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1

Stem and Leaf Plot  

NSDL National Science Digital Library

This site, created by Michelle Lacey of Yale University, gives a definition and an example of stem and leaf plots. The author helps to explain how these graphs are used, and in what fields and/or disciplines. Even though brief, this is still a valuable reference item for anyone interested in statistics.

Lacey, Michelle

2009-11-23

2

LEAF: A Microcomputer Program for Constructing the Tukey Stem and Leaf Graph.  

ERIC Educational Resources Information Center

This paper presents a BASIC microcomputer program that constructs the Tukey (1977) stem and leaf graph. Options within the LEAF program include a modified stem and leaf where the stem is split and a parallel stem and leaf graph where two separate sets of data are displayed from a common stem. (Author)

Pascale, Pietro J.; Smith, Joseph

1986-01-01

3

Student practice reading Stem-and-Leaf Plots  

NSDL National Science Digital Library

Using the same methods and approach, each pair could just write out the data as a Stem-and-Leaf Plot after they were testing the amount of water. Pairs could then provide their data (as a Stem-and-Leaf Plot) to another group and that new group would have to write out list of numbers and then find the mean, median, and mode. This group could then also create the box-and-whisker plot, or there could be a trade with a third group and have that one do the box-and-whisker plot while checking the work of others.

2012-04-04

4

Stem and leaf morphoanatomy of Maytenus ilicifolia.  

PubMed

Maytenus ilicifolia is a woody medicinal plant, employed mainly for its antiulcerogenic properties. The stem and leaf morphoanatomy has been studied, aiming to supply knowledge for the pharmacognostic and taxonomic species identification. The vegetative material was fixed, freehand sectioned and stained according to usual microtechniques. The stem organization, in secondary growth, shows periderm beneath the remaining epidermis, conspicuous sclerenchymatic ring in the cortex and cambium forming phloem outside and xylem inside. The leaf is simple, alternate and lanceolate and has sparsely spiny teeth along the margin. Epidermal cells containing calcium oxalate crystals, thick cuticle that forms cuticular flanges, dorsiventral mesophyll and amphicrival bundle in the midrib and petiole are observed. PMID:15664461

Duarte, M R; Debur, M C

2005-01-01

5

[Pharmacognostical studies on the stem and leaf of Chinese Alyxia].  

PubMed

About the stem and leaf of Chinese alyxia, pharmacognostical studies on the character, microscopical and physichemical aspects are made, The results are certifed that the methods of determination on the character and microscopical may be adopt for stem and leaf Chinese alyxia. There are a rich amino acids and trace elements. It provide scientific basis for its comprehensive development and utilization. PMID:12572443

Zhang, G; Zhang, L; Tanaka, T; Takada, A

1997-03-01

6

Structure and enzymatic accessibility of leaf and stem from wheat straw before and after hydrothermal pretreatment  

PubMed Central

Background Biomass recalcitrance is affected by a number of chemical, physical and biological factors. In this study we looked into the differences in recalcitrance between two major anatomical fractions of wheat straw biomass, leaf and stem. A set of twenty-one wheat cultivars was fractionated and illustrated the substantial variation in leaf-to-stem ratio between cultivars. The two fractions were compared in terms of chemical composition, enzymatic convertibility, cellulose crystallinity and glucan accessibility. The use of water as a probe for assessing glucan accessibility was explored using low field nuclear magnetic resonance and infrared spectroscopy in combination with hydrogen-deuterium exchange. Results Leaves were clearly more degradable by lignocellulolytic enzymes than stems, and it was demonstrated that xylose removal was more linked to glucose yield for stems than for leaves. Comparing the locations of water in leaf and stem by low field NMR and FT-IR revealed that the glucan hydroxyl groups in leaves were more accessible to water than glucan hydroxyl groups in stems. No difference in crystallinity between leaf and stem was observed using wide angle x-ray diffraction. Hydrothermal pretreatment increased the accessibility towards water in stems but not in leaves. The results in this study indicate a correlation between the accessibility of glucan to water and to enzymes. Conclusions Enzymatic degradability of wheat straw anatomical fractions can be indicated by the accessibility of the hydroxyl groups to water. This suggests that water may be used to assess glucan accessibility in biomass samples.

2014-01-01

7

A Stem-Leaf Plot: An Approach to Statistics.  

ERIC Educational Resources Information Center

A method of organizing data known as a stem-leaf plot is presented in detail. This method is viewed to overcome many of the disadvantages associated with the traditional methods of grouping in the frequency distribution table and provides a convenient introduction to data organization. (MP)

MacDonald, A. D.

1982-01-01

8

Leaf Spot and Stem Rot on Wilford Swallowwort Caused by Stemphylium lycopersici in Korea  

PubMed Central

In June 2012, leaf spot and stem rot were observed on Wilford Swallowwort plants grown in Cheonan, Korea. Three fungal isolates obtained from the diseased leaves and stems were identified as Stemphylium lycopersici, based on morphological, cultural, and molecular characteristics and pathogenicity. This is the first report of leaf spot and stem rot on Wilford Swallowwort caused by S. lycopersici.

Choi, Hyo Won; Lee, Young Kee; Shim, Hong Sik; Lee, Sang Yeob

2012-01-01

9

Coordination between leaf and stem traits related to leaf carbon gain and hydraulics across 32 drought-tolerant angiosperms.  

PubMed

We examined 15 traits in leaves and stems related to leaf C economy and water use for 32 co-existing angiosperms at ridge sites with shallow soil in the Bonin Islands. Across species, stem density was positively correlated to leaf mass per area (LMA), leaf lifespan (LLS), and total phenolics and condensed tannins per unit leaf N (N-based), and negatively correlated to leaf osmotic potential and saturated water content in leaves. LMA and LLS were negatively correlated to photosynthetic parameters, such as area-, mass-, and N-based assimilation rates. Although stem density and leaf osmotic potential were not associated with photosynthetic parameters, they were associated with some parameters of the leaf C economy, such as LMA and LLS. In the principal component (PCA) analysis, the first three axes accounted for 74.4% of total variation. Axis 1, which explained 41.8% of the total variation, was well associated with parameters for leaf C and N economy. Similarly, axis 2, which explained 22.3% of the total variation, was associated with parameters for water use. Axis 3, which explained 10.3% of the total variation, was associated with chemical defense within leaves. Axes 1 and 2 separated functional types relatively well, i.e., creeping trees, ruderal trees, other woody plants, C(3) shrubs and forbs, palms, and CAM plants, indicating that plant functional types were characterized by similar attributes of traits related to leaf C and N economy and water use. In addition, when the plot was extended by two unrelated traits, leaf mass-based assimilation rates and stem density, it also separated these functional types. These data indicate that differences in the functional types with contrasting plant strategies can be attributed to functional integration among leaf C economy, hydraulics, and leaf longevity, and that both leaf mass-based assimilation rates and stem density are key factors reflecting the different functions of plant species. PMID:18297313

Ishida, Atsushi; Nakano, Takashi; Yazaki, Kenichi; Matsuki, Sawako; Koike, Nobuya; Lauenstein, Diego L; Shimizu, Michiru; Yamashita, Naoko

2008-05-01

10

Correlation of leaf chlorophyll readings and stem nitrate concentrations in peppermint  

Microsoft Academic Search

The SPAD chlorophyll meter appears promising for rapid, on?farm analysis of crop nitrogen (N) status. Leaf SPAD chlorophyll levels have been correlated with total leaf N concentrations, but it has not been determined how they relate to other widely applied N diagnoses such as petiole or stem nitrate (NO3) analysis. Our objective was to examine the relationship between leaf SPAD

M. P. Westcott; J. M. Wraith

1995-01-01

11

Metal accumulation in intertidal litter through decomposing leaf blades, sheaths and stems of Phragmites australis.  

PubMed

Metal contents of decomposing leaf blades, leaf sheaths and stems of common reed (Phragmites australis) were monitored by a litter bag method on the sediment of an intertidal brackish marsh in the Scheldt estuary (The Netherlands). On monthly intervals, two litter bags were retrieved from the marsh during 9 months for both leaf blades and sheaths and during 16 months for stems. All samples were dried, weighed and analysed for ash and Cd, Cu, Cr, Ni, Pb and Zn contents. Most concentrations increased considerably during the decomposition. Generally, also a very important net metal inflow into the litter bags could be observed. The inflow was highest for leaf blades. High correlations between ash contents and metal concentrations for leaf blades suggest that the increase of leaf blade metal contents can be due to physicochemical sorption of dissolved metals and an important infiltration of mud particles, which were not removed by rinsing the leaf blades with distilled water preceding the analyses. For stems, smaller amounts of inflowing ash and even outflowing ash amounts were found, which suggests that inflow of inorganic particles is not the major factor determining metal accumulation by stems on medium term. Ergosterol concentrations in stem tissue however proved to be correlated with metal contents, which suggests a significant role of fungal litter colonizers in metal accumulation. For leaf sheaths, the effects of physicochemical sorption, infiltration of mud particles and incorporation by microbial litter colonizers do not seem to be as pronounced as for stems and leaf blades. PMID:16330074

Du Laing, Gijs; Van Ryckegem, Gunther; Tack, Filip M G; Verloo, Marc G

2006-06-01

12

Apparatus and methods for amplification of blood stem cell numbers  

US Patent & Trademark Office Database

The present invention provides an apparatus and methods for expansion of hematopoietic stem cell numbers. The stem cells are cultured and differentiated cells and endogenous growth factors are removed (depleted), permitting long term culture and expansion of the stem cells. The hematopoietic stem cells are used in numerous therapeutic procedures.

2010-09-14

13

Measurement of stem content for control purposes in a green leaf threshing plant  

NASA Astrophysics Data System (ADS)

The purpose of a green leaf threshing (GLT) plant is to separate the tobacco leaf from the stem. In the GLT process, there are over a dozen parameters to adjust for optimal performance. The current laboratory measurement technique is destructive, laborious and not as well suited for optimizing processing parameters as an on-line technique. A machine vision technique was developed to non-destructively measure the amount of stem in the stream of processed tobacco leaf. The machine vision technique employs novel lighting to collect images and image processing to measure the amount of stem in the image. The image processing combines fuzzy logic and unique morphological image processing to extract the leaf from the background and then the stem present in the leaf. Performance of the optical technique compared favorably with the lab method. Correlation coefficient (R2) was greater than 0.95 and relative error (%RSD) was less than 6%.

Thompson, Bruce T.

2002-02-01

14

First Report of Myrothecium roridum Causing Leaf and Stem Rot Disease on Peperomia quadrangularis in Korea  

PubMed Central

In 2010, symptoms of leaf and stem rot were observed on potted plants (Peperomia quadrangularis) in a greenhouse in Yongin, Korea. The causative pathogen was identified as Myrothecium roridum based on morphological data, internal transcribed spacer sequence analysis, and pathogenicity test. To our knowledge, this is the first report of M. roridum causing leaf and stem rot disease on P. quadrangularis in Korea and elsewhere worldwide.

Han, Kyung-Sook; Choi, Seung-Kook; Kim, Hyeong-Hwan; Lee, Sung-Chan; Park, Jong-Han; Cho, Myoung-Rae

2014-01-01

15

Stem hydraulic traits and leaf water-stress tolerance are co-ordinated with the leaf phenology of angiosperm trees in an Asian tropical dry karst forest  

PubMed Central

Background and Aims The co-occurring of evergreen and deciduous angiosperm trees in Asian tropical dry forests on karst substrates suggests the existence of different water-use strategies among species. In this study it is hypothesized that the co-occurring evergreen and deciduous trees differ in stem hydraulic traits and leaf water relationships, and there will be correlated evolution in drought tolerance between leaves and stems. Methods A comparison was made of stem hydraulic conductivity, vulnerability curves, wood anatomy, leaf life span, leaf pressure–volume characteristics and photosynthetic capacity of six evergreen and six deciduous tree species co-occurring in a tropical dry karst forest in south-west China. The correlated evolution of leaf and stem traits was examined using both traditional and phylogenetic independent contrasts correlations. Key Results It was found that the deciduous trees had higher stem hydraulic efficiency, greater hydraulically weighted vessel diameter (Dh) and higher mass-based photosynthetic rate (Am); while the evergreen species had greater xylem-cavitation resistance, lower leaf turgor-loss point water potential (?0) and higher bulk modulus of elasticity. There were evolutionary correlations between leaf life span and stem hydraulic efficiency, Am, and dry season ?0. Xylem-cavitation resistance was evolutionarily correlated with stem hydraulic efficiency, Dh, as well as dry season ?0. Both wood density and leaf density were closely correlated with leaf water-stress tolerance and Am. Conclusions The results reveal the clear distinctions in stem hydraulic traits and leaf water-stress tolerance between the co-occurring evergreen and deciduous angiosperm trees in an Asian dry karst forest. A novel pattern was demonstrated linking leaf longevity with stem hydraulic efficiency and leaf water-stress tolerance. The results show the correlated evolution in drought tolerance between stems and leaves.

Fu, Pei-Li; Jiang, Yan-Juan; Wang, Ai-Ying; Brodribb, Tim J.; Zhang, Jiao-Lin; Zhu, Shi-Dan; Cao, Kun-Fang

2012-01-01

16

Complementary patterns of stiffness in stem and leaf sheaths of Triticale  

Microsoft Academic Search

The variation in the stiffness of stem and leaf sheaths along the shoot axis of Triticale (Triticosecale W., cv. Jago) was examined, using an ultrasonic method, at two stages of development, (i) at the stage of high stem mechanical instability when upper internodes are forming (heading), and (ii) at milk maturity when development of strengthening tissues is completed (three weeks

Jacek ?ebrowski

1992-01-01

17

Cajan leaf combined with bone marrow-derived mesenchymal stem cells for the treatment of osteonecrosis of the femoral head  

PubMed Central

The aim of the present study was to observe the curative effect of traditional Chinese cajan leaves, combined with administration of bone marrow-derived mesenchymal stem cells (BMSCs), on osteonecrosis of the femoral head (ONFH) in rats and to investigate the underlying mechanisms. A total of 40 rat ONFH models were established through liquid nitrogen freezing and were subsequently divided into groups: A, control; B, treated with cajan leaf; C, treated with BMSCs and D, treated with cajan leaf combined with BMSCs. Samples were obtained 30 days following treatment, and immunohistochemical staining of vascular endothelial growth factor (VEGF) and image analysis were performed. Chondrocytes and vascular endothelial cells were stained as a result of immunohistochemical staining and group D exhibited markedly deeper staining, and a significantly larger number of stained cells, compared with group A. Thus, in the present study, cajan leaf combined with BMSCs was shown to promote VEGF expression and improve ONFH repair.

SHI, DA; SUN, YINDI; YIN, JICHAO; FAN, XIAOCHEN; DUAN, HONGHAO; LIU, NA; HE, WEI

2014-01-01

18

[Pharmacognostical identification on the stem and leaf of Humulus scandens].  

PubMed

In this paper, pharmacognostiacal identification of Humulus scandens was studied. The character of medicinal materials, histological and powder characteristics for the setem and leaf of H. scandens were mainly reported. The microscopical features for leaf is typical identified basis. PMID:12569675

Zhang, Q; Zhang, K; Liu, X; Zeng, X

1998-12-01

19

Comparative proteomics of leaf, stem, and root tissues of synthetic Brassica napus.  

PubMed

Comparative proteomics was applied to three vegetative organs of Brassica napus, the leaf, stem, and root using 2-DE. Among the >1600 analyzed spots, 43% were found to be common to all three organs, suggesting the existence of a "basal" or ubiquitous proteome composed of housekeeping proteins. The green organs, leaf, and stem, were closely related (approximately 80% common spots) while the root displayed more organ-specific polypeptides (approximately 10%). Reference maps were established using MS, allowing the identification of 93, 385, and 266 proteins in leaf, stem, and root proteomes, respectively. Bioinformatic analyses were also performed; in silico functional categorization and cellular localization allow obtaining a precise picture of the cell molecular network within vegetative organs. These proteome maps can be explored using the PROTICdb software at the following address: http://bioinformatique.moulon.inra.fr/proticdb/web_view/. PMID:19132686

Albertin, Warren; Langella, Olivier; Joets, Johann; Négroni, Luc; Zivy, Michel; Damerval, Catherine; Thiellement, Hervé

2009-02-01

20

Correlated evolution of stem and leaf hydraulic traits in Pereskia (Cactaceae).  

PubMed

Recent studies have demonstrated significant correlations between stem and leaf hydraulic properties when comparing across species within ecological communities. This implies that these traits are co-evolving, but there have been few studies addressing plant water relations within an explicitly evolutionary framework. This study tests for correlated evolution among a suite of plant water-use traits and environmental parameters in seven species of Pereskia (Cactaceae), using phylogenetically independent contrasts. There were significant evolutionary correlations between leaf-specific xylem hydraulic conductivity, Huber Value, leaf stomatal pore index, leaf venation density and leaf size, but none of these traits appeared to be correlated with environmental water availability; only two water relations traits - mid-day leaf water potentials and photosynthetic water use efficiency - correlated with estimates of moisture regime. In Pereskia, it appears that many stem and leaf hydraulic properties thought to be critical to whole-plant water use have not evolved in response to habitat shifts in water availability. This may be because of the extremely conservative stomatal behavior and particular rooting strategy demonstrated by all Pereskia species investigated. These results highlight the need for a lineage-based approach to understand the relative roles of functional traits in ecological adaptation. PMID:17083678

Edwards, Erika J

2006-01-01

21

Comparison of sodium carbonate pretreatment for enzymatic hydrolysis of wheat straw stem and leaf to produce fermentable sugars.  

PubMed

The specific characteristics of biomass structure and chemical composition of straw stem and leaf may result in different behavior of pretreatment and enzymatic hydrolysis. In this work, sodium carbonate (SC) was employed as a pretreatment to improve the enzymatic digestibility of wheat straw. The chemical composition and enzymatic hydrolysis of wheat straw stem and leaf (sheath included) were investigated comparatively. Most of the polysaccharides are kept in the solid fractions after SC pretreatment, while the stem has better delignification selectivity than leaf at high temperature. The enzymatic hydrolysis efficiency of wheat straw leaf is significantly higher than that of stem. The maximum total sugar yield from SC pretreated leaf was about 16% higher than stem. The results show that sodium carbonate is of great potential to be used as a pretreatment for the production of bioethanol from straw handling waste in a straw pulp mill with a low feedstock cost. PMID:23587832

Jin, Yongcan; Huang, Ting; Geng, Wenhui; Yang, Linfeng

2013-06-01

22

Acute and subacute toxicity of Cassia occidentalis L. stem and leaf in Wistar rats  

Microsoft Academic Search

Ethnopharmacological relevanceCassia occidentalis L. (syn. Senna occidentalis; Leguminosae) has been used as natural medicine in rainforests and tropical regions as laxative, analgesic, febrifuge, diuretic, hepatoprotective, vermifuge and colagogo. Herein, we performed a pre-clinical safety evaluation of hydroalcoholic extract of Cassia occidentalis stem and leaf in male and female Wistar rats.

Mirtes G. B. Silva; Ticiana P. Aragão; Carlos F. B. Vasconcelos; Pablo A. Ferreira; Bruno A. Andrade; Igor M. A. Costa; João H. Costa-Silva; Almir G. Wanderley; Simone S. L. Lafayette

2011-01-01

23

Characters of the leaf and stem morpho-anatomy of Alternanthera brasiliana (L.) O. Kuntze, Amaranthaceae  

Microsoft Academic Search

Alternanthera brasiliana (L.) O. Kuntze, Amaranthaceae is a Brazilian perennial herb employed as analgesic and anti- inflammatory in the traditional medicine. This work has analysed the morpho-anatomy of the leaf and stem, in order to supply knowledge to the medicinal plant identification. The botanical material was fixed, freehand sectioned and stained according to usual microtechniques. The leaves are simple, entire,

Márcia do Rocio Duarte; Maria do Carmo Debur

2004-01-01

24

Correlated evolution of stem and leaf hydraulic traits in Pereskia (Cactaceae)  

Microsoft Academic Search

Summary • Recent studies have demonstrated significant correlations between stem and leaf hydraulic properties when comparing across species within ecological communities. This implies that these traits are co-evolving, but there have been few studies addressing plant water relations within an explicitly evolutionary framework. • This study tests for correlated evolution among a suite of plant water-use traits and environmental parameters

Erika J. Edwards

2006-01-01

25

Antioxidant and anti-dermatophytic properties leaf and stem bark of Xylosma longifolium clos  

PubMed Central

Background The present study was carried out to assess the phytochemical and anti-dermatophytic effect of the leaf and bark extracts of Xylosma longifolium Clos. The leaf and stem bark are used by the indigenous people of Manipur, India for treatment of skin diseases. Methods The leaves and stem barks of Xylosma longifolium were extracted using petroleum ether, chloroform and methanol respectively. The different extracts of each plant parts were tested for antioxidant activity using DPPH assay. The phenolic content was assayed using Folin-Ciocalteu colorimetric method. Each extracts was further analysed by RP-HPLC to quantify some individual flavonoid components. The anti-dermatophytic activity was evaluated both by agar diffusion method and micro wells dilution method against the Microsporum boullardii MTCC 6059, M. canis (MTCC 2820 and MTCC 32700), M. gypseum MTCC 2819, Trichophyton ajelloi MTCC 4878, T. rubrum (MTCC 296 and MTCC 3272). Results The free radical scavenging activity values were ranged from 0.7 to 1.41 mg/ml and 0.6 to 1.23 mg/ml, respectively for leaf and stem bark extracts. The amount of total phenolic contents of the extracts occurred in both leaf and bark in the range of 12 to 56.6 mg GAE/100 g and 16 to 58 mg GAE/100 g respectively. RP-HPLC analysis for flavonoids revealed the presence of two major flavonoid compounds, rutin and catechin. Kaempferol was in trace or absent. Methanol leaf extract showed significant low inhibitory effect against tested fungus Trichophyton ajelloi MTCC 4878 (0.140625 mg/ml) as the most sensitive. These finding suggest that the methanol leaf extract tested contain compounds with antimicrobial properties. Conclusion The results of our study may partially justify the folkloric uses on the plant studied and further provide an evidence that the leaf extract of Xylosma longifolium might be indeed a potential sources of antimicrobial agents.

2013-01-01

26

Protective mechanism of desiccation tolerance in Reaumuria soongorica: leaf abscission and sucrose accumulation in the stem.  

PubMed

Reaumuria soongorica (Pall.) Maxim., a perennial semi-shrub, is widely found in semi-arid areas in northwestern China and can survive severe desiccation of its vegetative organs. In order to study the protective mechanism of desiccation tolerance in R. soongorica, diurnal patterns of net photosynthetic rate (Pn), water use efficiency (WUE) and chlorophyll fluorescence parameters of Photosystem II (PSII), and sugar content in the source leaf and stem were investigated in 6-year-old plants during progressive soil drought imposed by the cessation of watering. The results showed that R. soongorica was characterized by very low leaf water potential, high WUE, photosynthesis and high accumulation of sucrose in the stem and leaf abscission under desiccation. The maximum Pn increased at first and then declined during drought, but intrinsic WUE increased remarkably in the morning with increasing drought stress. The maximal photochemical efficiency of PSII (Fv/Fm) and the quantum efficiency of noncyclic electric transport of PSII (phiPSII) decreased significantly under water stress and exhibited an obvious phenomenon of photoinhibition at noon. Drought stressed plants maintained a higher capacity of dissipation of the excitation energy (measured as NPQ) with the increasing intensity of stress. Conditions of progressive drought promoted sucrose and starch accumulation in the stems but not in the leaves. However, when leaf water potential was less than -21.3 MPa, the plant leaves died and then abscised. But the stem photosynthesis remained and, afterward the plants entered the dormant state. Upon rewatering, the shoots reactivated and the plants developed new leaves. Therefore, R. soongorica has the ability to reduce water loss through leaf abscission and maintain the vigor of the stem cells to survive desiccation. PMID:17393078

Liu, YuBing; Zhang, TengGuo; Li, XingRong; Wang, Gang

2007-02-01

27

DRYING KINETICS OF CORIANDER (Coriandrum sativum) LEAF AND STEM  

Microsoft Academic Search

The drying kinetics of coriander leaves and stems, with or without blanching, was studied at several temperatures (50, 60, 70, and 80 °C) at constant air velocity (1.5 m s -1 ) in a fixed-bed dryer. Three drying models, Henderson and Pabis, Midilli et al., and the Logarithmic, were fitted to the experimental data. According to the results obtained, it

A. S. Silva

2008-01-01

28

Constituents and antimicrobial activity of the essential oils from flower, leaf and stem of Helichrysum armenium.  

PubMed

The chemical constituents from the flower, leaf and stem of Helichrysum armenium DC. (Asteraceae) growing in Iran were obtained by hydrodistillation and analyzed by GC and GC/MS. The oil of flower was characterized by higher amount of limonene (21.2%), alpha-cadinol (18.2%), borneol (11.9%), delta-cadinene (9.0%), bornyl acetate (8.0%) and alpha-humulene (7.3%). Twenty one constituents representing 96.2% of the chromatographical leaf oil were identified of which limonene (29.2%), alpha-pinene (14.4%), caryophyllene oxide (6.5%), alpha-gurjunene (6.3%), bornyl acetate (5.5%) and torreyol (5.2%) were the major components. The main components of the stem oil were limonene (23.6%), alpha-pinene (13.4%), spathulenol (6.4%), alpha-gurjunene (6.3%), caryophyllene oxide (5.3%), bornyl acetate (5.2%), beta-cubebene (4.8%) and delta-cadinene (4.3%). The composition of the oils is different, although the most abundant components are identical in leaf oil (96.2%). The antimicrobial effect of flower, leaf and stem essential oils from Helichrysum armenium was studied according to the agar diffusion cup method. The essential oils had a moderate effect on the Gram-positive and Gram-negative bacteria and had a substantial fungicidal effect on the fungi under study. PMID:22799105

Oji, Khodam-Ali; Shafaghat, Ali

2012-05-01

29

Comparative effects of plant growth regulators on leaf and stem explants of Labisia pumila var. alata  

PubMed Central

Objective: Labisia pumila var. alata, commonly known as ‘Kacip Fatimah’ or ‘Selusuh Fatimah’ in Southeast Asia, is traditionally used by members of the Malay community because of its post-partum medicinal properties. Its various pharmaceutical applications cause an excessive harvesting and lead to serious shortage in natural habitat. Thus, this in vitro propagation study investigated the effects of different plant growth regulators (PGRs) on in vitro leaf and stem explants of L. pumila. Methods: The capabilities of callus, shoot, and root formation were evaluated by culturing both explants on Murashige and Skoog (MS) medium supplemented with various PGRs at the concentrations of 0, 1, 3, 5, and 7 mg/L. Results: Medium supplemented with 3 mg/L indole-3-butyric acid (IBA) showed the optimal callogenesis from both leaf and stem explants with (72.34±19.55)% and (70.40±14.14)% efficacy, respectively. IBA was also found to be the most efficient PGR for root induction. A total of (50.00±7.07)% and (77.78±16.47)% of root formation were obtained from the in vitro stem and leaf explants after being cultured for (26.5±5.0) and (30.0±8.5) d in the medium supplemented with 1 and 3 mg/L of IBA, respectively. Shoot formation was only observed in stem explant, with the maximum percentage of formation ((100.00±0.00)%) that was obtained in 1 mg/L zeatin after (11.0±2.8) d of culture. Conclusions: Callus, roots, and shoots can be induced from in vitro leaf and stem explants of L. pumila through the manipulation of types and concentrations of PGRs.

Ling, Anna Pick Kiong; Tan, Kinn Poay; Hussein, Sobri

2013-01-01

30

Spray drying of Tinospora cordifolia leaf and stem extract and evaluation of antioxidant activity.  

PubMed

Tinospora cordifolia (Guduchi) is widely used in folk medicine/ ayurvedic system of medicine, also in ayurvedic 'Rasayanas' to improve the immune system and used as general tonic, anti-periodic, anti-spasmodic, anti-inflammatory, anti-arthritic and anti-diabetic agent. Numerous studies have been reported on the health benefits of individual parts or whole Guduchi plant. However, most of the work has focused on the extracts of T. cordifolia. In this study, T. cordifolia leaf and stem extract powders were prepared using spray drying at 90 °C outlet temperature of the spray dryer. The powder morphology has also been studied by scanning electron microscopy. The antioxidant activity was followed by DPPH method. The leaf extract powder showed higher retention of antioxidant activity than stem extract powder. PMID:23572835

Sarala, M; Velu, V; Anandharamakrishnan, C; Singh, R P

2012-02-01

31

Stem girdling influences concentrations of endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton  

Microsoft Academic Search

Many studies have shown that root–shoot imbalance influences vegetative growth and development of cotton (Gossypium hirsutum L.), but few have examined changes in leaf senescence and endogenous hormones due to stem girdling. The objective of this\\u000a study was to determine the correlation between some endogenous phytohormones, particularly cytokinins and abscisic acid (ABA),\\u000a and leaf senescence following stem girdling. Field-grown cotton

Jianlong DaiHezhong Dong; Hezhong Dong

32

Toxic effect of stem bark and leaf of Euphorbia hirta plant against freshwater vector snail Lymnaea acuminata  

Microsoft Academic Search

The aqueous stem bark and leaf extracts of plant Euphorbia hirta (family-Euphorbiaceae) have potent molluscicidal activity. Sub-lethal doses (40% and 80% of LC50) of aqueous stem bark and leaf extracts of this plant also significantly (P<0.05) alter the levels of total protein, total free amino acid, nucleic acids (DNA and RNA) and the activity of enzyme protease and acid and

Sunil Kumar Singh; Ram P. Yadav; Sudhanshu Tiwari; Ajay Singh

2005-01-01

33

Copy Number Variant Analysis of Human Embryonic Stem Cells  

Microsoft Academic Search

Differences between individual DNA sequences provide the basis for human genetic variability. Forms of genetic varia- tion include single-nucleotide polymorphisms, insertions\\/du- plications, deletions, and inversions\\/translocations. The ge- nome of human embryonic stem cells (hESCs) has been characterized mainly by karyotyping and comparative genomic hybridization (CGH), techniques whose relatively low resolution at 2-10 megabases (Mb) cannot accurately determine most copy number

Hao Wu; Kevin J. Kim; Kshama Mehta; Salvatore Paxia; Andrew Sundstrom; Thomas Anantharaman; Ali I. Kuraishy; Tri Doan; Jayati Ghosh; April D. Pyle; Amander Clark; William Lowry; Guoping Fan; Tim Baxter; Bud Mishra; Yi Sun; MICHAEL A. TEITELLe

2008-01-01

34

Identification of BFN1, a Bifunctional Nuclease Induced during Leaf and Stem Senescence in Arabidopsis1  

PubMed Central

Nuclease I enzymes are responsible for the degradation of RNA and single-stranded DNA during several plant growth and developmental processes, including senescence. However, in the case of senescence the corresponding genes have not been reported. We describe the identification and characterization of BFN1 of Arabidopsis, and demonstrate that it is a senescence-associated nuclease I gene. BFN1 nuclease shows high similarity to the sequence of a barley nuclease induced during germination and a zinnia (Zinnia elegans) nuclease induced during xylogenesis. In transgenic plants overexpressing the BFN1 cDNA, a nuclease activity of about 38 kD was detected on both RNase and DNase activity gels. Levels of BFN1 mRNA were extremely low or undetectable in roots, leaves, and stems. In contrast, relatively high BFN1 mRNA levels were detected in flowers and during leaf and stem senescence. BFN1 nuclease activity was also induced during leaf and stem senescence. The strong response of the BFN1 gene to senescence indicated that it would be an excellent tool with which to study the mechanisms of senescence induction, as well as the role of the BFN1 enzyme in senescence using reverse genetic approaches in Arabidopsis.

Perez-Amador, Miguel A.; Abler, Michael L.; De Rocher, E. Jay; Thompson, Debrah M.; van Hoof, Ambro; LeBrasseur, Nicole D.; Lers, Amnon; Green, Pamela J.

2000-01-01

35

Antioxidant, antimicrobial activities and fatty acid components of flower, leaf, stem and seed of Hypericum scabrum.  

PubMed

The hexane extracts of flower, leaf, stem, and seed of Hypericum scabrum, which were collected from northwestern Iran, were obtained by extraction in a Soxhlet apparatus. The fatty acids were converted to methyl esters and determined by gas chromatography/flame ionization detector (GC/FID) and gas chromatography/mass spectrometry (GC/MS) systems. The hexane extract from the flower, leaf, stem, and seed contained 39.1%, 43.2%, 29.0%, and 37.6% of omega-3 fatty acids, respectively. The other main components of the flower extract were tetracosane (12.2%) and palmitic acid (9.3%), and that of the leaf extract was palmitic acid (7.4%). The stem and seed extracts contained bis(2-ethylhexyl)phthalate (18.7% and 35.7%), nonacosane (11.7% and 3.9%) and linoleic acid (6.5% and 6.9%) as major components. The hexane extracts of different parts from H. scabrum represent an important source of omega-3 fatty acids in several Hypericum species. The antioxidant activity of all hexane extracts was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method. The results indicate that hexane extracts from different parts of H. scabrum possess considerable antioxidant activity. The highest radical scavenging activity was detected in seed, which had an IC50 = 165 microg/mL. The antimicrobial activity of the extracts of those samples were determined against seven Gram-positive and Gram-negative bacteria (Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, S. epidermidis, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae), as well as three fungi (Candida albicans, Saccharomyces cerevisiae, and Aspergillus niger). The bioassay showed that the oil exhibited moderate antimicrobial activity. This study reveals that the all parts of this plant are attractive sources of fatty acid components, especially the essential ones, as well as of effective natural antioxidants. PMID:22224301

Shafaghat, Ali

2011-11-01

36

Plant regeneration capacity of callus derived from leaf, stem, and root segments of Populus alba L. x P. grandidentata Michx.  

PubMed

Expiants for establishing callus cultures originated from in vitro cultured hybrid poplar (Populus alba L. X P. grandidentata Michx.). Plant regeneration was achieved from established callus cultures derived from stem internodes (SI), leaf discs (LD), and root segments (RS). Shoot regeneration from callus occurred within 4 weeks of culture on most of the media tested. Frequency of shoot formation was greatly increased by subculturing the selected organogenic calli on regeneration media. The highest rate of multiple shoot formation (an average number of 7/SI, 11/LD, and 8/RS) was obtained by using 0.05 ?M IBA in combination with 22.5 ?M 2iP, 22.5 ?M zeatin, and 12.5 ?M 2iP, respectively. Regenerated shoots were easily rooted in polyterra(™) peat plugs in transparent plastic boxes. The rooted plantlets were subsequently transferred to pots containing an artificial potting mix. PMID:24226948

Son, S H; Hall, R B

1990-10-01

37

The estimated impact of fungi on nutrient dynamics during decomposition of Phragmites australis leaf sheaths and stems.  

PubMed

Decomposition of culms (sheaths and stems) of the emergent macrophyte Phragmites australis (common reed) was followed for 16 months in the litter layer of a brackish tidal marsh along the river Scheldt (the Netherlands). Stems and leaf sheaths were separately analyzed for mass loss, litter-associated fungal biomass (ergosterol), nutrient (N and P), and cell wall polymer concentrations (cellulose and lignin). The role of fungal biomass in litter nutrient dynamics was evaluated by estimating nutrient incorporation within the living fungal mass. After 1 year of standing stem decay, substantial fungal colonization was found. This corresponded to an overall fungal biomass of 49 +/- 8.7 mg g(-1) dry mass. A vertical pattern of fungal colonization on stems in the canopy is suggested. The litter bag experiment showed that mass loss of stems was negligible during the first 6 months, whereas leaf sheaths lost almost 50% of their initial mass during that time. Exponential breakdown rates were -0.0039 +/- 0.0004 and -0.0026 +/- 0.0003 day(-1) for leaf sheaths and stems, respectively (excluding the initial lag period). In contrast to the stem tissue--which had no fungal colonization--leaf sheaths were heavily colonized by fungi (93 +/- 10 mg fungal biomass g(-1) dry mass) prior to placement in the litter layer. Once being on the sediment surface, 30% of leaf sheath's associated fungal biomass was lost, but ergosterol concentrations recovered the following months. In the stems, fungal biomass increased steadily after an initial lag period to reach a maximal biomass of about 120 mg fungal biomass g(-1) dry mass for both plant parts at the end of the experiment. Fungal colonizers are considered to contain an important fraction of nutrients within the decaying plant matter. Fungal N incorporation was estimated to be 64 +/- 13 and 102 +/- 15% of total available N pool during decomposition for leaf sheaths and stems, respectively. Fungal P incorporation was estimated to be 37 +/- 9 and 52 +/- 15% of total available P during decomposition for leaf sheaths and stems, respectively. Furthermore, within the stem tissue, fungi are suggested to be active immobilizers of nutrients from the external environment because fungi were often estimated to contain more than 100% of the original nutrient stock. PMID:17006744

Van Ryckegem, G; Van Driessche, G; Van Beeumen, J J; Verbeken, A

2006-10-01

38

Microscopic characters of the leaf and stem of Lavandula dentata L. (Lamiaceae).  

PubMed

Lavandula dentata L. is an aromatic plant used in folk medicine for different purposes and, for this reason, phytochemical surveys have been carried out in the search for bioactive substances aiming to support its uses. Since there is little knowledge on the structural aspects of L. dentata, this work has studied the anatomical characters of the leaf and stem using light and scanning electron microscopy, in order to assist the species identification. As a result, there are different types of trichomes: capitate glandular with uni- or bicellular head, peltate glandular with multicellular head, and branched non-glandular. The leaf is hypostomatic showing diacytic stomata. The epidermis is uniseriate and coated with striate cuticle. The mesophyll is dorsiventral and the midrib is concave-convex and traversed by a single collateral vascular bundle. The stem is quadrangular and has alternating strands of collenchyma and cortical parenchyma as well as a typical endodermis in the cortex. The phloem and xylem cylinders are traversed by narrow rays and there is an incomplete sclerenchymatic sheath adjoining the phloem. These results are a novelty for the species and contribute to distinguish it from other lavenders. Microsc. Res. Tech. 77:647-652, 2014. © 2014 Wiley Periodicals, Inc. PMID:24861363

do Rocio Duarte, Márcia; Carvalho de Souza, Danielle

2014-08-01

39

Relationships between stem number, tuber set and yield of Russet Burbank potatoes  

Microsoft Academic Search

Five storage temperatures and three planting dates were used to obtain differences in seed performance. As seed storage temperature\\u000a increased, average stem number per seed piece significantly increased. Stem number also increased with later planting dates.\\u000a Germination tests, conducted under controlled temperatures, resulted in a curvilinear response with the least stems per seed\\u000a piece at 10°C. a maximum stem number

W. M. Iritani; L. D. Weiler; N. R. Knowles

1983-01-01

40

Evaluations of the methanol extract of Ficus exasperata stem bark, leaf and root for phytochemical analysis and antimicrobial activities  

Microsoft Academic Search

The methanol extract of Ficus exasperata (stem bark, leaf and root) was investigated for activity against some human pathogenic organisms. Phytochemical screening revealed the presence of flavonoids, saponin, tannins, steroids and phlobatannins with no traces of alkaloids and anthraquinones. The results of in vitro antimicrobial screening of the methanol extract exhibited a wide range of activity on Pseudomonas aeruginosa, Salmonella

E. A. Adebayo; O. R. Ishola; O. S. Taiwo; O. N. Majolagbe; B. T. Adekeye

41

Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis.  

PubMed

Coordination of water movement among plant organs is important for understanding plant water use strategies. The hydraulic segmentation hypothesis (HSH) proposes that hydraulic conductance in shorter lived, 'expendable' organs such as leaves and longer lived, more 'expensive' organs such as stems may be decoupled, with resistance in leaves acting as a bottleneck or 'safety valve'. We tested the HSH in woody species from a Mediterranean-type ecosystem by measuring leaf hydraulic conductance (Kleaf ) and stem hydraulic conductivity (KS ). We also investigated whether leaves function as safety valves by relating Kleaf and the hydraulic safety margin (stem water potential minus the water potential at which 50% of conductivity is lost (?stem - ?50 )). We also examined related plant traits including the operating range of water potentials, wood density, leaf mass per area, and leaf area to sapwood area ratio to provide insight into whole-plant water use strategies. For hydrated shoots, Kleaf was negatively correlated with KS , supporting the HSH. Additionally, Kleaf was positively correlated with the hydraulic safety margin and negatively correlated with the leaf area to sapwood area ratio. Consistent with the HSH, our data indicate that leaves may act as control valves for species with high KS , or a low safety margin. This critical role of leaves appears to contribute importantly to plant ecological specialization in a drought-prone environment. PMID:24860955

Pivovaroff, Alexandria L; Sack, Lawren; Santiago, Louis S

2014-08-01

42

Brassica rapa stock description: F1 and F2 Non-purple stem, Yellow-green leaf stocks  

NSDL National Science Digital Library

PDF containing seed stock profile information for and illustration of the F1 and F2 Non-Purple Stem, Yellow-Green Leaf variety of Brassica rapa (Fast Plants). This also includes some brief suggestions for their use as a model organism in teaching Mendelian genetics with a monohybrid cross using Wisconsin Fast Plants.

Program, The W.

43

Students' Misconceptions in Interpreting Center and Variability of Data Represented via Histograms and Stem-and-Leaf Plots  

ERIC Educational Resources Information Center

This paper identifies and discusses misconceptions that students have in making judgments of center and variability when data are presented graphically. An assessment addressing interpreting center and variability in histograms and stem-and-leaf plots was administered to, and follow-up interviews were conducted with, undergraduates enrolled in…

Cooper, Linda L.; Shore, Felice S.

2008-01-01

44

Determination of chemical constituents of leaf and stem essential oils of Artemisia monosperma from central Saudi Arabia.  

PubMed

The leaf and stem essential oils of Artemisia monosperma from the desert region of central Saudi Arabia were analysed by gas chromatography-based techniques (GC-FID, GC-MS, Co-GC, LRI determination, database and literature search) using polar as well as non-polar columns, which resulted in the identification of 130 components, of which 81 were common to both oils. In the leaf oil 120 compounds were identified, while 91 were identified in the stem oil accounting for 98.4% and 99.7% of the oil composition, respectively. The major constituents of the leaf oil were beta-pinene (50.3%), a-terpinolene (10.0%), limonene (5.4%) and a-pinene (4.6%), while the major constituents of the stem oil were beta-pinene (36.7%), a-terpinolene (6.4%), limonene (4.8%), beta-maaliene (3.7%), shyobunone (3.2%) and a-pinene (3.1%). The two oils showed an important qualitative similarity. However, some specific constituents (39 in the leaf oil and 10 in the stem oil) allow differentiation of the two essential oils. PMID:22978234

Khan, Merajuddin; Mousa, Ahmad A; Syamasundar, Kodakandla V; Alkhathlan, Hamad Z

2012-08-01

45

Composition and antibacterial activity of essential oils from leaf, stem and root of Chrysanthemum parthenium (L.) Bernh. from Iran.  

PubMed

The water distilled essential oils from leaves, stems and roots of Chrysanthemum parthenium (L.) Bernh. were analyzed by GC and GC/MS methods. The leaf oil was characterized by a high amount of camphor (56.4%), whereas in the stem oil, camphor (26.0%), trans-beta-ocimene (23.6%) and germacrene-d (15.0%) were the major constituents. The main components of the root oil were alpha-pinene (50.0%), trans-beta-farnesene (13.8%) and bicyclogermacrene (11.0%). Antibacterial activity of the leaf, stem and root oil were evaluated using the micro-dilution broth method. The oils showed inhibitory effects on Escherichia coli and Salmonella typhi, but were not active against Staphylococcus aureus. PMID:19634337

Shafaghat, Ali; Sadeghi, Hajar; Oji, Khodamali

2009-06-01

46

Degradation of Perennial Ryegrass Leaf and Stem Cell Walls by the Anaerobic Fungus Neocallimastix sp. Strain CS3b  

PubMed Central

The degradation of cell walls isolated from stems and leaves of perennial ryegrass by the anaerobic fungus Neocallimastix sp. strain CS3b was studied in a defined medium. The combined cellulose and hemicellulose fraction represented 53.1 (wt/wt) and 63.3% (wt/wt) of the dry weight of control grass leaf and stem cell walls, respectively. In both leaf and stem cell walls, glucose was the major neutral monosaccharide, followed by xylose, arabinose, and galactose. After 2 days of fermentation with Neocallimastix sp. strain CS3b, treated cell walls contained smaller amounts of neutral sugars compared with those of undigested cell walls. These results were more evident for glucose, xylose, and arabinose than for galactose. Furthermore, the sugar content of leaf cell walls decreased before a decline in the sugar content of stem cell walls was observed. Data from formate and hydrogen production indicated that the growth of Neocallimastix sp. strain CS3b was completed in 4 days in the culture system used. During this period, the fungus liberated about 95% of the fermentable sugars in untreated material. On a percentage basis, no significant differences were found in final extent of degradation of glucose, xylose, and arabinose. Galactose, however, was degraded to a lesser extent.

Sijtsma, L.; Tan, B.

1996-01-01

47

Antimicrobial activity and chemical constituents of the essential oils from flower, leaf and stem of Gypsophila bicolor from Iran.  

PubMed

The volatile constituents from flower, leaf and stem of Gypsophila bicolor growing in Iran were obtained by hydrodistillation and analyzed by GC and GC/MS. The flower oil was characterized by high amounts of germacrene-D (21.2%), p-cymene (20.6%), bicyclogermacrene (17.6%), gamma-dodecadienolactone (13.7%) and terpinolene (9.4%). Twenty-four constituents representing 97.4% of the leaf oil were identified of which germacrene-D (23.4%), terpinolene (14.5%), bicyclogermacrene (7.5%), gamma-dodecadienolactone (6.8%), p-cymene (6.7%) and cis-beta-ocimene (6.3%) were major components. The main components of the stem oil were gamma-dodecadienolactone (28.5%), bicyclogermacrene (14.8%), germacrene-D (12.6%), p-cymene (12.5%), terpinolene (11.6%) and trans-beta-ocimene (4.2%). The antimicrobial effects of flower, leaf and stem essential oils from Gypsophila bicolor were studied according to the agar diffusion cup method. The essential oils had a moderate effect on the Gram-positive and Gram-negative bacteria, but had a substantial effect on the fungi studied. PMID:21425693

Shafagha, Ali; Shafaghatlonbar, Masoud

2011-02-01

48

Arachis hypogaea L. stem and leaf extract improves the sleep behavior of pentobarbital-treated rats  

PubMed Central

This study was conducted to evaluate the sedative effects of Arachis hypogaea L. stem and leaf extract (AHSLE) and determine its effect pathways through ?-aminobutyric acid (GABA)-gated channels on male Sprague-Dawley rats treated with pentobarbital. AHSLE was obtained from 98°C water (3 h, extracted twice). AHSLE and flumazenil (a GABA type A receptor antagonist) were administered to the rats orally, whereas pentobarbital sodium and muscimol (a GABA type A receptor agonist) were administered intraperitoneally (i.p.). The results demonstrated that AHSLE decreased sleep latency and increased sleep time in pentobarbital-treated rats (50 mg/kg, i.p.). The coadministration of AHSLE and muscimol (0.05 mg/kg) significantly increased sleep time and reduced sleep latency in pentobarbital-treated rats and these actions were significantly antagonized by flumazenil at a dose of 3.5 mg/kg. These results indicated that AHSLE improved the sleep behavior in pentobarbital-treated rats, possibly through GABA-gated channel-related mechanisms.

ZU, XIAO-YAN; XIONG, GUANG-QUAN; GENG, SHENG-RONG; LIAO, TAO; LI, XIN; ZHANG, ZHEN-YA

2014-01-01

49

Cell numbers and leaf development in Arabidopsis: a functional analysis of the STRUWWELPETER gene  

PubMed Central

The struwwelpeter (swp) mutant in Arabidopsis shows reduced cell numbers in all aerial organs. In certain cases, this defect is partially compensated by an increase in final cell size. Although the mutation does not affect cell cycle duration in the young primordia, it does influence the window of cell proliferation, as cell number is reduced during the very early stages of primordium initiation and a precocious arrest of cell proliferation occurs. In addition, the mutation also perturbs the shoot apical meristem (SAM), which becomes gradually disorganized. SWP encodes a protein with similarities to subunits of the Mediator complex, required for RNA polymerase II recruitment at target promoters in response to specific activators. To gain further insight into its function, we overexpressed the gene under the control of a constitutive promoter. This interfered again with the moment of cell cycle arrest in the young leaf. Our results suggest that the levels of SWP, besides their role in pattern formation at the meristem, play an important role in defining the duration of cell proliferation.

Autran, Daphne; Jonak, Claudia; Belcram, Katia; Beemster, Gerrit T.S.; Kronenberger, Jocelyne; Grandjean, Olivier; Inze, Dirk; Traas, Jan

2002-01-01

50

A comparative pharmacognostical and preliminary physico-chemical analysis of stem and leaf of Bacopa monnieri (L.) Pennel and Bacopa floribunda (R.BR.) Wettst  

PubMed Central

Brahmi is a well-known herbal drug having an effect on brain as a memory enhancer. Bacopa monnieri (L.) Pennel and Bacopa floribunda (R.Br.) Wettst are both marketed in the name of Brahmi. The present study differentiates Bacopa monnieri and Bacopa floribunda in morphology, transverse section (T.S.) of root and leaf, powder microscopy, and chemical constituents. Morphological characters show color difference in flower, stem and leaf and differences in microscopic study, organoleptic study, and powder characteristics. Morphologically, Bacopa monnieri leaf is fleshy and more succulent than Bacopa floribunda leaf. There is also a difference in the interval of the stem internodes of the two. Physico-chemical analysis revealed presence of 26% bacoside A in Bacopa floribunda leaf and 27% in Bacopa floribunda stem, which is higher than the bacoside A content in leaf (22%) and stem (18%) of Bacopa monnieri. However due to the hemolytic action of bacoside A, which is the toxic effect of the chemical constituent, it seems likely that Bacopa monnieri is more popular in regular use than Bacopa floribunda.

Gubbannavar, Jyoti S.; Chandola, H. M.; Harisha, C. R.; Khanpara, Komal; Shukla, V. J.

2013-01-01

51

Protection of wheat against leaf and stem rust and powdery mildew diseases by inhibition of polyamine metabolism  

NASA Technical Reports Server (NTRS)

In higher plants, polyamines arise from arginine by one of two pathways: via ornithine and ornithine decarboxylase or via agmatine and arginine decarboxylase but in fungi, only the ornithine decarboxylase pathway is present. Since polyamines are required for normal growth of microorganisms and plants and since the ornithine pathway can be irreversibly blocked by alpha-difluoromethylornithine (DFMO) which has no effect on arginine decarboxylase, fungal infection of green plants might be controlled by the site-directed use of such a specific metabolic inhibitor. DFMO at relatively low concentrations provided effective control of the three biotrophic fungal pathogens studied, Puccinia recondita (leaf rust), P. graminis f. sp. tritici (stem rust), and Erysiphe graminis (powdery mildew) on wheat (Triticum aestivum L.) Effective control of infection by leaf or stem rust fungi was obtained with sprays of DFMO that ranged from about 0.01 to 0.20 mM in experiments where the inhibitor was applied after spore inoculation. The powdery mildew fungus was somewhat more tolerant of DFMO, but good control of the pathogen was obtained at less than 1.0 mM. In general, application of DFMO after spore inoculation was more effective than application before inoculation. Less control was obtained following treatment with alpha-difluoromethylarginine (DFMA) but the relatively high degree of control obtained raises the possibility of a DFMA to DFMO conversion by arginase.

Weinstein, L. H.; Osmeloski, J. F.; Wettlaufer, S. H.; Galston, A. W.

1987-01-01

52

Antioxidant and antimicrobial activities of ethanol extract from the stem and leaf of Impatiens balsamina L. (Balsaminaceae) at different harvest times.  

PubMed

The aim of this study was to investigate the total phenolic content, total flavonoid contents, antioxidant activity and antimicrobial activity of ethanolic extract from stems (S) and leaves (L) of Impatiens balsamina L. (Balsaminaceae), which were harvested in Korea on March 10, 2011 (S1 and L1), May 14, 2011 (S2 and L2), and July 5, 2011 (S3 and L3), respectively. Our results revealed that the total phenolic (79.55-103.94 mg CE/g extract) and flavonoid (57.43-104.28 mg QE/g extract) contents of leaf extract were higher (p < 0.01) than those of stem extract. Leaf extracts (L1, L2, and L3) exhibited stronger (p < 0.01) free radical scavenging activity (66.06, 63.71, and 72.19%, respectively) than that of the positive control. In terms of antimicrobial activity, leaf extracts showed higher inhibitory effects against microorganisms than those of stem extracts (S1, S2, and S3). Among the leaf extracts at different harvest times, L3 showed the greatest antimicrobial activity against both Gram negative and Gram positive strains. From these results, the leaf extract from I. balsamina L. might be a valuable bioactive resource, and would seem to be applicable as a natural antioxidant in food preservation. PMID:23760032

Kang, Suk-Nam; Goo, Young-Min; Yang, Mi-Ra; Ibrahim, Rashid Ismael Hag; Cho, Jae-Hyeon; Kim, Il-Suk; Lee, Ok-Hwan

2013-01-01

53

Changes in leaf hydraulic conductance correlate with leaf vein embolism in Cercis siliquastrum L  

Microsoft Academic Search

The impact of xylem cavitation and embolism on leaf ( K leaf) and stem ( K stem) hydraulic conductance was measured in current-year shoots of Cercis siliquastrum L. (Judas tree) using the vacuum chamber technique. K stem decreased at leaf water potentials (? L) lower than -1.0 MPa, while K leaf started to decrease only at ? L L K leaf

Andrea Nardini; Sebastiano Salleo; Fabio Raimondo

2003-01-01

54

Sugar Contents of Single Cell Clones of Stem and Phylloxera Leaf Galls of the Grape Vine  

Microsoft Academic Search

INSECTS induce galls of many sizes and degrees of complexity in plants. The mechanism of gall induction and why growth finally ceases are not clearly understood. Phylloxera induces leaf gall in the grape vine which is typical of such abnormal growth in the sense that it is restricted in its development. Some of the biochemical and physiological changes which occur

R. P. Warick; A. C. Hildebrandt

1967-01-01

55

Stem Growth per Unit of Leaf Area: A Measure of Tree Vigor  

Microsoft Academic Search

The ratio of basal area growth to sapwood basal area is shown to correspond with stemwood-volume production per unit of leaf area. Analyzing 122 healthy Douglas-fir in one stand showed this ratio to be consistent among all but suppressed trees. Evaluating other stands suggests the ratio may be sensitive to environment and reflect competition. This ratio of tree vigor will

R. H. WARING; W. G. THIES; D. MUSCATO

56

Variation in the nutritional value of leaf and stem fractions of nineteen leucaena lines  

Microsoft Academic Search

In two experiments, 2.5-month-old edible regrowth of the genus Leucaena (varying in tolerance to the leucaena psyllid pest attack) were analysed for nutritive value. In Experiment 1, forage of nine lines was separated into young leaves, young stems (within woody fraction <5 mm diameter), old leaves and old stems (within a woody fraction 5–10 mm diameter) whereas in Experiment 2,

M Karachi

1998-01-01

57

Effect of Different Parts (Leaf, Stem and Stalk) and Seasons (Summer and Winter) on the Chemical Compositions and Antioxidant Activity of Moringa oleifera  

PubMed Central

Moringa oleifera, Lam. (Moringaceae) is grown world-wide in the tropics and sub-tropics of Asia and Africa and contains abundant various nutrients. This study describes the effect of different parts (leaf, stem and stalk) and seasons (summer and winter) on the chemical compositions and antioxidant activity of M. oleifera grown in Taiwan. The results showed that the winter samples of Moringa had higher ash (except the stalk part), calcium and phenolic compounds (except the leaf part) and stronger antioxidative activity than summer samples. The methanolic extract of Moringa showed strong scavenging effect of DPPH radicals and reducing power. The trend of antioxidative activity as a function of the part of Moringa was: leaf > stem > stalk for samples from both seasons investigated. The Moringa extract showed strong hydrogen peroxide scavenging activity and high Superoxide Dismutase (SOD) activity except the stalk part.

Shih, Ming-Chih; Chang, Cheng-Ming; Kang, Sue-Ming; Tsai, Min-Lang

2011-01-01

58

The endophytic mycoflora of bark, leaf, and stem tissues of Azadirachta indica A. Juss (neem) from Varanasi (India).  

PubMed

A systematic study was made of the endophytes of Azadirachta indica A. Juss (the neem tree) growing in several of its natural habitats in India. A total of 233 isolates of endophytic fungi representing 18 fungal taxa were obtained from segments of bark, stem, and leaves of this tree. Hyphomycetes (62.2%) were the most prevalent followed by the Coelomycetes (27.4%) and Mycelia Sterilia (7.7%). As mathematically determined, the maximum species richness and frequency of colonization of endophytes appeared in leaf segments rather than stem and bark tissues from each location. Endophytic colonization frequency was also greater in leaves (45.5%) than bark (31.5%). The leaf samples from all locations were nearly constant in their endophytic composition, whereas bark samples showed maximum diversity at different locations. Inter-site comparisons for endophytic diversity, however, were not significantly different with Loc1 and Loc2 having a maximum of 66.67% Jc. The smallest similarity was between Loc2 and Loc3 of 54.17% Jc. The dominant endophytic fungi isolated were Phomopsis oblonga, Cladosporium cladosporioides, Pestalotiopsis sp., Trichoderma sp, and Aspergillus sp. Genera such as Periconia, Stenella, and Drechslera are reported here for the first time as endophytes from this host plant. This report illustrates the value of sampling different tissues of a given plant in several locations to obtain the greatest species diversity of endophytes. The rich and sizeable collection of endophytic fungi from this specific plant may represent a unique source of one or more of the interesting and useful bioactive compounds normally associated with A. indica such as the azadirachtins and related tetranortriterpenoids. PMID:17394041

Verma, V C; Gond, S K; Kumar, A; Kharwar, R N; Strobel, Gary

2007-07-01

59

Expression of betapapillomavirus oncogenes increases the number of keratinocytes with stem cell-like properties.  

PubMed

Human papillomaviruses (HPV) of genus Betapapillomavirus (betaPV) are associated with nonmelanoma skin cancer development in epidermodysplasia verruciformis (EV) and immunosuppressed patients. Epidemiological and molecular studies suggest a carcinogenic activity of betaPV during early stages of cancer development. Since viral oncoproteins delay and perturb keratinocyte differentiation, they may have the capacity to either retain or confer a "stem cell-like" state on oncogene-expressing cells. The aim of this study was to determine (i) whether betaPV alters the expression of cell surface markers, such as CD44 and epithelial cell adhesion molecule (EpCAM), that have been associated with epithelial stemness, and (ii) whether this confers functional stem cell-like properties to human cutaneous keratinocytes. Fluorescence-activated cell sorter (FACS) analysis revealed an increase in the number of cells with high CD44 and EpCAM expression in keratinocyte cultures expressing HPV type 8 (HPV8) oncogenes E2, E6, and E7. Particularly through E7 expression, a distinct increase in clonogenicity and in the formation and size of tumor spheres was observed, accompanied by reduction of the epithelial differentiation marker Calgranulin B. These stem cell-like properties could be attributed to the pool of CD44(high) EpCAM(high) cells, which was increased within the E7 cultures of HPV5, -8, and -20. Enhanced EpCAM levels were present in organotypic skin cultures of primary keratinocytes expressing E7 of the oncogenic HPV types HPV5, -8, and -16 and in clinical samples from EV patients. In conclusion, our data show that betaPV may increase the number of stem cell-like cells present during early carcinogenesis and thus enable the persistence and accumulation of DNA damage necessary to generate malignant stem cells. PMID:24006432

Hufbauer, Martin; Biddle, Adrian; Borgogna, Cinzia; Gariglio, Marisa; Doorbar, John; Storey, Alan; Pfister, Herbert; Mackenzie, Ian; Akgül, Baki

2013-11-01

60

Expression of Betapapillomavirus Oncogenes Increases the Number of Keratinocytes with Stem Cell-Like Properties  

PubMed Central

Human papillomaviruses (HPV) of genus Betapapillomavirus (betaPV) are associated with nonmelanoma skin cancer development in epidermodysplasia verruciformis (EV) and immunosuppressed patients. Epidemiological and molecular studies suggest a carcinogenic activity of betaPV during early stages of cancer development. Since viral oncoproteins delay and perturb keratinocyte differentiation, they may have the capacity to either retain or confer a “stem cell-like” state on oncogene-expressing cells. The aim of this study was to determine (i) whether betaPV alters the expression of cell surface markers, such as CD44 and epithelial cell adhesion molecule (EpCAM), that have been associated with epithelial stemness, and (ii) whether this confers functional stem cell-like properties to human cutaneous keratinocytes. Fluorescence-activated cell sorter (FACS) analysis revealed an increase in the number of cells with high CD44 and EpCAM expression in keratinocyte cultures expressing HPV type 8 (HPV8) oncogenes E2, E6, and E7. Particularly through E7 expression, a distinct increase in clonogenicity and in the formation and size of tumor spheres was observed, accompanied by reduction of the epithelial differentiation marker Calgranulin B. These stem cell-like properties could be attributed to the pool of CD44high EpCAMhigh cells, which was increased within the E7 cultures of HPV5, -8, and -20. Enhanced EpCAM levels were present in organotypic skin cultures of primary keratinocytes expressing E7 of the oncogenic HPV types HPV5, -8, and -16 and in clinical samples from EV patients. In conclusion, our data show that betaPV may increase the number of stem cell-like cells present during early carcinogenesis and thus enable the persistence and accumulation of DNA damage necessary to generate malignant stem cells.

Biddle, Adrian; Borgogna, Cinzia; Gariglio, Marisa; Doorbar, John; Storey, Alan; Pfister, Herbert; Mackenzie, Ian; Akgul, Baki

2013-01-01

61

[Study of the influence of scan number on near-infrared diffuse spectra of tomato leaf and model precision].  

PubMed

Near-infrared spectroscopy technique is non-destructive, simple, fast, highly efficient, cheap to implement, and very recurrent with no sample preparation, and has been a rapid and non-destructive modem qualitative and quantitative technique that has been widely used in many fields. As a powerful analytical tool in product quality determination, this technology is based on the measurement of vibration frequencies of chemical bonds in functional group such as C-C, C-H, O-H, C=O and N-H upon absorption of radiation. However, NIR spectra are affected by the status of spectrometer and the set of parameters when scanning, such as accuracy of wavelength, resolution of apparatus, noise, scan time and uniformity of sample size. To provide foundation with optimum test condition when modeling, the influence of scan number on NIR diffuse spectra of tomato leaf and chlorophyll prediction model precision was studied. 102 tomato leaf samples were used in this experiment. Partial least-squares (PLS) was used to develop models and evaluate and compare these models. The results show that scan number does have effect on NIR spectra and prediction models. Variance value of root mean square (RMS) noise of NIR spectra diminished gradually with the increment of scan number. The spectral quality with high scan number was high, however, the system error of instrument increased too. The spectral quality with low scan number was low, while the spectra were smooth and system error of instrument decreased too. The determination coefficient of chlorophyll calibration and prediction model was highest with 128 scan number, however, the model was not robust. But with 32 scan number, although the coefficient was low, the calibration and prediction model was robust and only a short test time was needed. At the same time, the difference of models to predict chlorophyll contents with different scan numbers was not distinct (alpha = 0.05). Different influence factors should be considered when modeling. PMID:18975798

Jiang, Huan-yu; Peng, Yong-shi; Xie, Li-juan; Ying, Yi-bin

2008-08-01

62

Leaf and Stem CO2 Uptake in the Three Subfamilies of the Cactaceae 1  

PubMed Central

Net CO2 uptake over 24-hour periods was examined for the leaves and for the stems of 11 species of cacti representing all three subfamilies. For Pereskia aculeata, Pereskia grandifolia, and Maihuenia poeppigii (subfamily Pereskioideae), all the net shoot CO2 uptake was by the leaves and during the daytime. In contrast, for the leafless species Carnegiea gigantea, Ferocactus acanthodes, Coryphantha vivipara, and Mammillaria dioica (subfamily Cactoideae), all the shoot net CO2 uptake was by the stems and at night. Similarly, for leafless Opuntia ficus-indica (subfamily Opuntioideae), all net CO2 uptake occurred at night. For leafy members of the Opuntioideae (Pereskiopsis porteri, Quiabentia chacoensis, Austrocylindropuntia subulata), at least 88% of the shoot CO2 uptake over 24 hours was by the leaves and some CO2 uptake occurred at night. Leaves responded to the instantaneous level of photosynthetically active radiation (PAR) during the daytime, as occurs for C3 plants, whereas nocturnal CO2 uptake by stems of O. ficus-indica and F. acanthodes responded to the total daily PAR, as occurs for Crassulacean acid metabolism (CAM) plants. Thus, under the well-watered conditions employed, the Pereskioideae behaved as C3 plants, the Cactoideae behaved as CAM plants, and the Opuntioideae exhibited characteristics of both pathways.

Nobel, Park S.; Hartsock, Terry L.

1986-01-01

63

Leaf and Stem CO(2) Uptake in the Three Subfamilies of the Cactaceae.  

PubMed

Net CO(2) uptake over 24-hour periods was examined for the leaves and for the stems of 11 species of cacti representing all three subfamilies. For Pereskia aculeata, Pereskia grandifolia, and Maihuenia poeppigii (subfamily Pereskioideae), all the net shoot CO(2) uptake was by the leaves and during the daytime. In contrast, for the leafless species Carnegiea gigantea, Ferocactus acanthodes, Coryphantha vivipara, and Mammillaria dioica (subfamily Cactoideae), all the shoot net CO(2) uptake was by the stems and at night. Similarly, for leafless Opuntia ficus-indica (subfamily Opuntioideae), all net CO(2) uptake occurred at night. For leafy members of the Opuntioideae (Pereskiopsis porteri, Quiabentia chacoensis, Austrocylindropuntia subulata), at least 88% of the shoot CO(2) uptake over 24 hours was by the leaves and some CO(2) uptake occurred at night. Leaves responded to the instantaneous level of photosynthetically active radiation (PAR) during the daytime, as occurs for C(3) plants, whereas nocturnal CO(2) uptake by stems of O. ficus-indica and F. acanthodes responded to the total daily PAR, as occurs for Crassulacean acid metabolism (CAM) plants. Thus, under the well-watered conditions employed, the Pereskioideae behaved as C(3) plants, the Cactoideae behaved as CAM plants, and the Opuntioideae exhibited characteristics of both pathways. PMID:16664741

Nobel, P S; Hartsock, T L

1986-04-01

64

Optimising Human Mesenchymal Stem Cell Numbers for Clinical Application: A Literature Review  

PubMed Central

Adult mesenchymal stem cells (MSCs) are being investigated further for their use in stem cell therapies. However, as they are found in very low numbers in adult tissue, expansion in vitro is required to produce desired MSC numbers for clinical application. The need for effective cell-based therapies is increasing due to a rise in the ageing population, increasing the prevalence of musculoskeletal disorders. This review investigates how factors, age and gender of donor, as well as seeding density can affect MSC expansion. Age and gender of donor have received mixed results from studies, whereas seeding density studies have produced consistent results for numerous MSC sources, favouring lower seeding densities. Further research is required to reduce the risk of infection, loss of cell characterisation in cell culture, and making cell-based therapies more cost effective through creating rapid expansion of MSCs regardless of patient factors.

Fossett, E.; Khan, W. S.

2012-01-01

65

Estimating tree heights and number of stems in young forest stands using airborne laser scanner data  

Microsoft Academic Search

The mean heights of dominant trees and the stem numbers of 39 plots of 200 m2 each were derived from various canopy height metrics and canopy density measured by means of a small-footprint airborne laser scanner over young forest stands with tree heights <6 m. On the average, the laser transmitted 12,019 pulses ha?1. Ground-truth values were regressed against laser-derived

Erik Næsset; Kjell-Olav Bjerknes

2001-01-01

66

Notch signalling regulates stem cell numbers in vitro and in vivo.  

PubMed

The hope of developing new transplantation therapies for degenerative diseases is limited by inefficient stem cell growth and immunological incompatibility with the host. Here we show that Notch receptor activation induces the expression of the specific target genes hairy and enhancer of split 3 (Hes3) and Sonic hedgehog (Shh) through rapid activation of cytoplasmic signals, including the serine/threonine kinase Akt, the transcription factor STAT3 and mammalian target of rapamycin, and thereby promotes the survival of neural stem cells. In both murine somatic and human embryonic stem cells, these positive signals are opposed by a control mechanism that involves the p38 mitogen-activated protein kinase. Transient administration of Notch ligands to the brain of adult rats increases the numbers of newly generated precursor cells and improves motor skills after ischaemic injury. These data indicate that stem cell expansion in vitro and in vivo, two central goals of regenerative medicine, may be achieved by Notch ligands through a pathway that is fundamental to development and cancer. PMID:16799564

Androutsellis-Theotokis, Andreas; Leker, Ronen R; Soldner, Frank; Hoeppner, Daniel J; Ravin, Rea; Poser, Steve W; Rueger, Maria A; Bae, Soo-Kyung; Kittappa, Raja; McKay, Ronald D G

2006-08-17

67

Identification and characterization of miRNAome in root, stem, leaf and tuber developmental stages of potato (Solanum tuberosum L.) by high-throughput sequencing  

PubMed Central

Background MicroRNAs (miRNAs) are ubiquitous components of endogenous plant transcriptome. miRNAs are small, single-stranded and ~21 nt long RNAs which regulate gene expression at the post-transcriptional level and are known to play essential roles in various aspects of plant development and growth. Previously, a number of miRNAs have been identified in potato through in silico analysis and deep sequencing approach. However, identification of miRNAs through deep sequencing approach was limited to a few tissue types and developmental stages. This study reports the identification and characterization of potato miRNAs in three different vegetative tissues and four stages of tuber development by high throughput sequencing. Results Small RNA libraries were constructed from leaf, stem, root and four early developmental stages of tuberization and subjected to deep sequencing, followed by bioinformatics analysis. A total of 89 conserved miRNAs (belonging to 33 families), 147 potato-specific miRNAs (with star sequence) and 112 candidate potato-specific miRNAs (without star sequence) were identified. The digital expression profiling based on TPM (Transcripts Per Million) and qRT-PCR analysis of conserved and potato-specific miRNAs revealed that some of the miRNAs showed tissue specific expression (leaf, stem and root) while a few demonstrated tuberization stage-specific expressions. Targets were predicted for identified conserved and potato-specific miRNAs, and predicted targets of four conserved miRNAs, miR160, miR164, miR172 and miR171, which are ARF16 (Auxin Response Factor 16), NAM (NO APICAL MERISTEM), RAP1 (Relative to APETALA2 1) and HAM (HAIRY MERISTEM) respectively, were experimentally validated using 5? RLM-RACE (RNA ligase mediated rapid amplification of cDNA ends). Gene ontology (GO) analysis for potato-specific miRNAs was also performed to predict their potential biological functions. Conclusions We report a comprehensive study of potato miRNAs at genome-wide level by high-throughput sequencing and demonstrate that these miRNAs have tissue and/or developmental stage-specific expression profile. Also, predicted targets of conserved miRNAs were experimentally confirmed for the first time in potato. Our findings indicate the existence of extensive and complex small RNA population in this crop and suggest their important role in pathways involved in diverse biological processes, including tuber development.

2014-01-01

68

Early Life Nutrition Modulates Muscle Stem Cell Number: Implications for Muscle Mass and Repair  

PubMed Central

Suboptimal nutrition during prenatal and early postnatal development is associated with increased risk for type 2 diabetes during adult life. A hallmark of such diabetes risk is altered body composition, including reduced lean mass and increased adiposity. Since stem cell number and activity are important determinants of muscle mass, modulation of perinatal nutrition could alter stem cell number/function, potentially mediating developmentally programmed reductions in muscle mass. Skeletal muscle precursors (SMP) were purified from muscle of mice subjected to prenatal undernutrition and/or early postnatal high-fat diet (HFD)—experimental models that are both associated with obesity and diabetes risk. SMP number was determined by flow cytometry, proliferative capacity measured in vitro, and regenerative capacity of these cells determined in vivo after muscle freeze injury. Prenatally undernutrition (UN) mice showed significantly reduced SMP frequencies [Control (C) 4.8%±0.3% (% live cells) vs. UN 3.2%±0.4%, P=0.015] at 6 weeks; proliferative capacity was unaltered. Reduced SMP in UN was associated with 32% decrease in regeneration after injury (C 16%±3% of injured area vs. UN 11%±2%; P<0.0001). SMP frequency was also reduced in HFD-fed mice (chow 6.4%±0.6% vs. HFD 4.7%±0.4%, P=0.03), and associated with 44% decreased regeneration (chow 16%±2.7% vs. HFD 9%±2.2%; P<0.0001). Prenatal undernutrition was additive with postnatal HFD. Thus, both prenatal undernutrition and postnatal overnutrition reduce myogenic stem cell frequency and function, indicating that developmentally established differences in muscle-resident stem cell populations may provoke reductions in muscle mass and repair and contribute to diabetes risk.

Woo, Melissa; Isganaitis, Elvira; Cerletti, Massimiliano; Fitzpatrick, Connor; Wagers, Amy J.; Jimenez-Chillaron, Jose

2011-01-01

69

ANATOMIA COMPARATIVA DE HOJA Y TALLO EN LOS REPRESENTANTES DE CESTREAE G. DON (SOLANACEAE) DE ARGENTINA COMPARATIVE ANATOMY OF LEAF AND STEM IN SPECIES OF CESTREAE G. DON (SOLANACEAE) FROM ARGENTINA  

Microsoft Academic Search

This article compares leaf and stem anatomy of the 13 native and cultivated species of Cestrum L. and Sessea vestioides (Schltdl.) Hunz., of the tribe Cestreae G. Don (Solanaceae) from Argentina. Herbarium and FAA-preserved material was employed. The leaf characters which best distinguished among species were: secondary vein architecture, marginal ultimate venation, stomata and hairs, cuticle characteristics, presence of fibres

Iris J. Liscovsky; María T. Cosa

70

Clonal Contributions of Small Numbers of Retrovirally Marked Hematopoietic Stem Cells Engrafted in Unirradiated Neonatal W\\/Wnu Mice  

Microsoft Academic Search

Mice were repopulated with small numbers of retrovirally marked hematopoietic cells operationally definable as totipotent hematopoietic stem cells, without engraftment of cells at later stages of hematopoiesis, in order to facilitate analysis of stem cell clonal histories. This result depended upon the use of unirradiated W\\/Wnu newborn recipients. Before transplantation, viral integration markers were introduced during cocultivation of fetal liver

Blanche Capel; Robert Hawley; Luis Covarrubias; Teresa Hawley; Beatrice Mintz

1989-01-01

71

Grain amaranths are defoliation tolerant crop species capable of utilizing stem and root carbohydrate reserves to sustain vegetative and reproductive growth after leaf loss.  

PubMed

Tolerance to defoliation can be defined as the degree to which productivity is affected by photosynthetic area reduction. This trait was studied in grain amaranth (Amaranthus cruentus and A. hypochondriacus), which are considered to be a highly defoliation-tolerant species. The physiological and biochemical responses to increasing levels of mechanical leaf removal up to total defoliation were quantified. Tolerance appeared to be dependent on various factors: ( i) amount of lost tissue; (ii) mechanics of leaf tissue removal; (iii) environment, and (iv) species tested. Thus, grain amaranth was found to be a highly tolerant species under green-house conditions when leaf tissue loss was performed by gradual perforation. However, tolerance was compromised under similar conditions when defoliation was done by gradual cutting of the leaf. Also tolerance in completely defoliated plants tended to decrease under field conditions, where differences between A. cruentus and A. hypochondriacus were observed. All non-structural carbohydrate (NSC) levels were reduced in stems and roots of totally defoliated amaranths one day after treatment. Such depletion probably provided the carbon (C) resources needed to sustain the early recovery process in the absence of photosynthetic capacity. This was corroborated by shading of intact plants, which produced the same rapid and drastic reduction of NSC levels in these tissues. These results emphasize the role of stored NSCs, particularly starch, in buffering the impact of severe defoliation in amaranth. The fall in sucrose synthase and cell wall invertase activity observed in stems and roots soon after defoliation was consistent with their predicted shift from sink to source tissues. It is concluded that mobilization of C stores in stems and roots, is a physiologically important trait underlying tolerance to defoliation in grain amaranth. PMID:23861825

Vargas-Ortiz, Erandi; Espitia-Rangel, Eduardo; Tiessen, Axel; Délano-Frier, John Paul

2013-01-01

72

Chemical composition, cell wall features and degradability of stem, leaf blade and sheath in untreated and alkali-treated rice straw.  

PubMed

Three dominant morphological fractions (i.e. leaf blade (LB), leaf sheath (LS) and stem) were analysed for chemical composition and ruminal degradability in three rice straw varieties. In one variety treated with alkali, cell wall features were also characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy. The highest concentrations of cell wall carbohydrates (hemicellulose and cellulose) were observed in LS, whereas the highest concentrations of non-fibre (silica, phenolic compounds and CP) and lignin were recorded for LB. The stem had the lowest silica and hemicellulose contents but intermediate levels of other components. In terms of ruminal degradability, stem ranked higher than LB, which was followed by LS. Hemicellulose was found to be less degradable than either dry matter or cellulose in all the three fractions investigated. FTIR results indicated that the highest levels of hydrogen bonding, esterification and crystallinity within the cell wall components belonged to LS. In the alkaline treatment, these indices decreased to a larger extent for leaf fractions and a greater improvement was achieved in the degradability of LB and LS compared with that of stem. In the 24-h ruminal incubation, the silicified layer of epidermis and the underlying cell walls showed a rigid structure in the control fractions, whereas the treatment with NaOH resulted in crimping of the silicified cuticle layer and the loss of integrity in cell structure. Despite the highest silica and lignin contents observed in LB, LS showed the lowest degradability, which might be due to its high level of hydrogen bonding, crystallinity and esterification within its cell wall components as well as its high hemicellulose content. PMID:23473105

Ghasemi, E; Ghorbani, G R; Khorvash, M; Emami, M R; Karimi, K

2013-07-01

73

Identification of phosphoenolpyruvate carboxylase isoforms in leaf, stem and roots of the obligate CAM plant Vanilla planifolia Salib. (Orchidaceae): a physiological and molecular approach.  

PubMed

This study provides the first comparative analysis of phosphoenolpyruvate carboxylase isoforms (PEPc; EC 4.1.1.31) in an obligate crassulacean acid metabolism (CAM) plant, Vanilla planifolia Salisb. (Orchidaceae). Nocturnal CO2 fixation and malate accumulation by the leaves and the green stem show that these organs perform CAM. The chloroplast-containing aerial roots, however, exhibit C3 photosynthesis. The catalytic activity of PEPc was highest in the leaves compared with the stem and aerial roots. The Km (PEP) and Ki (malate) were similar in the PEPc extracted from leaf and aerial roots, and significant higher in stem. cDNA was obtained from those tissues and also from the soil-grown roots, and various cDNA clones were detected and amplified by means of RT-PCR and RACE-PCR. The amino-acid sequences of the PEPc isoforms deduced from the cDNA showed a great degree of homology, and Southern blot analysis suggests that the encoding genes form a small multigene family of at least two members. One PEPc isoform (PpcV1) is assumed to be related to CAM because, as shown by northern blot analysis, it is mainly expressed in the CAM-performing organs, i.e. in the leaves and the stem. A further isoform (PpcV2) was identified in the soil-grown roots and aerial roots, but northern blots show that to some extent PpcV2 is also expressed in the leaf and the stem tissues. Thus, it is assumed that PpcV2 encodes the housekeeping isoform of PEPc. Altogether, the present study provides support in favour of the view that isoforms of PEPc are related to specific functions. PMID:9869426

Gehrig, H; Faist, K; Kluge, M

1998-12-01

74

Genetic basis for developmental homeostasis of germline stem cell niche number: a network of Tramtrack-Group nuclear BTB factors.  

PubMed

The potential to produce new cells during adult life depends on the number of stem cell niches and the capacity of stem cells to divide, and is therefore under the control of programs ensuring developmental homeostasis. However, it remains generally unknown how the number of stem cell niches is controlled. In the insect ovary, each germline stem cell (GSC) niche is embedded in a functional unit called an ovariole. The number of ovarioles, and thus the number of GSC niches, varies widely among species. In Drosophila, morphogenesis of ovarioles starts in larvae with the formation of terminal filaments (TFs), each made of 8-10 cells that pile up and sort in stacks. TFs constitute organizers of individual germline stem cell niches during larval and early pupal development. In the Drosophila melanogaster subgroup, the number of ovarioles varies interspecifically from 8 to 20. Here we show that pipsqueak, Trithorax-like, batman and the bric-à-brac (bab) locus, all encoding nuclear BTB/POZ factors of the Tramtrack Group, are involved in limiting the number of ovarioles in D. melanogaster. At least two different processes are differentially perturbed by reducing the function of these genes. We found that when the bab dose is reduced, sorting of TF cells into TFs was affected such that each TF contains fewer cells and more TFs are formed. In contrast, psq mutants exhibited a greater number of TF cells per ovary, with a normal number of cells per TF, thereby leading to formation of more TFs per ovary than in the wild type. Our results indicate that two parallel genetic pathways under the control of a network of nuclear BTB factors are combined in order to negatively control the number of germline stem cell niches. PMID:23185495

Bartoletti, Mathieu; Rubin, Thomas; Chalvet, Fabienne; Netter, Sophie; Dos Santos, Nicolas; Poisot, Emilie; Paces-Fessy, Mélanie; Cumenal, Delphine; Peronnet, Frédérique; Pret, Anne-Marie; Théodore, Laurent

2012-01-01

75

Genetic Basis for Developmental Homeostasis of Germline Stem Cell Niche Number: A Network of Tramtrack-Group Nuclear BTB Factors  

PubMed Central

The potential to produce new cells during adult life depends on the number of stem cell niches and the capacity of stem cells to divide, and is therefore under the control of programs ensuring developmental homeostasis. However, it remains generally unknown how the number of stem cell niches is controlled. In the insect ovary, each germline stem cell (GSC) niche is embedded in a functional unit called an ovariole. The number of ovarioles, and thus the number of GSC niches, varies widely among species. In Drosophila, morphogenesis of ovarioles starts in larvae with the formation of terminal filaments (TFs), each made of 8–10 cells that pile up and sort in stacks. TFs constitute organizers of individual germline stem cell niches during larval and early pupal development. In the Drosophila melanogaster subgroup, the number of ovarioles varies interspecifically from 8 to 20. Here we show that pipsqueak, Trithorax-like, batman and the bric-à-brac (bab) locus, all encoding nuclear BTB/POZ factors of the Tramtrack Group, are involved in limiting the number of ovarioles in D. melanogaster. At least two different processes are differentially perturbed by reducing the function of these genes. We found that when the bab dose is reduced, sorting of TF cells into TFs was affected such that each TF contains fewer cells and more TFs are formed. In contrast, psq mutants exhibited a greater number of TF cells per ovary, with a normal number of cells per TF, thereby leading to formation of more TFs per ovary than in the wild type. Our results indicate that two parallel genetic pathways under the control of a network of nuclear BTB factors are combined in order to negatively control the number of germline stem cell niches.

Chalvet, Fabienne; Netter, Sophie; Dos Santos, Nicolas; Poisot, Emilie; Paces-Fessy, Melanie; Cumenal, Delphine; Peronnet, Frederique; Pret, Anne-Marie; Theodore, Laurent

2012-01-01

76

CO[sub 2] and temperature effects on leaf area production in two annual plant species  

SciTech Connect

The authors studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus retroflexus, under three day/night temperature regimes and two concentrations of carbon dioxide. The production of whole-plant leaf area during the first 30 d of growth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, production of branch leaves. Temperature and CO[sub 2] influenced leaf area production through effects on the rate of development, determined by the production of nodes on the main stem, and through shifts in the relationship between whole-plant leaf area and the number of main stem nodes. In Abutilon, leaf initiation rate was highest at 38[degree], but area of individual leaves was greatest at 28[degree]. Total leaf area was greatly reduced at 18[degree] due to slow leaf initiation rates. Elevated CO[sub 2] concentration increased leaf initiation rate at 28[degree], resulting in an increase in whole-part leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was increased by elevated CO[sub 2] at 28[degree]. Individual leaf area was greatest at 28[degree], and was increased by elevated CO[sub 2] at 28[degree] but decreased at 38[degree]. Branch leaf area displayed a similar response to CO[sub 2], butt was greater at 38[degree]. Overall, wholeplant leaf area was slightly increased at 38[degree] relative to 28[degree], and elevated CO[sub 2] levels resulted in increased leaf area at 28[degree] but decreased leaf area at 38[degree].

Ackerly, D.D.; Coleman, J.S.; Morse, S.R.; Bazzaz, F.A. (Harvard University, Cambridge, MA (United States))

1992-08-01

77

GC/MS analysis of volatiles obtained by headspace solid-phase microextraction and simultaneous-distillation extraction from Rabdosia serra (MAXIM.) HARA leaf and stem.  

PubMed

Volatiles in Rabdosia serra were investigated by headspace solid phase microextraction (HS-SPME) and simultaneous-distillation extraction (SDE). The HS-SPME technique was previously evaluated to optimise sampling conditions. A total of 56 and 48 compounds including alcohols, aldehydes, hydrocarbons, ketones, carboxylic acid, ester, and aromatics were identified in leaf and stem by optimised HS-SPME method (CAR/PDMS fibre; incubation time, 10 min; extraction temperature, 50°C; extraction time, 40 min), respectively. 1-Octen-3-ol and (2E)-hexenal had significant contribution to R. serra aroma. Cluster analysis indicated that leaf and stem exhibited different volatile diversity. Air drying was favourable for the retention of the volatiles, while freeze- and sun-drying led to the loss of volatiles. SDE method preferred to the analysis of compounds with low volatility including fatty acids and esters. HS-SPME was a useful technique for the analysis of readily volatile components for the characteristics of R. serra aroma. PMID:23122097

Lin, Lianzhu; Zhuang, Mingzhu; Lei, Fenfen; Yang, Bao; Zhao, Mouming

2013-01-15

78

Leaf area dynamics of potato cultivars infected by Phytophthora infestans  

Microsoft Academic Search

The effect ofPhytophthora infestans on foliage growth and senescence of three potato cultivars was studied in two field experiments. Inoculum or fungicide was\\u000a applied in different frequencies to establish a range of levels of disease. At weekly intervals leaf numbers were determined\\u000a as well as vertical canopy profiles of senescent and lesion covered leaf and stem area.\\u000a \\u000a \\u000a P. infestans reduced

M. Van Oijen

1991-01-01

79

Effect of Urtica dioica Leaf Alcoholic and Aqueous Extracts on the Number and the Diameter of the Islets in Diabetic Rats  

PubMed Central

Urtica dioica has been known as a plant that decreases blood glucose. Despite the importance of this plant in herbal medicine, relatively little research has been down on effects of this plant on islets yet. The objective of the current study was to evaluate the effect of dried Urtica dioica leaf alcoholic and aqueous extracts on the number and the diameter of the islets and histological parameters in streptozocin-induced diabetic rats. Six rats were used in each group. Group I: Normal rats were administered saline daily for 8 weeks. Group II: Diabetic rats were administered streptozotocin, 50 mg/kg of body weight; Group III: Diabetic rats were administered dried Urtica dioica leaf aqueous extracts for 8 weeks; Group IV: Diabetic rats were administered dried Urtica dioica leaf alcoholic extracts for 8 weeks. The animals, groups of diabetic and normal, were sacrificed by ether anaesthesia. Whole pancreas was dissected. The tissue samples were formalin fixed and paraffin embedded for microscopic examination. Histologic examination and grading were carried out on hematoxylin-eosin stained sections. The effects of administration of dried Urtica dioica leaf alcoholic and aqueous extracts to diabetic rats were determined by histopathologic examination. The pancreas from control rats showed normal pancreatic islets histoarchitecture. Our results also, indicate that the pancreas from diabetic rats show injury of pancreas tissue while the pancreas from diabetic rats treated with dried Urtica dioica leaf alcoholic and aqueous extracts show slight to moderate rearrangement of islets. According to our findings, dried Urtica dioica leaf alcoholic and aqueous extracts can cause a suitable repair of pancreatic tissue in streptozocin-induced diabetic experimental model.

Qujeq, Durdi; Tatar, Mohsen; Feizi, Farideh; Parsian, Hadi; Sohan Faraji, Alieh; Halalkhor, Sohrab

2013-01-01

80

Effect of Urtica dioica Leaf Alcoholic and Aqueous Extracts on the Number and the Diameter of the Islets in Diabetic Rats.  

PubMed

Urtica dioica has been known as a plant that decreases blood glucose. Despite the importance of this plant in herbal medicine, relatively little research has been down on effects of this plant on islets yet. The objective of the current study was to evaluate the effect of dried Urtica dioica leaf alcoholic and aqueous extracts on the number and the diameter of the islets and histological parameters in streptozocin-induced diabetic rats. Six rats were used in each group. Group I: Normal rats were administered saline daily for 8 weeks. Group II: Diabetic rats were administered streptozotocin, 50 mg/kg of body weight; Group III: Diabetic rats were administered dried Urtica dioica leaf aqueous extracts for 8 weeks; Group IV: Diabetic rats were administered dried Urtica dioica leaf alcoholic extracts for 8 weeks. The animals, groups of diabetic and normal, were sacrificed by ether anaesthesia. Whole pancreas was dissected. The tissue samples were formalin fixed and paraffin embedded for microscopic examination. Histologic examination and grading were carried out on hematoxylin-eosin stained sections. The effects of administration of dried Urtica dioica leaf alcoholic and aqueous extracts to diabetic rats were determined by histopathologic examination. The pancreas from control rats showed normal pancreatic islets histoarchitecture. Our results also, indicate that the pancreas from diabetic rats show injury of pancreas tissue while the pancreas from diabetic rats treated with dried Urtica dioica leaf alcoholic and aqueous extracts show slight to moderate rearrangement of islets. According to our findings, dried Urtica dioica leaf alcoholic and aqueous extracts can cause a suitable repair of pancreatic tissue in streptozocin-induced diabetic experimental model. PMID:24551786

Qujeq, Durdi; Tatar, Mohsen; Feizi, Farideh; Parsian, Hadi; Sohan Faraji, Alieh; Halalkhor, Sohrab

2013-01-01

81

Somatic copy number mosaicism in human skin revealed by induced pluripotent stem cells.  

PubMed

Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) has been suspected of causing de novo copy number variation. To explore this issue, here we perform a whole-genome and transcriptome analysis of 20 human iPSC lines derived from the primary skin fibroblasts of seven individuals using next-generation sequencing. We find that, on average, an iPSC line manifests two copy number variants (CNVs) not apparent in the fibroblasts from which the iPSC was derived. Using PCR and digital droplet PCR, we show that at least 50% of those CNVs are present as low-frequency somatic genomic variants in parental fibroblasts (that is, the fibroblasts from which each corresponding human iPSC line is derived), and are manifested in iPSC lines owing to their clonal origin. Hence, reprogramming does not necessarily lead to de novo CNVs in iPSCs, because most of the line-manifested CNVs reflect somatic mosaicism in the human skin. Moreover, our findings demonstrate that clonal expansion, and iPSC lines in particular, can be used as a discovery tool to reliably detect low-frequency CNVs in the tissue of origin. Overall, we estimate that approximately 30% of the fibroblast cells have somatic CNVs in their genomes, suggesting widespread somatic mosaicism in the human body. Our study paves the way to understanding the fundamental question of the extent to which cells of the human body normally acquire structural alterations in their DNA post-zygotically. PMID:23160490

Abyzov, Alexej; Mariani, Jessica; Palejev, Dean; Zhang, Ying; Haney, Michael Seamus; Tomasini, Livia; Ferrandino, Anthony F; Rosenberg Belmaker, Lior A; Szekely, Anna; Wilson, Michael; Kocabas, Arif; Calixto, Nathaniel E; Grigorenko, Elena L; Huttner, Anita; Chawarska, Katarzyna; Weissman, Sherman; Urban, Alexander Eckehart; Gerstein, Mark; Vaccarino, Flora M

2012-12-20

82

Multiple feedback loops through cytokinin signaling control stem cell number within the Arabidopsis shoot meristem.  

PubMed

A central unanswered question in stem cell biology, both in plants and in animals, is how the spatial organization of stem cell niches are maintained as cells move through them. We address this question for the shoot apical meristem (SAM) which harbors pluripotent stem cells responsible for growth of above-ground tissues in flowering plants. We find that localized perception of the plant hormone cytokinin establishes a spatial domain in which cell fate is respecified through induction of the master regulator WUSCHEL as cells are displaced during growth. Cytokinin-induced WUSCHEL expression occurs through both CLAVATA-dependent and CLAVATA-independent pathways. Computational analysis shows that feedback between cytokinin response and genetic regulators predicts their relative patterning, which we confirm experimentally. Our results also may explain how increasing cytokinin concentration leads to the first steps in reestablishing the shoot stem cell niche in vitro. PMID:19717465

Gordon, Sean P; Chickarmane, Vijay S; Ohno, Carolyn; Meyerowitz, Elliot M

2009-09-22

83

Leaf and stem anatomical responses to periodical waterlogging in simulated tidal floods in mangrove Avicennia marina seedlings  

Microsoft Academic Search

This study was aimed to evaluate anatomical responses to waterlogging of mangrove seedlings (Avicennia marina (Forsk.) Vierh.) grown in experimentally simulated semidiurnal tides. The following treatments were used: 0, 2, 4, 6, 8, 10 and 12h submergence period with two daily tidal cycles. With increasing waterlogging duration, the leaf thickness, mesophyll thickness, palisade parenchyma thickness, palisade–spongy ratio and hypodermis thickness

Yan Xiao; Zuliang Jie; Mao Wang; Guanghui Lin; Wenqing Wang

2009-01-01

84

Somatic copy-number mosaicism in human skin revealed by induced pluripotent stem cells  

PubMed Central

Reprogramming human somatic cells into induced pluripotent stem cells (iPSCs) has been suspected of causing de novo copy number variations (CNVs)1-4. To explore this issue, we performed a whole-genome and transcriptome analysis of 20 human iPSC lines derived from primary skin fibroblasts of 7 individuals using next-generation sequencing. We find that, on average, an iPSC line manifests two CNVs not apparent in the fibroblasts from which the iPSC was derived. Using qPCR, PCR, and digital droplet PCR (ddPCR), we show that at least 50% of those CNVs are present as low frequency somatic genomic variants in parental fibroblasts (i.e. the fibroblasts from which each corresponding hiPSC line is derived) and are manifested in iPSC colonies due to the colonies’ clonal origin. Hence, reprogramming does not necessarily lead to de novo CNVs in iPSC, since most of line-manifested CNVs reflect somatic mosaicism in the human skin. Moreover, our findings demonstrate that clonal expansion, and iPSC lines in particular, can be used as a discovery tool to reliably detect low frequency CNVs in the tissue of origin. Overall, we estimate that approximately 30% of the fibroblast cells have somatic CNVs in their genomes, suggesting widespread somatic mosaicism in the human body. Our study paves the way to understanding the fundamental question of the extent to which cells of the human body normally acquire structural alterations in their DNA post-zygotically.

Abyzov, Alexej; Mariani, Jessica; Palejev, Dean; Zhang, Ying; Haney, Michael Seamus; Tomasini, Livia; Ferrandino, Anthony; Belmaker, Lior A. Rosenberg; Szekely, Anna; Wilson, Michael; Kocabas, Arif; Calixto, Nathaniel E.; Grigorenko, Elena L.; Huttner, Anita; Chawarska, Katarzyna; Weissman, Sherman; Urban, Alexander Eckehart; Gerstein, Mark; Vaccarino, Flora M.

2012-01-01

85

Allometric estimation of total leaf area in the neotropical palm Euterpe oleracea at La Selva, Costa Rica  

Microsoft Academic Search

We estimated the magnitude of the total leaf area of the neotropical palm Euterpe oleracea and examined its allometry relative to the variation in stem height and diameter at La Selva Biological Station in Costa\\u000a Rica. The allometric relationships between frond leaf area and frond length (from tip to base), and between frond leaf area\\u000a and number of leaflets, were

Gerardo Avalos; Olivia Sylvester

2010-01-01

86

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...30.2 Leaf tobacco. Tobacco in the forms in which...manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings,...

2009-01-01

87

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...30.2 Leaf tobacco. Tobacco in the forms in which...manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings,...

2010-01-01

88

Notch signalling regulates stem cell numbers in vitro and in vivo  

Microsoft Academic Search

The hope of developing new transplantation therapies for degenerative diseases is limited by inefficient stem cell growth and immunological incompatibility with the host. Here we show that Notch receptor activation induces the expression of the specific target genes hairy and enhancer of split 3 (Hes3) and Sonic hedgehog (Shh) through rapid activation of cytoplasmic signals, including the serine\\/threonine kinase Akt,

Andreas Androutsellis-Theotokis; Ronen R. Leker; Frank Soldner; Daniel J. Hoeppner; Rea Ravin; Steve W. Poser; Maria A. Rueger; Soo-Kyung Bae; Raja Kittappa; Ronald D. G. McKay

2006-01-01

89

Clonal propagation of Stevia rebaudiana Bertoni by stem-tip culture  

Microsoft Academic Search

Clonal propagation of Stevia rebaudiana has been established by culturing stem-tips with a few leaf primordia on an agar medium supplemented with a high concentration (10 mg\\/l) of kinetin. Anatomical examination has suggested that these multiple shoots originate from a number of adventitious buds formed on the margin of the leaf. Innumerable shoots can be obtained by repeating the cycle

Yukiyoshi Tamura; Shigeharu Nakamura; Hiroshi Fukui; Mamoru Tabata

1984-01-01

90

STEM?!?!  

ERIC Educational Resources Information Center

The author's son has been an engineer since birth. He never asked "why" as a toddler, it was always "how's it work?" So that he wanted a STEM-based home education was no big surprise. In this article, the author considers what kind of curricula would work best for her complex kid.

Merrill, Jen

2012-01-01

91

DRYING KINETICS OF CORIANDER (Coriandrum sativum) LEAF AND STEM CINÉTICAS DE SECADO DE HOJA Y TALLO DE CILANTRO (Coriandrum sativum)  

Microsoft Academic Search

The drying kinetics of coriander leaves and stems, with or without blanching, was studied at several temperatures (50, 60, 70, and 80°C) at constant air velocity (1.5 m s) in a fixed-bed dryer. Three drying models, Henderson and Pabis, Midilli et al., and the Logarithmic, were fitted to the experimental data. According to the results obtained, it was verified that

A. S. Silva; F. de A. C. Almeida; E. E. Lima; F. L. H. Silva; J. P. Gomes

2008-01-01

92

Comparison of stem/progenitor cell number and transcriptomic profile in the mammary tissue of dairy and beef breed heifers.  

PubMed

Bovine mammary stem cells (MaSC) are a source of ductal and lobulo-alveolar tissue during the development of the mammary gland and its remodeling in repeating lactation cycles. We hypothesize that the number of MaSC, their molecular properties, and interactions with their niche may be essential in order to determine the mammogenic potential in heifers. To verify this hypothesis, we compared the number of MaSC and the transcriptomic profile in the mammary tissue of 20-month-old, non-pregnant dairy (Holstein-Friesian, HF) and beef (Limousin, LM) heifers. For the identification and quantification of putative stem/progenitor cells in mammary tissue sections, scanning cytometry was used with a combination of MaSC molecular markers: stem cell antigen-1 (Sca-1) and fibronectin type III domain containing 3B (FNDC3B) protein. Cytometric analysis revealed a significantly higher number of Sca-1(pos)FNDC3B(pos) cells in HF (2.94?±?0.35 %) than in LM (1.72?±?0.20 %) heifers. In HF heifers, a higher expression of intramammary hormones, growth factors, cytokines, chemokines, and transcription regulators was observed. The model of mammary microenvironment favorable for MaSC was associated with the regulation of genes involved in MaSC maintenance, self-renewal, proliferation, migration, differentiation, mammary tissue remodeling, angiogenesis, regulation of adipocyte differentiation, lipid metabolism, and steroid and insulin signaling. In conclusion, the mammogenic potential in postpubertal dairy heifers is facilitated by a higher number of MaSC and up-regulation of mammary auto- and paracrine factors representing the MaSC niche. PMID:24748329

Osi?ska, Ewa; Wicik, Zofia; Godlewski, Micha? M; Paw?owski, Karol; Majewska, Alicja; Mucha, Joanna; Gajewska, Ma?gorzata; Motyl, Tomasz

2014-08-01

93

Numbers  

NSDL National Science Digital Library

This engaging web site contains information and interactive applets related to various number systems: Egyptian, Babylonian, Chinese, Greek, Roman, Mayan, and Arabic. Users learn the history and structure of each system as well as how to count and write numbers. The site also allows users to explore finger systems, calculating machines, other number bases, and "interesting numbers." A series of pages on data and graphs includes information and activities on gathering, analyzing, graphing and sorting data. (Because the section on the Arabic number system is so extensive, it is cataloged separately as a related resource.)

Edkins, Jo

2006-01-01

94

Evidence of hydraulic lift for pre-rainy season leaf out and dry-season stem water enrichment in Sclerocarya birrea, a tropical agroforestry tree  

NASA Astrophysics Data System (ADS)

We use stable isotopes of water as tracers to follow water use by five Sclerocarya birrea trees in a catchment in South Eastern Burkina Faso interspersed with millet fields, gallery forest, Sudanian savanna, and fallow fields. Isotopic ratios were determined from water extracted from stems of the trees and sub-canopy soil of two of them, while nearby ground water, precipitation, and surface water was sampled weekly. A unique configuration of sensors connected with a wireless sensor network of meteorological stations measured sub-canopy shading, the temperature and humidity in the canopy, through-fall, and soil moisture under two of the trees. Both water extracted from sap and water extracted from soil is extremely enriched in the dry season, but drop to levels close to the ground water in February or March, which coincides with the growth of leaves. Dates of leaf out were confirmed by changes in ?DH and ?O18 concentrations of water, photographic documentation & pixel analysis, and analysis of sub-canopy radiation and proceeded the rise in humidity and flow that was later detected in the sub-canopy soil, the trunk of the tree (sap-flow), and atmosphere (canopy VPD). Examination of the isotopic signature suggests that size of tree plays an important role in duration and timing of this leaf-out as well as the degree of enrichment during the peak of the dry season. Further examination of the isotopic signatures of the roots suggested that the trees are performing hydraulic redistribution, or lifting the ground water and "sharing it" with the soil in the rooting zone in the dry season. The enriched level of xylem in this case is a product of water loss, and enrichment, along the travel path of the water from the roots to the tip of the stem, as evidenced by the variation according to size of tree. Vapor pressure deficit, soil water, and soil moisture interactions support this picture of interacting controls, separate from hydrologic triggers on the water movement in the tree.

Ceperley, Natalie; Mande, Theophile; Rinaldo, Andrea; Parlange, Marc B.

2014-05-01

95

Cutting position, leaf removal and time of year affects Rosa axillary shoot development  

Microsoft Academic Search

The interaction between the cutting position, leaf removal and the time of year on Rosa X hybrida L. cvs ‘Royalty’ and ‘Lovely Girl’ axillary shoot development was studied. The axillary shoot number per stem increased from 1.4 to 3.3 shoots as the cutting position increased from 1 to 13. The blind shoot number increased on ‘Royalty’ but not on the

John E. Erwin; Nina Glomsrud; Tom Vikor; R. Moe; Pat Etzel

1997-01-01

96

In Vitro Phytochemical, Antibacterial, and Antifungal Activities of Leaf, Stem, and Root Extracts of Adiantum capillus veneris  

PubMed Central

Adiantum capillus veneris is a medicinally essential plant used for the treatment of diverse infectious diseases. The study of phytochemical and antimicrobial activities of the plant extracts against multidrug-resistant (MDR) bacteria and medically important fungi is of immense significance. Extracts from the leaves, stems, and roots of Adiantum capillus veneris were extracted with water, methanol, ethanol, ethyl acetate, and hexane and screened for their antimicrobial activity against ten MDR bacterial strains and five fungal strains isolated from clinical and water samples. Ash, moisture, and extractive values were determined according to standard protocols. FTIR (Fourier transform infrared Spectroscopy) studies were performed on different phytochemicals isolated from the extracts of Adiantum capillus Veneris. Phytochemical analysis showed the presence of flavonoids, alkaloids, tannins, saponins, cardiac glycosides, terpenoids, steroids, and reducing sugars. Water, methanol, and ethanol extracts of leaves, stems, and roots showed significant antibacterial and antifungal activities against most of the MDR bacterial and fungal strains. This study concluded that extracts of Adiantum capillus veneris have valuable phytochemicals and significant activities against most of the MDR bacterial strains and medically important fungal strains.

Ishaq, Muhammad Saqib; Siddique Afridi, Muhammad; Khattak, Mahrukh; Ahmad, Sohail; Shakirullah

2014-01-01

97

The Mitochondrial Genome of the Leaf-Cutter Ant Atta laevigata: A Mitogenome with a Large Number of Intergenic Spacers  

PubMed Central

In this paper we describe the nearly complete mitochondrial genome of the leaf-cutter ant Atta laevigata, assembled using transcriptomic libraries from Sanger and Illumina next generation sequencing (NGS), and PCR products. This mitogenome was found to be very large (18,729 bp), given the presence of 30 non-coding intergenic spacers (IGS) spanning 3,808 bp. A portion of the putative control region remained unsequenced. The gene content and organization correspond to that inferred for the ancestral pancrustacea, except for two tRNA gene rearrangements that have been described previously in other ants. The IGS were highly variable in length and dispersed through the mitogenome. This pattern was also found for the other hymenopterans in particular for the monophyletic Apocrita. These spacers with unknown function may be valuable for characterizing genome evolution and distinguishing closely related species and individuals. NGS provided better coverage than Sanger sequencing, especially for tRNA and ribosomal subunit genes, thus facilitating efforts to fill in sequence gaps. The results obtained showed that data from transcriptomic libraries contain valuable information for assembling mitogenomes. The present data also provide a source of molecular markers that will be very important for improving our understanding of genomic evolutionary processes and phylogenetic relationships among hymenopterans.

Rodovalho, Cynara de Melo; Lyra, Mariana Lucio; Ferro, Milene; Bacci, Mauricio

2014-01-01

98

The Leaf Size-Twig Size Spectrum of Temperate Woody Species Along an Altitudinal Gradient: An Invariant Allometric Scaling Relationship  

PubMed Central

• Background and Aims The leaf size–twig size spectrum is one of the leading dimensions of plant ecological variation, and now it is under development. The purpose of this study was to test whether the relationship between leaf size and twig size is isometric or allometric, and to examine the relationship between plant allometric growth and life history strategies in the spectrum. • Methods Leaf and stem characters—including leaf and stem mass, total leaf area, individual leaf area, stem cross-sectional area, leaf number and stem length—at the twig level for 59 woody species were investigated along an altitudinal gradient on Changbaishan Mountain in the temperate zone of China. The environmental gradient ranges from temperate broad-leaved mixed forest at low altitude, to conifer forest at middle altitude, and to sub-alpine birch forest at high altitude. The scaling relationships between stem cross-sectional area and stem mass, stem mass and leaf mass, and leaf mass and leaf area at the twig level were simultaneously determined. • Key Results Twig cross-sectional area was found to have invariant allometric scaling relationships with the stem mass, leaf mass, total leaf area and individual leaf area, all with common slopes being significantly larger than 1, for three altitudinal-zoned vegetation types under investigation. However, leaf mass was found to be isometrically related to stem mass and leaf area along the environmental gradient. Based on the predictions of previous models, the exponent value of the relationship between twig cross-sectional area and total leaf area can be inferred to be 1·5, which falls between the confidence intervals of the relationship at each altitude, and between the confidence intervals of the common slope value (1·17–1·56) of this study. This invariant scaling relationship is assumed to result from the fractural network and/or developmental constraints of plants. The allometric constants (y-intercepts) of the relationships between the stem cross-sectional area and leaf area (both total leaf area and individual leaf area) were found to decrease significantly along the altitudinal gradient. This suggests that the species would support less leaf area at a given twig cross-sectional area with increasing environmental stress. • Conclusions This study demonstrated that plants respond to the environmental gradient by changing the y-intercepts of the relationship between leaf size–twig size, while keeping the exponent value of the allometric relationship as an invariant constant. The allometric growth in the twig size–leaf size spectrum is related to many other components of plant life history strategy, including the well established life history trade-off between efficiency and safety in the hydraulic transport of water.

SUN, SHUCUN; JIN, DONGMEI; SHI, PEILI

2006-01-01

99

Leaf Rolling and Stem Fasciation in Grass Pea (Lathyrus sativus L.) Mutant Are Mediated through Glutathione-Dependent Cellular and Metabolic Changes and Associated with a Metabolic Diversion through Cysteine during Phenotypic Reversal  

PubMed Central

A Lathyrus sativus L. mutant isolated in ethylmethane sulfonate-treated M2 progeny of mother variety BioL-212 and designated as rlfL-1 was characterized by inwardly rolled-leaf and stem and bud fasciations. The mutant exhibited karyomorphological peculiarities in both mitosis and meiosis with origin of aneuploidy. The mitosis was vigorous with high frequency of divisional cells and their quick turnover presumably steered cell proliferations. Significant transcriptional upregulations of cysteine and glutathione synthesis and concomitant stimulations of glutathione-mediated antioxidant defense helped rlfL-1 mutant to maintain balanced reactive oxygen species (ROS) metabolisms, as deduced by ROS-imaging study. Glutathione synthesis was shut down in buthionine sulfoximine- (BSO-) treated mother plant and mutant, and leaf-rolling and stems/buds fasciations in the mutant were reversed, accompanied by normalization of mitotic cell division process. Antioxidant defense was downregulated under low glutathione-redox but cysteine-desulfurations and photorespiratory glycolate oxidase transcripts were markedly overexpressed, preventing cysteine overaccumulation but resulted in excess H2O2 in BSO-treated mutant. This led to oxidative damage in proliferating cells, manifested by severe necrosis in rolled-leaf and fasciated stems. Results indicated vital role of glutathione in maintaining abnormal proliferations in plant organs, and its deficiency triggered phenotypic reversal through metabolic diversions of cysteine and concomitant cellular and metabolic modulations.

Talukdar, Dibyendu; Talukdar, Tulika

2014-01-01

100

Variable number of tandem repeat markers in the genome sequence of Mycosphaerella fijiensis, the causal agent of black leaf streak disease of banana (Musa spp).  

PubMed

We searched the genome of Mycosphaerella fijiensis for molecular markers that would allow population genetics analysis of this plant pathogen. M. fijiensis, the causal agent of banana leaf streak disease, also known as black Sigatoka, is the most devastating pathogen attacking bananas (Musa spp). Recently, the entire genome sequence of M. fijiensis became available. We screened this database for VNTR markers. Forty-two primer pairs were selected for validation, based on repeat type and length and the number of repeat units. Five VNTR markers showing multiple alleles were validated with a reference set of isolates from different parts of the world and a population from a banana plantation in Costa Rica. Polymorphism information content values varied from 0.6414 to 0.7544 for the reference set and from 0.0400 and 0.7373 for the population set. Eighty percent of the polymorphism information content values were above 0.60, indicating that the markers are highly informative. These markers allowed robust scoring of agarose gels and proved to be useful for variability and population genetics studies. In conclusion, the strategy we developed to identify and validate VNTR markers is an efficient means to incorporate markers that can be used for fungicide resistance management and to develop breeding strategies to control banana black leaf streak disease. This is the first report of VNTR-minisatellites from the M. fijiensis genome sequence. PMID:21064028

Garcia, S A L; Van der Lee, T A J; Ferreira, C F; Te Lintel Hekkert, B; Zapater, M-F; Goodwin, S B; Guzmán, M; Kema, G H J; Souza, M T

2010-01-01

101

Chemical composition of essential oil and anti trichomonas activity of leaf, stem, and flower of Rheum ribes L. extracts  

PubMed Central

Objectives: Trichomoniasis is one of the most common sexually transmitted diseases in humans and is caused by the protozoan Trichomonas vaginalis. Nowadays, increasing resistance to drugs such as metronidazole resulted in many problem, so new effective remedies are needed. In this study, we evaluate constituents of essential oil and anti-trichomonas activity of Rheum ribes. Materials and Methods: The essential oil from Rheum ribes L. flower growing wild in Iran was analyzed by GC/MS. The parasites were treated with different extract and fractions of the flower, stem, and leave of the plant. Anti-trichomonas activity was evaluated using an in vitro assay. Results: In all, 19 compounds were identified; palmitic acid [27.08%], n-eicosane [9.9%], n-tetracosane [7.34%], linoleic acid [6.56%], and ethyl linoleate [4.76%] were the main components of the oil. Rheum ribes extracts and fractions concentration dependently inhibited the ability of parasites to growth. This was associated with polarity of solvent used for fractionation and plant parts used for extraction. Conclusion: Findings demonstrate the potential of Rheum ribes extracts as an anti-trichomonas agent for human use. Further studies are required to evaluate its toxicity and safety.

Naemi, Forough; Asghari, Gholamreza; Yousofi, Hossein; Yousefi, Hossein Ali

2014-01-01

102

Antioxidant, antihyperglycemic, and antihyperlipidemic effects of Coriandrum sativum leaf and stem in alloxan-induced diabetic rats.  

PubMed

In India's indigenous system of medicine, Coriandrum sativum (CS), commonly used as a food ingredient, is claimed to be useful for various ailments. To establish its utility in diabetes mellitus, the present study evaluated the antidiabetic and antioxidant effects of CS in alloxan-induced diabetic rats. The extracts were shown to contain bioactive compounds including phenolics, flavonoids, steroids, and tannins. The extracts of CS in alloxan-induced diabetic rats were found to significantly lower blood glucose levels. Antidiabetic activity of the CS extracts was compared with the clinically available drug glibenclamide. The levels of serum total cholesterol, triglycerides, and low-density lipoprotein cholesterol were lower in the extract-treated group and high-density lipoprotein cholesterol was higher than the diabetic control rats. The extracts of CS exhibited strong scavenging effect on 2, 2-diphenyl-2-picrylhydrazyl free radical and inhibition of lipid peroxidation. The free radical scavenging effect of the extracts was comparable with that of the reference antioxidants. Furthermore, it also showed an improved antioxidant potential as evidenced by decreased lipid peroxidation and a significant increase in the activity of various antioxidant enzymes such as catalase, superoxide dismutase, and glutathione peroxidase in the liver of diabetic rats. These results indicate that the extracts could protect liver function and exhibited hypoglycemic, hypolipidemic, and antioxidant efficacies in the diabetic rats. These results support the use of this plant extract to manage diabetes mellitus. PRACTICAL APPLICATIONS: The leaves and stem of this plant Coriandrum sativum if used in cuisine would be a remedy for diabetes. PMID:22671941

Sreelatha, S; Inbavalli, R

2012-07-01

103

Conserved loci of leaf and stem rust fungi of wheat share synteny interrupted by lineage-specific influx of repeat elements  

PubMed Central

Background Wheat leaf rust (Puccinia triticina Eriks; Pt) and stem rust fungi (P. graminis f.sp. tritici; Pgt) are significant economic pathogens having similar host ranges and life cycles, but different alternate hosts. The Pt genome, currently estimated at 135 Mb, is significantly larger than Pgt, at 88 Mb, but the reason for the expansion is unknown. Three genomic loci of Pt conserved proteins were characterized to gain insight into gene content, genome complexity and expansion. Results A bacterial artificial chromosome (BAC) library was made from P. triticina race 1, BBBD and probed with Pt homologs of genes encoding two predicted Pgt secreted effectors and a DNA marker mapping to a region of avirulence. Three BACs, 103 Kb, 112 Kb, and 166 Kb, were sequenced, assembled, and open reading frames were identified. Orthologous genes were identified in Pgt and local conservation of gene order (microsynteny) was observed. Pairwise protein identities ranged from 26 to 99%. One Pt BAC, containing a RAD18 ortholog, shares syntenic regions with two Pgt scaffolds, which could represent both haplotypes of Pgt. Gene sequence is diverged between the species as well as within the two haplotypes. In all three BAC clones, gene order is locally conserved, however, gene shuffling has occurred relative to Pgt. These regions are further diverged by differing insertion loci of LTR-retrotransposon, Gypsy, Copia, Mutator, and Harbinger mobile elements. Uncharacterized Pt open reading frames were also found; these proteins are high in lysine and similar to multiple proteins in Pgt. Conclusions The three Pt loci are conserved in gene order, with a range of gene sequence divergence. Conservation of predicted haustoria expressed secreted protein genes between Pt and Pgt is extended to the more distant poplar rust, Melampsora larici-populina. The loci also reveal that genome expansion in Pt is in part due to higher occurrence of repeat-elements in this species.

2013-01-01

104

Frozen Cord Blood Hematopoietic Stem Cells Differentiate into Higher Numbers of Functional Natural Killer Cells In Vitro than Mobilized Hematopoietic Stem Cells or Freshly Isolated Cord Blood Hematopoietic Stem Cells  

PubMed Central

Adoptive natural killer (NK) cell therapy relies on the acquisition of large numbers of NK cells that are cytotoxic but not exhausted. NK cell differentiation from hematopoietic stem cells (HSC) has become an alluring option for NK cell therapy, with umbilical cord blood (UCB) and mobilized peripheral blood (PBCD34+) being the most accessible HSC sources as collection procedures are less invasive. In this study we compared the capacity of frozen or freshly isolated UCB hematopoietic stem cells (CBCD34+) and frozen PBCD34+ to generate NK cells in vitro. By modifying a previously published protocol, we showed that frozen CBCD34+ cultures generated higher NK cell numbers without loss of function compared to fresh CBCD34+ cultures. NK cells generated from CBCD34+ and PBCD34+ expressed low levels of killer-cell immunoglobulin-like receptors but high levels of activating receptors and of the myeloid marker CD33. However, blocking studies showed that CD33 expression did not impact on the functions of the generated cells. CBCD34+-NK cells exhibited increased capacity to secrete IFN-? and kill K562 in vitro and in vivo as compared to PBCD34+-NK cells. Moreover, K562 killing by the generated NK cells could be further enhanced by IL-12 stimulation. Our data indicate that the use of frozen CBCD34+ for the production of NK cells in vitro results in higher cell numbers than PBCD34+, without jeopardizing their functionality, rendering them suitable for NK cell immunotherapy. The results presented here provide an optimal strategy to generate NK cells in vitro for immunotherapy that exhibit enhanced effector function when compared to alternate sources of HSC.

Luevano, Martha; Domogala, Anna; Blundell, Michael; Jackson, Nicola; Pedroza-Pacheco, Isabela; Derniame, Sophie; Escobedo-Cousin, Michelle; Querol, Sergio; Thrasher, Adrian; Madrigal, Alejandro; Saudemont, Aurore

2014-01-01

105

Frozen cord blood hematopoietic stem cells differentiate into higher numbers of functional natural killer cells in vitro than mobilized hematopoietic stem cells or freshly isolated cord blood hematopoietic stem cells.  

PubMed

Adoptive natural killer (NK) cell therapy relies on the acquisition of large numbers of NK cells that are cytotoxic but not exhausted. NK cell differentiation from hematopoietic stem cells (HSC) has become an alluring option for NK cell therapy, with umbilical cord blood (UCB) and mobilized peripheral blood (PBCD34(+)) being the most accessible HSC sources as collection procedures are less invasive. In this study we compared the capacity of frozen or freshly isolated UCB hematopoietic stem cells (CBCD34(+)) and frozen PBCD34(+) to generate NK cells in vitro. By modifying a previously published protocol, we showed that frozen CBCD34(+) cultures generated higher NK cell numbers without loss of function compared to fresh CBCD34(+) cultures. NK cells generated from CBCD34(+) and PBCD34(+) expressed low levels of killer-cell immunoglobulin-like receptors but high levels of activating receptors and of the myeloid marker CD33. However, blocking studies showed that CD33 expression did not impact on the functions of the generated cells. CBCD34(+)-NK cells exhibited increased capacity to secrete IFN-? and kill K562 in vitro and in vivo as compared to PBCD34(+)-NK cells. Moreover, K562 killing by the generated NK cells could be further enhanced by IL-12 stimulation. Our data indicate that the use of frozen CBCD34(+) for the production of NK cells in vitro results in higher cell numbers than PBCD34(+), without jeopardizing their functionality, rendering them suitable for NK cell immunotherapy. The results presented here provide an optimal strategy to generate NK cells in vitro for immunotherapy that exhibit enhanced effector function when compared to alternate sources of HSC. PMID:24489840

Luevano, Martha; Domogala, Anna; Blundell, Michael; Jackson, Nicola; Pedroza-Pacheco, Isabela; Derniame, Sophie; Escobedo-Cousin, Michelle; Querol, Sergio; Thrasher, Adrian; Madrigal, Alejandro; Saudemont, Aurore

2014-01-01

106

Leaf Shape  

NSDL National Science Digital Library

This illustrated guide is designed to help students recognize and learn the different types of leaf shapes. The single Web page, which can be easily printed for use at field sites, shows five leaf shapes.

107

Down-regulation of SlIAA15 in tomato altered stem xylem development and production of volatile compounds in leaf exudates.  

PubMed

The Aux/IAA family genes encode short-lived nuclear proteins that function as transcriptional regulators in auxin signal transduction. Aux/IAA genes have been reported to control many processes of plant development. Our recent study showed that down-regulation of SlIAA15 in tomato reduced apical dominance, altered pattern of axillary shoot development, increased lateral root formation and leaves thickness. The SlIAA15 suppressed lines display strong reduction of trichome density, suggesting that SlIAA15 is involved in trichome formation. Here, we reported that SlIAA15-suppressed transgenic lines display increased number of xylem cells compared to wild-type plants. Moreover, the monoterpene content in trichome exudates are significantly reduced in SlIAA15 down-regulated leaves. The results provide the roles of SlIAA15 in production of volatile compounds in leaf exudates and xylem development, clearly indicating that members of the Aux/IAA gene family can play distinct and specific functions.  PMID:22836503

Deng, Wei; Yan, Fang; Liu, Minchun; Wang, Xinyu; Li, Zhengguo

2012-08-01

108

Leaf Margins  

NSDL National Science Digital Library

This illustrated guide is designed to help students recognize and learn the difference between entire and toothed leaf margins. The single Web page can be easily printed for use at field sites. Both leaf margin illustrations identify the leaf blade and the petiole.

109

Leaf hydraulic conductance for a tank bromeliad: axial and radial pathways for moving and conserving water.  

PubMed

Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen-Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water. PMID:23596446

North, Gretchen B; Lynch, Frank H; Maharaj, Franklin D R; Phillips, Carly A; Woodside, Walter T

2013-01-01

110

Leaf Hydraulic Conductance for a Tank Bromeliad: Axial and Radial Pathways for Moving and Conserving Water  

PubMed Central

Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen–Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water.

North, Gretchen B.; Lynch, Frank H.; Maharaj, Franklin D. R.; Phillips, Carly A.; Woodside, Walter T.

2013-01-01

111

Leaf-Induced Gibberellin Signaling Is Essential for Internode Elongation, Cambial Activity, and Fiber Differentiation in Tobacco Stems[C][W  

PubMed Central

The gibberellins (GAs) are a group of endogenous compounds that promote the growth of most plant organs, including stem internodes. We show that in tobacco (Nicotiana tabacum) the presence of leaves is essential for the accumulation of bioactive GAs and their immediate precursors in the stem and consequently for normal stem elongation, cambial proliferation, and xylem fiber differentiation. These processes do not occur in the absence of maturing leaves but can be restored by application of C19-GAs, identifying the presence of leaves as a requirement for GA signaling in stems and revealing the fundamental role of GAs in secondary growth regulation. The use of reporter genes for GA activity and GA-directed DELLA protein degradation in Arabidopsis thaliana confirms the presence of a mobile signal from leaves to the stem that induces GA signaling.

Dayan, Jonathan; Voronin, Nickolay; Gong, Fan; Sun, Tai-ping; Hedden, Peter; Fromm, Hillel; Aloni, Roni

2012-01-01

112

WOX13-like genes are required for reprogramming of leaf and protoplast cells into stem cells in the moss Physcomitrella patens.  

PubMed

Many differentiated plant cells can dedifferentiate into stem cells, reflecting the remarkable developmental plasticity of plants. In the moss Physcomitrella patens, cells at the wound margin of detached leaves become reprogrammed into stem cells. Here, we report that two paralogous P. patens WUSCHEL-related homeobox 13-like (PpWOX13L) genes, homologs of stem cell regulators in flowering plants, are transiently upregulated and required for the initiation of cell growth during stem cell formation. Concordantly, ?ppwox13l deletion mutants fail to upregulate genes encoding homologs of cell wall loosening factors during this process. During the moss life cycle, most of the ?ppwox13l mutant zygotes fail to expand and initiate an apical stem cell to form the embryo. Our data show that PpWOX13L genes are required for the initiation of cell growth specifically during stem cell formation, in analogy to WOX stem cell functions in seed plants, but using a different cellular mechanism. PMID:24715456

Sakakibara, Keiko; Reisewitz, Pascal; Aoyama, Tsuyoshi; Friedrich, Thomas; Ando, Sayuri; Sato, Yoshikatsu; Tamada, Yosuke; Nishiyama, Tomoaki; Hiwatashi, Yuji; Kurata, Tetsuya; Ishikawa, Masaki; Deguchi, Hironori; Rensing, Stefan A; Werr, Wolfgang; Murata, Takashi; Hasebe, Mitsuyasu; Laux, Thomas

2014-04-01

113

Enhancing the Number of African Americans Who Pursue STEM PhDs: Meyerhoff Scholarship Program Outcomes, Processes, and Individual Predictors  

PubMed Central

The current study examines the outcomes, processes, and individual predictors of pursuit of a STEM PhD among African-American students in the Meyerhoff Scholarship Program. Meyerhoff students were nearly five times more likely than comparison students to pursue a STEM PhD. Program components consistently rated as important were financial scholarship, being part of the Meyerhoff Program community, the Summer Bridge program, study groups, staff academic advising, and summer research opportunities. Furthermore, focus group findings revealed student internalization of key Meyerhoff Program values, including a commitment to excellence, accountability, group success, and giving back. In terms of individual predictors, multinomial logit regression analyses revealed that Meyerhoff students with higher levels of research excitement at college entry were more likely to pursue a STEM PhD.

Maton, Kenneth I.; Sto Domingo, Mariano R.; Stolle-McAllister, Kathleen E.; Zimmerman, J. Lynn; Hrabowski, Freeman A.

2011-01-01

114

Leaf Activities.  

ERIC Educational Resources Information Center

Leaf activities can provide a means of using basic concepts of outdoor education to learn in elementary level subject areas. Equipment needed includes leaves, a clipboard with paper, and a pencil. A bag of leaves may be brought into the classroom if weather conditions or time do not permit going outdoors. Each student should pick a leaf, examine…

Mingie, Walter

115

Role of algalization in rice growth, yield and incidence of infestation with the stem borerChilo agamemnon Bles. and the leaf minerHydrellia prosternalis Deeming in the Nile Delta.  

PubMed

Blue-green algae as a soil-based inoculum was applied to short-duration Indica rice in combination with 72 kg N/ha and compared with just N fertilization applied as 144 kg N/ha. Fertilizer N was applied in two equal doses 25 days after transplanting and at mid-tillering stage. The algal inoculum, which containedAnabaena cylindrica, Anabaena oryzae, Nostoc muscorum andTolypothrix tenuis, was applied at 100 kg/ha fresh material (90% moisture) 5 days after transplanting. Five different combinations of microelements were sprayed as a foliar application simultaneously with fertilizer N. Plant performance was enhanced by inoculation with algae and microelements compared with complete N fertilization only. Natural infestation with the stem borer,Chilo agamemnon, and leaf miner,Hydrellia prosternalis, decreased significantly during growth and up to harvesting with application of algae, Endosulfan, and increased with application of microelements. PMID:24430137

Yanni, Y G; Abdallah, F E

1990-12-01

116

Are leaf physiological traits related to leaf water isotopic enrichment in restinga woody species?  

PubMed

During plant-transpiration, water molecules having the lighter stable isotopes of oxygen and hydrogen evaporate and diffuse at a faster rate through the stomata than molecules having the heavier isotopes, which cause isotopic enrichment of leaf water. Although previous models have assumed that leaf water is well-mixed and isotopically uniform, non-uniform stomatal closure, promoting different enrichments between cells, and different pools of water within leaves, due to morpho-physiological traits, might lead to inaccuracies in isotopic models predicting leaf water enrichment. We evaluate the role of leaf morpho-physiological traits on leaf water isotopic enrichment in woody species occurring in a coastal vegetation of Brazil known as restinga. Hydrogen and oxygen stable isotope values of soil, plant stem and leaf water and leaf traits were measured in six species from restinga vegetation during a drought and a wet period. Leaf water isotopic enrichment relative to stem water was more homogeneous among species during the drought in contrast to the wet period suggesting convergent responses to deal to temporal heterogeneity in water availability. Average leaf water isotopic enrichment relative to stem water during the drought period was highly correlated with relative apoplastic water content. We discuss this observation in the context of current models of leaf water isotopic enrichment as a function of the Péclet effect. We suggest that future studies should include relative apoplastic water content in isotopic models. PMID:24068091

Rosado, Bruno H P; De Mattos, Eduardo A; Sternberg, Leonel Da S L

2013-09-01

117

Temperature and leaf wetness duration affect phenotypic expression of Rlm6-mediated resistance to Leptosphaeria maculans in Brassica napus.  

PubMed

Near-isogenic Brassica napus lines carrying/lacking resistance gene Rlm6 were used to investigate the effects of temperature and leaf wetness duration on phenotypic expression of Rlm6-mediated resistance. Leaves were inoculated with ascospores or conidia of Leptosphaeria maculans carrying the effector gene AvrLm6. Incubation period to the onset of lesion development, number of lesions and lesion diameter were assessed. Symptomless growth of L. maculans from leaf lesions to stems was investigated using a green fluorescent protein (GFP) expressing isolate carrying AvrLm6. L. maculans produced large grey lesions on Darmor (lacking Rlm6) at 5-25 degrees C and DarmorMX (carrying Rlm6) at 25 degrees C, but small dark spots and 'green islands' on DarmorMX at 5-20 degrees C. With increasing temperature/wetness duration, numbers of lesions/spots generally increased. GFP-expressing L. maculans grew from leaf lesions down leaf petioles to stems on DarmorMX at 25 degrees C but not at 15 degrees C. We conclude that temperature and leaf wetness duration affect the phenotypic expression of Rlm6-mediated resistance in leaves and subsequent L. maculans spread down petioles to produce stem cankers. PMID:16539610

Huang, Yong-Ju; Evans, Neal; Li, Zi-Qin; Eckert, Maria; Chèvre, Anne-Marie; Renard, Michel; Fitt, Bruce D L

2006-01-01

118

Leaf Identification  

NSDL National Science Digital Library

This straightforward tutorial on leaf identification comes from the Department of Horticulture at Penn State University. Simple diagrams, helpful photos, and clear explanations make short work of learning the basics of leaf identification. The website even includes a section on why anyone should bother learning this skill (i.e. it's not just for dedicated horticulturists and botanists). The tutorial covers leaf structure, blade shape, margins, venation, and so on. The self-testing component appears to be unavailable at this time, but this site as a whole is definitely worth a look.

119

Leaf Development  

PubMed Central

Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives.

2013-01-01

120

Leaf development.  

PubMed

Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives. PMID:23864837

Tsukaya, Hirokazu

2013-01-01

121

1123. Adenovirus-Mediated Expression of Sonic Hedgehog Increases the Number of CD34+ Cells in the Epidermal Stem Cell Niche in Hair Follicles  

Microsoft Academic Search

The hair follicle stem cell niche, also known as the “bulge,” contains adult stem cells that give rise to the follicle keratinocytes that generate hair shafts . While epidermal stem cells are utilized cyclically for hair shaft regrowth, epidermal stem cells also contribute progenitor cells of interfollicular epidermis as part of wound repair. Prior work from this laboratory (Sato et

Howard Lou; Andrey Panteleyev; Angela M. Christiano; Ronald G. Crystal; Philip L. Leopold

2005-01-01

122

Antibacterial activity and GC/MS analysis of the essential oils from flower, leaf and stem of Origanum vulgare ssp. viride growing wild in north-west Iran.  

PubMed

Essential oils obtained from flowers, leaves and stems of Origanum vulgare L. ssp. viride (Boiss.) Hayek., growing wild in Ardabil Province (north-west Iran), were analyzed by GC and GC/MS. beta-Caryophyllene was the major constituent in all three oils (48.1%, 50.1% and 60.2%, respectively). Of the 19 components detected in the flower oil, comprising 96.3% of the total, the major components were 1,8-cineole (11.6%), alpha-pinene (6.9%), and gamma-cadinene (4.8%). 1-Octen-3-ol (23.8%), and 1,8-cineole (8.5%) predominated in the leafoil. In the stem oil, other main constituents were bicyclogermacrene (9.8%), 1,8-cineole (6.4%), borneol (5.1%), and pinocarvone (4.4%). The essential oils were evaluated for their antibacterial activity against 10 selected microorganisms. The data obtained contribute to the future use of certain essential oils as natural preservatives for food products, due to their safety and positive effect on shelf life. PMID:21941913

Shafaghat, Ali

2011-09-01

123

Leaf Type  

NSDL National Science Digital Library

This illustrated guide to leaf types is designed to help students understand the differences between compound and simple leaves. This single Web page can be easily printed for use at field sites. Along with an explanation of both types, the guide includes a short description of related terms.

124

Leaf traits and leaf life spans of two xeric-adapted palmettos.  

PubMed

Plants of nutrient-poor, arid environments often have leaf traits that include small size, sclerophylly, long life span, low nutrient concentration, and low photosynthetic rate. Hence, the success of two large-leaved palmettos in peninsular Florida's seasonally xeric, nutrient-impoverished uplands seems anomalous, given that their leaves are orders of magnitude larger than the leaves of sympatric species. An examination of a 16-yr data set of leaf traits and leaf life spans across four vegetative associations differing in available light showed that Serenoa repens and Sabal etonia had low rates of leaf production coupled with long leaf life spans reaching 3.5 yr in heavily shaded plants. The adaptation of these palmettos to xeric, nutrient-poor habitats has generated dwarf statures, diminished leaf sizes and numbers, increased leaf life spans, and reduced rates of leaf production relative to other palms and congeners of more mesic sites. Leaf and petiole size, plant leaf canopy area, and leaf life span increased in both palmettos with decreasing available light, helping to compensate for reduced photosynthetic rates under shaded conditions and for the high leaf construction costs of the large, thick palmetto leaves. Large leaf size in these palmettos, likely due to phylogenetic conservatism, is compensated by other leaf traits (e.g., heavily cutinized epidermises, thick laminas) that increase survival in seasonally xeric, nutrient-impoverished environments. PMID:21636496

Abrahamson, Warren G

2007-08-01

125

7 CFR 29.3153 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...grown above the midpoint of the stalk. Cured leaves from the upper stalk position have a tendency to fold, concealing the face of the leaf and exposing the stem or midrib. These leaves have a pointed tip and generally are...

2009-01-01

126

7 CFR 29.3153 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...grown above the midpoint of the stalk. Cured leaves from the upper stalk position have a tendency to fold, concealing the face of the leaf and exposing the stem or midrib. These leaves have a pointed tip and generally are...

2010-01-01

127

The increased number of Leydig cells by di(2-ethylhexyl) phthalate comes from the differentiation of stem cells into Leydig cell lineage in the adult rat testis.  

PubMed

The objective of the present study is to determine whether di(2-ethylhexyl) phthalate (DEHP) exposure at adulthood increases rat Leydig cell number and to investigate the possible mechanism. 90-day-old Long-Evans rats were randomly divided into 3 groups, and were gavaged with the corn oil (control) or 10 or 750 mg/kg DEHP daily for 7 days, and then received an intraperitoneal injection of 75 mg/kg ethane dimethanesulfonate (EDS) to eliminate Leydig cells. Serum testosterone concentrations were assessed by RIA, and the mRNA levels of Leydig cell genes were measured by qPCR. EDS eliminated all Leydig cells in the control testis on day 4 post-EDS, as judged by undetectable serum testosterone level and no 3?-hydroxysteroid dehydrogenase positive (3?-HSD(pos)) cells in the interstitium. However, in DEHP-treated groups, there were detectable serum testosterone concentrations and some oval-shaped 3?-HSD(pos) cells in the interstitium. These 3?-HSD(pos) cells were not stained by the antibody against 11?-hydroxysteroid dehydrogenase 1 (11?-HSD1), a marker for Leydig cells at a more advanced stage. The disappearance of mRNAs of Leydig cell biomarkers including Lhcgr, Cyp11a1, Cyp17a1, Insl3 and Hsd11b1 in the control testis was observed on day 4 post-EDS. However, there were detectable concentrations of Lhcgr, Cyp11a1 and Cyp17a1 mRNAs but undetectable concentrations of Insl3, Hsd17b3 and Hsd11b1 in the DEHP-treated testes, indicating that these 3?-HSD(pos) cells were newly formed progenitor Leydig cells. The mRNA level for nestin (Nes, biomarker for stem Leydig cells) was significantly increased in the control testis on day 4 post-EDS, but not in the DEHP treated testes, suggesting that these nestin positive stem cells were differentiated into progenitor Leydig cells in the DEHP-treated testes. The present study suggests that DEHP increases the differentiation of stem cells into progenitor Leydig cells. PMID:23391632

Guo, Jingjing; Li, Xing-Wang; Liang, Yong; Ge, Yufei; Chen, Xiaomin; Lian, Qing-Quan; Ge, Ren-Shan

2013-04-01

128

The Analysis of Leaf Shape Using Fractal Geometry.  

ERIC Educational Resources Information Center

Describes ways to examine leaf structure and shape using fractal geometry. Students can test hypotheses using the leaves of replicated plants to look for non-linear trends in leaf shape along the stems of plants, across species, and under different environmental growth conditions. (SAH)

Hartvigsen, Gregg

2000-01-01

129

Genetics of Stem Rust Resistance in Wheat Cvs. Pasqua and AC Taber.  

PubMed

ABSTRACT Canadian wheat cvs. Pasqua and AC Taber were examined genetically to determine the number and identity of stem rust resistance genes in both. The two cultivars were crossed with stem rust susceptible line RL6071, and sets of random F(6) lines were developed from each cross. The F(6) lines, parents, and tester lines with single stem rust resistance genes were grown in a field rust nursery, inoculated with a mixture of stem and leaf rust races, and evaluated for rust resistance. The same wheat lines were tested by inoculation with specific stem rust races in seedling tests to postulate which Sr genes were segregating in the F6 lines. Segregation of F(6) lines indicated that Pasqua had three genes that conditioned field resistance to stem rust and had seedling genes Sr5, Sr6, Sr7a, Sr9b, and Sr12. Leaf rust resistance gene Lr34, which is in Pasqua, was associated with adult-plant stem rust resistance in the segregating F(6) lines. Adult-plant gene Sr2 was postulated to condition field resistance in AC Taber, and seedling genes Sr9b, Sr11, and Sr12 also were postulated to be in AC Taber. PMID:18944987

Liu, J Q; Kolmer, J A

1998-02-01

130

Assessing Soybean Leaf Area and Leaf Biomass by Spectral Measurements.  

National Technical Information Service (NTIS)

Red and photographic infrared spectral radiances were correlated with soybean total leaf area index, green leaf area index, chlorotic leaf area index, green leaf biomass, chlorotic leaf biomass, and total biomass. The most significant correlations were fo...

B. N. Holben C. J. Fan C. J. Tucker

1979-01-01

131

Plant Protection. Volume 22, Number 114, 1971.  

National Technical Information Service (NTIS)

Contents: Stem nematode (Ditylenchus dipsaci) with reference to host plants in Serbia; Contribution to the study of natural enemies of the Ceral Leaf Beetle (Lema melanopa) in Yugoslavia; A study of the morphology and ecology of Phyllosticta prunicola; In...

1973-01-01

132

Stem Cells  

MedlinePLUS

Stem cells are cells with the potential to develop into many different types of cells in the body. They serve as a repair ... body. There are two main types of stem cells: embryonic stem cells and adult stem cells. Stem ...

133

The combination of inhibitors of FGF/MEK/Erk and GSK3? signaling increases the number of OCT3/4- and NANOG-positive cells in the human inner cell mass, but does not improve stem cell derivation.  

PubMed

In embryonic stem cell culture, small molecules can be used to alter key signaling pathways to promote self-renewal and inhibit differentiation. In mice, small-molecule inhibition of both the FGF/MEK/Erk and the GSK3? pathways during preimplantation development suppresses hypoblast formation, and this results in more pluripotent cells of the inner cell mass (ICM). In this study, we evaluated the effects of different small-molecule inhibitors of the FGF/MEK/Erk and GSK3? pathway on embryo preimplantation development, early lineage segregation, and subsequent embryonic stem cell derivation in the humans. We did not observe any effect on blastocyst formation, but small-molecule inhibition did affect the number of OCT3/4- and NANOG-positive cells in the human ICM. We found that combined inhibition of the FGF/MEK/Erk and GSK3? pathways by PD0325901 and CHIR99021, respectively, resulted in ICMs containing significantly more OCT3/4-positive cells. Inhibition of FGF/MEK/Erk alone as well as in combination with inhibition of GSK3? significantly increased the number of NANOG-positive cells in blastocysts possessing good-quality ICMs. Secondly, we verified the influence of this increased pluripotency after 2i culture on the efficiency of stem cell derivation. Similar human embryonic stem cell (hESC) derivation rates were observed after 2i compared to control conditions, resulting in 2 control hESC lines and 1 hESC line from an embryo cultured in 2i conditions. In conclusion, we demonstrated that FGF/MEK/Erk and GSK3? signaling increases the number of OCT3/4- and NANOG-positive cells in the human ICM, but does not improve stem cell derivation. PMID:22784186

Van der Jeught, Margot; O'Leary, Thomas; Ghimire, Sabitri; Lierman, Sylvie; Duggal, Galbha; Versieren, Karen; Deforce, Dieter; Chuva de Sousa Lopes, Susana; Heindryckx, Björn; De Sutter, Petra

2013-01-15

134

The Combination of Inhibitors of FGF/MEK/Erk and GSK3? Signaling Increases the Number of OCT3/4- and NANOG-Positive Cells in the Human Inner Cell Mass, But Does Not Improve Stem Cell Derivation  

PubMed Central

In embryonic stem cell culture, small molecules can be used to alter key signaling pathways to promote self-renewal and inhibit differentiation. In mice, small-molecule inhibition of both the FGF/MEK/Erk and the GSK3? pathways during preimplantation development suppresses hypoblast formation, and this results in more pluripotent cells of the inner cell mass (ICM). In this study, we evaluated the effects of different small-molecule inhibitors of the FGF/MEK/Erk and GSK3? pathway on embryo preimplantation development, early lineage segregation, and subsequent embryonic stem cell derivation in the humans. We did not observe any effect on blastocyst formation, but small-molecule inhibition did affect the number of OCT3/4- and NANOG-positive cells in the human ICM. We found that combined inhibition of the FGF/MEK/Erk and GSK3? pathways by PD0325901 and CHIR99021, respectively, resulted in ICMs containing significantly more OCT3/4-positive cells. Inhibition of FGF/MEK/Erk alone as well as in combination with inhibition of GSK3? significantly increased the number of NANOG-positive cells in blastocysts possessing good-quality ICMs. Secondly, we verified the influence of this increased pluripotency after 2i culture on the efficiency of stem cell derivation. Similar human embryonic stem cell (hESC) derivation rates were observed after 2i compared to control conditions, resulting in 2 control hESC lines and 1 hESC line from an embryo cultured in 2i conditions. In conclusion, we demonstrated that FGF/MEK/Erk and GSK3? signaling increases the number of OCT3/4- and NANOG-positive cells in the human ICM, but does not improve stem cell derivation.

O'Leary, Thomas; Ghimire, Sabitri; Lierman, Sylvie; Duggal, Galbha; Versieren, Karen; Deforce, Dieter; Chuva de Sousa Lopes, Susana; Heindryckx, Bjorn; De Sutter, Petra

2013-01-01

135

Long-term Blue Light Effects on the Histology of Lettuce and Soybean Leaves and Stems  

NASA Technical Reports Server (NTRS)

Blue light (320 to 496 nm) alters hypocotyl and stem elongation and leaf expansion in short-term, cell-level experiments, but histological effects of blue light in long-term studies of whole plants have not been described. We measured cell size and number in stems of soybean (Glycine max L.) and leaves of soybean and lettuce (Lactuca sativa L.), at two blue light fractions. Short-term studies have shown that cell expansion in stems is rapidly inhibited when etiolated tissue is exposed to blue light. However, under long-term light exposure, an increase in the blue light fraction from less than 0.1% to 26% decreased internode length, specifically by inhibiting soybean cell division in stems. In contrast, an increase in blue light fraction from 6% to 26% reduced soybean leaf area by decreasing cell expansion. Surprisingly, lettuce leaf area increased with increasing blue light fraction (0% to 6%), which was attributed to a 3.1-fold increase in cell expansion and a 1.6-fold increase in cell division.

Dougher, Tracy A. O.; Bugbee, Bruce

2004-01-01

136

Xylem Cavitation in the Leaf of Prunus laurocerasus and Its Impact on Leaf Hydraulics1  

PubMed Central

This paper reports how water stress correlates with changes in hydraulic conductivity of stems, leaf midrib, and whole leaves of Prunus laurocerasus. Water stress caused cavitation-induced dysfunction in vessels of P. laurocerasus. Cavitation was detected acoustically by counts of ultrasonic acoustic emissions and by the loss of hydraulic conductivity measured by a vacuum chamber method. Stems and midribs were approximately equally vulnerable to cavitations. Although midribs suffered a 70% loss of hydraulic conductance at leaf water potentials of ?1.5 MPa, there was less than a 10% loss of hydraulic conductance in whole leaves. Cutting and sealing the midrib 20 mm from the leaf base caused only a 30% loss of conduction of the whole leaf. A high-pressure flow meter was used to measure conductance of whole leaves and as the leaf was progressively cut back from tip to base. These data were fitted to a model of hydraulic conductance of leaves that explained the above results, i.e. redundancy in hydraulic pathways whereby water can flow around embolized regions in the leaf, makes whole leaves relatively insensitive to significant changes in conductance of the midrib. The onset of cavitation events in P. laurocerasus leaves correlated with the onset of stomatal closure as found recently in studies of other species in our laboratory.

Nardini, Andrea; Tyree, Melvin T.; Salleo, Sebastiano

2001-01-01

137

Root Hypoxia Reduces Leaf Growth 1  

PubMed Central

This study examined the potential role of restricted phloem export, or import of substances from the roots in the leaf growth response to root hypoxia. In addition, the effects of root hypoxia on abscisic acid (ABA) and zeatin riboside (ZR) levels were measured and their effects on in vitro growth determined. Imposition of root hypoxia in the dark when transpirational water flux was minimal delayed the reduction in leaf growth until the following light period. Restriction of phloem transport by stem girdling did not eliminate the hypoxia-induced reduction in leaf growth. In vitro growth of leaf discs was inhibited in the presence of xylem sap collected from hypoxic roots, and also by millimolar ABA. Disc growth was promoted by sap from aerated roots and by 0.1 micromolar ZR. The flux of both ABA and ZR was reduced in xylem sap from hypoxic roots. Leaf ABA transiently increased twofold after 24 hours of hypoxia exposure but there were no changes in leaf cytokinin levels. Images Figure 3 Figure 4

Smit, Barbara A.; Neuman, Dawn S.; Stachowiak, Matthew L.

1990-01-01

138

7 CFR 29.1061 - Stem.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Stem. 29.1061 Section 29.1061 Agriculture...14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf. [42 FR 21092, Apr. 25, 1977....

2009-01-01

139

7 CFR 29.2553 - Stem.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Stem. 29.2553 Section 29.2553 Agriculture...23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf. [37 FR 13626, July 12, 1972....

2009-01-01

140

7 CFR 29.3059 - Stem.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Stem. 29.3059 Section 29.3059 Agriculture...Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf. [24 FR 8771, Oct. 29, 1959....

2009-01-01

141

7 CFR 29.2553 - Stem.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Stem. 29.2553 Section 29.2553 Agriculture...23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf. [37 FR 13626, July 12, 1972....

2010-01-01

142

Leaf life span spectrum of tropical woody seedlings: effects of light and ontogeny and consequences for survival  

PubMed Central

Background and Aims Leaf life span is widely recognized as a key life history trait associated with herbivory resistance, but rigorous comparative data are rare for seedlings. The goal of this study was to examine how light environment affects leaf life span, and how ontogenetic development during the first year may influence leaf fracture toughness, lamina density and stem density that are relevant for herbivory resistance, leaf life span and seedling survival. Methods Data from three experiments encompassing 104 neotropical woody species were combined. Leaf life span, lamina and vein fracture toughness, leaf and stem tissue density and seedling survival were quantified for the first-year seedlings at standardized ontogenetic stages in shade houses and common gardens established in gaps and shaded understorey in a moist tropical forest in Panama. Mortality of naturally recruited seedlings till 1 year later was quantified in 800 1-m2 plots from 1994 to 2011. Key Results Median leaf life span ranged widely among species, always greater in shade (ranging from 151 to >1790 d in the understorey and shade houses) than in gaps (115–867 d), but with strong correlation between gaps and shade. Leaf and stem tissue density increased with seedling age, whereas leaf fracture toughness showed only a weak increase. All these traits were positively correlated with leaf life span. Leaf life span and stem density were negatively correlated with seedling mortality in shade, while gap mortality showed no correlation with these traits. Conclusions The wide spectrum of leaf life span and associated functional traits reflects variation in shade tolerance of first-year seedlings among coexisting trees, shrubs and lianas in this neotropical forest. High leaf tissue density is important in enhancing leaf toughness, a known physical defence, and leaf life span. Both seedling leaf life span and stem density should be considered as key functional traits that contribute to seedling survival in tropical forest understoreys.

Kitajima, Kaoru; Cordero, Roberto A.; Wright, S. Joseph

2013-01-01

143

Can meristematic activity determine variation in leaf size and elongation rate among four Poa species? A kinematic study.  

PubMed

We studied inherent variation in final leaf size among four Poa spp. that live at different elevations. The average final length of leaf 7 of the main stem of the smallest species (Poa alpina) was only one-half that of the largest species (Poa trivialis); it was correlated with leaf elongation rate, but not with the duration of leaf elongation. A faster rate of leaf elongation rate was associated with (a) larger size of the zone of cell expansion, and (b) faster rates of cell production (per cell file) in the meristem, which in turn were due to greater numbers of dividing cells, whereas average cell division rates were very similar for all species (except Poa annua). Also we found that the proliferative fraction equaled 1 throughout the meristem in all species. It was remarkable that rates of cell expansion tended to be somewhat higher in the species with slower growing leaves. We discuss the results by comparing the spatial and material viewpoints, which lead to different interpretations of the role of cell division. Although the presented data do not strictly prove it, they strongly suggest a regulatory role for cell division in determining differences in growth rate among the present four Poa spp. PMID:11027732

Fiorani, F; Beemster, G T; Bultynck, L; Lambers, H

2000-10-01

144

Can Meristematic Activity Determine Variation in Leaf Size and Elongation Rate among Four Poa Species? A Kinematic Study1  

PubMed Central

We studied inherent variation in final leaf size among four Poa spp. that live at different elevations. The average final length of leaf 7 of the main stem of the smallest species (Poa alpina) was only one-half that of the largest species (Poa trivialis); it was correlated with leaf elongation rate, but not with the duration of leaf elongation. A faster rate of leaf elongation rate was associated with (a) larger size of the zone of cell expansion, and (b) faster rates of cell production (per cell file) in the meristem, which in turn were due to greater numbers of dividing cells, whereas average cell division rates were very similar for all species (except Poa annua). Also we found that the proliferative fraction equaled 1 throughout the meristem in all species. It was remarkable that rates of cell expansion tended to be somewhat higher in the species with slower growing leaves. We discuss the results by comparing the spatial and material viewpoints, which lead to different interpretations of the role of cell division. Although the presented data do not strictly prove it, they strongly suggest a regulatory role for cell division in determining differences in growth rate among the present four Poa spp.

Fiorani, Fabio; Beemster, Gerrit T.S.; Bultynck, Lieve; Lambers, Hans

2000-01-01

145

Testing the generality of the ‘leafing intensity premium’ hypothesis in temperate broad-leaved forests: a survey of variation in leaf size within and between habitats  

Microsoft Academic Search

Because leaf size scales negatively and isometrically with leaf number per shoot size (leafing intensity) in woody species,\\u000a and because most tree and shrub species have small leaves, Kleiman and Aarssen (J Ecol 95:376–382, 2007) recently proposed that natural selection favors high leafing intensity resulting in small leaves, i.e., the leafing-intensity-premium\\u000a hypothesis. However, empirical evidence for or against this hypothesis

Shuang XiangNing; Ning Wu; Shucun Sun

2010-01-01

146

Identification of Plant Using Leaf Image Analysis  

NASA Astrophysics Data System (ADS)

The trees are basically identified by their leaves. There are different varieties of trees grown throughout the world. Some are important cash crop. Some are used in medicine. The tree identification is very important in day to day life. Their identifications had been studied using various laboratory methods. The morphological and genetically characteristics were employed to classify different leafs. However, the presence of wide morphological varieties through evolution among the various leaf cultivars made it more complex and difficult to classify them. Therefore manual identification as well as classification of these leaves is a tedious task. During the last few decades computational biologists have studied various diversities among leaf due to huge number of evolutionary changes. Leaf structures play a very crucial role in determining the characteristics of a plant. The broad and narrow shaped leaves, leaf arrangement, leaf margin characteristics features which differentiate various leaf of a tree. This project proposed the methods to identify the leaf using an image analysis based approach.

Pramanik, Subhra; Bandyopadhyay, Samir Kumar; Bhattacharyya, Debnath; Kim, Tai-Hoon

147

Two WUSCHEL-related homeobox genes, narrow leaf2 and narrow leaf3, control leaf width in rice.  

PubMed

Leaf shape is one of the key determinants of plant architecture. Leaf shape also affects the amount of sunlight captured and influences photosynthetic efficiency; thus, it is an important agronomic trait in crop plants. Understanding the molecular mechanisms governing leaf shape is a central issue of plant developmental biology and agrobiotechnology. Here, we characterized the narrow-leaf phenotype of FL90, a linkage tester line of rice (Oryza sativa). Light and scanning electron microscopic analyses of FL90 leaves revealed defects in the development of marginal regions and a reduction in the number of longitudinal veins. The narrow-leaf phenotype of FL90 shows a two-factor recessive inheritance and is caused by the loss of function of two WUSCHEL-related homeobox genes, NAL2 and NAL3 (NAL2/3), which are duplicate genes orthologous to maize NS1 and NS2 and to Arabidopsis PRS. The overexpression of NAL2/3 in transgenic rice plants results in wider leaves containing increased numbers of veins, suggesting that NAL2/3 expression regulates leaf width. Thus, NAL2/3 can be used to modulate leaf shape and improve agronomic yield in crop plants. PMID:23420902

Ishiwata, Aiko; Ozawa, Misa; Nagasaki, Hiroshi; Kato, Makio; Noda, Yusaku; Yamaguchi, Takahiro; Nosaka, Misuzu; Shimizu-Sato, Sae; Nagasaki, Akie; Maekawa, Masahiko; Hirano, Hiro-Yuki; Sato, Yutaka

2013-05-01

148

Evaluation of stem injection for managing giant reed (Arundo donax).  

PubMed

Giant reed is an emergent aquatic plant that may be weedy in riparian habitats. Two herbicides approved for controlling giant reed in the US are glyphosate (N-(phosphonomethyl) glycine) and imazapyr (2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid). Foliar applications of these herbicides may be restricted in some areas, such as those, which are within the range of threatened or endangered species. We conducted two field experiments at sites in northern and central California. The first experiment evaluated the effects of three aquatic herbicides (glyphosate, imazapyr, and triclopyr [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid) injected into all of the stems within a giant reed (5 mL stem(-1)). In this experiment, leaf chlorophyll content, the proportion of living stems, and the number of new stems produced during the year after treatment declined (>80%) following injection of either full strength glyphosate or imazapyr. The effects of injecting full strength triclopyr were considerably less. In a second experiment, different proportions (0, 10%, 25%, or 100%) of the stems within a plant were injected with full strength glyphosate. Results indicated that it was necessary to inject all of the stems within a clump to achieve the greatest reduction in the plant growth characteristics measured. These results imply that giant reed may be successfully controlled by injecting full strength glyphosate (5 mL stem(-1)) into all of the stems within a clump. While labor intensive and thus potentially more costly this method, offers a new method for managing giant reed in sensitive sites where foliar spray applications may be restricted. PMID:25035911

Spencer, David F

2014-09-01

149

Leaf Epicuticular Waxes of the Eceriferum Mutants in Arabidopsis.  

PubMed Central

Wild-type Arabidopsis leaf epicuticular wax (EW) occurs as a smooth layer over the epidermal surface, whereas stem EW has a crystalline microstructure. Wild-type EW load was more than 10-fold lower on leaves than on stems. Compared with the EW on wild-type stems, EW on wild-type leaves had a much higher proportion of their total EW load in the form of alkanes and 1-alcohols; a large reduction in secondary alcohols, ketones, and esters; and a chain-length distribution for major EW classes that was skewed toward longer lengths. The eceriferum (cer) mutations often differentially affected leaf and stem EW chemical compositions. For example, the cer2 mutant EW phenotype was expressed on the stem but not on the leaf. Compared to wild type, the amount of primary alcohols on cer9 mutants was reduced on leaves but elevated on stems, whereas an opposite differential effect for primary alcohols was observed on cer16 leaves and stems. Putative functions for CER gene products are discussed. The CER4 and CER6 gene products may be involved in fatty aldehyde reduction and C26 fatty acylcoenzyme A elongation, respectively. CER1, CER8, CER9, and CER16 gene products may be involved in EW substrate transfer. The CER3 gene product may be involved in release of fatty acids from elongase complexes. CER2 gene product may have regulatory functions.

Jenks, M. A.; Tuttle, H. A.; Eigenbrode, S. D.; Feldmann, K. A.

1995-01-01

150

Relationship Between Tree Density, Leaf Area Index, Soil Metal Content, and LANDSAT MSS Canopy Radiance Values.  

National Technical Information Service (NTIS)

Measurements from a coniferous tree stand in soils containing high concentrations of copper, lead, and zinc of soil metal concentrations and tree density and stem diameter helped to establish relationships between canopy structure (stand density and leaf ...

C. Banninger

1986-01-01

151

Pluripotent stem cells  

Microsoft Academic Search

The isolation of human embryonic stem cells (ESC) in 1998 has created the hope that stem cells will one day be used to regenerate tissues and organs, even though it is obvious that a number of hurdles will need to be overcome for such therapies to become reality. The cloning of “Dolly” in 1997, more than 40 years after the first

C. Verfaillie

2009-01-01

152

Leaf Pack Network  

NSDL National Science Digital Library

The Leaf Pack Network (LPN) is a network of teachers and students investigating their local stream ecosystems by participating in the leaf pack experiment, which involves creating an artificial leaf pack (dry leaves in a mesh bag), immersing it in a stream for 3-4 weeks, and examining it for signs of aquatic insects as indicators of stream health. Participating classrooms share their data through the internet. This activity highlights the connection between streamside forests and the ecology of rivers and streams.

153

Methods of Screening Rices for Varietal Resistance to 'Cercospora' Leaf Spot.  

National Technical Information Service (NTIS)

Autoclaved rice stem nodes with prune juice provide a favorable medium for the isolation of Cercospora Oryzae, the fungus causing Cercospora leaf spot on narrow brown leaf spot, and for the mass production of spores. Spraying of spores in late afternoon r...

B. A. Estrada S. H. Ou

1978-01-01

154

Use of microdilution to assess in vitro antiamoebic activities of Brucea javanica fruits, Simarouba amara stem, and a number of quassinoids.  

PubMed Central

A microdilution technique for the assessment of in vitro activity against Entamoeba histolytica was devised and validated with metronidazole. The test was used to detect the antiamoebic activities of plant extracts prepared from the traditional remedies Brucea javanica fruits and Simarouba amara stems. The activity was associated with quassinoid-containing fractions. The 50% inhibitory concentrations for some quassinoids against amoebae were determined by using the microdilution method. These concentrations ranged from 0.019 micrograms.ml-1 for bruceantin, the most active quassinoid, to greater than 5 micrograms.ml-1 for glaucarubol, the least active compound tested. These results are discussed with reference to the known activities of these compounds against Plasmodium falciparum. Overall, the activities of the quassinoids against both protozoa are similar. The microdilution technique will be useful in the search for novel antiamoebic drugs.

Wright, C W; O'Neill, M J; Phillipson, J D; Warhurst, D C

1988-01-01

155

An Apparent Anomaly in Peanut Leaf Conductance  

PubMed Central

Conductance to gaseous transfer is normally considered to be greater from the abaxial than from the adaxial side of a leaf. Measurements of the conductance to water vapor of peanut leaves (Arachis hypogaea L.) under well watered and stress conditions in a controlled environment, however, indicated a 2-fold higher conductance from the adaxial side of the leaf than from the abaxial. Studies of conductance as light level was varied showed an increase in conductance from either surface with increasing light level, but conductance was always greater from the adaxial surface at any given light level. In contrast, measurements of soybean (Glycine max [L.] Merr.) and snapbean (Phaseolus vulgaris L.) leaf conductance showed an approximate 2-fold greater conductance from the abaxial surface than from the adaxial. Approximately the same number of stomata were present on both peanut leaf surfaces and stomatal size was similar. Electron microscopic examination of peanut leaves did not reveal any major structural differences between stomata on the two surfaces that would account for the differences in conductance. Light microscope studies of leaf sections revealed an extensive network of bundle sheaths with achloraplastic bundle sheath extensions; the lower epidermis was lined with a single layer of large achloraplastic parenchyma cells. Measurements of net photosynthesis made on upper and lower leaf surfaces collectively and individually indicated that two-thirds of the peanut leaf's total net photosynthesis can be attributed to diffusion of CO2 through the adaxial leaf surface. Possibly the high photosynthetic efficiency of peanut cultivars as compared with certain other C3 species is associated with the greater conductance of CO2 through their upper leaf surfaces. Images

Pallas, James E.

1980-01-01

156

Leaf Sequencing Method and System.  

National Technical Information Service (NTIS)

A method of delivering radiation treatment using multi-leaf collimation includes the step of providing a radiation fluence map which includes an intensity profile. The fluence map is converted into a preliminary leaf sequence, wherein the preliminary leaf...

J. Palta J. G. Li S. Kamath S. Ranka S. Sahni

2003-01-01

157

Changes in the number of CD8? T lymphocytes in the peripheral blood of patients with various autoimmune diseases after autologous hematopoietic stem cell transplantations and their relations to the survival times.  

PubMed

The changes in the number of CD8? T lymphocytes were studied before (0 day) and then 30 days after the autologous hematopoietic stem cell transplantations (AHSCT) in 14 therapy refractory patients with autoimmune diseases. The years of survival and the clinical states were also evaluated. The number of CD8? T cells was determined by an hematologic automat and by flow cytometry. Longer than 5-year survival times were found in 6 cases, whereas there was no progression (improvement) in 2 cases, and 4 patients were lost. The increase in the number of CD8? cytotoxic T cells was gradual in the first 2 months and reached the significantly highest values among all subtypes of lymphocytes. It was of a special interest that in all the 4 patients who died, the numbers of CD8? T cells were less than 150/?l on the 30th day after AHSCT, whereas all the 10 patients with a higher cell number survived. These results suggest that the early monitoring of the number (not only the ratio) of regenerating CD8? T cells in the peripheral blood can be a useful and quantitative laboratory measurement after AHSCT, and it has a significant relation also to the survival times of transplanted patients. PMID:23934041

Váróczy, László; Kovács, Ildikó; Baráth, Sándor; Gyimesi, Edit; Illés, Árpád; Zeher, Margit; Sipka, Sándor

2013-10-01

158

The effects of adding picoxystrobin, azoxystrobin and nitrogen to a triazole programme on disease control, flag leaf senescence, yield and grain quality of winter wheat  

Microsoft Academic Search

The effect of adding strobilurins to a triazole (epoxiconazole) fungicide programme on the quality of a range of wheat cultivars was assessed in field experiments in three successive years. Strobilurin was applied at just flag leaf emergence (azoxystrobin) or at the start of stem extension (azoxystrobin or picoxystrobin) and again at flag leaf emergence or at flag leaf emergence and

R. E. Ruske; M. J. Gooding; S. A. Jones

2003-01-01

159

Regeneration of peppermint and orange mint from leaf disks  

Microsoft Academic Search

Leaf disks from peppermint, spearmint, orange mint, lavender mint and Scotch spearmint were cultured on various Murashige-Skoog-based media in order to regenerate shoots. A significantly larger average number of orange mint leaf disks regenerated shoots on basal medium containing 44.4 µM benzyladenine (BA) and 250 ml l-1 coconut water (CW). Shoots regenerated from peppermint leaf disks cultured on basal medium

J. M. Van Eck; S. L. Kitto

1992-01-01

160

Functional coordination between leaf gas exchange and vulnerability to xylem cavitation in temperate forest trees  

Microsoft Academic Search

We examined functional coordination among stem and root vulnerability to xylem cavitation, plant water transport characteristics and leaf traits in 14 co-occurring temperate tree species. Relationships were evaluated using both tra- ditional cross-species correlations and phylogenetically independent contrast (PIC) correlations. For stems, the xylem tension at which 50% of hydraulic conductivity was lost ( ? ? ? ? 50 )

H. Maherali; CATARINA F. MOURA; MARIA C. CALDEIRA; CYNTHIA J. WILLSON; ROBERT B. JACKSON

2005-01-01

161

Four-Leaf Clover  

NSDL National Science Digital Library

Scientist-in-training Summer Praetorius has an unusual skillâshe is really, really good at spotting four-leaf clovers (Trifolium repens L.). A single gene causes the normally three-leafed clover to produce a fourth, supposedly lucky, leaf. As it turns out, good science depends on both close observationâa skill Praetorius uses to spot tiny shelled animals called foraminiferaâand a little bit of luck. Ari Daniel Shapiro explains. Also included is a Learn More section that provides background information on the scientists recorded in the podcast, lessons, images, and cool facts.

2009-01-01

162

Leaf-wax n-alkanes record the plant-water environment at leaf flush  

PubMed Central

Leaf-wax n-alkanes 2H/1H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes ?2H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant ?2H value and monitored the ?2H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the ?2H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found ?2H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation ?2H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were 2H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed 2H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax ?2H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane ?2H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season.

Tipple, Brett J.; Berke, Melissa A.; Doman, Christine E.; Khachaturyan, Susanna; Ehleringer, James R.

2013-01-01

163

Leaf-wax n-alkanes record the plant-water environment at leaf flush.  

PubMed

Leaf-wax n-alkanes (2)H/(1)H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes ?(2)H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant ?(2)H value and monitored the ?(2)H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the ?(2)H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found ?(2)H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation ?(2)H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were (2)H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed (2)H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax ?(2)H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane ?(2)H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season. PMID:23359675

Tipple, Brett J; Berke, Melissa A; Doman, Christine E; Khachaturyan, Susanna; Ehleringer, James R

2013-02-12

164

Microscopic evaluation and physiochemical analysis of Dillenia indica leaf  

PubMed Central

Objective To study detail microscopic evaluation and physiochemical analysis of Dillenia indica (D. indica) leaf. Methods Fresh leaf sample and dried power of the leaf were studied macroscopically and microscopically. Preliminary phytochemical investigation of plant material was done. Other WHO recommended parameters for standardizations were also performed. Results The detail microscopy revealed the presence of anomocytic stomata, unicellular trichome, xylem fibres, calcium oxalate crystals, vascular bundles, etc. Leaf constants such as stomatal number, stomatal index, vein-islet number and veinlet termination numbers were also measured. Physiochemical parameters such as ash values, loss on drying, extractive values, percentage of foreign matters, swelling index, etc. were also determined. Preliminary phytochemical screening showed the presence of steroids, terpenoids, glycosides, fatty acids, flavonoids, phenolic compounds and carbohydrates. Conclusions The microscopic and physiochemical analysis of the D. indica leaf is useful in standardization for quality, purity and sample identification.

Kumar, S; Kumar, V; Prakash, Om

2011-01-01

165

STEM Career  

NSDL National Science Digital Library

There are many groups and organizations in the United States working to encourage young people to enter STEM-related careers, and this website represents one of those endeavors. The STEM Career website was created by Professor Rich Feller of Colorado State University to help encourage young people to select just such a career path. The website contains updates on STEM career possibilities, and basic answers to questions like "Why STEM?" and "Why STEM Centric Career Development?" Visitors should also scan through the "STEM Disciplines" area on the homepage, as it contains resources about the job outlook for related STEM disciplines, such as biochemical engineering and engineering managers. Moving on, the site also features news updates from Professor Feller and his colleagues on subjects that include the ways in which corporations are promoting STEM education and women in STEM.

166

Hydroxy-beta-Diketones from Wheat Leaf Wax.  

National Technical Information Service (NTIS)

A mixture of hydroxy-beta-diketones, 8- and 9-hydroxyhentriacontane-14, 16-dione was isolated from the leaf-surface wax of the wheat Triticum compactum Host. var. Little Club. Long-chain-beta-diketones have been found in the leaf-surface waxes of a number...

A. P. Tulloch R. O. Weenink

1966-01-01

167

Electronic Leaf Project  

NSDL National Science Digital Library

This article demonstrates the benefits of a direct application of technology into a science classroom by transferring a traditional activity, such as leaf identification, into an electronic format. The new dynamic medium possesses attributes that can enha

Houston, Carolyn; Hargis, Jace

2000-05-01

168

Leaf to Landscape  

Microsoft Academic Search

\\u000a Temporal dynamics and structural complexity of plant canopies strongly affect light harvesting, generating variable spatio-temporal\\u000a distributions of the irradiance on leaf area (Baldocchi and Collineau 1994). Leaf light interception scales linearly with\\u000a incident irradiance, but plant photosynthesis and photomorphogenesis typically exhibit a saturating response to light. Because\\u000a of the inherent nonlinearity in light responses, estimates of the photosynthetic rate at

Alessandro Cescatti; Ülo Niinemets

169

Leaf to Landscape  

Microsoft Academic Search

\\u000a One fundamental “problem” for maximizing carbon gain at the leaf and higher organizational levels entails the link between\\u000a light capture and leaf energy budgets. The balance between the two processes, however, depends on the environment. For example,\\u000a shade environments limit carbon gain due to low light levels, and so we would expect plants to display traits that maximize\\u000a light interception

Stanley D. Smith; Elke Naumburg; ÜLo Niinemets; Matthew J. Germino

170

The effect of pollen on the fungal leaf microflora of Beta vulgaris L. and on infection of leaves by Phoma betae  

Microsoft Academic Search

Studies were made on the leaf-inhabiting fungus flora of two plots of flowering sugarbeet. Flowers were removed from plants of one plot as they appeared. Changes in the numbers of micro-organisms on leaves were recorded by leaf washing and leaf homogenization techniques, and were found to follow closely the changes in numbers of pollen grains seen on cleared leaf discs.

R. C. Warren

1972-01-01

171

Effects of Leaf Age on Oviposition and on Offspring Fitness in the Imported Willow Leaf Beetle Plagiodera versicolora (Coleoptera: Chrysomelidae)  

Microsoft Academic Search

Imported willow leaf beetles Plagiodera versicolora oviposit on willow leaves, and both larvae and adults feed on the leaves. In the field, eggs were found on leaves near the center of branchlets, and the number of eggs per cluster was independent of the leaf area and position. However, in the laboratory, females chose young leaves over old leaves, for both

B. H. King; M. L. Crowe; M. D. Blackmore

1998-01-01

172

Stem Up  

NSDL National Science Digital Library

Stem Up is a pilot program to aid the disadvantaged youth of Boyle Heights in Los Angeles. The intent of the program was to integrate STEM career pathways into schools and local communities. Visitors will find the K-12 Students tab near the top of the page to be filled with almost two dozen links for all levels of student learning about science and technology. Some of the sites include "Arrick Robotics", for 9-12 graders, "Extreme Science", for all ages, and "Fun Engineering" for kids aged 10-14. The "Boyle Heights" link is a great resource for residents of the LA neighborhood, as well as informative for those visitors unfamiliar with it. There is full contact information for the city and state representatives of the neighborhood, the Police Activities League, and a live theatre that performs outreach through theatre, and classical plays. The "Parents" link also provides a number of science and technology links that parents and kids can visit together.

173

Soybean Endo-?-Mannanase GmMAN1 Is Not Associated with Leaf Abscission, but Might Be Involved in the Response to Wounding  

PubMed Central

The objective of this work is to investigate the relationship between endo-?-mannanase and leaf abscission, and response to wounding in soybean (Glycine max). An endo-?-mannanase gene GmMAN1 was cloned from the abscission zone in petiole explants, and was heterologously expressed in E. coli. Polyclonal antibodies were raised against the fusion protein. The increases in activity, isoform numbers, and amounts of transcripts and proteins of GmMAN1 were found not only in the abscission zone but also in the non-abscission zone during petiole abscission in the explants, but not in these two tissues during leaf abscission artificially induced by ethephon treatment in the intact plants. The changes in endo-?-mannanase expression patterns in these two tissues were probably induced by the inherent mechanical wounding during the preparation of explants. When soybean plants were wounded by removing half of the leaf blade of the first pair of true leaves, the transcripts and proteins of GmMAN1 were induced in the leaves and stem, leading to the increases in enzyme activity and isoform numbers in them. It is concluded that the soybean endo-?-mannanase GmMAN1 is not associated with leaf abscission, but might be involved in the response to wounding.

Yan, Min; Zhang, Yifan; Guo, Wenjuan; Wang, Xiaofeng

2012-01-01

174

Deer predation on leaf miners via leaf abscission  

NASA Astrophysics Data System (ADS)

The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

Yamazaki, Kazuo; Sugiura, Shinji

2008-03-01

175

Deer predation on leaf miners via leaf abscission.  

PubMed

The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer (Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission. PMID:18004533

Yamazaki, Kazuo; Sugiura, Shinji

2008-03-01

176

STEM CELLS  

PubMed Central

Two independent studies show that, if push comes to shove, differentiated cells of the stomach and lung can act as adult stem cells generating various cell types of the tissue, including a pool of stem cells.

Desai, Tushar J.; Krasnow, Mark A.

2014-01-01

177

Stem Cell Transplantation Methods  

Microsoft Academic Search

\\u000a \\u000a Just a few short years ago, we still used to think that we were born with a finite number of irreplaceable neurons. However,\\u000a in recent years, there has been increasingly persuasive evidence that suggests that neural stem cell (NSC) maintenance and\\u000a differentiation continue to take place throughout the mammal’s lifetime. Studies suggest that neural stem cells not only persist\\u000a to

Kimberly D. Tran; Allen Ho; Rahul Jandial

178

The occurrence of adverse events during the infusion of autologous peripheral blood stem cells is related to the number of granulocytes in the leukapheresis product.  

PubMed

Toxicity related to autologous PBSC infusion is well known and traditionally attributed to the presence of DMSO as cryoprotectant. But despite DMSO depletion, adverse events continue appearing. We have conducted a retrospective study to determine the incidence of adverse events related to the PBSC infusion in a large series of 144 patients. Adverse effects were observed in 67.36% of patients, although most of them were of grade 1 or 2. The adverse events most frequently reported were allergic reactions, followed by general, gastrointestinal and respiratory symptoms. In the univariate analysis, age (P=0.01), the volume infused (P=0.005), the amount of DMSO (P=0.008), the total nucleated cells (P=0.002), the total number of granulocytes (P=0.000001) and clumping (P=0.000001) were associated with the occurrence of adverse events. In the multivariate analysis, two protective factors, age (P=0.05) and sex (P=0.004), and two risk factors, the number of granulocytes, with a relative risk of 1.18 (95% confidence interval, 1.06-1.31) (P=0.002), and clumping, with an relative risk of 1.94 (95% confidence interval, 1.15-3.29) (P=0.013), were identified. The best cutoff point for the prediction of the occurrence of adverse events, with a sensitivity of 47% and specificity of 89%, was 6.065 x 10(9) granulocytes. PMID:17906706

Cordoba, R; Arrieta, R; Kerguelen, A; Hernandez-Navarro, F

2007-12-01

179

The Drosophila ovary: an active stem cell community  

Microsoft Academic Search

Only a small number of cells in adult tissues (the stem cells) possess the ability to self-renew at every cell division, while producing differentiating daughter cells to maintain tissue homeostasis for an organism's lifetime. The Drosophila ovary harbors three different types of stem cell populations (germline stem cell (GSC), somatic stem cell (SSC) and escort stem cell (ESC)) located in

Dániel Kirilly; Ting Xie

2007-01-01

180

New perspectives in human stem cell therapeutic research  

Microsoft Academic Search

Human stem cells are in evaluation in clinical stem cell trials, primarily as autologous bone marrow studies, autologous and allogenic mesenchymal stem cell trials, and some allogenic neural stem cell transplantation projects. Safety and efficacy are being addressed for a number of disease state applications. There is considerable data supporting safety of bone marrow and mesenchymal stem cell transplants but

Alan Trounson

2009-01-01

181

Glucocorticoids decrease tissue mast cell number by reducing the production of the c-kit ligand, stem cell factor, by resident cells: in vitro and in vivo evidence in murine systems.  

PubMed Central

The local delivery of glucocorticoids to tissues significantly decreases mast cell number. This pharmacologic effect of glucocorticoids is believed to be one of the mechanisms by which glucocorticoids regulate allergic inflammation. To determine the mechanism by which glucocorticoids are able to exert this effect, we first applied the glucocorticoid fluocinonide to mouse dermis and observed that the decrease in mast cell number was associated with an increase in mast cell apoptosis. This did not appear to be due to a direct effect of the glucocorticoid on mast cells, as the addition of 0.01-1.0 microM of the glucocorticoid dexamethasone into stem cell factor (SCF)-dependent mast cell cultures did not enhance mast cell death. However, addition of dexamethasone to cultured fibroblasts did result in a downregulation of SCF mRNA and a significant decrease in SCF protein production. Similarly, immunohistochemistry performed on fluocinonide-treated mouse dermis revealed a decrease in immunoreactive SCF. Administration of SCF at sites of fluocinonide administration to the dermis abolished the mast cell-depleting effect of this glucocorticoid. Thus, glucocorticoids decrease tissue mast cell number by downregulating tissue SCF production required for the survival of local mast cells. This observation may be applicable to the design of improved strategies to treat mast cell-mediated disorders.

Finotto, S; Mekori, Y A; Metcalfe, D D

1997-01-01

182

Multipotent somatic stem cells contribute to the stem cell niche in the Drosophila testis  

Microsoft Academic Search

Adult stem cells reside in specialized microenvironments, or niches, that have an important role in regulating stem cell behaviour. Therefore, tight control of niche number, size and function is necessary to ensure the proper balance between stem cells and progenitor cells available for tissue homeostasis and wound repair. The stem cell niche in the Drosophila male gonad is located at

Justin Voog; Cecilia D'Alterio; D. Leanne Jones

2008-01-01

183

STEM Sell  

ERIC Educational Resources Information Center

Between 1994 and 2003, employment in science, technology, engineering and math (STEM) fields grew by a remarkable 23 percent, compared with 17 percent in non-STEM fields, according to federal data. The Bureau of Labor Statistics predicts continued strong growth in STEM job openings through 2014, with emphasis on life sciences, environmental…

Pantic, Zorica

2007-01-01

184

Relationship between Leaf Water and Leaf Waxes in Growing Pine Needles  

NASA Astrophysics Data System (ADS)

There has been an increasing interest in reconstruction of paleoclimate and paleo-environment using hydrogen isotopic ratios of plant lipids extracted from sediments. It has been shown that ?D of plant lipids is related to the ?D of leaf water, which in turn is related to the ?D of precipitation and relative humidity. However, the ?D of leaf water changes significantly through the life of a leaf, it is not clear how the leaf water dynamics affects the bulk isotopic composition of lipids that are synthesized throughout the life of the leaf. This work is a detailed study of the relationship between ?D values in leaf water and in leaf wax n-acids for two species of pine needles, red pine ( Pinus resinosa) and white pine ( Pinus strobus). In an earlier investigation we found that the ?D of leaf water in pine needles increased as they were elongated through the needle-growing season. The leaf water of red pine needles has higher ?D values than that of white pine needles at each comparable stage of growth. In addition, for a given needle, the leaf water ?D also increased from the base to the tip of the needle. To examine the variation of lipid ?D in relation to that of leaf water ?D, we collected 4 sets of needles during their elongation period, obtained the bulk leaf water, then sectioned them into smaller segments along the length, and measured ?D values of n-acids with 24 to 32 carbons. We test how the measured D/H ratios of leaf waxes vary with time, between two species, and with the position in the needle (relative distance from the tip, 0-1). A multiple regression analysis shows the following results. 1) The ?D values of all types of n-acids are significantly correlated with the position of the sample; ?D is lower near the base and higher near the tip. This result is consistent with the along-needle isotopic distribution of leaf water. 2) Leaf waxes of red pine needles are significantly more enriched in D than white pine needles, also consistent with leaf water ?D variation between the two species. 3) Regardless of temporal increases of leaf water ?D, the ?D of 4 out of 5 wax n-acids shows a decreasing trend with time, although only two (C-24, 32) are statistically significant. This may reflect use of stored hydrogen (from stored carbohydrates) at earlier stages of growth. 4) The significance of the overall regression of ?D against time, species and relative position increases from low carbon to high carbon number lipids (for C-24, 26, 28, 30, and 32, r2=0.34, 0.31, 0.56, 0.61, and 0.83), suggesting that longer wax n-acids are more influenced by local leaf water.

Majumdar, S.; Feng, X.; Hou, J.; Faiia, A. M.; Huang, Y.

2007-12-01

185

Interaction of mineral and cytokinin supply in control of leaf senescence and seed growth in soybean explants  

Microsoft Academic Search

The leaves of intact soybean plants (Glycine max. L. Merrill) characteristically turn yellow and abscise during pod maturation, and this may limit seed growth. We have used soybean expiants (excised 10 cm stem sections with a leaf and midfill pod attached) to study interactive effects of nutrient and hormone supply on leaf senescence symptoms and seed yield. Whereas mineral nutrients

P. M. Neumann; L. D. Nooden

1983-01-01

186

Leaf and Flower Blight Caused by Monilinia vaccinii-corymbosi on Lowbush Blueberry: Effects on Yield and Relationship to Bud Phenology.  

PubMed

ABSTRACT Naturally established lowbush blueberry clones in four fields were evaluated for the incidence of leaf and flower blight, proportion of mummy berries, and yield reductions caused by Monilinia vacciniicorymbosi. The relationship between the phenology of flower and leaf bud development and susceptibility also was examined. Three fields were examined over one crop year and one field was studied in two subsequent crop years. The incidence of stems with blight was correlated to incidence of leaf blight in all fields and to incidence of flower blight in one field. Incidence of leaf and flower blight and the proportion of mummy berries produced were not correlated. Lowbush blueberry clones with higher incidence levels of leaf blight had reduced fruit set and lower berry weights. For healthy stems, leaf-to-fruit ratios had no effect on berry weight in most fields. In contrast, blighted stems with higher leaf-to-fruit ratios had higher berry weights in three fields. Stems with slowerdeveloping leaf and flower buds had less leaf and flower blight, respectively, than stems with faster bud development. Some blueberry clones may avoid infection by delaying production of susceptible tissue until after ascospore release by M. vaccinii-corymbosi. PMID:18943470

Penman, L N; Annis, S L

2005-10-01

187

Shifts in diversity and community structure of endophytic bacteria and archaea across root, stem and leaf tissues in the common reed, Phragmites australis, along a salinity gradient in a marine tidal wetland of northern China.  

PubMed

The effects of salt stress on endophytic prokaryotic communities in plants are largely unknown, and the distribution patterns of bacterial and archaeal endophytes in different tissues of a plant species are rarely compared. We investigated the endophytic bacterial and archaeal communities in roots, stems and leaves of the common reed, Phragmites australis, collected from three tidal zones along a salinity gradient, using terminal restriction fragment (T-RF) length polymorphism analysis of the 16S rRNA genes. The results showed that the bacterial diversity in the roots was significantly higher than that in the leaves, whereas similar archaeal diversity was revealed for either plant tissues or tidal zones. Network analysis revealed that T-RFs were grouped largely by tissue, and the major groups were generally linked by a few common T-RFs. Unique T-RFs in roots were mainly present in plants growing in the supratidal zone, but unique T-RFs in stems and leaves were mainly present in those from the middle and high tidal zones. Non-metric multidimensional scaling ordination and analysis of similarity revealed that bacterial communities were significantly different among tissues (P < 0.05), but similar among tidal zones (P = 0.49). However, the archaeal communities differed among tidal zones (P < 0.05), but were similar among tissues (P = 0.89). This study indicates that: (1) the endophytic archaeal communities are influenced more significantly than the endophytic bacterial communities by soil salinity, and (2) the differential distribution patterns of bacterial and archaeal endophytes in plant tissues along a salinity gradient imply that these two groups play different roles in coastal hydrophytes. PMID:23897211

Ma, Bin; Lv, Xiaofei; Warren, Alan; Gong, Jun

2013-11-01

188

BOREAS TE-9 NSA Leaf Chlorophyll Density  

NASA Technical Reports Server (NTRS)

The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. These data were collected to help provide an explanation of potential seasonal and spatial changes of leaf pigment properties in boreal forest species at the NSA. At different dates (FFC-Winter, FFC-Thaw, IFC-1, IFC-2, and IMC-3), foliage samples were collected from the upper third of the canopy for five NSA sites (YJP, OJP, OBS, UBS, and OA) near Thompson, Manitoba. Subsamples of 100 needles for black spruce, 20 needles for jack pine, and single leaf for trembling aspen were cut into pieces and immersed in a 20-mL DMF aliquot in a Nalgene test tube. The extracted foliage materials were then oven-dried at 68 C for 48 hours and weighed. Extracted leaf dry weight was converted to a total leaf area basis to express the chlorophyll content in mg/sq cm of total leaf area. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Sy, Mikailou

2000-01-01

189

Autophagy in stem cells  

PubMed Central

Autophagy is a highly conserved cellular process by which cytoplasmic components are sequestered in autophagosomes and delivered to lysosomes for degradation. As a major intracellular degradation and recycling pathway, autophagy is crucial for maintaining cellular homeostasis as well as remodeling during normal development, and dysfunctions in autophagy have been associated with a variety of pathologies including cancer, inflammatory bowel disease and neurodegenerative disease. Stem cells are unique in their ability to self-renew and differentiate into various cells in the body, which are important in development, tissue renewal and a range of disease processes. Therefore, it is predicted that autophagy would be crucial for the quality control mechanisms and maintenance of cellular homeostasis in various stem cells given their relatively long life in the organisms. In contrast to the extensive body of knowledge available for somatic cells, the role of autophagy in the maintenance and function of stem cells is only beginning to be revealed as a result of recent studies. Here we provide a comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells. We discuss how recent studies of different knockout mice models have defined the roles of various autophagy genes and related pathways in the regulation of the maintenance, expansion and differentiation of various stem cells. We also highlight the many unanswered questions that will help to drive further research at the intersection of autophagy and stem cell biology in the near future.

Guan, Jun-Lin; Simon, Anna Katharina; Prescott, Mark; Menendez, Javier A.; Liu, Fei; Wang, Fen; Wang, Chenran; Wolvetang, Ernst; Vazquez-Martin, Alejandro; Zhang, Jue

2013-01-01

190

A high proportion of blue light increases the photosynthesis capacity and leaf formation rate of Rosa × hybrida but does not affect time to flower opening.  

PubMed

Alterations in light quality affect plant morphogenesis and photosynthetic responses but the effects vary significantly between species. Roses exhibit an irradiance-dependent flowering control but knowledge on light quality responses is scarce. In this study we analyzed, the responses in morphology, photosynthesis and flowering of Rosa × hybrida to different blue (B) light proportions provided by light-emitting diodes (LED, high B 20%) and high pressure sodium (HPS, low B 5%) lamps. There was a strong morphological and growth effect of the light sources but no significant difference in total dry matter production and flowering. HPS-grown plants had significantly higher leaf area and plant height, yet a higher dry weight proportion was allocated to leaves than stems under LED. LED plants showed 20% higher photosynthetic capacity (Amax ) and higher levels of soluble carbohydrates. The increase in Amax correlated with an increase in leaf mass per unit leaf area, higher stomata conductance and CO2 exchange, total chlorophyll (Chl) content per area and Chl a/b ratio. LED-grown leaves also displayed a more sun-type leaf anatomy with more and longer palisade cells and a higher stomata frequency. Although floral initiation occurred at a higher leaf number in LED, the time to open flowers was the same under both light conditions. Thereby the study shows that a higher portion of B light is efficient in increasing photosynthesis performance per unit leaf area, enhancing growth and morphological changes in roses but does not affect the total Dry Matter (DM) production or time to open flower. PMID:23020549

Terfa, Meseret Tesema; Solhaug, Knut Asbjørn; Gislerød, Hans Ragnar; Olsen, Jorunn Elisabeth; Torre, Sissel

2013-05-01

191

Maple Leaf Outdoor Centre.  

ERIC Educational Resources Information Center

Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…

Maguire, Molly; Gunton, Ric

2000-01-01

192

Role of mesenchymal stem cells in hematopoietic stem cell transplantation.  

PubMed

Within the bone marrow stroma are multipotential cells which are capable of differentiation into a number of mesenchymal cell lineages. These cells, termed mesenchymal stem cells, have recently been identified and characterized in humans. Many studies indicate that the bone marrow stroma is damaged following bone marrow transplantation. Since the marrow stroma is critical for the maintenance of hematopoiesis, its ability to support hematopoiesis following stem cell transplantation may be impaired. Animal models suggest that the transplantation of healthy stromal elements, including mesenchymal stem cells, may enhance the ability of the bone marrow microenvironment to support hematopoiesis after stem cell transplantation. Here the authors review recent data that suggest that mesenchymal stem cells may possess therapeutic value not only for the repair of damaged mesenchymal tissues following hematopoietic stem cell transplantation, but also as potential vectors for the delivery of corrective genes. PMID:11055509

Devine, S M; Hoffman, R

2000-11-01

193

Validation of chimerism in pediatric recipients of allogeneic hematopoietic stem cell transplantation (HSCT) a comparison between two methods: real-time PCR (qPCR) vs. variable number tandem repeats PCR (VNTR PCR).  

PubMed

Post-hematopoietic stem cell transplantation (HSCT) chimerism monitoring is important to assess relapse and therapeutic intervention. The purpose of our study is to compare two methods variable number tandem repeats (VNTR) vs. quantitative real- time polymerase chain reaction (qPCR) in terms of determining chimerism. 127 (peripheral blood n=112, bone marrow n=15) samples were simultaneously tested by VNTR using APO-B, D1S80, D1S111, D17S30, gene loci SRY and ZP3 and qPCR using 34 assays (CA001-CA034) that are designed to a bi-allelic insertion/deletion (indel) polymorphism in the human genome. Samples were separated in three subsets: total WBC, T-cell and Myeloid cells. Extraction of DNA was performed then quantified. We analyzed column statistics, paired t-test and regression analysis for both methods. There was complete correlation between the two methods. The simplicity and rapidity of the test results from the qPCR method is more efficient and accurate to assess chimerism. PMID:23238335

Kletzel, Morris; Huang, Wei; Olszewski, Marie; Khan, Sana

2013-01-01

194

The triple isotopic composition of oxygen in leaf water  

NASA Astrophysics Data System (ADS)

The isotopic composition of atmospheric O 2 depends on the rates of oxygen cycling in photosynthesis, respiration, photochemical reactions in the stratosphere and on ?17O and ?18O of ocean and leaf water. While most of the factors affecting ?17O and ?18O of air O 2 have been studied extensively in recent years, ?17O of leaf water—the substrate for all terrestrial photosynthesis—remained unknown. In order to understand the isotopic composition of atmospheric O 2 at present and in fossil air in ice cores, we studied leaf water in field experiments in Israel and in a European survey. We measured the difference in ?17O and ?18O between stem and leaf water, which is the result of isotope enrichment during transpiration. We calculated the slopes of the lines linking the isotopic compositions of stem and leaf water. The obtained slopes in ln( ?17O + 1) vs. ln( ?18O + 1) plots are characterized by very high precision (˜0.001) despite of relatively large differences between duplicates in both ?17O and ?18O (0.02-0.05‰). This is so because the errors in ?18O and ?17O are mass-dependent. The slope of the leaf transpiration process varied between 0.5111 ± 0.0013 and 0.5204 ± 0.0005, which is considerably smaller than the slope linking liquid water and vapor at equilibrium (0.529). We further found that the slope of the transpiration process decreases with atmospheric relative humidity ( h) as 0.522-0.008 × h, for h in the range 0.3-1. This slope is neither influenced by the plant species, nor by the environmental conditions where plants grow nor does it show strong variations along long leaves.

Landais, A.; Barkan, E.; Yakir, D.; Luz, B.

2006-08-01

195

Stem Cells, Phenotypic Inversion, and Differentiation  

PubMed Central

Stem cells possess the potential to cure a myriad of ailments ranging from congenital diseases to illnesses acquired through the physiological process of aging. In the adult, these cells are extremely rare and often difficult to isolate in numbers sufficient to apply to medical treatment. Ex vivo expansion of these cells will be required for most meaningful interventions. The discovery of stem/progenitor cell inversion offers a new avenue for obtaining sufficient numbers of stem cells. Adult progenitor cells are much more common than quiescent stem cells and can be isolated with minimal interventions; therefore, inversion of progenitors to stem cells may become a feasible approach for therapeutic purposes. Stem cells are known to possess few mitochondria, and mitochondrial biogenesis is required for stem cell differentiation. The microtubule cytoskeleton is a major regulator for mitochondrial biogenesis. Investigations in the area of controlling cell differentiation and inducing phenotypic inversion, possibly through manipulation of mitochondrial biogenesis, may contribute to stem cell-based therapies.

Siggins, Robert W.; Zhang, Ping; Welsh, David; LeCapitaine, Nicole J.; Nelson, Steve

2008-01-01

196

Hydraulic differences along the water transport system of South American Nothofagus species: do leaves protect the stem functionality?  

PubMed

Hydraulic traits were studied for six Nothofagus species from South America (Argentina and Chile), and for three of these species two populations were studied. The main goal was to determine if properties of the water conductive pathway in stems and leaves are functionally coordinated and to assess if leaves are more vulnerable to cavitation than stems, consistent with the theory of hydraulic segmentation along the vascular system of trees in ecosystems subject to seasonal drought. Vulnerability to cavitation, hydraulic conductivity of stems and leaves, leaf water potential, wood density and leaf water relations were examined. Large variations in vulnerability to cavitation of stems and leaves were observed across populations and species, but leaves were consistently more vulnerable than stems. Water potential at 50% loss of maximum hydraulic efficiency (P(50)) ranged from -0.94 to -2.44 MPa in leaves and from -2.6 to -5.3 MPa in stems across species and populations. Populations in the driest sites had sapwood and leaves more vulnerable to cavitation than those grown in the wettest sites. Stronger diurnal down-regulation in leaf hydraulic conductance compared with stem hydraulic conductivity apparently has the function to slow down potential water loss in stems and protect stem hydraulics from cavitation. Species-specific differences in wood density and leaf hydraulic conductance (K(Leaf)) were observed. Both traits were functionally related: species with higher wood density had lower K(Leaf). Other stem and leaf hydraulic traits were functionally coordinated, resulting in Nothofagus species with an efficient delivery of water to the leaves. The integrity of the more expensive woody portion of the water transport pathway can thus be maintained at the expense of the replaceable portion (leaves) of the stem-leaf continuum under prolonged drought. Compensatory adjustments between hydraulic traits may help to decrease the rate of embolism formation in the trees more vulnerable to cavitation. PMID:22684354

Bucci, Sandra J; Scholz, Fabian G; Campanello, Paula I; Montti, Lia; Jimenez-Castillo, Mylthon; Rockwell, Fulton A; Manna, Ludmila La; Guerra, Pedro; Bernal, Pablo Lopez; Troncoso, Oscar; Enricci, Juan; Holbrook, Michele N; Goldstein, Guillermo

2012-07-01

197

Physics strategies for sparing neural stem cells during whole-brain radiation treatments  

SciTech Connect

Purpose: Currently, there are no successful long-term treatments or preventive strategies for radiation-induced cognitive impairments, and only a few possibilities have been suggested. One such approach involves reducing the dose to neural stem cell compartments (within and outside of the hippocampus) during whole-brain radiation treatments for brain metastases. This study investigates the fundamental physics issues associated with the sparing of neural stem cells during photon radiotherapy for brain metastases. Methods: Several factors influence the stem cell dose: intracranial scattering, collimator leakage, beam energy, and total number of beams. The relative importance of these factors is investigated through a set of radiation therapy plans, which are all variations of an initial 6 MV intensity-modulated radiation therapy (IMRT) plan designed to simultaneously deliver a whole-brain dose of 30 Gy and maximally reduce stem cell compartment dose. Additionally, an in-house leaf segmentation algorithm was developed that utilizes jaw motion to minimize the collimator leakage. Results: The plans are all normalized such that 50% of the PTV receives 30 Gy. For the initial 6 MV IMRT plan, 50% of the stem cells receive a dose greater than 6.3 Gy. Calculations indicate that 3.6 Gy of this dose originates from intracranial scattering. The jaw-tracking segmentation algorithm, used in conjunction with direct machine parameter optimization, reduces the 50% stem cell dose to 4.3 and 3.7 Gy for 6 and 10 MV treatment beams, respectively. Conclusions: Intracranial scattering alone is responsible for a large dose contribution to the stem cell compartment. It is, therefore, important to minimize other contributing factors, particularly the collimator leakage, to maximally reduce dose to these critical structures. The use of collimator jaw tracking in conjunction with modern collimators can minimize this leakage.

Kirby, Neil; Chuang, Cynthia; Pouliot, Jean; Hwang, Andrew; Barani, Igor J. [Department of Radiation Oncology, University of California San Francisco, San Francisco, California 94143-1708 (United States)

2011-10-15

198

STEM At Work  

NSDL National Science Digital Library

STEM (Science Technology Engineering & Math) at work, presented by the Florida Advanced Technological Education Center, includes a number of educational puzzles for use in the classroom. Puzzles include an energy audit exercise, measurement of air bag movement, and diesel fuel additive volatility.

2011-03-17

199

Leaf lifetime photosynthetic rate and leaf demography in whole plants of Ipomoea pes-caprae growing with a low supply of calcium, a 'non-mobile' nutrient  

PubMed Central

The adaptive significance of leaf longevity has been established in relation to restrictive nutrients that can be retranslocated within the plant. However, the effect of deficiencies in ‘non-mobile’ nutrients on leaf lifespan and photosynthetic carbon gain is uncertain. Calcium is frequently given as an example of an essential nutrient with low phloem mobility that may alter the leaf senescence process. This study has been designed to estimate leaf lifespan, leaf production (Lp) and leaf death (Ld) rates, the age structure of leaves, and the decline in maximum photosynthetic rate (Amax) with age in plants of Ipomoea pes-caprae growing with a full supply of nutrients and with a low Ca supply. The Ca deficiency produced reductions in Lp and leaf lifespan compared with control plants. In spite of the differences in the demographic parameters between treatments in control and low-Ca plants, the percentage of leaves of a given leaf age class is maintained in such a way that the number of leaves per plant continues to increase. No relationship was found between Ca supply and Amax. However, the decline in Amax with leaf senescence was rather sudden in control plants compared with plants growing with a low Ca supply. The importance of simultaneously using the total leaf demographic census and the assimilation rate along with leaf lifespan data in order to understand the performance of whole plants under constrained conditions is discussed.

Suarez, N.

2010-01-01

200

Leaf lifetime photosynthetic rate and leaf demography in whole plants of Ipomoea pes-caprae growing with a low supply of calcium, a 'non-mobile' nutrient.  

PubMed

The adaptive significance of leaf longevity has been established in relation to restrictive nutrients that can be retranslocated within the plant. However, the effect of deficiencies in 'non-mobile' nutrients on leaf lifespan and photosynthetic carbon gain is uncertain. Calcium is frequently given as an example of an essential nutrient with low phloem mobility that may alter the leaf senescence process. This study has been designed to estimate leaf lifespan, leaf production (L(p)) and leaf death (L(d)) rates, the age structure of leaves, and the decline in maximum photosynthetic rate (A(max)) with age in plants of Ipomoea pes-caprae growing with a full supply of nutrients and with a low Ca supply. The Ca deficiency produced reductions in L(p) and leaf lifespan compared with control plants. In spite of the differences in the demographic parameters between treatments in control and low-Ca plants, the percentage of leaves of a given leaf age class is maintained in such a way that the number of leaves per plant continues to increase. No relationship was found between Ca supply and A(max). However, the decline in A(max) with leaf senescence was rather sudden in control plants compared with plants growing with a low Ca supply. The importance of simultaneously using the total leaf demographic census and the assimilation rate along with leaf lifespan data in order to understand the performance of whole plants under constrained conditions is discussed. PMID:20080828

Suárez, N

2010-03-01

201

Barley leaf stripe disease.  

PubMed

Leaf stripe is one of the most important diseases of barley in Iran especially in Gorgan, Mazandran and near Tehran (Varamin). Most obvious symptoms of the disease are described. Long pale or yellow stripes become darker as the fungus sporulates on the leaf surface. Infected plants usually are stunted and produce sterile spikes, rarely a few seeds are produced. Infected spikes and late-forming tillers may produce fertile spikes. The fungus is seed brone and survives in the outer layers of infected seed. To study the seed-borne disease, we have used the different methods (ISTA). Coleoptiles of seedlings are infected by the fungus under cool, moist conditions, a soil temperature below 15 degrees C is necessary for seed infection. The fungus penetrates through coleoptiles and grows systemically within the plant, produces toxin and kills cells and discolors leaf tissue between veins, thus causing striped lesions. When conditions are wet or humid, spores are produced on the surface of leaves at above the time spikes of healthy plant. Morphological characteristics of the vegetative and reproductive structures of the fungus show that it is Drechslera graminea (Rabenh) Shoemaker. PMID:12701433

Zad, J; Aghakhani, M; Etebarian, R; Okhovat, M

2002-01-01

202

Tomato stem trichomes and dispersal success of Phytoseiulus persimilis relative to its prey Tetranychus urticae  

Microsoft Academic Search

Tomato varieties used at present for commercial production in Dutch glasshouses have a high density of glandular trichomes on the stem, but a very low density on the leaves. The two-spotted spider mite,Tetranychus urticae Koch, and the predatory mite,Phytoseiulus persimilis Athias-Henriot, usually disperse from leaf to leaf via the stem, thereby incurring high risks of entrapment (and death) in the

R. J. F. Van Haren; M. M. Steenhuis; M. W. Sabelis; O. M. B. De Ponti

1987-01-01

203

The effect of chrysanthemum leaf trichome density and prey spatial distribution on predation of Tetranychus urticae (Acari: Tetranychidae) by Phytoseiulus persimilis (Acari: Phytoseiidae).  

PubMed

The effect of plant architecture, in terms of leaf hairiness, and prey spatial arrangement, on predation rate of eggs of the spider mite, Tetranychus urticae Koch, by the predatory mite Phytoseiulus persimilis Athias-Henriot was examined on cut stems of chrysanthemums. Three levels of leaf hairiness (trichome density) were obtained using two different chrysanthemum cultivars and two ages within one of the cultivars. The number of prey consumed by P. persimilis was inversely related to trichome density. At low prey densities (less than ten eggs per stem), prey consumption did not differ in a biologically meaningful way between treatments. The effect of prey spatial arrangement on the predation rate of P. persimilis was also examined. Predation rates were higher in prey patches on leaves adjacent to the release point of P. persimilis, but significantly greater numbers of prey were consumed in higher density prey patches compared to low density patches. The predators exhibited non-random searching behaviour, spending more time on leaves closest to the release point. The implications of these findings for biological control and predator-prey dynamics are discussed. PMID:12908920

Skirvin, D J; Stavrinides, M C; Skirvin, D J

2003-08-01

204

Patterns of hydraulic architecture and water relations of two tropical canopy trees with contrasting leaf phenologies: Ochroma pyramidale and Pseudobombax septenatum.  

PubMed

Many authors have attempted to explain the adaptive response of tropical plants to drought based on studies of water relations at the leaf level. Little attention has been given to the role of the xylem system in the control of plant water requirements. To evaluate this role, we studied the hydraulic architecture and water relations parameters of two tropical canopy trees with contrasting leaf phenologies: deciduous Pseudobombax septenatum (Jacq.) Dug and evergreen Ochroma pyramidale (Cav. ex lamb) Urban, both in the family Bombacaceae. The hydraulic architecture parameters studied include hydraulic conductivity, specific conductivity, leaf specific conductivity, and Huber value. Water relations parameters include leaf water potential, stem and leaf water storage capacitance, transpiration, stomatal conductance, and vulnerability of stems to cavitation and loss of hydraulic conductivity by embolisms. Compared to temperate trees, both species showed a pattern of highly vulnerable stems (50% loss of conductivity due to embolism at water potentials less than 1 MPa) with high leaf specific conductivities. The vulnerability of xylem to water-stress-induced embolism was remarkably similar for the two species but the leaf specific conductivity of petioles and leaf-bearing stems of the evergreen species, Ochroma (e.g., 9.08 and 11.4 x 10(-4) kg s(-1) m(-1) MPa(-1), respectively), were 3.4 and 2.3 times higher, respectively, than those of the deciduous species, Pseudobombax (e.g., 2.64 and 5.15 x 10(-4) kg s(-1) m(-1) MPa(-1), respectively). A runaway embolism model was used to test the ability of Ochroma and Pseudobombax stems to maintain elevated transpiration rates during the higher evaporative demand of the dry season. The percent loss of leaf area predicted by the runaway embolism model for stems of Pseudobombax ranged from 5 to 30%, not enough to explain the deciduous phenology of this tree species without analysis of root resistance or leaf and petiole vulnerability to embolism. PMID:14967698

Machado, J L; Tyree, M T

1994-03-01

205

Scaling relationships among twig size, leaf size and leafing intensity in a successional series of subtropical forests.  

PubMed

Scaling relationships among twig size, leaf size and leafing intensity fundamentally influence the twig-leaf deployment pattern, a property that affects the architecture and functioning of plants. However, our understanding of how these relationships change within a species or between species as a function of forest succession is unclear. We determined log-log scaling relationships between twig cross-sectional area (twig size) and each of total and individual leaf area, and leafing intensity (the number of leaves per twig volume) for 78 woody species along a successional series in subtropical evergreen forests in eastern China. The series included four stages: secondary shrub (S1), young (S2), sub-climax (S3) and climax evergreen broadleaved forests (S4). The scaling slopes in each of the three relationships did not differ among the four stages. The y-intercept did not shift among the successional stages in the relationship between twig cross-sectional area and total leaf area; however, the y-intercept was greatest in S4, intermediate in S3 and lowest in S2 and S1 for the relationship between twig size and individual leaf area, while the opposite pattern was found for the twig size-leafing intensity relationship. This indicates that late successional trees have few but large leaves while early successional trees have more small leaves per unit twig size. For the relationship between twig cross-sectional area and total leaf area, there was no difference in the regression slope between recurrent (appear in more than one stages) and non-recurrent species (appear in only one stage) for each of the S1-S2, S2-S3 and S3-S4 pairs. A significant difference in the y-intercept was found in the S2-S3 pair only. In the relationship between twig cross-sectional area and individual leaf area, the regression slope between recurrent and non-recurrent species was homogeneous in the S1-S2 and S3-S4 pairs, but heterogeneous in the S2-S3 pair. We conclude that forest succession caused the shift in the intercept, but did not affect scaling slopes for relationships among twig size, leaf size and leaf intensity. For recurrent species, the invariant scaling slope in the twig-leaf size relationship between adjacent pairs of successional stages may be related to their phenotypic plasticity by adjusting their twig and leaf deployment strategy to similar to what the non-recurrent species display. PMID:23824241

Yan, En-Rong; Wang, Xi-Hua; Chang, Scott X; He, Fangliang

2013-06-01

206

The stem xylem of Patagonian shrubs operates far from the point of catastrophic dysfunction and is additionally protected from drought-induced embolism by leaves and roots.  

PubMed

Hydraulic architecture was studied in shrub species differing in rooting depth in a cold desert in Southern Argentina. All species exhibited strong hydraulic segmentation between leaves, stems and roots with leaves being the most vulnerable part of the hydraulic pathway. Two types of safety margins describing the degree of conservation of the hydraulic integrity were used: the difference between minimum stem or leaf water potential (?) and the ? at which stem or leaf hydraulic function was reduced by 50% (? - ?50), and the difference between leaf and stem ?50. Leaf ?50 - stem ?50 increased with decreasing rooting depth. Large diurnal decreases in root-specific hydraulic conductivity suggested high root vulnerability to embolism across all species. Although stem ?50 became more negative with decreasing species-specific ?soil and minimum stem ?, leaf ?50 was independent of ? and minimum leaf ?. Species with embolism-resistant stems also had higher maximum stem hydraulic conductivity. Safety margins for stems were >2.1 MPa, whereas those for leaves were negative or only slightly positive. Leaves acted as safety valves to protect the integrity of the upstream hydraulic pathway, whereas embolism in lateral roots may help to decouple portions of the plant from the impact of drier soil layers. PMID:23639077

Bucci, Sandra J; Scholz, Fabian G; Peschiutta, Maria Laura; Arias, Nadia S; Meinzer, Frederick C; Goldstein, Guillermo

2013-12-01

207

Comparative Leaf Epidermal Anatomy of Mutants of Barley ( Hordeum vulgare L. ‘Himalaya’) which Differ in Leaf Length  

Microsoft Academic Search

We wished to determine the nature of differences in epidermal cell numbers and dimensions between leaves of different length in mutants of barley (Hordeum vulgareL. ‘Himalaya’). Three comparisons were made: leaf one (L1)vs.leaf four (L4); wild typevs.nine dwarf mutants and wild typevs.a slender mutant. L1 was shorter than L4, and for most lines this was associated with a change in

C. L. WENZEL; P. M. CHANDLER; R. B. CUNNINGHAM; J. B. PASSIOURA

1997-01-01

208

Developing STEM Leaders  

NASA Astrophysics Data System (ADS)

This poster highlights the Capitol College Center for Space Science Education and Public Outreach program to developing future leaders in the science, technology, engineering and math (STEM) fields. The STEM Leaders Program directly works to strengthen the nation's future workforce. Working in partnership with two area community colleges, the goal for the program is to increase the number of individuals who receive a bachelor's degree, advance to the graduate level, and are prepared to enter the workforce as leaders in a STEM discipline. This poster session provides a summary of the 2011 spring workshops, highlights speakers from NASA Goddard Space Flight Center and Lockheed Martin, and shares initial results from the spring 2011 program.

Gibbs, M. G.

2011-12-01

209

The effect of chrysanthemum leaf trichome density and prey spatial distribution on predation of Tetranychus urticae (Acari: Tetranychidae) by Phytoseiulus persimilis (Acari: Phytoseiidae)  

Microsoft Academic Search

The effect of plant architecture, in terms of leaf hairiness, and prey spatial arrangement, on predation rate of eggs of the spider mite, Tetranychus urticae Koch, by the predatory mite Phytoseiulus persimilis Athias-Henriot was examined on cut stems of chrysanthemums. Three levels of leaf hairiness (trichome density) were obtained using two different chrysanthemum cultivars and two ages within one of

M. C. Stavrinides; D. J. Skirvin

2003-01-01

210

Chemical approaches to studying stem cell biology  

PubMed Central

Stem cells, including both pluripotent stem cells and multipotent somatic stem cells, hold great potential for interrogating the mechanisms of tissue development, homeostasis and pathology, and for treating numerous devastating diseases. Establishment of in vitro platforms to faithfully maintain and precisely manipulate stem cell fates is essential to understand the basic mechanisms of stem cell biology, and to translate stem cells into regenerative medicine. Chemical approaches have recently provided a number of small molecules that can be used to control cell self-renewal, lineage differentiation, reprogramming and regeneration. These chemical modulators have been proven to be versatile tools for probing stem cell biology and manipulating cell fates toward desired outcomes. Ultimately, this strategy is promising to be a new frontier for drug development aimed at endogenous stem cell modulation.

Li, Wenlin; Jiang, Kai; Wei, Wanguo; Shi, Yan; Ding, Sheng

2013-01-01

211

Cellulose Synthase-Like D1 Is Integral to Normal Cell Division, Expansion, and Leaf Development in Maize1[W][OA  

PubMed Central

The Cellulose Synthase-Like D (CslD) genes have important, although still poorly defined, roles in cell wall formation. Here, we show an unexpected involvement of CslD1 from maize (Zea mays) in cell division. Both division and expansion were altered in the narrow-organ and warty phenotypes of the csld1 mutants. Leaf width was reduced by 35%, due mainly to a 47% drop in the number of cell files across the blade. Width of other organs was also proportionally reduced. In leaf epidermis, the deficiency in lateral divisions was only partially compensated by a modest, uniform increase in cell width. Localized clusters of misdivided epidermal cells also led to the formation of warty lesions, with cell clusters bulging from the epidermal layer, and some cells expanding to volumes 75-fold greater than normal. The decreased cell divisions and localized epidermal expansions were not associated with detectable changes in the cell wall composition of csld1 leaf blades or epidermal peels, yet a greater abundance of thin, dense walls was indicated by high-resolution x-ray tomography of stems. Cell-level defects leading to wart formation were traced to sites of active cell division and expansion at the bases of leaf blades, where cytokinesis and cross-wall formation were disrupted. Flow cytometry confirmed a greater frequency of polyploid cells in basal zones of leaf blades, consistent with the disruption of cytokinesis and/or the cell cycle in csld1 mutants. Collectively, these data indicate a previously unrecognized role for CSLD activity in plant cell division, especially during early phases of cross-wall formation.

Hunter, Charles T.; Kirienko, Daniel Hill; Sylvester, Anne W.; Peter, Gary F.; McCarty, Donald R.; Koch, Karen E.

2012-01-01

212

BOREAS TE-5 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. The leaf photosynthetic gas exchange data were collected in the BOREAS NSA and the SSA from 06-Jun- 1994 to 13-Sep- 1994 using a LI-COR 6200 portable photosynthesis system. The data were collected to compare the photosynthetic capacity, stomata] conductance, and leaf intercellular CO, concentrations among the major tree species at the BOREAS sites. The data are average values from diurnal measurements on the upper canopy foliage (sun leaves). The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

213

BOREAS TE-5 Leaf Carbon Isotope Data  

NASA Technical Reports Server (NTRS)

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This documentation describes leaf carbon isotope data that were collected in 1993 and 1994 at the NSA and SSA OJP sites, the SSA OBS site, and the NSA UBS site. In addition, leaf carbon isotope data were collected in 1994 only at the NSA and SSA OA sites. These data was collected to provide seasonal integrated physiological information for 10 to 15 common species at these 6 BOREAS sites. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

214

The role of gravity in leaf blade curvatures  

NASA Technical Reports Server (NTRS)

In the past year we have gained useful information on several aspects of leaf blade growth. The most important observations are as follows: The C(14)-1AA moves preferentially in a gravipositive dorsiventral direction through the blade. This movement is inhibited by inversion of the blade. The responding cells in leaf blade hyponasty are in the lower epidermis and bundle sheath cells. Two additional responses in the leaf were characterized. In addition to blade curvature, the leaf shows petiole curvature and changes in the liminal angle subtended by the pulvinus. Ethylene production was studied under a number of conditions. The blade, rather than the petiole or pulvinus, is the principal site of auxin-promoted ethylene synthesis. The effects of a variety of agents on the blade, including gibberellic acid, abscisic acid, vanadate, low pH buffers, and blue light were reviewed.

Hayes, A. B.

1984-01-01

215

Stem cell maintenance in a different niche  

PubMed Central

To overcome the difficulty of controlling stem cell fate and function in applications to regenerative medicine, a number of alternative approaches have been made. Recent reports demonstrate that a non-cellular niche modulating the biophysical microenvironment with chemical factors can support stem cell self-renewal. In our previous studies, early establishment was executed to optimize biophysical factors and it was subsequently found that the microgeometry of the extracellular matrix made huge differences in stem cell behavior and phenotype. We review here a three-dimensional, non-cellular niche designed to support stem cell self-renewal. The characteristics of stem cells under the designed system are further discussed.

Ahn, Ji Yeon; Lee, Seung Tae

2013-01-01

216

Leaf Area and Above and Belowground Growth Responses of Loblolly Pine to Nutrient and Water Additions  

Microsoft Academic Search

A 2 x 2 nutrient and water factorial experiment with four replications was installed in an 8-yr-old stand of Ioblolly pine (Pinus taeda L.) growing on an infertile, excessively drained sandy site in Scotland County, North Carolina. After the fourth year of treatment, estimated stem volume increment, total biomass production, and peak leaf area index (LAI) increased 152%, 99%, and

Timothy J. Albaugh; H. Lee Allen; Phillip M. Dougherty; Lance W. Kress; John S. King

1998-01-01

217

Stem Cell Basics  

MedlinePLUS

... cells? What are embryonic stem cells? What are adult stem cells? What are the similarities and differences between embryonic and adult stem cells? What are induced pluripotent stem cells? What are ...

218

Number Track  

NSDL National Science Digital Library

Students can use this interactive Flash applet to practice ordering whole numbers within 20. The applet displays a track and number tiles, which the user drags to create the correct sequence of numbers 1 through 20. Users may choose from four levels: place 5 missing numbers, place 10 numbers, arrange all 20 numbers, or create your own challenge.

Bunker, Dan

2010-01-01

219

Genetic dissection of leaf development in Brassica rapa using a genetical genomics approach.  

PubMed

The paleohexaploid crop Brassica rapa harbors an enormous reservoir of morphological variation, encompassing leafy vegetables, vegetable and fodder turnips (Brassica rapa, ssp. campestris), and oil crops, with different crops having very different leaf morphologies. In the triplicated B. rapa genome, many genes have multiple paralogs that may be regulated differentially and contribute to phenotypic variation. Using a genetical genomics approach, phenotypic data from a segregating doubled haploid population derived from a cross between cultivar Yellow sarson (oil type) and cultivar Pak choi (vegetable type) were used to identify loci controlling leaf development. Twenty-five colocalized phenotypic quantitative trait loci (QTLs) contributing to natural variation for leaf morphological traits, leaf number, plant architecture, and flowering time were identified. Genetic analysis showed that four colocalized phenotypic QTLs colocalized with flowering time and leaf trait candidate genes, with their cis-expression QTLs and cis- or trans-expression QTLs for homologs of genes playing a role in leaf development in Arabidopsis (Arabidopsis thaliana). The leaf gene Brassica rapa KIP-related protein2_A03 colocalized with QTLs for leaf shape and plant height; Brassica rapa Erecta_A09 colocalized with QTLs for leaf color and leaf shape; Brassica rapa Longifolia1_A10 colocalized with QTLs for leaf size, leaf color, plant branching, and flowering time; while the major flowering time gene, Brassica rapa flowering locus C_A02, colocalized with QTLs explaining variation in flowering time, plant architectural traits, and leaf size. Colocalization of these QTLs points to pleiotropic regulation of leaf development and plant architectural traits in B. rapa. PMID:24394778

Xiao, Dong; Wang, Huange; Basnet, Ram Kumar; Zhao, Jianjun; Lin, Ke; Hou, Xilin; Bonnema, Guusje

2014-03-01

220

Final report on the safety assessment of AloeAndongensis Extract, Aloe Andongensis Leaf Juice,aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice,aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract.  

PubMed

Plant materials derived from the Aloe plant are used as cosmetic ingredients, including Aloe Andongensis Extract, Aloe Andongensis Leaf Juice, Aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice, Aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract. These ingredients function primarily as skin-conditioning agents and are included in cosmetics only at low concentrations. The Aloe leaf consists of the pericyclic cells, found just below the plant's skin, and the inner central area of the leaf, i.e., the gel, which is used for cosmetic products. The pericyclic cells produce a bitter, yellow latex containing a number of anthraquinones, phototoxic compounds that are also gastrointestinal irritants responsible for cathartic effects. The gel contains polysaccharides, which can be acetylated, partially acetylated, or not acetylated. An industry established limit for anthraquinones in aloe-derived material for nonmedicinal use is 50 ppm or lower. Aloe-derived ingredients are used in a wide variety of cosmetic product types at concentrations of raw material that are 0.1% or less, although can be as high as 20%. The concentration of Aloe in the raw material also may vary from 100% to a low of 0.0005%. Oral administration of various anthraquinone components results in a rise in their blood concentrations, wide systemic distribution, accumulation in the liver and kidneys, and excretion in urine and feces; polysaccharide components are distributed systemically and metabolized into smaller molecules. aloe-derived material has fungicidal, antimicrobial, and antiviral activities, and has been effective in wound healing and infection treatment in animals. Aloe barbadensis (also known as Aloe vera)-derived ingredients were not toxic in acute oral studies using mice and rats. In parenteral studies, the LD(50) using mice was > 200 mg/kg, rats was > 50 mg/kg, and using dogs was > 50 mg/kg. In intravenous studies the LD(50) using mice was > 80 mg/kg, rats was > 15 mg/kg, and dogs was > 10 mg/kg. The 14-day no observed effect level (NOEL) for the Aloe polysaccharide, acemannan, in the diet of Sprague-Dawley rats, was 50,000 ppm or 4.1 to 4.6 g/kg day(-1). In a 3-month study using mice, Aloe vera (extracted in ethanol) given orally in drinking water at 100 mg/kg produced reproductive toxicity, inflammation, and mortality above that seen in control animals. Aloe vera extracted in methanol and given to mice at 100 mg/kg in drinking water for 3 months caused significant sperm damage compared to controls. Aloe barbadensis extracted with water and given to pregnant Charles Foster albino rats on gestational days (GDs) 0 through 9 was an abortifacient and produced skeletal abnormalities. Both negative and positive results were found in bacterial and mammalian cell genotoxicity assays using Aloe barbadensis-derived material, Aloe Ferox-derived material, and various anthraquinones derived from Aloe. Aloin (an anthraquinone) did not produce tumors when included in the feed of mice for 20 weeks, nor did aloin increase the incidence of colorectal tumors induced with 1,2-dimethylhydrazine. Aloe-emodin (an anthraquinone) given to mice in which tumor cells had been injected inhibited growth of malignant tumors. Other animal data also suggest that components of Aloe inhibit tumor growth and improve survival. Various in vitro assays also demonstrated anticarcinogenic activity of aloe-emodin. Diarrhea was the only adverse effect of note with the use of Aloe-derived ingredients to treat asthma, ischemic heart disease, diabetes, ulcers, skin disease, and cancer. Case reports include acute eczema, contact urticaria, and dermatitis in individuals who applied Aloe-derived ingredients topically. The Cosmetic Ingredient Review Expert Panel concluded that anthraquinone levels in the several Aloe Barbaden

2007-01-01

221

Testicular germline stem cells  

Microsoft Academic Search

Stem cells have the ability to both differentiate into other mature cell types and maintain an undifferentiated state by self-renewal. These unique properties form the basis for stem cell use in organ replacement and tissue regeneration in clinical medicine. Currently, embryonic stem cells are the best-studied stem cell type. However alternative stem cells such as induced pluripotent stem cells and

Kehkooi Kee; Renee A. Reijo Pera; Paul J. Turek

2010-01-01

222

Analysis of Gene Expression Profiles in Leaf Tissues of Cultivated Peanuts and Development of EST-SSR Markers and Gene Discovery  

PubMed Central

Peanut is vulnerable to a range of foliar diseases such as spotted wilt caused by Tomato spotted wilt virus (TSWV), early (Cercospora arachidicola) and late (Cercosporidium personatum) leaf spots, southern stem rot (Sclerotium rolfsii), and sclerotinia blight (Sclerotinia minor). In this study, we report the generation of 17,376 peanut expressed sequence tags (ESTs) from leaf tissues of a peanut cultivar (Tifrunner, resistant to TSWV and leaf spots) and a breeding line (GT-C20, susceptible to TSWV and leaf spots). After trimming vector and discarding low quality sequences, a total of 14,432 high-quality ESTs were selected for further analysis and deposition to GenBank. Sequence clustering resulted in 6,888 unique ESTs composed of 1,703 tentative consensus (TCs) sequences and 5185 singletons. A large number of ESTs (5717) representing genes of unknown functions were also identified. Among the unique sequences, there were 856 EST-SSRs identified. A total of 290 new EST-based SSR markers were developed and examined for amplification and polymorphism in cultivated peanut and wild species. Resequencing information of selected amplified alleles revealed that allelic diversity could be attributed mainly to differences in repeat type and length in the SSR regions. In addition, a few additional INDEL mutations and substitutions were observed in the regions flanking the microsatellite regions. In addition, some defense-related transcripts were also identified, such as putative oxalate oxidase (EU024476) and NBS-LRR domains. EST data in this study have provided a new source of information for gene discovery and development of SSR markers in cultivated peanut. A total of 16931 ESTs have been deposited to the NCBI GenBank database with accession numbers ES751523 to ES768453.

Guo, Baozhu; Chen, Xiaoping; Hong, Yanbin; Liang, Xuanqiang; Dang, Phat; Brenneman, Tim; Holbrook, Corley; Culbreath, Albert

2009-01-01

223

Remote Sensing of Leaf Water Content in the Near Infrared.  

National Technical Information Service (NTIS)

A stochastic leaf radiation model was used to predict leaf spectral reflectance as a function of leaf water content for a dicot leaf. Simulated spectral reflectances, corresponding to different leaf water contents or equivalent water thicknesses, were ana...

C. J. Tucker

1979-01-01

224

Change in hydraulic properties and leaf traits in a tall rainforest tree species subjected to long-term throughfall exclusion in the perhumid tropics  

NASA Astrophysics Data System (ADS)

A large-scale replicated throughfall exclusion experiment was conducted in a pre-montane perhumid rainforest in Sulawesi (Indonesia) exposing the trees for two years to pronounced soil desiccation. The lack of regularly occurring dry periods and shallow rooting patterns distinguish this experiment from similar experiments conducted in the Amazonian rainforest. We tested the hypotheses that a tree's sun canopy is more affected by soil drought than its shade crown, making tall trees particularly vulnerable even under a perhumid climate, and that extended drought periods stimulate an acclimation in the hydraulic system of the sun canopy. In the abundant and tall tree species Castanopsis acuminatissima (Fagaceae), we compared 31 morphological, anatomical, hydraulic and chemical variables of leaves, branches and the stem together with stem diameter growth between drought and control plots. There was no evidence of canopy dieback. However, the drought treatment led to a 30 % reduction in sapwood-specific hydraulic conductivity of sun canopy branches, possibly caused by the formation of smaller vessels and/or vessel filling by tyloses. Drought caused an increase in leaf size, but a decrease in leaf number, and a reduction in foliar calcium content. The ?13C and ?18O signatures of sun canopy leaves gave no indication of a permanent down-regulation of stomatal conductance during the drought, indicating that pre-senescent leaf shedding may have improved the water status of the remaining leaves. Annual stem diameter growth decreased during the drought, while the density of wood in the recently produced xylem increased in both the stem and sun canopy branches (marginally significant). The sun canopy showed a more pronounced drought response than the shade crown indicating that tall trees with a large sun canopy are more vulnerable to drought stress. We conclude that the extended drought prompted a number of medium- to long-term responses in the leaves, branches and the trunk, which may have reduced drought susceptibility. However, unlike a natural drought, our drought simulation experiment was carried out under conditions of high humidity, which may have dampened drought induced damages.

Schuldt, B.; Leuschner, C.; Horna, V.; Moser, G.; Köhler, M.; van Straaten, O.; Barus, H.

2011-08-01

225

Number Sense  

NSDL National Science Digital Library

Hacker has given you a challenge. Heâll run his number machine to create a number. Then youâll get three numbers between one and nine. The challenge is to make a number that is larger than the one on Hackerâs machine. Be careful though--Hacker will give you numbers that canât be bigger than his!

2008-01-01

226

Costs of measuring leaf area index of corn  

NASA Technical Reports Server (NTRS)

The magnitude of plant-to-plant variability of leaf area of corn plants selected from uniform plots was examined and four representative methods for measuring leaf area index (LAI) were evaluated. The number of plants required and the relative costs for each sampling method were calculated to detect 10, 20, and 50% differences in LAI using 0.05 and 0.01 tests of significance and a 90% probability of success (beta = 0.1). The natural variability of leaf area per corn plant was nearly 10%. Additional variability or experimental error may be introduced by the measurement technique employed and by nonuniformity within the plot. Direct measurement of leaf area with an electronic area meter had the lowest CV, required that the fewest plants be sampled, but required approximately the same amount of time as the leaf area/weight ratio method to detect comparable differences. Indirect methods based on measurements of length and width of leaves required more plants but less total time than the direct method. Unless the coefficients for converting length and width to area are verified frequently, the indirect methods may be biased. When true differences in LAI among treatments exceed 50% of mean, all four methods are equal. The method of choice depends on the resources available, the differences to be detected, and what additional information, such as leaf weight or stalk weight, is also desired.

Daughtry, C. S. T.; Hollinger, S. E.

1984-01-01

227

Direct analysis of single leaf disks for chemopreventive glucosinolates.  

PubMed

Natural isothiocyanates, produced during plant tissue damage from methionine-derived glucosinolates, are potent inducers of mammalian phase 2 detoxification enzymes such as quinone reductase (QR). A greatly simplified bioassay for glucosinolates based on induction and colorimetric detection of QR activity in murine hepatoma cells is described. It is demonstrated that excised leaf disks of Arabidopsis thaliana (ecotype Columbia) can directly and reproducibly substitute for cell-free leaf extracts as inducers of murine QR, which reduces samples preparation to a minimum and maximizes throughput. A comparison of 1 and 3 mm diameter leaf disks indicated that QR inducer potency was proportional to disk circumference (extent of tissue damage) rather than to area. When compared to the QR inducer potency of the corresponding amount of extract, 1 mm leaf disks were equally effective, whereas 3 mm disks were 70% as potent. The QR inducer potency of leaf disks correlated positively with the content of methionine-derived glucosinolates, as shown by the analysis of wild-type plants and mutant lines with lower or higher glucosinolate content. Thus, the microtitre plate-based assay of single leaf disks provides a robust and inexpensive visual method for rapidly screening large numbers of plants in mapping populations or mutant collections and may be applicable to other glucosinolate-producing species. PMID:12099105

Wang, Qiaomei; Grubb, C Douglas; Abel, Steffen

2002-01-01

228

A novel fluence map optimization model incorporating leaf sequencing constraints.  

PubMed

A novel fluence map optimization model incorporating leaf sequencing constraints is proposed to overcome the drawbacks of the current objective inside smoothing models. Instead of adding a smoothing item to the objective function, we add the total number of monitor unit (TNMU) requirement directly to the constraints which serves as an important factor to balance the fluence map optimization and leaf sequencing optimization process at the same time. Consequently, we formulate the fluence map optimization models for the trailing (left) leaf synchronized, leading (right) leaf synchronized and the interleaf motion constrained non-synchronized leaf sweeping schemes, respectively. In those schemes, the leaves are all swept unidirectionally from left to right. Each of those models is turned into a linear constrained quadratic programming model which can be solved effectively by the interior point method. Those new models are evaluated with two publicly available clinical treatment datasets including a head-neck case and a prostate case. As shown by the empirical results, our models perform much better in comparison with two recently emerged smoothing models (the total variance smoothing model and the quadratic smoothing model). For all three leaf sweeping schemes, our objective dose deviation functions increase much slower than those in the above two smoothing models with respect to the decreasing of the TNMU. While keeping plans in the similar conformity level, our new models gain much better performance on reducing TNMU. PMID:20124655

Jin, Renchao; Min, Zhifang; Song, Enmin; Liu, Hong; Ye, Yinyu

2010-02-21

229

Positive and negative effects of leaf shelters on herbivorous insects: linking multiple herbivore species on a willow.  

PubMed

We experimentally examined the effects on other herbivorous insects of leaf shelters constructed by lepidopteran larvae on a willow, Salix miyabeana. Several insect species occupied the vacant leaf shelters. Our experiment using artificial leaf shelters showed that the number of aphids increased with the number of artificial leaf shelters on a shoot, as did the numbers of three ant species ( Camponotus japonicus, Lasius hayashi, and Myrmica jessensis) that entered leaf shelters to collect aphid honeydew. To determine the ant-mediated effect of leaf shelters on herbivorous insects that do not use leaf shelters, we transferred newly hatched larvae of a common leaf beetle, Plagiodera versicolora, to the leaves of shoots with and without artificial leaf shelters. One day after the transfer, larval survival rate was significantly lower on shoots with shelters than on those without shelters, and shoots with shelters had significantly more ants than did shoots without shelters. Our field experiments demonstrated clearly that shelter-making lepidopteran larvae increased the abundance of both aphids and ants and decreased the survival rate of leaf beetle larvae, probably because the larvae were removed by ants that were attracted to the leaf shelters by the aphid colonies. PMID:12768405

Nakamura, Masahiro; Ohgushi, Takayuki

2003-08-01

230

Number Line  

NSDL National Science Digital Library

This iOS app helps students to visualize number sentences and create models for addition, subtractions, multiplication, and division. The number line can be adjusted to represent multiples of numbers from one to one hundred.

Clarity Innovations, Inc.

2013-11-22

231

Story Numbers.  

ERIC Educational Resources Information Center

A concrete approach to prime numbers is presented using rectangles and triangles to construct a building for each number so that each story represents a pair of factors and the triangular-shaped roof represents the number. (MP)

Swafford, Jane; McGinty, Robert

1978-01-01

232

Response to stem bending in forest shrubs: stem or shoot reorientation and shoot release.  

PubMed

Shrubs in the forest understory may be bent by their own weight or by overstory debris. To maintain height growth they must respond to bending by vertical growth of new shoots, reorientation of older axes, or by releasing preventitious buds to form epicormic shoots. I tested for these responses in Ilex verticillata L., Cornus amomum Mill., Gaylussacia baccata (Wang.) K. Koch, Viburnum cassinoides L., Hamamelis virginiana L., and Kalmia latifolia L. For each species, I removed potentially supporting vegetation adjacent to 20 stems, left 10 stems untreated to test for bending by self weight, and bent the remaining 10 stems to 45 degrees to simulate effects of fallen debris. Stem angles and curvatures were measured from before leaf out until just before leaf fall to detect either sagging from self weight or upward bending from tension wood action. Control stems initially leaned out of vertical and five of six species sagged further into a cantilever form. Several control stems failed and bent to the ground. Stems of H. virginiana, I. verticillata, and C. amomum formed tension wood, but only the first two species bent upward. Viburnum cassinoides, G. baccata, and K. latifolia formed no tension wood and sagged further down after being bent. Epicormic shoots formed with varying frequencies in all species except K. latifolia. Epicormic shoots were the major response in C. amomum, V. cassinoides, and G. baccata. New terminal shoots on bent stems recovered toward vertical in I. verticillata and K. latifolia. Negative gravitropic response of shoots was the only recovery mechanism for K. latifolia. PMID:11540964

Wilson, B F

1997-10-01

233

Leaf trait relationships in Australian plant species  

Microsoft Academic Search

Leaf trait data were compiled for 258 Australian plant species from several habitat types dominated by woody perennials. Specific leaf area (SLA), photosynthetic capacity, dark respiration rate and leaf nitrogen (N) and phosphorus (P) concentrations were positively correlated with one another and negatively correlated with average leaf lifespan. These trait relationships were consistent with previous results from global datasets. Together,

Ian J. Wright; Philip K. Groom; Byron B. Lamont; Pieter Poot; Peter B. Reich; E-Detlef Schulze; Erik J. Veneklaas; Mark Westoby; Penrith South

2004-01-01

234

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations of the Department of Agriculture...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when...

2009-01-01

235

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations of the Department of Agriculture...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when...

2010-01-01

236

The molecular genetic analysis of leaf senescence  

Microsoft Academic Search

The cloning of genes induced during leaf senescence and the study of their modes of regulation conducted in the past two years have revealed some of the molecular mechanisms underlying leaf senescence. The identification of genetic mutants that control leaf senescence in Arabidopsis thaliana opened up new possibilities for genetically analyzing leaf senescence in a model system. Encouraging experimental data

Hong Gil Nam

1997-01-01

237

Leaf senescence in Brassica napus: cloning of senescence related genes by subtractive hybridisation  

Microsoft Academic Search

A subtractive hybridisation technique was developed to clone cDNAs representing genes that showed enhanced expression during leaf senescence in Brassica napus. A number of different genes were identified that, when analysed by northern hybridisation, showed different patterns of expression during leaf development but were all expressed at increased levels during senescence. Sequence analysis of these cDNAs showed that several types

Vicky Buchanan-Wollaston; Charles Ainsworth

1997-01-01

238

Fresnel fringes in STEM.  

PubMed

Experiments carried out with a field emmission STEM show several Fresnel fringes along specimen edges, similar to CTEM observation. Analysis of the data shows agreement with computer profiles for idealized edges and the influence of defocusing distance and collector aperture size is discussed. In very coherent detection conditions the number of visible fringes is limited maily by signal-to-noise ratio considerations. In order to observe the maximum number of fringes, a collector aperture must be chosen so that there is a compromise between the limits imposed by the coherence of the detection and the signal-to-noise ratio. PMID:919075

Colliex, C; Craven, A J; Wilson, C J

1977-08-01

239

Adult Stem and Progenitor Cells  

NASA Astrophysics Data System (ADS)

The discovery of adult stem cells in most adult tissues is the basis of a number of clinical studies that are carried out, with therapeutic use of hematopoietic stem cells as a prime example. Intense scientific debate is still ongoing as to whether adult stem cells may have a greater plasticity than previously thought. Although cells with some features of embryonic stem cells that, among others, express Oct4, Nanog and SSEA1 are isolated from fresh tissue, it is not clear if the greater differentiation potential is acquired during cell culture. Moreover, adult more pluripotent cells do not have all pluripotent characteristics typical for embryonic stem cells. Recently, some elegant studies were published in which adult cells could be completely reprogrammed to embryonic stem cell-like cells by overexpression of some key transcription factors for pluripotency (Oct4, Sox2, Klf4 and c-Myc). It will be interesting for the future to investigate the exact mechanisms underlying this reprogramming and whether similar transcription factor pathways are present and/or can be activated in adult more pluripotent stem cells.

Geraerts, Martine; Verfaillie, Catherine M.

240

Stem cell therapy for osteoporosis.  

PubMed

Osteoporosis is a debilitating disease that affects millions of people worldwide. Current osteoporosis treatments are predominantly bone-resorbing drugs that are associated with several side effects. The use of stem cells for tissue regeneration has raised great hope in various fields of medicine, including musculoskeletal disorders. Stem cell therapy for osteoporosis could potentially reduce the susceptibility of fractures and augment lost mineral density by either increasing the numbers or restoring the function of resident stem cells that can proliferate and differentiate into bone-forming cells. Such osteoporosis therapies can be carried out by exogenous introduction of mesenchymal stem cells (MSCs), typically procured from bone marrow, adipose, and umbilical cord blood tissues or through treatments with drugs or small molecules that recruit endogenous stem cells to osteoporotic sites. The main hurdle with cell-based osteoporosis therapy is the uncertainty of stem cell fate and biodistribution following cell transplantation. Therefore, future advancements will focus on long-term engraftment and differentiation of stem cells at desired bone sites for tangible clinical outcome. PMID:24407712

Antebi, Ben; Pelled, Gadi; Gazit, Dan

2014-03-01

241

Stem cells, cancer, and cancer stem cells  

Microsoft Academic Search

Stem cell biology has come of age. Unequivocal proof that stem cells exist in the haematopoietic system has given way to the prospective isolation of several tissue-specific stem and progenitor cells, the initial delineation of their properties and expressed genetic programmes, and the beginnings of their utility in regenerative medicine. Perhaps the most important and useful property of stem cells

Tannishtha Reya; Sean J. Morrison; Michael F. Clarke; Irving L. Weissman

2001-01-01

242

LAMINA: a tool for rapid quantification of leaf size and shape parameters  

PubMed Central

Background An increased understanding of leaf area development is important in a number of fields: in food and non-food crops, for example short rotation forestry as a biofuels feedstock, leaf area is intricately linked to biomass productivity; in paleontology leaf shape characteristics are used to reconstruct paleoclimate history. Such fields require measurement of large collections of leaves, with resulting conclusions being highly influenced by the accuracy of the phenotypic measurement process. Results We have developed LAMINA (Leaf shApe deterMINAtion), a new tool for the automated analysis of images of leaves. LAMINA has been designed to provide classical indicators of leaf shape (blade dimensions) and size (area), which are typically required for correlation analysis to biomass productivity, as well as measures that indicate asymmetry in leaf shape, leaf serration traits, and measures of herbivory damage (missing leaf area). In order to allow Principal Component Analysis (PCA) to be performed, the location of a chosen number of equally spaced boundary coordinates can optionally be returned. Conclusion We demonstrate the use of the software on a set of 500 scanned images, each containing multiple leaves, collected from a common garden experiment containing 116 clones of Populus tremula (European trembling aspen) that are being used for association mapping, as well as examples of leaves from other species. We show that the software provides an efficient and accurate means of analysing leaf area in large datasets in an automated or semi-automated work flow.

Bylesjo, Max; Segura, Vincent; Soolanayakanahally, Raju Y; Rae, Anne M; Trygg, Johan; Gustafsson, Petter; Jansson, Stefan; Street, Nathaniel R

2008-01-01

243

Change in hydraulic properties and leaf traits of a tall rainforest tree species subjected to long-term throughfall exclusion in the perhumid tropics  

NASA Astrophysics Data System (ADS)

In a throughfall displacement experiment on Sulawesi, Indonesia, three 0.16 ha stands of a premontane perhumid rainforest were exposed to a two-year soil desiccation period that reduced the soil moisture in the upper soil layers beyond the conventional wilting point. About 25 variables, including leaf morphological and chemical traits, stem diameter growth and hydraulic properties of the xylem in the trunk and terminal twigs, were investigated in trees of the tall-growing tree species Castanopsis acuminatissima (Fagaceae) by comparing desiccated roof plots with nearby control plots. We tested the hypotheses that this tall and productive species is particularly sensitive to drought, and the exposed upper sun canopy is more affected than the shade canopy. Hydraulic conductivity in the xylem of terminal twigs normalised to vessel lumen area was reduced by 25%, leaf area-specific conductivity by 10-33% during the desiccation treatment. Surprisingly, the leaves present at the end of the drought treatment were significantly larger, but not smaller in the roof plots, though reduced in number (about 30% less leaves per unit of twig sapwood area), which points to a drought effect on the leaf bud formation while the remaining leaves may have profited from a surplus of water. Mean vessel diameter and axial conductivity in the outermost xylem of the trunk were significantly reduced and wood density increased, while annual stem diameter increment decreased by 26%. In contradiction to our hypotheses, (i) we found no signs of major damage to the C. acuminatissima trees nor to any other drought sensitivity of tall trees, and (ii) the exposed upper canopy was not more drought susceptible than the shade canopy.

Schuldt, B.; Leuschner, C.; Horna, V.; Moser, G.; Köhler, M.; Barus, H.

2010-11-01

244

The stem cell patent landscape as relevant to cancer vaccines.  

PubMed

Cancer vaccine targeting cancer stem cells is proposed to serve as a potent immunotherapy. Thus, it would be useful to examine the main trends in stem cell patenting activity as a guide for those seeking to develop such cancer vaccines. We found that a substantial number of stem cell patents were granted up to the end of 2010, including ~2000 issued in the US. Many of these have been filed since 2001, including 7,551 applications in the US. Stem cell development, as evidenced by the numbers of PubMed articles, has matured steadily in recent years. However, the other metrics, such as the number of patent applications, the technology-science linkage and the number of patent assignees, have been stagnant. Moreover, the ownership of stem cell patents is still quiet fragmented across multiple organizations, and the number of stem cell patent assignees from the business sector has not increased significantly. Academic and nonprofit institutions not only account for a large share of stem cell patents but also apply for patents continually. Based on this analysis, the strength of stem cell resources seems to remain stagnant in recent years due to the ban on government funding of embryonic stem cell research. Furthermore, the patent prosecution or technical barriers in the field of stem cells would be another main reason that the number of US-issued stem cell patents for each application have been in gradual decline since 2000. Therefore, we consider stem cell technology to still be under development. PMID:21957493

Wang, Shyh-Jen

2011-10-01

245

Theoretical concepts of tissue stem cell organization  

Microsoft Academic Search

Summary Many recent experimental findings on heterogeneity, flexibility, and plasticity of tissue stem cells are challenging the classical stem cell concept of a pre-defined, cell-intrinsic developmental program. Moreover, a number of these results are not consistent with the paradigm of a hierarchically structured stem cell population with a uni-directional development. Non-hierarchical, self-organizing systems provide a more elegant and comprehensive alternative

Ingo Roeder; Joerg Galle; Markus Loeffler

246

Stem cells and the Planarian Schmidtea mediterranea  

Microsoft Academic Search

In recent years, stem cells have been heralded as potential therapeutic agents to address a large number of degenerative diseases. Yet, in order to rationally utilize these cells as effective therapeutic agents, and\\/or improve treatment of stem-cell-associated malignancies such as leukemias and carcinomas, a better understanding of the basic biological properties of stem cells needs to be acquired. A major

Alejandro Sánchez Alvarado

2007-01-01

247

Pluripotent stem cells and their niches  

Microsoft Academic Search

The ability of stem cells to self-renew and to replace mature cells is fundamental to ontogeny and tissue regeneration. Stem\\u000a cells of the adult organism can be categorized as mono-, bi-, or multipotent, based on the number of mature cell types to\\u000a which they can give rise. In contrast, pluripotent stem cells of the early embryo have the ability to

M. William Lensch; Laurence Daheron; Thorsten M. Schlaeger

2006-01-01

248

Multi-trait interactions, not phylogeny, fine-tune leaf size reduction with increasing altitude  

PubMed Central

Background and Aims Despite long-held interest, knowledge on why leaf size varies widely among species is still incomplete. This study was conducted to assess whether abiotic factors, phylogenetic histories and multi-trait interactions act together to shape leaf size. Methods Fifty-seven pairs of altitudinal vicariant species were selected in northern Spain, and leaf area and a number of functionally related leaf, shoot and whole plant traits were measured for each pair. Structural equation modelling helped unravel trait interactions affecting leaf size, and Mantel tests weighed the relative relevance of phylogeny, environment and trait interactions to explain leaf size reduction with altitude. Key Results Leaves of highland vicariants were generally smaller than those of lowlands. However, the extent of leaf size reduction with increasing altitude was widely variable among genera: from approx. 700 cm2 reduction (96 % in Polystichum) to approx. 30 cm2 increase (37 % in Sorbus). This was partially explained by shifts in leaf, shoot and whole plant traits (35–64 % of explained variance, depending on models), with size/number trade-offs more influential than shifts in leaf form and leaf economics. Shifts in traits were more important than phylogenetic distances or site-specific environmental variation in explaining the degree of leaf size reduction with altitude. Conclusions Ecological filters, constraints due to phylogenetic history (albeit modest in the study system), and phenotypic integration contribute jointly to shape single-trait evolution. Here, it was found that phenotypic change was far more important than shared ancestry to explaine leaf size differences of closely related species segregated along altitudes.

Milla, Ruben; Reich, Peter B.

2011-01-01

249

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups  

Microsoft Academic Search

Based on prior evidence of coordinated multiple leaf trait scaling, we hypothesized that variation among species in leaf\\u000a dark respiration rate (R\\u000a d) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic\\u000a capacity (A\\u000a max). However, it is not known whether such scaling, if it exists, is similar among

Peter B. Reich; Michael B. Walters; David S. Ellsworth; James M. Vose; John C. Volin; Charles GreshamWilliam; William D. Bowman

1998-01-01

250

Number Flash  

NSDL National Science Digital Library

This iOS app helps students make the transition from counting to number recognition by thinking of a number of objects in relation to five and ten. The app displays a set number of items from one to twenty in ten frames then flashes away after the preset number of seconds. The user must identify the number that was shown on the ten frames.

Mark, Mitchell

2013-03-10

251

Stem diameter changes before bud opening in Zelkova serrata saplings.  

PubMed

It is well known that stems of woody plants shrink and swell diurnally. These fluctuations of stem diameter are induced mainly by the changes of water contents in plants, which are caused by the combination of leaf transpiration and root absorption of water. This implies that dormant-like deciduous broadleaved trees in a leafless state should show no or less changes in stem diameter. However, some physiological activities in woody plants are also known to precede their winter bud opening. Whether and how diameter changes occur in deciduous tree stems during winter was investigated using Zelkova serrata saplings in a leafless state. Measurements of stem diameter changes were done for more than 4 months continuously. The saplings showed distinct diameter changes with periodicities from diurnal to a few weeks, and these changes were initiated 2 months before winter bud opening. These results indicate that some physiological and/or developmental activities occur in the stem of deciduous trees before winter bud opening, and do not correspond to changes in water relations as a result of leaf transpiration. These internal activities cause fluctuations in stem diameter prior to winter bud opening in deciduous trees. PMID:12605295

Yoda, Kiyotsugu; Wagatsuma, Hiromichi; Suzuki, Mitsuo; Suzuki, Hitoshi

2003-02-01

252

STEM Planet  

NSDL National Science Digital Library

STEM Planet is a well designed website that is aimed at students of all levels and ages. The site is comprised of "employees of the National Network of Digital Schools (NNDS), a non-profit developer of the Lincoln Interactive online curriculum." These employees believe that students "succeed when their educational program offers a wide variety of learning opportunities." Visitors to the site will find that the learning opportunities consist of DIY experiments, discussion topics, polls, quizzes and activities. Some examples include making a homemade battery, origami engineering, taking a quiz on space phenomena, and exploring quantum mechanics. Visitors can join and comment on the Science, Technology, Engineering and Math "discussions" by simply registering on the site. Those only interested in reading the comments made in the forums under the discussion tab need not register. The "Experts" tab allows visitors to see all the great minds behind STEM Planet, including an extremely bright 14 year old.

2012-02-07

253

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

254

Leaf exsertion, leaf elongation, and leaf senescence in Eriophorum vaginatum and Carex Bigelowii  

SciTech Connect

Most of the common sedges of arctic vegetation show a pattern of leaf production in which the exsertion and elongation of new leaves is more or less simultaneous with the senescence of old leaves. The present study was designed to increase our understanding of the variability sequential leaf production by arctic sedges, and to determine some of the controls on that variability. We did this in two ways: first, we compared the sequential patterns of leaf growth and senescence in E. vaginatum with those of Carex Bigelowii Torr. at two tussock tundra sites near Toolik Lake on the North Slope of Alaska. Second, we compared the responses of leaf growth in these species in control and fertilized plots and in two microenvironments thought to differ sharply in nutrient availability and total productivity. 29 refs., 28 figs., 2 tabs.

Shaver, G.R.; Yandow, T.; Laundre, J.

1990-01-01

255

Stem Transitions  

NSDL National Science Digital Library

This one-year project is being led by the Center for Occupational Research and Development (CORD). Funded by the U.S. Department of Education Office of Vocational and Adult Education under cooperative agreement with the League for Innovation in the Community College, the project is building on the work of the College and Career Transitions Initiative begun by the League in 2003. At the heart of the project are the six Science, Technology, Engineering, and Mathematics (STEM) career clusters that have provided the context for instructional materials that demonstrate the convergence of academic and technical content at the community college level. CORD staff, in conjunction with 38 faculty conferees from community colleges across the country, have developed 63 integrated curriculum projects for use in math, science, and technical courses in the six STEM-related clusters health science; information technology; manufacturing; transportation; science, technology, engineering and mathematics; and agriculture. The classroom-ready projects are intended to aid in student mastery of essential mathematics and science concepts while motivating students to pursue STEM-related careers.

2009-11-27

256

Stem cell activation by light guides plant organogenesis  

PubMed Central

Leaves originate from stem cells located at the shoot apical meristem. The meristem is shielded from the environment by older leaves, and leaf initiation is considered to be an autonomous process that does not depend on environmental cues. Here we show that light acts as a morphogenic signal that controls leaf initiation and stabilizes leaf positioning. Leaf initiation in tomato shoot apices ceases in the dark but resumes in the light, an effect that is mediated through the plant hormone cytokinin. Dark treatment also affects the subcellular localization of the auxin transporter PIN1 and the concomitant formation of auxin maxima. We propose that cytokinin is required for meristem propagation, and that auxin redirects cytokinin-inducible meristem growth toward organ formation. In contrast to common wisdom over the last 150 years, the light environment controls the initiation of lateral organs by regulating two key hormones: auxin and cytokinin.

Yoshida, Saiko; Mandel, Therese; Kuhlemeier, Cris

2011-01-01

257

Nifty Numbers!  

NSDL National Science Digital Library

You will be working with numbers in all sorts of ways. First, you will play cop by picking numbers based on their divisibility. Then you will be adding and subtracting fractions in two fun and exciting games. First, as a cop, you will catch numbers that are divisible by which ever number you pick, avoinding crashing into non-divisible numbers. Number Cop-Divisibility Now, play Fishy Fractions! and help feed the seagull by practicing adding fractions. Make sure you read the instructions before getting started! Make sure to simplify your answers! After you ...

Miss.cochran

2008-03-26

258

Comparison of vegetative anatomy of Piperales. II. Leaf.  

PubMed

Many characters of leaf (hair, hypodermal cells, palisade layers, intercellular space, distinction between spongy and palisade parenchyma, "palisade ratio", distribution of collenchyma and sclerenchyma, presence or absence of starch grains, calcium oxalate crystals, number, shape and arrangement of bundles of petiole) are useful distinguishing characters. Reduction of palisade layers seems to be the trend of evolution in Piper and Peperomia. PMID:602574

Datta, P C; Dasgupta, A

1977-01-01

259

Late-spring leaf scorch of maple and beech trees  

Microsoft Academic Search

Investigation of a number of vegetation injury complaints in early June 1971, in which the complainants suspected air pollutants as the causal agents led to the discovery of a widespread physiological leaf scorch of maple and beech trees in the Niagara peninsula area of Southern Ontario. A description of the symptoms of injury, the species of trees affected and the

S. N. Linzon; W. D. McIlveen; R. G. Pearson

1972-01-01

260

Tooth Numbering  

MedlinePLUS

... numbered as well. Illustrations created by Simple Steps designer Michael Becker Universal Numbering System Adults In this ... indicates that it is a deciduous (primary or "baby") tooth. So, a child's first tooth on the ...

261

The future for stem cell research  

Microsoft Academic Search

Stem cells have offered much hope by promising to greatly extend the numbers and range of patients who could benefit from transplants, and to provide cell replacement therapy to treat debilitating diseases such as diabetes, Parkinson's and Huntington's disease. The issue of stem cell research is politically charged, prompting biologists to begin engaging in ethical debates, and generating in the

Robin Lovell-Badge

2001-01-01

262

Negative Numbers  

NSDL National Science Digital Library

This article is an account of how negative numbers became part of the "vocabulary" of mathematicians and of some of the earliest appearances of negative numbers in calculations of the ancient civilizations of China, India and Greece. Although negative numbers were used in calculations, negative answers to mathematical problems were considered meaningless or impossible. The troubled history of negative numbers presented in this article shows how the simple mathematical principles taken for granted today have taken thousands of years to develop.

Howard, Jill

2009-05-01

263

Measuring leaf material in ginned cotton from surface images  

NASA Astrophysics Data System (ADS)

Digitized images from black and white video cameras are being used to measure the area and numbers of leaf particles in cotton after lint cleaning. The method is now used to provide trash grades for 16 - 18 million bales of cotton prepared for market each year. Small samples are compressed against a glass window and illuminated with two small incandescent lamps for imaging. Leaf area readings are automatically adjusted for differences in lint greyness. The accuracy of this method compares well with gravimetric measurements of non-lint content.

Taylor, Robert A.

1995-01-01

264

Number Balance  

NSDL National Science Digital Library

This open-ended interactive Flash applet helps students develop operation and number sense, facility with number facts, and understanding of equations. Users designate single-digit whole numbers or integers and operations on both sides of an equation and test for balance. Users can enter numbers by using the keyboard or arrow buttons or by dragging number tiles. Each element can be hidden and a seesaw may be toggled on/off. Teachers may use this applet to lead instruction, or students may use it independently to perform specific investigations or explore freely. Supplementary documents include Objectives, containing teaching suggestions, and a student recording sheet.

Bunker, Dan

2005-01-01

265

Stem Cell Transplants  

MedlinePLUS

What Are Stem Cells? As you probably remember from biology class, every living thing is made up of cells — including the human body. ... can become new cells like this. Blood Stem Cells When you hear about stem cell transplants, they ...

266

Age-associated inflammation inhibits epidermal stem cell function  

PubMed Central

Altered stem cell homeostasis is linked to organismal aging. However, the mechanisms involved remain poorly understood. Here we report novel alterations in hair follicle stem cells during skin aging, including increased numbers, decreased function, and an inability to tolerate stress. Performing high-throughput RNA sequencing on aging stem cells, cytokine arrays, and functional assays, we identify an age-associated imbalance in epidermal Jak–Stat signaling that inhibits stem cell function. Collectively, this study reveals a role for the aging epidermis in the disruption of cytokine and stem cell homeostasis, suggesting that stem cell decline during aging may be part of broader tumor-suppressive mechanisms.

Doles, Jason; Storer, Mekayla; Cozzuto, Luca; Roma, Guglielmo; Keyes, William M.

2012-01-01

267

A Perivascular Niche for Brain Tumor Stem Cells  

Microsoft Academic Search

SUMMARY Cancers are believed to arise from cancer stem cells (CSCs), but it is not known if these cells remain dependent upon the niche microenvironments that regulate normal stem cells. We show that endo- thelial cells interact closely with self-renewing brain tumor cells and secrete factors that maintain these cells in a stem cell-like state. Increasing the number of endothelial

Christopher Calabrese; Helen Poppleton; Mehmet Kocak; Twala L. Hogg; Christine Fuller; Blair Hamner; Eun Young Oh; M. Waleed Gaber; David Finklestein; Meredith Allen; Adrian Frank; Ildar T. Bayazitov; Stanislav S. Zakharenko; Amar Gajjar; Andrew Davidoff; Richard J. Gilbertson

2007-01-01

268

Placenta—an alternative source of stem cells  

Microsoft Academic Search

The two most promising practical applications of human stem cells are cellular replacement therapies in human disease and toxicological screening of candidate drug molecules. Both require a source of human stem cells that can be isolated, purified, expanded in number and differentiated into the cell type of choice in a controlled manner. Currently, uses of both embryonic and adult stem

Tiina Matikainen; Jarmo. Laine

2005-01-01

269

Leaf mutants in diploid red clover (Trifolium pratense L.).  

PubMed

Leaf mutants were isolated and genetically stabilised in diploid red clover (Trifolium pratense). The major alteration showed normal trifoliolate leaves changed into multifoliolate leaves composed of 4-, 5-, 6- and 7 leaflets. As a result of recombination with other mutant alleles several genotypes were isolated with a different mode of leaf setting, different shapes and sizes of leaflets, variations in the whole plant habit, etc. A careful description was made of the mutant morphology and the development and genetic background was estimated as (h sl (2) ). The mutants demonstrated no disturbances in their generative reproduction and as a rule set seeds better than the standards. The primary evaluation permits a conclusion that the leaf alteration (complexity) is governed by at least three recessive pairs of alleles of additive action. The phenotypic expression of the altered leaves depends simply on the number of recessive alleles. Apart from the above there were some modifying genes of incomplete penetration. PMID:24311341

Jaranowski, J K; Broda, Z

1978-05-01

270

Leaf litter bags as an index to populations of northern two-lined salamanders (Eurycea bislineata)  

USGS Publications Warehouse

Concern about recent amphibian declines has led to research on amphibian populations, but few statistically tested, standardized methods of counting amphibians exist. We tested whether counts of northern two-lined salamander larvae (Eurycea bislineata) sheltered in leaf litter bags--a relatively new, easily replicable survey technique--had a linear correlation to total number of larvae. Using experimental enclosures placed in streams, we compared number of salamanders found in artificial habitat (leaf litter bags) with total number of salamanders in each enclosure. Low numbers of the animals were found in leaf litter bags, and the relative amount of variation in the index (number of animals in leaf litter bags compared to total number of animals in stream enclosures) was high. The index of salamanders in leaf litter bags was not significantly related to total number of salamanders in enclosures for two-thirds of the replicates or with pooled replicates (P= 0.066). Consequently, we cannot recommend using leaf litter bags to index populations of northern two-lined salamanders.

Chalmers, R.J.; Droege, S.

2002-01-01

271

Microbial Dynamics on Decaying Leaf Litter in an Ohio Stream  

NASA Astrophysics Data System (ADS)

Deciduous leaf litter is an important source of energy for many streams. Fungi (aquatic hyphomycetes) and bacteria play important roles in litter processing, but the colonization dynamics of these groups across different leaf types is not well described. We examined fungal and bacterial colonization on sugar maple and white oak leaves in a hardwater stream in Northeastern Ohio from November 2003 through May 2004. Triplicate samples of each leaf type were collected from litter bags approximately monthly. The dry weight and organic content of the leaves were measured. Fungal biomass was determined from ergosterol concentrations in the samples. Image analysis of DAPI-stained cells and standard conversion factors were used to calculate bacterial biomass. On most dates, fungal biomass was similar on leaf types, and 10-fold higher than bacterial biomass. Throughout the study, bacterial numbers and biomass were greater on sugar maple than white oak. Sugar maple leaves decayed faster than oak leaves, but this was not reflected in the biomass of aquatic hyphomycetes, rather in the abundance of bacteria. Although fungi are considered the main organisms in litter breakdown, bacteria showed a greater response to leaf quality in this study, and may be more important than the biomass suggests.

Das, M.; Royer, T. V.; Leff, L. G.

2005-05-01

272

Assessing quantitative resistance against Leptosphaeria maculans (phoma stem canker) in Brassica napus (oilseed rape) in young plants.  

PubMed

Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of canker symptoms on the stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the stem by leaf lamina inoculation; stage 2, growth in stem tissues to produce stem canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of stem canker and amount of L. maculans DNA in stem tissues. GFP-labelled L. maculans spread more quickly from the stem cortex to the stem pith in A30 than in C119. Stem canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases. PMID:24454767

Huang, Yong-Ju; Qi, Aiming; King, Graham J; Fitt, Bruce D L

2014-01-01

273

STEM Attrition: College Students' Paths into and out of STEM Fields. Statistical Analysis Report. NCES 2014-001  

ERIC Educational Resources Information Center

Producing sufficient numbers of graduates who are prepared for science, technology, engineering, and mathematics (STEM) occupations has become a national priority in the United States. To attain this goal, some policymakers have targeted reducing STEM attrition in college, arguing that retaining more students in STEM fields in college is a…

Chen, Xianglei

2013-01-01

274

Number Grids and Number Triangles  

NSDL National Science Digital Library

Practice counting, counting by tens, place value, and fact families by entering your answers into the blank boxes; click the big blue and green buttons to check your work. Each of the five levels of Number Grid activities displays a section of a matrix containing a set of of consecutive whole numbers. A move from one number to the next within a row corresponds to a change of one; a move from one number to the next within a column refers to a change of ten. The three levels of Number Triangle activities provide practice with fact families and inverse relationships through flash cards. An addition/subtraction Number Triangle has two addends and a sum; a multiplication/division Number Triangle has two factors and a product.

Brown, Quincy; Fetter, Annie

2006-08-01

275

Life in the Leaf Litter  

NSDL National Science Digital Library

Produced by the Center for Biodiversity and Conservation, Life in the Leaf Litter is a guide to the diversity of soil organisms and the crucial role that invertebrates play in woodland ecosystems. The booklet was based, in part, on a leaf litter survey conducted by the CBC's Metro Program and the Museum's Division of Invertebrate Zoology in Central Park's woodlands, which led to the discovery of a new genus and species of centipede, Nannarrup hoffmani. The booklet may be downloaded as a pdf or ordered free of charge.

276

Understanding the effect of carbon status on stem diameter variations  

PubMed Central

Background Carbon assimilation and leaf-to-fruit sugar transport are, along with plant water status, the driving mechanisms for fruit growth. An integrated comprehension of the plant water and carbon relationships is therefore essential to better understand water and dry matter accumulation. Variations in stem diameter result from an integrated response to plant water and carbon status and are as such a valuable source of information. Methods A mechanistic water flow and storage model was used to relate variations in stem diameter to phloem sugar loading and sugar concentration dynamics in tomato. The simulation results were compared with an independent model, simulating phloem sucrose loading at the leaf level based on photosynthesis and sugar metabolism kinetics and enabled a mechanistic interpretation of the ‘one common assimilate pool’ concept for tomato. Key Results Combining stem diameter variation measurements and mechanistic modelling allowed us to distinguish instantaneous dynamics in the plant water relations and gradual variations in plant carbon status. Additionally, the model combined with stem diameter measurements enabled prediction of dynamic variables which are difficult to measure in a continuous and non-destructive way, such as xylem water potential and phloem hydrostatic potential. Finally, dynamics in phloem sugar loading and sugar concentration were distilled from stem diameter variations. Conclusions Stem diameter variations, when used in mechanistic models, have great potential to continuously monitor and interpret plant water and carbon relations under natural growing conditions.

De Swaef, Tom; Driever, Steven M.; Van Meulebroek, Lieven; Vanhaecke, Lynn; Marcelis, Leo F. M.; Steppe, Kathy

2013-01-01

277

STEM Careers Exploration  

NSDL National Science Digital Library

This activity includes a presentation with links to videos about scientists and engineers working with NASA's Global Precipitation Measurement Mission (from the Faces of GPM series), as well as other STEM careers videos, followed by a number of links to online career resources. It is designed to be used by students working at their own pace, choosing which videos and links they are interested in watching and exploring, but could also be used with a larger group. As part of the activity, students identify personal skills and abilities related to career interests and develop a career goal. Includes a student capture sheet with guiding questions.

278

Estimating leaf biochemistry using the PROSPECT leaf optical properties model  

Microsoft Academic Search

The biophysical, biochemical, and optical properties of 63 fresh leaves and 58 dry leaves were measured to investigate the potential of remote sensing to estimate the leaf biochemistry from space. Almost 2000 hemispherical reflectance and transmittance spectra were acquired from 400 nm to 2500 nm using a laboratory spectrophotometer. The amount of chlorophyll, water, protein, cellulose, hemicellulose, lignin, and starch

S. Jacquemoud; S. L. Ustin; J. Verdebout; G. Schmuck; G. Andreoli; B. Hosgood

1996-01-01

279

Stem cell therapy for heart failure.  

PubMed

The last decade has witnessed the publication of a large number of clinical trials, primarily using bone marrow-derived stem cells as the injected cell. Much has been learned through these "first-generation" clinical trials. The considerable advances in our understanding include (1) cell therapy is safe, (2) cell therapy has been modestly effective, (3) the recognition that in humans bone marrow-derived stem cells do not transdifferentiate into cardiomyocytes or new blood vessels (or at least in sufficient numbers to have any effect). The primary mechanism of action for cell therapy is now believed to be through paracrine effects that include the release of cytokines, chemokines, and growth factors that inhibit apoptosis and fibrosis, enhance contractility, and activate endogenous regenerative mechanisms through endogenous circulating or site-specific stem cells. The new direction for clinical trials includes the use of stem cells capable of cardiac lineage, such as endogenous cardiac stem cells. PMID:24595173

Michler, Robert E

2014-01-01

280

Stem Cell Therapy for Heart Failure  

PubMed Central

The last decade has witnessed the publication of a large number of clinical trials primarily using bone marrow-derived stem cells as the injected cell. These “first-generation” clinical trials have advanced our understanding and shown us that (1) cell therapy is safe, (2) cell therapy has been modestly effective, and (3) in humans, bone marrow-derived stem cells do not transdifferentiate into cardiomyocytes or new blood vessels (or at least in sufficient numbers to have any effect). The primary mechanism of action for cell therapy is now believed to be through paracrine effects that include the release of cytokines, chemokines, and growth factors that inhibit apoptosis and fibrosis, enhance contractility, and activate endogenous regenerative mechanisms through endogenous circulating or site-specific stem cells. The new direction for clinical trials includes the use of stem cells capable of cardiac lineage, such as endogenous cardiac stem cells.

2013-01-01

281

Chili leaf curl betasatellite is associated with a distinct recombinant begomovirus, Pepper leaf curl Lahore virus, in Capsicum in Pakistan.  

PubMed

Capsium spp. are an important vegetable crop cultivated through Pakistan. Leaf curl disease is the major disease of Capsicum spp. in Pakistan caused by viruses. The disease has previously been shown to be associated with begomoviruses and betasatellites. We have cloned and sequenced a begomovirus and its associated betasatellite from Capsicum originating from central Pakistan. The begomovirus isolated was distinct from all previously characterised viruses and we propose the name Pepper leaf curl Lahore virus (PepLCLV) for this new species. Comparison of the sequence of PepLCLV with previously characterised begomoviruses shows it likely to have resulted from recombination between Papaya leaf curl virus and Chili leaf curl virus (ChiLCV), two species that have previously been identified in Pakistan. The betasatellite associated with PepLCLV in Capsicum was identified as Chili leaf curl betasatellite (ChLCB). This is the first identification of a cognate begomovirus for ChLCB infecting Capsicum, although this betasatellite has been shown in association with ChiLCV infecting potato in Pakistan. PepLCLV is one of an increasing number of monopartite begomoviruses shown to be associated with a betasatellite and one of the numerous species that affect Capsicum. In view of their only having been identified in Pakistan, PepLCLV and ChLCB likely represent a geographically distinct, Capsicum adapted, begomovirus-betasatellite complex. PMID:20079779

Tahir, Muhammad; Haider, Muhammad Saleem; Briddon, Rob W

2010-04-01

282

Role of Oxidative Stress in Stem, Cancer, and Cancer Stem Cells  

PubMed Central

The term ‘‘oxidative stress” refers to a cell’s state characterized by excessive production of reactive oxygen species (ROS) and oxidative stress is one of the most important regulatory mechanisms for stem, cancer, and cancer stem cells. The concept of cancer stem cells arose from observations of similarities between the self-renewal mechanism of stem cells and that of cancer stem cells, but compared to normal stem cells, they are believed to have no control over the cell number. ROS have been implicated in diverse processes in various cancers, and generally the increase of ROS in cancer cells is known to play an important role in the initiation and progression of cancer. Additionally, ROS have been considered as the most significant mutagens in stem cells; when elevated, blocking self-renewal and at the same time, serving as a signal stimulating stem cell differentiation. Several signaling pathways enhanced by oxidative stress are suggested to have important roles in tumorigenesis of cancer or cancer stem cells and the self-renewal ability of stem or cancer stem cells. It is now well established that mitochondria play a prominent role in apoptosis and increasing evidence supports that apoptosis and autophagy are physiological phenomena closely linked with oxidative stress. This review elucidates the effect and the mechanism of the oxidative stress on the regulation of stem, cancer, and cancer stem cells and focuses on the cell signaling cascades stimulated by oxidative stress and their mechanism in cancer stem cell formation, as very little is known about the redox status in cancer stem cells. Moreover, we explain the link between ROS and both of apoptosis and autophagy and the impact on cancer development and treatment. Better understanding of this intricate link may shed light on mechanisms that lead to better modes of cancer treatment.

Dayem, Ahmed Abdal; Choi, Hye-Yeon; Kim, Jung-Hyun; Cho, Ssang-Goo

2010-01-01

283

Matching Numbers  

NSDL National Science Digital Library

This interactive Flash version of the familiar game Concentration helps students develop number sense by matching various symbolic and pictorial representations of single digit numbers. The scoring rewards a systematic strategy over random guessing. The resource includes teacher notes with suggestions for implementation and differentiation, discussion questions, and printable sets of cards (pdf).

2014-01-01

284

Deciduous leaf drop reduces insect herbivory  

Microsoft Academic Search

Deciduous leaf fall is thought to be an adaptation that allows plants living in seasonal environments to reduce water loss\\u000a and damage during unfavorable periods while increasing photosynthetic rates during favorable periods. Observations of natural\\u000a variation in leaf shedding suggest that deciduous leaf fall may also allow plants to reduce herbivory. I tested this hypothesis\\u000a by experimentally manipulating leaf retention

Richard Karban

2007-01-01

285

Relationship of water status to vegetative growth and leaf gas exchange of peach (Prunus persica) trees on different rootstocks.  

PubMed

We investigated relationships between tree water status, vegetative growth and leaf gas exchange of peach trees growing on different rootstocks under field conditions. Tree water status was manipulated by partially covering (0, approximately 30 and approximately 60%) the tree canopies on individual days and then evaluating the effects of tree water status on vegetative growth and leaf gas exchange. Early morning stem water potentials were approximately -0.4 MPa for trees in all treatments, but mean midday values ranged from -1.1 to -1.7 MPa depending on rootstock and canopy coverage treatment. Relative shoot extension growth rate, leaf conductance, transpiration rate and net CO2 exchange rate differed significantly among trees in the different rootstocks and canopy coverage treatments. Shoot extension growth rate, leaf conductance, leaf transpiration rate and leaf net CO2 exchange rate were linearly correlated with midday stem water potential. These relationships were independent of the rootstock and canopy coverage treatments, indicating that tree water relations are probably directly involved in the mechanism that imparts vegetative growth control by selected peach rootstocks. PMID:16815835

Solari, Luis I; Johnson, Scott; DeJong, Theodore M

2006-10-01

286

Modeling Leaf Production and Senescence in Wheat  

Microsoft Academic Search

4 Abstract: A major component in a crop growth model is leaf area development, which has a major influence on photosynthesis and transpiration. The knowledge about the leaf area development of wheat especially in high temperature environments is incomplete. The aim of this study was to quantify leaf production and senescence of 15 spring wheat cultivars. Field experiments were conducted

J. Pourreza; A. Soltani; A. Naderi; A. Aynehband

2009-01-01

287

Pharmacognostic studies of the leaves and stem of Careya arborea Roxb.  

PubMed Central

Objective To study detailed pharmacognostic profile of leaves and stem of Careya arborea (C. arborea) Roxb. (Lecthyidaceae), an important medicinal plant in the Indian system of medicine. Methods Leaf and stem samples of C. arborea were studied by macroscopical, microscopical, physicochemical, phytochemical, fluorescence analysis of powder of the plant and other methods for standardization recommended by WHO. Results Macroscopically, the leaves are simple, broadly obovate in shape, acuminate apex with crenate, dentate margin, petioles (0.1–1.8 cm) long. Microscopically, the leaf showed the presence of median large size vascular bundle covered with fibrous bundle sheath, arrangement of xylem in cup shape and presence of cortical vascular bundle, patches of sclerenchyma, phloem fibers in groups and brown pigment containing cells in stem are some of the diagnostic features noted from anatomical study. Powder microscopy of leaf revealed the presence of parenchyma cells, xylem with pitted vessels and epidermis with anisocytic stomata. The investigations also included leaf surface data; quantitative leaf microscopy and fluorescence analysis. Physiochemical parameters such as loss on drying, swelling index, extractive values and ash values were also determined and results showed that total ash of the stem bark was about two times higher than leaf and water soluble extractive value of leaf and stem bark was two times higher than alcohol soluble extractive value. Preliminary phytochemical screening showed the presence of triterpenoids, saponins, tannins and flavonoids. Conclusions The results of the study can serve as a valuable source of information and provide suitable standards for identification of this plant material in future investigations and applications.

Gupta, Prakash Chandra; Sharma, Nisha; Rao, Ch V

2012-01-01

288

Stem xylem features in three Quercus (Fagaceae) species along a climatic gradient in NE Spain  

Microsoft Academic Search

Stem xylem features in two evergreen Quercus species (Q. coccifera and Q. ilex) and a deciduous one (Q. faginea) were analysed along an Atlantic-Mediterranean climatic gradient in which rainfall and winter cold experience strong variation.\\u000a Mean maximum vessel diameter, vessel density, vessel element length, xylem transverse sectional area, Huber value (xylem transverse\\u000a sectional area per leaf area unit), theoretical leaf

Pedro Villar-Salvador; Pilar Castro-Díez; Carmen Pérez-Rontomé; G. Montserrat-Martí

1997-01-01

289

Complex Numbers  

NSDL National Science Digital Library

Written by Tony R. Kuphaldt and Jason Starck, this chapter of All About Circuit's second volume on Alternating Current describes complex numbers: "In order to successfully analyze AC circuits, we need to work with mathematical objects and techniques capable of representing these multi-dimensional quantities. Here is where we need to abandon scalar numbers for something better suited: complex numbers." In addition to the introduction and credits to contributors, the chapter has seven sections: Vectors and AC waveforms, Simple vector addition, Complex vector addition, Polar and rectangular notation, Complex number arithmetic, More on AC "polarity," and Some examples with AC circuits. Each section has clear illustrations and a concise, bulleted review of what was covered at the end.

Kuphaldt, Tony R.

2008-07-15

290

Ordering numbers  

NSDL National Science Digital Library

Khan Academy Exercise bank - Ordering numbers Students are able to use the knowledge map and progress tracking tool to record and support their learning goals. Hints are provided and supporting video tutorials are identified and linked.

Khan, Sal

2011-04-01

291

Number Line  

NSDL National Science Digital Library

In this brief article the numerous uses of the number line are detailed: counting, measurement, addition, subtraction, decimals, and fractions. The article contains visual representations of the some of the concepts and links to related topics.

2012-08-27

292

[Effects of acid rain stress on Eleocarpus glabripetalus seedlings leaf chlorophyll fluorescence characteristics and growth].  

PubMed

A pot experiment was conducted to study the Eleocarpus glabripetalus seedlings leaf chlorophyll fluorescence characteristics and growth in different seasons under simulated acid rain stress (heavy, pH = 2. 5; moderate, pH = 4.0; and control, pH = 5.6). In the same treatments, the leaf relative chlorophyll content (SPAD), maximum PS II photochemical efficiency (F(v)/F(m)), actual PSII photochemical quantum yield (phi(PS II)), plant height, and stem diameter in different seasons were all in the order of October > July > April > January. In the same seasons, all the parameters were in the order of heavy acid rain > moderate acid rain > control. The interactions between different acid rain stress and seasons showed significant effects on the SPAD, F(v)/F(m), plant height, and stem diameter, but lesser effects on phi(PS II), qp and qN. PMID:20873608

Yin, Xiu-Min; Yu, Shu-Quan; Jiang, Hong; Liu, Mei-Hu

2010-06-01

293

Molecular targets of elevated (CO2) in leaves and stems of Populus deltoides: implications for future tree growth and carbon sequestration  

Microsoft Academic Search

We report the first comprehensive analysis of the effects of elevated (CO2) on gene expression in source leaf and stem sink tissues in woody plants. We have taken advantage of coppiced Populus deltoides (Bartr.) stands grown for 3 years under three different and constant elevated (CO2) in the agriforest mesocosms of Biosphere 2. Leaf area per tree was doubled by

Nathalie DruartA; Marisa Rodr ´ iguez-BueyA; Andreas Sj

294

Rotatable stem and lock  

DOEpatents

A valve stem and lock is disclosed which includes a housing surrounding a valve stem, a solenoid affixed to an interior wall of the housing, an armature affixed to the valve stem and a locking device for coupling the armature to the housing body. When the solenoid is energized, the solenoid moves away from the housing body, permitting rotation of the valve stem.

Deveney, J.E.; Sanderson, S.N.

1981-10-27

295

Rotatable stem and lock  

DOEpatents

A valve stem and lock include a housing surrounding a valve stem, a solenoid affixed to an interior wall of the housing, an armature affixed to the valve stem and a locking device for coupling the armature to the housing body. When the solenoid is energized, the solenoid moves away from the housing body, permitting rotation of the valve stem.

Deveney, Joseph E. (Albuquerque, NM) [Albuquerque, NM; Sanderson, Stephen N. (Albuquerque, NM) [Albuquerque, NM

1984-01-01

296

Stem cells in urology  

Microsoft Academic Search

The shortage of donors for organ transplantation has stimulated research on stem cells as a potential resource for cell-based therapy in all human tissues. Stem cells have been used for regenerative medicine applications in many organ systems, including the genitourinary system. The potential applications for stem cell therapy have, however, been restricted by the ethical issues associated with embryonic stem

Tamer Aboushwareb; Anthony Atala

2008-01-01

297

[Bioethical challenges of stem cell tourism].  

PubMed

Stem cells have drawn extraordinary attention from scientists and the general public due to their potential to generate effective therapies for incurable diseases. At the same time, the production of embryonic stem cells involves a serious ethical issue concerning the destruction of human embryos. Although adult stem cells and induced pluripotential cells do not pose this ethical objection, there are other bioethical challenges common to all types of stem cells related particularly to the clinical use of stem cells. Their clinical use should be based on clinical trials, and in special situations, medical innovation, both of which have particular ethical dimensions. The media has raised unfounded expectations in patients and the public about the real clinical benefits of stem cells. At the same time, the number of unregulated clinics is increasing around the world, making direct offers through Internet of unproven stem cell therapies that attract desperate patients that have not found solutions in standard medicine. This is what is called stem cells tourism. This article reviews this situation, its consequences and the need for international cooperation to establish effective regulations to prevent the exploitation of patients and to endanger the prestige of legitimate stem cell research. PMID:24448860

Ventura-Juncá, Patricio; Erices, Alejandro; Santos, Manuel J

2013-08-01

298

Stem cell therapy without the cells  

PubMed Central

As an example of the burgeoning importance of stem cell therapy, this past month the California Institute for Regenerative Medicine (CIRM) has approved $70 million to create a new network of stem cell clinical trial centers. Much work in the last decade has been devoted to developing the use of autologous and allogeneic adult stem cell transplants to treat a number of conditions, including heart attack, dementia, wounds, and immune system-related diseases. The standard model teaches us that adult stem cells exists throughout most of the body and provide a means to regenerate and repair most tissues through replication and differentiation. Although we have often witnessed the medical cart placed in front of the scientific horse in the development of stem cell therapies outside of academic circles, great strides have been made, such as the use of purified stem cells1 instead of whole bone marrow transplants in cancer patients, where physicians avoid re-injecting the patients with their own cancer cells.2 We most often think of stem cell therapy acting to regenerate tissue through replication and then differentiation, but recent studies point to the dramatic effects adult stem cells exert in the repair of various tissues through the release of paracrine and autocrine substances, and not simply through differentiation. Indeed, up to 80% of the therapeutic effect of adult stem cells has been shown to be through paracrine mediated actions.3 That is, the collected types of molecules released by the stem cells, called the secretome, or stem cell released molecules (SRM), number in the 100s, including proteins, microRNA, growth factors, antioxidants, proteasomes, and exosomes, and target a multitude of biological pathways through paracrine actions. The composition of the different molecule types in SRM is state dependent, and varies with cell type and conditions such as age and environment.

Maguire, Greg

2013-01-01

299

Stem cell therapy without the cells.  

PubMed

As an example of the burgeoning importance of stem cell therapy, this past month the California Institute for Regenerative Medicine (CIRM) has approved $70 million to create a new network of stem cell clinical trial centers. Much work in the last decade has been devoted to developing the use of autologous and allogeneic adult stem cell transplants to treat a number of conditions, including heart attack, dementia, wounds, and immune system-related diseases. The standard model teaches us that adult stem cells exists throughout most of the body and provide a means to regenerate and repair most tissues through replication and differentiation. Although we have often witnessed the medical cart placed in front of the scientific horse in the development of stem cell therapies outside of academic circles, great strides have been made, such as the use of purified stem cells(1) instead of whole bone marrow transplants in cancer patients, where physicians avoid re-injecting the patients with their own cancer cells.(2) We most often think of stem cell therapy acting to regenerate tissue through replication and then differentiation, but recent studies point to the dramatic effects adult stem cells exert in the repair of various tissues through the release of paracrine and autocrine substances, and not simply through differentiation. Indeed, up to 80% of the therapeutic effect of adult stem cells has been shown to be through paracrine mediated actions.(3) That is, the collected types of molecules released by the stem cells, called the secretome, or stem cell released molecules (SRM), number in the 100s, including proteins, microRNA, growth factors, antioxidants, proteasomes, and exosomes, and target a multitude of biological pathways through paracrine actions. The composition of the different molecule types in SRM is state dependent, and varies with cell type and conditions such as age and environment. PMID:24567776

Maguire, Greg

2013-11-01

300

Cell reprogramming: expectations and challenges for chemistry in stem cell biology and regenerative medicine  

Microsoft Academic Search

The possibility of reprogramming adult somatic cells into pluripotent stem cells (iPSCs) has generated a renewed interest into stem cell research and promises to overcome several key issues, including the ethical concerns of using human embryonic stem cells and the difficulty of obtaining large numbers of adult stem cells (Belmonte et al., Nat Rev Genet, 2009). This approach is also

L Anastasia; G Pelissero; B Venerando; G Tettamanti

2010-01-01

301

Addressing the STEM Teacher Shortage in American Schools: Ways to Recruit and Retain Effective STEM Teachers  

ERIC Educational Resources Information Center

The shortage of certified science, technology, engineering, and mathematics (STEM) teachers is of concern throughout the United States because of significant numbers needed over the next over the next 10 years. Addressing this issue in education, this study examined the experiences of three new STEM teachers who entered teaching through different…

Hutchison, Laveria F.

2012-01-01

302

A cross-species transcriptomics approach to identify genes involved in leaf development  

PubMed Central

Background We have made use of publicly available gene expression data to identify transcription factors and transcriptional modules (regulons) associated with leaf development in Populus. Different tissue types were compared to identify genes informative in the discrimination of leaf and non-leaf tissues. Transcriptional modules within this set of genes were identified in a much wider set of microarray data collected from leaves in a number of developmental, biotic, abiotic and transgenic experiments. Results Transcription factors that were over represented in leaf EST libraries and that were useful for discriminating leaves from other tissues were identified, revealing that the C2C2-YABBY, CCAAT-HAP3 and 5, MYB, and ZF-HD families are particularly important in leaves. The expression of transcriptional modules and transcription factors was examined across a number of experiments to select those that were particularly active during the early stages of leaf development. Two transcription factors were found to collocate to previously published Quantitative Trait Loci (QTL) for leaf length. We also found that miRNA family 396 may be important in the control of leaf development, with three members of the family collocating with clusters of leaf development QTL. Conclusion This work provides a set of candidate genes involved in the control and processes of leaf development. This resource can be used for a wide variety of purposes such as informing the selection of candidate genes for association mapping or for the selection of targets for reverse genetics studies to further understanding of the genetic control of leaf size and shape.

Street, Nathaniel Robert; Sjodin, Andreas; Bylesjo, Max; Gustafsson, Petter; Trygg, Johan; Jansson, Stefan

2008-01-01

303

Characterization of olfactory stem cells.  

PubMed

There is worldwide enthusiasm for the prospect of some kind of cellular transplant therapy for repair of failing organs. The olfactory mucosa of a patient's nose is easily biopsied to provide a ready source of multipotent cells. In this article we address practical issues pertinent to using olfactory neural stem cells for tissue repair. These cells are emerging as potentially most significant candidates for human tissue repair strategies. Previously we have shown that stem cells from olfactory mucosa are multipotent. As well, we have recently published three potential clinical applications. Their expression of dopaminergic markers in vitro and in a Parkinson's rat transplant model has been demonstrated. Their conversion to chondrogenic phenotype in vitro and in vivo has also been described, as has their transplant into a rat model of cardiac infarction. Here we examine in detail the biology of the olfactory neural stem cell using the rat as our animal model cell source. We establish its presence by examining self-renewal capacity and for phenotypic acquisition in inductive circumstances. We determine its frequency within the cell population and show that our culture system selects for this putative stem cell. Our studies demonstrate that adult olfactory stem cells, when transplanted into an environmental niche different from that of their origin, are able to demonstrate multipotency by acquiring the phenotype of the resident cells. We investigate how immediate the instruction need be. We test the hypothesis that olfactory neurospheres contain stem cells whose capacity for differentiation is triggered by signals of the immediate environmental niche. Significantly, of importance to any tissue regeneration endeavor, stem cell numbers were shown to be enriched by our culture methods. This was confirmed whether measured by sphere-forming capacity or differentiation response rate. PMID:21535908

Wetzig, Andrew; Mackay-Sim, Alan; Murrell, Wayne

2011-01-01

304

Hematopoietic stem cells in Drosophila.  

PubMed

The Drosophila lymph gland, the source of adult hemocytes, is established by mid-embryogenesis. During larval stages, a pool of pluripotent hemocyte precursors differentiate into hemocytes that are released into circulation upon metamorphosis or in response to immune challenge. This process is controlled by the posterior signaling center (PSC), which is reminiscent of the vertebrate hematopoietic stem cell niche. Using lineage analysis, we identified bona fide hematopoietic stem cells (HSCs) in the lymph glands of embryos and young larvae, which give rise to a hematopoietic lineage. These lymph glands also contain pluripotent precursor cells that undergo a limited number of mitotic divisions and differentiate. We further find that the conserved factor Zfrp8/PDCD2 is essential for the maintenance of the HSCs, but dispensable for their daughter cells, the pluripotent precursors. Zfrp8/PDCD2 is likely to have similar functions in hematopoietic stem cell maintenance in vertebrates. PMID:20023157

Minakhina, Svetlana; Steward, Ruth

2010-01-01

305

Leaf Extraction and Analysis Framework Graphical User Interface: Segmenting and Analyzing the Structure of Leaf Veins and Areoles1[W][OA  

PubMed Central

Interest in the structure and function of physical biological networks has spurred the development of a number of theoretical models that predict optimal network structures across a broad array of taxonomic groups, from mammals to plants. In many cases, direct tests of predicted network structure are impossible given the lack of suitable empirical methods to quantify physical network geometry with sufficient scope and resolution. There is a long history of empirical methods to quantify the network structure of plants, from roots, to xylem networks in shoots and within leaves. However, with few exceptions, current methods emphasize the analysis of portions of, rather than entire networks. Here, we introduce the Leaf Extraction and Analysis Framework Graphical User Interface (LEAF GUI), a user-assisted software tool that facilitates improved empirical understanding of leaf network structure. LEAF GUI takes images of leaves where veins have been enhanced relative to the background, and following a series of interactive thresholding and cleaning steps, returns a suite of statistics and information on the structure of leaf venation networks and areoles. Metrics include the dimensions, position, and connectivity of all network veins, and the dimensions, shape, and position of the areoles they surround. Available for free download, the LEAF GUI software promises to facilitate improved understanding of the adaptive and ecological significance of leaf vein network structure.

Price, Charles A.; Symonova, Olga; Mileyko, Yuriy; Hilley, Troy; Weitz, Joshua S.

2011-01-01

306

Molecular diversity of Cotton leaf curl Gezira virus isolates and their satellite DNAs associated with okra leaf curl disease in Burkina Faso  

PubMed Central

Okra leaf curl disease (OLCD) is a major constraint on okra (Abelmoschus esculentus) production and is widespread in Africa. Using a large number of samples representative of the major growing regions in Burkina Faso (BF), we show that the disease is associated with a monopartite begomovirus and satellite DNA complexes. Twenty-three complete genomic sequences of Cotton leaf curl Gezira virus (CLCuGV) isolates associated with OLCD, sharing 95 to 99% nucleotide identity, were cloned and sequenced. Six betasatellite and four alphasatellite (DNA-1) molecules were also characterized. The six isolates of betasatellite associated with CLCuGV isolates correspond to Cotton leaf curl Gezira betasatellite (CLCuGB) (88 to 98% nucleotide identity). One isolate of alphasatellite is a variant of Cotton leaf curl Gezira alphasatellite (CLCuGA) (89% nucleotide identity), whereas the three others isolates appear to correspond to a new species of alphasatellite (CLCuGA most similar sequence present 52 to 60% nucleotide identity), provisionally named Okra leaf curl Burkina Faso alphasatellite (OLCBFA). Recombination analysis of the viruses demonstrated the interspecies recombinant origin of all CLCuGV isolates, with parents being close to Hollyhock leaf crumple virus (AY036009) and Tomato leaf curl Diana virus (AM701765). Combined with the presence of satellites DNA, these results highlight the complexity of begomoviruses associated with OLCD.

2010-01-01

307

Mutants in Arabidopsis thaliana Altered in Epicuticular Wax and Leaf Morphology.  

PubMed Central

We report eight new mutants in Arabidopsis thaliana possessing altered leaf morphology and epicuticular wax. These were isolated from a T-DNA-mutagenized population using a visual screen for altered leaf reflectance, i.e. increased glaucousness or glossiness. The mutants were placed into three distinct classes based on alterations in overall plant morphology: knobhead (knb), bicentifolia (bcf), and wax. The four knb mutants formed callus-like growths in the axillary region of the rosette leaves and apical meristem, the two bcf mutants produced hundreds of narrow leaves, and the two wax mutants had leaves and stems that were more glossy than wild type and organs that fused during early development. Leaves of knb and bcf were more glaucous and abnormally shaped than wild type. Epicuticular wax crystals over knb and bcf leaf surfaces (where none were present on wild type) likely contributed to their more glaucous appearance. In contrast, the glossy appearance of the wax mutants was associated with a reduced epicuticular wax load on both leaves and stems. One representative from each phenotypic class was selected for detailed analyses of epicuticular wax chemistry. All three lines, knb1, bcf1, and wax1, had dramatic alterations in the total amounts and relative proportions of their leaf epicuticular wax constituents.

Jenks, M. A.; Rashotte, A. M.; Tuttle, H. A.; Feldmann, K. A.

1996-01-01

308

Hormonal regulation of leaf senescence in Lilium.  

PubMed

In addition to floral senescence and longevity, the control of leaf senescence is a major factor determining the quality of several cut flowers, including Lilium, in the commercial market. To better understand the physiological process underlying leaf senescence in this species, we evaluated: (i) endogenous variation in the levels of phytohormones during leaf senescence, (ii) the effects of leaf darkening in senescence and associated changes in phytohormones, and (iii) the effects of spray applications of abscisic acid (ABA) and pyrabactin on leaf senescence. Results showed that while gibberellin 4 (GA(4)) and salicylic acid (SA) contents decreased, that of ABA increased during the progression of leaf senescence. However, dark-induced senescence increased ABA levels, but did not affect GA(4) and SA levels, which appeared to correlate more with changes in air temperature and/or photoperiod than with the induction of leaf senescence. Furthermore, spray applications of pyrabactin delayed the progression of leaf senescence in cut flowers. Thus, we conclude that (i) ABA plays a major role in the regulation of leaf senescence in Lilium, (ii) darkness promotes leaf senescence and increases ABA levels, and (iii) exogenous applications of pyrabactin inhibit leaf senescence in Lilium, therefore suggesting that it acts as an antagonist of ABA in senescing leaves of cut lily flowers. PMID:22854182

Arrom, Laia; Munné-Bosch, Sergi

2012-10-15

309

Number Cruncher  

NSDL National Science Digital Library

Similar to the original "Function Machine" but lists input and output in a table and will not let the user attempt to guess the rule without having at least two data points. Number Cruncher is one of the Interactivate assessment explorers.

310

Number Patterns  

NSDL National Science Digital Library

In this lesson, learners are challenged to discover the relationship among six numbers. The objective of this activity is to engage learners in a problem-solving situation in which they practice aspects of the process of science. Learners can use an included Science Flowchart to chart their scientific experience. This lesson serves as a good introduction to the nature of scientific inquiry.

Scotchmoor, Judy

2010-01-01

311

Numbers Sense  

ERIC Educational Resources Information Center

This article reports on work undertaken by schools as part of Qualifications and Curriculum Authority's (QCA's) "Engaging mathematics for all learners" project. The goal was to use in the classroom, materials and approaches from a Royal Institution (Ri) Year 10 master-class, "Number Sense", which was inspired by examples from Michael Blastland and…

Kathotia, Vinay

2009-01-01

312

Microplate quantification of plant leaf superoxide dismutases.  

PubMed

Superoxide dismutases (SODs) catalyze the dismutation of superoxide radicals in a broad range of organisms, including plants. Quantification of SOD activity in crude plant extracts has been problematic due to the presence of compounds that interfere with the dose-response of the assay. Although strategies exist to partially purify SODs from plant extracts, the requirement for purification limits the rapidity and practical number of assays that can be conducted. In this article, we describe modification of a procedure using o-dianisidine as substrate that permits relatively rapid quantification of SOD activity in crude leaf extracts in a microplate format. The method employs the use of a commercial apparatus that permits lysis of 12 tissue samples at once and the use of Pipes buffer to reduce interference from compounds present in crude leaf extracts. The assay provided a linear response from 1 to 50 units of SOD. The utility of the assay was demonstrated using tissue extracts prepared from a group of taxonomically diverse plants. Reaction rates with tissue extracts from two grasses were linear for at least 60 min. Tissues of certain species contained interfering compounds, most of which could be removed by ultrafiltration. The presence of plant catalases, peroxidases, and ascorbate in physiological quantities did not interfere with the assay. This approach provides a means to quantify SOD activity in relatively large numbers of plant samples provided that the possibility for the presence of interfering compounds is considered. The presence of interfering compounds in certain plant tissues necessitates caution in interpreting the effects of plant stresses on SOD. PMID:15325300

Banowetz, Gary M; Dierksen, Karen P; Azevedo, Mark D; Stout, Richard

2004-09-15

313

Effect of light and gibberellic acid on cell division in the first foliage leaf of durum wheat ( Triticum durum Desf.)  

Microsoft Academic Search

The present paper is part of a research program which aims at a quantitative analysis of the effects of light and gibberellic acid (GA3) on growth of the first foliage leaf in durum wheat (Triticum durum Desf.). Since leaf growth is the combined result of the increase in cell number (cell division) and cell enlargement, the influence of light and

S. Baroncelli; A. Cavallini; B. Lercari; P. G. Cionini; F. D'Amato

1988-01-01

314

[Sensitivity study of a revised leaf photochemical reflectance index (PRI)].  

PubMed

Photochemical reflectance index (PRI) defined as a normalized difference index using two narrow reflectance bands at 531 and 570 nm that are closely related to xanthophyll cycle pigment content has been successfully used to estimate leaf photosynthetic light use efficiency (LUE) across species which vary in water content and nitrogen concentration. Previous research demonstrated that a consistent relationship could be established between PRI and LUE calculated from gas exchange measurements at the leaf, small canopy, and full forest or crop canopy scales. However, a number of problems, such as the saturation of PRI when LUE exceeds 0.03 mol CO2 mol(-1) PPED (photosynthetic photon flux density) and disjunctive relationships of PRI and LUE in seasonal changes, still existed and need to be handled in order to evaluate LUE more accurately. A sensitivity study of a revised PRI with four leaf parameters was performed based on PROSPECT model in the present article to study the effects of different biochemical concentrations on leaf SR-PRI (simple ratio PRI). Sensitivity study proved that leaf SR-PRI is more sensitive to leaf mesophyll structure parameter (N) and chlorophyll a + b content (c(ab)) than parameters of dry matter content (c(m)) and equivalent water thickness (c(w)), indicating that leaf mesophyll structure parameter (N) and chlorophyll a + b content (c(ab)) should be especially considered when acquiring leaf SR-PRI. And changes in the two parameters would cause large variation in SR-PRI which would reduce the precision for estimating light use efficiency. Validation study of SR-PRI was carried out in the analysis and the results proved that SR-PRI can also be a feasible index of estimating LUE for four species of plants with correlation coefficients better than that of PRI and LUE. The advantage of SR-PRI compared to PRI is its much clearer physical meaning and its sensitivity to the changes in reflectance at 531 nm which serves as a core parameter to evaluate light use efficiency. PMID:19093551

Wu, Chao-yang; Niu, Zheng; Tang, Quan

2008-09-01

315

Salinity effects on leaf anatomy  

Microsoft Academic Search

Increasing salinity led to substantially higher ratios of mesophyll surface area to leaf area (A\\/sup mes\\/\\/A) for Phaseolus vulgaris and Gossypium hirsutum and a smaller increase for Atriplex patula, a salt-tolerant species. The increase in internal surface for COâ absorption did not lead to higher COâ uptake rates, since the COâ resistance expressed on the basis of mesophyll cell wall

D. J. Longstreth; P. S. Nobel

1979-01-01

316

Leaf Optical Properties in Higher Plants: Linking Spectral Characteristics with Plant Stress  

NASA Technical Reports Server (NTRS)

A number of studies have addressed responses of leaf spectral reflectance, transmittance, or absorptance to physiological stress. Stressors included dehydration, ozone, herbicides, disease, insufficient mycorrhizae and N fertilization, flooding and insects. Species included conifers, grasses, and broadleaved trees. Increased reflectance with maximum responses near 700 nm wavelength occurred in all cases. Varying the chlorophyll content in leaves or pigment extracts can simulate this effect. Thus, common optical responses to stress result from decreases in leaf chlorophyll contents or the capacity of chloroplasts to absorb light. Leaf optic can be quite sensitive to any stressor that alters soil-plant-atmosphere processes.

Carter, Gregory A.; Knapp, Alan K.

1999-01-01

317

Table Numbers  

NSDL National Science Digital Library

This interactive applet helps students develop fluency with multiplication facts. Users chose a factor from among the digits 1-9, each of which is associated with a mnemonic graphic. The applet then displays three numbers and the user selects the one which is a multiple of the chosen factor. The player must respond correctly to ten examples to complete a round. A one-point penalty for selecting an incorrect product discourages guessing. The few words that are displayed are in Dutch.

2008-01-01

318

M yocyte and myogenic stem cell transplantation in the heart  

Microsoft Academic Search

Cellular transplantation is emerging as a potential mechanism with which to augment myocyte number in diseased hearts. To date a number of cell types have been shown to successfully engraft into the myocardium, including fetal, neonatal, and embryonic stem cell-derived cardiomyocytes, skeletal myoblasts, and stem cells with apparent cardiomyogenic potential. Here we provide a review of studies wherein myocytes or

Joshua D. Dowell; Michael Rubart; Kishore B. S. Pasumarthi; Mark H. Soonpaa; Loren J. Field

319

Canalization-based vein formation in a growing leaf.  

PubMed

Vein formation is an important process in plant leaf development. The phytohormone auxin is known as the most important molecule for the control of venation patterning; and the canalization model, in which cells experiencing higher auxin flux differentiate into specific cells for auxin transportation, is widely accepted. To date, several mathematical models based on the canalization hypothesis have been proposed that have succeeded in reproducing vein patterns similar to those observed in actual leaves. However, most previous studies focused on patterning in fixed domains, and, in a few exceptional studies, limited tissue growth - such as cell proliferation at leaf margins and small deformations without large changes in cell number - were dealt with. Considering that, in actual leaf development, venation patterning occurs in an exponentially growing tissue, whether the canalization hypothesis still applies is an important issue to be addressed. In this study, we first show through a pilot simulation that the coupling of chemical dynamics for canalization and tissue growth as independent models cannot reproduce normal venation patterning. We then examine conditions sufficient for achieving normal patterning in a growing leaf by introducing various constraints on chemical dynamics, tissue growth, and cell mechanics; in doing so, we found that auxin flux- or differentiation-dependent modification of the cell cycle and elasticity of cell edges are essential. The predictions given by our simulation study will serve as guideposts in experiments aimed at finding the key factors for achieving normal venation patterning in developing plant leaves. PMID:24632445

Lee, Sang-Woo; Feugier, Francois Gabriel; Morishita, Yoshihiro

2014-07-21

320

Hormonal changes during salinity-induced leaf senescence in tomato (Solanum lycopersicum L.).  

PubMed

Leaf senescence is one of the most limiting factors to plant productivity under salinity. Both the accumulation of specific toxic ions (e.g. Na+) and changes in leaf hormone relations are involved in the regulation of this process. Tomato plants (Solanum lycopersicum L. cv Moneymaker) were cultivated for 3 weeks under high salinity (100 mM NaCl) and leaf senescence-related parameters were studied during leaf development in relation to Na+ and K+ contents and changes in abscisic acid (ABA), cytokinins, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and the auxin indole-3-acetic acid (IAA). Na+ accumulated to a similar extent in both leaves 4 and 5 (numbering from the base of the plant) and more quickly during the third week, while concurrently K+ contents sharply decreased. However, photosystem II efficiency, measured as the F(v)/F(m) ratio, decreased from the second week of salinization in leaf 4 but only at the end of the third week in the younger leaf 5. In the prematurely senescent leaf 4, ABA content increased linearly while IAA strongly decreased with salinization time. Although zeatin (Z) levels were scarcely affected by salinity, zeatin-riboside (ZR) and the total cytokinin content (Z+ZR) progressively decreased by 50% from the imposition of the stress. ACC was the only hormonal compound that increased in leaf tissue coincident with the onset of oxidative damage and the decline in chlorophyll fluorescence, and prior to massive Na+ accumulation. Indeed, (Z+ZR) and ACC contents and their ratio (Z+ZR/ACC) were the hormonal parameters best correlated with the onset and progression of leaf senescence. The influence of different hormonal changes on salt-induced leaf senescence is discussed. PMID:18573798

Ghanem, Michel Edmond; Albacete, Alfonso; Martínez-Andújar, Cristina; Acosta, Manuel; Romero-Aranda, Remedios; Dodd, Ian C; Lutts, Stanley; Pérez-Alfocea, Francisco

2008-01-01

321

Jasmonates: Hormonal regulators or stress factors in leaf senescence?  

Microsoft Academic Search

Specific cyclopentanone compounds such as (?)-jasmonic acid (JA) and its methyl ester (JA-Me) or (+)-7-iso-jasmonic acid are\\u000a considered putative plant growth regulators for a number of reasons, including their ubiquitous occurrence in the plant kingdom,\\u000a structural specificity in physiological responses, and interaction with other phytohormones in the biological activities of\\u000a jasmonates. In this respect leaf senescence promotion is of particular

Benno Parthier

1990-01-01

322

Status of Legislation Concerning 911, The Emergency Telephone Number, With a Suggested 911 Emergency Telephone Number, Act with Supporting Analysis.  

National Technical Information Service (NTIS)

Official interest in establishing a universal emergency telephone number stems primarily from a 1967 recommendation of the President's Commission on Law Enforcement and the Administration of Justice that a 'single number should be established' for reporti...

1979-01-01

323

Antiviral Ability of Kalanchoe gracilis Leaf Extract against Enterovirus 71 and Coxsackievirus A16.  

PubMed

Pandemic infection or reemergence of Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) occurs in tropical and subtropical regions, being associated with hand-foot-and-mouth disease, herpangina, aseptic meningitis, brain stem encephalitis, pulmonary edema, and paralysis. However, effective therapeutic drugs against EV71 and CVA16 are rare. Kalanchoe gracilis (L.) DC is used for the treatment of injuries, pain, and inflammation. This study investigated antiviral effects of K. gracilis leaf extract on EV71 and CVA16 replications. HPLC analysis with a C-18 reverse phase column showed fingerprint profiles of K. gracilis leaf extract had 15 chromatographic peaks. UV/vis absorption spectra revealed peaks 5, 12, and 15 as ferulic acid, quercetin, and kaempferol, respectively. K. gracilis leaf extract showed little cytotoxicity, but exhibited concentration-dependent antiviral activities including cytopathic effect, plaque, and virus yield reductions. K. gracilis leaf extract was shown to be more potent in antiviral activity than ferulic acid, quercetin, and kaempferol, significantly inhibiting in vitro replication of EV71 (IC(50) = 35.88??g/mL) and CVA16 (IC(50) = 42.91??g/mL). Moreover, K. gracilis leaf extract is a safe antienteroviral agent with the inactivation of viral 2A protease and reduction of IL-6 and RANTES expressions. PMID:22666293

Wang, Ching-Ying; Huang, Shun-Chueh; Zhang, Yongjun; Lai, Zhen-Rung; Kung, Szu-Hao; Chang, Yuan-Shiun; Lin, Cheng-Wen

2012-01-01

324

Resistance to Melampsora larici-epitea leaf rust in Salix : analyses of quantitative trait loci  

Microsoft Academic Search

Quantitative resistance ofSalix toMelampsora larici-epitea leaf rust was studied in 2Salix mapping populations. One population was a backcross between aS. schwerinii ×S. viminalis hybrid andS. viminalis, and the other was an F2 population betweenS. viminalis andS. dasyclados. A leaf disc bioassay was used to study the components of quantitative resistance (latent period, uredinia number, and uredinia\\u000a size) to 3 isolates

Ann-Christin Rönnberg-Wästljung; Berit Samils; Vasilios Tsarouhas; Urban Gullberg

2008-01-01

325

On using the dosimetric leaf gap to model the rounded leaf ends in VMAT/RapidArc plans.  

PubMed

Partial transmission through rounded leaf ends of Varian multileaf collimators (MLC) is accounted for with a parameter called the dosimetric leaf gap (DLG). Verification of the value of the DLG is needed when the dose delivery is accompanied by gantry rotation in VMAT plans. We compared the doses measured with GAFCHROMIC film and an ionization chamber to treatment planning system (TPS) calculations to identify the optimum values of the DLG in clinical plans of the whole brain with metastases transferred to a phantom. We noticed the absence of a single value of the DLG that properly models all VMAT plans in our cohort (the optimum DLG varied between 0.93 ± 0.15 mm and 2.2 ± 0.2 mm). The former value is considerably different from the optimum DLG in sliding window plans (about 2.0 mm) that approximate IMRT plans. We further found that a single-value DLG model cannot accurately reproduce the measured dose profile even of a uniform static slit at a fixed gantry, which is the simplest MLC-delimited field. The calculation overestimates the measurement in the proximal penumbra, while it underestimates in the distal penumbra. This prompted us to expand the DLG parameter from a plan-specific number to a mathematical concept of the DLG being a function of the distance in the beam's eye view (BEV) between the dose point and the leaf ends. Such function compensates for the difference between the penumbras in a beam delimited with a rounded leaf MLC and delimited with solid jaws. Utilization of this concept allowed us generating a pair of step-and-shoot MLC plans for which we could qualitatively predict the value of the DLG providing best match to ionization chamber measurements. The plan for which the leafs stayed predominantly at positions requiring low values of the DLG (as seen in the profiles of 1D slits) yielded the combined DLG of 1.1 ± 0.2 mm, while the plan with leafs staying at positions requiring larger values of the DLG yielded the DLG 2.4 ± 0.2 mm. Considering the DLG to be a function of the distance (in BEV) between the dose point and the leaf ends allowed us to provide an explanation as to why conventional single-number DLG is plan-specific in VMAT plans. PMID:24710433

Szpala, Stanislaw; Cao, Fred; Kohli, Kirpal

2014-01-01

326

Impact of decomposing Cinnamomum septentrionale leaf litter on the growth of Eucalyptus grandis saplings.  

PubMed

A pot experiment was performed to study the impact of decomposing Cinnamomum septentrionale leaf litter on the growth of Eucalyptus grandis saplings. The experimental design scheme was 0 (CK), 40 (A1), 80 (A2) and 120 g pot(-1) (A3) of E. grandis leaves, and changes in the volatile oil chemical composition during litter decomposition were assessed in the present study. The results showed that C. septentrionale leaf litter inhibited the growth of E. grandis saplings, as determined by the height, basal diameter and chlorophyll content, after 69 d (T1). Five months after transplantation (T2), the height growth rate of the E. grandis saplings increased and then gradually reduced (A1: 40 g pot(-1) > A2: 80 g pot(-1) > A3: 120 g pot(-1) > CK: 0 g pot(-1)). After eleven months (T3), the variations in the height and basal diameter were the same as observed at T2, and the inhibition on leaf, branch, root and stem biomass increased with increasing leaf litter content. Gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile compound composition. The results indicated that the C. septentrionale original leaf litter (S1) contained thirty-one volatile compounds, but the treated leaf litter S2 (which was mixed with soil for eleven months to simultaneously plant E. grandis saplings) only possessed fourteen volatile compounds, releasing many secondary metabolites in the soil during decomposition. Most of the volatile compounds were alcohols, monoterpenoids, sesquiterpenes, alkanes, alkene, esters and ketones. Most of the allelochemicals of C. septentrionale might be released during the initial decomposing process, inhibiting the growth of other plants, whereas some nutrients might be released later, promoting the height growth of plants. In conclusion, decomposing C. septentrionale leaf litter release of many allelochemicals in the soil that significantly inhibit the growth of E. grandis. PMID:23835358

Huang, Weiwei; Hu, Tingxing; Chen, Hong; Wang, Qian; Hu, Hongling; Tu, Lihua; Jing, Liao

2013-09-01

327

Effects of water stress on irradiance acclimation of leaf traits in almond trees.  

PubMed

Photosynthetic acclimation to highly variable local irradiance within the tree crown plays a primary role in determining tree carbon uptake. This study explores the plasticity of leaf structural and physiological traits in response to the interactive effects of ontogeny, water stress and irradiance in adult almond trees that have been subjected to three water regimes (full irrigation, deficit irrigation and rain-fed) for a 3-year period (2006-08) in a semiarid climate. Leaf structural (dry mass per unit area, N and chlorophyll content) and photosynthetic (maximum net CO(2) assimilation, A(max), maximum stomatal conductance, g(s,max), and mesophyll conductance, g(m)) traits and stem-to-leaf hydraulic conductance (K(s-l)) were determined throughout the 2008 growing season in leaves of outer south-facing (S-leaves) and inner northwest-facing (NW-leaves) shoots. Leaf plasticity was quantified by means of an exposure adjustment coefficient (?=1-X(NW)/X(S)) for each trait (X) of S- and NW-leaves. Photosynthetic traits and K(s-l) exhibited higher irradiance-elicited plasticity (higher ?) than structural traits in all treatments, with the highest and lowest plasticity being observed in the fully irrigated and rain-fed trees, respectively. Our results suggest that water stress modulates the irradiance-elicited plasticity of almond leaves through changes in crown architecture. Such changes lead to a more even distribution of within-crown irradiance, and hence of the photosynthetic capacity, as water stress intensifies. Ontogeny drove seasonal changes only in the ? of area- and mass-based N content and mass-based chlorophyll content, while no leaf age-dependent effect was observed on ? as regards the physiological traits. Our results also indicate that the irradiance-elicited plasticity of A(max) is mainly driven by changes in leaf dry mass per unit area, in g(m) and, most likely, in the partitioning of the leaf N content. PMID:22440881

Egea, Gregorio; González-Real, María M; Baille, Alain; Nortes, Pedro A; Conesa, María R; Ruiz-Salleres, Isabel

2012-04-01

328

Ontogenetic changes in leaf phenology of two co-occurring Mediterranean oaks differing in leaf life span  

Microsoft Academic Search

Large differences in leaf physiology and morphology between ontogenetic stages of a single woody species have often been observed.\\u000a Far less attention, however, has been devoted to studying the ontogenetic changes observed in leaf phenology patterns, despite\\u000a the relevance of leaf phenology in determining the leaf carbon balance and leaf and plant mortality. Leaf emergence patterns\\u000a and leaf longevity were

Sonia Mediavilla; Alfonso Escudero

2009-01-01

329

Isolation and Enrichment of Stem Cells  

NASA Astrophysics Data System (ADS)

Stem cells have the potential to revolutionize tissue regeneration and engineering. Both general types of stem cells, those with pluripotent differentiation potential as well as those with multipotent differentiation potential, are of equal interest. They are important tools to further understanding of general cellular processes, to refine industrial applications for drug target discovery and predictive toxicology, and to gain more insights into their potential for tissue regeneration. This chapter provides an overview of existing sorting technologies and protocols, outlines the phenotypic characteristics of a number of different stem cells, and summarizes their potential clinical applications.

Bosio, Andreas; Huppert, Volker; Donath, Susan; Hennemann, Petra; Malchow, Michaela; Heinlein, Uwe A. O.

330

The Effect of Nitrogen Fertilization and Leaf-Harvest on the Root and Leaf Yield of Lovage  

Microsoft Academic Search

The effect of various amounts of nitrogen fertilizer (0, 15, 30, 45, 75, 120 kg\\/ha N) and the number of leaf harvests on the quality and quantity of lovage (Levisticum officinale Koch) was studied in a two-year-old stand in Puumala, South-Finland in 1987. As nitrogen fertilization increased fresh root yield increased from 115 to 213 kg\\/100 m. The optimum N-level,

B. Galambosi; Zs. Szebeni-Galambosi

1992-01-01

331

Leaf wetness within a lily canopy  

NASA Astrophysics Data System (ADS)

A wetness duration experiment was carried out within a lily field situated adjacent to coastal dunes in the Netherlands. A within-canopy model was applied to simulate leaf wetness in three layers, with equal leaf area indices, within the canopy. This simulation model is an extension of an existing model. It appeared that in most cases leaf wetness started in the uppermost layer followed by the middle and bottom layer, respectively. The same occurred during the early morning drying process. Just after sunrise the upper layer started to dry, followed by the middle and bottom layer, respectively. The longest leaf wetness duration occurred in the bottom layer. The calculated leaf wetness durations were within 10 minutes of the results obtained using a leaf wetness sensor.

Jacobs, Adrie F. G.; Heusinkveld, Bert G.; Klok, Elisabeth J.

2005-09-01

332

Number 8  

NASA Technical Reports Server (NTRS)

29 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a spotted, high latitude plain, south of the Argyre basin. When the image was received from Mars by the MOC operations team, they noticed -- with a sense of humor -- the number '8' on this martian surface. The '8' is located at the center-right and is formed by the rims of two old impact craters that have been eroded and partly-filled and partly-buried beneath the surface.

Location near: 68.6oS, 38.4oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

333

Stem Cells in Prostate.  

National Technical Information Service (NTIS)

This project aims to identify adult prostate stem cells, using tissue recombination techniques. To date, we have initiated studies utilizing mouse and human embryonic stem (ES) cells as outlined in the original statement of work. We have made progress tow...

G. Risbridger

2004-01-01

334

Neurological Complications of Hematopoietic Stem Cell Transplantation  

Microsoft Academic Search

Complications following hematopoietic stem cell transplantation have long been recognized. The causes are numerous, including\\u000a chemoradiotoxicity, medication toxicity, metabolic abnormalities, organ failure, graft versus host disease, infection, pancytopenia,\\u000a and platelet dysfunction. This chapter summarizes the disorders affecting the nervous system associated with hematopoietic\\u000a stem cell transplantation. As the number of transplants performed annually increases, potential neurologic complications are\\u000a being seen

Eudocia Quant; Patrick Y. Wen

335

STEM Club Participation and STEM Schooling Outcomes  

ERIC Educational Resources Information Center

To develop a more robust understanding of the relationship between non-formal, school-based STEM activities and students' success and persistence in STEM fields, this study evaluates how math club participation influences math GPA and how science club participation influences science GPA. Additionally, this study evaluates how math or science…

Gottfried, Michael A.; Williams, Darryl N.

2013-01-01

336

Multipotent somatic stem cells contribute to the stem cell niche in the Drosophila testis.  

PubMed

Adult stem cells reside in specialized microenvironments, or niches, that have an important role in regulating stem cell behaviour. Therefore, tight control of niche number, size and function is necessary to ensure the proper balance between stem cells and progenitor cells available for tissue homeostasis and wound repair. The stem cell niche in the Drosophila male gonad is located at the tip of the testis where germline and somatic stem cells surround the apical hub, a cluster of approximately 10-15 somatic cells that is required for stem cell self-renewal and maintenance. Here we show that somatic stem cells in the Drosophila testis contribute to both the apical hub and the somatic cyst cell lineage. The Drosophila orthologue of epithelial cadherin (DE-cadherin) is required for somatic stem cell maintenance and, consequently, the apical hub. Furthermore, our data indicate that the transcriptional repressor escargot regulates the ability of somatic cells to assume and/or maintain hub cell identity. These data highlight the dynamic relationship between stem cells and the niche and provide insight into genetic programmes that regulate niche size and function to support normal tissue homeostasis and organ regeneration throughout life. PMID:18641633

Voog, Justin; D'Alterio, Cecilia; Jones, D Leanne

2008-08-28

337

Hematopoietic Stem Cell Transplantation  

Microsoft Academic Search

\\u000a The purpose of hematopoietic stem cell transplantation (HSCT) is to replace diseased, damaged, or absent hematopoietic stem\\u000a cells (HSCs) with healthy HSCs. In general, allogeneic transplants are used when the hematopoietic stem cells are diseased\\u000a (e.g., leukemia), damaged (e.g., sickle cell disease), or absent (e.g., severe immunodeficiency disease). Autologous transplants\\u000a are used to provide stem cell rescue after higher doses

Robbie Norville; Deborah Tomlinson

338

Tumor stem cells  

Microsoft Academic Search

Stem cells possess two basic characteristics: they are able to renew themselves and to develop into different cell types.\\u000a The link between normal stem cells and tumor cells could be examined in three aspects: what are the differences and similarities\\u000a in the control of self-renewal capacity between stem cells and tumor cells; whether tumor cells arise from stem cells; do

László Kopper; Melinda Hajdú

2004-01-01

339

Umbilical Cord Stem Cells  

Microsoft Academic Search

The two most basic properties of stem cells are the capacities to self-renew and to differentiate into multiple cell or tissue\\u000a types (1–3). Generally, stem cells are categorized as one of three types: embryonic stem cells (ES), embryonic germ cells (EG), or adult\\u000a stem cells. ES cells are derived from the inner cell mass of the blastula (Fig. 1). They

Kathy E. Mitchell

340

Insect leaf mines from the Eocene Anglesea locality, Victoria, Australia  

Microsoft Academic Search

The first Tertiary leaf mines described from Australia are six mines from the Anglesea locality in Victoria. They are referable to five leaf mining taxa. Two of the mines are associated with a Lauraceae leaf. A third leaf mine is preserved in a ‘mummified’ leaf with affinities to Elaeocarpaceae. The remaining two mines are on leaves that are too poorly

A. C. Rozefelds

1988-01-01

341

7 CFR 28.467 - Leaf Grade 7.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Leaf Grade 7. 28.467 Section 28.467 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.467 Leaf Grade 7. Leaf Grade 7 is leaf which...

2009-01-01

342

Classification and quantification of leaf curvature  

PubMed Central

Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields.

Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

2010-01-01

343

Leaf traits within communities: context may affect the mapping of traits to function.  

PubMed

The leaf economics spectrum (LES) has revolutionized the way many ecologists think about quantifying plant ecological trade-offs. In particular, the LES has connected a clear functional trade-off (long-lived leaves with slow carbon capture vs. short-lived leaves with fast carbon capture) to a handful of easily measured leaf traits. Building on this work, community ecologists are now able to quickly assess species carbon-capture strategies, which may have implications for community-level patterns such as competition or succession. However, there are a number of steps in this logic that require careful examination, and a potential danger arises when interpreting leaf-trait variation among species within communities where trait relationships are weak. Using data from 22 diverse communities, we show that relationships among three common functional traits (photosynthetic rate, leaf nitrogen concentration per mass, leaf mass per area) are weak in communities with low variation in leaf life span (LLS), especially communities dominated by herbaceous or deciduous woody species. However, globally there are few LLS data sets for communities dominated by herbaceous or deciduous species, and more data are needed to confirm this pattern. The context-dependent nature of trait relationships at the community level suggests that leaf-trait variation within communities, especially those dominated by herbaceous and deciduous woody species, should be interpreted with caution. PMID:24279259

Funk, Jennifer L; Cornwell, William K

2013-09-01

344

Hair Follicle Stem Cells  

Microsoft Academic Search

The workshop on Hair Follicle Stem Cells brought together investigators who have used a variety of approaches to try to understand the biology of follicular epithelial stem cells, and the role that these cells play in regulating the hair cycle. One of the main concepts to emerge from this workshop is that follicular epithelial stem cells are multipotent, capable of

Robert M. Lavker; Tung-Tien Sun; Hideo Oshima; Yann Barrandon; Masashi Akiyama; Corinne Ferraris; Genevieve Chevalier; Bertrand Favier; Colin A. B. Jahoda; Danielle Dhouailly; Andrei A. Panteleyev; Angela M. Christiano

2003-01-01

345

STEM Workforce Pipeline.  

National Technical Information Service (NTIS)

The STEM-Works website was created to provide DoD personnel and other users around the world with access to high-quality, engaging science, technology, engineering, and mathematics (STEM) content to aid in advocating STEM content and skills to students. D...

D. M. Etter L. G. Groark

2013-01-01

346

Sugarbeet leaf spot disease (Cercospora beticola Sacc.)dagger.  

PubMed

SUMMARY Leaf spot disease caused by Cercospora beticola Sacc. is the most destructive foliar pathogen of sugarbeet worldwide. In addition to reducing yield and quality of sugarbeet, the control of leaf spot disease by extensive fungicide application incurs added costs to producers and repeatedly has selected for fungicide-tolerant C. beticola strains. The genetics and biochemistry of virulence have been examined less for C. beticola as compared with the related fungi C. nicotianae, C. kikuchii and C. zeae-maydis, fungi to which the physiology of C. beticola is often compared. C. beticola populations generally are not characterized as having race structure, although a case of race-specific resistance in sugarbeet to C. beticola has been reported. Resistance currently implemented in the field is quantitatively inherited and exhibits low to medium heritability. Taxonomy: Cercospora beticola Sacc.; Kingdom Fungi, Subdivision Deuteromycetes, Class Hyphomycetes, Order Hyphales, Genus Cercospora. Identification: Circular, brown to red delimited spots with ashen-grey centre, 0.5-6 mm diameter; dark brown to black stromata against grey background; pale brown unbranched sparingly septate conidiophores, hyaline acicular conidia, multiseptate, from 2.5 to 4 microm wide and 50-200 microm long. Host range: Propagative on Beta vulgaris and most species of Beta. Reported on members of the Chenopodiaceae and on Amaranthus. Disease symptoms: Infected leaves and petioles of B. vulgaris exhibit numerous circular leaf spots that coalesce in severe cases causing complete leaf collapse. Dark specks within a grey spot centre are characteristic for the disease. Older leaves exhibit a greater number of lesions with larger spot diameter. During the latter stage of severe epiphytotics, new leaf growth can be seen emerging from the plant surrounded by prostrate, collapsed leaves. Control: Fungicides in the benzimidazole and triazole class as well as organotin derivatives and strobilurins have successfully been used to control Cercospora leaf spot. Elevated levels of tolerance in populations of C. beticola to some of the chemicals registered for control has been documented. Partial genetic resistance also is used to reduce leaf spot disease. PMID:20565605

Weiland, John; Koch, Georg

2004-05-01

347

Salinity Effects on Leaf Anatomy  

PubMed Central

Increasing salinity led to substantially higher ratios of mesophyll surface area to leaf area (Ames/A) for Phaseolus vulgaris and Gossypium hirsutum and a smaller increase for Atriplex patula, a salt-tolerant species. The increase in internal surface for CO2 absorption did not lead to higher CO2 uptake rates, since the CO2 resistance expressed on the basis of mesophyll cell wall area (rcell) increased even more with salinity. The differences among species in the sensitivity of photosynthesis to salinity in part reflect the different Ames/A and rcell responses.

Longstreth, David J.; Nobel, Park S.

1979-01-01

348

Measurement of leaf area index using image-processing technology  

NASA Astrophysics Data System (ADS)

Leaf Area Index (LAI), as a fundamental parameter to evaluate the physiological condition of plants, was calculated by image processing based on machine vision technology. The measurement system hardware consisted primarily of the MS3100 3CCD camera, the image grabber card, a desktop computer and the acquired images were processed by Matlab and ENVI. After acquiring the 3 images by the 3CCD camera of Green, Red and NIR channels, the NIR image was considered more effective in separating the soil background for its higher contrast value. Thus, it was selected for image processing to calculate the leaf area index (LAI). The transect method was applied to obtain the threshold 50 in the binary image conversion and the soil background was thus eliminated as a result that most of its reflectance in the image was under 50. Then the 'imerode'-'imdilate' operation in the image processing box of Matlab was used to remove the left crop stem noises, including those small weeds in the binary image background. Consequently, the LAI of the acquired NIR image was calculated as 0.523 by dividing the total image pixel amount by that of the black pixels in the binary image.

Qiu, Zhengjun; Fang, Hui; Zhang, Yun; He, Yong

2005-11-01

349

Overexpression of a pectin methylesterase inhibitor in Arabidopsis thaliana leads to altered growth morphology of the stem and defective organ separation.  

PubMed

The methylesterification status of cell wall pectins, mediated through the interplay of pectin methylesterases (PMEs) and pectin methylesterase inhibitors (PMEIs), influences the biophysical properties of plant cell walls. We found that the overexpression of a PMEI gene in Arabidopsis thaliana plants caused the stems to develop twists and loops, most strongly around points on the stem where leaves or inflorescences failed to separate from the main stem. Altered elasticity of the stem, underdevelopment of the leaf cuticle, and changes in the sugar composition of the cell walls of stems were evident in the PMEI overexpression lines. We discuss the mechanisms that potentially underlie the aberrant growth phenotypes. PMID:24675171

Müller, Kerstin; Levesque-Tremblay, Gabriel; Fernandes, Anwesha; Wormit, Alexandra; Bartels, Sebastian; Usadel, Bjoern; Kermode, Allison

2013-12-01

350

Physical stem-end treatment effects on cut rose and acacia vase life and water relations  

Microsoft Academic Search

Cut Rosa hybrida cv. High & Mighty flowers and Acacia holosericea (Velvet Leaf Wattle) foliage were subjected to various physical stem-end treatments as practised by florists. Their effects on longevity (vase life) and water relations [relative fresh weight (RFW) and vase solution uptake (VSU)] were quantified. All vase water contained sodium dichloroisocyanurate (DICA) biocide. Bark removal had either positive or

Iftikhar Ahmad; Daryl C. Joyce; John D. Faragher

2011-01-01

351

29 CFR 780.516 - âPrior to the stemming process.â  

Code of Federal Regulations, 2013 CFR

...employee engaged in stemming, the removal of the midrib from the tobacco leaf (McComb v. Puerto Rico Tobacco Marketing Co-op. Ass'n., 80 F. Supp. 953, affirmed 181 F. 2d 697), or in any operations on the tobacco which are performed after...

2013-07-01

352

Hepatic stem cell niches  

PubMed Central

Stem cell niches are special microenvironments that maintain stem cells and control their behavior to ensure tissue homeostasis and regeneration throughout life. The liver has a high regenerative capacity that involves stem/progenitor cells when the proliferation of hepatocytes is impaired. In recent years progress has been made in the identification of potential hepatic stem cell niches. There is evidence that hepatic progenitor cells can originate from niches in the canals of Hering; in addition, the space of Disse may also serve as a stem cell niche during fetal hematopoiesis and constitute a niche for stellate cells in adults.

Kordes, Claus; Haussinger, Dieter

2013-01-01

353

Chloroplast Response to Low Leaf Water Potentials  

PubMed Central

Cyclic and noncyclic photophosphorylation and electron transport by photosystem 1, photosystem 2, and from water to methyl viologen (“whole chain”) were studied in chloroplasts isolated from sunflower (Helianthus annus L. var Russian Mammoth) leaves that had been desiccated to varying degrees. Electron transport showed considerable inhibition at leaf water potentials of ?9 bars when the chloroplasts were exposed to an uncoupler in vitro, and it continued to decline in activity as leaf water potentials decreased. Electron transport by photosystem 2 and coupled electron transport by photosystem 1 and the whole chain were unaffected at leaf water potentials of ?10 to ?11 bars but became progressively inhibited between leaf water potentials of ?11 and ?17 bars. A low, stable activity remained at leaf water potentials below ?17 bars. In contrast, both types of photophosphorylation were unaffected by leaf water potentials of ?10 to ?11 bars, but then ultimately became zero at leaf water potentials of ?17 bars. Although the chloroplasts isolated from the desiccated leaves were coupled at leaf water potentials of ?11 to ?12 bars, they became progressively uncoupled as leaf water potentials decreased to ?17 bars. Abscisic acid and ribonuclease had no effect on chloroplast photophosphorylation. The results are generally consistent with the idea that chloroplast activity begins to decrease at the same leaf water potentials that cause stomatal closure in sunflower leaves and that chloroplast electron transport begins to limit photosynthesis at leaf water potentials below about ?11 bars. However, it suggests that, during severe desiccation, the limitation may shift from electron transport to photophosphorylation.

Keck, R. W.; Boyer, J. S.

1974-01-01

354

The effect of experimental warming on leaf functional traits, leaf structure and leaf biochemistry in Arabidopsis thaliana  

PubMed Central

Background The leaf is an important plant organ, and how it will respond to future global warming is a question that remains unanswered. The effects of experimental warming on leaf photosynthesis and respiration acclimation has been well studied so far, but relatively little information exists on the structural and biochemical responses to warming. However, such information is very important to better understand the plant responses to global warming. Therefore, we grew Arabidopsis thaliana at the three day/night temperatures of 23/18°C (ambient temperature), 25.5/20.5°C (elevated by 2.5°C) and 28/23°C (elevated by 5°C) to simulate the middle and the upper projected warming expected within the 21st century for this purpose. Results The 28/23°C treatment significantly reduced the life span, total biomass and total weight of seeds compared with the other two temperatures. Among the three temperature regimes, the concentrations of starch, chlorophyll, and proline were the lowest at 28/23°C, whereas the total weight of seeds, concentrations of chlorophyll and proline, stomatal density (SD), stomatal conductance (gs), net CO2 assimilation rate (A) and transpiration rate (E) were the highest at 25.5/20.5°C. Furthermore, the number of chloroplasts per cell and mitochondrial size were highest at 25.5/20.5°C and lowest at 28/23°C. Conclusions The conditions whereby the temperature was increased by 2.5°C were advantageous for Arabidopsis. However, a rise of 5°C produced negative effects, suggesting that lower levels of warming may benefit plants, especially those which belong to the same functional group as Arabidopsis, whereas higher levels of warming may produce negative affects. In addition, the increase in A under moderately warm conditions may be attributed to the increase in SD, chlorophyll content, and number of chloroplasts. Furthermore, starch accumulation in chloroplasts may be the main factor influencing chloroplast ultrastructure, and elevated temperature regulates plant respiration by probably affecting mitochondrial size. Finally, high SOD and CAT activities may enable plants grown at elevated temperatures to exhibit relatively high tolerance to temperature stress, thus alleviating the harmful effects of superoxide anion radicals and hydrogen peroxide.

2011-01-01

355

Segmentation and leaf sequencing for intensity modulated arc therapy  

SciTech Connect

A common method in generating intensity modulated radiation therapy (IMRT) plans consists of a three step process: an optimized fluence intensity map (IM) for each beam is generated via inverse planning, this IM is then segmented into discrete levels, and finally, the segmented map is translated into a set of MLC apertures via a leaf sequencing algorithm. To date, limited work has been done on this approach as it pertains to intensity modulated arc therapy (IMAT), specifically in regards to the latter two steps. There are two determining factors that separate IMAT segmentation and leaf sequencing from their IMRT equivalents: (1) the intrinsic 3D nature of the intensity maps (standard 2D maps plus the angular component), and (2) that the dynamic multileaf collimator (MLC) constraints be met using a minimum number of arcs. In this work, we illustrate a technique to create an IMAT plan that replicates Tomotherapy deliveries by applying IMAT specific segmentation and leaf-sequencing algorithms to Tomotherapy output sinograms. We propose and compare two alternative segmentation techniques, a clustering method, and a bottom-up segmentation method (BUS). We also introduce a novel IMAT leaf-sequencing algorithm that explicitly takes leaf movement constraints into consideration. These algorithms were tested with 51 angular projections of the output leaf-open sinograms generated on the Hi-ART II treatment planning system (Tomotherapy Inc.). We present two geometric phantoms and 2 clinical scenarios as sample test cases. In each case 12 IMAT plans were created, ranging from 2 to 7 intensity levels. Half were generated using the BUS segmentation and half with the clustering method. We report on the number of arcs produced as well as differences between Tomotherapy output sinograms and segmented IMAT intensity maps. For each case one plan for each segmentation method is chosen for full Monte Carlo dose calculation (NumeriX LLC) and dose volume histograms (DVH) are calculated. In all cases, the BUS method outperformed the clustering, method. We recommend using the BUS algorithm and discuss potential improvements to the clustering algorithms.

Gladwish, Adam; Oliver, Mike; Craig, Jeff; Chen, Jeff; Bauman, Glenn; Fisher, Barbara; Wong, Eugene [Department of Physics, London Regional Cancer Program, London (Canada) and Medical Biophysics, University of Western Ontario, London (Canada); Department of Physics, London Regional Cancer Program, London (Canada); Department of Physics, London Regional Cancer Program, London (Canada) and Departments of Oncology and Medical Biophysics, University of Western Ontario, London (Canada); Department of Oncology, University of Western Ontario, London (Canada); Department of Physics, London Regional Cancer Program, London (Canada) and Departments of Oncology and Medical Biophysics, University of Western Ontario, London (Canada)

2007-05-15

356

Segmentation and leaf sequencing for intensity modulated arc therapy.  

PubMed

A common method in generating intensity modulated radiation therapy (IMRT) plans consists of a three step process: an optimized fluence intensity map (IM) for each beam is generated via inverse planning, this IM is then segmented into discrete levels, and finally, the segmented map is translated into a set of MLC apertures via a leaf sequencing algorithm. To date, limited work has been done on this approach as it pertains to intensity modulated arc therapy (IMAT), specifically in regards to the latter two steps. There are two determining factors that separate IMAT segmentation and leaf sequencing from their IMRT equivalents: (1) the intrinsic 3D nature of the intensity maps (standard 2D maps plus the angular component), and (2) that the dynamic multileaf collimator (MLC) constraints be met using a minimum number of arcs. In this work, we illustrate a technique to create an IMAT plan that replicates Tomotherapy deliveries by applying IMAT specific segmentation and leaf-sequencing algorithms to Tomotherapy output sinograms. We propose and compare two alternative segmentation techniques, a clustering method, and a bottom-up segmentation method (BUS). We also introduce a novel IMAT leaf-sequencing algorithm that explicitly takes leaf movement constraints into consideration. These algorithms were tested with 51 angular projections of the output leaf-open sinograms generated on the Hi-ART II treatment planning system (Tomotherapy Inc.). We present two geometric phantoms and 2 clinical scenarios as sample test cases. In each case 12 IMAT plans were created, ranging from 2 to 7 intensity levels. Half were generated using the BUS segmentation and half with the clustering method. We report on the number of arcs produced as well as differences between Tomotherapy output sinograms and segmented IMAT intensity maps. For each case one plan for each segmentation method is chosen for full Monte Carlo dose calculation (NumeriX LLC) and dose volume histograms (DVH) are calculated. In all cases, the BUS method outperformed the clustering, method. We recommend using the BUS algorithm and discuss potential improvements to the clustering algorithms. PMID:17555259

Gladwish, Adam; Oliver, Mike; Craig, Jeff; Chen, Jeff; Bauman, Glenn; Fisher, Barbara; Wong, Eugene

2007-05-01

357

"Breath figures" on leaf surfaces--formation and effects of microscopic leaf wetness  

PubMed Central

“Microscopic leaf wetness” means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 ?m, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past.

Burkhardt, Juergen; Hunsche, Mauricio

2013-01-01

358

Allometric analysis of the induced flavonols on the leaf surface of wild tobacco (Nicotiana attenuata).  

PubMed

Trichomes excrete secondary metabolites that may alter the chemical composition of the leaf surface, reducing damage caused by herbivores, pathogens and abiotic stresses. We examined the surface exudates produced by Nicotiana attenuata Torr. Ex Wats., a plant known to contain and secrete a number of secondary metabolites that are toxic or a deterrent to herbivorous insects. Extractions specific to the leaf surface, the trichomes, and the laminar components demonstrated the localization of particular compounds. Diterpene glycosides occurred exclusively in leaf mesophyll, whereas nicotine was found in both the trichomes and mesophyll. Neither rutin nor nicotine was found on the leaf surface. Quercetin and 7 methylated derivatives were found in the glandular trichomes and appeared to be excreted onto the leaf surface. We examined the elicitation of these flavonols on the leaf surface with a surface-area allometric analysis, which measures changes in metabolites independent of the effects of leaf expansion. The flavonols responded differently to wounding, methyl jasmonate (MeJA), herbivore attack and UV-C radiation, and the response patterns corresponded to their compound-specific allometries. Finding greater amounts of quercetin on younger leaves and reduced amounts after herbivore feeding and MeJA treatment, we hypothesized that quercetin may function as an attractant, helping the insects locate a preferred feeding site. Consistent with this hypothesis, mirids (Tupiocoris notatus) were found more often on mature leaves sprayed with quercetin at a concentration typical of young leaves than on unsupplemented mature leaves. The composition of metabolites on the leaf surface of N. attenuata changes throughout leaf development and in response to herbivore attack or environmental stress, and these changes are mediated in part by responses of the glandular trichomes. PMID:12620365

Roda, Amy L; Oldham, Neil J; Svatos, Ales; Baldwin, Ian T

2003-02-01

359

Paleotemperature Proxies from Leaf Fossils Reinterpreted in Light of Evolutionary History  

PubMed Central

Present-day correlations between leaf physiognomic traits (shape and size) and climate are widely used to estimate paleoclimate using fossil floras. For example, leaf-margin analysis estimates paleotemperature using the modern relation of mean annual temperature (MAT) and the site-proportion of untoothed-leaf species (NT). This uniformitarian approach should provide accurate paleoclimate reconstructions under the core assumption that leaf-trait variation principally results from adaptive environmental convergence, and because variation is thus largely independent of phylogeny it should be constant through geologic time. Although much research acknowledges and investigates possible pitfalls in paleoclimate estimation based on leaf physiognomy, the core assumption has never been explicitly tested in a phylogenetic comparative framework. Combining an extant dataset of 21 leaf traits and temperature with a phylogenetic hypothesis for 569 species-site pairs at 17 sites, we found varying amounts of non-random phylogenetic signal in all traits. Phylogenetic vs. standard regressions generally support prevailing ideas that leaf-traits are adaptively responding to temperature, but wider confidence intervals, and shifts in slope and intercept, indicate an overall reduced ability to predict climate precisely due to the non-random phylogenetic signal. Notably, the modern-day relation of proportion of untoothed taxa with mean annual temperature (NT-MAT), central in paleotemperature inference, was greatly modified and reduced, indicating that the modern correlation primarily results from biogeographic history. Importantly, some tooth traits, such as number of teeth, had similar or steeper slopes after taking phylogeny into account, suggesting that leaf teeth display a pattern of exaptive evolution in higher latitudes. This study shows that the assumption of convergence required for precise, quantitative temperature estimates using present-day leaf traits is not supported by empirical evidence, and thus we have very low confidence in previously published, numerical paleotemperature estimates. However, interpreting qualitative changes in paleotemperature remains warranted, given certain conditions such as stratigraphically closely-spaced samples with floristic continuity.

Little, Stefan A.; Kembel, Steven W.; Wilf, Peter

2010-01-01

360

7 CFR 29.2437 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Leaf. Medium to heavy body, mature, close, lean in oil, inelastic,...

2010-01-01

361

7 CFR 29.2437 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Leaf. Medium to heavy body, mature, close, lean in oil, inelastic,...

2009-01-01

362

Time to reconsider stem cell induction strategies.  

PubMed

Recent developments in stem cell research suggest that it may be time to reconsider the current focus of stem cell induction strategies. During the previous five years, approximately, the induction of pluripotency in somatic cells, i.e., the generation of so-called 'induced pluripotent stem cells' (iPSCs), has become the focus of ongoing research in many stem cell laboratories, because this technology promises to overcome limitations (both technical and ethical) seen in the production and use of embryonic stem cells (ESCs). A rapidly increasing number of publications suggest, however, that it is now possible to choose instead other, alternative ways of generating stem and progenitor cells bypassing pluripotency. These new strategies may offer important advantages with respect to ethics, as well as to safety considerations. The present communication discusses why these strategies may provide possibilities for an escape from the dilemma presented by pluripotent stem cells (self-organization potential, cloning by tetraploid complementation, patenting problems and tumor formation risk). PMID:24710555

Denker, Hans-Werner

2012-01-01

363

Leaf Morphology Affects Horseradish Regeneration In Vitro  

Microsoft Academic Search

The morphology of horseradish (Armoracia rusticana P. Gaertn., B. Mey & Scherb.) leaves varies through the growing season. The leaves range from laminate (complete) in the summer to pinnate (fern-leaf) toward the end of the growing season in the fall, with intermediate types appearing regularly. The causes of these changes are not understood. To determine whether leaf morphology affects their

A. M. Shehata; R. M. Skirvin; M. A. Norton

2008-01-01

364

Leaf peroxidase isozyme polymorphism of wild apple  

Microsoft Academic Search

The main aims of the study were to reveal the isozyme resemblances in the leaf peroxidase of wild apple and to define the traits related to the identification of Malus sylvestris Mill. The results of the study are based on leaf isozyme analysis of seven progenies selected according to the specific features of mother trees at their natural sites from

R. Petrokas; V. Stanys

2008-01-01

365

Leaf litter decomposition in three Adirondack lakes  

SciTech Connect

Decomposition of terrestrial leaf litter in three Adirondack lakes with water pH values approximately 5, 6, and 7 was studied. Litter bags containing leaves of American beech, sugar maple, red maple, leather leaf, and red spruce were placed in the lakes. Samples were removed periodically over a 3-year period and analyzed for loss in weight, changes in leaf surface area, carbon, nitrogen, and bacterial populations. The rate of decomposition of litter depended on the leaf species tested as well as on the lake water in which they were incubated. Of the five leaf species tested, red maple decomposed much faster and red spruce more slowly, i.e., red maple > sugar maple > beech > leather leaf > red spruce. Further, the data indicated that the rate of decomposition of the leaves differed among the lakes in the order Woods (pH approx. 5) < Sagamore (pH approx. 6) < Panther (pH approx. 7), and that the microbial colonization of some leaf species was affected. Accumulations of leaf litter in acid lakes due to reduction in microbial decomposition may affect nutrient recycling in lake ecosystems. 8 references, 4 tables.

Francis, A.J.; Quinby, H.L.; Hendrey, G.R.; Hoogendyk, C.G.

1983-04-01

366

Leaf and Air Temperature under Hawaii Conditions  

Microsoft Academic Search

During the daylight hours pineapple leaf tem ­ per ature was consistently higher than the air temperature measured in an instrument shelter at the same elevation as the plants. The values usually ranged from 1.5° to 3.5° C. above the air temperature but occasionally a leaf exp osed to direct sunlight had a temperature as mu ch as 7.6 °

T. L. NOFFSINGER

367

Carrot red leaf virus in Israel  

Microsoft Academic Search

Carrot (Daucus carota) plants in commercial fields in Israel quite often evince symptoms of leaf reddening (mainly of older leaves), leaf yellowing, and sometimes plant stunting. These symptoms were observed mainly on plants near the edges of the fields and they were attributed to trace element deficiencies, herbicide drifts and low temperature injuries. Incidence of symptomcarrying plants varied in different

S. Marco

1993-01-01

368

Leaf epifauna of the seagrass Thalassia testudinum  

Microsoft Academic Search

The abundance, composition and trophic relationships of metazoan leaf epifauna of the marine angiosperm Thalassia testudinum König were studied in Barbados, West Indies. Approximately 90 species from 11 phyla consisted chiefly of nematodes, harpacticoid copepods, crustacean nauplii, ostracods, and turbellarians. Epiflora- and detritus-feeders dominated the epifauna. Increasing leaf epiphytism was accompanied by faunal changes, most notably increased nematode, harpacticoid and

J. B. Lewis; C. E. Hollingworth

1982-01-01

369

Leaf Histology--Two Modern Methods.  

ERIC Educational Resources Information Center

Two methods for examining leaf structure are presented; both methods involve use of "superglue." The first method uses the glue to form a thin, permanent, direct replica of a leaf surface on a microscope slide. The second method uses the glue to examine the three-dimensional structure of spongy mesophyll. (JN)

Freeman, H. E.

1984-01-01

370

The red edge of plant leaf reflectance  

Microsoft Academic Search

The red edge is the sharp change in leaf reflectance between 680 and 750 nm and has been measured on leaves of a variety of species by first derivative reflectance spectrophotometry. A parameter ?re was defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration (p<0.001), with additional effects of species, developmental stage, leaf layering

D. N. H. Horler; M. Dockray; J. Barber

1983-01-01

371

Tumor Angiogenesis and the Cancer Stem Cell Model  

Microsoft Academic Search

In recent years, research and interest in the area of cancer stem cells has grown tremendously. An increasing number of studies\\u000a are finding that many different cancers contain a subpopulation of tumor cells that display several defining characteristics\\u000a of adult tissue stem cells, including multipotent differentiation potential, long-term self-renewal capacity, and the expression\\u000a of various molecular markers of stemness. Most

Chris Folkins; Robert S. Kerbel

372

Placenta-an alternative source of stem cells  

SciTech Connect

The two most promising practical applications of human stem cells are cellular replacement therapies in human disease and toxicological screening of candidate drug molecules. Both require a source of human stem cells that can be isolated, purified, expanded in number and differentiated into the cell type of choice in a controlled manner. Currently, uses of both embryonic and adult stem cells are investigated. While embryonic stem cells are pluripotent and can differentiate into any specialised cell type, their use requires establishment of embryonic stem cell lines using the inner cell mass of an early pre-implantation embryo. As the blastocyst is destroyed during the process, ethical issues need to be carefully considered. The use of embryonic stem cells is also limited by the difficulties in growing large numbers of the cells without inducing spontaneous differentiation, and the problems in controlling directed differentiation of the cells. The use of adult stem cells, typically derived from bone marrow, but also from other tissues, is ethically non-controversial but their differentiation potential is more limited than that of the embryonic stem cells. Since human cord blood, umbilical cord, placenta and amnion are normally discarded at birth, they provide an easily accessible alternative source of stem cells. We review the potential and current status of the use of adult stem cells derived from the placenta or umbilical cord in therapeutic and toxicological applications.

Matikainen, Tiina [Program of Developmental and Reproductive Biology, Biomedicum Helsinki and Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki (Finland); Laine, Jarmo [Stem Cell and Transplantation Services, Finnish Red Cross Blood Service, Kivihaantie 7, FIN 00310, Helsinki (Finland)]. E-mail: jarmo.laine@bts.redcoss.fi

2005-09-01

373

Elevated CO22 and Leaf Longevity in the C44 Grassland-Dominant Andropogon gerardii.  

PubMed

In central U.S. grasslands, plant and ecosystem responses to elevated CO2 are most pronounced when water availability is limited. In a northeast Kansas grassland, responses to elevated CO2 in leaf area, number, development, and longevity were quantified for the tallgrass prairie dominant, Andropogon gerardii. Plants were grown in open-top chambers (OTCs) modified to limit water availability and to maximize responses to elevated CO2. In OTCs with elevated (x2 ambient) levels of CO2, aboveground biomass production and leaf water potentials were increased significantly compared with those of plants in OTCs with ambient CO2. There were no differences in leaf area or leaf number per tiller in A. gerardii in elevated compared with ambient OTCs. However, leaf area in adjacent unchambered plots with greater water availability was significantly higher than in the OTCs. The time required for developing leaves to achieve maximum leaf area was reduced by 29%, and the period of time until leaves senesced was increased by 20% for plants exposed to elevated compared with ambient CO2. Thus, leaves of this C4 grass species expanded more rapidly (6 d) and remained green longer (9 d) when exposed to elevated CO2. Such CO2-mediated increases in leaf longevity in the dominant species may allow this grassland to respond more opportunistically to temporally variable rainfall patterns in high-CO2 environments. These responses should be included in leaf-based simulation models that attempt to mechanistically link physiological alterations to predicted canopy responses to increased CO2. PMID:10568772

Knapp; Bargmann; Maragni; McAllister; Bremer; Ham; Owensby

1999-11-01

374

Protective effects of leaf extract of Zanthoxylum ailanthoides on oxidation of low-density lipoprotein and accumulation of lipid in differentiated THP1 cells  

Microsoft Academic Search

It has been reported that extracts of stem and leaf of Zanthoxylum ailanthoides (ZLE) possess antioxidative properties. However, the biological importance of the ZLE is not well known. In our preliminary study, it showed that ZLE prepared from 75% alcohol highly contains flavonoids (5.8%). By HPLC analysis, it shows that the ZLE consists of flavonoid glycosides including rutin and hyperoside.

Chin-Ying Chu; Huei-Jane Lee; Chia-Yih Chu; Yu-Fang Yin; Tsui-Hwa Tseng

2009-01-01

375

MicroRNAs as novel regulators of stem cell fate  

PubMed Central

Mounting evidence in stem cell biology has shown that microRNAs (miRNAs) play a crucial role in cell fate specification, including stem cell self-renewal, lineage-specific differentiation, and somatic cell reprogramming. These functions are tightly regulated by specific gene expression patterns that involve miRNAs and transcription factors. To maintain stem cell pluripotency, specific miRNAs suppress transcription factors that promote differentiation, whereas to initiate differentiation, lineage-specific miRNAs are upregulated via the inhibition of transcription factors that promote self-renewal. Small molecules can be used in a similar manner as natural miRNAs, and a number of natural and synthetic small molecules have been isolated and developed to regulate stem cell fate. Using miRNAs as novel regulators of stem cell fate will provide insight into stem cell biology and aid in understanding the molecular mechanisms and crosstalk between miRNAs and stem cells. Ultimately, advances in the regulation of stem cell fate will contribute to the development of effective medical therapies for tissue repair and regeneration. This review summarizes the current insights into stem cell fate determination by miRNAs with a focus on stem cell self-renewal, differentiation, and reprogramming. Small molecules that control stem cell fate are also highlighted.

Choi, Eunhyun; Choi, Eunmi; Hwang, Ki-Chul

2013-01-01

376

Neural stem cells: Brain building blocks and beyond  

PubMed Central

Neural stem cells are the origins of neurons and glia and generate all the differentiated neural cells of the mammalian central nervous system via the formation of intermediate precursors. Although less frequent, neural stem cells persevere in the postnatal brain where they generate neurons and glia. Adult neurogenesis occurs throughout life in a few limited brain regions. Regulation of neural stem cell number during central nervous system development and in adult life is associated with rigorous control. Failure in this regulation may lead to e.g. brain malformation, impaired learning and memory, or tumor development. Signaling pathways that are perturbed in glioma are the same that are important for neural stem cell self-renewal, differentiation, survival, and migration. The heterogeneity of human gliomas has impeded efficient treatment, but detailed molecular characterization together with novel stem cell-like glioma cell models that reflect the original tumor gives opportunities for research into new therapies. The observation that neural stem cells can be isolated and expanded in vitro has opened new avenues for medical research, with the hope that they could be used to compensate the loss of cells that features in several severe neurological diseases. Multipotent neural stem cells can be isolated from the embryonic and adult brain and maintained in culture in a defined medium. In addition, neural stem cells can be derived from embryonic stem cells and induced pluripotent stem cells by in vitro differentiation, thus adding to available models to study stem cells in health and disease.

Bergstrom, Tobias

2012-01-01

377

Storage of hemopoietic stem cells  

PubMed Central

Background: Autologous, and in some cases allogeneic, hemopoietic stem cells (HSC) are stored for varying periods of time prior to infusion. For periods of greater than 48 h, storage requires cryopreservation. It is essential to optimize cell storage and ensure the quality of the product for subsequent reinfusion. Methods: A number of important variables may affect the subsequent quality of infused HSC and therapeutic cells (TC). This review discusses these and also reviews the regulatory framework that now aims to ensure the quality of stem cells and TC for transplantation. Results: Important variables included cell concentration, temperature, interval from collection to cryopreservation, manipulations performed. They also included rate of freezing and whether controlled-rate freezing was employed. Parameters studied were type of cryoprotectant utilized [dimethyl sulphoxide (DMSO) is most commonly used, sometimes in combination with hydroxyethyl starch (HES)]; and storage conditions. It is also important to assess the quality of stored stem cells. Measurements employed included the total cell count (TNC), mononuclear cell count (MNC), CD34+ cells and colony-forming units - granulocyte macrophage (CFU-GM). Of these, TNC and CD34+ are the most useful. However, the best measure of the quality of stored stem cells is their subsequent engraftment. The quality systems used in stem cell laboratories are described in the guidance of the Joint Accreditation Committee of ISCT (Europe) and the EBMT (JACIE) and the EU Directive on Tissues and Cells plus its supporting commission directives. Inspections of facilities are carried out by the appropriate national agencies and JACIE. Conclusion: For high-quality storage of HSC and TC, processing facilities should use validated procedures that take into account critical variables. The quality of all products must be assessed before and after storage.

Pamphilon, Derwood; Mijovic, Aleksandar

2007-01-01

378

Physiological, anatomical and leaf hydraulic effects on leaf water ?18O enrichment in different plant species  

NASA Astrophysics Data System (ADS)

Stable oxygen isotope ratios (?18O) of plant and source waters are valuable tools in the analysis of water and carbon fluxes at leaf, plant, and ecosystem scales. Recent improvements in mechanistic models have significantly advanced the understanding of isotopic leaf water enrichment, which is an important source of ?18O variability in plants and ecosystems. However, the marked variability in leaf water ?18O values that have been reported for different plant species hampers efforts to interpret and then apply data on leaf water ?18O values for studies conducted at the ecosystem scale. To improve the understanding and application of ?18O values in leaf water, we tested the interplay of physiological, morphological, anatomical and leaf hydraulic properties as drivers of leaf water ?18O values across 17 Eucalyptus species growing in a common garden. We observed large differences in leaf water ?18O across the 17 species. These differences were only partly driven by physiological and leaf morphological differences across species. A sensitivity analysis using state-of-the-art leaf water enrichment models showed that the parameter - effective path length - (L) is of critical importance for the variability of leaf water ?18O across different species. The data show that L can be related to a suite of leaf properties that include physiology, anatomy and hydraulics. Consequently, consideration of leaf properties will significantly improve the interpretation of ?18O values in leaf water across different plant species and will therefore help in the application of ?18O values in carbon and water cycle assessments at both the plant and the ecosystem scale.

Kahmen, A.; Arndt, S. K.; Dawson, T. E.

2007-12-01

379

Adipose stem cells and skeletal repair.  

PubMed

Although adipose tissue has been considered a useless tissue, recent investigations have shown that it provides an abundant source of adult stem cells. Adipose stem cells (ADCs) can undergo rapid osteogenenic differentiation, which represents a promising option for bone tissue engineering and treating large bone defects. While bone marrow-derived stem cells have been more extensively studied for bone tissue engineering, a limitation exists in the harvested amount of bone marrow. As adipose tissue can provide a much greater number of adult stem cells without causing morbidity, it offers a good option as a bone tissue engineering cell source. In this review, we discuss the definition of ASCs, the induction of osteogenic differentiation from ASCs, scaffolding materials for adipose bone tissue engineering, and in vivo models for future clinical applications. PMID:23258367

Im, Gun-Il

2013-05-01

380

Pluripotent Stem Cells and Gene Therapy  

PubMed Central

Human pluripotent stem cells represent an accessible cell source for novel cell-based clinical research and therapies. With the realization of induced pluripotent stem cells (iPSCs), it is possible to produce almost any desired cell type from any patient's cells. Current developments in gene modification methods have opened the possibility for creating genetically corrected human iPSCs for certain genetic diseases that could be used later in autologous transplantation. Promising preclinical studies have demonstrated correction of disease-causing mutations in a number of hematological, neuronal and muscular disorders. This review aims to summarize these recent advances with a focus on iPSC generation techniques, as well as gene modification methods. We will then further discuss some of the main obstacles remaining to be overcome before successful application of human pluripotent stem cell-based therapy arrives in the clinic and what the future of stem cell research may look like.

Simara, Pavel; Motl, Jason A.; Kaufman, Dan S.

2013-01-01

381

The PAWS and STEM reliability analysis programs  

NASA Technical Reports Server (NTRS)

The PAWS and STEM programs are new design/validation tools. These programs provide a flexible, user-friendly, language-based interface for the input of Markov models describing the behavior of fault-tolerant computer systems. These programs produce exact solutions of the probability of system failure and provide a conservative estimate of the number of significant digits in the solution. PAWS uses a Pade approximation as a solution technique; STEM uses a Taylor series as a solution technique. Both programs have the capability to solve numerically stiff models. PAWS and STEM possess complementary properties with regard to their input space; and, an additional strength of these programs is that they accept input compatible with the SURE program. If used in conjunction with SURE, PAWS and STEM provide a powerful suite of programs to analyze the reliability of fault-tolerant computer systems.

Butler, Ricky W.; Stevenson, Philip H.

1988-01-01

382

Cancer stem cells - normal stem cells \\  

Microsoft Academic Search

Evidence has accumulated that cancer develops from a population of quiescent tissue committed\\/pluripotent stem cells (TCSC\\/PSC) or cells developmentally closely related to them that are distributed in various organs. To support this notio n, stem cells (SC) are long lived cells and thus may become the subject of accumulating mutations that are crucial for initiation\\/progression of cancer. More important, they

Mariusz Z. Ratajczak

2005-01-01

383

Measurement of leaf hydraulic conductance and stomatal conductance and their responses to irradiance and dehydration using the Evaporative Flux Method (EFM).  

PubMed

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to achieve a high stomatal conductance (gs) to capture CO2 for photosynthesis, water is lost by transpiration(1,2). Water evaporating from the airspaces is replaced from cell walls, in turn drawing water from the xylem of leaf veins, in turn drawing from xylem in the stems and roots. As water is pulled through the system, it experiences hydraulic resistance, creating tension throughout the system and a low leaf water potential (?(leaf)). The leaf itself is a critical bottleneck in the whole plant system, accounting for on average 30% of the plant hydraulic resistance(3). Leaf hydraulic conductance (K(leaf) = 1/ leaf hydraulic resistance) is the ratio of the water flow rate to the water potential gradient across the leaf, and summarizes the behavior of a complex system: water moves through the petiole and through several orders of veins, exits into the bundle sheath and passes through or around mesophyll cells before evaporating into the airspace and being transpired from the stomata. K(leaf) is of strong interest as an important physiological trait to compare species, quantifying the effectiveness of the leaf structure and physiology for water transport, and a key variable to investigate for its relationship to variation in structure (e.g., in leaf venation architecture) and its impacts on photosynthetic gas exchange. Further, K(leaf) responds strongly to the internal and external leaf environment(3). K(leaf) can increase dramatically with irradiance apparently due to changes in the expression and activation of aquaporins, the proteins involved in water transport through membranes(4), and K(leaf) declines strongly during drought, due to cavitation and/or collapse of xylem conduits, and/or loss of permeability in the extra-xylem tissues due to mesophyll and bundle sheath cell shrinkage or aquaporin deactivation(5-10). Because K(leaf) can constrain gs and photosynthetic rate across species in well watered conditions and during drought, and thus limit whole-plant performance they may possibly determine species distributions especially as droughts increase in frequency and severity(11-14). We present a simple method for simultaneous determination of K(leaf) and gs on excised leaves. A transpiring leaf is connected by its petiole to tubing running to a water source on a balance. The loss of water from the balance is recorded to calculate the flow rate through the leaf. When steady state transpiration (E, mmol • m(-2) • s(-1)) is reached, gs is determined by dividing by vapor pressure deficit, and K(leaf) by dividing by the water potential driving force determined using a pressure chamber (K(leaf)= E /- ??(leaf), MPa)(15). This method can be used to assess K(leaf) responses to different irradiances and the vulnerability of K(leaf) to dehydration(14,16,17). PMID:23299126

Sack, Lawren; Scoffoni, Christine

2012-01-01

384

Stem cells and stem cell-derived tissues and their use in safety assessment.  

PubMed

Toxicology has long relied on animal models in a tedious approach to understanding risk of exposure to an uncharacterized molecule. Stem cell-derived tissues can be made in high purity, quality, and quantity to enable a new approach to this problem. Currently, stem cell-derived tissues are primarily "generic" genetic backgrounds; the future will see the integration of various genetic backgrounds and complex three-dimensional models to create truly unique in vitro organoids. This minireview focuses on the state of the art of a number of stem cell-derived tissues and details their application in toxicology. PMID:24362027

Kolaja, Kyle

2014-02-21

385

Voxel tree modeling for estimating leaf area density and woody material volume using 3-D LIDAR data  

NASA Astrophysics Data System (ADS)

In this work, the main focus is on voxel tree modeling using 3-D lidar data for accurate leaf area density (LAD) and woody material volume estimation. For more accurate LAD estimation, the voxel model was constructed by combining airborne and portable ground-based lidar data. The profiles obtained by the two types of lidar complemented each other, thus eliminating blind regions and yielding more accurate LAD profiles than could be obtained by using each type of lidar alone. Parts of the LAD profiles that were underestimated even when data from both lidars were combined were interpolated by using a Gaussian function, yielding improved results. A laser beam coverage index, ?, incorporating the lidar's laser beam settings and a laser beam attenuation factor, was proposed. This index showed general applicability to explain the LAD estimation error for LAD measurements using different types of lidars. In addition, we proposed a method for accurate woody material volume estimation based on a 3-D voxel-based solid modeling of the tree from portable scanning lidar data. The solid model was composed of consecutive voxels that filled the outer surface and the interior of the stem and large branches. By using the model, the woody material volume of not only the whole target tree but also of any part of the target tree can be directly calculated easily and accurately by counting the number of corresponding voxels and multiplying the result by the per-voxel volume.

Hosoi, F.; Nakai, Y.; Omasa, K.

2013-10-01

386

Mesenchymal stem cells regulate the proliferation and differentiation of neural stem cells through Notch signaling  

Microsoft Academic Search

The effects of mesenchymal stem cells (MSCs) on proliferation and cell fate determination of neural stem cells (NSCs) have been investigated. NSCs were co-cultured with MSCs or NIH3T3 cells using an in vitro transwell system. After 4 days, immunofluorescence staining showed that the number of cells positive for the cell proliferation antigen, ki-67, in neurospheres in MSCs was greater than

Yang Wang; Wei Tu; Yuanlei Lou; An Xie; Xianliang Lai; Fei Guo; Zhifeng Deng

2009-01-01

387

Plerixafor added to G-CSF-supported paclitaxel-ifosfamide-cisplatin salvage chemotherapy enhances mobilization of adequate numbers of hematopoietic stem cells for subsequent autografting in hard-to-mobilize patients with relapsed/refractory germ-cell tumors: a single-center experience.  

PubMed

An appreciable percentage of patients with relapsed/refractory germ-cell tumors (GCTs), candidates for high-dose chemotherapy (HDC) and autologous hematopoietic cell transplantation (HCT), fail to mobilize adequate hematopoietic stem cells (HSCs) numbers with granulocyte colony-stimulating factor (G-CSF)±salvage chemotherapy. Plerixafor has shown a potential to mobilize adequate CD34+HSCs numbers in this context. Here, we applied plerixafor in combination with G-CSF after salvage chemotherapy in 'poor' mobilizers with relapsed/refractory GCTs for HDC+HCT. Patients with relapsed/refractory GCTs (n=10) received salvage paclitaxel-ifosfamide-cisplatin (TIP) chemotherapy+G-CSF to mobilize adequate HSCs to support HDC, mainly with two courses of high-dose thiotepa-etoposide-carboplatin (TEC). Patients failing to achieve the minimum collection threshold of 2.0×10/kg CD34+ cells, to support at least one cycle of HDC, were administered plerixafor before the anticipated HSC collection during subsequent cycle(s). Overall, seven patients mobilized adequate CD34+ cells (>5.0×10/kg) aiming to support two cycles of HDC. Three patients did not mobilize adequate numbers of CD34+ cells after previous G-CSF plus salvage TIP, and plerixafor was added in subsequent cycle(s). This led to a collection of adequate CD34+ cells, able to support HDC with TEC (1-2 cycles). Hematopoietic engraftment for neutrophils (absolute neutrophil count>500/?l) and platelets (platelet count>20 000/?l) with plerixafor-mobilized HSCs occurred after a median of 9 and 14 days, respectively. Salvage TIP+G-CSF leads to successful HSC mobilization in patients with less heavily pretreated GCTs, whereas the addition of plerixafor to G-CSF+TIP led to mobilization of adequate HSCs that supported autografting after one to two TEC cycles. PMID:24625457

Kosmas, Christos; Athanasopoulos, Aggelos; Dimitriadis, George; Miltiadous, Constantinos; Zilakos, Minas; Lydakis, Dimitris; Magiorkinis, Emmanouel; Gekas, Christos; Daladimos, Theodoros; Mylonakis, Nikolaos; Ziras, Nikolaos

2014-08-01

388

Community Partnerships for Fostering Student Interest and Engagement in STEM  

ERIC Educational Resources Information Center

The foundations of Science, Technology, Engineering and Mathematics (STEM) education begins in the early years of schooling when students encounter formal learning experiences primarily in mathematics and science. Politicians, economists and industrialists recognise the importance of STEM in society, and therefore a number of strategies have been…

Watters, James J.; Diezmann, Carmel M.

2013-01-01

389

Primary stability of custom and anatomical uncemented femoral stems  

Microsoft Academic Search

BackgroundLack of primary stability of cementless hip stems prevents bone ingrowth and may lead to loosening of the stem. Direct measures of the implant stability require drilled holes in the bone at the measuring site. These holes weaken the cortical bone, limit the number of possible measuring points and inhibit other biomechanical measurements. This in vitro study aimed to develop

Per Olav Østbyhaug; Jomar Klaksvik; Pål Romundstad; Arild Aamodt

2010-01-01

390

Therapeutic potential of genetically modified mesenchymal stem cells  

Microsoft Academic Search

Bone marrow-derived mesenchymal stem cells (MSC) are multipotent adult stem cells of mesodermal origin localized within the bone marrow compartment. MSC possess multilineage property making them useful for a number of potential therapeutic applications. MSC can be isolated from the bone marrow, expanded in culture and genetically modified to serve as cell carriers for local or systemic therapy. Despite their

S Kumar; D Chanda; S Ponnazhagan

2008-01-01

391

Intracoronary Autologous CD34+ Stem Cell Therapy for Intractable Angina  

Microsoft Academic Search

Background\\/Objectives: A large number of patients with coronary artery disease experience angina that is not suitable for revascularization and is refractory to conventional medical therapy. Laboratory and preclinical studies have provided evidence for the safety and potential efficacy of autologous CD34+ stem cell therapies as treatment for angina. Clinical studies investigating intramyocardial transplantation of autologous CD34+ stem cells by catheter

Shihong Wang; Junyu Cui; Wei Peng; Min Lu

2010-01-01

392

A Quantitative and Dynamic Model for Plant Stem Cell Regulation  

Microsoft Academic Search

Plants maintain pools of totipotent stem cells throughout their entire life. These stem cells are embedded within specialized tissues called meristems, which form the growing points of the organism. The shoot apical meristem of the reference plant Arabidopsis thaliana is subdivided into several distinct domains, which execute diverse biological functions, such as tissue organization, cell-proliferation and differentiation. The number of

Florian Geier; Jan U. Lohmann; Moritz Gerstung; Annette T. Maier; Jens Timmer; Christian Fleck; Raya Khanin

2008-01-01

393

PTEN-deficient intestinal stem cells initiate intestinal polyposis  

Microsoft Academic Search

Intestinal polyposis, a precancerous neoplasia, results primarily from an abnormal increase in the number of crypts, which contain intestinal stem cells (ISCs). In mice, widespread deletion of the tumor suppressor Phosphatase and tensin homolog (PTEN) generates hamartomatous intestinal polyps with epithelial and stromal involvement. Using this model, we have established the relationship between stem cells and polyp and tumor formation.

Xi C He; Tong Yin; Justin C Grindley; Qiang Tian; Toshiro Sato; W Andy Tao; Raminarao Dirisina; Kimberly S Porter-Westpfahl; Mark Hembree; Teri Johnson; Leanne M Wiedemann; Terrence A Barrett; Leroy Hood; Hong Wu; Linheng Li

2007-01-01

394

Leaf wetness distribution within a potato crop  

NASA Astrophysics Data System (ADS)

The Netherlands has a mild maritime climate and therefore the major interest in leaf wetness is associated with foliar plant diseases. During moist micrometeorological conditions (i.e. dew, fog, rain), foliar fungal diseases may develop quickly and thereby destroy a crop quickly. Potato crop monocultures covering several hectares are especially vulnerable to such diseases. Therefore understanding and predicting leaf wetness in potato crops is crucial in crop disease control strategies. A field experiment was carried out in a large homogeneous potato crop in the Netherlands during the growing season of 2008. Two innovative sensor networks were installed as a 3 by 3 grid at 3 heights covering an area of about 2 hectares within two larger potato crops. One crop was located on a sandy soil and one crop on a sandy peat soil. In most cases leaf wetting starts in the top layer and then progresses downward. Leaf drying takes place in the same order after sunrise. A canopy dew simulation model was applied to simulate spatial leaf wetness distribution. The dew model is based on an energy balance model. The model can be run using information on the above-canopy wind speed, air temperature, humidity, net radiation and within canopy air temperature, humidity and soil moisture content and temperature conditions. Rainfall was accounted for by applying an interception model. The results of the dew model agreed well with the leaf wetness sensors if all local conditions were considered. The measurements show that the spatial correlation of leaf wetness decreases downward.

Heusinkveld, B. G.

2010-07-01

395

Breast cancer stem cells  

Microsoft Academic Search

Since the initial discovery of leukemia stem cells nearly a decade ago, a great deal of cancer research has focused on the\\u000a identification of cancer stem cells (CSCs) in many types of solid tumors, including breast cancer. Through analysis of cell\\u000a surface markers and xenotransplant models, a subpopulation of putative human breast cancer stem cells (BCSCs) that is CD24-negative\\/CD44-positive\\u000a (CD24?\\/CD44+)

Kazuharu Kai; Yoshimi Arima; Toshio Kamiya; Hideyuki Saya

2010-01-01

396

Embryonic Stem Cells  

Microsoft Academic Search

Stem cells, which have a great capacity for self-renewal and can differentiate into at least one committed cell type, exist\\u000a in embryonic and adult organisms of many phyla. Although stem cells of various types from mice and other lower organisms have\\u000a been studied for many years, it was not until the derivation of stem cell lines from human embryos in

Victoria L. Browning; Jon S. Odorico

397

Mesenchymal stem cells  

Microsoft Academic Search

The tremendous capacity of bone to regenerate is indicative of the presence of stem cells with the capability, by definition,\\u000a to self-renew as well as to give rise to daughter cells. These primitive progenitors, termed mesenchymal stem cells or bone\\u000a marrow stromal stem cells, exist postnatally, and are multipotent with the ability to generate cartilage, bone, muscle, tendon,\\u000a ligament, and

Richard O. C. Oreffo; Cyrus Cooper; Christopher Mason; Mark Clements

2005-01-01

398

Stem Cell Biology  

Microsoft Academic Search

\\u000a Stem cells are functionally defined as long-lived cells that can both self-renew and differentiate into multiple cell types.\\u000a Embryonic stem cells, considered totipotent cells, give rise to all embryonic tissue layers and, consequently, all tissue\\u000a types. Hematologists\\/oncologists are perhaps most familiar with hematopoietic stem cells (HSCs): the single pluripotent cell\\u000a that can give rise to all lymphoid, myeloid and erythroid

Elizabeth O. Hexner; Stephen G. Emerson

399

Assessing brain stem function.  

PubMed

Intraoperative neurophysiologic monitoring provides objective measures of nervous system function that are of value when operating in proximity to the brain stem. Real-time measurements of function can be correlated to operative manipulations in order to reduce the risk of damage in critically important regions. Techniques for evaluating brain stem function clinically and electrophysiologically are presented along with their applications during surgery of the brain stem. PMID:8353442

Sclabassi, R J; Kalia, K K; Sekhar, L; Jannetta, P J

1993-07-01

400

Radiation sensitivity of the hemopoietic stem cell.  

PubMed

The LD50/30 after total-body irradiation (TBI) indicates the radiosensitivity of any animal species and is determined by the number and radiosensitivity of the hemopoietic stem cells, in particular those that are pluripotent. The most extensive information exists for the mouse because in the species the pluripotential stem cells can be enumerated by the spleen colony assay. Stem cells of various species can also be quantified in vitro by the CFU-S and CFU-C assays. With the latter assay, the reported values for D0 and N vary by factors of 2-3 and up to 5, respectively. In both assays the upper level of the range of doses is about 5 Gy. A theoretical approach for the calculation of the D0 of hemopoietic stem cells was previously developed by comparing the number of autologous or syngeneic bone marrow cells required to protect 50% of supralethally irradiated animals with the known LD50/30 of the species and the estimates of total number of bone marrow cells present before irradiation. Using the rate of repopulation of peripheral blood cells in monkeys following high-dose TBI and the repopulation of the spleen and the bone marrow in mice, we have derived estimates of the surviving fractions of hemopoietic stem cells at radiation doses between 5 and 10 Gy. The resulting data suggest, among other possibilities, the presence of a small subpopulation of hemopoietic stem cells with higher radioresistance than the majority of the stem cells. It was postulated that this small subpopulation may exist under hypoxic conditions. To test this hypothesis, RBEs for fission neutrons have been determined for CFU-S survival and for LD50/30 in BCBA mice. Both RBEs were very similar, which proves that the radioresistance of the subpopulation responsible for survival at high doses is not due to hypoxic conditions. PMID:1924746

van Bekkum, D W

1991-10-01

401

Characterization of Pepper yellow leaf curl virus, a tentative new Polerovirus species causing a yellowing disease of pepper  

Microsoft Academic Search

Pepper (Capsicum annuum) is an important crop worldwide. In Israel, approximately 2,500 ha are grown all year round for the local and export markets.\\u000a Herein, we report the identification of a viral pathogen causing a new devastating disease in pepper crops. The disease syndrome\\u000a includes shortening of stem internodes, interveinal yellowing, and upward rolling of the leaf blade, accompanied by fruit

Aviv Dombrovsky; Eyal Glanz; Mali Pearlsman; Oded Lachman; Yehezkel Antignus

2010-01-01

402

Regulation of chloroplast number and DNA synthesis in higher plants. Final report, August 1995--August 1996  

SciTech Connect

The long term objective of this research is to understand the process of chloroplast development and its coordination with leaf development in higher plants. This is important because the photosynthetic capacity of plants is directly related to leaf and chloroplast development. This research focused on obtaining a detailed description of leaf development and the early steps in chloroplast development including activation of plastid DNA synthesis, changes in plastid DNA copy number, activation of chloroplast transcription and increases in plastid number per cell. The research focused on the isolation of the plastid DNA polymerase, and identification of genetic mutants which are altered in their accumulation of plastid DNA and plastid number per cell.

Mullet, J.E.

1997-06-17

403

Stem Cell Resources  

NSDL National Science Digital Library

The mission of the Stem Cell Resources website is "to provide timely, reliable, high-quality and scientifically credible stem cell information for the educational community worldwide." The website is a division of Bioscience Network which publishes online science education materials. On the site, visitors will find a stem cell image library, a multimedia area, and a special section titled "For Educators". In the "For Educators" area, visitors will find links to a primer on stem cells and links to educational resources on stem cells from curriculum to case studies to lesson plans from such trusted sources as the Australian Stem Cell Centre and the National Institutes of Health. Moving on, the "Multimedia" area includes videos that show how embryonic stem cell lines are made, along with other animations and graphics on the topic. Additionally, the site's "SCR Library" area includes the link to the Stem Cell Image Library, which provides dozens of photos of stem cells taken from researchers at the University of Cambridge and other institutions.

404

Stem cells and reproduction  

PubMed Central

Purpose of review To review the latest developments in reproductive tract stem cell biology. Recent findings In 2004, two studies indicated that ovaries contain stem cells which form oocytes in adults and that can be cultured in vitro into mature oocytes. A live birth after orthotopic transplantation of cyropreserved ovarian tissue in a woman whose ovaries were damaged by chemotherapy demonstrates the clinical potential of these cells. In the same year, another study provided novel evidence of endometrial regeneration by stem cells in women who received bone marrow transplants. This finding has potential for the use in treatment of uterine disorders. It also supports a new theory for the cause of endometriosis, which may have its origin in ectopic transdifferentiation of stem cells. Several recent studies have demonstrated that fetal cells enter the maternal circulation and generate microchimerism in the mother. The uterus is a dynamic organ permeable to fetal stem cells, capable of transdifferentiation and an end organ in which bone marrow stem cells may differentiate. Finally stem cell transformation can be an underlying cause of ovarian cancer. Summary Whereas we are just beginning to understand stem cells, the potential implications of stem cells to reproductive biology and medicine are apparent.

Du, Hongling; Taylor, Hugh S.

2011-01-01

405

Optimizing stem cell culture.  

PubMed

Stem cells always balance between self-renewal and differentiation. Hence, stem cell culture parameters are critical and need to be continuously refined according to progress in our stem cell biology understanding and the latest technological developments. In the past few years, major efforts have been made to define more precisely the medium composition in which stem cells grow or differentiate. This led to the progressive replacement of ill-defined additives such as serum or feeder cell layers by recombinant cytokines or growth factors. Another example is the control of the oxygen pressure. For many years cell cultures have been done under atmospheric oxygen pressure which is much higher than the one experienced by stem cells in vivo. A consequence of cell metabolism is that cell culture conditions are constantly changing. Therefore, the development of high sensitive monitoring processes and control algorithms is required for ensuring cell culture medium homeostasis. Stem cells also sense the physical constraints of their microenvironment. Rigidity, stiffness, and geometry of the culture substrate influence stem cell fate. Hence, nanotopography is probably as important as medium formulation in the optimization of stem cell culture conditions. Recent advances include the development of synthetic bioinformative substrates designed at the micro- and nanoscale level. On going research in many different fields including stem cell biology, nanotechnology, and bioengineering suggest that our current way to culture cells in Petri dish or flasks will soon be outdated as flying across the Atlantic Ocean in the Lindbergh's plane. PMID:20803548

van der Sanden, Boudewijn; Dhobb, Mehdi; Berger, François; Wion, Didier

2010-11-01

406

Stem cell policies in the United States and in Germany.  

PubMed

The article compares policymaking in the field of human embryonic stem cell research in the United States and Germany. Although experimental research with human stem cells is controversial in both countries, restrictions on research are much more strict in Germany than in the United States. In order to explain the contrast between the United States and Germany in dealing with human embryonic stem cell research and to predict possible future developments, we need to look carefully at a number of important differences in the interpretations and discourses of embryonic stem cell research and their consequences for the strategies of institutions and actors in the political-regulatory realm. PMID:17256227

Gottweis, Herbert

2002-01-01

407

Leaf rolling allows quantification of mRNA abundance in mesophyll cells of sorghum.  

PubMed

In the leaves of most C(4) plants, mesophyll (M) and bundle sheath (BS) cells develop and maintain highly differentiated biochemical networks. Separation and analysis of M and BS cells has greatly influenced our understanding of the C(4) pathway. A number of approaches including mechanical separation, digestion with cell wall-degrading cocktails, laser-capture microdissection, and leaf rolling have been used to isolate these cell types. Although leaf rolling is conceptually and practically the simplest method, to date it has only been used to assess the metabolite content of M cells from C(4) leaves of maize. This study reports an adapted leaf-rolling method for the isolation of high-quality RNA from M cells of sorghum. Analysis of leaf cell structure, RNA integrity, and transcript abundance of marker genes demonstrated that the sap collected by leaf rolling was from M cells and had no significant contamination. It was concluded that leaf rolling is a fast, cheap, and efficient method of measuring transcript abundance in M cells of sorghum. PMID:23077203

Covshoff, Sarah; Furbank, Robert T; Leegood, Richard C; Hibberd, Julian M

2013-01-01

408

Natural developmental variations in leaf and plant senescence in Arabidopsis thaliana.  

PubMed

Leaf senescence is a developmentally regulated process that contributes to nutrient redistribution during reproductive growth and finally leads to tissue death. Manipulating leaf senescence through breeding or genetic engineering may help to improve important agronomic traits, such as crop yield and the storage life of harvested organs. Here, we studied natural variations in the regulation of plant senescence among 16 Arabidopsis thaliana accessions. Chlorophyll content and the proportion of yellow leaves were used as indicator parameters to determine leaf and plant senescence respectively. Our study indicated significant genotype effects on the onset and development of senescence. We selected three late- and five early-senescence accessions for further physiological studies. The relationship between leaf and plant senescence was accession-dependent. There was a significant correlation between plant senescence and the total number of leaves, siliques and plant bolting age. We monitored expression of two senescence marker genes, SAG12 and WRKY53, to evaluate progression of senescence. Our data revealed that chlorophyll content does not fully reflect leaf age, because even fully green leaves had already commenced senescence at the molecular level. Integrating senescence parameters, such as the proportion of senescent leaves, at the whole plant level provided a better indication of the molecular status of the plant than single leaf senescence parameters. PMID:18721318

Balazadeh, S; Parlitz, S; Mueller-Roeber, B; Meyer, R C

2008-09-01

409

Intra-urban spatial variation of magnetic particles: Monitoring via leaf saturation isothermal remanent magnetisation (SIRM)  

NASA Astrophysics Data System (ADS)

Motorised traffic generates large numbers of small-sized, magnetisable particulate pollutants in the urban environment. Exposure to these small particles has been associated with adverse effects on human health. Magnetic properties of these particles are, therefore, increasingly used for assessing environmental stress. Biomonitoring of magnetic particles accumulated on leaf surfaces may provide information on the concentration of, and exposure to, atmospheric particles at high spatial resolution. In this study, leaf saturation isothermal remanent magnetisation (SIRM) of three urban tree types (Carpinus betulus and Tilia sp. with hairy and non-hairy leaves) was measured at high spatial resolution in the city of Gent, Belgium, in June and September 2009. We compared leaf SIRM between land use classes with different urban habitat quality. In a multiple regression model, we tried to explain the spatial variability in leaf SIRM by tree species, sampling height, distance to the nearest road and its traffic intensity, tram frequency and a measure for regional traffic emissions (derived from traffic intensity of and the distance to the most important highways around and in the city in the main four wind directions). We found that the leaf SIRM was significantly influenced by tree species, distance to the nearest road and its traffic intensity and tram frequency. The SIRM significantly increased with increasing traffic intensity and tram frequency and by decreasing distance to the nearest road. It is concluded that leaf SIRM is a good bio-indicator for monitoring spatial variation of magnetic particles in urban environments.

Kardel, F.; Wuyts, K.; Maher, B. A.; Samson, R.

2012-08-01

410

Diurnal Changes in Maize Leaf Photosynthesis 1  

PubMed Central

Maize (Zea mays L. cv. Pioneer 3184) leaf elongation rate was measured diurnally and was related to diurnal changes in the activities of sucrose metabolizing enzymes and carbohydrate content in the elongating portion of the leaf. The rate of leaf elongation was greatest at midday (1300 hours) and was coincident with the maximum assimilate export rate from the distal portion of the leaf. Leaf elongation during the light period accounted for 70% of the total observed increase in leaf length per 24 hour period. Pronounced diurnal fluctuations were observed in the activities of acid and neutral invertase and sucrose phosphate synthase. Maximum activities of sucrose phosphate synthase and acid invertase were observed at 0900 hours, after which activity declined rapidly. The activity of sucrose phosphate synthase was substantially lower than that observed in maize leaf source tissue. Neutral invertase activity was greatest at midday (1200 hours) and was correlated positively with diurnal changes in leaf elongation rate. There was no significant change in the activity of sucrose synthase over the light/dark cycle. Sucrose accumulation rate increased during a period when leaf elongation rate was maximal and beginning to decline. Maximum sucrose concentration was observed at 1500 hours, when the activities of sucrose metabolizing enzymes were low. At no time was there a significant accumulation of hexose sugars. The rate of starch accumulation increased after the maximum sucrose concentration was observed, continuing until the end of the light period. There was no delay in the onset of starch mobilization at the beginning of the dark period, and essentially all of the starch was depleted by the end of the night. Mobilization of starch in the elongating tissue at night could account for a significant proportion of the calculated increase in the tissue dry weight due to growth. Collectively, the results suggested that leaf growth may be controlled by the activities of certain sucrose metabolizing enzymes and may be coordinated with assimilate export from the distal, source portion of the leaf. Results are discussed with reference to diurnal photoassimilation and export in the distal, source portion of the leaf.

Kalt-Torres, Willy; Huber, Steven C.

1987-01-01

411

Key Proliferative Activity in the Junction between the Leaf Blade and Leaf Petiole of Arabidopsis1[W][OA  

PubMed Central

Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a leaf is clearly divided into the leaf blade and leaf petiole, no study has yet revealed how these are differentiated from a leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the leaf blade and leaf petiole and produces both leaf-blade and leaf-petiole cells. This proliferative region in leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and blade-on-petiole mutations further support the idea that organogenesis of the leaf blade and leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of leaf primordia. Thus, the proliferative zone of leaf primordia is spatially differentiated and supplies both the leaf-blade and leaf-petiole cells.

Ichihashi, Yasunori; Kawade, Kensuke; Usami, Takeshi; Horiguchi, Gorou; Takahashi, Taku; Tsukaya, Hirokazu

2011-01-01

412

The effect of a green leaf volatile on host plant finding by larvae of a herbivorous insect  

NASA Astrophysics Data System (ADS)

The role of a general green leaf volatile (glv) in host finding by larvae of the oligophagous chrysomelid Cassida denticollis was investigated using a new bioassay which takes into account the need for neonate larvae of this species to climb fresh host plants from the ground. A "stem arena" was designed in which plant stems of the host, tansy (Tanacetum vulgare), and stem dummies (tooth picks), both wrapped in perforated filter paper, were offered to neonate larvae. The wrapping allowed olfactory responses to be tested by preventing access to contact stimuli of stems and dummies. Larvae significantly preferred to climb the wrapped tansy stems over dummies after a period of 15min. The test glv, (Z)-3-hexen-1-ol, was not attractive when applied to dummies. However, when the glv was applied to the bottom of the arena, the ability of larvae to discriminate between host stems and untreated dummies was significantly enhanced. More larvae climbed wrapped host stems than dummies even within 5min. While numerous other herbivorous insects are known to be directly attracted by glv, this study shows that a singly offered glv on its own is unattractive to an herbivore but enhances the herbivore's ability to differentiate between host and nonhost plants.

Müller, Caroline; Hilker, M.

413

Stem cell-based therapies for osteoarthritis: Challenges and opportunities  

PubMed Central

Purpose of review Regenerative medicine offers the exciting potential of developing alternatives to total joint replacement for treating osteoarthritis (OA). In this article, we highlight recent work that addresses key challenges of stem cell-based therapies for OA and provide examples of innovative ways in which stem cells can aid in the treatment of OA. Recent findings Significant progress has been made in understanding the challenges to successful stem cell therapy, such as the effects of age or disease on stem cell properties, altered stem cell function due to an inflammatory joint environment, and phenotypic instability in vivo. Novel scaffold designs have been shown to enhance the mechanical properties of tissue-engineered cartilage and have also improved the integration of newly formed tissue within the joint. Emerging strategies such as injecting stem cells directly into the joint, manipulating endogenous stem cells to enhance regenerative capacity, and utilizing stem cells for drug discovery have expanded the potential uses of stem cells in treating OA. Summary A number of recent studies have greatly advanced the development and pre-clinical evaluation of potential stem cell-based treatments for OA through novel approaches focused on cell therapy, tissue engineering, and drug discovery.

Diekman, Brian O.; Guilak, Farshid

2013-01-01

414

What Afterschool STEM Does Best: How Stakeholders Describe Youth Learning Outcomes  

ERIC Educational Resources Information Center

As more stakeholders get involved in the effort to engage youth in STEM outside of school, afterschool providers are being asked to document a wide range of outcomes, from generating interest in STEM to improving standardized test scores in math and science and to increasing the number of students who pursue STEM majors in college. This issue has…

Krishnamurthi, Anita; Bevan, Bronwyn; Rinehart, Jen; Coulon, Vicky Ragan

2013-01-01

415

Insulin levels control female germline stem cell maintenance via the niche in Drosophila  

Microsoft Academic Search

Stem cell maintenance depends on local signals provided by specialized microenvironments, or niches, in which they reside. The potential role of systemic factors in stem cell maintenance, however, has remained largely unexplored. Here, we show that insulin signaling integrates the effects of diet and age on germline stem cell (GSC) maintenance through the dual regulation of cap cell number (via

Hwei-Jan Hsu; Daniela Drummond-Barbosa

2009-01-01

416

Using Community Colleges to Build a STEM-Skilled Workforce. Issue Brief  

ERIC Educational Resources Information Center

Education and skills in science, technology, engineering, and mathematics (STEM) are important in a global economy increasingly focused on high-growth, technology-driven occupations. Yet, many states face a shortage of STEM-skilled students and workers. A number of states have built powerful and productive STEM education and skills strategies to…

NGA Center for Best Practices, 2011

2011-01-01

417

Bax limits adult neural stem cell persistence through caspase and IP3 receptor activation  

Microsoft Academic Search

Neural stem cells in the mammalian brain persist and are functional well into adulthood. There is, however, little insight into mechanisms that control adult neural stem cell survival. Mice deficient in the proapoptotic molecule Bax exhibit increased numbers of multipotent progenitor cells in the adult subventricular zone. In vitro, these progenitors behave as neural stem cells and utilize Bax and

J Shi; L F Parada; S G Kernie

2005-01-01

418

Fossil leaf economics quantified: calibration, Eocene case study, and implications  

Microsoft Academic Search

Leaf mass per area (MA) is a central ecological trait that is intercorrelated with leaf life span, photosynthetic rate, nutrient concentration, and palatability to herbivores. These coordinated variables form a globally convergent leaf economics spectrum, which represents a general continuum running from rapid resource acquisition to maximized resource retention. Leaf economics are little studied in ancient ecosystems because they cannot

Dana L. Royer; Lawren Sack; Peter Wilf; Christopher H. Lusk; Gregory J. Jordan; Ülo Niinemets; Ian J. Wright; Mark Westoby; Bárbara Cariglino; Phyllis D. Coley; Asher D. Cutter; Kirk R. Johnson; Conrad C. Labandeira; Angela T. Moles; Matthew B. Palmer; Fernando Valladares

2007-01-01

419

7 CFR 28.516 - Leaf Grade No. 6.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Leaf Grade No. 6. 28.516 Section 28.516...Cotton Standards of the United States for the Leaf Grade of American Pima Cotton § 28.516 Leaf Grade No. 6. Leaf grade No. 6 shall...

2009-01-01

420

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2009-01-01