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Sample records for plant transpiration rate

  1. Zinc and copper uptake by plants under two transpiration rates. Part I. Wheat (Triticum aestivum L.).

    PubMed

    Tani, F H; Barrington, S

    2005-12-01

    To evaluate the environmental risk of irrigating crops with treated wastewater, an experiment was conducted using two growth chambers, each offering a different vapour pressure deficit (VPD) for high and low transpiration rates (TR), respectively. One of the two sets of 24 pots planted with 6 week old wheat (Triticum aestivum L.), was placed in each growth chamber, and irrigated in triplicates for 20 days with 8 Zn and Cu solutions (0 and 25 mg Zn/L combined with 0, 5, 15 and 30 mg Cu/L). Water losses from planted and non-planted pots served to measure evapo-transpiration and evaporation, respectively. Pots were monitored for Cu and Zn uptake by collecting three plants (shoot and grain)/pots after 0, 10 and 20 days, and roots in each pot after 20 days, and analyzing these plant parts for dry mass, and Cu and Zn levels. Transpiration rate was not affected by any Cu/Zn treatment, but Cu and Zn uptake increase with the time, irrigation solution level and higher TR, with the roots retaining most Cu and Zn, compared to the shoot followed by the grain. For the shoot and grain, Cu had a significant synergetic effect on Zn uptake, when Zn had slight but insignificant antagonistic effects on Cu uptake. For the roots, Cu and Zn had significant synergetic effect on each other. Regression equations obtained from the data indicate that Cu and Zn levels normally found in treated wastewater (0.08 mg/L) are 300 times lower than those used for the most concentrated experimental solutions (30 and 25 mg/L, respectively) and may, on a long term basis, be beneficial rather than toxic to wheat plants and do not acidify soil pH. PMID:16043273

  2. Development of synchronized, autonomous, and self-regulated oscillations in transpiration rate of a whole tomato plant under water stress

    PubMed Central

    Wallach, Rony; Da-Costa, Noam; Raviv, Michael; Moshelion, Menachem

    2010-01-01

    Plants respond to many environmental changes by rapidly adjusting their hydraulic conductivity and transpiration rate, thereby optimizing water-use efficiency and preventing damage due to low water potential. A multiple-load-cell apparatus, time-series analysis of the measured data, and residual low-pass filtering methods were used to monitor continuously and analyse transpiration of potted tomato plants (Solanum lycopersicum cv. Ailsa Craig) grown in a temperature-controlled greenhouse during well-irrigated and drought periods. A time derivative of the filtered residual time series yielded oscillatory behaviour of the whole plant's transpiration (WPT) rate. A subsequent cross-correlation analysis between the WPT oscillatory pattern and wet-wick evaporation rates (vertical cotton fabric, 0.14 m2 partly submerged in water in a container placed on an adjacent load cell) revealed that autonomous oscillations in WPT rate develop under a continuous increase in water stress, whereas these oscillations correspond with the fluctuations in evaporation rate when water is fully available. The relative amplitude of these autonomous oscillations increased with water stress as transpiration rate decreased. These results support the recent finding that an increase in xylem tension triggers hydraulic signals that spread instantaneously via the plant vascular system and control leaf conductance. The regulatory role of synchronized oscillations in WPT rate in eliminating critical xylem tension points and preventing embolism is discussed. PMID:20558570

  3. Silver and zinc inhibitors influence transpiration rate and aquaporin transcript levels in intact soybean plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Some soybean (Glycine max (L.) Merr.) have been identified that expressed limited transpiration rate (TR) above a threshold vapor pressure deficit (VPD). Restriction of TR at high VPD conditions is considered a water conservation trait that allows water to be retained in the soil to benefit of crop...

  4. Plant transpiration distillation of water

    SciTech Connect

    Virostko, M.K.; Spielberg, J.I.

    1986-01-01

    A project using solar energy and the transpiration of plants for the distillation of water is described. Along with determining which of three plants thrived best growing in a still, the experiment also revealed that the still functioned nearly as well in inclement weather as in fair weather.

  5. Hydraulic Limits on Maximum Plant Transpiration

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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

  6. Zinc uptake by young wheat plants under two transpiration regimes

    SciTech Connect

    Grifferty, A.; Barrington, S.

    2000-04-01

    Treated wastewater for crop irrigation is an alternative for countries with a shortage of fresh water. Such practice requires strict wastewater application criteria and a better understanding of the effects of transpiration rate on plant heavy metal uptake. The experiment measured Zn uptake by young wheat plants (Triticum aestvum L.) grown in triplicated experimental pots and held in two growth chambers with constant environmental conditions (relative humidity, light and temperature) but with a different air water vapor pressure deficit to produce two different transpiration rates. After 5 wk of growth in a greenhouse, the plants were transferred to the controlled chambers and irrigated using a fertilized solution with five different levels of Zn: 0, 2, 10, 25, and 50 mg/L. These Zn levels were low enough to have no significant effect on plant growth and transpiration rate. The wheat plants started to produce their grain at 6 wk. Plants were collected at 0, 3, and 10 d of incubation in the controlled chambers and analyzed for dry matter and total Zn content. The pots were weighed daily to measure their transpiration rates. On Day 10, the remaining plants were collected and their roots, shoots, and grain were separated, weighed, dried, and analyzed for total Zn. Time and plant transpiration rate were found to affect significantly plant Zn uptake. The higher transpiration rate enhanced plant Zn uptake. The roots had the highest Zn uptake followed by the shoots and then the grain.

  7. Drought, Abscisic Acid and Transpiration Rate Effects on the Regulation of PIP Aquaporin Gene Expression and Abundance in Phaseolus vulgaris Plants

    PubMed Central

    AROCA, RICARDO; FERRANTE, ANTONIO; VERNIERI, PAOLO; CHRISPEELS, MAARTEN J.

    2006-01-01

    • Background and Aims Drought causes a decline of root hydraulic conductance, which aside from embolisms, is governed ultimately by aquaporins. Multiple factors probably regulate aquaporin expression, abundance and activity in leaf and root tissues during drought; among these are the leaf transpiration rate, leaf water status, abscisic acid (ABA) and soil water content. Here a study is made of how these factors could influence the response of aquaporin to drought. • Methods Three plasma membrane intrinsic proteins (PIPs) or aquaporins were cloned from Phaseolus vulgaris plants and their expression was analysed after 4 d of water deprivation and also 1 d after re-watering. The effects of ABA and of methotrexate (MTX), an inhibitor of stomatal opening, on gene expression and protein abundance were also analysed. Protein abundance was examined using antibodies against PIP1 and PIP2 aquaporins. At the same time, root hydraulic conductance (L), transpiration rate, leaf water status and ABA tissue concentration were measured. • Key Results None of the treatments (drought, ABA or MTX) changed the leaf water status or tissue ABA concentration. The three treatments caused a decline in the transpiration rate and raised PVPIP2;1 gene expression and PIP1 protein abundance in the leaves. In the roots, only the drought treatment raised the expression of the three PIP genes examined, while at the same time diminishing PIP2 protein abundance and L. On the other hand, ABA raised both root PIP1 protein abundance and L. • Conclusions The rise of PvPIP2;1 gene expression and PIP1 protein abundance in the leaves of P. vulgaris plants subjected to drought was correlated with a decline in the transpiration rate. At the same time, the increase in the expression of the three PIP genes examined caused by drought and the decline of PIP2 protein abundance in the root tissues were not correlated with any of the parameters measured. PMID:17028296

  8. Quality assessment of plant transpiration water

    NASA Technical Reports Server (NTRS)

    Macler, Bruce A.; Janik, Daniel S.; Benson, Brian L.

    1990-01-01

    It has been proposed to use plants as elements of biologically-based life support systems for long-term space missions. Three roles have been brought forth for plants in this application: recycling of water, regeneration of air and production of food. This report discusses recycling of water and presents data from investigations of plant transpiration water quality. Aqueous nutrient solution was applied to several plant species and transpired water collected. The findings indicated that this water typically contained 0.3-6 ppm of total organic carbon, which meets hygiene water standards for NASA's space applications. It suggests that this method could be developed to achieve potable water standards.

  9. Characterizing photosynthesis and transpiration of plant communities in controlled environments

    NASA Technical Reports Server (NTRS)

    Monje, O.; Bugbee, B.

    1996-01-01

    CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

  10. Measuring Transpiration to Regulate Winter Irrigation Rates

    SciTech Connect

    Samuelson, Lisa

    2006-11-08

    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.

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

    ERIC Educational Resources Information Center

    Seligmann, Peter F.; Thompson, Steven R.

    1989-01-01

    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)

  12. Transpiration rate measurement using miniature temperature/humidity sensors.

    PubMed

    Sasaki, Satoshi; Amano, Tatsuya

    2010-01-01

    A novel method for the evaluating the transpiration rate (TR) has been proposed. Miniature temperature/humidity loggers were attached onto the leaf surface of a mangrove plant, Bruguiera gymnorrhiza, via a spacer. TR values were calculated using the mass-balance equation; the results showed good agreement with those measured using a conventional porometer when the plant root was surrounded by water. In a saline environment, on the other hand, the correlation became poor. The method was shown to require not only minimal invasion, but also a very short time for attaching leaves. PMID:20631447

  13. Acclimation of whole-plant Acacia farnesiana transpiration to carbon dioxide concentration.

    PubMed

    Dugas, W A; Polley, H W; Mayeux, H S; Johnson, H B

    2001-07-01

    Transpiration per unit leaf area of Acacia farnesiana (L.) Willd. plants grown at a CO2 concentration ([CO2]) of 385 micromol x mol(-1) was about twice that of plants grown at 980 micromol x mol(-1). However, whes plants grown for more than a year at 980 micromol x mol(-1) were exposed to 380 micromol x mol(-1) for 9 days, they transpired at half the rate of those that had been grown at 380 micromol x mol(-1)1. Similarly, plants grown at 380 micromol x mol(-1), when exposed to 980 micromol x mol(-1), transpired at twice the rate of those grown at 980 micromol x mol(-1). Thus, the effects of elevated [CO2] on whole-plant transpiration, like those on photosynthesis, respiration and stomatal conductance, cannot reliably be extrapolated from measurements made during short-term exposure to elevated [CO2]. PMID:11470664

  14. Root water compensation sustains transpiration rates in an Australian woodland

    NASA Astrophysics Data System (ADS)

    Verma, Parikshit; Loheide, Steven P.; Eamus, Derek; Daly, Edoardo

    2014-12-01

    We apply a model of root-water uptake to a woodland in Australia to examine the regulation of transpiration by root water compensation (i.e., the ability of roots to regulate root water uptake from different parts of the soil profile depending on local moisture availability). We model soil water movement using the Richards equation and water flow in the xylem with Darcy's equation. These two equations are coupled by a term that governs the exchange of water between soil and root xylem as a function of the difference in water potential between the two. The model is able to reproduce measured diurnal patterns of sap flux and results in leaf water potentials that are consistent with field observations. The model shows that root water compensation is a key process to allow for sustained rates of transpiration across several months. Scenarios with different root depths showed the importance of having a root system deeper than about 2 m to achieve the measured transpiration rates without reducing the leaf water potential to levels inconsistent with field measurements. The model suggests that the presence of more than 5 % of the root system below 0.6 m allows trees to maintain sustained transpiration rates keeping leaf water potential levels within the range observed in the field. According to the model, a large contribution to transpiration in dry periods was provided by the roots below 0.3 m, even though the percentage of roots at these depths was less than 40 % in all scenarios.

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

    PubMed

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

    2010-05-01

    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

  16. Barley yellow dwarf virus effects on cereal plant growth and transpiration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little is known about how changes in root system biomass caused by barley yellow dwarf virus (BYDV) infection impact water relations in cereal plants. Objectives of these greenhouse studies were to elucidate virus infection effects on plant growth and apparent transpiration rate in oats (Avena sati...

  17. Global separation of plant transpiration from groundwater and streamflow.

    PubMed

    Evaristo, Jaivime; Jasechko, Scott; McDonnell, Jeffrey J

    2015-09-01

    Current land surface models assume that groundwater, streamflow and plant transpiration are all sourced and mediated by the same well mixed water reservoir--the soil. However, recent work in Oregon and Mexico has shown evidence of ecohydrological separation, whereby different subsurface compartmentalized pools of water supply either plant transpiration fluxes or the combined fluxes of groundwater and streamflow. These findings have not yet been widely tested. Here we use hydrogen and oxygen isotopic data ((2)H/(1)H (δ(2)H) and (18)O/(16)O (δ(18)O)) from 47 globally distributed sites to show that ecohydrological separation is widespread across different biomes. Precipitation, stream water and groundwater from each site plot approximately along the δ(2)H/δ(18)O slope of local precipitation inputs. But soil and plant xylem waters extracted from the 47 sites all plot below the local stream water and groundwater on the meteoric water line, suggesting that plants use soil water that does not itself contribute to groundwater recharge or streamflow. Our results further show that, at 80% of the sites, the precipitation that supplies groundwater recharge and streamflow is different from the water that supplies parts of soil water recharge and plant transpiration. The ubiquity of subsurface water compartmentalization found here, and the segregation of storm types relative to hydrological and ecological fluxes, may be used to improve numerical simulations of runoff generation, stream water transit time and evaporation-transpiration partitioning. Future land surface model parameterizations should be closely examined for how vegetation, groundwater recharge and streamflow are assumed to be coupled. PMID:26333467

  18. Global separation of plant transpiration from groundwater and streamflow

    NASA Astrophysics Data System (ADS)

    Evaristo, Jaivime; Jasechko, Scott; McDonnell, Jeffrey J.

    2015-09-01

    Current land surface models assume that groundwater, streamflow and plant transpiration are all sourced and mediated by the same well mixed water reservoir--the soil. However, recent work in Oregon and Mexico has shown evidence of ecohydrological separation, whereby different subsurface compartmentalized pools of water supply either plant transpiration fluxes or the combined fluxes of groundwater and streamflow. These findings have not yet been widely tested. Here we use hydrogen and oxygen isotopic data (2H/1H (δ2H) and 18O/16O (δ18O)) from 47 globally distributed sites to show that ecohydrological separation is widespread across different biomes. Precipitation, stream water and groundwater from each site plot approximately along the δ2H/δ18O slope of local precipitation inputs. But soil and plant xylem waters extracted from the 47 sites all plot below the local stream water and groundwater on the meteoric water line, suggesting that plants use soil water that does not itself contribute to groundwater recharge or streamflow. Our results further show that, at 80% of the sites, the precipitation that supplies groundwater recharge and streamflow is different from the water that supplies parts of soil water recharge and plant transpiration. The ubiquity of subsurface water compartmentalization found here, and the segregation of storm types relative to hydrological and ecological fluxes, may be used to improve numerical simulations of runoff generation, stream water transit time and evaporation-transpiration partitioning. Future land surface model parameterizations should be closely examined for how vegetation, groundwater recharge and streamflow are assumed to be coupled.

  19. Hydraulic resistances and root geometry parameters in plant transpiration analysis

    NASA Astrophysics Data System (ADS)

    Vogel, Tomas; Votrubova, Jana; Dusek, Jaromir; Dohnal, Michal

    2016-04-01

    Three approximate mesoscopic solutions of soil water flow towards roots: (1) finite difference approximation, (2) steady-state solution, and (3) steady-rate solution, were examined from the point of view of their ability to predict the pressure head variations in the vicinity of roots. The individual solutions were then alternatively used to determine the macroscopic soil hydraulic resistance between bulk soil and root surface. In the next step, macroscopic simulations of coupled soil water flow and root water uptake at a forest site under humid temperate climate were performed. The predicted soil water pressure heads and actual transpiration rates were compared with observed data. The simulation results illustrate uncertainties associated with the estimation of root geometric and hydraulic properties. Regarding the prediction of actual transpiration, the correct characterization of active root system geometry and its hydraulic properties seems far more important than the choice of a particular macroscopic soil hydraulic resistance formula.

  20. Development of the deuterium tracing method for the estimation of transpiration rates and transpiration parameters of trees

    SciTech Connect

    Calder, I.R.

    1992-12-31

    Recent developments relating to the theory and practice of the deuterium tracing method are reviewed. Theoretical developments have shown that the method is applicable to the fluctuating flow regime which occurs in trees and that the method provides an estimate of the weighted mean flow over the time period that the tracer is present at the sampling point. A practical development of the method for estimating transpiration rates and transpiration parameters which uses time averaged sampling is described and it is shown that with this method only one deuterium tracer concentration analysis is required per tree compared with 90 using an earlier method. The calculation of surface resistance through solution of the convolution integral of the transpiration rate and the tracer concentration-time curve is also described and the sensitivity of the surface resistance estimate to the flow parameters is investigated using as an example observations made on a three year old plantation of Eucalyptus tereticornis growing in Karnataka, southern India.

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

    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.

  2. Hydrogen isotope composition of leaf wax n-alkanes in Arabidopsis lines with different transpiration rates

    NASA Astrophysics Data System (ADS)

    Pedentchouk, N.; Lawson, T.; Eley, Y.; McAusland, L.

    2012-04-01

    Stable isotopic compositions of oxygen and hydrogen are used widely to investigate modern and ancient water cycles. The D/H composition of organic compounds derived from terrestrial plants has recently attracted significant attention as a proxy for palaeohydrology. However, the role of various plant physiological and biochemical factors in controlling the D/H signature of leaf wax lipids in extant plants remains unclear. The focus of this study is to investigate the effect of plant transpiration on the D/H composition of n-alkanes in terrestrial plants. This experiment includes 4 varieties of Arabidopsis thaliana that differ with respect to stomatal density and stomatal geometry. All 4 varieties were grown indoors under identical temperature, relative humidity, light and watering regimes and then sampled for leaf wax and leaf water stable isotopic measurements. During growth, stomatal conductance to carbon dioxide and water vapour were also determined. We found that the plants varied significantly in terms of their transpiration rates. Transpiration rates were significantly higher in Arabidopsis ost1 and ost1-1 varieties (2.4 and 3.2 mmol m-2 s-1, respectively) than in Arabidopsis RbohD and Col-0 (1.5 and 1.4). However, hydrogen isotope measurements of n-alkanes extracted from leaf waxes revealed a very different pattern. Varieties ost1, ost1-1, and RbohD have very similar deltaD values of n-C29 alkane (-125, -128, and -127 per mil), whereas the deltaD value of Col-0 is more negative (-137 per mil). The initial results of this work suggest that plant transpiration is decoupled from the D/H composition of n-alkanes. In other words, physical processes that affect water vapour movement between the plant and its environment apparently cannot account for the stable hydrogen isotope composition of organic compounds that comprise leaf waxes. Additional, perhaps biochemical, processes that affect hydrogen isotope fractionation during photosynthesis might need to be invoked

  3. Investigation of transpiration and/or accumulation of volatile organic compounds (VOCs) by plants

    SciTech Connect

    Goodrich, R.L.; Carlsen, T.M.

    1994-12-31

    The authors are in the planning stages of an investigation to explore plant transpiration and/or accumulation of VOCs (primarily Trichloroethylene [TCE]) by native vegetation. Such processes may naturally remediate these compounds in shallow ground water. To adequately quantify the amount of TCE in ground water prior to vegetation uptake, the authors will first install shallow piezometers adjacent to existing vegetation. Vegetation sampling will be synchronized with the ground water sampling to establish baseline conditions. They will conduct a literature search to identify potential structures with high lipid content in the plant species of interest (Populus fremontii, Typha latifolia and Salix). To investigate VOC distribution in the plant, individual morphological segments of the plant will be analyzed. The vegetation will be dissected into distinct segments, such as the vegetative (stem and leaves) and reproductive structures, to determine the possible accumulation of TCE at various points within the plant. They have completed preliminary development of analytical methods that they will use to analyze the samples. In the field, plastic (Tedlar) bags will be tightly secured onto the vegetation and a direct head-space analysis will be conducted on the bags, thus providing information on the rate of transpiration compared to the actual accumulation of VOCs within the plant. At a minimum, they expect to document VOC losses from the ground water via plant transpiration.

  4. Gravimetric phenotyping of whole plant transpiration responses to atmospheric vapour pressure deficit identifies genotypic variation in water use efficiency.

    PubMed

    Ryan, Annette C; Dodd, Ian C; Rothwell, Shane A; Jones, Ros; Tardieu, Francois; Draye, Xavier; Davies, William J

    2016-10-01

    There is increasing interest in rapidly identifying genotypes with improved water use efficiency, exemplified by the development of whole plant phenotyping platforms that automatically measure plant growth and water use. Transpirational responses to atmospheric vapour pressure deficit (VPD) and whole plant water use efficiency (WUE, defined as the accumulation of above ground biomass per unit of water used) were measured in 100 maize (Zea mays L.) genotypes. Using a glasshouse based phenotyping platform with naturally varying VPD (1.5-3.8kPa), a 2-fold variation in WUE was identified in well-watered plants. Regression analysis of transpiration versus VPD under these conditions, and subsequent whole plant gas exchange at imposed VPDs (0.8-3.4kPa) showed identical responses in specific genotypes. Genotype response of transpiration versus VPD fell into two categories: 1) a linear increase in transpiration rate with VPD with low (high WUE) or high (low WUE) transpiration rate at all VPDs, 2) a non-linear response with a pronounced change point at low VPD (high WUE) or high VPD (low WUE). In the latter group, high WUE genotypes required a significantly lower VPD before transpiration was restricted, and had a significantly lower rate of transpiration in response to VPD after this point, when compared to low WUE genotypes. Change point values were significantly positively correlated with stomatal sensitivity to VPD. A change point in stomatal response to VPD may explain why some genotypes show contradictory WUE rankings according to whether they are measured under glasshouse or field conditions. Furthermore, this novel use of a high throughput phenotyping platform successfully reproduced the gas exchange responses of individuals measured in whole plant chambers, accelerating the identification of plants with high WUE. PMID:27593468

  5. A Transpiration Experiment Requiring Critical Thinking Skills.

    ERIC Educational Resources Information Center

    Ford, Rosemary H.

    1998-01-01

    Details laboratory procedures that enable students to understand the concept of how differences in water potential drive the movement of water within a plant in response to transpiration. Students compare transpiration rates for upper and lower surfaces of leaves. (DDR)

  6. Hydraulic limits on maximum plant transpiration and the emergence of the safety-efficiency trade-off.

    PubMed

    Manzoni, Stefano; Vico, Giulia; Katul, Gabriel; Palmroth, Sari; Jackson, Robert B; Porporato, Amilcare

    2013-04-01

    Soil and plant hydraulics constrain ecosystem productivity by setting physical limits to water transport and hence carbon uptake by leaves. While more negative xylem water potentials provide a larger driving force for water transport, they also cause cavitation that limits hydraulic conductivity. An optimum balance between driving force and cavitation occurs at intermediate water potentials, thus defining the maximum transpiration rate the xylem can sustain (denoted as E(max)). The presence of this maximum raises the question as to whether plants regulate transpiration through stomata to function near E(max). To address this question, we calculated E(max) across plant functional types and climates using a hydraulic model and a global database of plant hydraulic traits. The predicted E(max) compared well with measured peak transpiration across plant sizes and growth conditions (R = 0.86, P < 0.001) and was relatively conserved among plant types (for a given plant size), while increasing across climates following the atmospheric evaporative demand. The fact that E(max) was roughly conserved across plant types and scales with the product of xylem saturated conductivity and water potential at 50% cavitation was used here to explain the safety-efficiency trade-off in plant xylem. Stomatal conductance allows maximum transpiration rates despite partial cavitation in the xylem thereby suggesting coordination between stomatal regulation and xylem hydraulic characteristics. PMID:23356378

  7. Plant transpiration and groundwater dynamics in water-limited climates: Impacts of hydraulic redistribution

    NASA Astrophysics Data System (ADS)

    Luo, Xiangyu; Liang, Xu; Lin, Jeen-Shang

    2016-06-01

    The role of groundwater in sustaining plant transpiration constitutes an important but not well-understood aspect of the interactions between groundwater, vegetation, the land surface, and the atmosphere. The effect of the hydraulic redistribution (HR) process by plant roots on the interplay between plant transpiration and groundwater dynamics under water-limited climates is investigated by using the Variable Infiltration Capacity Plus (VIC+) land surface model. Numerical experiments, with or without explicitly considering HR, are conducted on soil columns over a range of groundwater table depths (GWTDs) under different vegetative land covers, soil types, and precipitation conditions. When HR is not included, this study obtains transpiration-GWTD relationships consistent with those from watershed studies that do not include HR. When HR is included, the transpiration-GWTD relationships are modified. The modification introduced by HR is manifested in the soil moisture of the root zone. The mechanism of HR is explained by detailing the roles of the hydraulically redistributed water, the upward diffusion of soil water, and the daytime root uptake. We have found that HR is particularly important in water-limited climates under which plants have high transpiration demand. At the beginning stage of a dry period, HR modulates the severe impacts that climate has on plant transpiration. Only after a prolonged dry period, impacts of HR are lessened when the groundwater table drops below the depth of water uptake by roots and are diminished when plant transpiration is decoupled from groundwater dynamics.

  8. Photosynthesis, Transpiration, Leaf Temperature, and Stomatal Activity of Cotton Plants under Varying Water Potentials

    PubMed Central

    Pallas, J. E.; Michel, B. E.; Harris, D. G.

    1967-01-01

    Cotton plants, Gossypium hirsutum L. were grown in a growth room under incident radiation levels of 65, 35, and 17 Langleys per hour to determine the effects of vapor pressure deficits (VPD's) of 2, 9, and 17 mm Hg at high soil water potential, and the effects of decreasing soil water potential and reirrigation on transpiration, leaf temperature, stomatal activity, photosynthesis, and respiration at a VPD of 9 mm Hg. Transpiration was positively correlated with radiation level, air VPD and soil water potential. Reirrigation following stress led to slow recovery, which may be related to root damage occurring during stress. Leaf water potential decreased with, but not as fast as, soil water potential. Leaf temperature was usually positively correlated with light intensity and negatively correlated with transpiration, air VPD, and soil water. At high soil water, leaf temperatures ranged from a fraction of 1 to a few degrees above ambient, except at medium and low light and a VPD of 19 mm Hg when they were slightly below ambient, probably because of increased transpirational cooling. During low soil water leaf temperatures as high as 3.4° above ambient were recorded. Reirrigation reduced leaf temperature before appreciably increasing transpiration. The upper leaf surface tended to be warmer than the lower at the beginning of the day and when soil water was adequate; otherwise there was little difference or the lower surface was warmer. This pattern seemed to reflect transpiration cooling and leaf position effects. Although stomata were more numerous in the lower than the upper epidermis, most of the time a greater percentage of the upper were open. With sufficient soil water present, stomata opened with light and closed with darkness. Fewer stomata opened under low than high light intensity and under even moderate, as compared with high soil water. It required several days following reirrigation for stomata to regain original activity levels. Apparent photosynthesis

  9. Assessment of actual transpiration rate in olive tree field combining sap-flow, leaf area index and scintillometer measurements

    NASA Astrophysics Data System (ADS)

    Agnese, C.; Cammalleri, C.; Ciraolo, G.; Minacapilli, M.; Provenzano, G.; Rallo, G.; de Bruin, H. A. R.

    2009-09-01

    Models to estimate the actual evapotranspiration (ET) in sparse vegetation area can be fundamental for agricultural water managements, especially when water availability is a limiting factor. Models validation must be carried out by considering in situ measurements referred to the field scale, which is the relevant scale of the modelled variables. Moreover, a particular relevance assumes to consider separately the components of plant transpiration (T) and soil evaporation (E), because only the first is actually related to the crop stress conditions. Objective of the paper was to assess a procedure aimed to estimate olive trees actual transpiration by combining sap flow measurements with the scintillometer technique at field scale. The study area, located in Western Sicily (Italy), is mainly cultivated with olive crop and is characterized by typical Mediterranean semi-arid climate. Measurements of sap flow and crop actual evapotranspiration rate were carried out during 2008 irrigation season. Crop transpiration fluxes, measured on some plants by means of sap flow sensors, were upscaled considering the leaf area index (LAI). The comparison between evapotranspiration values, derived by displaced-beam small-aperture scintillometer (DBSAS-SLS20, Scintec AG), with the transpiration fluxes obtained by the sap flow sensors, also allowed to evaluate the contribute of soil evaporation in an area characterized by low vegetation coverage.

  10. Transpiration rate. An important factor controlling the sucrose content of the guard cell apoplast of broad bean.

    PubMed

    Outlaw, W H; De Vlieghere-He, X

    2001-08-01

    Evaporation of water from the guard cell wall concentrates apoplastic solutes. We hypothesize that this phenomenon provides two mechanisms for responding to high transpiration rates. First, apoplastic abscisic acid is concentrated in the guard cell wall. Second, by accumulating in the guard cell wall, apoplastic sucrose (Suc) provides a direct osmotic feedback to guard cells. As a means of testing this second hypothesized mechanism, the guard cell Suc contents at a higher transpiration rate (60% relative humidity [RH]) were compared with those at a lower transpiration rate (90% RH) in broad bean (Vicia faba), an apoplastic phloem loader. In control plants (constant 60% RH), the guard cell apoplast Suc content increased from 97 +/- 81 femtomol (fmol) guard cell pair(-1) to 701 +/- 142 fmol guard cell pair(-1) between daybreak and midday. This increase is equivalent to approximately 150 mM external, which is sufficient to decrease stomatal aperture size. In plants that were shifted to 90% RH before daybreak, the guard cell apoplast Suc content did not increase during the day. In accordance, in plants that were shifted to 90% RH at midday, the guard cell apoplast Suc content declined to the daybreak value. Under all conditions, the guard cell symplast Suc content increased during the photoperiod, but the guard cell symplast Suc content was higher (836 +/- 33 fmol guard cell pair(-1)) in plants that were shifted to 90% RH. These results indicate that a high transpiration rate may result in a high guard cell apoplast Suc concentration, which diminishes stomatal aperture size. PMID:11500569

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

    PubMed

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

    2012-01-01

    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

  12. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf.

    PubMed

    Simonin, Kevin A; Burns, Emily; Choat, Brendan; Barbour, Margaret M; Dawson, Todd E; Franks, Peter J

    2015-03-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO₂ concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO₂ concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO₂ on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem-leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO₂ assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  13. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf

    PubMed Central

    Simonin, Kevin A.; Burns, Emily; Choat, Brendan; Barbour, Margaret M.; Dawson, Todd E.; Franks, Peter J.

    2015-01-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem–leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO2 concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO2 concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO2 on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem–leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915

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

    PubMed Central

    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

    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. PMID:22163656

  15. FPGA-based fused smart sensor for real-time plant-transpiration dynamic estimation.

    PubMed

    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

    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. PMID:22163656

  16. Plant canopy transpiration in bioregenerative life support systems - The link between mechanistic and empirical models

    NASA Technical Reports Server (NTRS)

    Sirko, Robert J.; Mccormack, Ann C.; Edeen, Marybeth A.

    1992-01-01

    A model of water transpiration in a plant canopy that combines two approaches is presented. The first approach is to account for underlying physical processes, while the second is to empirically incorporate transpiration data now being generated at the Johnson Center Variable Pressure Growth Chamber. The two approaches, physical modeling and data analysis, make it possible to produce a model that is more robust than either the standard first-principles model or a straightforward empirical model. It is shown that the present transpiration model is able to efficiently capture the dynamic behavior of the plant canopy over the entire range of environmental parameters now envisioned to be important in an operating controlled ecological life support system (CELSS). Examples of the use of this model in assessing plant canopy dynamics and CELSS design options are also presented.

  17. Role of transpiration and metabolism in translocation and accumulation of cadmium in tobacco plants (Nicotiana tabacum L.).

    PubMed

    Liu, Haiwei; Wang, Haiyun; Ma, Yibing; Wang, Haohao; Shi, Yi

    2016-02-01

    Tobacco plants grown in pots and in hydroponic culture accumulated cadmium (Cd) particularly: the Cd content of tobacco leaves exceeded 100 mg/kg and the enrichment factor (the ratio of Cd in leaves to that in soil) was more than 4. These high levels of accumulation identify tobacco as a hyperaccumulator of Cd. Two transpiration inhibitors (paraffin or CaCl2) and shade decreased the Cd content of tobacco leaves, and the decrease showed a linear relationship with the leaf transpiration rate. A metabolism inhibitor, namely 2,4-dinitrophenol (DNP), and low temperature (4 °C) also lowered the Cd content of tobacco leaves, but the inhibitory effect of low temperature was greater. In the half number of leaves that were shaded, the Cd content decreased to 26.5% of that in leaves that were not shaded in the same tobacco plants. These results suggests that translocation of Cd from the medium to the leaves is driven by the symplastic and the apoplastic pathways. Probably, of the two crucial steps in the translocation of Cd in tobacco plants, one, namely uptake from the medium to the xylem, is energy-dependent whereas the other, namely the transfer from the xylem to the leaves, is driven mainly by transpiration. PMID:26547876

  18. Effect of Transpiration on Plant Accumulation and Translocation of PPCP/EDCs

    PubMed Central

    Dodgen, Laurel K; Ueda, Aiko; Wu, Xiaoqin; Parker, David R; Gan, Jay

    2015-01-01

    The reuse of treated wastewater for agricultural irrigation in arid and hot climates where plant transpiration is high may affect plant accumulation of pharmaceutical and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs). In this study, carrot, lettuce, and tomato plants were grown in solution containing 16 PPCP/EDCs in either a cool-humid or a warm-dry environment. Leaf bioconcentration factors (BCF) were positively correlated with transpiration for chemical groups of different ionized states (p < 0.05). However, root BCFs were correlated with transpiration only for neutral PPCP/EDCs (p < 0.05). Neutral and cationic PPCP/EDCs showed similar accumulation, while anionic PPCP/EDCs had significantly higher accumulation in roots and significantly lower accumulation in leaves (p < 0.05). Results show that plant transpiration may play a significant role in the uptake and translocation of PPCP/EDCs, which may have a pronounced effect in arid and hot climates where irrigation with treated wastewater is common. PMID:25594843

  19. Effect of transpiration on plant accumulation and translocation of PPCP/EDCs.

    PubMed

    Dodgen, Laurel K; Ueda, Aiko; Wu, Xiaoqin; Parker, David R; Gan, Jay

    2015-03-01

    The reuse of treated wastewater for agricultural irrigation in arid and hot climates where plant transpiration is high may affect plant accumulation of pharmaceutical and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs). In this study, carrot, lettuce, and tomato plants were grown in solution containing 16 PPCP/EDCs in either a cool-humid or a warm-dry environment. Leaf bioconcentration factors (BCF) were positively correlated with transpiration for chemical groups of different ionized states (p < 0.05). However, root BCFs were correlated with transpiration only for neutral PPCP/EDCs (p < 0.05). Neutral and cationic PPCP/EDCs showed similar accumulation, while anionic PPCP/EDCs had significantly higher accumulation in roots and significantly lower accumulation in leaves (p < 0.05). Results show that plant transpiration may play a significant role in the uptake and translocation of PPCP/EDCs, which may have a pronounced effect in arid and hot climates where irrigation with treated wastewater is common. PMID:25594843

  20. Applicability of high rate transpiration system for treatment of biologically treated distillery effluent.

    PubMed

    Singh, S K; Juwarkar, Asha A; Pandey, R A; Chakrabarti, T

    2008-06-01

    The biologically treated distillery effluent (BTDE) contains intense colour, high total dissolved solids (TDS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). These properties even after primary, secondary and tertiary treatments contain high concentrations of TDS, COD and BOD. The paper highlights the safe disposal and treatment of BTDE on land through High Rate Transpiration System (HRTS). HRTS is a zero discharge, low cost, high-tech method for improving the quality of BTDE for potential reuse. The experiments conducted at bench and pilot scale showed that HRTS having coconut husk as a bedding material could successfully treat the BTDE with a hydraulic load of 200 m3 ha(-1) day(-1) having BOD of 100 mg l(-1) and 500 m3 ha(-1) day(-1) having BOD of 500 mg l(-1) with average COD load of 0.686 and 2.88 ton ha(-1) day(-1) during the post and pre monsoon periods respectively. There was no significant increase in the organic carbon of the soil irrigated with BTDE. The concentrations of various pollutants analyzed in the leachate were within the prescribed limit for the drinking water sources. The colour removal was 99 to 100% and BOD and COD were possible to treat with optimum hydraulic loading of BTDE through HRTS planted with Dendrocalamus strictus. PMID:17882528

  1. A Laboratory Exercise to Assess Transpiration.

    ERIC Educational Resources Information Center

    Schrock, Gould F.

    1982-01-01

    Procedures are outlined for a laboratory exercise in which students use a gravimetric method to determine the rate of transpiration in sunflower seedlings. Discusses the data in terms of the effectiveness of stomatal openings, mechanisms for water movement in plants, and the role of transpiration in the environment. (DC)

  2. From evaporating pans to transpiring plants (John Dalton Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Roderick, Michael

    2013-04-01

    observations that win. That is the basis of science. In this Dalton Medal lecture we first examine pan evaporation observations and show why pan evaporation has declined. Armed with that knowledge we then investigate the consequences for plant water use and how this is directly coupled to the catchment water balance.

  3. Mesoscopic aspects of root water uptake modeling - Hydraulic resistances and root geometry interpretations in plant transpiration analysis

    NASA Astrophysics Data System (ADS)

    Vogel, Tomas; Votrubova, Jana; Dusek, Jaromir; Dohnal, Michal

    2016-02-01

    In the context of soil water flow modeling, root water uptake is often evaluated based on water potential difference between the soil and the plant (the water potential gradient approach). Root water uptake rate is modulated by hydraulic resistance of both the root itself, and the soil in the root vicinity. The soil hydraulic resistance is a function of actual soil water content and can be assessed assuming radial axisymmetric water flow toward a single root (at the mesoscopic scale). In the present study, three approximate solutions of mesoscopic root water uptake - finite difference approximation, steady-state solution, and steady-rate solution - are examined regarding their ability to capture the pressure head variations in the root vicinity. Insignificance of their differences when implemented in the macroscopic soil water flow model is demonstrated using the critical root water uptake concept. Subsequently, macroscopic simulations of coupled soil water flow and root water uptake are presented for a forest site under temperate humid climate. Predicted soil water pressure heads and actual transpiration rates are compared with observed data. Scenario simulations illustrate uncertainties associated with estimates of root geometrical and hydraulic properties. Regarding the actual transpiration prediction, the correct characterization of active root system geometry and hydraulic properties seems far more important than the choice of a particular mesoscopic model.

  4. 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)

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

    2012-12-01

    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

  5. Measuring diurnal cycles of plant transpiration fluxes in the Arctic with an automated clear chamber

    NASA Astrophysics Data System (ADS)

    Cohen, L. R.; Raz Yaseef, N.; Curtis, J. B.; Rahn, T. A.; Young, J. M.; Newman, B. D.

    2013-12-01

    Evapotranspiration is an important greenhouse gas and a major component of the hydrological cycle, but methodological challenges still limit our knowledge of this flux. Measuring evapotranspiration is even more difficult when aiming to partition plant transpiration and soil evaporation. Information on this process for arctic systems is very limited. In order to decrease this gap, our objective was to directly measure plant transpiration in Barrow, Alaska (71.3°N 156.7°W). A commercial system allows measuring carbon soil respiration fluxes with an automated clear chamber connected to an infrared gas-analyzer (Licor 8100), and while it simultaneously measures water concentrations, it is not calibrated to measure vapor fluxes. We calibrated the clear chamber against a previously established method based on a Licor 6400 soil chamber, and we developed a code to calculate fluxes. We performed laboratory comparisons in New Mexico and field comparisons in the Arctic, suggesting that this is a valid tool for a large range of climates. In the field we found a strong correlation between the two instruments with R2 of 0.79. Even with 24 hours of daylight in the Arctic, the system captures a clear diurnal transpiration flux, peaking at 0.9 mmol m-2 s-1 and showing no flux at the lowest points. This new method should be a powerful approach for long term measurements of specific vegetation types or surface features. Such Data can also be used to help understand controls on larger scale eddy covariance tower measurements of evapotranspiration.

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

    PubMed Central

    Hosy, Eric; Vavasseur, Alain; Mouline, Karine; Dreyer, Ingo; Gaymard, Frédéric; Porée, Fabien; Boucherez, Jossia; Lebaudy, Anne; Bouchez, David; Véry, Anne-Aliénor; Simonneau, Thierry; Thibaud, Jean-Baptiste; Sentenac, Hervé

    2003-01-01

    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. PMID:12671068

  7. Genetic variation in transpiration efficiency and relationships between whole plant and leaf gas exchange measurements in Saccharum spp. and related germplasm.

    PubMed

    Jackson, Phillip; Basnayake, Jaya; Inman-Bamber, Geoff; Lakshmanan, Prakash; Natarajan, Sijesh; Stokes, Chris

    2016-02-01

    Fifty-one genotypes of sugarcane (Saccharum spp.) or closely related germplasm were evaluated in a pot experiment to examine genetic variation in transpiration efficiency. Significant variation in whole plant transpiration efficiency was observed, with the difference between lowest and highest genotypes being about 40% of the mean. Leaf gas exchange measurements were made across a wide range of conditions. There was significant genetic variation in intrinsic transpiration efficiency at a leaf level as measured by leaf internal CO2 (Ci) levels. Significant genetic variation in Ci was also observed within subsets of data representing narrow ranges of stomatal conductance. Ci had a low broad sense heritability (Hb = 0.11) on the basis of single measurements made at particular dates, because of high error variation and genotype × date interaction, but broad sense heritability for mean Ci across all dates was high (Hb = 0.81) because of the large number of measurements taken at different dates. Ci levels among genotypes at mid-range levels of conductance had a strong genetic correlation (-0.92 ± 0.30) with whole plant transpiration efficiency but genetic correlations between Ci and whole plant transpiration efficiency were weaker or not significant at higher and lower levels of conductance. Reduced Ci levels at any given level of conductance may result in improved yields in water-limited environments without trade-offs in rates of water use and growth. Targeted selection and improvement of lowered Ci per unit conductance via breeding may provide longer-term benefits for water-limited environments but the challenge will be to identify a low-cost screening methodology. PMID:26628517

  8. Genetic variation in transpiration efficiency and relationships between whole plant and leaf gas exchange measurements in Saccharum spp. and related germplasm

    PubMed Central

    Jackson, Phillip; Basnayake, Jaya; Inman-Bamber, Geoff; Lakshmanan, Prakash; Natarajan, Sijesh; Stokes, Chris

    2016-01-01

    Fifty-one genotypes of sugarcane (Saccharum spp.) or closely related germplasm were evaluated in a pot experiment to examine genetic variation in transpiration efficiency. Significant variation in whole plant transpiration efficiency was observed, with the difference between lowest and highest genotypes being about 40% of the mean. Leaf gas exchange measurements were made across a wide range of conditions. There was significant genetic variation in intrinsic transpiration efficiency at a leaf level as measured by leaf internal CO2 (Ci) levels. Significant genetic variation in Ci was also observed within subsets of data representing narrow ranges of stomatal conductance. Ci had a low broad sense heritability (Hb = 0.11) on the basis of single measurements made at particular dates, because of high error variation and genotype × date interaction, but broad sense heritability for mean Ci across all dates was high (Hb = 0.81) because of the large number of measurements taken at different dates. Ci levels among genotypes at mid-range levels of conductance had a strong genetic correlation (−0.92 ± 0.30) with whole plant transpiration efficiency but genetic correlations between Ci and whole plant transpiration efficiency were weaker or not significant at higher and lower levels of conductance. Reduced Ci levels at any given level of conductance may result in improved yields in water-limited environments without trade-offs in rates of water use and growth. Targeted selection and improvement of lowered Ci per unit conductance via breeding may provide longer-term benefits for water-limited environments but the challenge will be to identify a low-cost screening methodology. PMID:26628517

  9. Photosynthesis, transpiration and water use efficiencies of a plant canopy and plant leaves under restricted air current conditions

    NASA Astrophysics Data System (ADS)

    Kitaya, Yoshiaki; Shibuya, Toshio; Tsuruyama, Joshin

    A fundamental study was conducted to obtain the knowledge for culturing plants and exchanging gases with plants under restricted air circulation conditions in space agriculture. The effects of air velocities less than 1.3 m s-1 on net photosynthetic rates (Pn), transpiration rates (Tr) and Pn/Tr, water use efficiencies (WUE), of a canopy of cucumber seedlings and of single leaves of cucumber, sweet potato and barley were assessed with assimilation chamber methods in ground based experiments. The cucumber seedling canopy, which had a LAI of 1.4 and height of 0.1 m, was set in a wind tunnel installed in a plant canopy assimilation chamber. Each of the attached single leaves was set in a leaf assimilation chamber. The Pn and Tr of the plant canopy increased to 1.2 and 2.8 times, respectively, and WUE decreased to 0.4 times with increasing the air velocity from 0.02 to 1.3 m s-1. The Pn and Tr of the single leaves of all the species increased by 1.3-1.7 and 1.9-2.2 times, respectively, and WUE decreased to 0.6-0.8 times as the air velocity increased from 0.05 to 0.8 m s-1. The effect of air velocity was more significant on Tr than on Pn and thus WUE decreased with increasing air velocity in both the plant canopy and the individual leaves. The leaf boundary layer resistance was approximately proportional to the minus 1/3 power of the air velocity. Stomatal resistance was almost constant during the experiment. The CO2 concentrations in the sub-stomatal cavity in leaves of cucumber, sweet potato and barley, respectively, were 43, 31 and 58 mmol mol-1 lower at the air velocity of 0.05 m s-1 than at the air velocity of 0.8 m s-1, while the water vapor pressure in the sub-stomatal cavity was constant. We concluded that the change in the CO2 concentration in the sub-stomatal cavity was a cause of the different effect of the air velocity on Pn and Tr, and thus on WUE. The phenomenon will be more remarkable under restricted air convection conditions at lower gravity in space.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  11. Overexpression of Rice NAC Gene SNAC1 Improves Drought and Salt Tolerance by Enhancing Root Development and Reducing Transpiration Rate in Transgenic Cotton

    PubMed Central

    Liu, Guanze; Li, Xuelin; Jin, Shuangxia; Liu, Xuyan; Zhu, Longfu; Nie, Yichun; Zhang, Xianlong

    2014-01-01

    The SNAC1 gene belongs to the stress-related NAC superfamily of transcription factors. It was identified from rice and overexpressed in cotton cultivar YZ1 by Agrobacterium tumefaciens-mediated transformation. SNAC1-overexpressing cotton plants showed more vigorous growth, especially in terms of root development, than the wild-type plants in the presence of 250 mM NaCl under hydroponic growth conditions. The content of proline was enhanced but the MDA content was decreased in the transgenic cotton seedlings under drought and salt treatments compared to the wild-type. Furthermore, SNAC1-overexpressing cotton plants also displayed significantly improved tolerance to both drought and salt stresses in the greenhouse. The performances of the SNAC1-overexpressing lines under drought and salt stress were significantly better than those of the wild-type in terms of the boll number. During the drought and salt treatments, the transpiration rate of transgenic plants significantly decreased in comparison to the wild-type, but the photosynthesis rate maintained the same at the flowering stage in the transgenic plants. These results suggested that overexpression of SNAC1 improve more tolerance to drought and salt in cotton through enhanced root development and reduced transpiration rates. PMID:24489802

  12. Transpiration and metabolisation of TCE by willow plants - a pot experiment.

    PubMed

    Schöftner, Philipp; Watzinger, Andrea; Holzknecht, Philipp; Wimmer, Bernhard; Reichenauer, Thomas G

    2016-07-01

    Willows were grown in glass cylinders filled with compost above water-saturated quartz sand, to trace the fate of TCE in water and plant biomass. The experiment was repeated once with the same plants in two consecutive years. TCE was added in nominal concentrations of 0, 144, 288, and 721 mg l(-1). Unplanted cylinders were set-up and spiked with nominal concentrations of 721 mg l(-1) TCE in the second year. Additionally, (13)C-enriched TCE solution (δ(13)C = 110.3 ‰) was used. Periodically, TCE content and metabolites were analyzed in water and plant biomass. The presence of TCE-degrading microorganisms was monitored via the measurement of the isotopic ratio of carbon ((13)C/(12)C) in TCE, and the abundance of (13)C-labeled microbial PLFAs (phospholipid fatty acids). More than 98% of TCE was lost via evapotranspiration from the planted pots within one month after adding TCE. Transpiration accounted to 94 to 78% of the total evapotranspiration loss. Almost 1% of TCE was metabolized in the shoots, whereby trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were dominant metabolites; less trichloroethanol (TCOH) and TCE accumulated in plant tissues. Microbial degradation was ruled out by δ(13)C measurements of water and PLFAs. TCE had no detected influence on plant stress status as determined by chlorophyll-fluorescence and gas exchange. PMID:26684839

  13. Ecohydrology of groundwater-dependent ecosystems: a stochastic framework for plant transpiration

    NASA Astrophysics Data System (ADS)

    Tamea, S.; Laio, F.; Ridolfi, L.; D'Odorico, P.; Rodriguez-Iturbe, I.

    2009-04-01

    Groundwater-dependent ecosystems are found in areas with a shallow water table, where the groundwater plays a key role on the ecosystem functions. In these areas, the water table depth, the capillary fluxes, and the soil moisture content exert a major control on most ecohydrologic processes, such as infiltration, surface runoff, aquifer recharge, land-atmosphere feedbacks, vegetation dynamics, nutrient cycling, and pollutant transport. Understanding and modeling the soil water balance and its relationships with climate, soil, and vegetation is therefore a crucial aspect for geosciences such as hydrology and ecology. The ecohydrology of groundwater-dependent ecosystems can be described with a modeling framework based on a stochastic process-based water balance. The model is driven by a compound marked Poisson noise representing the rainfall events and, under some simplifying, yet realistic, assumptions, it includes rainfall infiltration, root water uptake, capillary flux, and subsurface flow to/from an external water body. The framework provides the long-term probability distribution of water table depth and of soil moisture vertical profiles, enabling a quantitative study of the local hydrology with a limited number of parameters. We here apply this framework to investigate plant transpiration and root water uptake. The probability distributions of water uptake are derived from those of the soil water content and are investigated for different scenarios of climate, soil, and vegetation. The results of this approach allow for interesting speculations about the groundwater contribution to root uptake, the soil water available for plant transpiration, and the optimal strategies of root growth and plant competition. This information is useful to assess the impact of climate changes, vegetation modification, and water management operations.

  14. Transpiration cooling of hypersonic blunt bodies with finite rate surface reactions

    NASA Technical Reports Server (NTRS)

    Henline, William D.

    1989-01-01

    The convective heat flux blockage to blunt body and hypersonic vehicles by transpiration cooling are presented. The general problem of mass addition to laminar boundary layers is reviewed. Results of similarity analysis of the boundary layer problem are provided for surface heat flux with transpiration cooling. Detailed non-similar results are presented from the numerical program, BLIMPK. Comparisons are made with the similarity theory. The effects of surface catalysis are investigated.

  15. Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.

    PubMed

    Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M

    2013-12-01

    During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents. PMID:23647101

  16. High resolution mapping of traits related to whole-plant transpiration under increasing evaporative demand in wheat.

    PubMed

    Schoppach, Rémy; Taylor, Julian D; Majerus, Elisabeth; Claverie, Elodie; Baumann, Ute; Suchecki, Radoslaw; Fleury, Delphine; Sadok, Walid

    2016-04-01

    Atmospheric vapor pressure deficit (VPD) is a key component of drought and has a strong influence on yields. Whole-plant transpiration rate (TR) response to increasing VPD has been linked to drought tolerance in wheat, but because of its challenging phenotyping, its genetic basis remains unexplored. Further, the genetic control of other key traits linked to daytime TR such as leaf area, stomata densities and - more recently - nocturnal transpiration remains unknown. Considering the presence of wheat phenology genes that can interfere with drought tolerance, the aim of this investigation was to identify at an enhanced resolution the genetic basis of the above traits while investigating the effects of phenology genes Ppd-D1 and Ppd-B1 Virtually all traits were highly heritable (heritabilities from 0.61 to 0.91) and a total of mostly trait-specific 68 QTL were detected. Six QTL were identified for TR response to VPD, with one QTL (QSLP.ucl-5A) individually explaining 25.4% of the genetic variance. This QTL harbored several genes previously reported to be involved in ABA signaling, interaction with DREB2A and root hydraulics. Surprisingly, nocturnal TR and stomata densities on both leaf sides were characterized by highly specific and robust QTL. In addition, negative correlations were found between TR and leaf area suggesting trade-offs between these traits. Further, Ppd-D1 had strong but opposite effects on these traits, suggesting an involvement in this trade-off. Overall, these findings revealed novel genetic resources while suggesting a more direct role of phenology genes in enhancing wheat drought tolerance. PMID:27001921

  17. High resolution mapping of traits related to whole-plant transpiration under increasing evaporative demand in wheat

    PubMed Central

    Schoppach, Rémy; Taylor, Julian D; Majerus, Elisabeth; Claverie, Elodie; Baumann, Ute; Suchecki, Radoslaw; Fleury, Delphine; Sadok, Walid

    2016-01-01

    Atmospheric vapor pressure deficit (VPD) is a key component of drought and has a strong influence on yields. Whole-plant transpiration rate (TR) response to increasing VPD has been linked to drought tolerance in wheat, but because of its challenging phenotyping, its genetic basis remains unexplored. Further, the genetic control of other key traits linked to daytime TR such as leaf area, stomata densities and – more recently – nocturnal transpiration remains unknown. Considering the presence of wheat phenology genes that can interfere with drought tolerance, the aim of this investigation was to identify at an enhanced resolution the genetic basis of the above traits while investigating the effects of phenology genes Ppd-D1 and Ppd-B1. Virtually all traits were highly heritable (heritabilities from 0.61 to 0.91) and a total of mostly trait-specific 68 QTL were detected. Six QTL were identified for TR response to VPD, with one QTL (QSLP.ucl-5A) individually explaining 25.4% of the genetic variance. This QTL harbored several genes previously reported to be involved in ABA signaling, interaction with DREB2A and root hydraulics. Surprisingly, nocturnal TR and stomata densities on both leaf sides were characterized by highly specific and robust QTL. In addition, negative correlations were found between TR and leaf area suggesting trade-offs between these traits. Further, Ppd-D1 had strong but opposite effects on these traits, suggesting an involvement in this trade-off. Overall, these findings revealed novel genetic resources while suggesting a more direct role of phenology genes in enhancing wheat drought tolerance. PMID:27001921

  18. 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...

  19. Sapfluxnet: a global database of sap flow measurements to unravel the ecological factors of transpiration regulation in woody plants

    NASA Astrophysics Data System (ADS)

    Poyatos, Rafael; Martínez-Vilalta, Jordi; Molowny-Horas, Roberto; Steppe, Kathy; Oren, Ram; Katul, Gabriel; Mahecha, Miguel

    2016-04-01

    Plant transpiration is one of the main components of the global water cycle, it controls land energy balance, determines catchment hydrological responses and exerts strong feedbacks on regional and global climate. At the same time, plant productivity, growth and survival are severely constrained by water availability, which is expected to decline in many areas of the world because of global-change driven increases in drought conditions. While global surveys of drought tolerance traits at the organ level are rapidly increasing our knowledge of the diversity in plant functional strategies to cope with drought stress, a whole-plant perspective of drought vulnerability is still lacking. Sap flow measurements using thermal methods have now been applied to measure seasonal patterns in water use and the response of transpiration to environmental drivers across hundreds of species of woody plants worldwide, covering a wide range of climates, soils and stand structural characteristics. Here, we present the first effort to build a global database of sub-daily, tree-level sap flow (SAPFLUXNET) that will be used to improve our understanding of physiological and structural determinants of plant transpiration and to further investigate the role of vegetation in controlling global water balance. We already have the expression of interest of data contributors representing >115 globally distributed sites, > 185 species and > 700 trees, measured over at least one growing season. However, the potential number of available sites and species is probably much higher given that > 2500 sap flow-related papers have been identified in a Scopus literature search conducted in November 2015. We will give an overview of how data collection, harmonisation and quality control procedures are implemented within the project. We will also discuss potential analytical strategies to synthesize hydroclimatic controls on sap flow into biologically meaningful traits related to whole-plant transpiration

  20. Effectiveness of cuticular transpiration barriers in a desert plant at controlling water loss at high temperatures.

    PubMed

    Schuster, Ann-Christin; Burghardt, Markus; Alfarhan, Ahmed; Bueno, Amauri; Hedrich, Rainer; Leide, Jana; Thomas, Jacob; Riederer, Markus

    2016-01-01

    Maintaining the integrity of the cuticular transpiration barrier even at elevated temperatures is of vital importance especially for hot-desert plants. Currently, the temperature dependence of the leaf cuticular water permeability and its relationship with the chemistry of the cuticles are not known for a single desert plant. This study investigates whether (i) the cuticular permeability of a desert plant is lower than that of species from non-desert habitats, (ii) the temperature-dependent increase of permeability is less pronounced than in those species and (iii) whether the susceptibility of the cuticular permeability barrier to high temperatures is related to the amounts or properties of the cutin or the cuticular waxes. We test these questions with Rhazya stricta using the minimum leaf water vapour conductance (gmin) as a proxy for cuticular water permeability. gmin of R. stricta (5.41 × 10(-5) m s(-1) at 25 °C) is in the upper range of all existing data for woody species from various non-desert habitats. At the same time, in R. stricta, the effect of temperature (15-50 °C) on gmin (2.4-fold) is lower than in all other species (up to 12-fold). Rhazya stricta is also special since the temperature dependence of gmin does not become steeper above a certain transition temperature. For identifying the chemical and physical foundation of this phenomenon, the amounts and the compositions of cuticular waxes and cutin were determined. The leaf cuticular wax (251.4 μg cm(-2)) is mainly composed of pentacyclic triterpenoids (85.2% of total wax) while long-chain aliphatics contribute only 3.4%. In comparison with many other species, the triterpenoid-to-cutin ratio of R. stricta (0.63) is high. We propose that the triterpenoids deposited within the cutin matrix restrict the thermal expansion of the polymer and, thus, prevent thermal damage to the highly ordered aliphatic wax barrier even at high temperatures. PMID:27154622

  1. Effectiveness of cuticular transpiration barriers in a desert plant at controlling water loss at high temperatures

    PubMed Central

    Schuster, Ann-Christin; Burghardt, Markus; Alfarhan, Ahmed; Bueno, Amauri; Hedrich, Rainer; Leide, Jana; Thomas, Jacob; Riederer, Markus

    2016-01-01

    Maintaining the integrity of the cuticular transpiration barrier even at elevated temperatures is of vital importance especially for hot-desert plants. Currently, the temperature dependence of the leaf cuticular water permeability and its relationship with the chemistry of the cuticles are not known for a single desert plant. This study investigates whether (i) the cuticular permeability of a desert plant is lower than that of species from non-desert habitats, (ii) the temperature-dependent increase of permeability is less pronounced than in those species and (iii) whether the susceptibility of the cuticular permeability barrier to high temperatures is related to the amounts or properties of the cutin or the cuticular waxes. We test these questions with Rhazya stricta using the minimum leaf water vapour conductance (gmin) as a proxy for cuticular water permeability. gmin of R. stricta (5.41 × 10−5 m s−1 at 25 °C) is in the upper range of all existing data for woody species from various non-desert habitats. At the same time, in R. stricta, the effect of temperature (15–50 °C) on gmin (2.4-fold) is lower than in all other species (up to 12-fold). Rhazya stricta is also special since the temperature dependence of gmin does not become steeper above a certain transition temperature. For identifying the chemical and physical foundation of this phenomenon, the amounts and the compositions of cuticular waxes and cutin were determined. The leaf cuticular wax (251.4 μg cm−2) is mainly composed of pentacyclic triterpenoids (85.2% of total wax) while long-chain aliphatics contribute only 3.4%. In comparison with many other species, the triterpenoid-to-cutin ratio of R. stricta (0.63) is high. We propose that the triterpenoids deposited within the cutin matrix restrict the thermal expansion of the polymer and, thus, prevent thermal damage to the highly ordered aliphatic wax barrier even at high temperatures. PMID:27154622

  2. Transpiration cooling in hypersonic flight

    NASA Technical Reports Server (NTRS)

    Tavella, Domingo; Roberts, Leonard

    1989-01-01

    A preliminary numerical study of transpiration cooling applied to a hypersonic configuration is presented. Air transpiration is applied to the NASA all-body configuration flying at an altitude of 30500 m with a Mach number of 10.3. It was found that the amount of heat disposal by convection is determined primarily by the local geometry of the aircraft for moderate rates of transpiration. This property implies that different areas of the aircraft where transpiration occurs interact weakly with each other. A methodology for quick assessments of the transpiration requirements for a given flight configuration is presented.

  3. Simulating canopy transpiration and photosynthesis of corn plants under contrasting water regimes using a coupled model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A process-based corn simulation model (MaizeSim) was coupled with a two-dimensional soil simulator (2DSOIL) to simulate the transpiration and photosynthesis of corn under drought stress. To simulate stomatal reaction to drought stress, two stomatal controlling algorithms (control by hydraulic signal...

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

    PubMed

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

    2010-08-01

    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 (ψ(s)). PMID:20566582

  5. Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon–juniper woodland

    DOE PAGESBeta

    Pangle, Robert E.; Limousin, Jean -Marc; Plaut, Jennifer A.; Yepez, Enrico A.; Hudson, Patrick J.; Boutz, Amanda L.; Gehres, Nathan; Pockman, William T.; McDowell, Nate G.

    2015-03-23

    Plant hydraulic conductance (ks) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between ks and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (EC) and conductance (GC). For both species, we observed significant reductionsmore » in plant transpiration (E) and ks under experimentally imposed drought. Conversely, supplemental water additions increased E and ks in both species. Interestingly, both species exhibited similar declines in ks under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant ks also reduced carbon assimilation in both species, as leaf-level stomatal conductance (gs) and net photosynthesis (An) declined strongly with decreasing ks. Finally, we observed that chronically low whole-plant ks was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy EC and GC. Our data indicate that significant reductions in ks precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon–juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent

  6. Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon–juniper woodland

    PubMed Central

    Pangle, Robert E; Limousin, Jean-Marc; Plaut, Jennifer A; Yepez, Enrico A; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Pockman, William T; McDowell, Nate G

    2015-01-01

    Plant hydraulic conductance (ks) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between ks and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (EC) and conductance (GC). For both species, we observed significant reductions in plant transpiration (E) and ks under experimentally imposed drought. Conversely, supplemental water additions increased E and ks in both species. Interestingly, both species exhibited similar declines in ks under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant ks also reduced carbon assimilation in both species, as leaf-level stomatal conductance (gs) and net photosynthesis (An) declined strongly with decreasing ks. Finally, we observed that chronically low whole-plant ks was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy EC and GC. Our data indicate that significant reductions in ks precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon–juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent

  7. Unveiling stomata 24/7: can we use carbonyl sulfide (COS) and oxygen isotopes (18O) to constrain estimates of nocturnal transpiration across different evolutionary plant forms?

    NASA Astrophysics Data System (ADS)

    Gimeno, Teresa E.; Ogee, Jerome; Bosc, Alexander; Genty, Bernard; Wohl, Steven; Wingate, Lisa

    2015-04-01

    Numerous studies have reported a continued flux of water through plants at night, suggesting that stomata are not fully closed. Growing evidence indicates that this nocturnal flux of transpiration might constitute an important fraction of total ecosystem water use in certain environments. However, because evaporative demand is usually low at night, nocturnal transpiration fluxes are generally an order of magnitude lower than rates measured during the day and perilously close to the measurement error of traditional gas-exchange porometers. Thus estimating rates of stomatal conductance in the dark (gnight) precisely poses a significant methodological challenge. As a result, we lack accurate field estimates of gnight and how it responds to different atmospheric drivers, indicating the need for a different measurement approach. In this presentation we propose a novel method to obtain detectable and robust estimates of gnight. We will demonstrate using mechanistic theory how independent tracers including the oxygen isotope composition of CO2 (δ18O) and carbonyl sulfide (COS) can be combined to obtain robust estimates of gnight. This is because COS and CO18O exchange within leaves are controlled by the light insensitive enzyme carbonic anhydrase. Thus, if plant stomata are open in the dark we will continue to observe COS and CO18O exchange. Using our theoretical model we will demonstrate that the exchange of these tracers can now be measured using advances in laser spectrometry techniques at a precision high enough to determine robust estimates of gnight. We will also present our novel experimental approach designed to measure simultaneously the exchange of CO18O and COS alongside the conventional technique that relies on measuring the total water flux from leaves in the dark. Using our theoretical approach we will additionally explore the feasibility of our proposed experimental design to detect variations in gnight during drought stress and across a variety of plant

  8. Thermophoretically enhanced mass transport rates to solid and transpiration-cooled walls across turbulent (law-of-the-wall) boundary layers

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Rosner, Daniel E.

    1985-01-01

    Convective-diffusion mass transfer rate predictions are made for both solid wall and transpiration-cooled 'law-of-the-wall' nonisothermal turbulent boundary layers (TBLs), including the mechanism of thermophoresis, i.e., small particle mass transport 'down a temperature gradient'. The present calculations are confined to low mass-loading situations but span the entire particle size range from vapor molecules to particles near the onset of inertial ('eddy') impaction. It is shown that, when Sc is much greater than 1, thermophoresis greatly increases particle deposition rates to internally cooled solid walls, but only partially offsets the appreciable reduction in deposition rates associated with dust-free gas-transpiration-cooled surfaces. Thus, efficient particle sampling from hot dusty gases can be carried out using transpiration 'shielded' probe surfaces.

  9. Climate Change at Northern Latitudes: Rising Atmospheric Humidity Decreases Transpiration, N-Uptake and Growth Rate of Hybrid Aspen

    PubMed Central

    Tullus, Arvo; Kupper, Priit; Sellin, Arne; Parts, Leopold; Sõber, Jaak; Tullus, Tea; Lõhmus, Krista; Sõber, Anu; Tullus, Hardi

    2012-01-01

    At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008–2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect – inhibition of above-ground growth rate – was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO3− in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO2 concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place. PMID:22880067

  10. Quantifying the Components of Evapotranspiration from Plant Communities, Soil Evaporation and Plant Transpiration, with Isotopes and Micrometeorology

    NASA Astrophysics Data System (ADS)

    Denmead, O. Tom; Heng, L.; Zeeman, Matthias

    2016-04-01

    Isotope fractionation has been used in recent years to separate the components of evapotranspiration (ET):soil evaporation (E) and plant transpiration T. The technique estimates the ratio of T to ET, but without further information on the magnitude of ET, can not estimate the magnitudes of the components. To accomplish this, we conducted a study using the micrometeorological technique of eddy covariance to determine ET for a developing crop of winter wheat in conjunction with measurement of enrichment of the isotopes 18O and H2 in the vertical profiles of water vapour within and above the crop canopy. As well, the study employed a second micrometeorological technique based on a Lagrangian description of dispersion in the canopy (Raupach, 1989) to infer the source strengths for water vapour at the soil surface and in the various foliage layers in the canopy. Lagrangian dispersion analysis provides a means of linking canopy sources and sinks with mean concentration profiles using statistics of the turbulence in and above the canopy. Forward Lagrangian dispersion analysis predicts mean concentration profiles generated by given canopy source distributions. It uses a Lagrangian (fluid-following) framework to track an ensemble of "marked fluid particles" as they disperse. Inverse Lagrangian dispersion analysis does the reverse of the forward analysis: it predicts source profiles from mean concentration profiles. The dispersion equation uses information on the turbulence and gas concentrations in the canopy to relate the concentrations at any level to the source strengths at all levels. The necessary turbulence statistics are the friction velocity (a measure of vertical turbulent exchange in the air flow over the plant canopy), the standard deviation of the vertical wind velocity, and the Lagrangian time scale (a measure of eddy coherence). The analysis calculates the contributions of the various canopy layers to the net flux. In this study, agreement between the

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 6οC 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 2-4οC 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

  12. Quantifying the feedback of evaporation and transpiration rates to soil moisture dynamics and meteorological condition changes by a numerical model

    NASA Astrophysics Data System (ADS)

    Su, Ye; Shao, Wei; Vlček, Lukáš; Langhammer, Jakub

    2015-04-01

    Evapotranspiration drives the hydrological process through energy-driven water-phase changes between systems of soil-vegetation-atmosphere. Evapotranspiration performs a rather complex process attributable to the spatial and temporal variation of soil-vegetation-atmosphere system. For vegetation-covered land surfaces, the transpiration process is governed by the stomatal behavior and water uptake from the root zone, and evaporation is related with the interception of rainfall and radiation on the canopy and soil surface. This study is emphasized on describing the hydrological process and energy cycle in a basic hydrological response unit, a hillslope. The experimental hillslope is located in an experimental catchment of the Bohemian Forest Mountains' headwaters in the Czech Republic, where is mostly covered by dead Norway spruce forest (Picea abies) stands caused by balk beetle outbreak. High-frequency monitoring network of the hydro-climatic data, soil pore water pressure and soil temperature has been launched since 2012. To conceptualize the land-surface energy and water fluxes in a complex hillslope, a soil-vegetation-atmosphere transport (SVAT) model, coupled with a multi-phase soil physics process (i.e. the water, vapor and heat flow transport) is used. We selected an 8-week basis dataset from 2013 as a pilot for partitioning the evapotranspiration into three interactive components: transpiration (Et), canopy interception evaporation (Ei), and soil evaporation (Es), by using this numerical model. Within such model framework, the sensitive feedback of evapotranspiration rates to rainfall intensity, soil moisture, and solar radiation will be examined by conducting numerical experiments to better understand the mechanism of evapotranspiration process under various influencing factors. Such application study and followed numerical simulations provide a new path for quantifying the behaviors of the soil-vegetation-atmosphere system.

  13. Continuous measurement of macronutrient ions in the transpiration stream of intact plants using the meadow spittlebug coupled with ion chromatography.

    PubMed

    Malone, Michael; Herron, Michelle; Morales, M-Angeles

    2002-11-01

    A method is described for continuous, nondestructive analysis of xylem-borne mineral nutrients in intact transpiring plants. The method uses the xylem-feeding insect the meadow spittlebug (Philaenus spumarius L. [Homoptera: Cercopidae]). This insect will feed from a wide range of plant species and organs. Insect excreta can be collected at all times of the day and night, and its mineral ion content can be analyzed rapidly, and without purification, by ion chromatography. The excreta will have a mineral content virtually identical to that of xylem sap. Cages suitable for containing the insects and collecting excreta from any desired location on plants in both laboratory and greenhouse are described. Even in the greenhouse, evaporation had only a minor effect on the sample ion content. Example results are presented which illustrate dynamics, over several days, in the xylem concentrations of sodium (Na(+)), potassium (K(+)), NH(4)(+), magnesium (Mg(2+)), calcium (Ca(2+)), chloride (Cl(-)), NO(3)(-), PO(4)(3-), and SO(4)(2-). These data were collected from young plants growing in pots of compost in the laboratory and from fully mature pepper (Capsicum annuum L. cv Bellboy) plants growing in hydroponics (rockwool) in the greenhouse. This method should facilitate studies of macronutrient uptake and transport in a range of plants and environments. PMID:12428008

  14. Nighttime transpiration is highly variable within a tallgrass prairie community

    NASA Astrophysics Data System (ADS)

    O'Keefe, K.; Nippert, J. B.

    2014-12-01

    Nighttime transpiration may have significant consequences on plant functioning and earth-atmosphere water fluxes, yet little is known about how this process can vary among species or with environmental changes, particularly in grassland ecosystems. We measured leaf-level nighttime transpiration and daytime photosynthetic rates, as well as whole-plant sap flow rates on eight grass, forb and shrub species in a Kansas tallgrass prairie. Measurements were made periodically across a single growing season (May-August 2014) on three C4 grasses (Andropogon gerardii, Sorghastrum nutans and Panicum virgatum), two C3 forbs (Vernonia baldwinii and Solidago canidensis), and three C3 shrubs (Cornus drummondii, Rhus glabra and Amorpha canescens). At the leaf level, nighttime transpiration rates varied among species and across the growing season. Nighttime transpiration was greater in the three grass species compared to the forbs and shrubs early in the growing season. As the growing season progressed, nighttime transpiration increased and then decreased in all species. These results are consistent with patterns of decreasing daytime stomatal conductance and photosynthetic rates as the growing season became hotter and drier. Nighttime sap flow rates also varied among species and typically accounted for over 10% of total daily water flux at the whole-plant level. These results show that nighttime transpiration is species specific and variable at a small spatial scale. Nighttime transpiration can therefore be a significant portion of a plant water budget in a tallgrass prairie, is highly variable within a community, and is dynamic in response to changing environmental conditions. Forecasts of future ecosystem responses to a changing climate must account for plant water use and loss at night.

  15. Genetic variation in a grapevine progeny (Vitis vinifera L. cvs Grenache×Syrah) reveals inconsistencies between maintenance of daytime leaf water potential and response of transpiration rate under drought

    PubMed Central

    Coupel-Ledru, Aude; Lebon, Éric; Christophe, Angélique; Doligez, Agnès; Cabrera-Bosquet, Llorenç; Péchier, Philippe; Hamard, Philippe; This, Patrice; Simonneau, Thierry

    2014-01-01

    In the face of water stress, plants evolved with different abilities to limit the decrease in leaf water potential, notably in the daytime (ΨM). So-called isohydric species efficiently maintain high ΨM, whereas anisohydric species cannot prevent ΨM from dropping as soil water deficit develops. The genetic and physiological origins of these differences in (an)isohydric behaviours remain to be clarified. This is of particular interest within species such as Vitis vinifera L. where continuous variation in the level of isohydry has been observed among cultivars. With this objective, a 2 year experiment was conducted on the pseudo-F1 progeny from a cross between the two widespread cultivars Syrah and Grenache using a phenotyping platform coupled to a controlled-environment chamber. Potted plants of all the progeny were analysed for ΨM, transpiration rate, and soil-to-leaf hydraulic conductance, under both well-watered and water deficit conditions. A high genetic variability was found for all the above traits. Four quantitative trait loci (QTLs) were detected for ΨM under water deficit conditions, and 28 other QTLs were detected for the different traits in either condition. Genetic variation in ΨM maintenance under water deficit weakly correlated with drought-induced reduction in transpiration rate in the progeny, and QTLs for both traits did not completely co-localize. This indicates that genetic variation in the control of ΨM under water deficit was not due simply to variation in transpiration sensitivity to soil drying. Possible origins of the diversity in (an)isohydric behaviours in grapevine are discussed on the basis of concurrent variations in soil-to-leaf hydraulic conductance and stomatal control of transpiration. PMID:25381432

  16. Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon–juniper woodland

    SciTech Connect

    Pangle, Robert E.; Limousin, Jean -Marc; Plaut, Jennifer A.; Yepez, Enrico A.; Hudson, Patrick J.; Boutz, Amanda L.; Gehres, Nathan; Pockman, William T.; McDowell, Nate G.

    2015-03-23

    Plant hydraulic conductance (ks) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between ks and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (EC) and conductance (GC). For both species, we observed significant reductions in plant transpiration (E) and ks under experimentally imposed drought. Conversely, supplemental water additions increased E and ks in both species. Interestingly, both species exhibited similar declines in ks under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant ks also reduced carbon assimilation in both species, as leaf-level stomatal conductance (gs) and net photosynthesis (An) declined strongly with decreasing ks. Finally, we observed that chronically low whole-plant ks was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy EC and GC. Our data indicate that significant reductions in ks precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon–juniper woodlands can be

  17. Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon-juniper woodland.

    PubMed

    Pangle, Robert E; Limousin, Jean-Marc; Plaut, Jennifer A; Yepez, Enrico A; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Pockman, William T; McDowell, Nate G

    2015-04-01

    Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between k s and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (E C) and conductance (G C). For both species, we observed significant reductions in plant transpiration (E) and k s under experimentally imposed drought. Conversely, supplemental water additions increased E and k s in both species. Interestingly, both species exhibited similar declines in k s under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant k s also reduced carbon assimilation in both species, as leaf-level stomatal conductance (g s) and net photosynthesis (A n) declined strongly with decreasing k s. Finally, we observed that chronically low whole-plant k s was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy E C and G C. Our data indicate that significant reductions in k s precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon-juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and

  18. Sap flow measurements to determine the transpiration of facade greenings

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  19. Water- and nitrogen-dependent alterations in the inheritance mode of transpiration efficiency in winter wheat at the leaf and whole-plant level.

    PubMed

    Ratajczak, Dominika; Górny, Andrzej G

    2012-11-01

    The effects of contrasting water and nitrogen (N) supply on the observed inheritance mode of transpiration efficiency (TE) at the flag-leaf and whole-season levels were examined in winter wheat. Major components of the photosynthetic capacity of leaves and the season-integrated efficiency of water use in vegetative and grain mass formation were evaluated in parental lines of various origins and their diallel F(2)-hybrids grown in a factorial experiment under different moisture and N status of the soil. A broad genetic variation was mainly found for the season-long TE measures. The variation range in the leaf photosynthetic indices was usually narrow, but tended to slightly enhance under water and N shortage. Genotype-treatment interaction effects were significant for most characters. No consistency between the leaf- and season-long TE measures was observed. Preponderance of additivity-dependent variance was mainly identified for the season-integrated TE and leaf CO(2) assimilation rate. Soil treatments exhibited considerable influence on the phenotypic expression of gene action for the residual leaf measures. The contribution of non-additive gene effects and degree of dominance tended to increase in water- and N-limited plants, especially for the leaf transpiration rate and stomatal conductance. The results indicate that promise exists to improve the season-integrated TE. However, selection for TE components should be prolonged for later hybrid generations to eliminate the masking of non-additive causes. Such evaluation among families grown under sub-optimal water and nitrogen supply seems to be the most promising strategy in winter wheat. PMID:22878956

  20. Estimating High Rates of Transpiration in Woody Vines with the Heat-Balance Method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat-balance sap flow gauges were configured to produce a more thermally uniform stem cross section under high flow rates. On mature grapevines (Vitis labruscana) either undisturbed in the field or transplanted to large containers (ca. 1m3 volume), with stem diameters up to 46 mm and leaf area per v...

  1. Estimating High Rates of Transpiration in Woody Vines with the Heat-Balance Method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat-balance sap flow gauges were configured to produce a more thermally uniform stem cross-section under high flow rates. On mature grapevines (Vitis labruscana) either undisturbed in the field or transplanted to large containers (ca. 1m^3 volume), with stem diameters up to 46 mm and leaf area per ...

  2. Localization of the Transpiration Barrier in the Epi- and Intracuticular Waxes of Eight Plant Species: Water Transport Resistances Are Associated with Fatty Acyl Rather Than Alicyclic Components.

    PubMed

    Jetter, Reinhard; Riederer, Markus

    2016-02-01

    Plant cuticular waxes play a crucial role in limiting nonstomatal water loss. The goal of this study was to localize the transpiration barrier within the layered structure of cuticles of eight selected plant species and to put its physiological function into context with the chemical composition of the intracuticular and epicuticular wax layers. Four plant species (Tetrastigma voinierianum, Oreopanax guatemalensis, Monstera deliciosa, and Schefflera elegantissima) contained only very-long-chain fatty acid (VLCFA) derivatives such as alcohols, alkyl esters, aldehydes, and alkanes in their waxes. Even though the epicuticular and intracuticular waxes of these species had very similar compositions, only the intracuticular wax was important for the transpiration barrier. In contrast, four other species (Citrus aurantium, Euonymus japonica, Clusia flava, and Garcinia spicata) had waxes containing VLCFA derivatives, together with high percentages of alicyclic compounds (triterpenoids, steroids, or tocopherols) largely restricted to the intracuticular wax layer. In these species, both the epicuticular and intracuticular waxes contributed equally to the cuticular transpiration barrier. We conclude that the cuticular transpiration barrier is primarily formed by the intracuticular wax but that the epicuticular wax layer may also contribute to it, depending on species-specific cuticle composition. The barrier is associated mainly with VLCFA derivatives and less (if at all) with alicyclic wax constituents. The sealing properties of the epicuticular and intracuticular layers were not correlated with other characteristics, such as the absolute wax amounts and thicknesses of these layers. PMID:26644508

  3. Modeling the water use efficiency of soybean and maize plants under environmental stresses: application of a synthetic model of photosynthesis-transpiration based on stomatal behavior.

    PubMed

    Yu, Gui-Rui; Wang, Qiu-Feng; Zhuang, Jie

    2004-03-01

    Understanding the variability of plant WUE and its control mechanism can promote the comprehension to the coupling relationship of water and carbon cycle in terrestrial ecosystem, which is the foundation for developing water-carbon coupling cycle model. In this paper, we made clear the differences of net assimilation rate, transpiration rate, and WUE between the two species by comparing the experiment data of soybean (Glycine max Merr.) and maize (Zea mays L.) plants under water and soil nutrient stresses. WUE of maize was about two and a half times more than that of soybean in the same weather conditions. Enhancement of water stresses led to the marked decrease of Am and Em of two species, but water stresses of some degree could improve WUE, and this effect was more obvious for soybean. WUE of the two species changed with psiL in a second-order curve relation, and the WUE at high fertilization was higher than that at low fertilization, this effect was especially obvious for maize. Moreover, according to the synthetic model of photosynthesis-transpiration based on stomatal behavior (SMPTSB) presented by Yu et al. (2001), the WUE model and its applicability were discussed with the data measured in this experiment. The WUE estimated by means of the model accorded well with the measured values. However, this model underestimated the WUE for maize slightly, thus further improvement on the original model was made in this study. Finally, by discussing some physiological factors controlling Am and WUE, we made clear the physiological explanation for differences of the relative contributions of stomata- and mesophyll processes to control of Am and WUE, and the applicability of WUE model between the two species. Because the requirement to stomatal conductance by unit change of net assimilation rate is different, the responses of opening-closing activity of stomata to environmental stresses are different between the two species. To obtain the same level of net assimilation

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    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.

  5. Wheat Transpiration Response to Soil Heterogeneity

    NASA Astrophysics Data System (ADS)

    Langensiepen, M.; Kupisch, M.; Cai, G.; Vanderborght, J.; Stadler, A.; Hüging, H.; Ewert, F.

    2014-12-01

    Measuring sap-flow in thin wheat tillers has been difficult so far due to technical difficulties associated with the application of the heat-balance method for this purpose. We developed a new method which solved this problem (Langensiepen et al. 2014) and applied it during four consecutive vegetation seasons for determining tiller transpiration rates in a wheat field with strong soil heterogeneity. The transpiration rates differed insignificantly between different field sections characterized by strong differences in physical soil conditions, regardless whether the crop was irrigated or supplied with variable rainwater. Tiller transpiration in a sheltered section was slightly reduced. Maximum leaf vapor conductance didn't differ among these different conditions, except under severe water stress conditions. Leaf water potential varied considerably during daily cycles under all circumstances. These responses are typical for plants with anisohydric behaviors which are characterized by small sensitivities of guard cells to critical leaf water potential thresholds and high photosynthetic productivity under absent or mild water stress. Recent studies conducted in Eucalyptus, tomato, and Arabidopsis plants have shown that the transition from mild to severe stress in anisohydric plants is marked by an increasing sensitivity of stomatal control to the transpiration rate. The results of this study demonstrate that this also seems to be the case for wheat. This practically implies that the parameterization of models calculating wheat canopy flux responses to soil heterogeneity patterns must not only account for the crop-type specific soil-vegetation pattern interaction under absent or mild stress, but also for additional mechanisms which kick in when water stress becomes severe. Langensiepen, M., Kupisch, M., Graf, A., Schmidt, M., Ewert, F. (2014) Improving the stem heat balance method for determining sap-flow in wheat. Agric. For. Met. 186: 34-42

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

    PubMed

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

    2013-09-01

    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 (D₂O) in lupin (Lupinus albus) roots. Lupins were grown in aluminum containers (30 × 25 × 1 cm) filled with sandy soil. D₂O 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 D₂O 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

  7. Effects of contrasting rooting distribution patterns on plant transpiration along a precipitation gradient

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding and predicting ecosystem functioning in water limited ecosystems requires a thorough assessment of the role plant root systems. Widespread ecological phenomena such as shrub encroachment may drastically change root distribution in the soil profile affecting the uptake of water and nutr...

  8. Using ISBA model for partitioning evapotranspiration into soil evaporation and plant transpiration of irrigated crops under semi-arid climate

    NASA Astrophysics Data System (ADS)

    Aouade, Ghizlane; Jarlan, Lionel; Ezzahar, Jamal; Er-raki, Salah; Napoly, Adrien; Benkaddour, Abdelfettah; Khabba, Said; Boulet, Gilles; Chehbouni, Abdelghani; Boone, Aaron

    2016-04-01

    The Haouz region, typical of southern Mediterranean basins, is characterized by a semi-arid climate, with average annual rainfall of 250, whilst evaporative demand is about 1600 mm per year. Under these conditions, crop irrigation is inevitable for growth and development. Irrigated agriculture currently consumes the majority of total available water (up to 85%), making it critical for more efficient water use. Flood irrigation is widely practiced by the majority of the farmers (more than 85 %) with an efficiency which does not exceed 50%. In this context, a good knowledge of the partitioning of evapotranspiration (ET) into soil evaporation and plant transpiration is of crucial need for improving the irrigation scheduling and thus water use efficiency. In this study, the ISBA (Interactions Soil-Biosphere-Atmosphere) model was used for estimating ET and its partition over an olive orchard and a wheat field located near to the Marrakech City (Centre of Morocco). Two versions were evaluated: standard version which simulates a single energy balance for the soil and vegetation and the recently developed multiple energy balance (MEB) version which solves a separate energy balance for each of the two sources. Eddy covariance system, which provides the sensible and latent heat fluxes and meteorological instruments were operated during years 2003-2004 for the Olive Orchard and during years 2013 for wheat. The transpiration component was measured using a Sap flow system during summer over the wheat crop and stable isotope samples were gathered over wheat. The comparison between ET estimated by ISBA model and that measured by the Eddy covariance system showed that MEB version yielded a remarkable improvement compared to the standard version. The root mean square error (RMSE) and the correlation coefficient (R²) were about 45wm-2 and 0.8 for MEB version. By contrast, for the standard version, the RMSE and R² were about 60wm-2 and 0.7, respectively. The result also showed that

  9. Control of transpiration by radiation.

    PubMed

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

    2010-07-27

    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

  10. Nutrient availability moderates transpiration in Ehrharta calycina.

    PubMed

    Cramer, Michael D; Hoffmann, Vera; Verboom, G Anthony

    2008-01-01

    Transpiration-driven 'mass-flow' of soil-water can increase nutrient flow to the root surface. Here it was investigated whether transpiration could be partially regulated by nutrient status. Seeds of Ehrharta calycina from nine sites across a rainfall gradient were supplied with slow-release fertilizer dibbled into the sand surrounding the roots and directly available through interception, mass-flow and diffusion (dubbed 'interception'), or sequestered behind a 40-microm mesh and not directly accessible by the roots, but from which nutrients could move by diffusion or mass-flow (dubbed 'mass-flow'). Although mass-flow plants were significantly smaller than interception plants as a consequence of nutrient limitation, they transpired 60% faster, had 90% higher photosynthesis relative to transpiration (A/E), and 40% higher tissue P, Ca and Na concentrations than plants allowed to intercept nutrients directly. Tissue N and K concentrations were similar for interception and mass-flow plants. Transpiration was thus higher in the nutrient-constrained 'mass-flow' plants, increasing the transport of nutrients to the roots by mass-flow. Transpiration may have been regulated by N availability, resulting in similar tissue concentration between treatments. It is concluded that, although transpiration is a necessary consequence of photosynthetic CO(2) uptake in C(3) plants, plants can respond to nutrient limitation by varying transpiration-driven mass-flow of nutrients. PMID:18537891

  11. Transpiration of urban forests in the Los Angeles metropolitan area.

    PubMed

    Pataki, Diane E; McCarthy, Heather R; Litvak, Elizaveta; Pincetl, Stephanie

    2011-04-01

    Despite its importance for urban planning, landscape management, and water management, there are very few in situ estimates of urban-forest transpiration. Because urban forests contain an unusual and diverse mix of species from many regions worldwide, we hypothesized that species composition would be a more important driver of spatial variability in urban-forest transpiration than meteorological variables in the Los Angeles (California, USA) region. We used constant-heat sap-flow sensors to monitor urban tree water use for 15 species at six locations throughout the Los Angeles metropolitan area. For many of these species no previous data on sap flux, water use, or water relations were available in the literature. To scale sap-flux measurements to whole trees we conducted a literature survey of radial trends in sap flux across multiple species and found consistent relationships for angiosperms vs. gymnosperms. We applied this relationship to our measurements and estimated whole-tree and plot-level transpiration at our sites. The results supported very large species differences in transpiration, with estimates ranging from 3.2 +/- 2.3 kg x tree(-1) x d(-1) in unirrigated Pinus canariensis (Canary Island pine) to 176.9 +/- 75.2 kg x tree(-1) x d(-1) in Platanus hybrida (London planetree) in the month of August. Other species with high daily transpiration rates included Ficus microcarpa (laurel fig), Gleditsia triacanthos (honeylocust), and Platanus racemosa (California sycamore). Despite irrigation and relatively large tree size, Brachychiton populneas (kurrajong), B. discolor (lacebark), Sequoia sempervirens (redwood), and Eucalyptus grandis (grand Eucalyptus) showed relatively low rates of transpiration, with values < 45 kg x tree(-1) x d(-1). When scaled to the plot level, transpiration rates were as high as 2 mm/d for sites that contained both species with high transpiration rates and high densities of planted trees. Because plot-level transpiration is highly

  12. Maize transpiration in response to meteorological conditions

    NASA Astrophysics Data System (ADS)

    Klimešová, Jana; Stŕedová, Hana; Stŕeda, Tomáš

    2013-09-01

    Differences in transpiration of maize (Zea mays L.) plants in four soil moisture regimes were quantified in a pot experiment. The transpiration was measured by the "Stem Heat Balance" method. The dependence of transpiration on air temperature, air humidity, global solar radiation, soil moisture, wind speed and leaf surface temperature were quantified. Significant relationships among transpiration, global radiation and air temperature (in the first vegetation period in the drought non-stressed variant, r = 0.881**, r = 0.934**) were found. Conclusive dependence of transpiration on leaf temperature (r = 0.820**) and wind speed (r = 0.710**) was found. Transpiration was significantly influenced by soil moisture (r = 0.395**, r = 0.528**) under moderate and severe drought stress. The dependence of transpiration on meteorological factors decreased with increasing deficiency of water. Correlation between transpiration and plant dry matter weight (r = 0.997**), plant height (r = 0.973**) and weight of corn cob (r = 0.987**) was found. The results of instrumental measuring of field crops transpiration under diverse moisture conditions at a concurrent monitoring of the meteorological elements spectra are rather unique. These results will be utilized in the effort to make calculations of the evapotranspiration in computing models more accurate.

  13. Steady state or non-steady state? Identifying driving mechanisms of oxygen isotope signatures of leaf transpiration in functionally distinct plant species

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Kübert, Angelika; Cuntz, Matthias; Werner, Christiane

    2015-04-01

    Isotope techniques are widely applied in ecosystem studies. For example, isoflux models are used to separate soil evaporation from transpiration in ecosystems. These models often assume that plant transpiration occurs at isotopic steady state, i.e. that the transpired water shows the same isotopic signature as the source water. Yet, several studies found that transpiration did not occur at isotopic steady state, under both controlled and field conditions. Here we focused on identifying the internal and external factors which drive the isotopic signature of leaf transpiration. Using cavity ring-down spectroscopy (CRDS), the effect of both environmental variables and leaf physiological traits on δ18OT was investigated under controlled conditions. Six plant species with distinct leaf physiological traits were exposed to step changes in relative air humidity (RH), their response in δ18OT and gas exchange parameters and their leaf physiological traits were assessed. Moreover, two functionally distinct plant types (tree, i.e. Quercus suber, and grassland) of a semi-arid Mediterranean oak-woodland where observed under natural conditions throughout an entire growth period in the field. The species differed substantially in their leaf physiological traits and their turn-over times of leaf water. They could be grouped in species with fast (<60 min.), intermediate (ca. 120 min.) and slow (>240 min.) turn-over times, mostly due to differences in stomatal conductance, leaf water content or a combination of both. Changes in RH caused an immediate response in δ18OT, which were similarly strong in all species, while leaf physiological traits affected the subsequent response in δ18OT. The turn-over time of leaf water determined the speed of return to the isotopic steady or a stable δ18OT value (Dubbert & Kübert et al., in prep.). Under natural conditions, changes in environmental conditions over the diurnal cycle had a huge impact on the diurnal development of δ18OT in both

  14. Transpiration- and growth-induced water potentials in maize

    SciTech Connect

    Westgate, M.E.; Boyer, J.S.

    1984-01-01

    Recent evidence from leaves and stems indicates that gradients in water potential (psi/sub w/) necessary for water movement through growing tissues are larger than previously assumed. Because growth is sensitive to tissue psi/sub w/ and the behavior of these gradients has not been investigated in transpiring plants, the authors examined the water status of all the growing and mature vegetative tissues of maize (Zea mays L.) during high and low rates of transpiration. The psi/sub w/ measured in the mature regions of the plant responded primarily to transpiration, while the psi/sub w/ in the growing regions was affected both by transpiration and growth. The transpiration-induced potentials of the mature tissue formed a gradient of decreasing psi/sub w/ along the transpiration stream while the growth-induced potentials formed a gradient of decreasing psi/sub w/ from the transpiration stream to the expanding cells in the growing tissue. The growth-induced gradient in psi/sub w/ within the leaf remained fairly constant as the xylem psi/sub w/ decreased during the day and was associated with a decreased osmotic potential (psi/sub s/) of the growing region (osmotic adjustment). The growth-induced gradient in psi/sub w/ was not caused by excision of the tissue because intact maize stems exhibited a similar psi/sub w/. These observations support the concept that large gradients in psi/sub w/ are required to maintain water flow to expanding cells within all the vegetative tissues and suggest that the maintenance of a favorable gradient in psi/sub w/ for cell enlargement may be an important role for osmotic adjustment. 33 references, 7 figures, 1 table.

  15. Effects of Planting Density on Transpiration, Stem Flow and Interception for Two Clones Differing in Drought Tolerance in a High Productivity Eucalyptus Plantation in Brazil

    NASA Astrophysics Data System (ADS)

    Hubbard, R. M.; Hakemada, R.; Ferraz, S.

    2015-12-01

    Eucalypt plantations cover about 20 M hectares worldwide and expansion is expected to mainly occur in marginal growing areas where dry conditions may lead to water conflicts. One of the principal reasons for the expansion of Eucalyptus plantations is rapid wood growth but these forests also transpire large amounts of water. Genotype selection and planting density, are key factors regulating carbon and water tradeoffs at a stand scale, but few studies have examined these simultaneously especially in highly productive clonal plantations. Our goal in this study was to examine the effects of planting density on carbon and water interactions using a drought tolerant and drought sensitive eucalyptus clone. This work is part of a larger study (TECHS project - Tolerance of Eucalyptus Clones to Hydric and Thermal Stresses) and is located in a flat Oxisol in southeast of Brazil. A drought tolerant (E. grandis x E. camaldulensis (Grancam) and drought sensitive clone E. grandis x E. urophylla (Urograndis) were planted at four densities ranging from 600 to 3.000 stem ha-1. We measured transpiration using thermal heat dissipation probes, wood growth, canopy interception and stemflow during a full year (21 to 33 months old). Precipitation during the study period was 738 mm. Independently of genetics, growth increased with increasing density. Transpiration also increased with planting density and ranged from 515-595 mm at wider spacing to 735-978 mm at tighter spacing. Interception increased with planting density representing 18-22% of precipitation versus 13-14% in wider spacing while stem flow represented 2-5% in denser spacing and 1-2% at broader spacing. When density was higher than 1.250 and 1.750 stems ha-1 in Urograndis and Grancam clones, respectively, the water balance were negative. On a stand scale, results show both genetics and spacing can be used as silvicultural tools to better manage the tradeoff between wood growth and water consumption.

  16. Transpiration cooling using air as a coolant

    SciTech Connect

    Kikkawa, Shinzo; Senda, Mamoru; Sakagushi, Katsuji; Shibutani, Hideki )

    1993-02-01

    Transpiration cooling is one of the most effective techniques for protecting a surface exposed to a high-temperature gas stream. In the present paper, the transpiration cooling effectiveness was measured under steady state. Air as a coolant was transpired from the surface of a porous plate exposed to hot gas stream, and the transpiration rate was varied in the range of 0.001 [approximately] 0.006. The transpiration cooling effectiveness was evaluated by measuring the temperature of the upper surface of the plate. Also, a theoretical study was performed and it was clarified that the effectiveness increases with increasing transpiration rate and heat-transfer coefficient of the upper surface. Further, the effectiveness was expressed as a function of the blowing parameter only. The agreement between the experimental results and theoretical ones was satisfactory.

  17. Transpiration cooled throat for hydrocarbon rocket engines

    NASA Technical Reports Server (NTRS)

    May, Lee R.; Burkhardt, Wendel M.

    1991-01-01

    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.

  18. Fruit load governs transpiration of olive trees.

    PubMed

    Bustan, Amnon; Dag, Arnon; Yermiyahu, Uri; Erel, Ran; Presnov, Eugene; Agam, Nurit; Kool, Dilia; Iwema, Joost; Zipori, Isaac; Ben-Gal, Alon

    2016-03-01

    We tested the hypothesis that whole-tree water consumption of olives (Olea europaea L.) is fruit load-dependent and investigated the driving physiological mechanisms. Fruit load was manipulated in mature olives grown in weighing-drainage lysimeters. Fruit was thinned or entirely removed from trees at three separate stages of growth: early, mid and late in the season. Tree-scale transpiration, calculated from lysimeter water balance, was found to be a function of fruit load, canopy size and weather conditions. Fruit removal caused an immediate decline in water consumption, measured as whole-plant transpiration normalized to tree size, which persisted until the end of the season. The later the execution of fruit removal, the greater was the response. The amount of water transpired by a fruit-loaded tree was found to be roughly 30% greater than that of an equivalent low- or nonyielding tree. The tree-scale response to fruit was reflected in stem water potential but was not mirrored in leaf-scale physiological measurements of stomatal conductance or photosynthesis. Trees with low or no fruit load had higher vegetative growth rates. However, no significant difference was observed in the overall aboveground dry biomass among groups, when fruit was included. This case, where carbon sources and sinks were both not limiting, suggests that the role of fruit on water consumption involves signaling and alterations in hydraulic properties of vascular tissues and tree organs. PMID:26802540

  19. Near-optimal response of instantaneous transpiration efficiency to vapour pressure deficit, temperature and [CO2] in cotton (Gossypium hirsutum L.).

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The instantaneous transpiration efficiency (ITE, the ratio of photosynthesis rate to transpiration) is an important variable for crops, because it ultimately affects dry mass production per unit of plant water lost to the atmosphere. The theory that stomata optimize carbon uptake per unit water used...

  20. Estimation of Soil Evaporation and Plant Transpiration of Sparse Steppes by Using Ground-based Infrared Thermal Images

    NASA Astrophysics Data System (ADS)

    Qiu, G. Y.; Feng, Y.

    2011-12-01

    Separately estimation of soil evaporation (E) and vegetation transpiration (T) is important for water management. In this study, a methodology to estimate the ratio of vegetation cover, soil evaporation and vegetation transpiration in a sparse steppe is developed based on a previous published model, the three-temperatures (3T) model. The input parameters of the model includes the surface temperatures of soil and vegetation (from thermal image), net radiation (estimated from surface temperature and solar radiation), and air temperature. The approach of unsupervised classification was used to separate the bare soil and vegetation pixels from the images. The areas with higher temperature could be regarded as the bare soil and E was estimated by the evaporation sub-model in the 3T model; while the areas with lower temperature could be regarded as pure vegetation and T was estimated by the transpiration sub-model in the 3T model. Afterward, the estimated E and T were converted into daily values and compared with the measured E and T by using Bowen Ratio and micro-lysimeter methods. Results show that the proposed approach is a useful way to separately estimated E and T in sparse steppe.

  1. Comparison of corn transpiration, eddy covariance, and soil water loss

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stem flow gages are used to estimate plant transpiration, but only a few studies compare transpiration with other measures of soil water loss. The purpose of this study was to compare transpiration from stem flow measurements with soil water changes estimated by daily neutron probe readings. Monitor...

  2. The function of nocturnal transpiration

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  3. Combining field performance with controlled environment plant imaging to identify the genetic control of growth and transpiration underlying yield response to water-deficit stress in wheat

    PubMed Central

    Parent, Boris; Shahinnia, Fahimeh; Maphosa, Lance; Berger, Bettina; Rabie, Huwaida; Chalmers, Ken; Kovalchuk, Alex; Langridge, Peter; Fleury, Delphine

    2015-01-01

    Crop yield in low-rainfall environments is a complex trait under multigenic control that shows significant genotype×environment (G×E) interaction. One way to understand and track this trait is to link physiological studies to genetics by using imaging platforms to phenotype large segregating populations. A wheat population developed from parental lines contrasting in their mechanisms of yield maintenance under water deficit was studied in both an imaging platform and in the field. We combined phenotyping methods in a common analysis pipeline to estimate biomass and leaf area from images and then inferred growth and relative growth rate, transpiration, and water-use efficiency, and applied these to genetic analysis. From the 20 quantitative trait loci (QTLs) found for several traits in the platform, some showed strong effects, accounting for between 26 and 43% of the variation on chromosomes 1A and 1B, indicating that the G×E interaction could be reduced in a controlled environment and by using dynamic variables. Co-location of QTLs identified in the platform and in the field showed a possible common genetic basis at some loci. Co-located QTLs were found for average growth rate, leaf expansion rate, transpiration rate, and water-use efficiency from the platform with yield, spike number, grain weight, grain number, and harvest index in the field. These results demonstrated that imaging platforms are a suitable alternative to field-based screening and may be used to phenotype recombinant lines for positional cloning. PMID:26179580

  4. Uncertainty in sap flow-based transpiration due to xylem properties

    NASA Astrophysics Data System (ADS)

    Looker, N. T.; Hu, J.; Martin, J. T.; Jencso, K. G.

    2014-12-01

    Transpiration, the evaporative loss of water from plants through their stomata, is a key component of the terrestrial water balance, influencing streamflow as well as regional convective systems. From a plant physiological perspective, transpiration is both a means of avoiding destructive leaf temperatures through evaporative cooling and a consequence of water loss through stomatal uptake of carbon dioxide. Despite its hydrologic and ecological significance, transpiration remains a notoriously challenging process to measure in heterogeneous landscapes. Sap flow methods, which estimate transpiration by tracking the velocity of a heat pulse emitted into the tree sap stream, have proven effective for relating transpiration dynamics to climatic variables. To scale sap flow-based transpiration from the measured domain (often <5 cm of tree cross-sectional area) to the whole-tree level, researchers generally assume constancy of scale factors (e.g., wood thermal diffusivity (k), radial and azimuthal distributions of sap velocity, and conducting sapwood area (As)) through time, across space, and within species. For the widely used heat-ratio sap flow method (HRM), we assessed the sensitivity of transpiration estimates to uncertainty in k (a function of wood moisture content and density) and As. A sensitivity analysis informed by distributions of wood moisture content, wood density and As sampled across a gradient of water availability indicates that uncertainty in these variables can impart substantial error when scaling sap flow measurements to the whole tree. For species with variable wood properties, the application of the HRM assuming a spatially constant k or As may systematically over- or underestimate whole-tree transpiration rates, resulting in compounded error in ecosystem-scale estimates of transpiration.

  5. Effects of overcast and foggy conditions on transpiration rates of Pinus patula trees along a chronosequence within the cloud belt of the Sierra Madre Oriental, central Veracruz, Mexico

    NASA Astrophysics Data System (ADS)

    Alvarado-Barrientos, M. S.; Holwerda, F.; Asbjornsen, H.; Sauer, T.; Dawson, T. E.; Bruijnzeel, L. A.

    2010-12-01

    Pinus patula is a native tree species of the montane cloud belt of central Veracruz, Mexico, and one of the most popular species for regional reforestation efforts, both within and outside its natural range of occurrence. Projected regional climate change is likely to cause a rise in the average cloud condensation level by several hundred meters, thereby reducing fog occurrence, whilst overcast conditions are likely to remain similar. To improve our understanding of how water use of P. patula plantations is affected by changes in climatic conditions, we analyzed the response of transpiration rates to fine-scale variations in microclimate, particularly fog immersion and the occurrence of high clouds. We conducted measurements of micrometeorological parameters and transpiration (Et, using the heat ratio sap flow technique) of 15 pine trees representing a range of ages (10-34 years) and sizes (7-60 cm of dbh) during one and a half years (Nov 2008 - May 2010), covering two dry seasons and one wet season. Foggy days were defined using daytime “M-of-N” constructs (at least 4 hours with visibility <1000 m within 6 consecutive hourly observations), and days with overcast conditions as having a median daytime visibility > 1000 m and a maximum incoming solar radiation (Sin) < 700 W m-2. Precipitation and leaf wetness data were used to distinguish between (partly) wet and dry canopy conditions. Daily transpiration rates were normalized for climatic conditions using the FAO reference evaporation ETo to allow determination of the proportional contributions to Et suppression by reductions in Sin and VPD relative to leaf wetness. We found that both foggy and overcast conditions without rainfall produced similar % of Et reduction compared to sunny conditions (60-70%). The strongest Et suppression effects occurred when foggy or overcast conditions were associated with rainfall. However, there was just a slight and non significant difference between the average Et/ETo ratio for

  6. Continuous Measurement of Macronutrient Ions in the Transpiration Stream of Intact Plants Using the Meadow Spittlebug Coupled with Ion Chromatography1

    PubMed Central

    Malone, Michael; Herron, Michelle; Morales, M.-Angeles

    2002-01-01

    A method is described for continuous, nondestructive analysis of xylem-borne mineral nutrients in intact transpiring plants. The method uses the xylem-feeding insect the meadow spittlebug (Philaenus spumarius L. [Homoptera: Cercopidae]). This insect will feed from a wide range of plant species and organs. Insect excreta can be collected at all times of the day and night, and its mineral ion content can be analyzed rapidly, and without purification, by ion chromatography. The excreta will have a mineral content virtually identical to that of xylem sap. Cages suitable for containing the insects and collecting excreta from any desired location on plants in both laboratory and greenhouse are described. Even in the greenhouse, evaporation had only a minor effect on the sample ion content. Example results are presented which illustrate dynamics, over several days, in the xylem concentrations of sodium (Na+), potassium (K+), NH4+, magnesium (Mg2+), calcium (Ca2+), chloride (Cl−), NO3−, PO43−, and SO42−. These data were collected from young plants growing in pots of compost in the laboratory and from fully mature pepper (Capsicum annuum L. cv Bellboy) plants growing in hydroponics (rockwool) in the greenhouse. This method should facilitate studies of macronutrient uptake and transport in a range of plants and environments. PMID:12428008

  7. 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)

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

    2012-12-01

    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

  8. Seasonal, synoptic and diurnal variation of atmospheric water-isotopologues in the boundary layer of Southwestern Germany caused by plant transpiration, cold-front passages and dewfall.

    NASA Astrophysics Data System (ADS)

    Christner, Emanuel; Dyroff, Christoph; Kohler, Martin; Zahn, Andreas; Gonzales, Yenny; Schneider, Matthias

    2013-04-01

    Atmospheric water is an enormously crucial trace gas. It is responsible for ~70 % of the natural greenhouse effect (Schmidt et al., JGR, 2010) and carries huge amounts of latent heat. The isotopic composition of water vapor is an elegant tracer for a better understanding and quantification of the extremely complex and variable hydrological cycle in Earth's atmosphere (evaporation, cloud condensation, rainout, re-evaporation, snow), which in turn is a prerequisite to improve climate modeling and predictions. As H216O, H218O and HDO differ in vapor pressure and mass, isotope fractionation occurs due to condensation, evaporation and diffusion processes. In contrast to that, plants are able to transpire water with almost no isotope fractionation. For that reason the ratio of isotopologue concentrations in the boundary layer (BL) provides, compared to humidity measurements alone, independent and additional constraints for quantifying the strength of evaporation and transpiration. Furthermore the isotope ratios contain information about transport history of an air mass and microphysical processes, that is not accessible by humidity measurements. Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) a commercial Picarro Analyzer L2120-i is operated at Karlsruhe in Southwestern Germany, which is continuously measuring the isotopologues H216O, HDO and H218O of atmospheric water vapor since January 2012. A one year record of H216O, HDO and H218O shows clear seasonal, synoptic and diurnal characteristics and reveals the main driving processes affecting the isotopic composition of water vapor in the Middle European BL. Changes in continental plant transpiration and evaporation throughout the year lead to a slow seasonal HDO/H216O-variation, that cannot be explained by pure Rayleigh condensation. Furthermore, cold-front passages from NW lead to fast and pronounced depletion of the HDO/H216O-ratio within

  9. Terrestrial water fluxes dominated by transpiration.

    PubMed

    Jasechko, Scott; Sharp, Zachary D; Gibson, John J; Birks, S Jean; Yi, Yi; Fawcett, Peter J

    2013-04-18

    Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km(3) per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth's continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km(3) of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes. PMID:23552893

  10. Interspecies comparison of transpiration in Cambodia for the prediction of water use under the tropical monsoon climate

    NASA Astrophysics Data System (ADS)

    Tateishi, Makiko; Miyazawa, Yoshiyuki; Tomo'Omi, Kumagai; Ma, Vuthy; Sokh, Heng; Mizoue, Nobuya

    2010-05-01

    Recently exotic fast-growing trees are planted in Southeast Asia, since economical profits of fast-growing tree plantations are expected. However, fast-growing species are also thought to consume more water than native species. There is concern these exotic species may influence water resources because of their large water consumption, especially during the dry season. In Cambodia there is a clear rainy season and extremely dry season with hardly any rainfall. Whether fast-growing trees adapt to such dry season and their effect on water resources is unconcern. To evaluate the impact of planting exotic trees, it is critical to know how much water these trees transpired and how they control water use under drought condition. To more thoroughly understand these processes, water flow was monitored in the stem of 4 species continuously using sap flux measurement to estimate transpiration of individual trees. For this experiment, we selected 6 trees of each species; two native species (Dipterocarpus obtusifolius and Shorea roxburghii) and 2 exotic species (Acacia auriculiformis and Eucalyptus camaldulensis). Meteorological observations were also conducted. All species had similar transpiration rates under the same environmental condition in the rainy season. Although there was a relationship between tree size and transpiration, difference among the tree species was not clear. That is to say, the difference of transpiration between small size trees and large trees was larger than interspecies variation in that period. From long-term observations, we found that transpiration of native and exotic species in the dry season show different responses to environmental conditions. While transpiration of A. auriculiformis slightly decreased during the dry season, the transpiration rate of S. roxburghii, a native species, remained high despite diminished groundwater at the end of the dry season. This result implies S. roxburghii develops deeper roots to access groundwater for

  11. Simple relations for different stomatal control mechanisms link partially drying soil and transpiration

    NASA Astrophysics Data System (ADS)

    Huber, Katrin; Vanderborght, Jan; Javaux, Mathieu; Vereecken, Harry

    2015-04-01

    Stomata can close to regulate plant water loss under unfavourable water availability. This closure can be triggered by hydraulic ('H') and/or chemical signals ('C', 'H+C'). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive a simple relation that links soil water availability, expressed as the fraction of roots in dry soil, to transpiration. We used the detailed mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontally and vertically split domains with varying fractions of roots in dry soil and comparing different strengths of stomatal regulation by chemical and hydraulic signals. Transpiration predicted by the relation was in good agreement with numerical simulations. Under certain conditions H+C control leads to isohydric plant behaviour, which means that stomata close to keep leaf water potential constant after reaching a certain level. C control on the other hand exerts anisohydric behaviour, meaning that stomata remain fully open during changes in leaf water potential. For C control the relation between transpiration reduction and fraction of roots in dry soil becomes independent of transpiration rate whereas H+C control results in stronger reduction for higher transpiration rates. Simple relations that link effective soil and leaf water potential can describe different stomatal control resulting in contrasting behaviour.

  12. Localization of the Transpiration Barrier in the Epi- and Intracuticular Waxes of Eight Plant Species: Water Transport Resistances Are Associated with Fatty Acyl Rather Than Alicyclic Components1[OPEN

    PubMed Central

    Jetter, Reinhard

    2016-01-01

    Plant cuticular waxes play a crucial role in limiting nonstomatal water loss. The goal of this study was to localize the transpiration barrier within the layered structure of cuticles of eight selected plant species and to put its physiological function into context with the chemical composition of the intracuticular and epicuticular wax layers. Four plant species (Tetrastigma voinierianum, Oreopanax guatemalensis, Monstera deliciosa, and Schefflera elegantissima) contained only very-long-chain fatty acid (VLCFA) derivatives such as alcohols, alkyl esters, aldehydes, and alkanes in their waxes. Even though the epicuticular and intracuticular waxes of these species had very similar compositions, only the intracuticular wax was important for the transpiration barrier. In contrast, four other species (Citrus aurantium, Euonymus japonica, Clusia flava, and Garcinia spicata) had waxes containing VLCFA derivatives, together with high percentages of alicyclic compounds (triterpenoids, steroids, or tocopherols) largely restricted to the intracuticular wax layer. In these species, both the epicuticular and intracuticular waxes contributed equally to the cuticular transpiration barrier. We conclude that the cuticular transpiration barrier is primarily formed by the intracuticular wax but that the epicuticular wax layer may also contribute to it, depending on species-specific cuticle composition. The barrier is associated mainly with VLCFA derivatives and less (if at all) with alicyclic wax constituents. The sealing properties of the epicuticular and intracuticular layers were not correlated with other characteristics, such as the absolute wax amounts and thicknesses of these layers. PMID:26644508

  13. Stem girdling evidences a trade-off between cambial activity and sprouting and dramatically reduces plant transpiration due to feedback inhibition of photosynthesis and hormone signaling

    PubMed Central

    López, Rosana; Brossa, Ricard; Gil, Luis; Pita, Pilar

    2015-01-01

    The photosynthesis source–sink relationship in young Pinus canariensis seedlings was modified by stem girdling to investigate sprouting and cambial activity, feedback inhibition of photosynthesis, and stem and root hydraulic capacity. Removal of bark tissue showed a trade-off between sprouting and diameter growth. Above the girdle, growth was accelerated but the number of sprouts was almost negligible, whereas below the girdle the response was reversed. Girdling resulted in a sharp decrease in whole plant transpiration and root hydraulic conductance. The reduction of leaf area after girdling was strengthened by the high levels of abscisic acid found in buds which pointed to stronger bud dormancy, preventing a new needle flush. Accumulation of sugars in leaves led to a coordinated reduction in net photosynthesis (AN) and stomatal conductance (gS) in the short term, but later (gS below 0.07 mol m-2 s-1) AN decreased faster. The decrease in maximal efficiency of photosystem II (FV/FM) and the operating quantum efficiency of photosystem II (ΦPSII) in girdled plants could suggest photoprotection of leaves, as shown by the vigorous recovery of AN and ΦPSII after reconnection of the phloem. Stem girdling did not affect xylem embolism but increased stem hydraulic conductance above the girdle. This study shows that stem girdling affects not only the carbon balance, but also the water status of the plant. PMID:25972884

  14. Compensating effect of sap velocity for stand density leads to uniform hillslope-scale forest transpiration across a steep valley cross-section

    NASA Astrophysics Data System (ADS)

    Renner, Maik; Hassler, Sibylle; Blume, Theresa; Weiler, Markus; Hildebrandt, Anke; Guderle, Marcus; Schymanski, Stan; Kleidon, Axel

    2016-04-01

    Roberts (1983) found that forest transpiration is relatively uniform across different climatic conditions and suggested that forest transpiration is a conservative process compensating for environmental heterogeneity. Here we test this hypothesis at a steep valley cross-section composed of European Beech in the Attert basin in Luxemburg. We use sapflow, soil moisture, biometric and meteorological data from 6 sites along a transect to estimate site scale transpiration rates. Despite opposing hillslope orientation, different slope angles and forest stand structures, we estimated relatively similar transpiration responses to atmospheric demand and seasonal transpiration totals. This similarity is related to a negative correlation between sap velocity and site-average sapwood area. At the south facing sites with an old, even-aged stand structure and closed canopy layer, we observe significantly lower sap velocities but similar stand-average transpiration rates compared to the north-facing sites with open canopy structure, tall dominant trees and dense understorey. This suggests that plant hydraulic co-ordination allows for flexible responses to environmental conditions leading to similar transpiration rates close to the water and energy limits despite the apparent heterogeneity in exposition, stand density and soil moisture. References Roberts, J. (1983). Forest transpiration: A conservative hydrological process? Journal of Hydrology 66, 133-141.

  15. 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

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

    2009-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  17. Numerical Analysis of Convection/Transpiration Cooling

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  18. Numerical Analysis of Convection/Transpiration Cooling

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  19. Correlation of thermophoretically-modified small particle diffusional deposition rates in forced convection systems with variable properties, transpiration cooling and/or viscous dissipation

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Rosner, D. E.

    1984-01-01

    A cooled object (heat exchanger tube or turbine blade) is considered to be immersed in a hot fluid stream containing trace amounts of suspended vapors and/or small particles. Numerical prediction calculations were done for self-similar laminar boundary layers and law-of-the-wall turbulent boundary layers. Correlations are presented for the effect of thermophoresis in the absence of transpiration cooling and viscous dissipation; the effect of real suction and blowing in the absence of thermophoresis; the effect of viscous dissipation on thermophoresis in the absence of transpiration cooling; and the combined effect of viscous dissipation and transpiration cooling on thermophoresis. The final correlation, St/St-sub-zero, is insensitive to particle properties, Euler number, and local mainstream temperature.

  20. 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 ...

  1. Transpiration and CO/sub 2/ fixation of selected desert shrubs as related to soil-water potential

    SciTech Connect

    Clark, S.B.; Letey, J. Jr.; Lunt, O.R.; Wallace, A.; Kleinkopf, G.E.; Romney, E.M.

    1980-01-01

    In desert plants, transpiration rates decreased before photosynthetic rates when plants were entering a period of water stress. This may have adaptive consequences. A difference of -5 bars in the soil-moisture potential had considerable importance in reducing the rate of transpiration. In Helianthus annuus L. (sunflower) the photosynthetic rate decreased before the transpiration rate in contrast to Great Basin-Mojave Desert plants, and the changes occurred with a -1 bar difference in soil-moisture potential. Morphological changes in three desert plant species (Artemisia tridentata Nutt., Ambrosia dumosa (Gray) Payne, Larrea tridentata (Ses. Moc. ex DC) Cov.) as the soil-moisture potential decreased are given. With a mesic species, H. annuus, 20% reduction in photosynthesis and transpiration was reached at higher soil-moisture potentials than with the desert plants. Loss of net photosynthesis occurred in A. dumosa (a summer deciduous shrub) as PSI soil reached -48 bars in the field, whereas L. tridentata (an evergreen shrub) at the same time was able to maintain a water potential difference between soil and plant of -10 to -15 bars and continue net CO/sub 2/ gain well into the summer months.

  2. Fruit transpiration in kiwifruit: environmental drivers and predictive model

    PubMed Central

    Montanaro, Giuseppe; Dichio, Bartolomeo; Xiloyannis, Cristos; Lang, Alexander

    2012-01-01

    Background and aims In most fruit crops, storage quality varies greatly between regions and seasons, causing significant commercial loss. Understanding the sources of this variability will contribute to the knowledge of fruit developmental physiology and may also benefit commercial fruit production via altered managements that reduce it or forecasts that predict it. A causal-chain relationship is proposed to help elucidate the sources of variability in fruit storage quality: the weather →(i)→ fruit transpiration →(ii)→ fruit calcium →(iii)→ fruit storage quality. This paper explores the first link of this hypothesis, →(i)→, for Hayward kiwifruit using field measurements of fruit transpiration rate and concurrent meteorological recordings. The aims are to identify the key environmental variables driving fruit transpiration and develop a predictive fruit transpiration model. Methodology Fruit transpiration was determined hourly over several 24-h periods by recording weight loss of detached fruit, on Days 23, 35, 49, 65, 94 and 140 after full bloom. Meteorological records were made every 15 min throughout the season at an adjacent regional weather station. A model of fruit transpiration was developed in which the usual meteorological variables (radiation, temperature, windspeed and relative humidity) were incorporated in a Fick's Law transpiration flux equation. Principal results Fruit transpiration rate (i.e. the molar flux density, mmol cm−2 h−1) varied diurnally and decreased during the season. The dominant fruit variable governing transpiration rate was skin conductance and the dominant environmental variables were relative humidity and temperature. Radiation and windspeed were not significantly influential. Conclusions The model provides a good fit to the fruit transpiration rate measurements regardless of the time of day/night or the stage of fruit development. The model allows reasonably accurate and continuous predictions of fruit

  3. Deposition control using transpiration: Final report

    SciTech Connect

    Kozlu, H.; Louis, J.F.

    1986-11-01

    An experimental and theoretical study of deposition of small particles is presented to evaluate the concept of transpiration as a deposition control strategy. The application of this work is the control of the deposition of small particles (0.5 to 3 ..mu..m) in turbines burning fuels derived from coal. The study is carried out in a wind tunnel facility containing a flat porous transpired section. Similar flows and particle motions are achieved by choosing the proper Reynolds and Stokes numbers representative of the conditions found in industrial gas turbines. Measurements of the velocity profiles were conducted for high injection rates (1.5% < F < 3%). A theory developed for the transpired turbulent boundary layer, which is described by an ''outer boundary layer'' entraining the transpired flow for large injection rates, agrees well with the experimental data. Concentration profiles of glass particles of both very narrow and wide size distributions were conducted for different injection rates under isothermal conditions. The measurements indicate clearly the conditions under which transpiration can prevent the deposition of particles and they show the effect of particle size. The interaction between transpiration and the inertial impaction of particulates is determined in an experimental set-up using an identical inclined transpired plate. Using the experimental data, the effect of the density of particles on concentration profiles is predicted. Present study also provides a clear insight into the turbulent diffusion of particles for a Stokes number of between 1 and 3.5 (and a turbulent Schmidt number range of 2 to 6). The turbulent Schmidt numbers obtained from the measurements are in agreement with the theoretical prediction of Tchen. 26 refs., 25 figs.

  4. 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)

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

    2013-04-01

    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.

  5. Interannual Variation in Stand Transpiration is Dependent Upon Tree Species

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    In order to successfully predict transpirational water fluxes from forested watersheds, interannual variability in transpiration must be quantified and understood. In a heterogeneous forested landscape in northern Wisconsin, we quantified stand transpiration across four forest cover types representing more than 80 percent of the land area in order to 1) quantify differences in stand transpiration and leaf area over two years and 2) determine the mechanisms governing the changes in transpiration over two years. We measured sap flux in eight trees of each tree species in the four cover types. We found that in northern hardwoods, the leaf area of sugar maple increased between the two measurement years with transpiration per unit ground area increasing even more than could be explained by leaf area. In an aspen stand, tent caterpillars completely defoliated the stand for approximately a month until a new set of leaves flushed out. The new set of leaves resulted in a lower leaf area but the same transpiration per unit leaf area indicating there was no physiological compensation for the lower leaf area. At the same time, balsam fir growing underneath the aspen increased their transpiration rate in response to greater light penetration through the dominant aspen canopy Red pine had a thirty percent change in leaf area within a growing season due to multiple cohorts of leaves and transpiration followed this leaf area dynamic. In a forested wetland, white cedar transpiration was proportional to surface water depth between the two years. Despite the specific tree species' effects on stand transpiration, all species displayed a minimum water potential regulation resulting in a saturating response of transpiration to vapor pressure deficit that did not vary across the two years. This physiological set point will allow future water flux models to explain mechanistically interannual variability in transpiration of this and similar forests.

  6. Connections between groundwater flow and transpiration partitioning.

    PubMed

    Maxwell, Reed M; Condon, Laura E

    2016-07-22

    Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes. PMID:27463671

  7. Connections between groundwater flow and transpiration partitioning

    NASA Astrophysics Data System (ADS)

    Maxwell, Reed M.; Condon, Laura E.

    2016-07-01

    Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes.

  8. Transpiration and yield relationships of grain sorghum grown in a field environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of plants to convert transpiration into dry matter has been studied since the early 20th century. Research has compared differences among species using transpiration efficiency (TE), the ratio of biomass yield (Yb) to transpiration (T); and m and k, which are the slopes of the linear Yb...

  9. Transpiration purged optical probe

    DOEpatents

    VanOsdol, John; Woodruff, Steven

    2004-01-06

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  11. Transpiration Control Of Aerodynamics Via Porous Surfaces

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Quasi-active porous surface used to control pressure loading on aerodynamic surface of aircraft or other vehicle, according to proposal. In transpiration control, one makes small additions of pressure and/or mass to cavity beneath surface of porous skin on aerodynamic surface, thereby affecting rate of transpiration through porous surface. Porous skin located on forebody or any other suitable aerodynamic surface, with cavity just below surface. Device based on concept extremely lightweight, mechanically simple, occupies little volume in vehicle, and extremely adaptable.

  12. 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

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

    1995-01-01

    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. PMID:12228364

  13. Evapotranspiration crop coefficients for mixed riparian plant community and transpiration crop coefficients for Common reed, Cottonwood and Peach-leaf willow in the Platte River Basin, Nebraska-USA

    NASA Astrophysics Data System (ADS)

    Irmak, S.; Kabenge, I.; Rudnick, D.; Knezevic, S.; Woodward, D.; Moravek, M.

    2013-02-01

    SummaryApplication of two-step approach of evapotranspiration (ET) crop coefficients (Kc) to "approximate" a very complex process of actual evapotranspiration (ETa) for field crops has been practiced by water management community. However, the use of Kc, and in particular the concept of growing degree days (GDD) to estimate Kc, have not been sufficiently studied for estimation of evaporative losses from riparian vegetation. Our study is one of the first to develop evapotranspiration crop coefficient (KcET) curves for mixed riparian vegetation and transpiration (TRP) crop coefficients (KcTRP) for individual riparian species as a function GDD through extensive field campaigns conducted in 2009 and 2010 in the Platte River Basin in central Nebraska, USA. KcTRP values for individual riparian vegetation species [Common reed (Phragmites australis), Cottonwood (Populus deltoids) and Peach-leaf willow (Salix amygdaloides)] were quantified from the TRP rates obtained using scaled-up canopy resistance from measured leaf-level stomatal resistance and reference evapotranspiration. The KcET and KcTRP curves were developed for alfalfa-reference (KcrET and KcrTRP) surface. The seasonal average mixed riparian plant community KcrET was 0.89 in 2009 and 1.27 in 2010. In 2009, the seasonal average KcrTRP values for Common reed, Cottonwood and Peach-leaf willow were 0.57, 0.51 and 0.62, respectively. In 2010, the seasonal average KcrTRP were 0.69, 0.62 and 0.83 for the same species, respectively. In general, TRP crop coefficients had less interannual variability than the KcrET. Response of the vegetation to flooding in 2010 played an important role on the interannual variability of KcrET values. We demonstrated good performance and reliability of developed GDD-based KcrTRP curves by using the curves developed for 2009 to predict TRP rates of individual species in 2010. Using the KcrTRP curves developed during the 2009 season, we were able to predict the TRP rates for Common reed

  14. Reduced nighttime transpiration is a relevant breeding target for high water-use efficiency in grapevine.

    PubMed

    Coupel-Ledru, Aude; Lebon, Eric; Christophe, Angélique; Gallo, Agustina; Gago, Pilar; Pantin, Florent; Doligez, Agnès; Simonneau, Thierry

    2016-08-01

    Increasing water scarcity challenges crop sustainability in many regions. As a consequence, the enhancement of transpiration efficiency (TE)-that is, the biomass produced per unit of water transpired-has become crucial in breeding programs. This could be achieved by reducing plant transpiration through a better closure of the stomatal pores at the leaf surface. However, this strategy generally also lowers growth, as stomatal opening is necessary for the capture of atmospheric CO2 that feeds daytime photosynthesis. Here, we considered the reduction in transpiration rate at night (En) as a possible strategy to limit water use without altering growth. For this purpose, we carried out a genetic analysis for En and TE in grapevine, a major crop in drought-prone areas. Using recently developed phenotyping facilities, potted plants of a cross between Syrah and Grenache cultivars were screened for 2 y under well-watered and moderate soil water deficit scenarios. High genetic variability was found for En under both scenarios and was primarily associated with residual diffusion through the stomata. Five quantitative trait loci (QTLs) were detected that underlay genetic variability in En Interestingly, four of them colocalized with QTLs for TE. Moreover, genotypes with favorable alleles on these common QTLs exhibited reduced En without altered growth. These results demonstrate the interest of breeding grapevine for lower water loss at night and pave the way to breeding other crops with this underexploited trait for higher TE. PMID:27457942

  15. Streamwise-varying steady transpiration control in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Gómez, F.; Blackburn, H. M.; Rudman, M.; Sharma, A. S.; McKeon, B. J.

    2016-06-01

    A study of the the main features of low- and high amplitude steady streamwise wall transpiration applied to pipe flow is presented. The effect of the two transpiration parameters, amplitude and wavenumber, on the flow have been investigated by means of direct numerical simulation at a moderate turbulent Reynolds number. The behaviour of the three identified mechanisms that act in the flow: modification of Reynolds shear stress, steady streaming and generation of non-zero mean streamwise gradients, have been linked to the transpiration parameters. The observed trends have permitted the identification of wall transpiration configurations able to reduce or increase the overall flow rate in -36.1% and 19.3% respectively. A resolvent analysis has been carried out to obtain a description of the reorganization of the flow structures induced by the transpiration.

  16. Transpiration Cooling Experiment

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  17. Role of aquaporins in determining transpiration and photosynthesis in water-stressed plants: crop water-use efficiency, growth and yield.

    PubMed

    Moshelion, Menachem; Halperin, Ofer; Wallach, Rony; Oren, Ram; Way, Danielle A

    2015-09-01

    The global shortage of fresh water is one of our most severe agricultural problems, leading to dry and saline lands that reduce plant growth and crop yield. Here we review recent work highlighting the molecular mechanisms allowing some plant species and genotypes to maintain productivity under water stress conditions, and suggest molecular modifications to equip plants for greater production in water-limited environments. Aquaporins (AQPs) are thought to be the main transporters of water, small and uncharged solutes, and CO2 through plant cell membranes, thus linking leaf CO2 uptake from the intercellular airspaces to the chloroplast with water loss pathways. AQPs appear to play a role in regulating dynamic changes of root, stem and leaf hydraulic conductivity, especially in response to environmental changes, opening the door to using AQP expression to regulate plant water-use efficiency. We highlight the role of vascular AQPs in regulating leaf hydraulic conductivity and raise questions regarding their role (as well as tonoplast AQPs) in determining the plant isohydric threshold, growth rate, fruit yield production and harvest index. The tissue- or cell-specific expression of AQPs is discussed as a tool to increase yield relative to control plants under both normal and water-stressed conditions. PMID:25039365

  18. Growth and transpiration of Japanese cedar (Cryptomeria japonica) and Hinoki cypress (Chamaecyparis obtusa) seedlings in response to soil water content.

    PubMed

    Nagakura, Junko; Shigenaga, Hidetoshi; Akama, Akio; Takahashi, Masamichi

    2004-11-01

    To investigate the effects of soil water content on growth and transpiration of Japanese cedar (Cryptomeria japonica D. Don) and Hinoki cypress (Chamaecyparis obtusa (Siebold et Zucc.) Endl.), potted seedlings were grown in well-watered soil (wet treatment) or in drying soil (dry treatment) for 12 weeks. Seedlings in the wet treatment were watered once every 2 or 3 days, whereas seedlings in the dry treatment were watered when soil water content (Theta; m3 m(-3)) reached 0.30, equivalent to a soil matric potential of -0.06 MPa. From Weeks 7 to 12 after the onset of the treatments, seedling transpiration was measured by weighing the potted seedlings. After the last watering, changes in transpiration rate during soil drying were monitored intensely. The dry treatment restricted aboveground growth but increased biomass allocation to the roots in both species, resulting in no significant treatment difference in whole-plant biomass production. The species showed similar responses in relative growth rate (RGR), net assimilation rate (NAR) and shoot mass ratio (SMR) to the dry treatment. Although NAR did not change significantly in either C. japonica or C. obtusa as the soil dried, the two species responded differently to the dry treatment in terms of mean transpiration rate (E) and water-use efficiency (WUE), which are parameters that relate to NAR. In the dry treatment, both E and WUE of C. japonica were stable, whereas in C. obtusa, E decreased and WUE increased (E and WUE counterbalanced to maintain a constant NAR). Transpiration rates were lower in C. obtusa seedlings than in C. japonica seedlings, even in well-watered conditions. During soil drying, the transpiration rate decreased after Theta reached about 0.38 (-0.003 MPa) in C. obtusa and 0.32 (-0.028 MPa) in C. japonica. We conclude that C. obtusa has more water-saving characteristics than C. japonica, particularly when water supply is limited. PMID:15339729

  19. Enhanced transpiration in response to wind effects at the edge of a blue gum (Eucalyptus globulus) plantation.

    PubMed

    Taylor, P J; Nuberg, I K; Hatton, T J

    2001-04-01

    In Australia, tree planting has been widely promoted to alleviate dryland salinity and one proposed planting configuration is that of strategically placed interception belts. We conducted an experiment to determine the effect of tree position in a belt on transpiration rate. We also assessed how much the effect of tree position can be explained by advection and environmental conditions. Daily transpiration rates were determined by the heat pulse velocity technique for four edge and 12 inner trees in a 7-year-old Tasmanian blue gum (Eucalyptus globulus) plantation in South Australia. Various climatic variables were logged automatically at one edge of the plantation. The relationship between daily sap flow and sapwood area was strongly linear for the edge trees (r2 = 0.97), but only moderately correlated for the inner trees (r2 = 0.46), suggesting an edge effect. For all trees, sap flow normalized to sapwood area (Qs) increased with potential evaporation (PE) initially and then became independent as PE increased further. There was a fairly close correlation between transpiration of the edge and inner trees, implying that water availability was partially responsible for the difference between inner and edge trees. However, the ratio of edge tree to inner tree transpiration differed from unity, indicating differences in canopy conductance, which were estimated by an inverse form of the Penman-Monteith equation. When canopy conductances were less than a critical value, there was a strong linear relationship between Qs of the edge and inner trees. When canopy conductances of the edge trees were greater than the critical value, the slope of the linear relationship was steeper, indicating greater transpiration of the edge trees compared with the inner trees. This was interpreted as evidence for enhancement of transpiration of the edge trees by advection of wind energy. PMID:11282580

  20. Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration.

    PubMed

    Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

    2015-01-01

    Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species. PMID:26734024

  1. Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration

    PubMed Central

    Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

    2015-01-01

    Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species. PMID:26734024

  2. Performance of a transpiration-regenerative cooled rocket thrust chamber

    NASA Technical Reports Server (NTRS)

    Valler, H. W.

    1979-01-01

    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.

  3. Idaho Chemical Processing Plant failure rate database

    SciTech Connect

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

    1995-08-01

    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 of how this mission change influenced the relevance of failure data also has been included. This report contains two data sources: the ICPP Failure Rate Database and a generic failure rate database. A discussion is presented on the approaches and assumptions used to develop the data in the ICPP Failure Rate Database. The generic database is included along with a short discussion of its application. A brief discussion of future projects recommended to strengthen and lend credibility to the ICPP Failure Rate Database also is included.

  4. Wind-induced leaf transpiration

    NASA Astrophysics Data System (ADS)

    Huang, Cheng-Wei; Chu, Chia-Ren; Hsieh, Cheng-I.; Palmroth, Sari; Katul, Gabriel G.

    2015-12-01

    While the significance of leaf transpiration (fe) on carbon and water cycling is rarely disputed, conflicting evidence has been reported on how increasing mean wind speed (U) impacts fe from leaves. Here, conditions promoting enhancement or suppression of fe with increasing U for a wide range of environmental conditions are explored numerically using leaf-level gas exchange theories that combine a stomatal conductance model based on optimal water use strategies (maximizing the 'net' carbon gain at a given fe), energy balance considerations, and biochemical demand for CO2. The analysis showed monotonic increases in fe with increasing U at low light levels. However, a decline in modeled fe with increasing U were predicted at high light levels but only in certain instances. The dominant mechanism explaining this decline in modeled fe with increasing U is a shift from evaporative cooling to surface heating at high light levels. New and published sap flow measurements for potted Pachira macrocarpa and Messerschmidia argentea plants conducted in a wind tunnel across a wide range of U (2 - 8 m s-1) and two different soil moisture conditions were also employed to assess how fe varies with increasing U. The radiative forcing imposed in the wind tunnel was only restricted to the lower end of expected field conditions. At this low light regime, the findings from the wind tunnel experiments were consistent with the predicted trends.

  5. Rising CO2 widens the transpiration-photosynthesis optimality space

    NASA Astrophysics Data System (ADS)

    de Boer, Hugo J.; Eppinga, Maarten B.; Dekker, Stefan C.

    2016-04-01

    Stomatal conductance (gs) and photosynthetic biochemistry, typically expressed by the temperature-adjusted maximum rates of carboxylation (V cmax) and electron transport (Jmax), are key traits in land ecosystem models. Contrary to the many approaches available for simulating gs responses, the biochemical parameters V cmax and Jmax are often treated as static traits in ecosystem models. However, observational evidence indicates that V cmax and Jmax respond to persistent changes in atmospheric CO2. Hence, ecosystem models may be improved by incorporating coordinated responses of photosynthetic biochemistry and gs to atmospheric CO2. Recently, Prentice et al. (2014) proposed an optimality framework (referred to as the Prentice framework from here on) to predict relationships between V cmax and gs based on Fick's law, Rubisco-limited photosynthesis and the carbon costs of transpiration and photosynthesis. Here we show that this framework is, in principle, suited to predict CO2-induced changes in the V cmax ‑gs relationships. The framework predicts an increase in the V cmax:gs-ratio with higher atmospheric CO2, whereby the slope of this relationship is determined by the carbon costs of transpiration and photosynthesis. For our empirical analyses we consider that the carbon cost of transpiration is positively related to the plant's Huber value (sapwood area/leaf area), while the carbon cost of photosynthesis is positively related to the maintenance cost of the photosynthetic proteins. We empirically tested the predicted effect of CO2 on the V cmax:gs-ratio in two genotypes of Solanum dulcamara (bittersweet) that were grown from seeds to maturity under 200, 400 and 800 ppm CO2 in walk-in growth chambers with tight control on light, temperature and humidity. Seeds of the two Solanum genotypes were obtained from two distinct natural populations; one adapted to well-drained sandy soil (the 'dry' genotype) and one adapted to poorly-drained clayey soil (the 'wet' genotype

  6. Reduced nighttime transpiration is a relevant breeding target for high water-use efficiency in grapevine

    PubMed Central

    Coupel-Ledru, Aude; Lebon, Eric; Christophe, Angélique; Gallo, Agustina; Gago, Pilar; Pantin, Florent; Doligez, Agnès; Simonneau, Thierry

    2016-01-01

    Increasing water scarcity challenges crop sustainability in many regions. As a consequence, the enhancement of transpiration efficiency (TE)—that is, the biomass produced per unit of water transpired—has become crucial in breeding programs. This could be achieved by reducing plant transpiration through a better closure of the stomatal pores at the leaf surface. However, this strategy generally also lowers growth, as stomatal opening is necessary for the capture of atmospheric CO2 that feeds daytime photosynthesis. Here, we considered the reduction in transpiration rate at night (En) as a possible strategy to limit water use without altering growth. For this purpose, we carried out a genetic analysis for En and TE in grapevine, a major crop in drought-prone areas. Using recently developed phenotyping facilities, potted plants of a cross between Syrah and Grenache cultivars were screened for 2 y under well-watered and moderate soil water deficit scenarios. High genetic variability was found for En under both scenarios and was primarily associated with residual diffusion through the stomata. Five quantitative trait loci (QTLs) were detected that underlay genetic variability in En. Interestingly, four of them colocalized with QTLs for TE. Moreover, genotypes with favorable alleles on these common QTLs exhibited reduced En without altered growth. These results demonstrate the interest of breeding grapevine for lower water loss at night and pave the way to breeding other crops with this underexploited trait for higher TE. PMID:27457942

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

    USGS Publications Warehouse

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

    2008-01-01

    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

  8. TaER Expression Is Associated with Transpiration Efficiency Traits and Yield in Bread Wheat

    PubMed Central

    Zheng, Jiacheng; Yang, Zhiyuan; Madgwick, Pippa J.; Carmo-Silva, Elizabete; Parry, Martin A. J.; Hu, Yin-Gang

    2015-01-01

    ERECTA encodes a receptor-like kinase and is proposed as a candidate for determining transpiration efficiency of plants. Two genes homologous to ERECTA in Arabidopsis were identified on chromosomes 6 (TaER2) and 7 (TaER1) of bread wheat (Triticum aestivum L.), with copies of each gene on the A, B and D genomes of wheat. Similar expression patterns were observed for TaER1 and TaER2 with relatively higher expression of TaER1 in flag leaves of wheat at heading (Z55) and grain-filling (Z73) stages. Significant variations were found in the expression levels of both TaER1 and TaER2 in the flag leaves at both growth stages among 48 diverse bread wheat varieties. Based on the expression of TaER1 and TaER2, the 48 wheat varieties could be classified into three groups having high (5 varieties), medium (27 varieties) and low (16 varieties) levels of TaER expression. Significant differences were also observed between the three groups varying for TaER expression for several transpiration efficiency (TE)- related traits, including stomatal density (SD), transpiration rate, photosynthetic rate (A), instant water use efficiency (WUEi) and carbon isotope discrimination (CID), and yield traits of biomass production plant-1 (BYPP) and grain yield plant-1 (GYPP). Correlation analysis revealed that the expression of TaER1 and TaER2 at the two growth stages was significantly and negatively associated with SD (P<0.01), transpiration rate (P<0.05) and CID (P<0.01), while significantly and positively correlated with flag leaf area (FLA, P<0.01), A (P<0.05), WUEi (P<0.05), BYPP (P<0.01) and GYPP (P<0.01), with stronger correlations for TaER1 than TaER2 and at grain-filling stage than at heading stage. These combined results suggested that TaER involved in development of transpiration efficiency -related traits and yield in bread wheat, implying a function for TaER in regulating leaf development of bread wheat and contributing to expression of these traits. Moreover, the results indicate

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

    PubMed Central

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

    2013-01-01

    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. PMID:23669746

  10. Measurements of transpiration from Eucalyptus plantations, India, using deuterium tracing

    SciTech Connect

    Calder, I.R.; Swaminath, M.H.; Kariyappa, G.S.; Srinivasalu, N.V.; Murthy, K.V.; Mumtaz, J.

    1992-12-31

    Measurements of transpiration from individual trees in Eucalyptus plantations at four different sites in Karnataka, southern India, are presented. These show large (as much as tenfold) differences in the transpiration between pre and post monsoon periods; a reflection of the effects of soil moisture stress in the pre monsoon periods. For trees with diameters at breast height (DBH) less than 10 cm the transpiration rate of individual trees is proportional to the square of the DBH. For trees which are not experiencing soil water stress the daily transpiration rate of individual trees, q, is well represented by the relation: q= (6.6 {+-} 0.3)g m{sup 3}d{sup {minus}1} where g (m{sup 2}) is the tree basal area. On a unit ground area basis the transpiration rate, expressed as a depth per day, is given by the relation: E{sub t}= (0.66 {+-} 0.03)G (mm d{sup {minus}1}) where G (m{sup 2} ha{sup {minus}1}) is the total basal area per hectare. For all the sites studied, although there is evidence for the mining of soil water as roots penetrate deeper depths in the soil each year, there is no evidence for direct abstraction from the watertable.

  11. Partitioning evapotranspiration into evaporation and transpiration in a corn field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evapotranspiration (ET) is a main component of the hydrology cycle. It consists of soil water evaporation (E) and plant transpiration (T). Accurate partitioning of ET into E and T is challenging. We measured soil water E using heat pulse sensors and a micro-Bowen ratio system, T using stem flow gaug...

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

    PubMed Central

    Matimati, Ignatious

    2014-01-01

    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 μm 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 (g s), 1.2-fold higher intercellular [CO2] (C i), and 3.4-fold lower water use efficiency than ‘interception’ plants, despite comparable values of photosynthetic rate (A). E, g s, and C i 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

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

    PubMed

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

    2014-01-01

    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 μm 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

  14. Transpiration during life cycle in controlled wheat growth

    NASA Technical Reports Server (NTRS)

    Volk, Tyler; Rummel, John D.

    1989-01-01

    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 which varies during the life cycle, are examined. Results indicate that during the main phase of vegetative growth in the first half of the life cycle, the rate of transpiration per unit mass of inedible biomass is more than double the rate during the phase of grain development and maturation during latter half of the life cycle.

  15. An experimental set-up to study carbon, water, and nitrate uptake rates by hydroponically grown plants.

    PubMed

    Andriolo, J L; Le Bot, J; Gary, C; Sappe, G; Orlando, P; Brunel, B; Sarrouy, C

    1996-01-01

    The experimental system described allows concomitant hourly measurements of CO2, H2O, and NO3 uptake rates by plants grown hydroponically in a greenhouse. Plants are enclosed in an airtight chamber through which air flows at a controlled speed. Carbon dioxide exchange and transpiration rates are determined from respective differences of concentrations of CO2 and water vapor of the air at the system inlet and outlet. This set-up is based on the "open-system" principle with improvements made on existing systems. For instance, propeller anemometers are used to monitor air flow rates in the chamber. From their signal it is possible to continuously adjust air speed to changing environmental conditions and plant activity. The air temperature inside the system therefore never rises above that outside. Water and NO3 uptake rates are calculated at time intervals from changes in the volume and the NO3 concentration of the nutrient solution in contact with the roots. The precise measurement of the volume of solution is achieved using a balance which has a higher precision than any liquid level sensors. Nitrate concentration is determined in the laboratory from aliquots of solution sampled at time intervals. A number of test runs are reported which validate the measurements and confirm undisturbed conditions within the system. Results of typical diurnal changes in CO2, H2O, and NO3 uptake rates by fruiting tomato plants are also presented. PMID:11541097

  16. Temporal variations of the 18O/16O signal of the whole-canopy transpiration in a temperate forest

    NASA Astrophysics Data System (ADS)

    Lee, Xuhui; Kim, Kyounghee; Smith, Ronald

    2007-09-01

    Biosphere-atmosphere exchange of water vapor isotopes plays an important role in the global atmospheric 18O-CO2 and 18O-O2 budgets. In this paper, we report the results of the first continuous measurements of isotope ratios of water vapor and the evapotranspiration flux in a temperate forest over one full growing season. We found that the 18O/16O isotopic signal of the whole-canopy transpiration (δT) was not in steady state with respect to plant source water. The departure from steady state was greatest at night and on days of low transpiration rates. Relative humidity was an important driver on timescales shorter than a few hours; on the diurnal timescale, the nonsteady state behavior was driven by relative humidity and the covarying transpiration rate. On average, δT was lowest in midmorning and highest at midnight, with an average peak-to-peak variation on the order of 15‰ over the growing season. A diurnal variation of 60‰ or more was observed on some days. On the seasonal timescale, δT was tightly coupled with the precipitation isotope ratio in the early growing season and fluctuated around the isotope ratio of the stem water of overstory trees in the late growing season. The temporal shift suggests that the forest switched its water source from the shallow to the deep soil pool and that the overstory trees dominated the whole stand transpiration in the late growing season. Using isotopic partitioning, we estimated that the overstory trees contributed roughly 70% to the whole-stand transpiration water loss during the growing season.

  17. Transpiration as landfill leachate phytotoxicity indicator.

    PubMed

    Białowiec, Andrzej

    2015-05-01

    An important aspect of constructed wetlands design for landfill leachate treatment is the assessment of landfill leachate phytotoxicity. Intravital methods of plants response observation are required both for lab scale toxicity testing and field examination of plants state. The study examined the toxic influence of two types of landfill leachate from landfill in Zakurzewo (L1) and landfill in Wola Pawłowska (L2) on five plant species: reed Phragmites australis (Cav.) Trin. ex Steud, manna grass Glyceria maxima (Hartm.) Holmb., bulrush Schoenoplectus lacustris (L.) Palla, sweet flag Acorus calamus L., and miscanthus Miscanthus floridulus (Labill) Warb. Transpiration measurement was used as indicator of plants response. The lowest effective concentration causing the toxic effect (LOEC) for each leachate type and plant species was estimated. Plants with the highest resistance to toxic factors found in landfill leachate were: sweet flag, bulrush, and reed. The LOEC values for these plants were, respectively, 17%, 16%, 9% in case of leachate L1 and 21%, 18%, 14% in case of L2. Leachate L1 was more toxic than L2 due to a higher pH value under similar ammonia nitrogen content, i.e. pH 8.74 vs. pH 8.00. PMID:25708408

  18. The positive effect of skin transpiration in peach fruit growth.

    PubMed

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

    2010-09-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    /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.

  20. Transpiring Cooling of a Scram-Jet Engine Combustion Chamber

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  1. Photosynthetic Rate of Soybean at Various Planting Dates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean [Glycine max (L.) Merr.] yield is typically maximized by early planting in the upper Midwest USA. Seasonal carbon dioxide exchange rate (CER) has not been quantified to explain the positive yield response to early planting. Five planting dates were established between 18-April and 22-May nea...

  2. Gas-phase and transpiration-driven mechanisms for volatilization through wetland macrophytes.

    PubMed

    Reid, Matthew C; Jaffé, Peter R

    2012-05-15

    Natural and constructed wetlands have gained attention as potential tools for remediation of shallow sediments and groundwater contaminated with volatile organic compounds (VOCs). Wetland macrophytes are known to enhance rates of contaminant removal via volatilization, but the magnitude of different volatilization mechanisms, and the relationship between volatilization rates and contaminant physiochemical properties, remain poorly understood. Greenhouse mesocosm experiments using the volatile tracer sulfur hexafluoride were conducted to determine the relative magnitudes of gas-phase and transpiration-driven volatilization mechanisms. A numerical model for vegetation-mediated volatilization was developed, calibrated with tracer measurements, and used to predict plant-mediated volatilization of common VOCs as well as quantify the contribution of different volatilization pathways. Model simulations agree with conclusions from previous work that transpiration is the main driver for volatilization of VOCs, but also demonstrate that vapor-phase transport in wetland plants is significant, and can represent up to 50% of the total flux for compounds with greater volatility like vinyl chloride. PMID:22509995

  3. Tamarix transpiration along a semiarid river has negligible impact on water resources

    NASA Astrophysics Data System (ADS)

    McDonald, Alyson K.; Wilcox, Bradford P.; Moore, Georgianne W.; Hart, Charles R.; Sheng, Zhuping; Owens, M. Keith

    2015-07-01

    The proliferation of saltcedar (Tamarix spp.) along regulated rivers in the western United States has transformed riparian plant communities. It is commonly assumed that transpiration by these alien plants has led to large losses of water that would otherwise contribute to streamflow. Control of saltcedar, therefore, has been considered a viable strategy for conserving water and increasing streamflow in these regions. In an effort to better understand the linkage between transpiration by saltcedar and streamflow, we monitored transpiration, stream stage, and groundwater elevations within a saltcedar stand along the Pecos River during June 2004. Transpiration, as determined by sap flow measurements, exhibited a strong diel pattern; stream stage did not. Diel fluctuations in groundwater levels were observed, but only in one well, which was located in the center of the saltcedar stand. In that well, the correlation between maximal transpiration and minimal groundwater elevation was weak (R2 = 0.16). No effects of transpiration were detected in other wells within the saltcedar stand, nor in the stream stage. The primary reason, we believe, is that the saltcedar stand along this reach of the Pecos River has relatively low sapwood area and a limited spatial extent resulting in very low transpiration compared with the stream discharge. Our results are important because they provide a mechanistic explanation for the lack of increase in streamflow following large-scale control of invasive trees along semiarid rivers.

  4. Transpiration of urban trees and its cooling effect in a high latitude city.

    PubMed

    Konarska, Janina; Uddling, Johan; Holmer, Björn; Lutz, Martina; Lindberg, Fredrik; Pleijel, Håkan; Thorsson, Sofia

    2016-01-01

    An important ecosystem service provided by urban trees is the cooling effect caused by their transpiration. The aim of this study was to quantify the magnitude of daytime and night-time transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), to analyse the influence of weather conditions and surface permeability on the tree transpiration, and to find out whether tree transpiration contributed to daytime or nocturnal cooling. Stomatal conductance and leaf transpiration at day and night were measured on mature street and park trees of seven common tree species in Gothenburg: Tilia europaea, Quercus robur, Betula pendula, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica and Prunus serrulata. Transpiration increased with vapour pressure deficit and photosynthetically active radiation. Midday rates of sunlit leaves ranged from less than 1 mmol m(-2) s(-1) (B. pendula) to over 3 mmol m(-2) s(-1) (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected crown area. A simple estimate of available rainwater, comprising of precipitation sum and fractional surface permeability within the crown area, was found to explain 68% of variation in midday stomatal conductance. Night-time transpiration was observed in all studied species and amounted to 7 and 20% of midday transpiration of sunlit and shaded leaves, respectively. With an estimated night-time latent heat flux of 24 W m(-2), tree transpiration significantly increased the cooling rate around and shortly after sunset, but not later in the night. Despite a strong midday latent heat flux of 206 W m(-2), a cooling effect of tree transpiration was not observed during the day. PMID:26048702

  5. Transpiration of urban trees and its cooling effect in a high latitude city

    NASA Astrophysics Data System (ADS)

    Konarska, Janina; Uddling, Johan; Holmer, Björn; Lutz, Martina; Lindberg, Fredrik; Pleijel, Håkan; Thorsson, Sofia

    2016-01-01

    An important ecosystem service provided by urban trees is the cooling effect caused by their transpiration. The aim of this study was to quantify the magnitude of daytime and night-time transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), to analyse the influence of weather conditions and surface permeability on the tree transpiration, and to find out whether tree transpiration contributed to daytime or nocturnal cooling. Stomatal conductance and leaf transpiration at day and night were measured on mature street and park trees of seven common tree species in Gothenburg: Tilia europaea, Quercus robur, Betula pendula, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica and Prunus serrulata. Transpiration increased with vapour pressure deficit and photosynthetically active radiation. Midday rates of sunlit leaves ranged from less than 1 mmol m-2 s-1 ( B. pendula) to over 3 mmol m-2 s-1 ( Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected crown area. A simple estimate of available rainwater, comprising of precipitation sum and fractional surface permeability within the crown area, was found to explain 68 % of variation in midday stomatal conductance. Night-time transpiration was observed in all studied species and amounted to 7 and 20 % of midday transpiration of sunlit and shaded leaves, respectively. With an estimated night-time latent heat flux of 24 W m-2, tree transpiration significantly increased the cooling rate around and shortly after sunset, but not later in the night. Despite a strong midday latent heat flux of 206 W m-2, a cooling effect of tree transpiration was not observed during the day.

  6. Transpiration in an oil palm landscape: effects of palm age

    NASA Astrophysics Data System (ADS)

    Röll, A.; Niu, F.; Meijide, A.; Hardanto, A.; Hendrayanto; Knohl, A.; Hölscher, D.

    2015-06-01

    Oil palm (Elaeis guineensis Jacq.) plantations cover large and continuously increasing areas of humid tropical lowlands. Landscapes dominated by oil palms usually consist of a mosaic of mono-cultural, homogeneous stands of varying age, which may be heterogeneous in their water use characteristics. However, studies on the water use characteristics of oil palms are still at an early stage and there is a lack of knowledge on how oil palm expansion will affect the major components of the hydrological cycle. To provide first insights into hydrological landscape-level consequences of oil palm cultivation, we derived transpiration rates of oil palms in stands of varying age, estimated the contribution of palm transpiration to evapotranspiration, and analyzed the influence of fluctuations in environmental variables on oil palm water use. We studied 15 two- to 25 year old stands in the lowlands of Jambi, Indonesia. A sap flux technique with an oil palm specific calibration and sampling scheme was used to derive leaf-, palm- and stand-level water use rates in all stands under comparable environmental conditions. Additionally, in a two- and a 12 year old stand, eddy covariance measurements were conducted to derive evapotranspiration rates. Water use rates per leaf and palm increased 5-fold from an age of two years to a stand age of approx. 10 years and then remained relatively constant. A similar trend was visible, but less pronounced, for estimated stand transpiration rates of oil palms; they varied 12-fold, from 0.2 mm day-1 in a 2 year old to 2.5 mm day-1 in a 12 year old stand, showing particularly high variability in transpiration rates among medium-aged stands. Confronting sap flux and eddy-covariance derived water fluxes suggests that transpiration contributed 8 % to evapotranspiration in the 2 year old stand and 53 % in the 12 year old stand, indicating variable and substantial additional sources of evaporation, e.g. from the soil, the ground vegetation and from trunk

  7. Uncertainty in the response of transpiration to CO2 and implications for climate change

    NASA Astrophysics Data System (ADS)

    Mengis, N.; Keller, D. P.; Eby, M.; Oschlies, A.

    2015-09-01

    While terrestrial precipitation is a societally highly relevant climate variable, there is little consensus among climate models about its projected 21st century changes. An important source of precipitable water over land is plant transpiration. Plants control transpiration by opening and closing their stomata. The sensitivity of this process to increasing CO2 concentrations is uncertain. To assess the impact of this uncertainty on future climate, we perform experiments with an intermediate complexity Earth System Climate Model (UVic ESCM) for a range of model-imposed transpiration-sensitivities to CO2. Changing the sensitivity of transpiration to CO2 causes simulated terrestrial precipitation to change by -10% to +27% by 2100 under a high emission scenario. This study emphasises the importance of an improved assessment of the dynamics of environmental impact on vegetation to better predict future changes of the terrestrial hydrological and carbon cycles.

  8. Uncertainty in the response of transpiration to CO2 and implications for climate change

    NASA Astrophysics Data System (ADS)

    Mengis, Nadine; Keller, David; Eby, Michael; Oschlies, Andreas

    2015-04-01

    While terrestrial precipitation is a societally highly relevant climate variable, there is little consensus among climate models about its projected 21st century changes. The main source of precipitable water over land is plant transpiration. Plants control transpiration by opening and closing their stomata. The sensitivity of this process to increasing CO2 concentrations is uncertain. To assess the impact of this uncertainty on future climate, we perform experiments with an intermediate complexity Earth System Climate Model (UVic ESCM) for a range of model-imposed transpiration-sensitivities to CO2. Changing the sensitivity of transpiration to CO2 causes simulated terrestrial precipitation to change by -10 % to +27 % by 2100 under a high emission scenario. This study emphasises the importance of an improved assessment of the dynamics of environmental impact on vegetation to better predict future changes of the terrestrial hydrological and carbon cycle.

  9. Decreased transpiration in poplar trees exposed to 2,4,6-trinitrotoluene

    SciTech Connect

    Thompson, P.L.; Ramer, L.A.; Guffey, A.P.; Schnoor, J.L.

    1998-01-01

    The improper handling of the toxic compound 2,4,6-trinitrotoluene (TNT) has led to the contamination of soil and groundwater, and the uptake of TNT by a variety of plants has been established. This article discusses the effects of various concentrations of the explosive 2,4,6-trinitrotoluene (TNT) on the transpiration of hybrid poplar trees growing in hydroponic media. Transpiration was measured daily by gravimetric means. The rapid removal of TNT from hydroponic solutions was a result of plant uptake and required a daily dosage of TNT to ensure a relatively constant exposure over time. Transpiration decreased with increasing TNT concentrations {ge}5 mg/L. Decreases in transpiration were accompanied by leaf chlorosis and abscission. A comparison between a laboratory study and a pilot-scale experiment showed good scale-up potential.

  10. Spatial Variability of Tree Transpiration Along a Soil Drainage Gradient of Boreal Black Spruce Forest

    NASA Astrophysics Data System (ADS)

    Angstmann, J. L.; Ewers, B. E.; Kwon, H.; Bond-Lamberty, B.; Amiro, B.; Gower, S. T.

    2008-12-01

    results of Picea mariana differed between drainage conditions when expressed per unit xylem area with trees in poorly-drained soils experiencing higher rates than trees in well-drained areas (101.79 and 83.02 g cm-2 day-1 respectively). In contrast, when expressed as transpiration per tree, trees on well-drained soils had higher rates than those in poorly-drained locations (366.96 and 216.82 g tree-1 day-1 respectively). This indicates that tree size, reflected in sapwood area per ground area, which is constrained by anaerobic conditions across well- to poorly-drained areas, is driving differences in tree transpiration. Initial spatial analyses show that spatial autocorrelation decreases from 51.3 to 24.6 meters as D increases from 0.9 to 2.1 kPa. This phenomenon is explained by tree hydraulics and more patchy stomatal response as trees regulate water loss. Thus, regional scale bottom-up process models of boreal forest transpiration can be simplified with respect to soil drainage while retaining mechanistic rigor with respect to plant hydraulics.

  11. Transpiration in an oil palm landscape: effects of palm age

    NASA Astrophysics Data System (ADS)

    Röll, A.; Niu, F.; Meijide, A.; Hardanto, A.; Hendrayanto; Knohl, A.; Hölscher, D.

    2015-10-01

    Oil palm (Elaeis guineensis Jacq.) plantations cover large and continuously increasing areas of humid tropical lowlands. Landscapes dominated by oil palms usually consist of a mosaic of mono-cultural, homogeneous stands of varying age, which may be heterogeneous in their water use characteristics. However, studies on the water use characteristics of oil palms are still at an early stage and there is a lack of knowledge on how oil palm expansion will affect the major components of the hydrological cycle. To provide first insights into hydrological landscape-level consequences of oil palm cultivation, we derived transpiration rates of oil palms in stands of varying age, estimated the contribution of palm transpiration to evapotranspiration, and analyzed the influence of fluctuations in environmental variables on oil palm water use. We studied 15 two- to 25-year old stands in the lowlands of Jambi, Indonesia. A sap flux technique with an oil palm specific calibration and sampling scheme was used to derive leaf-, palm- and stand-level water use rates in all stands under comparable environmental conditions. Additionally, in a two- and a 12-year old stand, eddy covariance measurements were conducted to derive evapotranspiration rates. Water use rates per leaf and palm increased 5-fold from an age of 2 years to a stand age of approx. 10 years and then remained relatively constant. A similar trend was visible, but less pronounced, for estimated stand transpiration rates of oil palms; they varied 12-fold, from 0.2 mm day-1 in a 2-year old to 2.5 mm day-1 in a 12-year old stand, showing particularly high variability in transpiration rates among medium-aged stands. Comparing sap flux and eddy-covariance derived water fluxes suggests that transpiration contributed 8 % to evapotranspiration in the 2-year old stand and 53 % in the 12-year old stand, indicating variable and substantial additional sources of evaporation, e.g., from the soil, the ground vegetation and from trunk

  12. Transpiration Cooling Of Hypersonic Blunt Body

    NASA Technical Reports Server (NTRS)

    Henline, William D.

    1991-01-01

    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.

  13. Transpiration of shrub species, Alnus firma under changing atmospheric environments in montane area, Japan

    NASA Astrophysics Data System (ADS)

    Miyazawa, Y.; Maruyama, A.; Inoue, A.

    2014-12-01

    In the large caldera of Mt. Aso in Japan, grasslands have been traditionally managed by the farmers. Due to changes in the social structure of the region, a large area of the grassland has been abandoned and was invaded by the shrubs with different hydrological and ecophysiological traits. Ecophysiological traits and their responses to seasonally changing environments are fundamental to project the transpiration rates under changing air and soil water environments, but less is understood. We measured the tree- and leaf-level ecophysiological traits of a shrub, Alnus firma in montane region where both rainfall and soil water content drastically changes seasonally. Sap flux reached the annual peak in evaporative summer (July-August) both in 2013 and 2014, although the duration was limited within a short period due to the prolonged rainy season before summer (2014) and rapid decrease in the air vapor pressure deficit (D) in late summer. Leaf ecophysiological traits in close relationship with gas exchange showed modest seasonal changes and the values were kept at relatively high levels typical in plants with nitrogen fixation under nutrient-poor environments. Stomatal conductance, which was measured at leaf-level measurements and sap flux measurements, showed responses to D, which coincided with the theoretical response for isohydric leaves. A multilayer model, which estimates stand-level transpiration by scaling up the leaf-level data, successfully captured the temporal trends in sap flux, suggesting that major processes were incorporated. Thus, ecophysiological traits of A. firma were characterized by the absence of responses to seasonally changing environments and the transpiration rate was the function of the interannually variable environmental conditions.

  14. Auxin metabolism rates and implications for plant development.

    PubMed

    Kramer, Eric M; Ackelsberg, Ethan M

    2015-01-01

    Studies of auxin metabolism rarely express their results as a metabolic rate, although the data obtained would often permit such a calculation to be made. We analyze data from 31 previously published papers to quantify the rates of auxin biosynthesis, conjugation, conjugate hydrolysis, and catabolism in seed plants. Most metabolic pathways have rates in the range 10 nM/h-1 μM/h, with the exception of auxin conjugation, which has rates as high as ~100 μM/h. The high rates of conjugation suggest that auxin metabolic sinks may be very small, perhaps as small as a single cell. By contrast, the relatively low rate of auxin biosynthesis requires plants to conserve and recycle auxin during long-distance transport. The consequences for plant development are discussed. PMID:25852709

  15. Auxin metabolism rates and implications for plant development

    PubMed Central

    Kramer, Eric M.; Ackelsberg, Ethan M.

    2015-01-01

    Studies of auxin metabolism rarely express their results as a metabolic rate, although the data obtained would often permit such a calculation to be made. We analyze data from 31 previously published papers to quantify the rates of auxin biosynthesis, conjugation, conjugate hydrolysis, and catabolism in seed plants. Most metabolic pathways have rates in the range 10 nM/h–1 μM/h, with the exception of auxin conjugation, which has rates as high as ~100 μM/h. The high rates of conjugation suggest that auxin metabolic sinks may be very small, perhaps as small as a single cell. By contrast, the relatively low rate of auxin biosynthesis requires plants to conserve and recycle auxin during long-distance transport. The consequences for plant development are discussed. PMID:25852709

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

    NASA Astrophysics Data System (ADS)

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

    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

  17. Plant respirometer enables high resolution of oxygen consumption rates

    NASA Technical Reports Server (NTRS)

    Foster, D. L.

    1966-01-01

    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.

  18. Rate of Contamination Removal of Two Phyto-remediation Sites at the DOE Portsmouth Gaseous Diffusion Plant

    SciTech Connect

    Lewis, A.C.; Baird, D.R.

    2006-07-01

    relationship between plant transpiration, soil moisture, and groundwater flow in a phyto-remediation system. The existing monitoring program was expanded in 2004 in order to evaluate the interactions among these processes. The purpose of this monitoring program was to determine the rate of contaminant removal and to more accurately predict the amount of time needed to remediate the contaminated groundwater. Initial planting occurred in 1999 at the X-740 area, with additional replanting in 2001 and 2002. In 2003, coring of selected trees and chemical analyses illustrated the presence of TCE; however, little impact was observed in groundwater levels, analytical monitoring, and periodic tree diameter monitoring at the X-740 area. To provide better understanding of how these phyto-remediation systems work, a portable weather station was installed at the X-740 area to provide data for estimating transpiration and two different systems for measuring sap flow and sap velocity were outfitted to numerous trees. After evaluating and refining the groundwater flow and contaminant transport models, the data gathered by these two inventive methods can be used to establish a rate of contaminant removal and to better predict the time required in order to meet remediation goals for the phyto-remediation systems located at the PORTS site. (authors)

  19. Mostly Plants. Individualized Biology Activities on: I. Investigating Bread Mold; II. Transpiration; III. Botany Project; IV. Collecting/Preserving/Identifying Leaves; [and] V. Student Science Laboratory Write-Ups.

    ERIC Educational Resources Information Center

    Gibson, Paul R.

    Individualized biology activities for secondary students are presented in this teaching guide. The guide is divided into five sections: (1) investigating bread mold; (2) investigating transpiration; (3) completing a botany project; (4) collecting, preserving, and identifying leaves; and (5) writing up science laboratory investigations. The…

  20. Nitrogen assimilation and transpiration: key processes conditioning responsiveness of wheat to elevated [CO2] and temperature.

    PubMed

    Jauregui, Iván; Aroca, Ricardo; Garnica, María; Zamarreño, Ángel M; García-Mina, José M; Serret, Maria D; Parry, Martin; Irigoyen, Juan J; Aranjuelo, Iker

    2015-11-01

    Although climate scenarios have predicted an increase in [CO(2)] and temperature conditions, to date few experiments have focused on the interaction of [CO(2)] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO(2). The main goal of this study was to analyze the effect of interacting [CO(2)] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO(2)] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO(2)] (400 vs 700 µmol mol(-1)) and temperature (ambient vs ambient + 4°C) in CO(2) gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO(2)] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO(2)] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient transport in leaves of plants exposed to elevated [CO(2)] and temperature, led to mineral depletion and therefore contributed to the inhibition of photosynthetic activity. PMID:25958969

  1. Modeling the uptake and transpiration of TCE using phreatophytic trees. Master`s Thesis

    SciTech Connect

    Wise, D.P.

    1997-12-01

    Phytoremediation is a recent addition to the numerous methods used today to remediate ground water contaminants. It is proving more effective and efficient compared to existing remediation techniques. The use of phreatophytes, or water seeking trees, has great potential for phytoremediation. These trees are fast growing, long lived, grow their roots down to the ground water table, transpire large amounts of water, and are proven to actively remove contaminants from the soil horizon. The purpose of this research is to develop quantitative concepts for understanding the dynamics of TCE uptake and transpiration by phreatophytic trees over a short rotation woody crop time frame. This will he done by constructing a system dynamics model of this process and running it over a wide range of conditions. This research will offer managers a tool to simulate long-term uptake and transpiration of TCE at potential sites. The results of this study indicate that TCE is actively removed from the soil horizon by phreatophytic trees and a significant proportion of this TCE is then transpired. Changes in soil horizon parameters, xylem flow rates, and variables in the uptake equation greatly influence TCE uptake rates as well as transpiration. Also, parameters used in equations representing flows in and out of the leaf greatly influence transpiration. Better understanding of these processes is essential for managers to accurately predict the amount of TCE removed and transpired during potential phytoremediation projects.

  2. Habitat Temperature and Precipitation of Arabidopsis thaliana Ecotypes Determine the Response of Foliar Vasculature, Photosynthesis, and Transpiration to Growth Temperature

    PubMed Central

    Adams, William W.; Stewart, Jared J.; Cohu, Christopher M.; Muller, Onno; Demmig-Adams, Barbara

    2016-01-01

    Acclimatory adjustments of foliar vascular architecture, photosynthetic capacity, and transpiration rate in Arabidopsis thaliana ecotypes (Italian, Polish [Col-0], Swedish) were characterized in the context of habitat of origin. Temperatures of the habitat of origin decreased linearly with increasing habitat latitude, but habitat precipitation was greatest in Italy, lowest in Poland, and intermediate in Sweden. Plants of the three ecotypes raised under three different growth temperature regimes (low, moderate, and high) exhibited highest photosynthetic capacities, greatest leaf thickness, highest chlorophyll a/b ratio and levels of β-carotene, and greatest levels of wall ingrowths in phloem transfer cells, and, in the Col-0 and Swedish ecotypes, of phloem per minor vein in plants grown at the low temperature. In contrast, vein density and minor vein tracheary to sieve element ratio increased with increasing growth temperature – most strongly in Col-0 and least strongly in the Italian ecotype – and transpirational water loss correlated with vein density and number of tracheary elements per minor vein. Plotting of these vascular features as functions of climatic conditions in the habitat of origin suggested that temperatures during the evolutionary history of the ecotypes determined acclimatory responses of the foliar phloem and photosynthesis to temperature in this winter annual that upregulates photosynthesis in response to lower temperature, whereas the precipitation experienced during the evolutionary history of the ecotypes determined adjustment of foliar vein density, xylem, and transpiration to temperature. In particular, whereas photosynthetic capacity, leaf thickness, and foliar minor vein phloem features increased linearly with increasing latitude and decreasing temperature of the habitats of origin in response to experimental growth at low temperature, transpiration rate, foliar vein density, and minor vein tracheary element numbers and cross

  3. Habitat Temperature and Precipitation of Arabidopsis thaliana Ecotypes Determine the Response of Foliar Vasculature, Photosynthesis, and Transpiration to Growth Temperature.

    PubMed

    Adams, William W; Stewart, Jared J; Cohu, Christopher M; Muller, Onno; Demmig-Adams, Barbara

    2016-01-01

    Acclimatory adjustments of foliar vascular architecture, photosynthetic capacity, and transpiration rate in Arabidopsis thaliana ecotypes (Italian, Polish [Col-0], Swedish) were characterized in the context of habitat of origin. Temperatures of the habitat of origin decreased linearly with increasing habitat latitude, but habitat precipitation was greatest in Italy, lowest in Poland, and intermediate in Sweden. Plants of the three ecotypes raised under three different growth temperature regimes (low, moderate, and high) exhibited highest photosynthetic capacities, greatest leaf thickness, highest chlorophyll a/b ratio and levels of β-carotene, and greatest levels of wall ingrowths in phloem transfer cells, and, in the Col-0 and Swedish ecotypes, of phloem per minor vein in plants grown at the low temperature. In contrast, vein density and minor vein tracheary to sieve element ratio increased with increasing growth temperature - most strongly in Col-0 and least strongly in the Italian ecotype - and transpirational water loss correlated with vein density and number of tracheary elements per minor vein. Plotting of these vascular features as functions of climatic conditions in the habitat of origin suggested that temperatures during the evolutionary history of the ecotypes determined acclimatory responses of the foliar phloem and photosynthesis to temperature in this winter annual that upregulates photosynthesis in response to lower temperature, whereas the precipitation experienced during the evolutionary history of the ecotypes determined adjustment of foliar vein density, xylem, and transpiration to temperature. In particular, whereas photosynthetic capacity, leaf thickness, and foliar minor vein phloem features increased linearly with increasing latitude and decreasing temperature of the habitats of origin in response to experimental growth at low temperature, transpiration rate, foliar vein density, and minor vein tracheary element numbers and cross

  4. Material Response of One-Dimensional, Steady-State Transpiration Cooling in Radiative and Convective Environments

    NASA Technical Reports Server (NTRS)

    Kubota, Hirotoshi

    1975-01-01

    A simplified analytical solution for thermal response of a transpiration-cooled porous heat-shield material in an intense radiative-convective heating environment is presented. Essential features of this approach are "two-flux method" for radiative transfer process and "two-temperature" assumption for solid and gas temperatures. Incident radiative-convective heatings are specified as boundary conditions. Sample results are shown using porous silica with CO2 transpiration and some parameters quantitatively show the effect on this transpiration cooling system. Summarized maps for mass injection rate, porosity and blowing correction factor for radiation are obtained in order to realize such a cooling system.

  5. Impact of the hydraulic capacity of plants on water and carbon fluxes in tropical South America

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Eun; Boyce, Kevin

    2010-12-01

    Angiosperms (flowering plants) have higher transpirational capacities than any other plants. Here we use climate model simulation to test the hypothesis that the high transpirational capacity of angiosperms plays a unique role in the maintenance of tropical rainforest. Their elevated transpiration rates are shown to increase recycling of precipitation up to ˜300 mm/yr (˜20% of total precipitation) averaged over the whole of tropical South America and to increase the wet season duration over the Amazon basin. Transpiration triggers convection by increasing moisture in the boundary layer and thereby decreasing atmospheric stability. If the moisture content of the boundary layer is sufficient, a double Intertropical Convergence Zone (ITCZ) is generated in October around 60°W-50°W, as observed in present-day climate, and the eastern part of the Amazon basin becomes wet (˜200 mm/month of precipitation). This double ITCZ is lost, however, and the region becomes dry (<50 mm/month of precipitation) in the absence of full angiosperm transpiration. Although higher water use efficiency is usually associated with plants with lower transpiration rates, water use efficiency actually increases with higher hydraulic capacity in our simulations as a result of the higher humidity and, thus, lower vapor pressure gradient between the intercellular air space within the leaf and the external atmosphere. We speculate that the high transpirational capacity of angiosperms played a significant role in the expansion of tropical rain forest.

  6. Transpiration And Regenerative Cooling Of Rocket Engine

    NASA Technical Reports Server (NTRS)

    Obrien, Charles J.

    1989-01-01

    Transpiration cooling extends limits of performance. Addition of transpiration cooling to regeneratively-cooled rocket-engine combustion chamber proposed. Modification improves performance of engine by allowing use of higher chamber pressure. Throat section of combustion-chamber wall cooled by transpiration, while chamber and nozzle sections cooled by fluid flowing in closed channels. Concept applicable to advanced, high-performance terrestrial engines or some kinds of industrial combustion chambers. With proper design, cooling scheme makes possible to achieve higher chamber pressure and higher overall performance in smaller engine.

  7. Resistance to Water Flow in the Sorghum Plant 1

    PubMed Central

    Meyer, Wayne S.; Ritchie, Joe T.

    1980-01-01

    Knowledge of the location and magnitude of the resistance to water flow in a plant is fundamental for describing whole plant response to water stress. The reported magnitudes of these resistances vary widely, principally because of the difficulty of measuring water potential within the plant. A number of interrelated experiments are described in which the water potential of a covered, nontranspiring leaf attached to a transpiring sorghum plant (Sorghum bicolor [L.] Moench) was used as a measure of the potential at the root-shoot junction. This allowed a descriptive evaluation of plant resistance to be made. The water potentials of a covered, nontranspiring leaf and a nonabsorbing root in solution, both attached to an otherwise actively transpiring and absorbing plant, were found to be similar. This supported the hypothesis that covered leaf water potential was equilibrating at a point shared by the vascular connections of both leaves and roots, i.e. the nodal complex of the root-shoot junction or crown. The difference in potential between a covered and exposed leaf together with calculated individual leaf transpiration rates were used to evaluate the resistance between the plant crown and the exposed leaf lamina called the connection resistance. There was an apparent decrease in the connection resistance as the transpiration rate increased; this is qualitatively explained as plant capacitance. Assuming that the covered leaf water potential was equal to that in the root xylem at the point of water absorption in the experimental plants with relatively short root axes, calculated radial root resistances were strongly dependent on the transpiration rate. For plants with moderate to high transpiration rates the roots had a slightly larger resistance than the shoots. PMID:16661138

  8. Transpiration characteristics of forests and shrubland under land cover change within the large caldera of Mt. Aso, Japan

    NASA Astrophysics Data System (ADS)

    Miyazawa, Y.; Inoue, A.; Maruyama, A.

    2013-12-01

    Grassland within a caldera of Mt. Aso has been maintained for fertilizer production from grasses and cattle feeding. Due to the changes in the agricultural and social structure since 1950's, a large part of the grassland was converted to plantations or abandoned to shrublands. Because vegetations of different plant functional types differ in evapotranspiration; ET, a research project was launched to examine the effects of the ongoing land use change on the ET within the caldera, and consequently affect the surface and groundwater discharge of the region. As the part of the project, transpiration rate; E of the major 3 forest types were investigated using sap flow measurements. Based on the measured data, stomatal conductance; Gs was inversely calculated and its response to the environmental factors was modeled using Jarvis-type equation in order to estimate ET of a given part of the caldera based on the plant functional type and the weather data. The selected forests were conifer plantation, deciduous broadleaved plantation and shrubland, which were installed with sap flow sensors to calculate stand-level transpiration rate. Sap flux; Js did not show clear differences among sites despite the large differences in sapwood area. In early summer solar radiation was limited to low levels due to frequent rainfall events and therefore, Js was the function of solar radiation rather than other environmental factors, such as vapor pressure deficit and soil water content. Gs was well regressed with the vapor pressure deficit and solar radiation. The estimated E based on Gs model and the weather data was 0.3-1.2 mm day-1 for each site and was comparable to the E of grassland in other study sites. Results suggested that transpiration rate in growing was not different between vegetations but its annual value are thought to differ due to the different phenology.

  9. Transpiring wall supercritical water oxidation reactor salt deposition studies

    SciTech Connect

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

    1996-09-01

    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.

  10. Uptake rate of nitrogen dioxide by potato plants

    SciTech Connect

    Sinn, J.P.; Pell, E.J.; Kabel, R.L.

    1984-06-01

    Greenhouse-grown potato plants were exposed to nitrogen dioxide in an exposure chamber to determine the rate of NO/sub 2/ uptake at concentrations from 228 to 817 ..mu..g/m/sup 3/ (0.12-0.43 ppm). Results show that a consistent increase in uptake rate accompanied an increase in NO/sub 2/ exposure concentrations. Exposure in the range of concentration had no significant effect on leaf diffusive resistance.

  11. 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...

  12. Improvements in plant growth rate using underwater discharge

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  13. Relationships between xylem anatomy, root hydraulic conductivity, leaf/root ratio and transpiration in citrus trees on different rootstocks.

    PubMed

    Rodríguez-Gamir, Juan; Intrigliolo, Diego S; Primo-Millo, Eduardo; Forner-Giner, M Angeles

    2010-06-01

    The aim of the study was to determine the extent in which leaf and whole plant transpiration (Tp) were influenced by root hydraulic conductance (K(r)), leaf to root ratio and leaf mass. Also, the relationships between the anatomic characteristics of roots and K(r) were investigated. To this end, 9-month-old seedlings of the citrus rootstocks Cleopatra mandarin (CM), Poncirus trifoliata (PT), and their hybrids Forner-Alcaide no 5 (FA-5) and Forner-Alcaide no 13 (FA-13) and 15-month-old trees of Valencia orange budded on these four rootstocks were tested. The hybrid FA-13 and PT had higher values of K(r) and leaf transpiration rates (E) than FA-5 and CM. There was a positive curvilinear correlation between E and K(r). Furthermore, E levels in the different types of plants decreased with increased leaf/root (L/R) ratios. Pruning of the roots and defoliation confirmed that transpiration rates were strongly influenced by the L/R ratio. However, variations in E because of differences in L/R ratios were less pronounced in trees budded on FA-13 and PT than on the other two rootstocks. In addition, there was a positive correlation between Tp and leaf biomass, although differences between rootstocks may be attributed to differences in K(r). The average lumen diameter of xylem vessels was greater in rootstocks with high K(r). Size of epidermal and hypodermal cells of fibrous roots may also restrict K(r). PMID:20088906

  14. Global transpiration, recharge and runoff tracked with stable isotopes

    NASA Astrophysics Data System (ADS)

    Jasechko, S.

    2015-12-01

    The transformations of precipitation into soil-, ground- or stream-water constitute fundamental components of the hydrologic cycle. Hydrometric data are well suited to track propagations of pressures through the landscape, but tell us little about the transport of water itself. Conversely, isotopic data track movements of molecules, providing quantitative insights into subsurface processes. This presentation reviews recent uses of isotopic data to quantify the velocity, storage and mixing of precipitation as it flushes into plants (1. transpiration), aquifers (2. recharge) and streams (3. runoff). (1) Plant transpiration comprises the largest flux of fresh water from the continents, exceeding global river flows by a factor of ~1.5. Mounting evidence suggests that water used by plants is poorly connected to water flowing into streams and aquifers, contrasting most earth system model parameterizations. (2) This partitioning of precipitation into "blue" (recharge, runoff) and "green" (transpiration) water storages is further evidenced by relating precipitation and groundwater isotope contents. Global precipitation-groundwater isotope data show that snowmelt pulses (extratropics) and intensive rainfall (tropics) lead to disproportionately large groundwater recharge fluxes—that is, recharge/precipitation ratios exceeding the local annual average. Across the low latitudes, these results mean that the ongoing intensification of precipitation brought on by global warming may serve to promote groundwater recharge in the tropics, where, by 2050, half of the world's population is projected to live. (3) This presentation concludes by relating precipitation and streamflow isotope contents to show that ~1/3 of global river discharges are generated by precipitation that reaches the stream in less than 3 months (i.e., "young water" in rivers). Substantial and pervasive young, month(s)-old water in global rivers means that biogeochemical processes taking place in the critical

  15. Mycorrhizal response trades off with plant growth rate and increases with plant successional status.

    PubMed

    Koziol, Liz; Bever, James D

    2015-07-01

    Early-successional plant species invest in rapid growth and reproduction in contrast to slow growing late-successional species. We test the consistency of "trade-offs between plant life history and responsiveness on arbuscular mycorrhizal fungi. We selected four very early-, seven early-, 11 middle-, and eight late-successional plant species from six different families and functional groups and grew them with and without a mixed fungal inoculum and compared root architecture, mycorrhizal responsiveness, and plant growth rate. Our results indicate mycorrhizal responsiveness increases with plant successional stage and that this effect explains more variation in mycorrhizal response than is explained by phylogenetic relatedness. The mycorrhizal responsiveness of individual plant species was positively correlated with mycorrhizal root infection and negatively correlated with average plant mass and the number of root tips per unit mass, indicating that both plant growth rate and root architecture trade off with investment in mycorrhizal mutualisms. Because late-successional plants are very responsive to mycorrhizal fungi, our results suggest that fungal community dynamics may be an important driver of plant succession. PMID:26378299

  16. Effect of plants on sunspace passive solar heating

    SciTech Connect

    Best, E.D.; McFarland, R.D.

    1985-01-01

    The effect of plants on sunspace thermal performance is investigated, based on experiments done in Los Alamos using two test rooms with attached sunspaces, which were essentially identical except for the presence of plants in one. Performance is related to plant transpiration, evaporation from the soil, condensation on the glazing and the absorbtance of solar energy by the lightweight leaves. Performance effects have been quantified by measurements of auxiliary heat consumption in the test rooms and analyzed by means of energy balance calculations. A method for estimating the transpiration rate is presented.

  17. Effect of different densities of the twospotted spider mite Tetranychus urticae on CO2 assimilation, transpiration, and stomatal behaviour in rose leaves.

    PubMed

    Landeros, J; Guevara, L P; Badii, M H; Flores, A E; Pámanes, A

    2004-01-01

    The effect of population density of Tetranychus urticae Koch on CO2 assimilation, transpiration and stomatal behaviour in rose leaves and on the diameter and length of stems and flower buds was investigated under greenhouse conditions. The investigation was performed in order to gain more insight into integrated control systems in rose crops grown under greenhouse conditions. Physiological processes, such as photosynthesis and transpiration, as well as stomatal behaviour and chlorophyll content, were studied as they form part of the plant's nutrition mechanism and therefore affect the quantity and quality of the flowers. Information related to the effect of spider mite population density on bloom quality, diameter and length of stems and flower buds was also collected. The data indicate that increased mite density coincides with a decrease in the net photosynthetic rate, transpiration and chlorophyll content. Higher mite densities on leaves cause stomata to remain open for longer periods, which allows a greater loss of water. Spider mite densities of 10 and 50 mites per leaf cause a reduction in flower stem length of 17 and 26%, respectively, as compared to plants with no mites present. PMID:15139084

  18. Transpiration from forest dwelling and woodland Mygalomorphae (Araneae)

    NASA Astrophysics Data System (ADS)

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

    1983-03-01

    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.

  19. Transpiration by trees under seasonal water logging and drought in monsoon central Cambodia

    NASA Astrophysics Data System (ADS)

    Miyazawa, Y.; Tateishi, M.; Kajisa, T.; Ma, V.; Heng, S.; Kumagai, T.; Mizoue, N.

    2012-04-01

    Cambodia is situated in the center of Indochina Peninsula and experiences severe drought for 5 months of dry season and subsequent rainy season. Around the Tonlesap Lake where both natural and secondary forests exist without intensive destruction by human activity, forest hydrology is characterized by seasonal water logging in mid rainy season. Tree- and stand-scale transpiration is thought to be influenced by the changing soil water conditions and trees' site-specific adaptation to the environment, but less is measured about transpiration and leaf ecophysiological traits in this region. The objectives of this study is to reveal the ecophysiology of the two native (Dipterocarpus obtusifolius and Shorea roxburghii) and two exotic species (Acacia auriculiformis and Eucalyptus camaldulensis) and to detect the effects of soil water conditions on day to week scale transpiration in mid rainy and dry season. Seasonal leaf-level photosynthesis measurements suggested that photosynthetic capacity (Vcmax25) showed no clear seasonal change in each species without clear interspecific variation. Two native species had stomatal control in response to the environment different from previous studies and showed stomatal conductance higher than most woody species in other seasonal tropical forests, suggesting the species- and site-specific adaptation to the easy access to the ground water. Sap flow rate per leaf area was expressed in two parameters: measured transpiration rate based on the continuous sap flow measurements (Esap) and modeled transpiration rate (Emod) using a multilayer model based on the measured data of atmospheric environments, radiation and the leaf ecophysiological traits. Esap was lower in rainy season than those in dry season, with short but pronounced drop near the end of the dry season, although Emod was higher in rainy season than in dry season. In dry season, Emod well fit the diurnal and day to day trend of Esap, suggesting that soil drought did not limit

  20. Transpiration and canopy conductance variations of shelterbelt in an arid inland river basin of northwest China

    NASA Astrophysics Data System (ADS)

    Gao, G.

    2015-12-01

    The knowledge of plant water use characteristics under changing environmental conditions is essential for ecosystem management and water resources distribution in water-stressed environments. This study was conducted to quantify variations in transpiration and canopy conductance in a shelterbelt in the middle of the Heihe River Basin, China. Sap flow of eight Gansu Poplar trees (Populus gansuensis) with different diameters at breast height (DBH) was measured over three consecutive growing seasons (2012-2014). The evapotranspiration of groundwater via plant use was estimated by the White method, with diurnal water table fluctuations. Results showed that mean sap flow density varied between 30.62 ±11.44 and 101.88 ±28.98 kg m-2 h-1, and it increased linearly with the DBH. Variations of sap flow density were mainly controlled by meteorological factors in addition to water table depth. Average stand transpiration during the growing season was about 4.85 mm day-1, and it had a logarithmic relationship with reference crop evapotranspiration. Precipitation increased stand transpiration, but not at a statistically significant level (p>0.05). The recharge of soil water by irrigation significantly accelerated stand transpiration (p<0.05). Stand transpiration and canopy conductance increased by 27% and 31%, respectively, when soil water conditions changed from dry to wet. Canopy conductance decreased logarithmically with vapor pressure deficit, whereas there was no apparent relationship between canopy conductance and solar radiation. The sensitivity of canopy conductance to vapor pressure deficit decreased under dry soil conditions. Groundwater evapotranspiration (0.6-7.1 mm day-1) was linearly correlated with stand transpiration (1.1-6.5 mm day-1) (R2 = 0.71). During the drought period, approximately 80% of total stand transpiration came from groundwater evapotranspiration. This study highlighted the critical role of irrigation and groundwater for shelterbelts, and might

  1. Variable coupling between sap-flow and transpiration in pine trees under drought conditions

    NASA Astrophysics Data System (ADS)

    Preisler, Yakir; Tatarinov, Fyodor; Rohatyn, Shani; Rotenberg, Eyal; Grunzweig, Jose M.; Yakir, Dan

    2016-04-01

    Changes in diurnal patterns in water transport and physiological activities in response to changes in environmental conditions are important adjustments of trees to drought. The rate of sap flow (SF) in trees is expected to be in agreement with the rate of tree-scale transpiration (T) and provides a powerful measure of water transport in the soil-plant-atmosphere system. The aim of this five-years study was to investigate the temporal links between SF and T in Pinus halepensis exposed to extreme seasonal drought in the Yatir forest in Israel. We continuously measured SF (20 trees), the daily variations in stem diameter (ΔDBH, determined with high precision dendrometers; 8 trees), and ecosystem evapotranspiration (ET; eddy covariance), which were complemented with short-term campaigns of leaf-scale measurements of H2O and CO2 gas exchange, water potentials, and hydraulic conductivity. During the rainy season, tree SF was well synchronized with ecosystem ET, reaching maximum rates during midday in all trees. However, during the dry season, the daily SF trends greatly varied among trees, allowing a classification of trees into three classes: 1) Trees that remain with SF maximum at midday, 2) trees that advanced their SF peak to early morning, and 3) trees that delayed their SF peak to late afternoon hours. This classification remained valid for the entire study period (2010-2015), and strongly correlated with tree height and DBH, and to a lower degree with crown size and competition index. In the dry season, class 3 trees (large) tended to delay the timing of SF maximum to the afternoon, and to advance their maximum diurnal DBH to early morning, while class 2 trees (smaller) advanced their SF maximum to early morning and had maximum daily DBH during midday and afternoon. Leaf-scale transpiration (T), measurements showed a typical morning peak in all trees, irrespective of classification, and a secondary peak in the afternoon in large trees only. Water potential and

  2. Wind increases "evaporative demand" but reduces plant water requirements

    NASA Astrophysics Data System (ADS)

    Schymanski, S. J.; Or, D.

    2015-12-01

    Transpiration is commonly conceptualised as a fraction of some potential rate, determined by stomatal or canopy resistance. Therefore, so-called "atmospheric evaporative demand" or "potential evaporation" is generally used alongside with precipitation and soil moisture to characterise the environmental conditions that affect plant water use. An increase in potential evaporation (e.g. due to climate change) is generally believed to cause increased transpiration and/or vegetation water stress, aggravating drought effects. In the present study, we investigated the question whether potential evaporation constitutes a meaningful reference for transpiration and compared sensitivity of potential evaporation and leaf transpiration to atmospheric forcing. Based on modelling results and supporting experimental evidence, we conclude that stomatal resistance cannot be parameterised as a factor relating transpiration to potential evaporation, as the ratio between transpiration and potential evaporation not only varies with stomatal resistance, but also with wind speed, air temperature, irradiance and relative humidity. Furthermore, the effect of wind speed in particular implies increase in potential evaporation, which is commonly interpreted as increased "water stress", but at the same time can reduce leaf transpiration, implying a decrease in water demand at the leaf scale. In fact, in a range of field measurements, we found that water use efficiency (WUE, carbon uptake per water transpired) commonly increases with increasing wind speed, enabling plants to conserve water during photosynthesis. We estimate that the observed global decrease in terrestrial near-surface wind speeds could have reduced WUE at a magnitude similar to the increase in WUE attributed to global rise in atmospheric carbon dioxide concentrations. We conclude that trends in wind speed and atmospheric carbon dioxide concentrations have to be considered explicitly for the estimation of drought effects on

  3. Disentangling effects of vector birth rate, mortality rate, and abundance on spread of a plant pathogen

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For insect-transmitted plant pathogens, rates of pathogen spread are a function of vector abundance. While vector abundance is recognized to be important, parameters that govern vector population size receive little attention. For example, epidemiological models often fix vector population size by a...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  5. Coupling gross primary production and transpiration for a consistent estimate of canopy water use efficiency

    NASA Astrophysics Data System (ADS)

    Yebra, Marta; van Dijk, Albert

    2015-04-01

    Water use efficiency (WUE, the amount of transpiration or evapotranspiration per unit gross (GPP) or net CO2 uptake) is key in all areas of plant production and forest management applications. Therefore, mutually consistent estimates of GPP and transpiration are needed to analysed WUE without introducing any artefacts that might arise by combining independently derived GPP and ET estimates. GPP and transpiration are physiologically linked at ecosystem level by the canopy conductance (Gc). Estimates of Gc can be obtained by scaling stomatal conductance (Kelliher et al. 1995) or inferred from ecosystem level measurements of gas exchange (Baldocchi et al., 2008). To derive large-scale or indeed global estimates of Gc, satellite remote sensing based methods are needed. In a previous study, we used water vapour flux estimates derived from eddy covariance flux tower measurements at 16 Fluxnet sites world-wide to develop a method to estimate Gc using MODIS reflectance observations (Yebra et al. 2013). We combined those estimates with the Penman-Monteith combination equation to derive transpiration (T). The resulting T estimates compared favourably with flux tower estimates (R2=0.82, RMSE=29.8 W m-2). Moreover, the method allowed a single parameterisation for all land cover types, which avoids artefacts resulting from land cover classification. In subsequent research (Yebra et al, in preparation) we used the same satellite-derived Gc values within a process-based but simple canopy GPP model to constrain GPP predictions. The developed model uses a 'big-leaf' description of the plant canopy to estimate the mean GPP flux as the lesser of a conductance-limited and radiation-limited GPP rate. The conductance-limited rate was derived assuming that transport of CO2 from the bulk air to the intercellular leaf space is limited by molecular diffusion through the stomata. The radiation-limited rate was estimated assuming that it is proportional to the absorbed photosynthetically

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

    NASA Astrophysics Data System (ADS)

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

    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 μL CO 2 L -1, 24/17°C (population A); 700 μL CO 2 L -1, 24/17°C (population B) and 700 μL 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

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

    NASA Technical Reports Server (NTRS)

    Holden, Michael S.

    1994-01-01

    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

  8. Cross-scale modelling of transpiration from stomata via the leaf boundary layer

    PubMed Central

    Defraeye, Thijs; Derome, Dominique; Verboven, Pieter; Carmeliet, Jan; Nicolai, Bart

    2014-01-01

    Background and Aims Leaf transpiration is a key parameter for understanding land surface–climate interactions, plant stress and plant structure–function relationships. Transpiration takes place at the microscale level, namely via stomata that are distributed discretely over the leaf surface with a very low surface coverage (approx. 0·2–5 %). The present study aims to shed more light on the dependency of the leaf boundary-layer conductance (BLC) on stomatal surface coverage and air speed. Methods An innovative three-dimensional cross-scale modelling approach was applied to investigate convective mass transport from leaves, using computational fluid dynamics. The gap between stomatal and leaf scale was bridged by including all these scales in the same computational model (10−5–10−1 m), which implies explicitly modelling individual stomata. Key Results BLC was strongly dependent on stomatal surface coverage and air speed. Leaf BLC at low surface coverage ratios (CR), typical for stomata, was still relatively high, compared with BLC of a fully wet leaf (hypothetical CR of 100 %). Nevertheless, these conventional BLCs (CR of 100 %), as obtained from experiments or simulations on leaf models, were found to overpredict the convective exchange. In addition, small variations in stomatal CR were found to result in large variations in BLCs. Furthermore, stomata of a certain size exhibited a higher mass transfer rate at lower CRs. Conclusions The proposed cross-scale modelling approach allows us to increase our understanding of transpiration at the sub-leaf level as well as the boundary-layer microclimate in a way currently not feasible experimentally. The influence of stomatal size, aperture and surface density, and also flow-field parameters can be studied using the model, and prospects for further improvement of the model are presented. An important conclusion of the study is that existing measures of conductances (e.g. from artificial leaves) can be

  9. Cyclic Variations in Nitrogen Uptake Rate of Soybean Plants 1

    PubMed Central

    Henry, Leslie Tolley; Raper, C. David

    1989-01-01

    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. PMID:11537458

  10. Relating xylem cavitation to transpiration in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Acoustic emmisions (AEs) from xylem cavitation events are characteristic of transpiration processes. Even though a body of work employing AE exists with a large number of species, cotton and other agronomically important crops have either not been investigated, or limited information exists. A few s...

  11. SEWAGE DISPOSAL BY EVAPORATION-TRANSPIRATION

    EPA Science Inventory

    One of the methods for on-site disposal of wastewater from individual homes is by evaporation. Two types of evaporative disposal systems have been investigated in this study; evapo-transpiration (ET) beds and mechanical evaporation units. Twenty nine test lysimeters of 0.22 cubic...

  12. Riparian buffer transpiration and watershed scale impacts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Forested riparian buffers are prevalent throughout the Southeastern Coastal Plain Region of the United States (US). Because they make up a significant portion of the regional landscape, transpiration within these riparian buffers is believed to have an important impact on the hydrologic budget of r...

  13. Make Your Own Transpiring Tree

    ERIC Educational Resources Information Center

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

    2003-01-01

    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…

  14. The stem heat balance method to measure transpiration:Evaluation of a new sensor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The direct measurement of crop transpiration (Tcrop) under field conditions and throughout the growing season is difficult to obtain. An available method uses stem flow gauge sensors, based on the stem heat balance. The sensor consists of a small heater that is wrapped around the stem of the plant a...

  15. Free convection over a vertical porous plate with transpiration

    NASA Technical Reports Server (NTRS)

    Parikh, P. G.; Moffat, R. J.; Kays, W. M.; Bershader, D.

    1974-01-01

    The problem of free convection over an isothermal vertical porous plate with transpiration is studied both numerically and experimentally. Numerical solutions to the variable-property transpired free-convection boundary layer equations have been obtained using the finite difference procedure of Patankar and Spalding (1967). The effects of uniform transpiration on heat transfer and on temperature and velocity profiles are predicted. Interferometrically measured nondimensional temperature profiles for the uniform wall temperature and transpiration case agreed closely with these numerical predictions.

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

    NASA Astrophysics Data System (ADS)

    Gong, Daozhi; Kang, Shaozhong; Zhang, Jianhua

    2005-08-01

    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.

  17. Active microbreak effects on musculoskeletal comfort ratings in meatpacking plants.

    PubMed

    Genaidy, A M; Delgado, E; Bustos, T

    1995-02-01

    This study was conducted to examine whether a system of active microbreaks can reduce the discomfort perceived by employees in a meatpacking plant. Moreover, the relationship between the discomfort perceived on the job and musculoskeletal capability was investigated. Twenty-eight men employed in a local meatpacking plant participated in a study conducted over a period of four weeks. Results indicated that active microbreaks significantly reduced the level of discomfort perceived by employees during the course of the working day. The subjective ratings of perceived discomfort correlated significantly with anthropometric, strength and background information (R2 = 0.66). The physical characteristics of Caucasian employees were higher than those of their Hispanic counterparts. Moreover, the physical characteristics of meatpacking employees were significantly lower than those reported in the literature for employees engaged in manual handling tasks. PMID:7895738

  18. Mercaptan removal rate exceeds 99% at Canadian gas plant

    SciTech Connect

    Judd, B. )

    1993-08-16

    Installation of a Selexol solvent unit at Pembina Resources Ltd.'s Diamond Valley gas plant has been effective in polishing mercaptans and other sulfur-bearing compounds from a variable gas stream. The actual removal rate exceeds 99%, and an absolute treated gas target of < 100 ppm total sulfur is maintained. In addition, hydrocarbon pick up is restricted sufficiently so that slugs of hydrocarbon are not carried through the system to destabilize incineration of the mercaptans. The paper discusses start-up problems, the gas treating process, mercaptans in the feed gas, the solvent unit, and its operation.

  19. Photosynthesis and transpiration of loblolly pine seedlings as influenced by moisture-stress conditioning

    SciTech Connect

    Seiler, J.R.; Johnson, J.D.

    1985-01-01

    One-yr-old seedlings were exposed to 8 wk of moisture stress conditioning (MSC); seedlings were watered only when pre-dawn needle water potential fell below -1.4 MPa. Water was then withheld and photosynthesis and transpiration rates recorded. Photosynthesis in well-watered controls and MSC seedlings was reduced to zero in 12 and 17 days respectively. Seedlings were harvested and water use efficiency calculated using photosynthesis and transpiration data; it was expressed as mg of CO/sub 2/ fixed per g of water lost. Seedlings exposed to MSC continued to photosynthesize to much lower needle water potentials. This response is at least partly attributed to the significant decrease (0.45 MPa) in needle osmotic potential found in MSC seedlings, which were able to maintain turgor to lower needle water potentials. Transpiration rate decreased 30% and water use efficiency increased 67% as a result of MSC. 26 references.

  20. Transpired Air Collectors - Ventilation Preheating

    SciTech Connect

    Christensen, C.

    2006-06-22

    Many commercial and industrial buildings have high ventilation rates. Although all that fresh air is great for indoor air quality, heating it can be very expensive. This short (2-page) fact sheet describes a technology available to use solar energy to preheat ventilation air and dramatically reduce utility bills.

  1. 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...

  2. Transpiration characteristics of a rubber plantation in central Cambodia.

    PubMed

    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

    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

  3. A New Method to Quantify the Isotopic Signature of Leaf Transpiration: Implications for Landscape-Scale Evapotranspiration Partitioning Studies

    NASA Astrophysics Data System (ADS)

    Wang, L.; Good, S. P.; Caylor, K. K.

    2010-12-01

    Characterizing the constituent components of evapotranspiration is crucial to better understand ecosystem-level water budgets and water use dynamics. Isotope based evapotranspiration partitioning methods are promising but their utility lies in the accurate estimation of the isotopic composition of underlying transpiration and evaporation. Here we report a new method to quantify the isotopic signature of leaf transpiration under field conditions. This method utilizes a commercially available laser-based isotope analyzer and a transparent leaf chamber, modified from Licor conifer leaf chamber. The method is based on the water mass balance in ambient air and leaf transpired air. We verified the method using “artificial leaves” and glassline extracted samples. The method provides a new and direct way to estimate leaf transpiration isotopic signatures and it has wide applications in ecology, hydrology and plant physiology.

  4. Processes driving nocturnal transpiration and implications for estimating land evapotranspiration.

    PubMed

    de Dios, Víctor Resco; Roy, Jacques; Ferrio, Juan Pedro; Alday, Josu G; Landais, Damien; Milcu, Alexandru; Gessler, Arthur

    2015-01-01

    Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12-23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51-98 vs. 7-8 mm yr(-1)). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake. PMID:26074373

  5. Processes driving nocturnal transpiration and implications for estimating land evapotranspiration

    NASA Astrophysics Data System (ADS)

    de Dios, Víctor Resco; Roy, Jacques; Ferrio, Juan Pedro; Alday, Josu G.; Landais, Damien; Milcu, Alexandru; Gessler, Arthur

    2015-06-01

    Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12-23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51-98 vs. 7-8 mm yr-1). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake.

  6. Processes driving nocturnal transpiration and implications for estimating land evapotranspiration

    PubMed Central

    de Dios, Víctor Resco; Roy, Jacques; Ferrio, Juan Pedro; Alday, Josu G.; Landais, Damien; Milcu, Alexandru; Gessler, Arthur

    2015-01-01

    Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12–23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51–98 vs. 7–8 mm yr−1). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake. PMID:26074373

  7. Disentangling Effects of Vector Birth Rate, Mortality Rate, and Abundance on Spread of Plant Pathogens.

    PubMed

    Sisterson, Mark S; Stenger, Drake C

    2016-04-01

    Models on the spread of insect-transmitted plant pathogens often fix vector population size by assuming that deaths are offset by births. Although such mathematical simplifications are often justified, deemphasizing parameters that govern vector population size is problematic, as reproductive biology and mortality schedules of vectors of plant pathogens receive little empirical attention. Here, the importance of explicitly including parameters for vector birth and death rates was evaluated by comparing results from models with fixed vector population size with models with logistic vector population growth. In fixed vector population size models, increasing vector mortality decreased percentage of inoculative vectors, but had no effect on vector population size, as deaths were offset by births. In models with logistic vector population growth, increasing vector mortality decreased percentage of inoculative vectors and decreased vector population size. Consequently, vector mortality had a greater effect on pathogen spread in models with logistic vector population growth than in models with fixed vector population size. Further, in models with logistic vector population growth, magnitude of vector birth rate determined time required for vector populations to reach large size, thereby determining when pathogen spread occurred quickly. Assumptions regarding timing of vector mortality within a time step also affected model outcome. A greater emphasis of vector entomologists on studying reproductive biology and mortality schedules of insect species that transmit plant pathogens will facilitate identification of conditions associated with rapid growth of vector populations and could lead to development of novel control strategies. PMID:26637536

  8. Transpiration in the Global Water Cycle

    NASA Astrophysics Data System (ADS)

    Schlesinger, W. H.; Jasechko, S.

    2014-12-01

    A compilation of 81 studies that have partitioned evapotranspiration (ET) into its components—transpiration (T) and evaporation (E)—at the ecosystem scale indicates that T accounts for 61% (±15% s.d.) of ET and returns approximately 39±10% of incident precipitation (P) to the atmosphere, creating a dominant force in the global water cycle. T as a proportion of ET is highest in tropical rainforests (70±14 %) and lowest in steppes, shrublands and deserts (51±15%), but there is no relationship of T/ET versus P across all available data (R2 = 0.01). Changes to transpiration due to increasing CO2 concentrations, land use changes, shifting ecozones and climate warming are expected to have significant impacts upon runoff and groundwater recharge, reflecting human impacts on the global biogeochemical cycle of water.

  9. 78 FR 78352 - Plant-E Corp; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Plant-E Corp; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket Section 204 Authorization This is a supplemental notice in the above-referenced proceeding, of Plant-E...

  10. Transpiration efficiency of a tropical pioneer tree (Ficus insipida) in relation to soil fertility.

    PubMed

    Cernusak, Lucas A; Winter, Klaus; Aranda, Jorge; Turner, Benjamin L; Marshall, John D

    2007-01-01

    The response of whole-plant water-use efficiency, termed transpiration efficiency (TE), to variation in soil fertility was assessed in a tropical pioneer tree, Ficus insipida Willd. Measurements of stable isotope ratios (delta(13)C, delta(18)O, delta(15)N), elemental concentrations (C, N, P), plant growth, instantaneous leaf gas exchange, and whole-plant water use were used to analyse the mechanisms controlling TE. Plants were grown individually in 19 l pots with non-limiting soil moisture. Soil fertility was altered by mixing soil with varying proportions of rice husks, and applying a slow release fertilizer. A large variation was observed in leaf photosynthetic rate, mean relative growth rate (RGR), and TE in response to experimental treatments; these traits were well correlated with variation in leaf N concentration. Variation in TE showed a strong dependence on the ratio of intercellular to ambient CO(2) mole fractions (c(i)/c(a)); both for instantaneous measurements of c(i)/c(a) (R(2)=0.69, P <0.0001, n=30), and integrated estimates based on C isotope discrimination (R(2)=0.88, P <0.0001, n=30). On the other hand, variations in the leaf-to-air humidity gradient, unproductive water loss, and respiratory C use probably played only minor roles in modulating TE in the face of variable soil fertility. The pronounced variation in TE resulted from a combination of the strong response of c(i)/c(a) to leaf N, and inherently high values of c(i)/c(a) for this tropical tree species; these two factors conspired to cause a 4-fold variation among treatments in (1-c(i)/c(a)), the term that actually modifies TE. Results suggest that variation in plant N status could have important implications for the coupling between C and water exchange in tropical forest trees. PMID:18057036

  11. 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...

  12. Functional magnetic resonance imaging in intact plants--quantitative observation of flow in plant vessels.

    PubMed

    Kuchenbrod, E; Kahler, E; Thürmer, F; Deichmann, R; Zimmermann, U; Haase, A

    1998-04-01

    Quantitative magnetic resonance (MR) images of flow velocities in intact corn plants were acquired using magnetization-prepared MR microscopy. A phase contrast flow imaging technique was used to quantitate water flow velocities and total volume flow rates in small xylem vessels. The simultaneous measurement of the transpiration of the whole plant was achieved by using a closed climate chamber within the MR magnet. The total volume flow rate and the transpiration values were in close correlation. Functional magnetic resonance imaging in intact plants was performed by light stimulation of the transpiration inside of the magnet. The change in the flow velocities in the xylem vessels of single vascular bundles was in correlation with the changes in the transpiration. Significant differences were observed between the xylem vessels in different vascular bundles. Furthermore, flow velocity measurements were performed on excised plant stems and visualized by the uptake of the MR contrast agent, gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). A comparison between the phase contrast flow imaging and the contrast media uptake showed to be in good agreement with each other. PMID:9621974

  13. Transpired Solar Collector at NREL's Waste Handling Facility Uses Solar Energy to Heat Ventilation Air

    SciTech Connect

    2010-09-08

    The transpired solar collector was installed on NREL's Waste handling Facility (WHF) in 1990 to preheat ventilation air. The electrically heated WHF was an ideal candidate for the this technology - requiring a ventilation rate of 3,000 cubic feet per meter to maintain safe indoor conditions.

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

    NASA Technical Reports Server (NTRS)

    Holden, M. S.; Rodriguez, K. M.; Nowak, R. J.

    1991-01-01

    Experimental studies are conducted to examine the utilization of transpiration cooling to reduce the peak-heating loads in areas of shock/shock interaction. Smooth and transpiration-cooled nosetip models, 12 inches in diameter, were employed in these studies, which focused on defining the pressure distributions and heat transfer in type III and IV interaction areas. Transpiration cooling was determined to significantly increase the size of the shock layer and to move the peak-heating point around the body. A transpiration-cooling rate of more than 30 percent of the freestream maximum flux did not lower the peak-heating level more than 10 percent, but the integrated heating loads were reduced.

  15. Advanced control strategy for plant heat rate improvement

    SciTech Connect

    Schultz, P.; Frerichs, D.K.; Kyr, D.

    1995-12-31

    Florida Power & Light Company (FPL) supplies electricity to about half of the population of Florida, roughly 6.5 million people. The load base is largely residential/business with the obvious seasonal extremes due to the climate. FPL`s generating capacity is 16,320 MW composed of 70% traditional fossil cycle, 18% nuclear, and 12% gas turbine. The system load profile coupled with bulk power purchases is such that the 400 MW class units (9 Foster Wheeler drum type units comprising 24% of total capacity) are now forced to cycle daily all year, and to come off line on weekends during the winter months. The current economic realities of power generation force utility companies to seek methods to improve plant heat rate, and FPL is no exception. FPL believed it possible to achieve the goal of lower heat rate and follow the required load demand with the 400 MW class units through the use of an advanced control strategy implemented totally within the unit`s Distributed Control System (DCS). As of the writing of this paper, the project is still ongoing. This paper will present the theory and methodology of the advanced control strategy along with the current design and implementation status and results obtained to date.

  16. Modelling orange tree root water uptake active area by minimally invasive ERT data and transpiration measurements

    NASA Astrophysics Data System (ADS)

    Vanella, Daniela; Boaga, Jacopo; Perri, Maria Teresa; Consoli, Simona; Cassiani, Giorgio

    2015-04-01

    The comprehension of the hydrological processes involving plant root dynamics is crucial for implementing water saving measures in agriculture. This is particular urgent in areas, like those Mediterranean, characterized by scarce water availability. The study of root water dynamics should not be separated from a more general analysis of the mass and energy fluxes transferred in the soil-plant-atmosphere continuum. In our study, in order to carry this inclusive approach, minimal invasive 3D time-lapse electrical resistivity tomography (ERT) for soil moisture estimation was combined with plant transpiration fluxes directly measured with Sap Flow (SF) techniques and Eddy Covariance methods, and volumetric soil moisture measurements by TDR probes. The main objective of this inclusive approach was to accurately define root-zone water dynamics and individuate the root-area effectively active for water and nutrient uptake process. The monitoring was carried out in Eastern Sicily (south Italy) in summers 2013 and 2014, within an experimental orange orchard farm. During the first year of experiment (October 2013), ERT measurements were carried out around the pertinent volume of one fully irrigated tree, characterized by a vegetation ground cover of 70%; in the second year (June 2014), ERT monitoring was conducted considering a cutting plant, thus to evaluate soil water dynamics without the significant plant transpiration contribution. In order to explore the hydrological dynamics of the root zone volume surrounded by the monitored tree, the resistivity data acquired during the ERT monitoring were converted into soil moisture content distribution by a laboratory calibration based on the soil electrical properties as a function of moisture content and pore water electrical conductivity. By using ERT data in conjunction with the agro-meteorological information (i.e. irrigation rates, rainfall, evapotranspiration by Eddy Covariance, transpiration by Sap Flow and soil moisture

  17. Do root hydraulic properties change during the early vegetative stage of plant development in barley (Hordeum vulgare)?

    PubMed Central

    Suku, Shimi; Knipfer, Thorsten; Fricke, Wieland

    2014-01-01

    Background and Aims As annual crops develop, transpirational water loss increases substantially. This increase has to be matched by an increase in water uptake through the root system. The aim of this study was to assess the contributions of changes in intrinsic root hydraulic conductivity (Lp, water uptake per unit root surface area, driving force and time), driving force and root surface area to developmental increases in root water uptake. Methods Hydroponically grown barley plants were analysed during four windows of their vegetative stage of development, when they were 9–13, 14–18, 19–23 and 24–28 d old. Hydraulic conductivity was determined for individual roots (Lp) and for entire root systems (Lpr). Osmotic Lp of individual seminal and adventitious roots and osmotic Lpr of the root system were determined in exudation experiments. Hydrostatic Lp of individual roots was determined by root pressure probe analyses, and hydrostatic Lpr of the root system was derived from analyses of transpiring plants. Key Results Although osmotic and hydrostatic Lp and Lpr values increased initially during development and were correlated positively with plant transpiration rate, their overall developmental increases (about 2-fold) were small compared with increases in transpirational water loss and root surface area (about 10- to 40-fold). The water potential gradient driving water uptake in transpiring plants more than doubled during development, and potentially contributed to the increases in plant water flow. Osmotic Lpr of entire root systems and hydrostatic Lpr of transpiring plants were similar, suggesting that the main radial transport path in roots was the cell-to-cell path at all developmental stages. Conclusions Increase in the surface area of root system, and not changes in intrinsic root hydraulic properties, is the main means through which barley plants grown hydroponically sustain an increase in transpirational water loss during their vegetative

  18. Inferring dominant controls on transpiration across a hillslope transect from ecohydrological measurements and thermodynamic limits

    NASA Astrophysics Data System (ADS)

    Renner, Maik; Hassler, Sibylle; Blume, Theresa; Weiler, Markus; Hildebrandt, Anke; Guderle, Marcus; Schymanki, Stan; Kleidon, Axel

    2015-04-01

    hillslopes and stand characteristics were found to be the major long term control: the south-facing sites with larger atmospheric demand show significantly lower sensitivity to atmospheric demand than the north-facing sites. Interestingly, we find that the sensitivity is decreasing with stand density, which is markedly different between the contrasting hillslopes. Thus periodical water limitation induced by larger absorption of solar radiation on the south-facing slopes may have led to long term plant adaptation or forest management strategies which satisfy the trade-off between highly variable atmospheric demand and the depletion of soil water storage. In summary, the strong linear link of daily transpiration to atmospheric demand as well as the more long-term adaptation to soil moisture availability may allow for the spatially explicit prediction of forest transpiration from solar radiation, temperature and stand characteristics.

  19. Phylogenetic and ecological patterns in nighttime transpiration among five members of the genus Rubus co-occurring in western Oregon

    PubMed Central

    McNellis, Brandon; Howard, Ava R

    2015-01-01

    Nighttime transpiration is a substantial portion of ecosystem water budgets, but few studies compare water use of closely related co-occurring species in a phylogenetic context. Nighttime transpiration can range up to 69% of daytime rates and vary between species, ecosystem, and functional type. We examined leaf-level daytime and nighttime gas exchange of five species of the genus Rubus co-occurring in the Pacific Northwest of western North America in a greenhouse common garden. Contrary to expectations, nighttime transpiration was not correlated to daytime water use. Nighttime transpiration showed pronounced phylogenetic signals, but the proportion of variation explained by different phylogenetic groupings varied across datasets. Leaf osmotic water potential, water potential at turgor loss point, stomatal size, and specific leaf area were correlated with phylogeny but did not readily explain variation in nighttime transpiration. Patterns in interspecific variation as well as a disconnect between rates of daytime and nighttime transpiration suggest that variation in nighttime water use may be at least partly driven by genetic factors independent of those that control daytime water use. Future work with co-occurring congeneric systems is needed to establish the generality of these results and may help determine the mechanism driving interspecific variation in nighttime water use. PMID:26380686

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

    NASA Astrophysics Data System (ADS)

    Mitra, B.; Papuga, S. A.

    2012-12-01

    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 (θ) 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

  1. Dominant controls of transpiration along a hillslope transect inferred from ecohydrological measurements and thermodynamic limits

    NASA Astrophysics Data System (ADS)

    Renner, Maik; Hassler, Sibylle K.; Blume, Theresa; Weiler, Markus; Hildebrandt, Anke; Guderle, Marcus; Schymanski, Stanislaus J.; Kleidon, Axel

    2016-05-01

    We combine ecohydrological observations of sap flow and soil moisture with thermodynamically constrained estimates of atmospheric evaporative demand to infer the dominant controls of forest transpiration in complex terrain. We hypothesize that daily variations in transpiration are dominated by variations in atmospheric demand, while site-specific controls, including limiting soil moisture, act on longer timescales. We test these hypotheses with data of a measurement setup consisting of five sites along a valley cross section in Luxembourg. Both hillslopes are covered by forest dominated by European beech (Fagus sylvatica L.). Two independent measurements are used to estimate stand transpiration: (i) sap flow and (ii) diurnal variations in soil moisture, which were used to estimate the daily root water uptake. Atmospheric evaporative demand is estimated through thermodynamically constrained evaporation, which only requires absorbed solar radiation and temperature as input data without any empirical parameters. Both transpiration estimates are strongly correlated to atmospheric demand at the daily timescale. We find that neither vapor pressure deficit nor wind speed add to the explained variance, supporting the idea that they are dependent variables on land-atmosphere exchange and the surface energy budget. Estimated stand transpiration was in a similar range at the north-facing and the south-facing hillslopes despite the different aspect and the largely different stand composition. We identified an inverse relationship between sap flux density and the site-average sapwood area per tree as estimated by the site forest inventories. This suggests that tree hydraulic adaptation can compensate for heterogeneous conditions. However, during dry summer periods differences in topographic factors and stand structure can cause spatially variable transpiration rates. We conclude that absorption of solar radiation at the surface forms a dominant control for turbulent heat and

  2. Thermal transpiration: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    T, Joe Francis; Sathian, Sarith P.

    2014-12-01

    Thermal transpiration is a phenomenon where fluid molecules move from the cold end towards the hot end of a channel under the influence of longitudinal temperature gradient alone. Although the phenomenon of thermal transpiration is observed at rarefied gas conditions in macro systems, the phenomenon can occur at atmospheric pressure if the characteristic dimensions of the channel is less than 100 nm. The flow through these nanosized channels is characterized by the free molecular flow regimes and continuum theory is inadequate to describe the flow. Thus a non-continuum method like molecular dynamics (MD) is necessary to study such phenomenon. In the present work, MD simulations were carried out to investigate the occurance of thermal transpiration in copper and platinum nanochannels at atmospheric pressure conditions. The mean pressure of argon gas confined inside the nano channels was maintained around 1 bar. The channel height is maintained at 2nm. The argon atoms interact with each other and with the wall atoms through the Lennard-Jones potential. The wall atoms are modelled using an EAM potential. Further, separate simulations were carried out where a Harmonic potential is used for the atom-atom interaction in the platinum channel. A thermally insulating wall was introduced between the low and high temperature regions and those wall atoms interact with fluid atoms through a repulsive potential. A reduced cut off radius were used to achieve this. Thermal creep is induced by applying a temperature gradient along the channel wall. It was found that flow developed in the direction of the increasing temperature gradient of the wall. An increase in the volumetric flux was observed as the length of the cold and the hot regions of the wall were increased. The effect of temperature gradient and the wall-fluid interaction strength on the flow parameters have been studied to understand the phenomenon better.

  3. Thermal transpiration: A molecular dynamics study

    SciTech Connect

    T, Joe Francis; Sathian, Sarith P.

    2014-12-09

    Thermal transpiration is a phenomenon where fluid molecules move from the cold end towards the hot end of a channel under the influence of longitudinal temperature gradient alone. Although the phenomenon of thermal transpiration is observed at rarefied gas conditions in macro systems, the phenomenon can occur at atmospheric pressure if the characteristic dimensions of the channel is less than 100 nm. The flow through these nanosized channels is characterized by the free molecular flow regimes and continuum theory is inadequate to describe the flow. Thus a non-continuum method like molecular dynamics (MD) is necessary to study such phenomenon. In the present work, MD simulations were carried out to investigate the occurance of thermal transpiration in copper and platinum nanochannels at atmospheric pressure conditions. The mean pressure of argon gas confined inside the nano channels was maintained around 1 bar. The channel height is maintained at 2nm. The argon atoms interact with each other and with the wall atoms through the Lennard-Jones potential. The wall atoms are modelled using an EAM potential. Further, separate simulations were carried out where a Harmonic potential is used for the atom-atom interaction in the platinum channel. A thermally insulating wall was introduced between the low and high temperature regions and those wall atoms interact with fluid atoms through a repulsive potential. A reduced cut off radius were used to achieve this. Thermal creep is induced by applying a temperature gradient along the channel wall. It was found that flow developed in the direction of the increasing temperature gradient of the wall. An increase in the volumetric flux was observed as the length of the cold and the hot regions of the wall were increased. The effect of temperature gradient and the wall-fluid interaction strength on the flow parameters have been studied to understand the phenomenon better.

  4. Heat exchanger with transpired, highly porous fins

    DOEpatents

    Kutscher, Charles F.; Gawlik, Keith

    2002-01-01

    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.

  5. Night-time transpiration can decrease hydraulic redistribution.

    PubMed

    Howard, Ava R; van Iersel, Marc W; Richards, James H; Donovan, Lisa A

    2009-08-01

    C(3) plants dominate many landscapes and are critically important for ecosystem water cycling. At night, plant water losses can include transpiration (E(night)) from the canopy and hydraulic redistribution (HR) from roots. We tested whether E(night) 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. HR was initiated by briefly withholding all water, followed by watering only one rooting compartment. Under study conditions, all species showed substantial E(night) and HR (highest minus lowest soil water potential [Psi(s)] during a specified diel period). Suppressing E(night) by canopy bagging increased HR during the nightly bagging period (HR(N)) for A. tridentata and H. anomalus by 73 and 33% respectively, but did not affect HR(N) by Q. laevis. Total daily HR (HR(T)) was positively correlated with the Psi(s) gradient between the rooting compartments, which was correlated with light and/or atmospheric vapour pressure deficit (VPDa) the prior day. For A. tridentata, HR(T) was negatively correlated with night-time VPDa. Ecological implications of the impact of E(night) on HR may include decreased plant productivity during dry seasons, altered ecosystem water flux patterns and reduced nutrient cycling in drying soils. PMID:19422615

  6. Lattice Boltzmann approach to thermal transpiration

    SciTech Connect

    Sofonea, Victor

    2006-11-15

    Diffuse reflection boundary conditions are introduced in a thermal lattice Boltzmann model to allow for variable fluid density and temperature along the walls. The capability of this model to capture the main characteristics of the thermal transpiration phenomenon in a box at nonvanishing Knudsen numbers is demonstrated. The thermal creep velocity is found to be proportional to the temperature gradient imposed at the wall, whereas the accuracy of the simulation results are found to be of first or second order, depending on the numerical scheme.

  7. Simultaneous viscous-inviscid coupling via transpiration

    SciTech Connect

    Yiu, K.F.C.; Giles, M.B.

    1995-09-01

    In viscous-inviscid coupling analysis, the direct coupling technique and the inverse coupling technique are commonly adopted. However, stability and convergence of the algorithms derived are usually very unsatisfactory. Here, by using the transpiration technique to simulate the effect of the displacement thickness, a new simultaneous coupling method is derived. The integral boundary layer equations and the full potential equation are chosen to be the viscous-inviscid coupled system. After discretization, the Newton-Raphson technique is proposed to solve the coupled nonlinear system. Several numerical results are used to demonstrate the accuracy and efficiency of the proposed method. 15 refs., 23 figs.

  8. 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...

  9. Responses of shelterbelt stand transpiration to drought and groundwater variations in an arid inland river basin of Northwest China

    NASA Astrophysics Data System (ADS)

    Shen, Qin; Gao, Guangyao; Fu, Bojie; Lü, Yihe

    2015-12-01

    Plant water use characteristics and transpiration responses under dry conditions are considered essential for effective and sustainable ecosystem management in arid areas. This study was conducted to evaluate the response of shelterbelt stand transpiration to precipitation, soil drought and groundwater variations in an oasis-desert ecotone in the middle of the Heihe River Basin, China. Sap flow was measured in eight Gansu Poplar trees (Populus Gansuensis) with different diameter at breast height over three consecutive growing seasons (2012-2014). The groundwater evapotranspiration via plant use was estimated by the White method with diurnal water table fluctuations. The results showed that precipitation increased the stand transpiration but not statistically significant (paired t-test, p > 0.05). The recharge of soil water by irrigation caused stand transpiration acceleration significantly (t-test, p < 0.05). Stand transpiration and canopy conductance increased by 27% and 31%, respectively, when soil water conditions changed from dry to wet. Canopy conductance decreased logarithmically with vapor pressure deficit, while there was no apparent relationship between canopy conductance and solar radiation. The sensitivity of canopy conductance to vapor pressure deficit decreased under dry soil conditions. Groundwater evapotranspiration (0.6-7.1 mm day-1) was linearly correlated with stand transpiration (1.1-6.5 mm day-1) (R2 = 0.71), and these two variables had similar variability. During the drought period, approximately 80% of total stand transpiration came from groundwater evapotranspiration. This study highlighted the critical role of irrigation and groundwater for shelterbelt, and might provide the basis for the development of water requirement schemes for shelterbelt growth in arid inland river basins.

  10. Desiccant cooling using unglazed transpired solar collectors

    NASA Astrophysics Data System (ADS)

    Pesaran, A. A.; Wipke, K.

    1992-05-01

    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 percent more than that required for the glazed collector, the cost of the unglazed collector array was 44 percent 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.