Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model.  

PubMed

Plants display a range of striking architectural adaptations when grown at elevated temperatures. In the model plant Arabidopsis thaliana, these include elongation of petioles, and increased petiole and leaf angles from the soil surface. The potential physiological significance of these architectural changes remains speculative. We address this issue computationally by formulating a mathematical model and performing numerical simulations, testing the hypothesis that elongated and elevated plant configurations may reflect a leaf-cooling strategy. This sets in place a new basic model of plant water use and interaction with the surrounding air, which couples heat and mass transfer within a plant to water vapour diffusion in the air, using a transpiration term that depends on saturation, temperature and vapour concentration. A two-dimensional, multi-petiole shoot geometry is considered, with added leaf-blade shape detail. Our simulations show that increased petiole length and angle generally result in enhanced transpiration rates and reduced leaf temperatures in well-watered conditions. Furthermore, our computations also reveal plant configurations for which elongation may result in decreased transpiration rate owing to decreased leaf liquid saturation. We offer further qualitative and quantitative insights into the role of architectural parameters as key determinants of leaf-cooling capacity. PMID:23720538

Bridge, L J; Franklin, K A; Homer, M E

2013-08-01

185

Atmospheric CO2 Enrichment of Water Hyacinths: Effects on Transpiration and Water Use Efficiency  

NASA Astrophysics Data System (ADS)

Open-top clear plastic wall chambers enclosing pairs of sunken metal stock tanks, one of each pair of which contained a full cover of water hyacinths, were maintained out-of-doors at Phoenix, Arizona for several weeks during the summer of 1984. One of these chambers represented ambient conditions, while the other three were continuously enriched with carbon dioxide to approximate target concentrations of 500, 650, and 900 ppm. During a 4-week period when plant growth was at its maximum, water hyacinth biomass production increased by 36% for a 300-600 ppm doubling of the atmospheric CO2 content, while water use efficiency, or the biomass produced per unit of water transpired, actually doubled. These results are similar to what has been observed in several terrestrial plants and they indicate the general trend which may be expected to occur as atmospheric CO2 continues to rise in the years ahead.

Idso, Sherwood B.; Kimball, Bruce A.; Anderson, Michael G.

1985-11-01

186

Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow  

NASA Technical Reports Server (NTRS)

A program of experimental research and analysis was conducted to examine the heat transfer and pressure distributions in regions of shock/shock interaction over smooth and transpiration-cooled hemispherical noseshapes. The objective of this investigation was to determine whether the large heat transfer generated in regions of shock/shock interaction can be reduced by transpiration cooling. The experimental program was conducted at Mach numbers of 12 to 16 in the Calspan 48-Inch Shock Tunnel. Type 3 and type 4 interaction regions were generated for a range of freestream unit Reynolds numbers to provide shear layer Reynolds numbers from 10 exp 4 to 10 exp 6 to enable laminar and turbulent interaction regions to be studied. Shock/shock interactions were investigated on a smooth hemispherical nosetip and a similar transpiration-cooled nosetip, with the latter configuration being examined for a range of surface blowing rates up to one-third of the freestream mass flux. While the heat transfer measurements on the smooth hemisphere without shock/shock interaction were in good agreement with Fay-Riddell predictions, those on the transpiration-cooled nosetip indicated that its intrinsic roughness caused heating-enhancement factors of over 1.5. In the shock/shock interaction studies on the smooth nosetip, detailed heat transfer and pressure measurements were obtained to map the variation of the distributions with shock-impingement position for a range of type 3 and type 4 interactions. Such sets of measurements were obtained for a range of unit Reynolds numbers and Mach numbers to obtain both laminar and turbulent interactions. The measurements indicated that shear layer transition has a significant influence on the heating rates for the type 4 interaction as well as the anticipated large effects on type 3 interaction heating. In the absence of blowing, the peak heating in the type 3 and type 4 interaction regions, over the transpiration-cooled model, did not appear to be influenced by the model's rough surface characteristics. The studies of the effects of the transpiration cooling on type 3 and type 4 shock/shock interaction regions demonstrated that large surface blowing rates had significant effect on the structure of the flowfield, enlarging the shock layer and moving the region of peak-heating interaction around the body.

Holden, Michael S.; Rodriguez, Kathleen M.

1992-01-01

187

Stomatal conductance, transpiration and sap flow of tropical montane rain forest trees in the southern Ecuadorian Andes.  

PubMed

We investigated tree water relations in a lower tropical montane rain forest at 1950-1975 m a.s.l. in southern Ecuador. During two field campaigns, sap flow measurements (Granier-type) were carried out on 16 trees (14 species) differing in size and position within the forest stand. Stomatal conductance (g(s)) and leaf transpiration (E(l)) were measured on five canopy trees and 10 understory plants. Atmospheric coupling of stomatal transpiration was good (decoupling coefficient Omega = 0.25-0.43), but the response of g(s) and E(l) to the atmospheric environment appeared to be weak as a result of the offsetting effects of vapor pressure deficit (VPD) and photosynthetic photon flux (PPF) on g(s). In contrast, sap flow (F) followed these atmospheric parameters more precisely. Daily F depended chiefly on PPF sums, whereas on short time scales, VPD impeded transpiration when it exceeded a value of 1-1.2 kPa. This indicates an upper limit to transpiration in the investigated trees, even when soil water supply was not limiting. Mean g(s) was 165 mmol m(-2) s(-1) for the canopy trees and about 90 mmol m(-2) s(-1) for the understory species, but leaf-to-leaf as well as tree-to-tree variation was large. Considering whole-plant water use, variation in the daily course of F was more pronounced among trees differing in size and crown status than among species. Daily F increased sharply with stem diameter and tree height, and ranged between 80 and 120 kg day(-1) for dominant canopy trees, but was typically well below 10 kg day(-1) for intermediate and suppressed trees of the forest interior. PMID:16076777

Motzer, Thomas; Munz, Nicole; Küppers, Manfred; Schmitt, Dieter; Anhuf, Dieter

2005-10-01

188

The effects of exogenous plant growth regulators in the phytoextraction of heavy metals.  

PubMed

The term "assisted phytoextraction" usually refers to the process of applying a chemical additive to contaminated soil in order to increase the metal uptake by crop plants. In this study three commercially available plant growth regulators (PGRs) based on cytokinins (CKs) were used to boost the assisted phytoextraction of Pb and Zn in contaminated soil collected from a former manufactured gas-plant site. The effects of EDTA treatment in soil and PGR treatment in leaves of Helianthus annuus were investigated in terms of dry weight biomass, Pb and Zn accumulation in the upper parts of the plants, Pb and Zn phytoextraction efficiency and transpiration rate. Metal solubility in soil and its subsequent accumulation in shoots were markedly enhanced by EDTA. The combined effects of EDTA and cytokine resulted in an increase in the Pb and Zn phytoextraction efficiency (up to 890% and 330%, respectively, compared to untreated plants) and up to a 50% increase in foliar transpiration. Our results indicate that exogenous PGRs based on CKs can positively assist the phytoextraction increasing the biomass production, the metal accumulation in shoots and the plant transpiration. The observed increase in biomass could be related to its action in stimulation of cell division and shoot initiation. On the other hand, the increase in metal accumulation in upper parts of plant could be related to both the role of PGRs in the enhancement of plant resistance to stress (as toxic metals) and the increase in transpiration rate, i.e. flux of water-soluble soil components and contaminants by the regulation of stomatal opening. PMID:18037469

Tassi, Eliana; Pouget, Joël; Petruzzelli, Gianniantonio; Barbafieri, Meri

2008-03-01

189

Digital control of working fluid flow rate for an OTEC plant  

SciTech Connect

The role of control in operating an OTEC plant efficiently is of great importance. This paper describes digital control of working fluid rate based on an adaptive control theory for the ''Imari2'' OTEC plant at Saga University. Provisions have been made for linkage between the software of the adaptive control theory and the hardware of the OTEC plant. The authors can obtain satisfactory control performance using this digital control system.

Nakamura, M.; Egashira, N.; Uehara, H.

1986-05-01

190

Organ-distinctive changes in respiration rates of rice plants under nickel stress  

Microsoft Academic Search

Nickel (Ni) is an essential mineral element that may accumulate to toxic levels in soils due to anthropogenic activities.\\u000a The growth of rice plants cultured hydroponically was severely impaired when Ni concentration was raised from 0.1 to 0.5 mM.\\u000a However, the decrease in plant growth was not accompanied by any significant effect on respiration rates at the whole plant\\u000a level. Short-term

Andreu Llamas; Amparo Sanz

2008-01-01

191

Rep-rated Z-Pinch Power Plant Concept - Direct Energy Conversion and Shrapnel Generation  

Microsoft Academic Search

We are developing direct energy conversion schemes and shrapnel generation models to be used to optimize a high yield z-pinch IFE power plant concept. The concept uses high yield ( 10 GJ) at low rep-rate ( 0.1 Hz), with a Recyclable Transmission Line (RTL) to provide the necessary standoff between the fusion target and the power plant chamber. The RTL

John S. de Groot; Niels Gronbech-Jensen; Greg Miller; Craig L. Olsen; Gary E. Rochau; Mark S. Derzon; Steven A. Slutz; Rick B. Spielman; Per F. Peterson; Gregory A. Rochau; Robert R. Pederson

2000-01-01

192

Technical solutions for upgrading high rate and medium loaded activated sludge plants for nutrient removal  

Microsoft Academic Search

In order to meet the requirements for total nitrogen removal in sensitive area, as specified by the EC Standards, existing high-rate or medium loaded activated sludge plants treating only carbonaceous pollution have to be upgraded. Two attractive technical solutions are proposed. Depending on both the design and operational conditions of the activated sludge plants, all existing treatment facilities will be

P. Chudoba; R. Pujol

193

Statistical analysis of nuclear power plant pump failure rate variability: some preliminary results  

Microsoft Academic Search

In-Plant Reliability Data System (IPRDS) pump failure data on over 60 selected pumps in four nuclear power plants are statistically analyzed using the Failure Rate Analysis Code (FRAC). A major purpose of the analysis is to determine which environmental, system, and operating factors adequately explain the variability in the failure data. Catastrophic, degraded, and incipient failure severity categories are considered

H. F. Martz; D. E. Whiteman

1984-01-01

194

Development of an improved LNG plant failure rate data base. Final report March 1980June 1981  

Microsoft Academic Search

Questionnaires were sent to LNG plant operators requesting data on failures of gas pretreatment systems, vaporizers, compressors, valves, piping, storage tanks, fire and leak detection systems, etc. The responses were combined to broaden the failure rate data base for major LNG plant equipment. The results generally agree with data found in an earlier survey. The results will be useful for

D. W. Johnson; J. R. Welker

1981-01-01

195

Estimation of SCRAM Rate Trends in Nuclear Power Plants Using Hierarchical Bayes Models  

Microsoft Academic Search

Nuclear reactors are equipped with reactor scram systems to ensure rapid shutdown of the system in the event of leaks, failure of power conversion systems, or other operational abnormalities. The U.S. Nuclear Regulatory Commission (NRC) collects data on scram rates from various nuclear power plants over time to estimate the trend of proper functioning of the plants which in turn

Kaushal K. Mishra; Sujit K. Ghosh

2009-01-01

196

Cancer rates after the Three Mile Island nuclear accident and proximity of residence to the plant  

Microsoft Academic Search

In the light of a possible link between stress and cancer promotion or progression, and of previously reported distress in residents near the Three Mile Island (TMI) nuclear power plant, we attempted to evaluate the impact of the March 1979 accident on community cancer rates. Proximity of residence to the plant, which related to distress in previous studies, was taken

M. C. Hatch; S. Wallenstein; J. Beyea; J. W. Nieves; M. Susser

1991-01-01

197

Oxidation mechanism and overall removal rates of endocrine disrupting chemicals by aquatic plants.  

PubMed

The purpose of this study was to evaluate experimentally and theoretically the oxidation mechanisms and overall removal rates of phenolic endocrine disrupting chemicals (EDCs) by aquatic plants. EDCs used in this study were bisphenol-A (BPA), 2,4-dichlorophenol (2,4-DCP), 4-tert-octylphenol (4-t-OP), and pentachlorophenol (PCP). Referring to reported detection levels in aquatic environments and contaminated sites, the feed concentration of each EDC was set from 1 to 100?g/L. Experimental results showed that, except for PCP, phenolic EDCs were stably and concurrently removed by different types of aquatic plants over 70 days in long-term continuous treatments. Primal enzymes responsible for oxidation of BPA, 2,4-DCP, and 4-t-OP were peroxidases (POs). Moreover, enzymatic removal rates of BPA, 2,4-DCP, and 4-t-OP by POs were more than 2 orders of magnitude larger than those by aquatic plants. Assuming that overall removal rates of EDCs are controlled by mass transfer rates onto liquid films on the surface of aquatic plants, an electrochemical method based on the limiting current theory was developed to measure the mass transfer rates of EDCs. Because of extremely large removal rates of EDCs by POs, observed removal rates by aquatic plants were in reasonably good agreement with calculated results by a mathematical model developed based on an assumption that mass transfer limitation is a rate-limiting step. PMID:24333944

Reis, A R; Tabei, K; Sakakibara, Y

2014-01-30

198

On Assessing Decomposition Rates of Plant Debris and Standard Cellulose Samples in Tundra Communities  

Microsoft Academic Search

Interest in studies on the rate of plant debris decomposition (however labor-consuming they are) is maintained owing to the desire to comprehensively describe the structural and functional characteristics of the Earth’s biogeocenotic cover and to solve the problem of monitoring and long-term prognosis. Numerous attempts to use a simplified approach to the assessment of decomposition rates (substitution of plant samples

N. I. Andreyashkina; N. V. Peshkova

2001-01-01

199

Ethylene synthesis and sensitivity in crop plants  

NASA Technical Reports Server (NTRS)

Closed and semi-closed plant growth chambers have long been used in studies of plant and crop physiology. These studies include the measurement of photosynthesis and transpiration via photosynthetic gas exchange. Unfortunately, other gaseous products of plant metabolism can accumulate in these chambers and cause artifacts in the measurements. The most important of these gaseous byproducts is the plant hormone ethylene (C2H4). In spite of hundreds of manuscripts on ethylene, we still have a limited understanding of the synthesis rates throughout the plant life cycle. We also have a poor understanding of the sensitivity of intact, rapidly growing plants to ethylene. We know ethylene synthesis and sensitivity are influenced by both biotic and abiotic stresses, but such whole plant responses have not been accurately quantified. Here we present an overview of basic studies on ethylene synthesis and sensitivity.

Klassen, Stephen P.; Bugbee, Bruce

2004-01-01

200

Transpiration cooled electrodes and insulators for MHD generators  

DOEpatents

Systems for cooling the inner duct walls in a magnetohydrodynamic (MHD) generator. The inner face components, adjacent the plasma, are formed of a porous material known as a transpiration material. Selected cooling gases are transpired through the duct walls, including electrically insulating and electrode segments, and into the plasma. A wide variety of structural materials and coolant gases at selected temperatures and pressures can be utilized and the gases can be drawn from the generation system compressor, the surrounding environment, and combustion and seed treatment products otherwise discharged, among many other sources. The conduits conducting the cooling gas are electrically insulated through low pressure bushings and connectors so as to electrically isolate the generator duct from the ground.

Hoover, Jr., Delmer Q. (Churchill Boro, PA)

1981-01-01

201

Transpiration of cottonwood\\/willow forest estimated from sap flux  

Microsoft Academic Search

Cottonwood\\/willow forests in the American Southwest consist of discrete, even-aged vegetation patches arranged in narrow strips along active and abandoned stream channels of alluvial flood plains. We used the heat-pulse velocity technique in this study to estimate transpiration in 12 such forest patches along a perennially flowing reach of the San Pedro River in southeastern Arizona, USA during five periods

Sean M. Schaeffer; David G. Williams; David C. Goodrich

2000-01-01

202

DSMC Simulation of thermal transpiration and accomodation pumps  

SciTech Connect

The Direct Simulation Monte Carlo (DSMC) technique is employed to evaluate several configurations of thermal transpiration and accommodation pumps. There is renewed interest in these rarefied flow pumping concepts for Micro-Electro-Mechanical Systems (MEMS) due to advances in micro-fabrication. The simulation results are compared with existing data to understand gas-surface interaction uncertainties in the experiments. Parametric studies are performed to determine the effects of Knudsen number and surface temperature and roughness on the maximum pump pressure ratio.

Hudson, M.L.; Bartel, T.J.

1998-11-01

203

Multiple major increases and decreases in mitochondrial substitution rates in the plant family Geraniaceae  

PubMed Central

Background Rates of synonymous nucleotide substitutions are, in general, exceptionally low in plant mitochondrial genomes, several times lower than in chloroplast genomes, 10–20 times lower than in plant nuclear genomes, and 50–100 times lower than in many animal mitochondrial genomes. Several cases of moderate variation in mitochondrial substitution rates have been reported in plants, but these mostly involve correlated changes in chloroplast and/or nuclear substitution rates and are therefore thought to reflect whole-organism forces rather than ones impinging directly on the mitochondrial mutation rate. Only a single case of extensive, mitochondrial-specific rate changes has been described, in the angiosperm genus Plantago. Results We explored a second potential case of highly accelerated mitochondrial sequence evolution in plants. This case was first suggested by relatively poor hybridization of mitochondrial gene probes to DNA of Pelargonium hortorum (the common geranium). We found that all eight mitochondrial genes sequenced from P. hortorum are exceptionally divergent, whereas chloroplast and nuclear divergence is unexceptional in P. hortorum. Two mitochondrial genes were sequenced from a broad range of taxa of variable relatedness to P. hortorum, and absolute rates of mitochondrial synonymous substitutions were calculated on each branch of a phylogenetic tree of these taxa. We infer one major, ~10-fold increase in the mitochondrial synonymous substitution rate at the base of the Pelargonium family Geraniaceae, and a subsequent ~10-fold rate increase early in the evolution of Pelargonium. We also infer several moderate to major rate decreases following these initial rate increases, such that the mitochondrial substitution rate has returned to normally low levels in many members of the Geraniaceae. Finally, we find unusually little RNA editing of Geraniaceae mitochondrial genes, suggesting high levels of retroprocessing in their history. Conclusion The existence of major, mitochondrial-specific changes in rates of synonymous substitutions in the Geraniaceae implies major and reversible underlying changes in the mitochondrial mutation rate in this family. Together with the recent report of a similar pattern of rate heterogeneity in Plantago, these findings indicate that the mitochondrial mutation rate is a more plastic character in plants than previously realized. Many molecular factors could be responsible for these dramatic changes in the mitochondrial mutation rate, including nuclear gene mutations affecting the fidelity and efficacy of mitochondrial DNA replication and/or repair and – consistent with the lack of RNA editing – exceptionally high levels of "mutagenic" retroprocessing. That the mitochondrial mutation rate has returned to normally low levels in many Geraniaceae raises the possibility that, akin to the ephemerality of mutator strains in bacteria, selection favors a low mutation rate in plant mitochondria.

Parkinson, Christopher L; Mower, Jeffrey P; Qiu, Yin-Long; Shirk, Andrew J; Song, Keming; Young, Nelson D; dePamphilis, Claude W; Palmer, Jeffrey D

2005-01-01

204

Porous Ceramic Coating for Transpiration Cooling of Gas Turbine Blade  

NASA Astrophysics Data System (ADS)

A transpiration cooling system for gas turbine applications has significant benefit for reducing the amount of cooling air and increasing cooling efficiency. In this paper, the porous ceramic coating, which can infiltrate cooling gas, is developed with plasma spraying process, and the properties of the porous coating material such as permeability of cooling gas, thermal conductivity, and adhesion strength are examined. The mixture of 8 wt.% yttria-stabilized zirconia and polyester powders was employed as the coating material, in order to deposit the porous ceramic coating onto Ni-based super alloy substrate. It was shown that the porous ceramic coating has superior permeability for cooling gas. The adhesion strength of the porous coating was low only 20% compared with the thermal barrier coating utilized in current gas turbine blades. Simulation test of hot gas flow around the gas turbine blade verified remarkable reduction of the coating surface temperature by the transpiration cooling mechanism. It was concluded that the transpiration cooling system for the gas turbine could be achieved using the porous ceramic coating developed in this study.

Arai, M.; Suidzu, T.

2013-06-01

205

Rates of molecular evolution and diversification in plants: chloroplast substitution rates correlate with species-richness in the Proteaceae  

PubMed Central

Background Many factors have been identified as correlates of the rate of molecular evolution, such as body size and generation length. Analysis of many molecular phylogenies has also revealed correlations between substitution rates and clade size, suggesting a link between rates of molecular evolution and the process of diversification. However, it is not known whether this relationship applies to all lineages and all sequences. Here, in order to investigate how widespread this phenomenon is, we investigate patterns of substitution in chloroplast genomes of the diverse angiosperm family Proteaceae. We used DNA sequences from six chloroplast genes (6278bp alignment with 62 taxa) to test for a correlation between diversification and the rate of substitutions. Results Using phylogenetically-independent sister pairs, we show that species-rich lineages of Proteaceae tend to have significantly higher chloroplast substitution rates, for both synonymous and non-synonymous substitutions. Conclusions We show that the rate of molecular evolution in chloroplast genomes is correlated with net diversification rates in this large plant family. We discuss the possible causes of this relationship, including molecular evolution driving diversification, speciation increasing the rate of substitutions, or a third factor causing an indirect link between molecular and diversification rates. The link between the synonymous substitution rate and clade size is consistent with a role for the mutation rate of chloroplasts driving the speed of reproductive isolation. We find no significant differences in the ratio of non-synonymous to synonymous substitutions between lineages differing in net diversification rate, therefore we detect no signal of population size changes or alteration in selection pressures that might be causing this relationship.

2013-01-01

206

Effect of stage-specific vital rates on population growth rates and effective population sizes in an endangered iteroparous plant.  

PubMed

Effective population size (N(e)) determines the strength of genetic drift and can influence the level of genetic diversity a population can maintain. Assessing how changes in demographic rates associated with environmental variables and management actions affect N(e) thus can be crucial to the conservation of endangered species. Calculation of N(e) through demographic models makes it possible to use elasticity analyses to study this issue. The elasticity of N(e) to a given vital rate is the proportional change in N(e) associated with a proportional increase in that vital rate. In addition, demographic models can be used to study N(e) and population growth rate (?) simultaneously. Simultaneous examination is important because some vital rates differ diametrically in their associations with ? and N(e). For example, in some cases increasing these vital rates increases ? and decreases N(e). We used elasticity analysis to study the effect of stage-specific survival and flowering rates on N(e), annual effective population size (N(a)), and ? in seven populations of the endangered plant Austrian dragonhead (Dracocephalum austriacum). In populations with ? ? 1, the elasticities of N(e) and N(a) were similar to those of ?. Survival rates of adults were associated with greater elasticities than survival rates of juveniles, flowering rates, or fecundity. In populations with ? < 1, N(e) and N(a) exhibited greater elasticities to juvenile than to adult vital rates. These patterns are similar to those observed in other species with similar life histories. We did not observe contrasting effects of any vital rate on ? and N(e); thus, management actions that increase the ? of populations of Austrian dragonhead will not increase genetic drift. Our results show that elasticity analyses of N(e) and N(a) can complement elasticity analysis of ?. Moreover, such analyses do not require more data than standard matrix models of population dynamics. PMID:22268810

Andrello, Marco; Nicolè, Florence; Till-Bottraud, Irène; Gaggiotti, Oscar E

2012-04-01

207

Multi-Objective Parameter Estimation for Simulating Canopy Transpiration in Forested Watersheds  

NASA Astrophysics Data System (ADS)

Transpiration is a major component flux simulated by distributed land surface process models. However, the uncertainty of parameterizing leaf stomatal function at a large scale represents a significant gap in characterizing physiological responses to climate change and land use pressures. A fuzzy logic parameter estimation technique is first applied to the simulation of four forest stands in northern Wisconsin, using a half-hourly Jarvis-based model of stomatal conductance calibrated to sap flux measurements. Parameterizations for the multiple species are shown to strictly follow plant hydraulics with a linear relationship between stomatal sensitivity to the log of vapor pressure deficit, dGs/lnD, and reference conductance, Gsref, with a slope of 0.6. Plant species falling on this line theoretically regulate water potential to just prevent runaway cavitation. The multi-objective technique is then extended to a series of 25 hillslopes in a Central Sierra Nevada watershed, using a daily model calibrated to thermal remote sensing data acquired at times of both high and low soil moisture. Initially, only canopy parameters are adjusted. Under well-watered conditions the estimated dGs/lnD versus Gsref among all hillslopes follows the same linear relation of slope 0.6. It is then shown that by adding a scalar of vegetation rooting length into the parameter estimation scheme, dGs/lnD versus Gsref among hillslopes also conforms to the theory for water-stressed conditions. The results point to potential use of remote sensing for quantifying plant hydraulic controls on transpiration at regional to global scales.

Mackay, D. S.; Samanta, S.

2002-12-01

208

A study on the optimal hydraulic loading rate and plant ratios in recirculation aquaponic system  

Microsoft Academic Search

The growths of the African catfish (Clarias gariepinus) and water spinach (Ipomoea aquatica) were evaluated in recirculation aquaponic system (RAS). Fish production performance, plant growth and nutrient removal were measured and their dependence on hydraulic loading rate (HLR) was assessed. Fish production did not differ significantly between hydraulic loading rates. In contrast to the fish production, the water spinach yield

Azizah Endut; A. Jusoh; N. Ali; W. B. Wan Nik; A. Hassan

2010-01-01

209

Plant traits are the predominant control on litter decomposition rates within biomes worldwide  

Microsoft Academic Search

Worldwide decomposition rates depend both on climate and the legacy of plant functional traits as litter quality. To quantify the degree to which functional differentiation among species affects their litter decomposition rates, we brought together leaf trait and litter mass loss data for 818 species from 66 decomposition experiments on six continents. We show that: (i) the magnitude of species-driven

William K. Cornwell; Johannes H. C. Cornelissen; K. Amatangalo; Ellen Dorrepaal; Valerie T. Eviner; Oscar Godoy; S. E. Hobbir; Bart Hoorens; Hiroko Kurokawa; N. Perez-Harguindeguy; Helen M. Quested; Louis S. Santiago; David A. Wardle; Ian J. Wright; Rien Aerts; Steven D. Allison; Bodegom van P. M; Victor Brovkin; Alex Chatain; Terry V. Callaghan; S. Diaz; Eric Garnier; Diego E. Gurvich; Elena Kazakou; Julia A. Klein; Jenny Read; Peter B. Reich; Nadejda A. Soudzilovskaia; M. Victoria Vaieretti; Mark Westoby

2008-01-01

210

Parasitic plants have increased rates of molecular evolution across all three genomes  

PubMed Central

Background Theoretical models and experimental evidence suggest that rates of molecular evolution could be raised in parasitic organisms compared to non-parasitic taxa. Parasitic plants provide an ideal test for these predictions, as there are at least a dozen independent origins of the parasitic lifestyle in angiosperms. Studies of a number of parasitic plant lineages have suggested faster rates of molecular evolution, but the results of some studies have been mixed. Comparative analysis of all parasitic plant lineages, including sequences from all three genomes, is needed to examine the generality of the relationship between rates of molecular evolution and parasitism in plants. Results We analysed DNA sequence data from the mitochondrial, nuclear and chloroplast genomes for 12 independent evolutionary origins of parasitism in angiosperms. We demonstrated that parasitic lineages have a faster rate of molecular evolution than their non-parasitic relatives in sequences for all three genomes, for both synonymous and nonsynonymous substitutions. Conclusions Our results prove that raised rates of molecular evolution are a general feature of parasitic plants, not confined to a few taxa or specific genes. We discuss possible causes for this relationship, including increased positive selection associated with host-parasite arms races, relaxed selection, reduced population size or repeated bottlenecks, increased mutation rates, and indirect causal links with generation time and body size. We find no evidence that faster rates are due to smaller effective populations sizes or changes in selection pressure. Instead, our results suggest that parasitic plants have a higher mutation rate than their close non-parasitic relatives. This may be due to a direct connection, where some aspect of the parasitic lifestyle drives the evolution of raised mutation rates. Alternatively, this pattern may be driven by an indirect connection between rates and parasitism: for example, parasitic plants tend to be smaller than their non-parasitic relatives, which may result in more cell generations per year, thus a higher rate of mutations arising from DNA copy errors per unit time. Demonstration that adoption of a parasitic lifestyle influences the rate of genomic evolution is relevant to attempts to infer molecular phylogenies of parasitic plants and to estimate their evolutionary divergence times using sequence data.

2013-01-01

211

Upper-limit mutation rate estimation for a plant RNA virus  

PubMed Central

It is generally accepted that mutation rates of RNA viruses are inherently high due to the lack of proofreading mechanisms. However, direct estimates of mutation rate are surprisingly scarce, in particular for plant viruses. Here, based on the analysis of in vivo mutation frequencies in tobacco etch virus, we calculate an upper-bound mutation rate estimation of 3×10?5 per site and per round of replication; a value which turns out to be undistinguishable from the methodological error. Nonetheless, the value is barely on the lower side of the range accepted for RNA viruses, although in good agreement with the only direct estimate obtained for other plant viruses. These observations suggest that, perhaps, differences in the selective pressures operating during plant virus evolution may have driven their mutation rates towards values lower than those characteristic of other RNA viruses infecting bacteria or animals.

Sanjuan, Rafael; Agudelo-Romero, Patricia; Elena, Santiago F.

2009-01-01

212

Chilling rate effects on pork loin tenderness in commercial processing plants.  

PubMed

The present experiment was conducted to provide a large-scale objective comparison of pork LM tenderness and other meat quality traits among packing plants that differ in stunning method and carcass chilling rate. For each of 2 replicates, pigs were sourced from a single barn of a commercial finishing operation that fed pigs from a single terminal crossbred line. On each day, 3 trucks were loaded, with each of those trucks delivering the pigs to a different plant. Plant A used CO(2) stunning and conventional spray chilling; Plant B used CO(2) stunning and blast chilling; and Plant C used electrical stunning and blast chilling. The boneless, vacuum-packaged loin was obtained from the left side of each carcass (n = 597; 100 · plant(-1) · replicate(-1)). As designed, HCW, LM depth, and LM intramuscular fat percentage did not differ among plants (P > 0.05). By 1.67 h postmortem (1 h after the carcasses exited the harvest floor), the average deep LM temperature was >10°C warmer for Plant A than Plants B and C (32.1°C, 21.6°C, and 19.3°C, for Plants A, B, and C, respectively) and deep LM temperature continued to be >10°C warmer for Plant A until 4.17 h or 6.33 h postmortem than for Plants C and B, respectively. Both plants that used blast chilling produced loins with greater LM slice shear force at 15 d postmortem than did the plant that used conventional spray chilling (P < 0.0001). The frequency of loins with excessively high (>25 kg) LM slice shear force values was greater for Plant B than Plant A (14.7% vs. 1%; P < 0.01). Among all the traits studied, including visual and instrumental evaluations of LM color, ultimate pH, marbling score, and lean color stability, the only other difference between Plants A and B was that purge loss during 13 d (from d 1 to 14) of vacuum-packaged storage was greater for Plant B (P < 0.05). That is, with this sample of pigs and CO(2) stunning, no loin quality advantages were detected for blast chilling. Regardless of chilling method, CO(2) stunning resulted in darker LM lean color and greater LM water-holding capacity than did electrical stunning (P < 0.05). This research shows that differences in chilling systems among pork packing plants can have a strong influence on loin chop tenderness. PMID:22307481

Shackelford, S D; King, D A; Wheeler, T L

2012-08-01

213

A study on the optimal hydraulic loading rate and plant ratios in recirculation aquaponic system.  

PubMed

The growths of the African catfish (Clarias gariepinus) and water spinach (Ipomoea aquatica) were evaluated in recirculation aquaponic system (RAS). Fish production performance, plant growth and nutrient removal were measured and their dependence on hydraulic loading rate (HLR) was assessed. Fish production did not differ significantly between hydraulic loading rates. In contrast to the fish production, the water spinach yield was significantly higher in the lower hydraulic loading rate. Fish production, plant growth and percentage nutrient removal were highest at hydraulic loading rate of 1.28 m/day. The ratio of fish to plant production has been calculated to balance nutrient generation from fish with nutrient removal by plants and the optimum ratio was 15-42 gram of fish feed/m(2) of plant growing area. Each unit in RAS was evaluated in terms of oxygen demand. Using specified feeding regime, mass balance equations were applied to quantify the waste discharges from rearing tanks and treatment units. The waste discharged was found to be strongly dependent on hydraulic loading rate. PMID:19819130

Endut, Azizah; Jusoh, A; Ali, N; Wan Nik, W B; Hassan, A

2010-03-01

214

Rate variation in parasitic plants: correlated and uncorrelated patterns among plastid genes of different function  

PubMed Central

Background The analysis of synonymous and nonsynonymous rates of DNA change can help in the choice among competing explanations for rate variation, such as differences in constraint, mutation rate, or the strength of genetic drift. Nonphotosynthetic plants of the Orobanchaceae have increased rates of DNA change. In this study 38 taxa of Orobanchaceae and relatives were used and 3 plastid genes were sequenced for each taxon. Results Phylogenetic reconstructions of relative rates of sequence evolution for three plastid genes (rbcL, matK and rps2) show significant rate heterogeneity among lineages and among genes. Many of the non-photosynthetic plants have increases in both synonymous and nonsynonymous rates, indicating that both (1) selection is relaxed, and (2) there has been a change in the rate at which mutations are entering the population in these species. However, rate increases are not always immediate upon loss of photosynthesis. Overall there is a poor correlation of synonymous and nonsynonymous rates. There is, however, a strong correlation of synonymous rates across the 3 genes studied and the lineage-speccific pattern for each gene is strikingly similar. This indicates that the causes of synonymous rate variation are affecting the whole plastid genome in a similar way. There is a weaker correlation across genes for nonsynonymous rates. Here the picture is more complex, as could be expected if there are many causes of variation, differing from taxon to taxon and gene to gene. Conclusions The distinctive pattern of rate increases in Orobanchaceae has at least two causes. It is clear that there is a relaxation of constraint in many (though not all) non-photosynthetic lineages. However, there is also some force affecting synonymous sites as well. At this point, it is not possible to tell whether it is generation time, speciation rate, mutation rate, DNA repair efficiency or some combination of these factors.

Young, Nelson D; dePamphilis, Claude W

2005-01-01

215

Cancer rates after the Three Mile Island nuclear accident and proximity of residence to the plant  

SciTech Connect

In the light of a possible link between stress and cancer promotion or progression, and of previously reported distress in residents near the Three Mile Island (TMI) nuclear power plant, we attempted to evaluate the impact of the March 1979 accident on community cancer rates. Proximity of residence to the plant, which related to distress in previous studies, was taken as a possible indicator of accident stress; the postaccident pattern in cancer rates was examined in 69 'study tracts' within a 10-mile radius of TMI, in relation to residential proximity. A modest association was found between postaccident cancer rates and proximity (OR = 1.4; 95% CI = 1.3, 1.6). After adjusting for a gradient in cancer risk prior to the accident, the odds ratio contrasting those closest to the plant with those living farther out was 1.2 (95% CI = 1.0, 1.4). A postaccident increase in cancer rates near the Three Mile Island plant was notable in 1982, persisted for another year, and then declined. Radiation emissions, as modeled mathematically, did not account for the observed increase. Interpretation in terms of accident stress is limited by the lack of an individual measure of stress and by uncertainty about whether stress has a biological effect on cancer in humans. An alternative mechanism for the cancer increase near the plant is through changes in care-seeking and diagnostic practice arising from postaccident concern.

Hatch, M.C.; Wallenstein, S.; Beyea, J.; Nieves, J.W.; Susser, M. (Columbia Univ., New York, NY (USA))

1991-06-01

216

Effects of temperature and humidity on transpiration in adults of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae).  

PubMed

Measurements of water loss were made on adults of the lesser mealworm, Alphitobius diaperinus, using a recording micro-electrobalance and a programmable heat circulator bath. This species originates in tropical regions and infests poultry houses in temperate countries. Two routes of water loss were examined: the general cuticle and via the spiracles. Temperature and relative humidity of the ambient air substantially affect the cuticular transpiration in adults (fresh body weights from 12 mg to 22 mg). At near 0% R.H., between 20 and 40 degrees C the rate of body water loss gradually increased; on the other hand, the insects gained weight in an atmosphere close to saturation. Above 40 degrees C transpiration flow abruptly increased coinciding with the start of vigorous locomotor activity. This critical point corresponds to the opening of the spiracles from which the water is expelled from the tracheal system.In dead specimens, killed by cyanide or solvent, the water vapour slowly diffused out of the spiracles and, as in atracheate insects, the transpiration curves did not show a peak as the air temperature was increased.The thermostupor point (TSP) occurred as the insects became motionless; the corresponding temperature is significantly affected by atmospheric relative humidity (TSP=47.4+/-0.6 degrees C at c. 0% R.H.; TSP=46.6+/-0.7 degrees C at c. 100% R.H.).The transpiration flow was about four times as fast in specimens treated with solvent as in the individuals (live or cyanide-killed) that had undamaged water-proof cuticle. This species has to cope with a double challenge: (i) to adapt its physiology and ecology to poultry-house conditions which constitutes an extension of its primary habitats, and (ii) to survive over winter; high drought resistance and heat tolerance may constitute a pre-adaptation to conquer anthropogenic air-conditioned sites. PMID:12770283

Salin, C; Vernon, P; Vannier, G

1999-10-01

217

Relationship between calcium decoding elements and plant abiotic-stress resistance  

PubMed Central

Serving as an important second messenger, calcium ion has unique properties and universal ability to transmit diverse signals that trigger primary physiological actions in cells in response to hormones, pathogens, light, gravity, and stress factors. Being a second messenger of paramount significance, calcium is required at almost all stages of plant growth and development, playing a fundamental role in regulating polar growth of cells and tissues and participating in plant adaptation to various stress factors. Many researches showed that calcium signals decoding elements are involved in ABA-induced stomatal closure and plant adaptation to drought, cold, salt and other abiotic stresses. Calcium channel proteins like AtTPC1 and TaTPC1 can regulate stomatal closure. Recently some new studies show that Ca2+ is dissolved in water in the apoplast and transported primarily from root to shoot through the transpiration stream. The oscillating amplitudes of [Ca2+]o and [Ca2+]i are controlled by soil Ca2+ concentrations and transpiration rates. Because leaf water use efficiency (WUE) is determined by stomatal closure and transpiration rate, so there may be a close relationship between Ca2+ transporters and stomatal closure as well as WUE, which needs to be studied. The selection of varieties with better drought resistance and high WUE plays an increasing role in bio-watersaving in arid and semi-arid areas on the globe. The current paper reviews the relationship between calcium signals decoding elements and plant drought resistance as well as other abiotic stresses for further study.

Song, Wei-Yi; Zhang, Zheng-Bin; Shao, Hong-Bo; Guo, Xiu-Lin; Cao, Hong-Xing; Zhao, Hong-Bin; Fu, Zheng-Yan; Hu, Xiao-Jun

2008-01-01

218

Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements  

Microsoft Academic Search

Transpiration of a Douglas-fir (Pseudorsuga menziesii (Mirb.) France) stand was evaluated by sap flow measurements during a 4-month period. Between-tree variation in sap flow depended on crown class. On a sunny day, total transpiration was 1.6, 8.0 and 22.0 liters day-' for suppressed, codomi- nant and dominant trees, respectively. Transpiration estimated by sap How fell below potential evapotranspiration when available

A. GRANIER

1987-01-01

219

Thermal/structural analysis of a transpiration cooled nozzle  

NASA Technical Reports Server (NTRS)

The 8-foot High Temperature Tunnel (HTT) at LaRC is a combustion driven, high enthalpy blow down wind tunnel. In Mar. 1991, during check out of the transpiration cooled nozzle, pieces of platelets were found in the tunnel test section. It was determined that incorrect tolerancing between the platelets and the housing was the primary cause of the platelet failure. An analysis was performed to determine the tolerance layout between the platelets and the housing to meet the structural and performance criteria under a range of thermal, pressure, and bolt preload conditions. Three recommendations resulted as a product of this analysis.

Gregory, Peyton B.; Thompson, Jon E.; Babcock, Dale A.; Gray, Carl E., Jr.; Mouring, Chris A.

1992-01-01

220

Control and Augmentation of Passive Porosity through Transpiration Control  

NASA Technical Reports Server (NTRS)

A device for controlling pressure loading of a member caused by a fluid moving past the member or the member moving through a fluid. The device consists of a porous skin mounted over the solid surface of the member and separated from the solid surface by a plenum. Fluid from an area exerting high pressure on the member may enter the plenum through the porous surface and exit into an area exerting a lower pressure on the member, thus controlling pressure loading of the member. A transpirational control device controls the conditions within the plenum thus controlling the side force and yaw moment on the forebody.

Banks, Daniel W. (Inventor); Wood, Richard M. (Inventor); Bauer, Steven X. S. (Inventor)

1999-01-01

221

Modelling leaf photosynthetic and transpiration temperature-dependent responses in Vitis vinifera cv. Semillon grapevines growing in hot, irrigated vineyard conditions  

PubMed Central

Background and aims Grapevines growing in Australia are often exposed to very high temperatures and the question of how the gas exchange processes adjust to these conditions is not well understood. The aim was to develop a model of photosynthesis and transpiration in relation to temperature to quantify the impact of the growing conditions on vine performance. Methodology Leaf gas exchange was measured along the grapevine shoots in accordance with their growth and development over several growing seasons. Using a general linear statistical modelling approach, photosynthesis and transpiration were modelled against leaf temperature separated into bands and the model parameters and coefficients applied to independent datasets to validate the model. Principal results Photosynthesis, transpiration and stomatal conductance varied along the shoot, with early emerging leaves having the highest rates, but these declined as later emerging leaves increased their gas exchange capacities in accordance with development. The general linear modelling approach applied to these data revealed that photosynthesis at each temperature was additively dependent on stomatal conductance, internal CO2 concentration and photon flux density. The temperature-dependent coefficients for these parameters applied to other datasets gave a predicted rate of photosynthesis that was linearly related to the measured rates, with a 1 : 1 slope. Temperature-dependent transpiration was multiplicatively related to stomatal conductance and the leaf to air vapour pressure deficit and applying the coefficients also showed a highly linear relationship, with a 1 : 1 slope between measured and modelled rates, when applied to independent datasets. Conclusions The models developed for the grapevines were relatively simple but accounted for much of the seasonal variation in photosynthesis and transpiration. The goodness of fit in each case demonstrated that explicitly selecting leaf temperature as a model parameter, rather than including temperature intrinsically as is usually done in more complex models, was warranted.

Greer, Dennis H.

2012-01-01

222

Effect of Expansion of Fertilization Width on Nitrogen Recovery Rate in Tea Plants  

NASA Astrophysics Data System (ADS)

In cultivation of tea plants, large amounts of nitrogen, compared to amounts used for other crops, have been used for fertilization, resulting in degradation of the soil environment between hedges and an increase in concentrations of nitrate nitrogen in surrounding water systems. To reduce the environmental load, new methods of fertilizer application are needed. This report deals with the effect of expansion of fertilization width on nitrogen recovery rate in tea plants. In the test field, 15 N-labeled ammonium sulfate had been applied over custom fertilization by between-hedges fertilization (fertilization width of 15cm) and wide fertilization (fertilization width of 40cm), nitrogen recovery rates were compared. Expansion of fertilization width resulted in an approximately 30% increase in nitrogen recovery rate compared to that in the case of fertilization between hedges. Increases in nitrogen recovery rates were observed with fallapplied fertilization, spring-applied fertilization, pop-up fertilizer application, and summerapplied fertilization.

Nonaka, Kunihiko; Hirono, Yuhei; Watanabe, Iriki

223

Somatic deleterious mutation rate in a woody plant: estimation from phenotypic data.  

PubMed

We conducted controlled crosses in populations of the long-lived clonal shrub, Vaccinium angustifolium (lowbush blueberry) to estimate inbreeding depression and mutation parameters associated with somatic deleterious mutation. Inbreeding depression level was high, with many plants failing to set fruit after self-pollination. We also compared fruit set from autogamous pollinations (pollen collected from within the same inflorescence) with fruit set from geitonogamous pollinations (pollen collected from the same plant but from inflorescences separated by several meters of branch growth). The difference between geitonogamous versus autogamous fitness within single plants is referred to as 'autogamy depression' (AD). AD can be caused by somatic deleterious mutation. AD was significantly different from zero for fruit set. We developed a maximum-likelihood procedure to estimate somatic mutation parameters from AD, and applied it to geitonogamous and autogamous fruit set data from this experiment. We infer that, on average, approximately three sublethal, partially dominant somatic mutations exist within the crowns of the plants studied. We conclude that somatic mutation in this woody plant results in an overall genomic deleterious mutation rate that exceeds the rate measured to date for annual plants. Some implications of this result for evolutionary biology and agriculture are discussed. PMID:23778990

Bobiwash, K; Schultz, S T; Schoen, D J

2013-10-01

224

Coal flow aids reduce coke plant operating costs and improve production rates  

SciTech Connect

Chemical coal flow aids can provide many benefits to coke plants, including improved production rates, reduced maintenance and lower cleaning costs. This article discusses the mechanisms by which coal flow aids function and analyzes several successful case histories. 2 refs., 10 figs., 1 tab.

Bedard, R.A.; Bradacs, D.J.; Kluck, R.W.; Roe, D.C.; Ventresca, B.P.

2005-06-01

225

Risk-Rating Saratoga Spittlebug Damage by Abundance of Alterbate-Host Plants.  

National Technical Information Service (NTIS)

The potential damage of the Saratoga spittlebug to red pine can be predicted by comparing the percentage of ground occupied by sweet-fern with the percentage of ground cover occupied by other nymphal host plants. A risk-rating graph is used to estimate po...

L. F. Wilson

1971-01-01

226

Statistical analysis of nuclear power plant valve failure-rate variability: some preliminary results  

Microsoft Academic Search

Valve failure data from the In-Plant Reliability Data System (IPRDS) are statistically analyzed using the Failure Rate Analysis Code (FRAC). Data from five failure modes, four of which are time related and the other demand related, are analyzed to determine which of the factors - operating system, valve size, valve type, operating type, and operating mode - most affect valve

R. J. Beckman; H. F. Martz

1985-01-01

227

Degradation of landfill leachate using transpiring-wall supercritical water oxidation (SCWO) reactor.  

PubMed

Oxidation of landfill leachate wastewater was studied in a transpiring-wall SCWO reactor, operated under varied temperature and pressure 320-430 °C, 18-30 MPa. Effect of temperature and pressure on COD and BOD removal efficiency was investigated. COD and BOD removal efficiency being 99.23%, 98.06% were achieved at 430 °C, 30 MPa, which increased with temperature and pressure. The modified pseudo first-order rate model was regressed from experimental data, taking into account the induction time (t(ind)) effect. The resulting pre-exponential factor A and activation energy E(a) were 34.86 s(-1) and 32.1 kJ mol(-1), respectively, assuming that the reaction order for feed wastewater (based on COD) and oxidant were first order and zero order, respectively. PMID:20483581

Gong, Weijin; Duan, Xuejun

2010-11-01

228

Transpiration cooling in the locality of a transverse fuel jet for supersonic combustors  

NASA Astrophysics Data System (ADS)

The objective of the current work was to determine the feasibility of transpiration cooling for the relief of the local heating rates in the region of a sonic, perpendicular, fuel jet of gaseous hydrogen. Experiments were conducted to determine the interaction between the cooling required and flameholding limits of a transverse jet in a high-enthalpy, Mach 3 flow in both open-jet and direct-connect test mode. Pulsed shadowgraphs were used to illustrate the flow field. Infrared thermal images indicated the surface temperatures, and the OH(-) emission of the flame was used to visualize the limits of combustion. Wall, static presures indicated the location of the combustion within the duct and were used to calculate the combustion efficiency. The results from both series of tests at facility total temperatures of 1700 K and 2000 K are presented.

Northam, G. Burton; Capriotti, Diego P.; Byington, Carl S.

1990-07-01

229

The Effect of Differential Growth Rates across Plants on Spectral Predictions of Physiological Parameters  

PubMed Central

Leaves of various ages and positions in a plant's canopy can present distinct physiological, morphological and anatomical characteristics, leading to complexities in selecting a single leaf for spectral representation of an entire plant. A fortiori, as growth rates between canopies differ, spectral-based comparisons across multiple plants – often based on leaves' position but not age – becomes an even more challenging mission. This study explores the effect of differential growth rates on the reflectance variability between leaves of different canopies, and its implication on physiological predictions made by widely-used spectral indices. Two distinct irrigation treatments were applied for one month, in order to trigger the formation of different growth rates between two groups of grapevines. Throughout the experiment, the plants were physiologically and morphologically monitored, while leaves from every part of their canopies were spectrally and histologically sampled. As the control vines were constantly developing new leaves, the water deficit plants were experiencing growth inhibition, resulting in leaves of different age at similar nodal position across the treatments. This modification of the age-position correlation was characterized by a near infrared reflectance difference between younger and older leaves, which was found to be exponentially correlated (R2?=?0.98) to the age-dependent area of intercellular air spaces within the spongy parenchyma. Overall, the foliage of the control plant became more spectrally variable, creating complications for intra- and inter-treatment leaf-based comparisons. Of the derived indices, the Structure-Insensitive Pigment Index (SIPI) was found indifferent to the age-position effect, allowing the treatments to be compared at any nodal position, while a Normalized Difference Vegetation Index (NDVI)-based stomatal conductance prediction was substantially affected by differential growth rates. As various biotic and abiotic factors may form distinctions in growth, future precision agriculture studies should consider its spectral effect on physiological predictions.

Rapaport, Tal; Hochberg, Uri; Rachmilevitch, Shimon; Karnieli, Arnon

2014-01-01

230

Conversion rates in power plant plumes based on filter pack data: The oil fired Northport plume  

NASA Astrophysics Data System (ADS)

More than 60 airborne plume studies were conducted at a large oil fired power station during a 3 build1/2 year period. These studies were conducted to determine the typical rate of formation of sulfate in the plume and the conditions which most influence these atmospheric processes. The power plant chosen for this program is located in the northeast region of the U.S. and during the course of these studies a typical variety of meteorological conditions were encountered. This is probably the most extensive body of plume data ever gathered from a single power plant. The effect on the oxidation rate was explored for a wide variety of and variation in meteorological conditions. Plume sulfate rarely accounted for more than 5 % of the total plume sulfur even for plume travel times of up to 4 h. For most experiments more than half of the observed plume sulfate was that emitted from the power plant units. The rate of atmospheric oxidation of sulfur dioxide to sulfate was not readily discernible due to the low rate of conversion and the relatively high amount of the sulfate emitted. The results reported in this paper generally indicate an apparent oxidation rate of less than 1 % h -. A diurnal influence or effects due to changes in various meteorological conditions are difficult to discern.

Garber, Robert W.; Forrest, Joseph; Newman, Leonard

231

Using a basin-scale hydrological model to estimate crop transpiration and soil evaporation  

Microsoft Academic Search

Increasing populations and expectations, declining crop yields and the resulting increased competition for water necesitate improvements in irrigation management and productivity. A key factor in defining agricultural productivity is to be able to simulate soil evaporation and crop transpiration. In agribusiness terms, crop transpiration is a useful process while soil and open-water evaporations are wasteful processes. In this study a

G. Kite

2000-01-01

232

Physiological tradeoffs in the parameterization of a model of canopy transpiration  

Microsoft Academic Search

We examined physiological parameter tradeoffs in modeling stomatal control of transpiration from a number of forest species. Measurements of sapflux, micrometeorology, and leaf area index were made in stands representing 85% of the forest ecosystems around the WLEF eddy flux tower in northern Wisconsin. A Jarvis-based canopy conductance model was used to simulate canopy transpiration (EC) for five tree species

D. S. Mackay; D. E. Ahl; B. E. Ewers; S. Samanta; S. T. Gower; S. N. Burrows

2003-01-01

233

The controlling of landfill leachate evapotranspiration from soil-plant systems with willow: Salix amygdalina L.  

PubMed

The use of willows (Salix amygdalina L) to manage landfill leachate disposal is an effective and cost-effective method due to the high transpiration ability of the willow plants. A 2-year lysimetric experiment was performed to determine an optimum leachate hydraulic loading rate to achieve high evapotranspiration but exert no harmful influence on the plants. The evapotranspiration rate of a soil-plant system planted with the willow was 1.28-5.12-fold higher than the rate measured on a soil surface lacking vegetation, suggesting that soil-willow systems with high volatilization rates are a viable landfill leachate treatment method. Of the soil-willow systems, the one with willow growing on sand amended with sewage sludge soil at an hydraulic loading rate of 1 mm day(-1) performed best, with evapotranspiration ranging from 2.25 to 3.02 mm day(-1) and a biomass yield of 8.0-9.85 Mg dry matter ha(-1). The organic fraction of the soil increased as much as 2.5% of dry matter, due to the sewage sludge input, which exerted a positive effect on the biomass yield as well as on transpiration and evaporation. It was observed that the plants in the sand-and-sewage sludge soil systems displayed higher resistance to toxic effects from the applied landfill leachate relative to plants in the sand-soil systems. PMID:17346008

Bia?owiec, Andrzej; Wojnowska-Bary?a, Irena; Hasso-Agopsowicz, Marek

2007-02-01

234

Physiological Effects of Water Stress on Young Corn Plants.  

National Technical Information Service (NTIS)

Laboratory experiments were used to investigate the mechanism of plant response to water stress by determining the sensitivity of leaf elongation, photosynthesis and transpiration in young corn plants to a decrease in leaf water potential. The sensitivity...

E. W. R. Barlow

1974-01-01

235

Improved growth, productivity and quality of tomato (Solanum lycopersicum L.) plants through application of shikimic acid  

PubMed Central

A field experiment was conducted to investigate the effect of seed presoaking of shikimic acid (30, 60 and 120 ppm) on growth parameters, fruit productivity and quality, transpiration rate, photosynthetic pigments and some mineral nutrition contents of tomato plants. Shikimic acid at all concentrations significantly increased fresh and dry weights, fruit number, average fresh and dry fruit yield, vitamin C, lycopene, carotenoid contents, total acidity and fruit total soluble sugars of tomato plants when compared to control plants. Seed pretreatment with shikimic acid at various doses induces a significant increase in total leaf conductivity, transpiration rate and photosynthetic pigments (Chl. a, chl. b and carotenoids) of tomato plants. Furthermore, shikimic acid at various doses applied significantly increased the concentration of nitrogen, phosphorus and potassium in tomato leaves as compared to control non-treated tomato plants. Among all doses of shikimic acid treatment, it was found that 60 ppm treatment caused a marked increase in growth, fruit productivity and quality and most studied parameters of tomato plants when compared to other treatments. On the other hand, no significant differences were observed in total photosynthetic pigments, concentrations of nitrogen and potassium in leaves of tomato plants treated with 30 ppm of shikimic acid and control plants. According to these results, it could be suggested that shikimic acid used for seed soaking could be used for increasing growth, fruit productivity and quality of tomato plants growing under field conditions.

Al-Amri, Salem M.

2013-01-01

236

Conservatism and diversification of plant functional traits: Evolutionary rates versus phylogenetic signal  

PubMed Central

The concepts of niche conservatism and adaptive radiation have played central roles in the study of evolution and ecological diversification. With respect to phenotypic evolution, the two processes may be seen as opposite ends of a spectrum; however, there is no straightforward method for the comparative analysis of trait evolution that will identify these contrasting scenarios. Analysis of the rate of phenotypic evolution plays an important role in this context and merits increased attention. In this article, independent contrasts are used to estimate rates of evolution for continuous traits under a Brownian motion model of evolution. A unit for the rate of phenotypic diversification is introduced: the felsen, in honor of J. Felsenstein, is defined as an increase of one unit per million years in the variance among sister taxa of ln-transformed trait values. The use of a standardized unit of measurement facilitates comparisons among clades and traits. Rates of diversification of three functional traits (plant height, leaf size, and seed size) were estimated for four to six woody plant clades (Acer, Aesculus, Ceanothus, Arbutoideae, Hawaiian lobeliads, and the silversword alliance) for which calibrated phylogenies were available. For height and leaf size, rates were two to ?300 times greater in the Hawaiian silversword alliance than in the other clades considered. These results highlight the value of direct estimates of rates of trait evolution for comparative analysis of adaptive radiation, niche conservatism, and trait diversification.

Ackerly, David

2009-01-01

237

Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone.  

PubMed

The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flow rates and tracer concentrations at wetland inflows and outflows. We used two ideal reactor model solutions, a continuous flow stirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these non-ideal agricultural wetlands in which check ponds are in series. Using a flux model, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment-water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemical mechanisms affecting dissolved constituent cycling in the root zone. In addition, our understanding of internal root zone cycling of Hg and other dissolved constituents, benthic fluxes, and biological irrigation may be greatly affected. PMID:24296049

Bachand, P A M; Bachand, S; Fleck, J; Anderson, F; Windham-Myers, L

2014-06-15

238

Thermal simulation and economic assessment of unglazed transpired collector systems  

SciTech Connect

Unglazed transpired collectors (UTCs) have recently emerged as a new solar air heating technology. They are relatively inexpensive, efficient, and particularly suited to applications in which a high outdoor air requirement must be met. A TRNSYS model has been created for UTC systems. Annual simulations are performed for several representative buildings. The statewide economic potential of UTC systems is assessed for Wisconsin. UTC systems on existing buildings are competitive with electric heating systems but not with gas or oil heating. Electric heating is not widely used in most buildings that are well-suited for UTC systems, with the exception of large apartment buildings. Therefore, there is no significant statewide economic potential for retrofit of UTC systems on existing buildings except in the residential sector. However, UTC systems are cost effective for new buildings because their low first cost allows them to compete with gas and oil heating.

Summers, D.N.; Mitchell, J.W.; Klein, S.A.; Beckman, W.A.

1996-10-01

239

Boron mobility in plants  

Microsoft Academic Search

In the majority of plant species, B distribution between plant organs and the symptoms of B deficiency and toxicity indicate that B has restricted mobility. Nevertheless, B is present in phloem and is retranslocated in phloem, often in sufficient amounts to satisfy the demands of developing sink regions that do not readily transpire. In species that produce significant amounts of

Barry J. Shelp; Eduardo Marentes; Alice M. Kitheka; Pathmanathan Vivekanandan

1995-01-01

240

Boron mobility in plants  

Microsoft Academic Search

In the majority of plant species, B distribution between plant organs and the symptoms of B deficiency and toxicity indicate that B has restricted mobility. Nevertheless, B is present in phloem and is retranslocated in phloem, often in sufficient amounts to satisfy the demands of developing sink regions that do not readily transpire. In species that produce significant amounts of

Patrick H. Brown; Barry J. Shelp

1997-01-01

241

The effect of temperature on the rate of cyanide metabolism of two woody plants  

Microsoft Academic Search

The response of cyanide metabolism rates of two woody plants to changes in temperature is investigated. Detached leaves (1.0g fresh weight) from weeping willow (Salix babylonica L.) and Chinese elder (Sambucus chinensis Lindl.) were kept in glass vessels with 100ml of aqueous solution spiked with potassium cyanide for a maximum of 28h. Ten different temperatures were used ranging from 11°C

Xiaozhang Yu; Stefan Trapp; Puhua Zhou; Hao Hu

2005-01-01

242

Hazard rating of ash and slag dumps of thermal power plants firing Kuznetskii coal  

SciTech Connect

Results of a study of the degree of toxicity and of the hazard rating of ash and slag waste due to firing Kuznetskii coals at thermal power plants are presented. Computation shows and biological tests prove that the waste belongs to the fifth hazard class, i.e., is virtually safe. Comparison of the results obtained with foreign data shows that the waste in question belongs to the safe category in accordance with foreign standards as well.

E.P. Dik; A.N. Soboleva [All-Russia Thermal Engineering Institute (VTI), Moscow (Russian Federation)

2006-03-15

243

Photosynthesis in intact leaves of C 3 plants: Physics, physiology and rate limitations  

Microsoft Academic Search

The instantaneous rate of photosynthetic CO2 assimilation in C3 plants has generally been studied in model systems such as isolated chloroplasts and algae. From these studies and from theoretical\\u000a analyses of gas exchange behavior it is now possible to study the biochemistry of photosynthesis in intact leaves using a\\u000a combination of methods, most of which are nondestructive.\\u000a \\u000a The limitations to

Thomas D. Sharkey

1985-01-01

244

Extinction rate estimates for plant populations in revisitation studies: Importance of detectability  

USGS Publications Warehouse

Many researchers have obtained extinction-rate estimates for plant populations by comparing historical and current records of occurrence. A population that is no longer found is assumed to have gone extinct. Extinction can then be related to characteristics of these populations, such as habitat type, size, or species, to test ideas about what factors may affect extinction. Such studies neglect the fact that a population may be overlooked, however, which may bias estimates of extinction rates upward. In addition, if populations are unequally detectable across groups to be compared, such as habitat type or population size, comparisons become distorted to an unknown degree. To illustrate the problem, I simulated two data sets, assuming a constant extinction rate, in which populations occurred in different habitats or habitats of different size and these factors affected their detectability The conventional analysis implicitly assumed that detectability equalled 1 and used logistic regression to estimate extinction rates. It wrongly identified habitat and population size as factors affecting extinction risk. In contrast, with capture-recapture methods, unbiased estimates of extinction rates were recovered. I argue that capture-recapture methods should be considered more often in estimations of demographic parameters in plant populations and communities.

Kery, M.

2004-01-01

245

Measured isoprene emission rates of plants in California landscapes: comparison to estimates from taxonomic relationships  

NASA Astrophysics Data System (ADS)

Isoprene emission rates of 64 plant species found in California's urban and natural landscapes were measured using a dynamic flow-through chamber enclosure technique. Species were selected to provide data for previously unmeasured species and to test estimates of isoprene emission rates based upon taxonomic relationships developed for compilation of biogenic emission inventories as proposed by Benjamin et al. (1996, Atmospheric Environment 30, 1437-1452) . Branch-level isoprene emission rates ranged from undetectable for 47 species, to 54 ?g g -1 h -1 for Quercus kelloggii, California black oak. Isoprene emission rate estimates based on taxonomy agreed well with our measurements for species within the same genus, with the exception of the Quercus genus for which a wide range of isoprene emission rates have been reported. As expected, family-level estimates based on taxonomy showed greater deviation from our measured values than did genus-based estimates. The data developed in the present study support use of a taxonomic predictive methodology, especially if previous measurements within specific families, sub-families, and genera are extensive, and the results of such assignment are treated with proper caution. A taxonomic approach may be most useful where plant species in natural and urban landscapes are numerous, such as in California, where no experimental measurements are available for thousands of species.

Karlik, John F.; Winer, Arthur M.

246

Bisphenol A emission factors from industrial sources and elimination rates in a sewage treatment plant.  

PubMed

Bisphenol A (BPA) is widely used for the production of epoxy resins and polycarbonate plastics and is considered an endocrine disruptor. Special in vitro test systems and animal experiments showed a weak estrogenic activity. Aquatic wildlife especially could be endangered by waste water discharges. To manage possible risks arising from BPA emissions the major fluxes need to be investigated and the sources of the contamination of municipal treatment plants need to be determined. In this study, five major industrial point sources, two different household areas and the influent and effluent of the corresponding treatment plant (WWTP) were monitored simultaneously at a plant serving 120,000 population equivalents. A paper producing plant was the major BPA contributor to the influent load of the wastewater treatment plant. All the other emissions from point sources, including the two household areas, were considerably lower. The minimum elimination rate in the WTTP could be determined at 78% with an average of 89% of the total BPA-load. For a possible pollution-forecast, or for a comparison between different point sources, emission factors based on COD-emissions were calculated for industrial and household point sources at BPA/COD-ratios between 1.4 x 10(-8) - 125 x 10(-8) and 1.3 x 10(-6) - 6.3 x 10(-6), respectively. PMID:12862225

Fuerhacker, M

2003-01-01

247

Enhanced IGCC regulatory control and coordinated plant-wide control strategies for improving power ramp rates  

SciTech Connect

As part of ongoing R&D activities at the National Energy Technology Laboratory’s (NETL) Advanced Virtual Energy Simulation Training & Research (AVESTAR™) Center, this paper highlights strategies for enhancing low-level regulatory control and system-wide coordinated control strategies implemented in a high-fidelity dynamic simulator for an Integrated Gasification Combined Cycle (IGCC) power plant with carbon capture. The underlying IGCC plant dynamic model contains 20 major process areas, each of which is tightly integrated with the rest of the power plant, making individual functionally-independent processes prone to routine disturbances. Single-loop feedback control although adequate to meet the primary control objective for most processes, does not take into account in advance the effect of these disturbances, making the entire power plant undergo large offshoots and/or oscillations before the feedback action has an opportunity to impact control performance. In this paper, controller enhancements ranging from retuning feedback control loops, multiplicative feed-forward control and other control techniques such as split-range control, feedback trim and dynamic compensation, applicable on various subsections of the integrated IGCC plant, have been highlighted and improvements in control responses have been given. Compared to using classical feedback-based control structure, the enhanced IGCC regulatory control architecture reduces plant settling time and peak offshoots, achieves faster disturbance rejection, and promotes higher power ramp-rates. In addition, improvements in IGCC coordinated plant-wide control strategies for “Gasifier-Lead”, “GT-Lead” and “Plantwide” operation modes have been proposed and their responses compared. The paper is concluded with a brief discussion on the potential IGCC controller improvements resulting from using advanced process control, including model predictive control (MPC), as a supervisory control layer.

Mahapatra, P.; Zitney, S.

2012-01-01

248

Estimates of deep drainage rates at the U.S. Department of Energy Pantex Plant, Amarillo, Texas  

Microsoft Academic Search

In FY 1996, the Pacific Northwest National Laboratory (PNNL) provided technical assistance to Battelle Columbus Operations (BCO) in their ongoing assessment of contaminant migration at the Pantex Plant in Amarillo, Texas. The objective of this report is to calculate deep drainage rates at the Pantex Plant. These deep drainage rates may eventually be used to predict contaminant loading to the

M. J. Fayer; M. C. Richmond; M. S. Wigmosta; M. E. Kelley

1998-01-01

249

Supplementary documentation for an Environmental Impact Statement regarding the Pantex Plant: a comparison of county and state cancer mortality rates  

Microsoft Academic Search

This report documents work performed in support of preparation of an Environmental Impact Statement (EIS) regarding the Department of Energy's Pantex Plant near Amarillo, Texas. This report considers cancer mortality rates in the region surrounding the Pantex nuclear weapons facility. The working hypothesis was that increased cancer mortality rates would exist in counties proximal to the Pantex Plant. To evaluate

L. D. Wiggs; G. S. Wilkinson; G. L. Tietjen; J. F. Acquavella

1982-01-01

250

Life history influences rates of climatic niche evolution in flowering plants  

PubMed Central

Across angiosperms, variable rates of molecular substitution are linked with life-history attributes associated with woody and herbaceous growth forms. As the number of generations per unit time is correlated with molecular substitution rates, it is expected that rates of phenotypic evolution would also be influenced by differences in generation times. Here, we make the first broad-scale comparison of growth-form-dependent rates of niche evolution. We examined the climatic niches of species on large time-calibrated phylogenies of five angiosperm clades and found that woody lineages have accumulated fewer changes per million years in climatic niche space than related herbaceous lineages. Also, climate space explored by woody lineages is consistently smaller than sister lineages composed mainly of herbaceous taxa. This pattern is probably linked to differences in the rate of climatic niche evolution. These results have implications for niche conservatism; in particular, the role of niche conservatism in the distribution of plant biodiversity. The consistent differences in the rate of climatic niche evolution also emphasize the need to incorporate models of phenotypic evolution that allow for rate heterogeneity when examining large datasets.

Smith, Stephen A.; Beaulieu, Jeremy M.

2009-01-01

251

Island radiation on a continental scale: Exceptional rates of plant diversification after uplift of the Andes  

PubMed Central

Species radiations provide unique insights into evolutionary processes underlying species diversification and patterns of biodiversity. To compare plant diversification over a similar time period to the recent cichlid fish radiations, which are an order of magnitude faster than documented bird, arthropod, and plant radiations, we focus on the high-altitude flora of the Andes, which is the most species-rich of any tropical mountains. Because of the recent uplift of the northern Andes, the upland environments where much of this rich endemic flora is found have been available for colonization only since the late Pliocene or Pleistocene, 2–4 million years (Myr) ago. Using DNA sequence data we identify a monophyletic group within the genus Lupinus representing 81 species endemic to the Andes. The age of this clade is estimated to be 1.18–1.76 Myr, implying a diversification rate of 2.49–3.72 species per Myr. This exceeds previous estimates for plants, providing the most spectacular example of explosive plant species diversification documented to date. Furthermore, it suggests that the high cichlid diversification rates are not unique. Lack of key innovations associated with the Andean Lupinus clade suggests that diversification was driven by ecological opportunities afforded by the emergence of island-like habitats after Andean uplift. Data from other genera indicate that lupines are one of a set of similarly rapid Andean plant radiations, continental in scale and island-like in stimulus, suggesting that the high-elevation Andean flora provides a system that rivals other groups, including cichlids, for understanding rapid species diversification.

Hughes, Colin; Eastwood, Ruth

2006-01-01

252

Importance of precipitation partitioning into vaporization and deep percolation in estimation of evaporation and transpiration  

NASA Astrophysics Data System (ADS)

Evaporation and Transpiration are two important fluxes in the hydrological cycle. Different approaches exist to estimate it as a function of land cover/land use, soil moisture content and atmospheric forcing. We here compare two approaches: ETLook wherein evaporation and transpiration is controlled by AMSRE derived soil moisture induced stress and a Simple Evaporation Transpiration Scheme (SETS) that has similar evaporation and transpiration formulation as ETLook without AMSRE derived soil moisture control but with explicit subsurface soil moisture accounting (and including thus derived soil moisture induced stress). The central question addressed here is whether satellite observation based soil moisture provides a credible control on evaporation and transpiration when explicit subsurface soil moisture accounting, which governs partitioning of precipitation into vaporization and percolation, is absent. We apply the two schemes at daily time scale for the year 2007 for Indus River Basin in Pakistan and India at 1km x 1km spatial resolution. SETS is forced by TRMM precipitation data series and has simpler representation of irrigation. All other data sets and parameter values are same between the two methods. Results show that SETS has a tendency to underpredict ETLook in both evaporation and transpiration. Since evaporation and transpiration schemes are same in both, the differences between the two can only be due to use of TRMM data sets, poorer representation irrigation or explicit representation of subsurface hydrology in SETS. In this study we suggest that explicit subsurface soil moisture accounting plays a major role in explaining the difference between the two.

Ghazanfari, S.; Pande, S.; Cheema, M.; Bastiaanssen, W.; Savenije, H.

2011-12-01

253

Exploring the importance of within-canopy spatial temperature variation on transpiration predictions  

PubMed Central

Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale in climatically contrasting genotypes of Acer rubrum L., cv. October Glory (OG) and Summer Red (SR). The effects of temperature acclimation on intracanopy gradients in transpiration over a range of realistic forest growth temperatures were also assessed by simulation. Physiological parameters were applied, with or without adjustment for temperature acclimation, to account for transpiration responses to growth temperature. Both types of parameterization were scaled up to stand transpiration (expressed per unit leaf area) with an individual tree model (MAESTRA) to assess how transpiration might be affected by spatial and temporal distributions of foliage properties. The MAESTRA model performed well, but its reproducibility was dependent on physiological parameters acclimated to daytime temperature. Concordance correlation coefficients between measured and predicted transpiration were higher (0.95 and 0.98 versus 0.87 and 0.96) when model parameters reflected acclimated growth temperature. In response to temperature increases, the southern genotype (SR) transpiration responded more than the northern (OG). Conditions of elevated long-term temperature acclimation further separate their transpiration differences. Results demonstrate the importance of accounting for leaf-level physiological adjustments that are sensitive to microclimate changes and the use of provenance-, ecotype-, and/or genotype-specific parameter sets, two components likely to improve the accuracy of site-level and ecosystem-level estimates of transpiration flux.

Bauerle, William L.; Bowden, Joseph D.; Wang, G. Geoff; Shahba, Mohamed A.

2009-01-01

254

Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates  

SciTech Connect

Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g{sup -1} soil) to soils amended with and without {sup 13}C-labeled plant residue. We measured CO{sub 2} respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g{sup -1}) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g{sup -1}) had no impact on plant residue decomposition, while greater concentrations of C (> 7.2 mg C g{sup -1}) reduced decomposition (-50%). Concurrently, high exudate concentrations (> 3.6 mg C g{sup -1}) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (< 3.6 mg C g{sup -1}) increased metabolic activity rather than gene copy numbers. These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria.

De Graaff, Marie-Anne [ORNL; Classen, Aimee T [University of Tennessee, Knoxville (UTK); Castro Gonzalez, Hector F [ORNL; Schadt, Christopher Warren [ORNL

2010-01-01

255

Strobilurin fungicides induce changes in photosynthetic gas exchange that do not improve water use efficiency of plants grown under conditions of water stress.  

PubMed

The effects of five strobilurin (beta-methoxyacrylate) fungicides and one triazole fungicide on the physiological parameters of well-watered or water-stressed wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and soya (Glycine max Merr.) plants were compared. Water use efficiency (WUE) (the ratio of rate of transpiration, E, to net rate of photosynthesis, A(n)) of well-watered wheat plants was improved slightly by strobilurin fungicides, but was reduced in water-stressed plants, so there is limited scope for using strobilurins to improve the water status of crops grown under conditions of drought. The different strobilurin fungicides had similar effects on plant physiology but differed in persistence and potency. When applied to whole plants using a spray gun, they reduced the conductance of water through the epidermis (stomatal and cuticular transpiration), g(sw), of leaves. Concomitantly, leaves of treated plants had a lower rate of transpiration, E, a lower intercellular carbon dioxide concentration, c(i), and a lower net rate of photosynthesis, A(n), compared with leaves of control plants or plants treated with the triazole. The mechanism for the photosynthetic effects is not known, but it is hypothesised that they are caused either by strobilurin fungicides acting directly on ATP production in guard cell mitochondria or by stomata responding to strobilurin-induced changes in mesophyll photosynthesis. The latter may be important since, for leaves of soya plants, the chlorophyll fluorescence parameter F(v)/F(m) (an indication of the potential quantum efficiency of PSII photochemistry) was reduced by strobilurin fungicides. It is likely that the response of stomata to strobilurin fungicides is complex, and further research is required to elucidate the different biochemical pathways involved. PMID:17912684

Nason, Mark A; Farrar, John; Bartlett, David

2007-12-01

256

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation  

NASA Astrophysics Data System (ADS)

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation is studied on the basis of kinetic theory. We consider the situation in which the Knudsen number (the mean free path divided by the characteristic length of the cross section) is small and the dimensionless gravity (the characteristic length divided by the ascent height of the molecules against gravity) is of the order of the square of the Knudsen number. The behavior of the gas is studied analytically on the basis of the fluid-dynamic-type equation and the slip-type boundary condition derived from the Boltzmann equation for small Knudsen numbers. Extending the analysis of the two-dimensional channel problem, the solution for a pipe with an arbitrary cross section is obtained in a semianalytical form. When the temperature gradient is imposed along the pipe, the pressure gradient is produced not only in the vertical direction but also in the horizontal direction due to the effect of gravity. Although this pressure gradient is of the order of the square of the Knudsen number, it induces a flow of the order of the Knudsen number. As a result, the apparently higher order effect of gravity produces a relatively finite effect on thermal transpiration. This phenomenon, first observed in plane thermal transpiration, is clarified for a pipe with a general cross section. The explicit solution is obtained for the pipe with the cross section of an annulus between eccentric circular cylinders. Based on the solution, the effect of weak gravitation on the mass flow rate of the gas, as well as on the flow velocity, is clarified over a wide range of the radii ratio and the eccentricity of the cylinders.

Doi, Toshiyuki

2013-10-01

257

Variation in decomposition rates in the fynbos biome, South Africa: the role of plant species and plant stoichiometry  

PubMed Central

Previous studies in the fynbos biome of the Western Cape, South Africa, have suggested that biological decomposition rates in the fynbos vegetation type, on poor soils, may be so low that fire is the main factor contributing to litter breakdown and nutrient release. However, the fynbos biome also comprises vegetation types on more fertile soils, such as the renosterveld. The latter is defined by the shrub Elytropappus rhinocerotis, while the shrub Galenia africana may become dominant in overgrazed areas. We examined decomposition of litter of these two species and the geophyte Watsonia borbonica in patches of renosterveld in an agricultural landscape. In particular, we sought to understand how plant species identity affects litter decomposition rates, especially through variation in litter stoichiometry. Decomposition (organic matter mass loss) varied greatly among the species, and was related to litter N and P content. G. africana, with highest nutrient content, lost 65% of its original mass after 180 days, while E. rhinocerotis had lost ca. 30%, and the very nutrient poor W. borbonica <10%. Litter placed under G. africana decomposed slightly faster than when placed under E. rhinocerotis. Over the course of the experiment, G. africana and E. rhinocerotis lost N and P, while W. borbonica showed strong accumulation of these elements. Decomposition rates of G. africana and E. rhinocerotis were substantially higher than those previously reported from fynbos vegetation, and variation among the species investigated was considerable. Our results suggest that fire may not always be the main factor contributing to litter breakdown and nutrient release in the fynbos biome. Thus, biological decomposition has likely been underestimated and, along with small-scale variation in ecosystem processes, would repay further study. Electronic supplementary material The online version of this article (doi:10.1007/s00442-010-1753-7) contains supplementary material, which is available to authorized users.

Janion, Charlene; Chown, Steven L.; Leinaas, Hans Petter

2010-01-01

258

Yield and gas exchange ability of sweetpotato plants cultured in a hydroponic system  

NASA Astrophysics Data System (ADS)

Life support of crews in space is greatly dependent on the amounts of food atmospheric O 2 and clean water produced by plants Therefore the space farming systems with scheduling of crop production obtaining high yields with a rapid turnover rate converting atmospheric CO 2 to O 2 and purifying water should be established with employing suitable plant species and varieties and precisely controlling environmental variables around plants grown at a high density in a limited space In this study three sweetpotato varieties were cultured in a newly developed hydroponic system and the yield the photosynthetic rate and the transpiration rate were compared on the earth as a fundamental study for establishing the space farming systems The varieties were Elegant summer Koukei 14 and Beniazuma The hydroponic system mainly consisted of water channels and rockwool boards A growing space for roots was made between the rockwool board and nutrient solution in the water channel Storage roots were developed on the lower surface of the rockwool plates Fresh weights of the storage roots were 1 6 1 2 and 0 6 kg plant for Koukei 14 Elegant summer and Beniazuma respectively grown for five months from June to October under the sun light in Osaka Japan Koukei 14 and Elegant summer produced greater total phytomass than Beniazuma There were positive correlations among the total phytomass the net photosynthetic rate and the transpiration rate Young stems and leaves as well as storage roots of Elegant summer are edible Therefore Elegant-summer

Kitaya, Y.; Hirai, H.; Saiful Islam, A. F. M.; Yamamoto, M.

259

Transpirational water use and its regulation in the mountainous terrain of S. Korea  

NASA Astrophysics Data System (ADS)

Quantifying water use by forests growing on complex mountainous terrain is difficult and understanding of controls on water use by these forests a challenge. Yet mountains are crucial as water towers and better understanding of their hydrology and ecology is critical for sustainable management. Consequently, there is a growing need for new research approaches designed with attention to the particular needs and constraints of large-scale studies and that have the potential to generate reliable and accurate data. The use of a combination of different sapflow-measurement techniques provides a unique opportunity to monitor water use by the understory and canopy forest tree species at micro-scale, allowing for accurate estimation of total forest water use. The obtained data, in conjunction with intensively measured climatic variables, allow for better understanding and interpretation of transpiration results. A research initiative under the International Training Group: Complex Terrain and Ecological Heterogeneity (TERRECO) seeks to address pertinent issues related to forest water use and production in complex terrain. Stem Heat balance (SHB) and Heat Dissipation techniques have been employed to measure sapflow in the understory woody plants and tree branches and on stems of canopy trees respectively. Measurements have been stratified to account for differences in tree sizes and species diversity. To better understand the data, we are intensively monitoring soil moisture at 5, 10 and 30 cm depths, in addition to a range of micrometeorology sensors that have been set up below, within and above the canopy. These measurements have been planned, taking into account altitudinal/elevation gradient, aspect and within site differences in species composition and tree sizes and to generate data for large-scale modeling of the entire catchment. A total of 70 trees from 9 species growing in six different locations at varying elevations and aspects are being monitored. Peak daily water use by trees during mid summer amounts to 45 kg d-1 but varies significantly with sapwood area. Within a species, there is a consistent relationship between tree size (DBH) and sapwood area irrespective of elevation. We have also established a common trend in the relationship between wood density and sap flux density (Js) that transcends the boundaries of species differences. These initial findings are critical for our planned upscaling of water use by the forest catchment. In addition to soil moisture, vapor pressure deficit (VPD) and light play a crucial regulatory role on forest water use. We are at the stage of establishing a common link that brings together micrometeorology and transpiration that will allow for large scale modeling of forest water use.

Otieno Dennis, O.; Eunyoung, J.; Sinkyu, K.; Tenhunen, J. D.

2009-12-01

260

Penman–Monteith reference evapotranspiration adapted to estimate irrigated tree transpiration  

Microsoft Academic Search

The Penman–Monteith equation as parameterized by the FAO-56 bulletin to compute grass reference evapotranspiration (E0, Lgroundm?2d?1) was used to predict transpiration of irrigated orchard apple trees, olives, grapevines, kiwifruit and an isolated walnut tree. Sap flow (S, Lplant?1d?1) measured by the compensation heat-pulse technique was taken as the tree transpiration on a daily time scale, and it proved to be

Antonio Roberto Pereira; Steve Green; Nilson Augusto Villa Nova

2006-01-01

261

Evaluation of transpiration in adult apricot trees from sap flow measurements  

Microsoft Academic Search

The aim of this study was to assess the accuracy of transpiration measurements obtained using the compensation heat-pulse compared with the transpiration estimated using the soil water balance. The experiment was carried out with 11-year-old apricot trees (Prunus armeniaca L. cv. Bulida, grafted onto Real Fino apricot rootstock) growing in a commercial orchard located in south-eastern Spain under different irrigation

E. Nicolas; A. Torrecillas; M. F. Ortuño; R. Domingo; J. J. Alarcón

2005-01-01

262

Transpiration of a 64-year-old maritime pine stand in Portugal  

Microsoft Academic Search

The transpiration, sap flow, stomatal conductance and water relations ofPinus pinaster were determined during spring and summer in a 64-year-old stand in Ribatejo (Portugal). The transpiration of the pine canopy was determined from sap flow or eddy covariance techniques. Canopy conductance values (gc) were estimated from inversion methods using eddy covariance or sap flow data, respectively, and from scaling-up methods

D. Loustau; P. Berbigier; P. Roumagnac; C. Arruda-Pacheco; J. S. David; M. I. Ferreira; J. S. Pereira; R. Tavares

1996-01-01

263

A Plant Notices Insect Egg Deposition and Changes Its Rate of Photosynthesis1  

PubMed Central

Scots pine (Pinus sylvestris) is known to change its terpenoid metabolism in response to egg deposition by the sawfly Diprion pini (Hymenoptera, Diprionidae). Three days after egg deposition, parts of the pine twig adjacent to the egg-laden one are induced to emit volatiles, which attract egg parasitoids. In this study, we investigated whether egg deposition by this sawfly affects pine photosynthesis. Measurements of photosynthesis were taken from untreated control twigs and from pine twigs adjacent to egg-laden ones (i.e. systemically oviposition-induced twigs) for a period of 3 d starting after egg deposition. The net photosynthetic rate of oviposition-induced pine twigs was lower than that of untreated control twigs, whereas the respiration rate of pine twigs was not affected by egg deposition. CO2 response curves of oviposition-induced twigs tended to be lower than those of controls. The potential rate of electron transport (Jmax) and the maximum rate of Rubisco activity (Vcmax) were calculated from the data of the CO2 response curves. Jmax of oviposition-induced twigs was significantly lower than that of controls at day 1 after egg deposition, while the difference diminished from day 2 to day 3. A similar pattern was observed for Vcmax. Light response curves of oviposition-induced twigs were significantly lower than those of untreated ones during 3 d of measurements. Stomatal conductance was slightly lowered by egg deposition. When considering photosynthetic activity as a physiological currency to measure costs of induction of plant defense, the effects of insect egg deposition on gas exchange of pine are discussed with respect to known effects of insect feeding on the photosynthesis activity of plants.

Schroder, Roland; Forstreuter, Manfred; Hilker, Monika

2005-01-01

264

Evaluating the Performance and Economics of Transpired Solar Collectors for Commercial Applications: Preprint  

SciTech Connect

Using transpired solar collectors to preheat ventilation air has recently become recognized as an economic alternative for integrating renewable energy into commercial buildings in heating climates. The collectors have relatively low installed costs and operate on simple principles. Theory and performance testing have shown that solar collection efficiency can exceed 70% of incident solar. However, implementation and current absorber designs have adversely affected the efficiency and associated economics from this initial analysis. The National Renewable Energy Laboratory has actively studied this technology and monitored performance at several installations. A calibrated model that uses typical meteorological weather data to determine absorber plate efficiency resulted from this work. With this model, an economic analysis across heating climates was done to show the effects of collector size, tilt, azimuth, and absorptivity. The analysis relates the internal rate of return of a system based on the cost of the installed absorber area. In general, colder and higher latitude climates return a higher rate of return because the heating season extends into months with good solar resource.

Kozubal, E.; Deru, M.; Slayzak, S.; Norton, P.; Barker, G.; McClendon, J,

2008-07-01

265

Risk-taking plants: anisohydric behavior as a stress-resistance trait.  

PubMed

Water scarcity is a critical limitation for agricultural systems. Two different water management strategies have evolved in plants: an isohydric strategy and an anisohydric strategy. Isohydric plants maintain a constant midday leaf water potential (?leaf) when water is abundant, as well as under drought conditions, by reducing stomatal conductance as necessary to limit transpiration. Anisohydric plants have more variable ?leaf and keep their stomata open and photosynthetic rates high for longer periods, even in the presence of decreasing leaf water potential. This risk-taking behavior of anisohydric plants might be beneficial when water is abundant, as well as under moderately stressful conditions. However, under conditions of intense drought, this behavior might endanger the plant. We will discuss the advantages and disadvantages of these two water-usage strategies and their effects on the plant's ability to tolerate abiotic and biotic stress. The involvement of plant tonoplast AQPs in this process will also be discussed. PMID:22751307

Sade, Nir; Gebremedhin, Alem; Moshelion, Menachem

2012-07-01

266

What determines the complex kinetics of stomatal conductance under blueless PAR in Festuca arundinacea? Subsequent effects on leaf transpiration  

PubMed Central

Light quality and, in particular, its content of blue light is involved in plant functioning and morphogenesis. Blue light variation frequently occurs within a stand as shaded zones are characterized by a simultaneous decrease of PAR and blue light levels which both affect plant functioning, for example, gas exchange. However, little is known about the effects of low blue light itself on gas exchange. The aims of the present study were (i) to characterize stomatal behaviour in Festuca arundinacea leaves through leaf gas exchange measurements in response to a sudden reduction in blue light, and (ii) to test the putative role of Ci on blue light gas exchange responses. An infrared gas analyser (IRGA) was used with light transmission filters to study stomatal conductance (gs), transpiration (Tr), assimilation (A), and intercellular concentration of CO2 (Ci) responses to blueless PAR (1.80 ?mol m?2 s?1). The results were compared with those obtained under a neutral filter supplying a similar photosynthetic efficiency to the blueless PAR filter. It was shown that the reduction of blue light triggered a drastic and instantaneous decrease of gs by 43.2% and of Tr by 40.0%, but a gradual stomatal reopening began 20 min after the start of the low blue light treatment, thus leading to new steady-states. This new stomatal equilibrium was supposed to be related to Ci. The results were confirmed in more developed plants although they exhibited delayed and less marked responses. It is concluded that stomatal responses to blue light could play a key role in photomorphogenetic mechanisms through their effect on transpiration.

Barillot, Romain; Frak, Ela; Combes, Didier; Durand, Jean-Louis; Escobar-Gutierrez, Abraham J.

2010-01-01

267

How do soil texture, plant community composition and earthworms affected the infiltration rate in a grassland plant diversity experiment depending on season?  

NASA Astrophysics Data System (ADS)

Background and aims: In this study we analyzed the influences of plant community characteristics, soil texture and earthworm presence on infiltration rates on a managed grassland plant diversity experiment assessing the role of biotic and abiotic factors on soil hydrology. Methods: We measured infiltration using a hood infiltrometer in subplots with ambient and reduced earthworm density (earthworm extraction) nested in plots of different plant species richness (1, 4, and 16), plant functional group number and composition (1 to 4; legumes, grasses, small herbs, tall herbs) in early summer (June) and autumn (September, October) 2011. Results: The presence of certain plant functional groups such as grasses and legumes influenced infiltration rates and this effect enhanced during the growing season. Infiltration was significantly higher in plots containing legumes than in plots without, and it was significantly lower in the presence of grasses than in their absence. In early summer, earthworm presence and biomass increased the infiltration rates, independently of plant species richness. In October, plant species richness only affected infiltration rates in reduced earthworm plots. At the end of the growing season earthworm populations were negatively influenced by grasses and positively by legumes. In September, infiltration rates were positive related to the proportion of finer grains. The correlation disappears when removing all plots containing legumes from the sample. For all measurements the infiltration rates decreases from early summer to autumn at the matric potentials at pressure zero and -0.02 m, but not for smaller macropores at matric potentials -0.04 and -0.06m. Conclusions: Considering infiltration rates as ecosystem function, this function will largely depend on the ecosystem composition and season, not on biodiversity per se. Our results indicate that biotic factors are of overriding influence for shaping infiltration rates mainly for larger macropores, and should be taken into account in hydrological applications.

Fischer, Christine; Britta, Merkel; Nico, Eisenhauer; Christiane, Roscher; Sabine, Attinger; Stefan, Scheu; Anke, Hildebrandt

2013-04-01

268

Modelling the effect of low soil temperatures on transpiration by Scots pine  

NASA Astrophysics Data System (ADS)

For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring-early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70-year-old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high-latitude stands.

Mellander, Per-Erik; Stähli, Manfred; Gustafsson, David; Bishop, Kevin

2006-06-01

269

Cyclic variations in nitrogen uptake rate of soybean plants: effects of external nitrate concentration  

NASA Technical Reports Server (NTRS)

Net uptake of NO3- by non-nodulated soybean plants [Glycine max (L.) Merr. cv. Ransom] growing in flowing hydroponic cultures containing 0.5, 1.0 and 10.0 mol m-3 NO3- was measured daily during a 24-d period of vegetative development to determine if amplitude of maximum and minimum rates of net NO3- uptake are responsive to external concentrations of NO3-. Removal of NO3- from the replenished solutions during each 24-h period was determined by ion chromatography. Neither dry matter accumulation nor the periodicity of oscillations in net uptake rate was altered by the external NO3- concentrations. The maxima of the oscillations in net uptake rate, however, increased nearly 3-fold in response to external NO3- concentrations. The maxima and minima, respectively, changed from 4.0 and 0.6 mmol NO3- per gram root dry weight per day at an external solution level of 0.5 mol m-3 NO3- to 15.2 and -2.7 mmol NO3- per gram root dry weight per day at an external solution level of 10.0 mol m-3 NO3-. The negative values for minimum net uptake rate from 10.0 mol m-3 NO3- solutions show that net efflux was occurring and indicate that the magnitude of the efflux component of net uptake was responsive to external concentration of NO3-.

Tolley-Henry, L.; Raper, C. D. Jr; Granato, T. C.; Raper CD, J. r. (Principal Investigator)

1988-01-01

270

Testing the Growth Rate Hypothesis in Vascular Plants with Above- and Below-Ground Biomass  

PubMed Central

The growth rate hypothesis (GRH) proposes that higher growth rate (the rate of change in biomass per unit biomass, ?) is associated with higher P concentration and lower C?P and N?P ratios. However, the applicability of the GRH to vascular plants is not well-studied and few studies have been done on belowground biomass. Here we showed that, for aboveground, belowground and total biomass of three study species, ? was positively correlated with N?C under N limitation and positively correlated with P?C under P limitation. However, the N?P ratio was a unimodal function of ?, increasing for small values of ?, reaching a maximum, and then decreasing. The range of variations in ? was positively correlated with variation in C?N?P stoichiometry. Furthermore, ? and C?N?P ranges for aboveground biomass were negatively correlated with those for belowground. Our results confirm the well-known association of growth rate with tissue concentration of the limiting nutrient and provide empirical support for recent theoretical formulations.

Yu, Qiang; Wu, Honghui; He, Nianpeng; Lu, Xiaotao; Wang, Zhiping; Elser, James J.; Wu, Jianguo; Han, Xingguo

2012-01-01

271

Self-sterility in flowering plants: preventing self-fertilization increases family diversification rates  

PubMed Central

Background and Scope New data are presented on the distribution and frequency of self-sterility (SS) – predominantly pre-zygotic self-incompatibility (SI) systems – in flowering plants and the hypothesis is tested that families with self-sterile taxa have higher net diversification rates (DRs) than those with exclusively self-compatible taxa using both absolute and relative rate tests. Key Results Three major forms of SI systems (where pollen is rejected at the stigmatic, stylar or ovarian interface) are found to occur in the oldest families of flowering plants, with times of divergence >100 million years before the present (mybp), while post-fertilization SS and heterostyly appear in families with crown ages of 81 and 87 mybp, respectively. It is also founnd that many (22) angiosperm families exhibit >1 SI phenotype and that the distribution of different types of SS does not show strong phylogenetic clustering, collectively suggesting that SS and SI systems have evolved repeatedly de novo in angiosperm history. Families bearing self-sterile taxa have higher absolute DRs using all available calibrations of the angiosperm tree, and this affect is caused mostly by the high DR of families with homomorphic SI systems (in particular stigmatic SI) or those in which multiple SS/SI phenotypes have been observed (polymorphic). Lastly, using sister comparisons, it is further demonstrated that in 29 of 38 sister pairs (including 95 families), the self-sterile sister group had higher species richness and DR than its self-compatible sister based on either the total number of taxa in the clade with SS or only the estimated fraction to harbour SS based on literature surveys. Conclusions Collectively, these analyses point to the importance of SS, particularly pre-zygotic SI in the evolution of flowering plants.

Ferrer, Miriam M.; Good, Sara V.

2012-01-01

272

Evaluation of Ability to Determine Transpiration Fraction from Stable Water Isotopes by Synthesis of Models and Observations in an Alpine Forest  

NASA Astrophysics Data System (ADS)

The partitioning of latent heat flux into contributions from ground evaporation and plant transpiration in land surface models is a key feature of any hydrological scheme, but notoriously difficult to resolve. Global scale models show significant differences in the terrestrial energy balance, which can be traced to poor constraints on the pathways of water that control evapotranspiration (ET). In addition, the depth of water uptake has been shown to be correlated with ecosystem ET partitioning, but vegetation rooting profiles are difficult to observe and therefore present a significant source of uncertainty. Stable isotope ratios in water from soil, leaves and water vapor have been used to help constrain the ET partitioning and to track water movement in ecosystems, but many previous studies have been limited in two regards: 1) lack of sufficient data to provide true closure, and 2) lack of an adequate modeling framework to incorporate many of the processes which control ET. We present results for the partitioning of ET from an isotopically-enabled land surface model (ISOLSM) that is driven by meteorological, hydrological and isotopic data collected at the Manitou Experimental Forest during the summer and autumn of 2011. An ensemble of 394 realizations has been produced, constrained by observations of latent heat, sensible heat and CO2 fluxes. Even when all three flux constraints are met, the transpiration fraction is not well-constrained. These experiments show that previous work using isotopic observations likely has significant uncertainty in their ET partitioning estimates. However, root-weighted soil isotope values have proven to sufficiently provide a final constraint on transpiration fraction, and an investigation of the time scales associated with this constraint is conducted. A sensitivity analysis of rooting profile and ET partitioning reveals the soil isotope ratios, and therefore the estimate of transpiration fraction, depend strongly on the rooting profile.

Wong, T.; Berkelhammer, M. B.; Noone, D. C.

2013-12-01

273

On the spatial distribution of the transpiration and soil moisture of a Mediterranean heterogeneous ecosystem in water-limited conditions.  

NASA Astrophysics Data System (ADS)

Mediterranean ecosystems are characterized by a strong heterogeneity, and often by water-limited conditions. In these conditions contrasting plant functional types (PFT, e.g. grass and woody vegetation) compete for the water use. Both the vegetation cover spatial distribution and the soil properties impact the soil moisture (SM) spatial distribution. Indeed, vegetation cover density and type affects evapotranspiration (ET), which is the main lack of the soil water balance in these ecosystems. With the objective to carefully estimate SM and ET spatial distribution in a Mediterranean water-limited ecosystem and understanding SM and ET relationships, an extended field campaign is carried out. The study was performed in a heterogeneous ecosystem in Orroli, Sardinia (Italy). The experimental site is a typical Mediterranean ecosystem where the vegetation is distributed in patches of woody vegetation (wild olives mainly) and grass. Soil depth is low and spatially varies between 10 cm and 40 cm, without any correlation with the vegetation spatial distribution. ET, land-surface fluxes and CO2 fluxes are estimated by an eddy covariance technique based micrometeorological tower. But in heterogeneous ecosystems a key assumption of the eddy covariance theory, the homogeneity of the surface, is not preserved and the ET estimate may be not correct. Hence, we estimate ET of the woody vegetation using the thermal dissipation method (i.e. sap flow technique) for comparing the two methodologies. Due the high heterogeneity of the vegetation and soil properties of the field a total of 54 sap flux sensors were installed. 14 clumps of wild olives within the eddy covariance footprint were identified as the most representative source of flux and they were instrumented with the thermal dissipation probes. Measurements of diameter at the height of sensor installation (height of 0.4 m above ground) were recorded in all the clumps. Bark thickness and sapwood depth were measured on several trees to obtain a generalized estimates of sapwood depth. The known of allometric relationships between sapwood area, diameter and canopy cover area within the eddy covariance footprint helped for the application of a reliable scaling procedure of the local sap flow estimates which are in a good agreement with the estimates of ET eddy covariance based. Soil moisture were also extensively monitored through 25 probes installed in the eddy covariance footprint. Results show that comparing eddy covariance and sap flow ET estimates eddy covariance technique is still accurate in this heterogeneous field, whereas the key assumption, surface homogeneity, is not preserved. Furthermore, interestingly wild olives still transpire at higher rates for the driest soil moisture conditions, confirming the hydraulic redistribution from soil below the roots, and from roots penetrating deep cracks in the underlying basalt parent rock.

Curreli, Matteo; Corona, Roberto; Montaldo, Nicola; Albertson, John D.; Oren, Ram

2014-05-01

274

Effect of Host Plant Resistance and Reduced Rates and Frequencies of Fungicide Application to Control Potato Late Blight  

Microsoft Academic Search

Kirk, W. W., Felcher, K. J., Douches, D. S., Coombs, J., Stein, J. M., Baker, K. M., and Ham- merschmidt, R. 2001. Effect of host plant resistance and reduced rates and frequencies of fungi- cide application to control potato late blight. Plant Dis. 85:1113-1118. Field experiments were conducted during 1998 to 2000 to determine the response of commer- cial potato

W. W. Kirk; K. J. Felcher; D. S. Douches; J. Coombs; J. M. Stein; K. M. Baker; R. Hammerschmidt

2001-01-01

275

Increase in recombination rate in Arabidopsis thaliana plants sharing gaseous environment with X-ray and UVC-irradiated plants depends on production of radicals  

PubMed Central

X-ray and UVC are the two physical agents that damage DNA directly, with both agents capable of inducing double-strand breaks. Some of our recent work has demonstrated that local exposure to UVC results in a systemic increase in recombination frequency, suggesting that information about exposure can be passed from damaged to non-damaged tissue. Indeed, we recently showed that plants sharing the same enclosed environment with UVC-irradiated plants exhibit similar increase in homologous recombination frequency as irradiated plants. Here, we further tested whether yet another DNA-damaging agent, X-ray, is capable of increasing recombination rate (RR) in neighboring plants grown in a Petri dish. To test this, we grew plants exposed to X-ray or UVC irradiation in an enclosed environment next to non-exposed plants. We found that both X-ray and UVC-irradiated plants and neighboring plants exhibited comparable increases in the levels of strand breaks and the RR. We further showed that pre-exposure of plants to radical scavenger DMSO substantially alleviates the radiation-induced increase in RR and prevents formation of bystander signal. Our results suggest that the increase in RR in bystander plants can also be triggered by X-ray and that radicals may play some role in initiation or maintenance of this signal.

Zemp, Franz J.; Sidler, Corinne; Kovalchuk, Igor

2012-01-01

276

Transpiration-purged optical probe: a novel sensor for high temperature harsh environments  

NASA Astrophysics Data System (ADS)

Typical control systems that are found in modern power plants must control the many physical aspects of the complex processes that occur inside the various components of the power plant. As detection and monitoring of pollutants becomes increasingly important to plant operation, these control systems will become increasingly complex, and will depend upon accurate monitoring of the concentration levels of the various chemical species that are found in the gas streams. In many cases this monitoring can be done optically. Optical access can also be used to measure thermal emissions and the particulate loading levels in the fluid streams. Some typical environments were optical access is needed are combustion chambers, reactor vessels, the gas and solid flows in fluidized beds, hot gas filters and heat exchangers. These applications all have harsh environments that are at high temperatures and pressures. They are often laden with products of combustion and other fine particulate matter which is destructive to any optical window that could be used to monitor the processes in these environments in order to apply some control scheme over the process. The dust and char that normally collects on the optical surfaces reduces the optical quality and thus impairs the ability of the optical surface to transmit data. Once this has occurred, there is generally no way to clean the optical surface during operation. The probe must be dismounted from the vessel, disassembled and cleaned or replaced, then remounted. This would require the shutdown of the particular component of the plant where optical monitoring is required. This renders the probe ineffective to be used as the monitoring part of any control system application. The components of optical monitoring equipment are usually built in supporting structures that require precise alignment. This is almost always accomplished using fine scale adjustments to specialized mounting hardware that is attached to the reactor vessel. When the temperature of these supporting structures increases due to the high temperature process that is occurring inside the vessel, the optical alignment can often suffer due to the thermal expansion of the mounting structure. This can render them useless especially for gas velocity measurements or other situations where precise optical alignment is required. What is needed is an optical probe that can be inserted into any hazardous environment that will not suffer alignment problems or other failure modes that are related to high temperature dirty environments, and at the same time maintain a clean optical surface through the lifetime of the devise so that it may be continually used for optical inspection or for control system applications. This paper describes details of the construction and the use of a transpiration purged optical probe which mitigates the problems that are outlined above. The transpiration probe may be used as either an emitter or a detector. The probe is implemented in the harsh high temperature environment of the NETL pulsed combustion system where products of combustion and particulate matter have been shown to degrade the performance of a normal optical window. Assessments of combustion heat release are made by monitoring the ultraviolet signatures that are produced by the concentration of OH during a pulsed combustion process. It is shown that these measurements are directly correlated with the pressure within the pulsed combustor. Probe temperature measurements are also presented to show how the probe and its mounting hardware remain at constant temperatures well below the high temperature environment which they monitor.

VanOsdol, John; Woodruff, Steve; Straub, Douglas

2007-10-01

277

Large rate of uptake of atmospheric carbon dioxide by planted forest biomass in Korea  

NASA Astrophysics Data System (ADS)

The Republic of Korea, henceforth referred to as Korea, has successfully implemented intensive programs of reforestation and forest management over the last 30 years to restore its once-rich forests. This nationwide effort has resulted in a massive accumulation of less than 30-year-old tree biomass, which now accounts for about 72% of the total forest biomass in Korea. Here we use a forest tree inventory data set for Korea to calculate the effectiveness of these planted trees in absorbing excess carbon dioxide from the atmosphere during the period 1954-2000. The forest carbon density in Korea has increased from 5-7 megagrams of carbon per hectare (Mg C ha-1, Mg = 106 grams) in the period 1955-1973 to more than 30 Mg C ha-1 in the late 1990s. The calculated carbon uptake has increased from a mean rate of 0.001 petagrams of carbon per year (Pg C yr-1, Pg = 1015 grams) in the period 1955-1973 to as high as 0.012 Pg C yr-1 in recent years, largely due to the 30-year implementation of reforestation and forest management projects. The contemporary rate of carbon uptake by the total Korean tree biomass is approximately one-half of the 1994-1998 mean rate of carbon uptake by the total Chinese forest biomass of 0.026 Pg C yr-1 [, 2001]; the Chinese forest biomass has recently been found to be a significant carbon sink in northern temperate regions. The observed uptake rate for Korea is remarkably high, considering the fact that the total area of Korean forests is approximately 16 times smaller than that of Chinese forests. Our results show that long-term rates of carbon sequestration by nationwide forests can be increased substantially through reforestation and forest management.

Choi, Sung-Deuk; Lee, Kitack; Chang, Yoon-Seok

2002-12-01

278

Comparative measurements of xylem pressure in transpiring and non-transpiring leaves by means of the pressure chamber and the xylem pressure probe  

Microsoft Academic Search

proposed more than 100 years ago by Dixon and Joly (1894). According to this theory, long-distance water Simultaneous measurements were made with the transport in xylem is driven by tension (negative pressure) xylem pressure probe on exposed, transpiring leaves gradients generated by the evaporation of water from and with the Scholander pressure chamber on both leaves and transmitted through continuous

P. J. Melcher; F. C. Meinzer; D. E. Yount; G. Goldstein; U. Zimmermann

1998-01-01

279

Rates of evolution in seed plants: Net increase in diversity of chromosome numbers and species numbers through time  

PubMed Central

An approach was made to the problem of estimating rates of chromosomal evolution in plants. This was done by considering variability in chromosome number within genera whose ages are known approximately from fossil and biogeographic evidence. The relative increases in chromosome number diversity per lineage per unit time were as follows: herbaceous angiosperms, 100; woody angiosperms, 14; conifers, 2; and cycads, 0. Rates of increase in species diversity were estimated in an analogous way. These rates were strongly correlated with the karyotypic rates. These evolutionary rate differences between major groups of seed plants are largely explicable in terms of the breeding structures of populations. Herbs usually have small to moderate effective population sizes, and relatively high dispersability. By contrast, woody angiosperms and gymnosperms are usually obligate outbreeders with large effective population sizes and low dispersability. Thus the probability of fixing and dispersing new karyotypes or novel character ensembles is higher in herbs than in other seed plants.

Levin, D. A.; Wilson, A. C.

1976-01-01

280

Coupled hydraulic and photosynthetic feedbacks on forest transpiration throughout the growing season  

NASA Astrophysics Data System (ADS)

Ecosystem models account for vegetative controls on water fluxes using environmental drivers and hydraulic and/or biochemical limits on canopy stomatal conductance (Gs), variations in space and time of leaf area index (L), and species or biome specific parameters. However, some parameters, such as maximum stomatal conductance or its reference proxy at vapor pressure deficit of 1 kPa (Gsref), may not be strictly time-independent suggesting as yet undefined mechanisms in the models. We developed a model of coupled canopy water and carbon exchange, which allowed us to examine photosynthetic and hydraulic feedbacks on Gsref spanning the whole growing season for several dominant tree species in wetland and upland positions that collectively account for most a 1600 square km region centered on the WLEF AmeriFlux tower in Wisconsin, USA. The model assimilated half-hourly sap flux and micrometeorological data to quantify and explain temporal variations in Gsref for trembling aspen, sugar maple, and red pine in upland sites, and speckled alder and white cedar in wetland sites. Results show (1) phenological effects on photosynthetic activity with feedback on Gsref in all species, and (2) lags of up to two months between maximum per unit leaf area photosynthetic rates for conifer versus deciduous species. These results show that for given environmental conditions canopy transpiration depends on both L and timing of biochemical activation, both of which have implications for regional ecosystem water cycling.

Mackay, D. S.; Ewers, B. E.

2007-12-01

281

Characterization of Transpiration in a Deciduous Forest of the US Midwest  

NASA Astrophysics Data System (ADS)

The exchange of water between atmosphere and biosphere is an important determinant of climate and the productivity of vegetation, as transpiration involves substantial amounts of energy. Knowing how transpiration changes over seasonal and diurnal cycles can help increase the understanding of how a forest reacts to changes in the biosphere and atmosphere on both short and long time scales. A study was conducted to characterize the daily and seasonal variation of transpiration in sugar maple (Acer Saccharum) at the Morgan-Monroe State Forest (MMSF) AmeriFlux site in Indiana (USA), were this species represent more than 25% of the forest basal area. Transpiration was estimated by up-scaling single point measurements of sap flow density obtained using the heat-pulse technique. To characterize the variability of sap flow density in the deep sapwood of sugar maples, 3 to 4 radial profiles were obtained for each sampled tree at different positions around the trunk. Different approaches were then tested to scale up to whole tree sap flow. Seventeen trees of different diameter were sampled by three roving sap flow systems, taking measurements from each tree for 5-7 contiguous days. Because of the small scale but complex topography in the area and the relatively shallow soil, particular attention was given to the effect of spatial and temporal variability of soil moisture content on transpiration; for this reason, sampled trees were selected along a topographic gradient and soil water content was measured in the proximity of each tree. Meteorological measurements taken at the nearby MMSF AmeriFlux tower were used to explain transpiration variability in terms of vapor pressure deficit, and solar radiation, while eddy- covariance measurements of latent heat flux were related to the up-scaled transpiration of sugar maples in the study area.

Dragoni, D.; Caylor, K. K.; Schmid, H.

2006-12-01

282

Increased vapor pressure deficit due to higher temperature leads to greater transpiration and faster mortality during drought for tree seedlings common to the forest-grassland ecotone.  

PubMed

Tree species growing along the forest-grassland ecotone are near the moisture limit of their range. Small increases in temperature can increase vapor pressure deficit (VPD) which may increase tree water use and potentially hasten mortality during severe drought. We tested a 40% increase in VPD due to an increase in growing temperature from 30 to 33°C (constant dewpoint 21°C) on seedlings of 10 tree species common to the forest-grassland ecotone in the southern Great Plains, USA. Measurement at 33 vs 30°C during reciprocal leaf gas exchange measurements, that is, measurement of all seedlings at both growing temperatures, increased transpiration for seedlings grown at 30°C by 40% and 20% for seedlings grown at 33°C. Higher initial transpiration of seedlings in the 33°C growing temperature treatment resulted in more negative xylem water potentials and fewer days until transpiration decreased after watering was withheld. The seedlings grown at 33°C died 13% (average 2 d) sooner than seedlings grown at 30°C during terminal drought. If temperature and severity of droughts increase in the future, the forest-grassland ecotone could shift because low seedling survival rate may not sufficiently support forest regeneration and migration. PMID:23718199

Will, Rodney E; Wilson, Stuart M; Zou, Chris B; Hennessey, Thomas C

2013-10-01

283

An improved heat pulse method to measure low and reverse rates of sap flow in woody plants  

Microsoft Academic Search

Summary The compensation heat pulse method (CHPM) is of limited value for measuring low rates of sap flow in woody plants. Recent application of the CHPM to woody roots has further illustrated some of the constraints of this technique. Here we present an improved heat pulse method, termed the heat ratio method (HRM), to measure low and reverse rates of

STEPHEN S. O. BURGESS; MARK A. ADAMS; NEIL C. TURNER; CRAIG R. BEVERLY; CHIN K. ONG; AHMED A. H. KHAN; TIM M. BLEBY

284

Influence of stocking rate and grazing system on plant basal cover and botanical composition of veld in the northern cape  

Microsoft Academic Search

Changes in basal cover and botanical composition were recorded at four stocking rates, both under continuous and rotational grazing in the Northern Cape. The experiment was conducted with cattle. Results suggested that heavier stocking rates could be applied under rotational grazing than under continuous grazing without veld deterioration occuring. After four seasons, botanical composition deteriorated only under continuous grazing. Plant

J. H. Fourie; G. J. Redelinghuys; D. P. J. Opperman

1984-01-01

285

Short-term and long-term effects of low total pressure on gas exchange rates of spinach  

NASA Astrophysics Data System (ADS)

In this study, spinach plants were grown under atmospheric and low pressure conditions with constant O2 and CO2 partial pressures, and the effects of low total pressure on gas exchange rates were investigated. CO2 assimilation and transpiration rates of spinach grown under atmospheric pressure increased after short-term exposure to low total pressure due to the enhancement of leaf conductance. However, gas exchange rates of plants grown at 25 kPa total pressure were not greater than those grown at atmospheric pressure. Stomatal pore length and width were significantly smaller in leaves grown at low total pressure. This result suggested that gas exchange rates of plants grown under low total pressure were not stimulated even with the enhancement of gas diffusion because the stomatal size and stomatal aperture decreased.

Iwabuchi, K.; Kurata, K.

286

Spectral Quantification of Transpiration, Evaporation and Soil Root Zone Hydrology in Forested Ecosystems  

NASA Astrophysics Data System (ADS)

Evapotranspiration plays an essential role in the energy balance of the planet and climate, but no effective means exist to produce long-term data records of evapotranspiration, crucial to investigate future climate scenarios. As climate warms, global precipitation is also increasing. However, the IPCC AR4 reports a number of regions where precipitation is increasing but where (Arctic regions, Mediterranean, SE Asia, SW United States and the Sahel), the regions seem to be getting "drier". Model simulations (Bounoua et al., 2010) have hypothesized that an underlying mechanism may be an increase in vegetation leaf area where the additional precipitation has stimulated growth resulting in an even faster rate in evapotranspiration with decreasing runoff. In this paper we employ a recently developed tower-mounted spectrometer algorithm to quantify the diurnal and seasonal variation in the photosynthetic uptake of carbon (Ac), then use Ac (t) in the Ball-Berry-Collatz equation relating stomatal conductance gc(t) to Ac(t) to compute gc. With gc we then compute the diurnal and seasonal variation in bulk transpiration (Tr) rates through the canopy stomata as a function of measured metorological conditions at various forest sites. The sites also have tower mounted spectrometers and eddy-correlation (EC) instruments and meteorological instrumentation. The EC instruments measure the total evapotranspiration (ET), the spectrometer Tr only - the difference being the evaporation rate E. With these independently "measured" values Tr and E and precipitation we are able to quantify the dynamical behaviour of root-zone soil moisture following precipitation events. We then use the dynamical variation in ET, Tr ,E and Tl following precipitation events to investigate the various modes of water transport and storage among at the sites and compare them to modeled values using the Simple Biosphere Model (SiB2).

Hall, F. G.; Bounoua, L.

2012-12-01

287

Cyclic variations in nitrogen uptake rate in soybean plants: uptake during reproductive growth  

NASA Technical Reports Server (NTRS)

Net uptake of NO3- by non-nodulated soybean plants [Glycine max (L.) Merr. cv. Ransom] growing in flowing hydroponic culture was measured daily during a 63 d period of reproductive development between the first florally inductive photoperiod and [unknown word] seed growth. Removal of NO3- from a replenished solution containing 1.0 mol m-3 NO3- was determined by ion chromatography. Uptake of NO3- continued throughout reproductive development. The net uptake rate of NO3- cycled between maxima and minima with a periodicity of oscillation of 3 to 7 d during the floral stage and about 6 d during the fruiting stage. Coupled with increasing concentrations of carbon and C : N ratios in tissues, the oscillations in net uptake rates of NO3- are evidence that the demand for carbohydrate by reproductive organs is contingent on the availability of nitrogen in the shoot pool rather than that the demand for nitrogen follows the flux of carbohydrate into reproductive tissues.

Vessey, J. K.; Raper, C. D. Jr; Henry, L. T.; Raper CD, J. r. (Principal Investigator)

1990-01-01

288

Numerical simulation of gas-phonon coupling in thermal transpiration flows  

NASA Astrophysics Data System (ADS)

Thermal transpiration is a rarefied gas flow driven by a wall temperature gradient and is a promising mechanism for gas pumping without moving parts, known as the Knudsen pump. Obtaining temperature measurements along capillary walls in a Knudsen pump is difficult due to extremely small length scales. Meanwhile, simplified analytical models are not applicable under the practical operating conditions of a thermal transpiration device, where the gas flow is in the transitional rarefied regime. Here, we present a coupled gas-phonon heat transfer and flow model to study a closed thermal transpiration system. Discretized Boltzmann equations are solved for molecular transport in the gas phase and phonon transport in the solid. The wall temperature distribution is the direct result of the interfacial coupling based on mass conservation and energy balance at gas-solid interfaces and is not specified a priori unlike in the previous modeling efforts. Capillary length scales of the order of phonon mean free path result in a smaller temperature gradient along the transpiration channel as compared to that predicted by the continuum solid-phase heat transfer. The effects of governing parameters such as thermal gradients, capillary geometry, gas and phonon Knudsen numbers and, gas-surface interaction parameters on the efficiency of thermal transpiration are investigated in light of the coupled model.

Guo, Xiaohui; Singh, Dhruv; Murthy, Jayathi; Alexeenko, Alina A.

2009-10-01

289

Part-failure rate data book outline for gas turbine and combined-cycle plants. Final report  

Microsoft Academic Search

The development of a Lambda (failure rate) book for Westinghouse combined cycle plants is described. The Lambda book, containing a separate sheet for each system, subsystem, or component, provides reliability statistics based on operating experience. The field-reported data from six utilities represent 54,185 fired hours of W501 combustion turbine operation. The reliability parameters determined include: failure rate, maintenance rate, life,

H. H. Wisch; R. J. Thoman

1985-01-01

290

A High-Rate Secondary Treatment Based on a Moving Bed Bioreactor and Multimedia Filters for Small Wastewater Treatment Plants  

Microsoft Academic Search

For small wastewater treatment plants (WWPTs), high-rate secondary treatment systems with good treatment efficiency and easy, stable, and robust operation are called for. In this paper an experimental study on a high rate secondary treatment based on moving bed biofilm reactor (MBBR) and multimedia filters is presented. A high rate MBBR converts easily biodegradable SCOD in short HRT (0.5 h) directly

Z. Liao; V. Rasmussen; H. Ødegaard

2003-01-01

291

Model-derived dose rates per unit concentration of radon in air in a generic plant geometry.  

PubMed

A model for the derivation of dose rates per unit radon concentration in plants was developed in line with the activities of a Task Group of the International Commission on Radiological Protection (ICRP), aimed at developing more realistic dosimetry for non-human biota. The model considers interception of the unattached and attached fractions of the airborne radon daughters by plant stomata, diffusion of radon gas through stomata, permeation through the plant's epidermis and translocation of deposited activity to plant interior. The endpoint of the model is the derivation of dose conversion coefficients relative to radon gas concentration at ground level. The model predicts that the main contributor to dose is deposition of (214)Po ?-activity on the plant surface and that diffusion of radon daughters through the stomata is of relatively minor importance; hence, daily variations have a small effect on total dose. PMID:21739195

Vives i Batlle, J; Smith, A; Vives-Lynch, S; Copplestone, D; Pröhl, G; Strand, T

2011-11-01

292

Overexpression of a Plasma Membrane Aquaporin in Transgenic Tobacco Improves Plant Vigor under Favorable Growth Conditions but Not under Drought or Salt Stress  

PubMed Central

Most of the symplastic water transport in plants occurs via aquaporins, but the extent to which aquaporins contribute to plant water status under favorable growth conditions and abiotic stress is not clear. To address this issue, we constitutively overexpressed the Arabidopsis plasma membrane aquaporin, PIP1b, in transgenic tobacco plants. Under favorable growth conditions, PIP1b overexpression significantly increased plant growth rate, transpiration rate, stomatal density, and photosynthetic efficiency. By contrast, PIP1b overexpression had no beneficial effect under salt stress, whereas during drought stress it had a negative effect, causing faster wilting. Our results suggest that symplastic water transport via plasma membrane aquaporins represents a limiting factor for plant growth and vigor under favorable conditions and that even fully irrigated plants face limited water transportation. By contrast, enhanced symplastic water transport via plasma membrane aquaporins may not have any beneficial effect under salt stress, and it has a deleterious effect during drought stress.

Aharon, Refael; Shahak, Yosepha; Wininger, Smadar; Bendov, Rozalina; Kapulnik, Yoram; Galili, Gad

2003-01-01

293

An in vivo root hair assay for determining rates of apoptotic-like programmed cell death in plants  

PubMed Central

In Arabidopsis thaliana we demonstrate that dying root hairs provide an easy and rapid in vivo model for the morphological identification of apoptotic-like programmed cell death (AL-PCD) in plants. The model described here is transferable between species, can be used to investigate rates of AL-PCD in response to various treatments and to identify modulation of AL-PCD rates in mutant/transgenic plant lines facilitating rapid screening of mutant populations in order to identify genes involved in AL-PCD regulation.

2011-01-01

294

Effect of Environmental Factors on Cuticular Transpiration Resistance 1  

PubMed Central

Measurements of the various diffusive resistances to water vapor transport within the leaves of sunflower plants (Helianthus annuus) growing in a controlled environment chamber, were used to calculate values of cuticular resistance under a range of environmental conditions. Cuticular resistance to water loss was found to be inversely related to the relative humidity of the surrounding air, and it is suggested that such a mechanism would form a useful adaptation to arid conditions, enabling plants to maintain a more favorable internal water balance.

Moreshet, S.

1970-01-01

295

Mycorrhizal and non-mycorrhizal Lactuca sativa plants exhibit contrasting responses to exogenous ABA during drought stress and recovery  

PubMed Central

The arbuscular mycorrhizal (AM) symbiosis enhances plant tolerance to water deficit through the alteration of plant physiology and the expression of plant genes. These changes have been postulated to be caused (among others) by different contents of abscisic acid (ABA) between AM and non-AM plants. However, there are no studies dealing with the effects of exogenous ABA on the expression of stress-related genes and on the physiology of AM plants. The aim of the present study was to evaluate the influence of AM symbiosis and exogenous ABA application on plant development, physiology, and expression of several stress-related genes after both drought and a recovery period. Results show that the application of exogenous ABA had contrasting effects on AM and non-AM plants. Only AM plants fed with exogenous ABA maintained shoot biomass production unaltered by drought stress. The addition of exogenous ABA enhanced considerably the ABA content in shoots of non-AM plants, concomitantly with the expression of the stress marker genes Lsp5cs and Lslea and the gene Lsnced. By contrast, the addition of exogenous ABA decreased the content of ABA in shoots of AM plants and did not produce any further enhancement of the expression of these three genes. AM plants always exhibited higher values of root hydraulic conductivity and reduced transpiration rate under drought stress. From plants subjected to drought, only the AM plants recovered their root hydraulic conductivity completely after the 3 d recovery period. As a whole, the results indicate that AM plants regulate their ABA levels better and faster than non-AM plants, allowing a more adequate balance between leaf transpiration and root water movement during drought and recovery.

Aroca, Ricardo; Vernieri, Paolo; Ruiz-Lozano, Juan Manuel

2008-01-01

296

Mycorrhizal and non-mycorrhizal Lactuca sativa plants exhibit contrasting responses to exogenous ABA during drought stress and recovery.  

PubMed

The arbuscular mycorrhizal (AM) symbiosis enhances plant tolerance to water deficit through the alteration of plant physiology and the expression of plant genes. These changes have been postulated to be caused (among others) by different contents of abscisic acid (ABA) between AM and non-AM plants. However, there are no studies dealing with the effects of exogenous ABA on the expression of stress-related genes and on the physiology of AM plants. The aim of the present study was to evaluate the influence of AM symbiosis and exogenous ABA application on plant development, physiology, and expression of several stress-related genes after both drought and a recovery period. Results show that the application of exogenous ABA had contrasting effects on AM and non-AM plants. Only AM plants fed with exogenous ABA maintained shoot biomass production unaltered by drought stress. The addition of exogenous ABA enhanced considerably the ABA content in shoots of non-AM plants, concomitantly with the expression of the stress marker genes Lsp5cs and Lslea and the gene Lsnced. By contrast, the addition of exogenous ABA decreased the content of ABA in shoots of AM plants and did not produce any further enhancement of the expression of these three genes. AM plants always exhibited higher values of root hydraulic conductivity and reduced transpiration rate under drought stress. From plants subjected to drought, only the AM plants recovered their root hydraulic conductivity completely after the 3 d recovery period. As a whole, the results indicate that AM plants regulate their ABA levels better and faster than non-AM plants, allowing a more adequate balance between leaf transpiration and root water movement during drought and recovery. PMID:18469324

Aroca, Ricardo; Vernieri, Paolo; Ruiz-Lozano, Juan Manuel

2008-01-01

297

The role of planted forests in urban water budgets (Invited)  

NASA Astrophysics Data System (ADS)

In arid regions which are not naturally forested, urban trees are sustained through the redistribution of water resources as irrigation. Assessments of outdoor water use in Southwestern US cities have shown that not only is 30-75% of residential water use expended on outdoor landscapes, but that irrigation is frequently in excess of estimated plant demand. Thus, there is a need to understand the factors which influence the magnitude and variability of water use of urban trees. A complicating factor in assessing urban tree water use is the widely recognized heterogeneity of urban environments. Human choices and decision-making result in a landscape with significant variability in water and nutrient inputs, microclimate, biotic inputs and vegetation composition. In order to quantify urban tree water use and explain variation in water use resulting from variability in resource availability and species composition, we have conducted a combination of sapflux, growth and isotopic studies on more than 35 common (primarily non-native) tree species in the Los Angeles basin. The objective of these studies was to determine how much variability in water use and water use efficiency exists within and between commonly planted urban tree species, and what factors explain or can be used to predict this variability. Through these studies we have found considerable differences (up to two fold) in tree transpiration within a given species, attributable to differences in water and nutrient availability and tree planting density. Additionally, we have found substantial variation in the water use of different species: at typical urban planting densities, peak transpiration rates can be more than ten times greater for high transpiring trees than low transpiring trees. Finally, we found whole tree water use efficiency to vary across species by a factor of up to a hundred, explained to a large degree by the climate conditions (especially vapor pressure deficit) in the native ranges of these non-native trees. On the scale of the entire city of Los Angeles, we estimate that the urban forest could use as much as 50% of the total municipal water use. Overall, we have found that urban trees can use substantial quantities of water, and that species choice matters greatly in determining urban landscape water use.

McCarthy, H. R.; Pataki, D. E.; Litvak, E.

2009-12-01

298

Plants  

NSDL National Science Digital Library

Get ready to explore plants! Let's Learn About Plants! Question: What do plants need to live? Watch the video to find out! What does it need to grow? Question: What are the parts of a plant? Click to find out! Parts of a Plant Question: What is the life cycle of a plant? Watch the video to find out! Plant Life Cycle Video Question: ...

Berneski, Miss

2011-12-10

299

An examination of heat rate improvements due to waste heat integration in an oxycombustion pulverized coal power plant  

NASA Astrophysics Data System (ADS)

Oxyfuel, or oxycombustion, technology has been proposed as one carbon capture technology for coal-fired power plants. An oxycombustion plant would fire coal in an oxidizer consisting primarily of CO2, oxygen, and water vapor. Flue gas with high CO2 concentrations is produced and can be compressed for sequestration. Since this compression generates large amounts of heat, it was theorized that this heat could be utilized elsewhere in the plant. Process models of the oxycombustion boiler, steam cycle, and compressors were created in ASPEN Plus and Excel to test this hypothesis. Using these models, heat from compression stages was integrated to the flue gas recirculation heater, feedwater heaters, and to a fluidized bed coal dryer. All possible combinations of these heat sinks were examined, with improvements in coal flow rate, Qcoal, net power, and unit heat rate being noted. These improvements would help offset the large efficiency impacts inherent to oxycombustion technology.

Charles, Joshua M.

300

Monitoring Evaporation/Transpiration in a Vineyard from Two-Source Energy Balance and Radiometric Temperatures  

NASA Astrophysics Data System (ADS)

Water management and understanding of irrigation efficiency could be significantly improved if the components of evapotranspiration (ET) in row-crop systems (plants and soil interrows) could be quantified separately. This evaporation/transpiration (E/T) partition, and its daily and seasonal evolution, depends on a variety of biophysical and environmental factors. In this work we present an operational method to provide continuous E/T results avoiding soil or canopy disturbance. This technique is based on the combination of the surface-atmosphere energy exchange modeling together with an accurate remote thermal characterization of the crop elements. An experiment was carried out in a row-crop vineyard in Mallorca, Spain, from June 2012 to May 2013. A set of 6 thermal-infrared radiometers (IRTs) were mounted in a mast placed in the middle of a vineyard N-S row. Two IRTs pointed to the soil between rows and other two pointed to the plants from a frontal view, measuring both east and west sides of the row. A fifth IRT pointed upward to collect the downwelling sky radiance and the remaining IRT was mounted at 4.5-m height over the canopy measuring the composed soil-canopy temperature. Measurements of the four components of the net radiation over the canopy and soil heat fluxes, as well as air temperature, humidity, wind speed, and soil moisture, were collected and stored in 15-min averages. A two-source energy balance approach was applied to the vineyard from its appropriate thermal characterization. Total and separate soil/canopy components of net radiation, soil, sensible and latent heat fluxes were obtained every 15 minutes and averaged at hourly and daily scales. Comparison between observed and modeled values of available surface energy showed relative errors below 15%. An analysis of the partition E/T was conducted along the vineyard growing season and the different phenological stages. In this experiment, interrow soil evaporation reached as much as 1/3 of the total cumulative evapotranspiration from floration to harvest. This technique can be useful for scientists and land managers interested in improving water use efficiency, not only because it is shown as an alternative to traditional weighing lysimeters, but also because the presented method allows the continuous monitoring of the E/T partition under a variety of meteorological conditions and covering the different stages of the crop development.

Sánchez, Juan Manuel; Doña, Carolina; Cuxart, Joan; Caselles, Vicente; Niclòs, Raquel

2014-05-01

301

Interspecific differences in dead plant buffering capacity alter the impact of acid rain on decomposition rates in tidal marshes  

Microsoft Academic Search

Simulated acid rain did not alter respiration rates of microbial associations on dead Spartina alterniora from Delaware salt marshes or on dead Carex lyngbyei from Oregon brackish marshes. Since these dead plant-microbe associations have a strong buffering capacity for acid rain, the microbial associations did not experience a low pH. In contrast, Phragmites australis has a low buffering capacity and

John L. Gallagher; Lisa A. Donovan; Donna M. Grant; Debra M. Decker

1987-01-01

302

Effect of plant density and nitrogen rates upon the leaf area of seed sugar beet on seed yield and quality  

Microsoft Academic Search

Three-year field trials were set up on eutric brown soil in northwestern Croatia (Zagreb) with the objective to determine the effect of plant density and nitrogen rates on the formation and size of leaf area of seed sugar beet, and on the yield and seed quality in seed production without transplanting. Investigations should also reveal how much the yield and

M. Pospišil; A. Pospišil; M. Rastija

2000-01-01

303

Quantification of excess water loss in plant canopies warmed with infrared heating.  

PubMed

Here we investigate the extent to which infrared heating used to warm plant canopies in climate manipulation experiments increases transpiration. Concerns regarding the impact of the infrared heater technique on the water balance have been raised before, but a quantification is lacking. We calculate transpiration rates under infrared heaters and compare these with air warming at constant relative humidity. As infrared heating primarily warms the leaves and not the air, this method increases both the gradient and the conductance for water vapour. Stomatal conductance is determined both independently of vapour pressure differences and as a function thereof, while boundary layer conductance is calculated using several approaches. We argue that none of these approaches is fully accurate, and opt to present results as an interval in which the actual water loss is likely to be found. For typical conditions in a temperate climate, our results suggest a 12-15% increase in transpiration under infrared heaters for a 1 °C warming. This effect decreases when stomatal conductance is allowed to vary with the vapour pressure difference. Importantly, the artefact is less of a concern when simulating heat waves. The higher atmospheric water demand underneath the heaters reflects naturally occurring increases of potential evapotranspiration during heat waves resulting from atmospheric feedback. While air warming encompasses no increases in transpiration, this fully depends on the ability to keep humidity constant, which in the case of greenhouses requires the presence of an air humidification system. As various artefacts have been associated with chamber experiments, we argue that manipulating climate in the field should be prioritized, while striving to limit confounding factors. The excess water loss underneath infrared heaters reported upon here could be compensated by increasing irrigation or applying newly developed techniques for increasing air humidity in the field. PMID:24501063

De Boeck, Hans J; Kimball, Bruce A; Miglietta, Franco; Nijs, Ivan

2012-09-01

304

The Competition between Liquid and Vapor Transport in Transpiring Leaves1[W][OPEN  

PubMed Central

In leaves, the transpirational flux of water exits the veins as liquid and travels toward the stomata in both the vapor and liquid phases before exiting the leaf as vapor. Yet, whether most of the evaporation occurs from the vascular bundles (perivascular), from the photosynthetic mesophyll cells, or within the vicinity of the stomatal pore (peristomatal) remains in dispute. Here, a one-dimensional model of the competition between liquid and vapor transport is developed from the perspective of nonisothermal coupled heat and water molecule transport in a composite medium of airspace and cells. An analytical solution to the model is found in terms of the energy and transpirational fluxes from the leaf surfaces and the absorbed solar energy load, leading to mathematical expressions for the proportions of evaporation accounted for by the vascular, mesophyll, and epidermal regions. The distribution of evaporation in a given leaf is predicted to be variable, changing with the local environment, and to range from dominantly perivascular to dominantly peristomatal depending on internal leaf architecture, with mesophyll evaporation a subordinate component. Using mature red oak (Quercus rubra) trees, we show that the model can be solved for a specific instance of a transpiring leaf by combining gas-exchange data, anatomical measurements, and hydraulic experiments. We also investigate the effect of radiation load on the control of transpiration, the potential for condensation on the inside of an epidermis, and the impact of vapor transport on the hydraulic efficiency of leaf tissue outside the xylem.

Rockwell, Fulton Ewing; Holbrook, N. Michele; Stroock, Abraham Duncan

2014-01-01

305

Cell water potential, osmotic potential, and turgor in the epidermis and mesophyll of transpiring leaves  

Microsoft Academic Search

Water potential, osmotic potential and turgor measurements obtained by using a cell pressure probe together with a nanoliter osmometer were compared with measurements obtained with an isopiestic psychrometer. Both types of measurements were conducted in the mature region of Tradescantia virginiana L. leaves under non-transpiring conditions in the dark, and gave similar values of all potentials. This finding indicates that

Hiroshi Nonami; E.-D. Schulze

1989-01-01

306

Mixed convection heat transfer in horizontal rectangular ducts with wall transpiration effects  

Microsoft Academic Search

A detailed numerical study was carried out to examine the effects of wall transpiration on laminar mixed convection flow and heat transfer in the entrance region of horizontal rectangular ducts. The vorticity-velocity method was employed in the formulation. Both thermal boundary conditions of uniform heat flux (UHF) and uniform wall temperature (UWT) were considered. Predicted results are presented for air

Wei-Mon Yan

1998-01-01

307

Diurnal courses of leaf conductance and transpiration of mistletoes and their hosts in Central Australia  

Microsoft Academic Search

In Australia, diurnal courses of leaf conductance and transpiration of hemiparasitic mistletoes (Loranthaceae) and their hosts were measured using steady-state porometers under conditions of partial drought and high evaporative demand. The sites spanned a diversity of climatic regions ranging from the subtropical arid zone with winter rainfall, through the subtropical arid zone with summer rainfall to the tropical summer rainfall

I. Ullmann; O. L. Lange; H. Ziegler; J. Ehleringer; E.-D. Schulze; I. R. Cowan

1985-01-01

308

Evaluation of compensated heat-pulse velocity method to determine vine transpiration using combined measurements of eddy covariance system and microlysimeters  

Microsoft Academic Search

â–º The CHPV method was tested in field conditions using an independent measurement of residual transpiration. â–º Measurements of eddy covariance system and microlysimeters were used to calculated residual transpiration. â–º Changes in FM, FL and k have a little effect in daily vine transpiration values. â–º Results demonstrate the applicability of CHPV method for obtain daily vine transpiration using

S. Ortega-Farias; S. Fuentes

2012-01-01

309

Contrasting roles of interception and transpiration in the hydrological cycle - Part 2: Moisture recycling  

NASA Astrophysics Data System (ADS)

The contribution of land evaporation to local and remote precipitation (i.e., moisture recycling) is of significant importance to sustain water resources and ecosystems. But how important are different evaporation components in sustaining precipitation? This is the first paper to present moisture recycling metrics for partitioned evaporation. In the companion paper, Part 1, evaporation was partitioned into vegetation interception, floor interception, soil moisture evaporation and open water evaporation (constituting the direct, purely physical fluxes, largely dominated by interception), and transpiration (delayed, biophysical flux). Here, we track these components forward as well as backward in time. We also include age tracers to study the atmospheric residence times of these evaporation components. As the main result we present a new image of the global hydrological cycle that includes quantification of partitioned evaporation and moisture recycling as well as the atmospheric residence times of all fluxes. We demonstrate that evaporated interception is more likely to return as precipitation on land than transpired water. On average, direct evaporation (essentially interception) is found to have an atmospheric residence time of eight days, while transpiration typically resides nine days in the atmosphere. Interception recycling has a much shorter local length scale than transpiration recycling, thus interception generally precipitates closer to its evaporative source than transpiration, which is particularly pronounced outside the tropics. We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells. On the other hand, transpiration remains active during dry spells and is transported over much larger distances downwind where it can act as a significant source of moisture. Thus, as various land-use types can differ considerably in their partitioning between interception and transpiration, our results stress that land-use changes (e.g., forest to cropland conversion) do not only affect the magnitude of moisture recycling, but could also influence the moisture recycling patterns and lead to a redistribution of water resources. As such, this research highlights that land-use changes can have complex effects on the atmospheric branch of the hydrological cycle.

van der Ent, R. J.; Wang-Erlandsson, L.; Keys, P. W.; Savenije, H. H. G.

2014-03-01

310

Transcription Factor Families Have Much Higher Expansion Rates in Plants than in Animals  

Microsoft Academic Search

Transcription factors (TFs), which are central to the regulation of gene expression, are usually members of multigene families. In plants, they are involved in diverse processes such as developmental control and elicitation of defense and stress responses. To investigate if differences exist in the expansion patterns of TF gene families between plants and other eukaryotes, we first used Arabidopsis (Arabidopsis

Shin-Han Shiu; Ming-Che Shih; Wen-Hsiung Li

2005-01-01

311

Decomposition and nutrient liberation rates of plant material in the Parana medio River (Argentina)  

Microsoft Academic Search

The degradation of plant material was studied in order to obtain degradation coefficients and nutrient release kinetics of the vegetation that will be submerged during the filling of the future Parana Medio man-made lake. A group of 13 plant species representative of the whole vegetation of the area were chosen.

M. Leguizamon; J. Hammerly; M. A. Maine; N. Sufie; M. J. Pizarro

1992-01-01

312

Gas transport by thermal transpiration in micro-channels -- A numerical study  

SciTech Connect

A reliable micro gas pump is an essential element to the development of many micro-systems for chemical gas analyses. At Sandia, the authors are exploring a different pumping mechanism, gas transport by thermal transpiration. Thermal transpiration refers to the rarefied gas dynamics developed in a micro-channel with a longitudinal temperature gradient. To investigate the potential of thermal transpiration for gas pumping in micro-systems, the authors have performed simulations and model analysis to design micro-devices and to assess their design performance before the fabrication process. The effort is to apply ICARUS (a Direct Simulation Monte Carlo code developed at Sandia) to characterize the fluid transport and evaluate the design performance. The design being considered has two plenums at different temperatures (hot and cold) separated by a micro-channel of 0.1 micron wide and 1 micron long. The temperature difference between the two plenums is 30 kelvin. ICARUS results, a quasi-steady analysis, predicts a net flow through the micro-channel with a velocity magnitude of about 0.4 m/s due to temperature gradient at the wall (thermal creep flow) at the early time. Later as the pressure builds up in the hot plenum, flow is reversed. Eventually when the system reaches steady state equilibrium, the net flow becomes zero. The thermal creep effect is compensated by the thermo-molecular pressure effect. This result demonstrates that it is important to include the thermo-molecular pressure effect when designing a pumping mechanism based on thermal transpiration. The DSMC technique can model this complex thermal transpiration problem.

Wong, C.C.; Hudson, M.L.; Potter, D.L.; Bartel, T.J.

1998-08-01

313

Time-temperature-dose rate superposition: A methodology for predicting cable degradation under ambient nuclear power plant aging conditions  

SciTech Connect

Time-temperature superposition is an empirical approach that has been used in polymers for more than 30 years to make thermal aging predictions at experimentally inaccessible times. Given the historical success of time-temperature superposition, we have expanded this approach for combined radiation-thermal environments, yielding an empirical time-temperature-dose rate shifting procedure. The procedure derives an isothermal curve for a given amount of material damage versus dose rate at a selected reference temperature by finding the Arrhenius activation energy that causes higher-temperature dose-rate data to superpose when shifted to the reference temperature. The resulting superposed curve at the reference temperature expends to much lower dose rates that, in effect, are experimentally inaccessible due to the long time periods which would be required. This procedure therefore allows meaningful predictions to be made under long-term, low-dose rate, radiation aging conditions. Using historical data from our radiation-aging program on nuclear power plant cable materials, we have successfully applied the time-temperature-dose rate superposition approach to four different materials. For two of these materials, extrapolated predictions based on the superposed data were found to be in excellent agreement with 12-year, low-dose rate nuclear power plant results.

Gillen, K.T.; Clough, R.L.

1988-08-01

314

Expansion and photosynthetic rate of leaves of soybean plants during onset of and recovery from nitrogen stress  

NASA Technical Reports Server (NTRS)

This study reports on the effects of nitrogen stress and restoration of nitrogen availability after a period of stress on expansion and photosynthetic rate of soybean leaves of differing maturity. We hypothesized that nitrogen resupply would lead to additional accumulation of reduced nitrogen in the leaves and, ultimately, resumption of leaf initiation and expansion and photosynthetic activity. In continuously nitrogen-stressed plants, expansion of middle trifoliolates of main-stem trifoliates and leaf area at full expansion were severely restricted. Leaves showing the greatest effects were initiated after removal of nitrogen. When the reduced nitrogen concentration in mature leaves of continuously stressed plants fell below 9 mg dm-2, the photosynthetic rate per unit leaf decreased rapidly, reaching a minimum of ca. 6-8 mg dm-2 h-1. The older mature leaves tended to abscise at this point, while the youngest leaves remained on the plant and continued to photosynthesize slowly. When nitrogen was resupplied, leaf expansion and final leaf area increased. Leaf initiation was also stimulated as reduced nitrogen levels rose in the leaves. Photosynthetic rates of the oldest and youngest pair of mature leaves returned to values comparable to those of similar-aged leaves of nonstressed soybean plants.

Tolley-Henry, L.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1986-01-01

315

Groundwater Availability Alters Soil-plant Nutrient Cycling in a Stand of Invasive, N-fixing Phreatophytes  

NASA Astrophysics Data System (ADS)

N-fixing phreatophytic trees are common in arid and semi-arid regions worldwide, and can play significant roles in modifying hydrology and soil-plant nutrient cycling where they are present. In light of reductions in groundwater levels in many arid regions we estimated annual transpiration rates at a stand level, and alterations to C, N and P accretion in soils as a function of groundwater depth in a ca.120 year old stand of Prosopis pallida along an elevation gradient in coastal leeward Hawaii. We measured sapflow and stand level sapwood area to quantify transpiration, and calculated groundwater transpiration rates using P. pallida stem water ?18O values. By measuring soil resistivity, we were able to compare the volume of groundwater transpired by these trees to groundwater depth across the stand. We examined nutrient deposition and accretion in soils in lowland areas of the stand with accessible shallow groundwater, compared to upland areas with no groundwater access, as indicated by stem water ?18O values. Resistivity results suggested that groundwater was at a height close to sea level throughout the stand. Transpiration was around 1900 m3 ha-1 year-1 in the areas of the stand closest to the sea (where groundwater was at around 1-4 m below ground level) and decreased to around a tenth of that volume where groundwater was not accessible. Litterfall rates over the course of the year studied were 17 times greater at lowland sites, but this litterfall contributed ca. 24 times the N, and 35 times the P of upland sites. Thus, groundwater access contributed to the total mass of nitrogen and phosphorus deposited in the form of litter through higher litter quantity and quality. Total N content of soils was 4.7 times greater and inorganic N pools were eight times higher at lowland plots. These results suggest that groundwater depth can have strong effects on soil-plant nutrient cycling, so that reductions in the availability of shallow groundwater are likely to impact soil nutrient availability in arid regions.

Dudley, B. D.; Miyazawa, Y.; Hughes, F.; Ostertag, R.; Kettwich, S. K.; MacKenzie, R.; Dulaiova, H.; Waters, C. A.; Bishop, J.; Giambelluca, T. W.

2013-12-01

316

Thermographic visualization of leaf response in cucumber plants infected with the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum.  

PubMed

Infection with the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum (FOC), which causes Fusarium wilt of cucumber plants, might result in changes in plant transpiration and water status within leaves. To monitor leaf response in cucumber infected with FOC, digital infrared thermography (DIT) was employed to detect changes in leaf temperature. During the early stages of FOC infection, stomata closure was induced by ABA in leaves, resulting in a decreased transpiration rate and increased leaf temperature. Subsequently, cell death occurred, accompanied by water loss, resulting in a little decrease in leaf temperature. A negative correlation between transpiration rate and leaf temperature was existed. But leaf temperature exhibited a special pattern with different disease severity on light-dark cycle. Lightly wilted leaves had a higher temperature in light and a lower temperature in dark than did in healthy leaves. We identified that the water loss from wilted leaves was regulated not by stomata but rather by cells damage caused by pathogen infection. Finally, water balance in infected plants became disordered and dead tissue was dehydrated, so leaf temperature increased again. These data suggest that membrane injury caused by FOC infection induces uncontrolled water loss from damaged cells and an imbalance in leaf water status, and ultimately accelerate plant wilting. Combining detection of the temperature response of leaves to light-dark conditions, DIT not only permits noninvasive detection and indirect visualization of the development of the soil-borne disease Fusarium wilt, but also demonstrates certain internal metabolic processes correlative with water status. PMID:23103050

Wang, Min; Ling, Ning; Dong, Xian; Zhu, Yiyong; Shen, Qirong; Guo, Shiwei

2012-12-01

317

Potential Usefulness of Antitranspirants for Increasing Water Use Efficiency in Plants.  

National Technical Information Service (NTIS)

Antitranspirants conserve water and maintain favorable plant water balances by reducing stomatal apertures, by forming a thin film over the leaves, or by reflecting excessive radiation. Under normal conditions, reductions in both transpiration and photosy...

R. M. Hagan D. C. Davenport

1970-01-01

318

Growth rates of rhizosphere microorganisms depend on competitive abilities of plants for nitrogen  

Microsoft Academic Search

Rhizosphere - one of the most important `hot spots' in soil - is characterized not only by accelerated turnover of microbial biomass and nutrients but also by strong intra- and inter-specific competition. Intra-specific competition occurs between individual plants of the same species, while inter-specific competition can occur both at population level (plant species-specific, microbial species-specific interactions) and at community level

Evgenia Blagodatskaya; Johanna Littschwager; Marianna Lauerer; Yakov Kuzyakov

2010-01-01

319

Reduction of lesion growth rate of late blight plant disease in transgenic potato expressing harpin protein  

Microsoft Academic Search

Using harpin protein gene from apple fire blight pathogenErwinia amylovora and potato prp1-1 promoter as main DNA elements, the feasibility of using pathogen infection-induced hypersensitive response\\u000a was explored as a new strategy of engineering fungal disease resistance. Three plant transformation vectors were constructed\\u000a and 68 transgenic potato plants were produced throughAgrobacterium mediated transformation method. Southern, Northern and Western blot analysis

Rugang Li; Yunliu Fan

1999-01-01

320

Seasonal photosynthetic gas exchange and water-use efficiency in a constitutive CAM plant, the giant saguaro cactus (Carnegiea gigantea).  

PubMed

Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic gas exchange and WUE, limiting our ability to predict growth and survival responses of desert CAM plants to climate change. We monitored net CO(2) assimilation (A(net)), stomatal conductance (g(s)), and transpiration (E) rates periodically over 2 years in a natural population of the giant columnar cactus Carnegiea gigantea (saguaro) near Tucson, Arizona USA to investigate environmental and physiological controls over carbon gain and water loss in this ecologically important plant. We hypothesized that seasonal changes in daily integrated water use efficiency (WUE(day)) in this constitutive CAM species would be driven largely by stomatal regulation of nighttime transpiration and CO(2) uptake responding to shifts in nighttime air temperature and humidity. The lowest WUE(day) occurred during time periods with extreme high and low air vapor pressure deficit (D(a)). The diurnal with the highest D(a) had low WUE(day) due to minimal net carbon gain across the 24 h period. Low WUE(day) was also observed under conditions of low D(a); however, it was due to significant transpiration losses. Gas exchange measurements on potted saguaro plants exposed to experimental changes in D(a) confirmed the relationship between D(a) and g(s). Our results suggest that climatic changes involving shifts in air temperature and humidity will have large impacts on the water and carbon economy of the giant saguaro and potentially other succulent CAM plants of warm desert environments. PMID:21822726

Bronson, Dustin R; English, Nathan B; Dettman, David L; Williams, David G

2011-11-01

321

Effect of low dose gamma irradiation on plant and grain nutrition of wheat  

NASA Astrophysics Data System (ADS)

We recently reported the use of low dose gamma irradiation to improve plant vigor, grain development and yield attributes of wheat ( Singh and Datta, 2010). Further, we report here the results of a field experiment conducted to assess the effect of gamma irradiation at 0, 0.01, 0.03, 0.05, 0.07 and 0.1 kGy on flag leaf area, stomatal conductance, transpiration and photosynthetic rate and plant and grain nutritional quality. Gamma irradiation improved plant nutrition but did not improve the nutritional quality of grains particularly relating to micronutrients. Grain carotene, a precursor for vitamin A, was higher in irradiated grains. Low grain micronutrients seem to be caused by a limitation in the source to sink nutrient translocation rather than in the nutrient uptake capacity of the plant root.

Singh, Bhupinder; Datta, Partha Sarathi

2010-08-01

322

Plants  

NSDL National Science Digital Library

Use these links to find out more about plants. This site will help you determine what a plant needs to grow. Michigan's 4-H Children's Garden This site will send you through an adventure where you try to discover if you can grow plants on the moon. Adventures of the agronauts These 2 sites are teacher resource sites on plants. Light Plants and Dark Plants, Wet Plants and Dry Ones The New York Times Daily Lesson Plan: Growing Pains ...

Quinn, Miss

2005-05-02

323

Evaluation of diel patterns of relative changes in cell turgor of tomato plants using leaf patch clamp pressure probes.  

PubMed

Relative changes in cell turgor of leaves of well-watered tomato plants were evaluated using the leaf patch clamp pressure probe (LPCP) under dynamic greenhouse climate conditions. LPCP changes, a measure for relative changes in cell turgor, were monitored at three different heights of transpiring and non-transpiring leaves of tomato plants on sunny and cloudy days simultaneously with whole plant water uptake. Clear diel patterns were observed for relative changes of cell turgor of both transpiring and non-transpiring leaves, which were stronger on sunny days than on cloudy days. A clear effect of canopy height was also observed. Non-transpiring leaves showed relative changes in cell turgor that closely followed plant water uptake throughout the day. However, in the afternoon the relative changes of cell turgor of the transpiring leaves displayed a delayed response in comparison to plant water uptake. Subsequent recovery of cell turgor loss of transpiring leaves during the following night appeared insufficient, as the pre-dawn turgescent state similar to the previous night was not attained. PMID:22540231

Lee, Kang M; Driever, Steven M; Heuvelink, Ep; Rüger, Simon; Zimmermann, Ulrich; de Gelder, Arie; Marcelis, Leo F M

2012-12-01

324

C3 plants enhance rates of photosynthesis by reassimilating photorespired and respired CO2.  

PubMed

Photosynthetic carbon gain in plants using the C(3) photosynthetic pathway is substantially inhibited by photorespiration in warm environments, particularly in atmospheres with low CO(2) concentrations. Unlike C(4) plants, C(3) plants are thought to lack any mechanism to compensate for the loss of photosynthetic productivity caused by photorespiration. Here, for the first time, we demonstrate that the C(3) plants rice and wheat employ a specific mechanism to trap and reassimilate photorespired CO(2) . A continuous layer of chloroplasts covering the portion of the mesophyll cell periphery that is exposed to the intercellular air space creates a diffusion barrier for CO(2) exiting the cell. This facilitates the capture and reassimilation of photorespired CO(2) in the chloroplast stroma. In both species, 24-38% of photorespired and respired CO(2) were reassimilated within the cell, thereby boosting photosynthesis by 8-11% at ambient atmospheric CO(2) concentration and 17-33% at a CO(2) concentration of 200 µmol mol(-1) . Widespread use of this mechanism in tropical and subtropical C(3) plants could explain why the diversity of the world's C(3) flora, and dominance of terrestrial net primary productivity, was maintained during the Pleistocene, when atmospheric CO(2) concentrations fell below 200 µmol mol(-1) . PMID:22734462

Busch, Florian A; Sage, Tammy L; Cousins, Asaph B; Sage, Rowan F

2013-01-01

325

The metabolic signature related to high plant growth rate in Arabidopsis thaliana  

PubMed Central

The decline of available fossil fuel reserves has triggered world-wide efforts to develop alternative energy sources based on plant biomass. Detailed knowledge of the relations of metabolism and biomass accumulation can be expected to yield powerful novel tools to accelerate and enhance energy plant breeding programs. We used metabolic profiling in the model Arabidopsis to study the relation between biomass and metabolic composition using a recombinant inbred line (RIL) population. A highly significant canonical correlation (0.73) was observed, revealing a close link between biomass and a specific combination of metabolites. Dividing the entire data set into training and test sets resulted in a median correlation between predicted and true biomass of 0.58. The demonstrated high predictive power of metabolic composition for biomass features this composite measure as an excellent biomarker and opens new opportunities to enhance plant breeding specifically in the context of renewable resources.

Meyer, Rhonda C.; Steinfath, Matthias; Lisec, Jan; Becher, Martina; Witucka-Wall, Hanna; Torjek, Otto; Fiehn, Oliver; Eckardt, Anne; Willmitzer, Lothar; Selbig, Joachim; Altmann, Thomas

2007-01-01

326

Conversion rates in power plant plumes based on filter pack data. Part II: The oil fired Northport plume  

Microsoft Academic Search

More than 60 airborne plume studies were conducted at a large oil-fired power station during a 3-1\\/2 year period. These studies were conducted to determine the typical rate of formation of sulfate in the plume and the conditions which most influence these atmospheric processes. The power plant chosen for this program is located in the northeast region of the US

R. W. Garber; J. Forrest; L. Newman

2008-01-01

327

Effects of nitrogen form on growth, CO2 assimilation, chlorophyll fluorescence, and photosynthetic electron allocation in cucumber and rice plants*  

PubMed Central

Cucumber and rice plants with varying ammonium (NH4 +) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO3 ?)-grown plants, cucumber plants grown under NH4 +-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH4 +-grown plants had a higher O2-independent alternative electron flux than NO3 ?-grown plants. NO3 ? reduction activity was rarely detected in leaves of NH4 +-grown cucumber plants, but was high in NH4 +-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO3 ? assimilation, an effect more significant in NO3 ?-grown plants than in NH4 +-grown plants. Meanwhile, NH4 +-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO3 ? reduction, regardless of the N form supplied, while NH4 +-sensitive plants had a high water-water cycle activity when NH4 + was supplied as the sole N source.

Zhou, Yan-hong; Zhang, Yi-li; Wang, Xue-min; Cui, Jin-xia; Xia, Xiao-jian; Shi, Kai; Yu, Jing-quan

2011-01-01

328

Effects of nitrogen form on growth, CO? assimilation, chlorophyll fluorescence, and photosynthetic electron allocation in cucumber and rice plants.  

PubMed

Cucumber and rice plants with varying ammonium (NH(4)(+)) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO(3)(-))-grown plants, cucumber plants grown under NH(4)(+)-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO(2)) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O(2)-independent alternative electron flux, and increased O(2)-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH(4)(+)-grown plants had a higher O(2)-independent alternative electron flux than NO(3)(-)-grown plants. NO(3)(-) reduction activity was rarely detected in leaves of NH(4)(+)-grown cucumber plants, but was high in NH(4)(+)-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO(3)(-) assimilation, an effect more significant in NO(3)(-)-grown plants than in NH(4)(+)-grown plants. Meanwhile, NH(4)(+)-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO(3)(-) reduction, regardless of the N form supplied, while NH(4)(+)-sensitive plants had a high water-water cycle activity when NH(4)(+) was supplied as the sole N source. PMID:21265044

Zhou, Yan-hong; Zhang, Yi-li; Wang, Xue-min; Cui, Jin-xia; Xia, Xiao-jian; Shi, Kai; Yu, Jing-quan

2011-02-01

329

Advanced regulatory control and coordinated plant-wide control strategies for IGCC targeted towards improving power ramp-rates  

SciTech Connect

As part of ongoing R&D activities at the National Energy Technology Laboratory's (NETL) Advanced Virtual Energy Simulation Training & Research (AVESTAR™) Center, this paper highlights strategies for enhancing low-level regulatory control and system-wide coordinated control strategies implemented in a high-fidelity dynamic simulator for an Integrated Gasification Combined Cycle (IGCC) power plant with carbon capture. The underlying IGCC plant dynamic model contains 20 major process areas, each of which is tightly integrated with the rest of the power plant, making individual functionally-independent processes prone to routine disturbances. Single-loop feedback control although adequate to meet the primary control objective for most processes, does not take into account in advance the effect of these disturbances, making the entire power plant undergo large offshoots and/or oscillations before the feedback action has an opportunity to impact control performance. In this paper, controller enhancements ranging from retuning feedback control loops, multiplicative feed-forward control and other control techniques such as split-range control, feedback trim and dynamic compensation, applicable on various subsections of the integrated IGCC plant, have been highlighted and improvements in control responses have been given. Compared to using classical feedback-based control structure, the enhanced IGCC regulatory control architecture reduces plant settling time and peak offshoots, achieves faster disturbance rejection, and promotes higher power ramp-rates. In addition, improvements in IGCC coordinated plant-wide control strategies for “Gasifier-Lead”, “GT-Lead” and “Plantwide” operation modes have been proposed and their responses compared. The paper is concluded with a brief discussion on the potential IGCC controller improvements resulting from using advanced process control, including model predictive control (MPC), as a supervisory control layer.

Mahapatra, P.; Zitney, S.

2012-01-01

330

The effect of land plants on weathering rates of silicate minerals  

Microsoft Academic Search

Land plants and their associated microbiota directly affect silicate mineral weathering in several ways: by generation of chelating ligands, by modifying pH through production of CO 2 or organic acids, and by altering the physical properties of a soil, particularly the exposed surface areas of minerals and the residence time of water. In laboratory experiments far from equilibrium, 1 mM

James I. Drever

1994-01-01

331

A new approach to production rate measurement in sulfuric acid plants  

Microsoft Academic Search

Since the promulgation of the new source performance standards (NSPS) methods and standards in the December 23, 1971 Federal Register, attention has been increasingly focused on accurate determination of the process parameters for assessing compliance. For utility boilers, the standard is in units of pounds of particulate per million Btu's of heat input; for sulfuric acid plants, the units are

D. J. Grove; W. S. Smith

1983-01-01

332

Comparison of effectiveness of convection-, transpiration-, and film-cooling methods with air as coolant  

NASA Technical Reports Server (NTRS)

Various parts of aircraft propulsion engines that are in contact with hot gases often require cooling. Transpiration and film cooling, new methods that supposedly utilize cooling air more effectively than conventional convection cooling, have already been proposed. This report presents material necessary for a comparison of the cooling requirements of these three methods. Correlations that are regarded by the authors as the most reliable today are employed in evaluating each of the cooling processes. Calculations for the special case in which the gas velocity is constant along the cooled wall (flat plate) are presented. The calculations reveal that a comparison of the three cooling processes can be made on quite a general basis. The superiority of transpiration cooling is clearly shown for both laminar and turbulent flow. This superiority is reduced when the effects of radiation are included; for gas-turbine blades, however, there is evidence indicating that radiation may be neglected.

Eckert, E R G; Livingood, N B

1954-01-01

333

Mechanism of Methane Transport from the Rhizosphere to the Atmosphere through Rice Plants 1  

PubMed Central

To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots could absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths. Images Figure 7

Nouchi, Isamu; Mariko, Shigeru; Aoki, Kazuyuki

1990-01-01

334

Study of the relationship between photosynthesis, respiration, transpiration, and mineral nutrition in wheat  

NASA Technical Reports Server (NTRS)

The growth of wheat (triticum aestivum) was studied in an enclosed controlled environment for a period of 70 days. The exchange of gases (photosynthesis, respiration), water (transpiration) and the consumption of mineral elements (nitrogen, phosphorus, potassium) were continuously measured. The dynamical relations observed in the different physiological functions, under the influence of growth and in response to environment modifications are presented. The influence of carbon dioxide content during growth (normal or double percentage) was made clear.

Andre, M.; Ducloux, H.; Richaud, C.; Massimino, D.; Daguenet, A.; Massimino, J.; Gerbaud, A.; Andre, M.

1987-01-01

335

Determination of soil water evaporation and transpiration from energy balance and stem flow measurements  

Microsoft Academic Search

Ham, J.M., Heiiman, J.L. and Lascano, R.J., i 990. Determination of soil water evaporation and tran- spiration from energy balance and stem flow measurements. Agric. For. Meteorol., 52: 287-301. Frequent measurements of soil water evaporation (E) and transpiration (T) are needed to quan- tify energy and water balances of sparse crops. Field experiments were conducted in Lubbock, TX to examine

Jay M. Ham; J. L. Heilman; R. J. Lascano

1990-01-01

336

Cadmium accumulation and distribution in populations of Phytolacca americana L. and the role of transpiration.  

PubMed

The concentrations of heavy metals in Phytolacca americana L. and corresponding soil samples from three contaminated sites and an uncontaminated site were studied. Hydroponic experiments were also conducted to investigate the Cd uptake ability and mechanism of P. americana. The field results showed that the average Cd concentration was 42 mg kg(-1) in P. americana leaves, with the highest concentration of 402 mg kg(-1) found at Datianwan. A significant relationship was observed between the concentrations of Cd in leaves and those of corresponding soils on a logarithmic scale. Under laboratory hydroponic conditions, the maximum Cd concentration in aerial tissues of P. americana was 637 mg kg(-1), under treatment with 100 microM Cd. The population from the uncontaminated site (Zijinshan) also had a remarkable ability to accumulate Cd in shoots to concentrations well in excess of 100 microM in the hydroponic experiment, similar to the population from contaminated site, suggesting that Cd accumulation is a constitutive trait of P. americana. In the presence of 100 microM Cd, the addition of polyethylene glycol decreased leaf transpiration, the shoot Cd concentration, and the shoot/root Cd concentration ratio. There was a significantly positive relationship between the shoot Cd concentration and the leaf transpiration of P. americana. A similar significant positive correlation was also obtained between the shoot/root Cd concentration and leaf transpiration. Moreover, pretreatment with 5 microM abscisic acid or 5 microM HgCl(2) significantly decreased the Cd concentration in P. americana shoots. These results suggest that transpiration has an important role in Cd accumulation in shoots of P. americana. PMID:20060149

Liu, Xiaoqing; Peng, Kejian; Wang, Aiguo; Lian, Chunlan; Shen, Zhenguo

2010-02-01

337

Pressurised aeration in wetland macrophytes: Some theoretical aspects of humidity-induced convection and thermal transpiration  

Microsoft Academic Search

The pressurised gas-flows, humidity-induced convection (HIC) and thermal transpiration (TT), which are important for aeration\\u000a and for greenhouse gas emissions in some wetland macrophytes, are described and discussed. Results obtained from simple mathematical\\u000a modelling of the processes are presented to illustrate some of their more relevant features. It is emphasised that both processes\\u000a require the presence of a micro-porous partition

William Armstrong; Jean Armstrong; Peter M. Beckett

1996-01-01

338

Experimental Investigation of a Turbulent Transpiration-induced Channel Flow Using Particle Image Velocimetry Technique  

Microsoft Academic Search

Turbulence in a channel flow with a fully transpired wall has been investigated experimentally. 2D Particle Image Velocimetry is used to measure the instantaneous flow fields within the channel for two different porous surfaces: 6.35 mm honeycomb and 3.175 mm honeycomb. The 6.35 mm honeycomb creates a larger fluctuation of the injection velocity than the 3.175 mm honeycomb by a

Zhiqun Deng; Ronald J. Adrian

2002-01-01

339

Boundary Singularity for Thermal Transpiration Problem of the Linearized Boltzmann Equation  

NASA Astrophysics Data System (ADS)

We study the boundary singularity of the fluid velocity for the thermal transpiration problem in the kinetic theory. Logarithmic singularity has been demonstrated through the asymptotic and computational analysis. The goal of this paper is to confirm this logarithmic singularity through exact analysis. We use an iterated scheme, with the "gain" part of the collision operator as a source. The iterated scheme is appropriate for large Knudsen numbers considered here and yields an explicit leading term.

Chen, I.-Kun; Liu, Tai-Ping; Takata, Shigeru

2014-05-01

340

Differential gene expression of wheat progeny with contrasting levels of transpiration efficiency  

Microsoft Academic Search

High water use efficiency or transpiration efficiency (TE) in wheat is a desirable physiological trait for increasing grain\\u000a yield under water-limited environments. The identification of genes associated with this trait would facilitate the selection\\u000a for genotypes with higher TE using molecular markers. We performed an expression profiling (microarray) analysis of approximately\\u000a 16,000 unique wheat ESTs to identify genes that were

Gang-Ping Xue; C. Lynne McIntyre; Scott Chapman; Neil I. Bower; Antonio Reverter; Bryan Clarke; Ray Shorter

2006-01-01

341

A hybrid dual-source model for potential evaporation and transpiration partitioning  

NASA Astrophysics Data System (ADS)

SummaryPotential ET (PET) and partitioning of evaporation and transpiration are important information for hydrologic, ecologic, forest, and agricultural studies. Most PET models were developed in flat areas for agricultural purposes, with potential evaporation (PE) and potential transpiration (PT) lumped together. To quantify the evaporative demand for sloped surfaces with a wide range of vegetation coverage, a topography- and vegetation-based surface energy partitioning algorithm for PE and PT estimates (TVET) is developed. In this paper, vegetation-based part of the TVET model is presented. TVET employs a hybrid of layer and patch approaches in partitioning energy and routing vapor and sensible heat. It first uses a layer approach to partition available energy for the canopy and the soil components. The available energy of each component is then partitioned into potential latent heat and sensible heat, using a patch approach. Hybrid of these two approaches results in simple model formulae, while coupling the two components in terms of energy partitioning and aerodynamic resistances for heat and vapor transfer. TVET is different from a layer-approach model in that it distinguishes the difference in evaporation from inter-canopy soil and from under-canopy soil, and limits convective transfer contribution to transpiration only for vegetation-cover fraction. TVET is different from a patch-approach model in that it allows evaporation occurring from under-canopy soil, and that vegetation effect on both evaporation and transpiration is well considered. These features make TVET sensitive to vegetation effect on surface energy partitioning. The model is demonstrated and tested with Penman-Monteith and Shuttleworth-Wallace models, and with observations, at four sites covering mountain, basin floor, and riparian environments. The results indicate that TVET can be used to estimate PE and PT partitioning for a wide range of surfaces with different fractional vegetation cover. Good estimates of riparian surface evapotranspiration at the Rio Grande in the central New Mexico suggest its capacity to estimate ET in similar environments.

Guan, Huade; Wilson, John L.

2009-10-01

342

A high-rate secondary treatment based on a moving bed bioreactor and multimedia filters for small wastewater treatment plants.  

PubMed

For small wastewater treatment plants (WWPTs), high-rate secondary treatment systems with good treatment efficiency and easy, stable, and robust operation are called for. In this paper an experimental study on a high rate secondary treatment based on moving bed biofilm reactor (MBBR) and multimedia filters is presented. A high rate MBBR converts easily biodegradable SCOD in short HRT (0.5 h) directly after screening, then a Kaldnes-Filtralite-Sand (KFS) filter removes the particulate COD and detached biofilms at filtration rates of 10-20 m/h. The whole system gave effluent SS and COD less than 30 mg/L and 100 mg/L when total detention time is less than 1 h and small dosage of chemicals (iron and/or cationic polymer) is used. A new scenario of high rate secondary system with a primary Kaldnes coarse media filter in front of high rate MBBR and the KFS filter is proposed and discussed. This scenario with total HRT less than 2h is more suitable for high influent SS concentrations and may also be extended for nitrogen and phosphorous removal. Compared to conventional secondary treatment, the high rate secondary treatment will be using only 1/5-1/10 of the space, resulting in considerable savings for construction, energy and operation. PMID:14524687

Liao, Z; Rasmussen, V; Odegaard, H

2003-01-01

343

Systems dynamic modeling of a guard cell Cl- channel mutant uncovers an emergent homeostatic network regulating stomatal transpiration.  

PubMed

Stomata account for much of the 70% of global water usage associated with agriculture and have a profound impact on the water and carbon cycles of the world. Stomata have long been modeled mathematically, but until now, no systems analysis of a plant cell has yielded detail sufficient to guide phenotypic and mutational analysis. Here, we demonstrate the predictive power of a systems dynamic model in Arabidopsis (Arabidopsis thaliana) to explain the paradoxical suppression of channels that facilitate K(+) uptake, slowing stomatal opening, by mutation of the SLAC1 anion channel, which mediates solute loss for closure. The model showed how anion accumulation in the mutant suppressed the H(+) load on the cytosol and promoted Ca(2+) influx to elevate cytosolic pH (pH(i)) and free cytosolic Ca(2+) concentration ([Ca(2+)](i)), in turn regulating the K(+) channels. We have confirmed these predictions, measuring pH(i) and [Ca(2+)](i) in vivo, and report that experimental manipulation of pH(i) and [Ca(2+)](i) is sufficient to recover K(+) channel activities and accelerate stomatal opening in the slac1 mutant. Thus, we uncover a previously unrecognized signaling network that ameliorates the effects of the slac1 mutant on transpiration by regulating the K(+) channels. Additionally, these findings underscore the importance of H(+)-coupled anion transport for pH(i) homeostasis. PMID:23090586

Wang, Yizhou; Papanatsiou, Maria; Eisenach, Cornelia; Karnik, Rucha; Williams, Mary; Hills, Adrian; Lew, Virgilio L; Blatt, Michael R

2012-12-01

344

Transpiration of gaseous elemental mercury through vegetation in a subtropical wetland in florida  

SciTech Connect

Four seasonal sampling campaigns were carried out in the Florida Everglades to measure elemental Hg vapor (Hg{sup o}) fluxes over emergent macrophytes using a modified Bowen ratio gradient approach. The predominant flux of Hg{sup o} over both invasive cattail and native sawgrass stands was emission; mean day time fluxes over cattail ranged from {approx}20 (winter) to {approx}40 (summer) ng m{sup -2} h{sup -1}. Sawgrass fluxes were about half those over cattail during comparable periods. Emission from vegetation significantly exceeded evasion of Hg{sup o} from the underlying water surface ({approx}1-2 ng m{sup -2} h{sup -1}) measured simultaneously using floating chambers. Among several environmental factors (e.g. CO{sub 2} flux, water vapor flux, wind speed, water, air and leaf temperature, and solar radiation), water vapor exhibited the strongest correlation with Hg{sup o} flux, and transpiration is suggested as an appropriate term to describe this phenomenon. The lack of significant Hg{sup o} emissions from a live, but uprooted (floating) cattail stand suggests that a likely source of the transpired Hg{sup o} is the underlying sediments. The pattern of Hg{sup o} fluxes typically measured indicated a diel cycle with two peaks, possibly related to different gas exchange dynamics: one in early morning related to lacunal gas release, and a second at midday related to transpiration; nighttime fluxes approached zero.

Lindberg, Steven Eric [ORNL; Dong, Weijin [ORNL; Meyers, Tilden [NOAA, Oak Ridge, TN

2002-07-01

345

Monte Carlo analysis of thermal transpiration effects in capacitance diaphragm gauges with helicoidal baffle system  

NASA Astrophysics Data System (ADS)

The Capacitance Diaphragm Gauge (CDG) is one of the most widely used vacuum gauges in low and middle vacuum ranges. This device consists basically of a very thin ceramic or metal diaphragm which forms one of the electrodes of a cap acitor. The pressure is determined by measuring the variation in the capacitance due to the deflection of the diaphragm caused by the pressure difference established across the membrane. In order to minimize zero drift, some CDGs are operated keeping the sensor at a higher temperature. This difference in the temperature between the sensor and the vacuum chamber makes the behaviour of the gauge non-linear due to thermal transpiration effects. This effect becomes more significant when we move from the transitional flow to the free molecular regime. Besides, CDGs may incorporate different baffle systems to avoid the condensation on the membrane or its contamination. In this work, the thermal transpiration effect on the behaviour of a rarefied gas and on the measurements in a CDG with a helicoidal baffle system is investigated by using the Direct Simulation Monte Carlo method (DSMC). The study covers the behaviour of the system under the whole range of rarefaction, from the continuum up to the free molecular limit and the results are compared with empirical results. Moreover, the influence of the boundary conditions on the thermal transpiration effects is investigated by using Maxwell boundary conditions.

Vargas, M.; Wüest, M.; Stefanov, S.

2012-05-01

346

High outcrossing rates maintain male and hermaphrodite individuals in populations of the flowering plant Datisca glomerata  

Microsoft Academic Search

MODELS for the maintenance of androdioecy (the presence of male and hermaphrodite individuals in a breeding population) in plants predict that males must have a fertility at least double the male fertility of hermaphrodites in order to be maintained by selection1-3. An even greater advantage is required in partially self-fertilizing populations1-3 as the gain in fitness through increased pollen production

Peter Fritsch; Loren H. Rieseberg

1992-01-01

347

Effects of plant community and phosphorus loading rate on constructed wetland performance in Florida, USA  

Microsoft Academic Search

We evaluated the effectiveness of constructed wetlands with varying plant communities for phosphorus (P) reduction from the\\u000a Everglades Agricultural Area runoff in south Florida. Weekly or biweekly water samples from the inflow and outflow regions\\u000a of 11 test cells (2,000 m2) were analyzed for various forms of P and other selected water quality variables between January 2002 and August 2004.

Binhe Gu; Thomas Dreschel

2008-01-01

348

Chapter 18 Hurdles to Engineering Greater Photosynthetic Rates in Crop Plants: C 4 Rice  

Microsoft Academic Search

\\u000a It is now 20 years since a suggestion was first made of introducing a C4 photosynthetic pathway into rice plants to increase rice productivity. With the amount of arable land decreasing, the human\\u000a population increasing and rice productivity plateauing there is an urgent need to significantly increase rice productivity.\\u000a One way of increasing rice productivity is by introducing the C4

James N. Burnell

349

Temperature and Transpiration Resistances of Xanthium Leaves as Affected by Air Temperature, Humidity, and Wind Speed 1  

PubMed Central

Transpiration and temperatures of single, attached leaves of Xanthium strumarium L. were measured in high intensity white light (1.2 calories per square centimeter per minute on a surface normal to the radiation), with abundant water supply, at wind speeds of 90, 225, and 450 centimeters per second, and during exposure to moist and dry air. Partitioning of absorbed radiation between transpiration and convection was determined, and transpiration resistances were computed. Leaf resistances decreased with increasing temperature (down to a minimum of 0.36 seconds per centimeter). Silicone rubber replicas of leaf surfaces proved that the decrease was due to increased stomatal apertures. At constant air temperature, leaf resistances were higher in dry than in moist air with the result that transpiration varied less than would have been predicted on the basis of the water-vapor pressure difference between leaf and air. The dependence of stomatal conductance on temperature and moisture content of the air caused the following effects. At air temperatures below 35 C, average leaf temperatures were above air temperature by an amount dependent on wind velocity; increasing wind diminished transpiration. At air temperatures above 35 C, leaf temperatures were below air temperatures, and increasing wind markedly increased transpiration. Leaf temperatures equaled air temperature near 35 C at all wind speeds and in moist as well as in dry air.

Drake, B. G.; Raschke, K.; Salisbury, F. B.

1970-01-01

350

Modeled dosage-response relationship on the net photosynthetic rate for the sensitivity to acid rain of 21 plant species.  

PubMed

This study investigated the sensitivity of plant species to acid rain based on the modeled dosage-response relationship on the net photosynthetic rate (P (N)) of 21 types of plant species, subjected to the exposure of simulated acid rain (SAR) for 5 times during a period of 50 days. Variable responses of P (N) to SAR occurred depending on the type of plant. A majority (13 species) of the dosage-response relationship could be described by an S-shaped curve and be fitted with the Boltzmann model. Model fitting allowed quantitative evaluation of the dosage-response relationship and an accurate estimation of the EC(10), termed as the pH of the acid rain resulting in a P (N) 10 % lower than the reference value. The top 9 species (Camellia sasanqua, Cinnamomum camphora, etc. EC(10) ? 3.0) are highly endurable to very acid rain. The rare, relict plant Metasequoia glyptostroboides was the most sensitive species (EC(10) = 5.1) recommended for protection. PMID:22562418

Deng, Shihuai; Gou, Shuzhen; Sun, Baiye; Lv, Wenlin; Li, Yuanwei; Peng, Hong; Xiao, Hong; Yang, Gang; Wang, Yingjun

2012-08-01

351

Water uptake efficiency of a maize plant - A simulation case study  

NASA Astrophysics Data System (ADS)

Water uptake by plant roots is a complex mechanism controlled by biological and physical properties of the soil-plant-atmosphere system and affects a major component of the water cycle, transpiration. This uptake of water by plants is one of the major factors of plant development. Since water uptake occurs at the roots, root architecture and hydraulic properties both play a crucial role in plant productivity. A fundamental understanding of the main processes of water uptake will enable better breeding of drought resistant plants and the improvement of irrigation strategies. In this work we analyzed the differences of root water uptake between idealized genotypes of a plant using mathematical modelling The numerical simulations were performed by the R-SWMS software (Javaux et al., 2008). The model describes 3-D water movement in soil by solving Richard's equation with a sink term representing root uptake. Water flow within the root xylem network and between soil and root is modelled based on water pressure gradients and calculated according to Doussan's model. The sink term is calculated by integration of local uptakes within rooted representative elementary volumes of soil. The plant water demand is described by a boundary condition at the base of the shoot. We compare the water uptake efficiency of three types of root system architectures of a maize plant. Two are actual architectures from genotypes showing significant differences regarding the internodal distance, the root growth rate and the insertion angle of their primary roots. The third one is an ideotype according to Lynch of the maize plant designed to perform better in one dry environment. We generated with RootBox five repetitions of these three root systems with the same total root volume and simulated two drought scenarios at the flowering stage (lack of water at the top or at the bottom of the soil domain). We did these simulations for two distinct distributions of local conductivities of root segments based on literature values. This numerical experiment shows significantly different behaviors of the root systems in terms of dynamics of the water uptake, duration of the water stress or cumulative transpiration. The ranking of the maize architectures varied according to the considered drought scenario. The performance of a root system depends on the environment and on its hydraulic architecture suggesting that we always need to take the genotype-environment interaction into account for recommending breeding options. This study also shows that an ideotype must be built for one specific environment: the one we created experienced difficulties to transpire when placed in different conditions it has been designed for. By mathematical simulation we increased the understanding of the most important underlying processes governing water uptake in a root system.

Meunier, Félicien; Leitner, Daniel; Bodner, Gernot; Javaux, Mathieu; Schnepf, Andrea

2014-05-01

352

Comparison of emission from the water column and wetland plants at the Berry's Creek estuary, Hackensack Meadowlands, New Jersey.  

NASA Astrophysics Data System (ADS)

Berry's Creek is a tidal tributary to the Hackensack River, and was historically subjected to discharges of mercury from the Ventron-Velsicol mercury processing site. The emission of mercury from this site to the atmosphere can follow three pathways: 1) emission from the water column, 2) transpiration through plants, and 3) emission from exposed wetland sediments. In this poster, we present a comparison of the first two emission pathways which have been studied at this site to date. Emission of mercury from the water column mercury to the atmosphere results from complex biogeochemical reactions between photoreactive dissolved organic carbon, ultraviolet light, and dissolved aqueous mercury. Emission rates measured using a dynamic flux chamber ranged from -0.64 to 34 ng/m2-h. Solar radiation and DOC spectral slope appear to exert the strongest control on mercury emission, with solar radiation alone accounting for up to 98% of the diel changes in mercury emission. Emission of mercury from plants appears to be a complex process that includes emission of mercury along with water vapor during transpiration as well as deposition to plant surfaces. Emission rates from Phragmites australis leaves ranged from -0.64 to 0.17 ng/m2-h. Annual and diel cycles are considered in an estimation of the magnitude of total mercury emitted through each pathway over the duration of 1 year.

Peters, S.; Wollenberg, J.; Bubb, M.

2008-12-01

353

Silencing of StKCS6 in potato periderm leads to reduced chain lengths of suberin and wax compounds and increased peridermal transpiration  

PubMed Central

Very long chain aliphatic compounds occur in the suberin polymer and associated wax. Up to now only few genes involved in suberin biosynthesis have been identified. This is a report on the isolation of a potato (Solanum tuberosum) 3-ketoacyl-CoA synthase (KCS) gene and the study of its molecular and physiological relevance by means of a reverse genetic approach. This gene, called StKCS6, was stably silenced by RNA interference (RNAi) in potato. Analysis of the chemical composition of silenced potato tuber periderms indicated that StKCS6 down-regulation has a significant and fairly specific effect on the chain length distribution of very long-chain fatty acids (VLCFAs) and derivatives, occurring in the suberin polymer and peridermal wax. All compounds with chain lengths of C28 and higher were significantly reduced in silenced periderms, whereas compounds with chain lengths of C26 and lower accumulated. Thus, StKCS6 is preferentially involved in the formation of suberin and wax lipidic monomers with chain lengths of C28 and higher. As a result, peridermal transpiration of the silenced lines was about 1.5-times higher than that of the wild type. Our results convincingly show that StKCS6 is involved in both suberin and wax biosynthesis and that a reduction of the monomeric carbon chain lengths leads to increased rates of peridermal transpiration.

Serra, Olga; Soler, Marcal; Hohn, Carolin; Franke, Rochus; Schreiber, Lukas; Prat, Salome; Molinas, Marisa; Figueras, Merce

2009-01-01

354

Silencing of StKCS6 in potato periderm leads to reduced chain lengths of suberin and wax compounds and increased peridermal transpiration.  

PubMed

Very long chain aliphatic compounds occur in the suberin polymer and associated wax. Up to now only few genes involved in suberin biosynthesis have been identified. This is a report on the isolation of a potato (Solanum tuberosum) 3-ketoacyl-CoA synthase (KCS) gene and the study of its molecular and physiological relevance by means of a reverse genetic approach. This gene, called StKCS6, was stably silenced by RNA interference (RNAi) in potato. Analysis of the chemical composition of silenced potato tuber periderms indicated that StKCS6 down-regulation has a significant and fairly specific effect on the chain length distribution of very long-chain fatty acids (VLCFAs) and derivatives, occurring in the suberin polymer and peridermal wax. All compounds with chain lengths of C(28) and higher were significantly reduced in silenced periderms, whereas compounds with chain lengths of C(26) and lower accumulated. Thus, StKCS6 is preferentially involved in the formation of suberin and wax lipidic monomers with chain lengths of C(28) and higher. As a result, peridermal transpiration of the silenced lines was about 1.5-times higher than that of the wild type. Our results convincingly show that StKCS6 is involved in both suberin and wax biosynthesis and that a reduction of the monomeric carbon chain lengths leads to increased rates of peridermal transpiration. PMID:19112170

Serra, Olga; Soler, Marçal; Hohn, Carolin; Franke, Rochus; Schreiber, Lukas; Prat, Salomé; Molinas, Marisa; Figueras, Mercè

2009-01-01

355

Effects of Arbuscular-Mycorrhizal Glomus Species on Drought Tolerance: Physiological and Nutritional Plant Responses  

PubMed Central

The tolerance of lettuce plants (Lactuca sativa L. cv. Romana) to drought stress differed with the arbuscular-mycorrhizal fungal isolate with which the plants were associated. Seven fungal species belonging to the genus Glomus were studied for their ability to enhance the drought tolerance of lettuce plants. These fungi had different traits that affected the drought resistance of host plants. The ranking of arbuscular-mycorrhizal fungal effects on drought tolerance, based on the relative decreases in shoot dry weight, was as follows: Glomus deserticola > Glomus fasciculatum > Glomus mosseae > Glomus etunicatum > Glomus intraradices > Glomus caledonium > Glomus occultum. In this comparative study specific mycorrhizal fungi had consistent effects on plant growth, mineral uptake, the CO(inf2) exchange rate, water use efficiency, transpiration, stomatal conductance, photosynthetic phosphorus use efficiency, and proline accumulation under either well-watered or drought-stressed conditions. The ability of the isolates to maintain plant growth effectively under water stress conditions was related to higher transpiration rates, levels of leaf conductance, and proline, N, and P contents. Differences in proline accumulation in leaves among the fungal symbioses suggested that the fungi were able to induce different degrees of osmotic adjustment. The detrimental effects of drought were not related to decreases in photosynthesis or water use efficiency. Neither of these parameters was related to P nutrition. The differences in P and K acquisition, transpiration, and stomatal conductance were related to the mycorrhizal efficiencies of the different fungi. Our observations revealed the propensities of different Glomus species to assert their protective effects during plant water stress. The greater effectiveness of G. deserticola in improving water deficit tolerance was associated with the lowest level of growth reduction (9%) under stress conditions. The growth of plants colonized by G. occultum was reduced by 70% after a progressive drought stress period. In general, the different protective effects of the mycorrhizal isolates were not associated with colonizing ability. Nevertheless, G. deserticola was the most efficient fungus and exhibited the highest levels of mycorrhizal colonization, as well as the greatest stimulation of physiological parameters.

Ruiz-Lozano, J. M.; Azcon, R.; Gomez, M.

1995-01-01

356

Plant Gas Exchange at High Wind Speeds 1  

PubMed Central

High altitude Rhododendron ferrugineum L. and Pinus cembra L. seedlings were exposed to winds at 15 meters per second for 24-hour periods. Wind-sensitive stomata of Rhododendron seedlings immediately initiated a closing response which resulted in decreased photosynthesis and an even greater reduction in transpiration. Stomatal aperture and transpiration rates of P. cembra were only slightly reduced by high speed winds. However, photosynthesis was substantially reduced because of changes in needle display to available irradiation.

Caldwell, Martyn M.

1970-01-01

357

Component failure-rate data with potential applicability to a nuclear fuel reprocessing plant  

Microsoft Academic Search

Approximately 1223 pieces of component failure-rate data, under 136 subject categories, have been compiled from published literature and computer searches of a number of data bases. Component selections were based on potential applicability to facilities for reprocessing spent nuclear fuels. The data will be useful in quantifying fault trees for probabilistic safety analyses and risk assessments.

A. H. Dexter; W. C. Perkins

1982-01-01

358

Survey of U.S. Costs and Water Rates for Deslaination and Membrane Softening Plants.  

National Technical Information Service (NTIS)

The report is based ona survey by Leitner and Associates, Inc., of U.S. costs and water rates for utilities that use desalination and membrane softening. The report provides information of the following four processes: reverse osmosis for brackish/groundw...

1997-01-01

359

Modeling evapotranspiration based on plant hydraulic theory can predict spatial variability across an elevation gradient and link to biogeochemical fluxes  

NASA Astrophysics Data System (ADS)

In woody plant systems transpiration is often the dominant component of total evapotranspiration, and so it is key to understanding water and energy cycles. Moreover, transpiration is tightly coupled to carbon and nutrient fluxes, and so it is also vital to understanding spatial variability of biogeochemical fluxes. However, the spatial variability of transpiration and its links to biogeochemical fluxes, within- and among-ecosystems, has been a challenge to constrain because of complex feedbacks between physical and biological controls. Plant hydraulics provides an emerging theory with the rigor needed to develop testable hypotheses and build useful models for scaling these coupled fluxes from individual plants to regional scales. This theory predicts that vegetative controls over water, energy, carbon, and nutrient fluxes can be determined from the limitation of plant water transport through the soil-xylem-stomata pathway. Limits to plant water transport can be predicted from measurable plant structure and function (e.g., vulnerability to cavitation). We present a next-generation coupled transpiration-biogeochemistry model based on this emerging theory. The model, TREEScav, is capable of predicting transpiration, along with carbon and nutrient flows, constrained by plant structure and function. The model incorporates tightly coupled mechanisms of the demand and supply of water through the soil-xylem-stomata system, with the feedbacks to photosynthesis and utilizable carbohydrates. The model is evaluated by testing it against transpiration and carbon flux data along an elevation gradient of woody plants comprising sagebrush steppe, mid-elevation lodgepole pine forests, and subalpine spruce/fir forests in the Rocky Mountains. The model accurately predicts transpiration and carbon fluxes as measured from gas exchange, sap flux, and eddy covariance towers. The results of this work demonstrate that credible spatial predictions of transpiration and related biogeochemical fluxes will be possible at regional scales using relatively easily obtained vegetation structural and functional information.

Mackay, D. S.; Frank, J.; Reed, D.; Whitehouse, F.; Ewers, B. E.; Pendall, E.; Massman, W. J.; Sperry, J. S.

2012-04-01

360

Rapid Evolution of Enormous, Multichromosomal Genomes in Flowering Plant Mitochondria with Exceptionally High Mutation Rates  

PubMed Central

Genome size and complexity vary tremendously among eukaryotic species and their organelles. Comparisons across deeply divergent eukaryotic lineages have suggested that variation in mutation rates may explain this diversity, with increased mutational burdens favoring reduced genome size and complexity. The discovery that mitochondrial mutation rates can differ by orders of magnitude among closely related angiosperm species presents a unique opportunity to test this hypothesis. We sequenced the mitochondrial genomes from two species in the angiosperm genus Silene with recent and dramatic accelerations in their mitochondrial mutation rates. Contrary to theoretical predictions, these genomes have experienced a massive proliferation of noncoding content. At 6.7 and 11.3 Mb, they are by far the largest known mitochondrial genomes, larger than most bacterial genomes and even some nuclear genomes. In contrast, two slowly evolving Silene mitochondrial genomes are smaller than average for angiosperms. Consequently, this genus captures approximately 98% of known variation in organelle genome size. The expanded genomes reveal several architectural changes, including the evolution of complex multichromosomal structures (with 59 and 128 circular-mapping chromosomes, ranging in size from 44 to 192 kb). They also exhibit a substantial reduction in recombination and gene conversion activity as measured by the relative frequency of alternative genome conformations and the level of sequence divergence between repeat copies. The evolution of mutation rate, genome size, and chromosome structure can therefore be extremely rapid and interrelated in ways not predicted by current evolutionary theories. Our results raise the hypothesis that changes in recombinational processes, including gene conversion, may be a central force driving the evolution of both mutation rate and genome structure.

Sloan, Daniel B.; Alverson, Andrew J.; Chuckalovcak, John P.; Wu, Martin; McCauley, David E.; Palmer, Jeffrey D.; Taylor, Douglas R.

2012-01-01

361

Rapid evolution of enormous, multichromosomal genomes in flowering plant mitochondria with exceptionally high mutation rates.  

PubMed

Genome size and complexity vary tremendously among eukaryotic species and their organelles. Comparisons across deeply divergent eukaryotic lineages have suggested that variation in mutation rates may explain this diversity, with increased mutational burdens favoring reduced genome size and complexity. The discovery that mitochondrial mutation rates can differ by orders of magnitude among closely related angiosperm species presents a unique opportunity to test this hypothesis. We sequenced the mitochondrial genomes from two species in the angiosperm genus Silene with recent and dramatic accelerations in their mitochondrial mutation rates. Contrary to theoretical predictions, these genomes have experienced a massive proliferation of noncoding content. At 6.7 and 11.3 Mb, they are by far the largest known mitochondrial genomes, larger than most bacterial genomes and even some nuclear genomes. In contrast, two slowly evolving Silene mitochondrial genomes are smaller than average for angiosperms. Consequently, this genus captures approximately 98% of known variation in organelle genome size. The expanded genomes reveal several architectural changes, including the evolution of complex multichromosomal structures (with 59 and 128 circular-mapping chromosomes, ranging in size from 44 to 192 kb). They also exhibit a substantial reduction in recombination and gene conversion activity as measured by the relative frequency of alternative genome conformations and the level of sequence divergence between repeat copies. The evolution of mutation rate, genome size, and chromosome structure can therefore be extremely rapid and interrelated in ways not predicted by current evolutionary theories. Our results raise the hypothesis that changes in recombinational processes, including gene conversion, may be a central force driving the evolution of both mutation rate and genome structure. PMID:22272183

Sloan, Daniel B; Alverson, Andrew J; Chuckalovcak, John P; Wu, Martin; McCauley, David E; Palmer, Jeffrey D; Taylor, Douglas R

2012-01-01

362

Soil- and plant- water uptake in saline environments and their consequences to plant adaptation in fluctuating climates  

NASA Astrophysics Data System (ADS)

Ecological processes determining plant colonization are quite peculiar and competition among different species is governed by a set of unique adaptations to stress conditions caused by drought, hypoxic or hyper-saline conditions. These adaptations and possible positive feedbacks often lead to the formation of patterns of vegetation colonization and spatial heterogeneity (zonation), and play a primary role in the stabilization of sediments. It is these issues that frame the scope of this study. The main objective of this work is to track one of the fundamental pathways between plant adaptation (quantified in terms of physiological and ecological attributes such as leaf area or root density profile) and feedbacks (quantified by plant-mediated alterations to water availability and salinity levels): root water uptake. Because root-water uptake is the main conduit connecting transpiring leaves to reservoirs of soil water, the means by which salinity modifies the processes governing its two end-points and any two-way interactions between them serves as a logical starting point. Salinity effects on leaf transpiration and photosynthesis are first explored via stomatal optimization principles that maximize carbon gain at a given water loss for autonomous leaves. Salinity directly affects leaf physiological attributes such as mesophyll conductance and photosynthetic parameters and hence over-all conductance to transpiration as well as different strategies to cope with the high salinity (e.g. through salt seclusion, compartmentation and osmotic adjustments). A coupled model of subsurface flow based on a modified Richards’ equation that accounts for the effects of increasing salinity, anaerobic conditions, water stress and compensation factors is developed. Plant water uptake is considered as a soil moisture sink term with a potential rate dictated by the carbon demands of the leaves, and an actual rate that accounts for both - hydraulic and salinity limitations. Using this model, the root distribution shape function (e.g. constant, linear, exponential, or power-law) that optimally satisfies these carbon demands and simultaneous hydraulic and salinity constraints of the soil-root system is then determined for a set of forcing variables and boundary conditions. Adaptation speeds and feedback strengths to future climatic fluctuations are explored as ‘departures’ from this equilibrium profile state.

Volpe, V.; Albertson, J. D.; Katul, G. G.; Marani, M.

2010-12-01

363

Engineering the use of green plants to reduce produced water disposal volume.  

SciTech Connect

In 1990, the Laboratory began an investigation into biological approaches for the reduction of water produced from oil and gas wells. In the spring of 1995, the Company began an on-site experiment at an oil/gas lease in Oklahoma using one of these approaches. The process, known as phytoremediation, utilizes the ability of certain salt tolerant plants to draw the produced water through their roots, transpire the water from their leaves, and thereby reduce overall water disposal volumes and costs. At the Company experimental site, produced water flows through a trough where green plants (primarily cordgrass) have been planted in pea gravel. The produced water is drawn into the plant through its roots, evapotranspirates and deposits a salt residue on the plant leaves. The plant leaves are then harvested and used by a local rancher as cattle feed. The produced water is tested to assure it contains nothing harmful to cattle. In 1996, the Company set up another trough to compare evaporation rates using plants versus using an open container without plants. Data taken during all four seasons (water flow rate, temperature, pH, and conductivity) have shown that using plants to evapotranspirate produced water is safe, more cost effective than traditional methods and is environmentally sound.

Hinchman, R.; Mollock, G. N.; Negri, M. C.; Settle, T.

1998-01-29

364

Multivariate statistical analysis of a high rate biofilm process treating kraft mill bleach plant effluent.  

PubMed

This study reports on a multivariate analysis of the moving bed biofilm reactor (MBBR) wastewater treatment system at a Canadian pulp mill. The modelling approach involved a data overview by principal component analysis (PCA) followed by partial least squares (PLS) modelling with the objective of explaining and predicting changes in the BOD output of the reactor. Over two years of data with 87 process measurements were used to build the models. Variables were collected from the MBBR control scheme as well as upstream in the bleach plant and in digestion. To account for process dynamics, a variable lagging approach was used for variables with significant temporal correlations. It was found that wood type pulped at the mill was a significant variable governing reactor performance. Other important variables included flow parameters, faults in the temperature or pH control of the reactor, and some potential indirect indicators of biomass activity (residual nitrogen and pH out). The most predictive model was found to have an RMSEP value of 606 kgBOD/d, representing a 14.5% average error. This was a good fit, given the measurement error of the BOD test. Overall, the statistical approach was effective in describing and predicting MBBR treatment performance. PMID:17486834

Goode, C; LeRoy, J; Allen, D G

2007-01-01

365

Phenological changes in rate of respiration and annual carbon balance in a perennial herbaceous plant, Primula sieboldii.  

PubMed

Primula sieboldii E. Morren is a clonal herbaceous species with a short foliar period from spring to early summer. We have studied the temperature-dependence of the rate of respiration at the whole-ramet level throughout the phenological stages of P. sieboldii to reveal its photosynthate-utilization strategy. P. sieboldii ramets were grown in a chamber enabling simulation of seasonal changes in temperature. Rates of respiration were measured at three phenological stages--the foliar period, the before-chilling defoliated (BCD) period, and the after--chilling defoliated (ACD) period. In the foliar period the rate of respiration, on a biomass basis at 20 degrees C (R (20)), of the above-ground plant parts was 2.5 times that of the below-ground parts. The R (20) of the below-ground parts in the foliar period was 6.5 times that in the BCD period and 1.6 times that in the ACD period. Estimation of the ramet carbon balance under these growth conditions showed that ramets respired 87% of total photosynthate production during the experimental period (8.5 months). Respiratory consumption in the foliar period accounted for 70% of the yearly total, whereas 24 and 6% were consumed in the BCD and ACD periods, respectively. An extremely low rate of respiration during the long defoliated period led to a positive net annual carbon balance for P. sieboldii ramets. PMID:17492255

Noda, Hibiki; Muraoka, Hiroyuki; Tang, Yanhong; Washitani, Izumi

2007-05-01

366

Response of Insect Relative Growth Rate to Temperature and Host-Plant Phenology: Estimation and Validation from Field Data  

PubMed Central

Between 1975 to 2011, aphid Relative Growth Rates (RGR) were modelled as a function of mean outdoor temperature and host plant phenology. The model was applied to the grain aphid Sitobion avenae using data on aphid counts in winter wheat at two different climate regions in France (oceanic climate, Rennes (western France); continental climate, Paris). Mean observed aphid RGR was higher in Paris compared to the Rennes region. RGR increased with mean temperature, which is explained by aphid reproduction, growth and development being dependent on ambient temperature. From the stem extension to the heading stage in wheat, there was either a plateau in RGR values (Rennes) or an increase with a maximum at heading (Paris) due to high intrinsic rates of increase in aphids and also to aphid immigration. From the wheat flowering to the ripening stage, RGR decreased in both regions due to the low intrinsic rate of increase in aphids and high emigration rate linked to reduced nutrient quality in maturing wheat. The model validation process showed that the fitted models have more predictive power in the Paris region than in the Rennes region.

Ciss, Mamadou; Parisey, Nicolas; Fournier, Gwenaelle; Taupin, Pierre; Dedryver, Charles-Antoine; Pierre, Jean-Sebastien

2014-01-01

367

Effect of microgravity on sap flow in plant stems  

NASA Astrophysics Data System (ADS)

A fundamental study was conducted to assess the possibility of plant growth suppression caused by poor movement of air in closed plant growth facilities in space farming. Sap water flow in plant stems, which plays an important role to transport fluid and nutrients from roots to leaves, will be suppressed through suppression of transpiration because of little natural convection of air under microgravity conditions. In this study, the sap flow in tomato stems was examined using a heat flow method at 0.01 and 1.0 g for 20 seconds each during parabolic airplane flights in order to clarify the effect of microgravity on the sap flow in stems. Heat generated with a tiny heater installed in the stem was transferred upstream and downstream by conduction and upstream by the sap flow through xylems of the vascular tissue. The internal heat convection corresponding to the sap flow was analyzed with thermal images captured on stems near heated points. In results, the sap flow in stems at 0.01 g was suppressed under a retarded air condition at a wind speed of 0.1 m s-1 compared with that at 1 g. No suppression of the sap flow was observed under a stirred air condition at a wind speed of 0.5 m s-1. Suppressed sap water flow in stems would be caused by suppression of transpiration in leaves and would cause restriction of water and nutrient uptake in roots. The forced air movement is, therefore, essential to culture healthy plants at a high growth rate under microgravity conditions in space.

Kitaya, Yoshiaki; Hirai, Hiroaki; Nobol Ikeda, MR..

2012-07-01

368

The effect of CO(2) enrichment on leaf photosynthetic rates and instantaneous water use efficiency of Andropogon gerardii in the tallgrass prairie.  

PubMed

Open-top chambers were used to study the effects of CO(2) enrichment on leaf-level photosynthetic rates of the C(4) grass Andropogon gerardii in the native tallgrass prairie ecosystem near Manhattan, Kansas. Measurements were made during a year with abundant rainfall (1993) and a year with below-normal rainfall (1994). Treatments included: No chamber, ambient CO(2) (A); chamber with ambient CO(2) (CA); and chamber with twice-ambient CO(2) (CE). Measurements of photosynthesis were made at 2-hour intervals, or at midday, on cloudless days throughout the growing season using an open-flow gas-exchange system. No significant differences in midday rates of photosynthesis or in daily carbon accumulation as a result of CO(2) enrichment were found in the year with abundant precipitation. In the dry year, midday rates of photosynthesis were significantly higher in the CE treatment than in the CA or A treatments throughout the season. Estimates of daily carbon accumulation also indicated that CO(2) enrichment allowed plants to maximize carbon acquisition on a diurnal basis. The increased carbon accumulation was accounted for by greater rates of photosynthesis in the CE plots during midday. During the wet year, CO(2) enrichment decreased stomatal conductance, which allowed plants to decrease transpiration while still photosynthesizing at rates similar to plants in ambient conditions. During the dry year, CO(2) enrichment allowed plants to maintain photosynthetic rates even though stomatal conductance and transpiration had been reduced in all treatments due to stress. Estimates of instantaneous water-use efficiency were reduced under CO(2) enrichment for both years. PMID:16228479

Adam, N R; Owensby, C E; Ham, J M

2000-01-01

369

Influence of irrigation and fertilization on transpiration and hydraulic properties of Populus deltoides.  

SciTech Connect

Summary Long-term hydraulic acclimation to resource availability was explored in 3-year-bld Populus deltoides Bartr. ex Marsh. clones by examining transpiration. leaf-specific hydraulic conductance (GL), canopy stomatal conductance (Gs) and leaf to sapwood area ratio (AL:Asi)n response to imgation (13 and 551 mm year in addition to ambient precipitation) and fertilization (0 and 120 kg N ha-' year-'). Sap flow was measured continuously over one growing season with thermal dissipation probes. Fertilization had a greater effect on growth and hydraulic properties than imgation, and fertilization effects were independent of irrigation treatment. Transpiration on a ground area basis (E) ranged between 0.3 and 1.8 mm day-', and increased 66% and 90% in response to imgation and fertilization, respectively. Increases in GL, Gs at a reference vapor pressure deficit of 1 kPa, and transpiration per unit leaf areain response to increases in resource availability were associated with reductions in AL:As and consequently a minimal change in the water potential gradient from soil to leaf. Imgation and fertilization increased leaf area index similarly, from an average 1.16 in control stands to 1.45, but sapwood area was increased from 4.0 to 6.3 m ha-' by irrigation and from 3.7 to 6.7 m2 ha-' by fertilization. The balance between leaf area and sapwood area was important in understanding long-term hydraulic acclimation to resource availability and mechanisms controlling maximum productivity in Populus deltoides.

Samuelson, Lisa, J.; Stokes, Thomas, A.; Coleman, Mark, D.

2007-02-01

370

The transpiration and the spectral response of non-irrigated Haloxylon ammodendron at canopy scale  

NASA Astrophysics Data System (ADS)

Transpiration, an essential component of surface evapotranspiration, is particularly important in the research of surface evapotranspiration in arid areas. The paper explores the spectral information of the arid vegetal evapotranspiration from a semi-empirical perspective by the measured data and the up-scaling method. The paper inverted the transpiration of Haloxylon ammodendronat at the canopy, pixel and regional scales in the southern edge of the Gurbantunggut desert in Xinjiang, China. The results are as follows: At the canopy scale, the optimal exponential model of the sap flow based on the hyperspectrum is Y = 3.65× SR(1580,1600) + 0.76, R2 = 0.72. At the pixel scale, there was a good linear relationship between the sap flow and the SR index, with a linear relationship of Y = 0.0787 X - 0.0724, R2 = 0.604. At the regional scale, based on the optimal exponential model and the EO-1 Hyperion remote sensing data, the transpiration of the study area was inverted. Comparing the results of the SEBAL and SEBS models, the errors of the simulation results were 12.66% and 11.68%. The paper made full use of the knowledge flow at different scales, bridging the scale difference in canopy and remote sensing images to avoid the information bottleneck in the up-scaling. However, there is much limit in the data acquirement, the endmembers determine, the temporal-spatial up-scaling, and the accuracy assessment to be improved in the future studies.

Cao, Xiao-ming; Wang, Juan-le; Gao, Zhiqiang; Chen, Mao-si

2012-10-01

371

Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant  

PubMed Central

Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August–September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions.

Harada, Kouji H.; Niisoe, Tamon; Imanaka, Mie; Takahashi, Tomoyuki; Amako, Katsumi; Fujii, Yukiko; Kanameishi, Masatoshi; Ohse, Kenji; Nakai, Yasumichi; Nishikawa, Tamami; Saito, Yuuichi; Sakamoto, Hiroko; Ueyama, Keiko; Hisaki, Kumiko; Ohara, Eiji; Inoue, Tokiko; Yamamoto, Kanako; Matsuoka, Yukiyo; Ohata, Hitomi; Toshima, Kazue; Okada, Ayumi; Sato, Hitomi; Kuwamori, Toyomi; Tani, Hiroko; Suzuki, Reiko; Kashikura, Mai; Nezu, Michiko; Miyachi, Yoko; Arai, Fusako; Kuwamori, Masanori; Harada, Sumiko; Ohmori, Akira; Ishikawa, Hirohiko; Koizumi, Akio

2014-01-01

372

Etude des relations entre photosynthese respiration, transpiration et nutrition minerale chez le ble  

NASA Astrophysics Data System (ADS)

La croissance du Blé Triticum aestivum a été étudiée en environnement contrôlé et fermé pendant une période de 70 jours. Les échanges gazeux (Photosynthèse, Respiration) hydriques (Transpiration) et la consommation en éléments minéraux (Azote, Phosphore, Potassium) ont été mesurés en continu. On présentera les relations dynamiques observées entre les différentes fonctions physiologiques, d'une part sous l'influence de la croissance et d'autre part en réponse à des modifications de l'environnement. L'influence de la teneur en CO2 pendant la croissance (teneur normale ou doublée) sera mise en évidence.

André, M.; Ducloux, H.; Richaud, C.; Massimino, D.; Daguenet, A.; Massimino, J.; Gerbaud, A.

373

Monte Carlo analysis of lobular gas-surface scattering in tubes applied to thermal transpiration  

NASA Technical Reports Server (NTRS)

A model of rarefied gas flow in tubes was developed which combines a lobular distribution with diffuse reflection at the wall. The model with Monte Carlo techniques was used to explain previously observed deviations in the free molecular thermal transpiration ratio which suggest molecules can have a greater tube transmission probability in a hot-to-cold direction than in a cold-to-hot direction. The model yields correct magnitudes of transmission probability ratios for helium in Pyrex tubing (1.09 to 1.14), and some effects of wall-temperature distribution, tube surface roughness, tube dimensions, gas temperature, and gas molecular mass.

Smith, J. D.; Raquet, C. A.

1972-01-01

374

Options for transpiration water removal in a crop growth system under zero gravity conditions  

NASA Technical Reports Server (NTRS)

The operation of a microgravity crop-growth system is a critical feature of NASA's Closed Ecological Life Support System (CELSS) development program. Transpiration-evolved water must be removed from the air that is recirculated in such a system, perhaps supplying potable water in the process. The present consideration of candidate systems for CELSS water removal gives attention to energy considerations and to a mechanical, inertial-operation water-separation system that was chosen due to the depth of current understanding of its operation.

Blackwell, C. C.; Kliss, M.; Yendler, B.; Borchers, B.; Yendler, Boris S.; Nguyen, Thoi K.; Waleh, Ahmad

1991-01-01

375

Solar Ultraviolet-B Radiation Affects Seedling Emergence, DNA Integrity, Plant Morphology, Growth Rate, and Attractiveness to Herbivore Insects in Datura ferox.  

PubMed Central

To study functional relationships between the effects of solar ultraviolet-B radiation (UV-B) on different aspects of the physiology of a wild plant, we carried out exclusion experiments in the field with the summer annual Datura ferox L. Solar UV-B incident over Buenos Aires reduced daytime seedling emergence, inhibited stem elongation and leaf expansion, and tended to reduce biomass accumulation during early growth. However, UV-B had no effect on calculated net assimilation rate. Using a monoclonal antibody specific to the cyclobutane-pyrimidine dimer (CPD), we found that plants receiving full sunlight had more CPDs per unit of DNA than plants shielded from solar UV-B, but the positive correlation between UV-B and CPD burden tended to level off at high (near solar) UV-B levels. At our field site, Datura plants were consumed by leaf beetles (Coleoptera), and the proportion of plants attacked by insects declined with the amount of UV-B received during growth. Field experiments showed that plant exposure to solar UV-B reduced the likelihood of leaf beetle attack by one-half. Our results highlight the complexities associated with scaling plant responses to solar UV-B, because they show: (a) a lack of correspondence between UV-B effects on net assimilation rate and whole-plant growth rate, (b) nonlinear UV-B dose-response curves, and (c) UV-B effects of plant attractiveness to natural herbivores.

Ballare, C. L.; Scopel, A. L.; Stapleton, A. E.; Yanovsky, M. J.

1996-01-01

376

Middle to late Miocene Plant Respiration Rates from the Southern Altiplano Indicate Increasing Aridity during Surface Uplift  

NASA Astrophysics Data System (ADS)

The interactions between climate and tectonics have likely played an important role in shaping the central Andes, where extreme climate gradients exist today (e.g., Masek et al., 1994; Horton et al., 1999; Montgomery et al., 2001). However, the feedback between these processes is still not fully understood (e.g., Molnar and England, 1990), and some have argued that climate change has resulted in a false signal of elevation change in the region (Ehlers and Poulsen, 2009; Poulsen et. al., 2010). This study attempts to resolve this debate by examining the history of aridification of the southern Altiplano by using plant respiration rates as a proxy for aridity, and comparing this to the studies of surface uplift. Assuming all other factors are constant, plant respiration rates should decrease with increasing aridity (Cerling and Quade, 1993), and therefore this calculation provides an estimate of the relative amount of precipitation. Changes in the aridity of discrete portions of the Andean plateau help determine the local climate response to Andean surface uplift and allow us to tease out the effects of surface uplift versus global climate change on this region. Paleoelevation studies have indicated rapid surface uplift of ~1.6 km in the southern Altiplano from ~16 to 13 Ma (Smith et al., 2009) followed by ~2.5 km in the north between 10 and 6 Ma (Garzione et al., 2006; 2008; Ghosh et al., 2006). These different surface uplift histories should have coincided with distinct climate change events in the northern and southern Altiplano due to the development of a rain shadow associated with the rising Eastern Cordillera and Altiplano basin (currently between ~3.6 km and 4 km). This study calculates plant respiration rates in paleosols dating from ~16 to 8 Ma (i.e., the period of inferred surface uplift) in the southern Altiplano/Eastern Cordillera using the soil carbon isotope model of Quade et al. (2007), which is based on the relationship between the carbon isotopic values of soil CO2 (estimated from d13C of paleosol carbonates) and plant-respired CO2 (estimated from d13C of fossil teeth). Calculations show a decrease in plant respiration rates throughout the middle to late Miocene, which indicates increasing aridity in the southern Altiplano that is synchronous with surface uplift. This lends support to the argument that the observations of Miocene changes in the central Andes, such as surface temperature changes in the northern and southern Altiplano (Ghosh et al., 2006; Smith et al., 2009), are caused by surface uplift rather than global climate change due to the distinct timing of changes within each region. This paleoclimate evidence also supports the rapid uplift hypothesis by documenting the aridification that is expected to accompany the surface uplift in each area.

Smith, J. J.; Garzione, C. N.; Auerbach, D. J.; Macfadden, B.; Croft, D.

2011-12-01

377

A Tolerant Behavior in Salt-Sensitive Tomato Plants can be Mimicked by Chemical Stimuli  

PubMed Central

Lycopersicon esculentum plants exhibit increased salt stress tolerance following treatment with adipic acid monoethylester and 1,3-diaminepropane (DAAME), known as an inducer of resistance against biotic stress in tomato and pepper. For an efficient water and nutrient uptake, plants should adapt their water potential to compensate a decrease in water soil potential produced by salt stress. DAAME-treated plants showed a faster and stronger water potential reduction and an enhanced proline accumulation. Salinity-induced oxidative stress was also ameliorated by DAAME treatments. Oxidative membrane damage and ethylene emission were both reduced in DAAME-treated plants. This effect is probably a consequence of an increase of both non-enzymatic antioxidant activity as well as peroxidase activity. DAAME-mediated tolerance resulted in an unaltered photosynthetic rate and a stimulation of the decrease in transpiration under stress conditions without a cost in growth due to salt stress. The reduction in transpiration rate was concomitant with a reduction in phytotoxic Na+ and Cl? accumulation under saline stress. Interestingly, the ABA deficient tomato mutant sitiens was insensitive to DAAME-induced tolerance following NaCl stress exposure. Additionally, DAAME treatments increased the ABA content of leaves, therefore, an intact ABA signalling pathway seems to be important to express DAAME-induced salt tolerance. Here, we show a possibility of enhance tomato stress tolerance by chemical induction of the major plant defences against salt stress. DAAME-induced tolerance against salt stress could be complementary to or share elements with induced resistance against biotic stress. This might be the reason for the observed wide spectrum of effectiveness of this compound.

Flors, Victor; Paradis, Mercedes; Garcia-Andrade, Javier; Cerezo, Miguel; Gonzalez-Bosch, Carmen

2007-01-01

378

Cryo-Scanning Electron Microscopy Observations of Vessel Content during Transpiration in Walnut Petioles. Facts or Artifacts?  

PubMed Central

The current controversy about the “cohesion-tension” of water ascent in plants arises from the recent cryo-scanning electron microscopy (cryo-SEM) observations of xylem vessels content by Canny and coworkers (1995). On the basis of these observations it has been claimed that vessels were emptying and refilling during active transpiration in direct contradiction to the previous theory. In this study we compared the cryo-SEM data with the standard hydraulic approach on walnut (Juglans regia) petioles. The results of the two techniques were in clear conflict and could not both be right. Cryo-SEM observations of walnut petioles frozen intact on the tree in a bath of liquid nitrogen (LN2) suggested that vessel cavitation was occurring and reversing itself on a diurnal basis. Up to 30% of the vessels were embolized at midday. In contrast, the percentage of loss of hydraulic conductance (PLC) of excised petiole segments remained close to 0% throughout the day. To find out which technique was erroneous we first analyzed the possibility that PLC values were rapidly returned to zero when the xylem pressures were released. We used the centrifugal force to measure the xylem conductance of petiole segments exposed to very negative pressures and es