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1

Stem-and-Leaf Plots  

NSDL National Science Digital Library

This lesson is designed to introduce students to stem-and-leaf plots as a graphical way to represent a data set. The lesson also reviews measures of central tendency. This lesson provides links to discussions and activities related to stem-and-leaf plots as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

2

Ginseng leaf-stem: bioactive constituents and pharmacological functions  

Microsoft Academic Search

Ginseng root is used more often than other parts such as leaf stem although extracts from ginseng leaf-stem also contain similar active ingredients with pharmacological functions. Ginseng's leaf-stems are more readily available at a lower cost than its root. This article reviews the pharmacological effects of ginseng leaf-stem on some diseases and adverse effects due to excessive consumption. Ginseng leaf-stem

Hongwei Wang; Dacheng Peng; Jingtian Xie

2009-01-01

3

In vitro regeneration of Rubus from leaf and stem segments  

Microsoft Academic Search

Various media, sourees of explant and Rubus genotypes of diverse origin were assessed for their ability to regenerate whole plants in vitro. Regenerants were produced from leaf discs and from both peeled and unpeeled internodal stem segments but not from epidermal peelings. Hormone type and concentration, amount of sucrose, absence of activated charcoal, presence of light and for leaf discs

R. J. McNicol; Julie Graham

1990-01-01

4

Decoupled leaf and stem economics in rain forest trees.  

PubMed

Cross-species analyses of plant functional traits have shed light on factors contributing to differences in performance and distribution, but to date most studies have focused on either leaves or stems. We extend these tissue-specific analyses of functional strategy towards a whole-plant approach by integrating data on functional traits for 13?448 leaves and wood tissues from 4672 trees representing 668 species of Neotropical trees. Strong correlations amongst traits previously defined as the leaf economics spectrum reflect a tradeoff between investments in productive leaves with rapid turnover vs. costly physical leaf structure with a long revenue stream. A second axis of variation, the 'stem economics spectrum', defines a similar tradeoff at the stem level: dense wood vs. high wood water content and thick bark. Most importantly, these two axes are orthogonal, suggesting that tradeoffs operate independently at the leaf and at the stem levels. By simplifying the multivariate ecological strategies of tropical trees into positions along these two spectra, our results provide a basis to improve global vegetation models predicting responses of tropical forests to global change. PMID:20807232

Baraloto, Christopher; Timothy Paine, C E; Poorter, Lourens; Beauchene, Jacques; Bonal, Damien; Domenach, Anne-Marie; Hérault, Bruno; Patiño, Sandra; Roggy, Jean-Christophe; Chave, Jerome

2010-08-29

5

Resistance of leaf and stem fractions of tropical forage to chewing and passage in cattle.  

PubMed

The voluntary intake (VI) of separated leaf and stem fractions of a grass and legume (Panicum maximum and Lablab purpureus respectively) was determined using Hereford steers fistulated at the rumen and oesophagus. VI of leaf fractions was higher than that of the stem fraction (8.23 v. 3.67 kg/d, P less than 0.001) while that for the legume diets was higher than for the grass diets (6.65 v. 5.22 kg/d, P less than 0.05). The total number of eating chews per day was higher on the leaf than stem fraction (1.6 x 10(4) v. 9.8 x 10(3), P less than 0.05). The mean number of rumination chews (2.4 x 10(4)) was similar (P greater than 0.05) for all four diets. The mean resistance of large particles (LP, i.e. retained on a 1.18 mm sieve during wet sieving) to breakdown (chews per g LP breakdown) during eating was lower for leaf than stem fractions (8.4 v. 23.7) and lower for the grass than legume diets (10.5 v. 21.6). The mean resistance to breakdown of LP by rumination (chews per g LP breakdown) was lower in leaf than in stem fractions (8.2 v. 13.2, P less than 0.01) and higher in grass than in legume (12.5 v. 9.0, P less than 0.05). The resistance of LP to breakdown during rumination was higher than during eating for the grass diets, but was lower for the legume. Fractional passage rates (FPR) of small particles (i.e. passing through a 1.18 mm sieve during wet sieving) from the reticulo-rumen were negatively related to dimensions of particles, with greater ease of outflow for legume than for grass particles of the same length or diameter. When corrected for content of cellulase-indigestible fibre, FPR of small particles of leaf was greater than for small stem particles. It was concluded that VI of tropical forages was associated with the resistance of LP to breakdown by chewing during both eating and rumination and that the patterns of escape of small particles from the reticulo-rumen were only partially explicable in terms of particle dimensions, and that other properties of the particles may be of importance. PMID:2317472

McLeod, M N; Kennedy, P M; Minson, D J

1990-01-01

6

Photoautotrophic growth of potato plantlets as affected by explant leaf area, fresh weight and stem length  

Microsoft Academic Search

Photoautotrophic growth in vitro of potato (Solanum tuberosum L. cv. Benimaru) explants varied with their initial leaf area and stem length. Photoautotrophic growth was much greater in leafy than in leafless explants. Variability in photoautotrophic growth was smallest in the explants with the greatest leaf area. The results indicated that use of explants with a large leaf area is important

Yoshie Miyashita; Yoshiaki Kitaya; Chieri Kubota; Toyoki Kozai

1996-01-01

7

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

8

Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems.  

PubMed

Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species. However, maximum leaf hydraulic conductance (K (leaf)) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K (leaf) values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water potentials to drop from predawn values to values corresponding to 50% loss of K (leaf) or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits. PMID:18049826

Hao, Guang-You; Hoffmann, William A; Scholz, Fabian G; Bucci, Sandra J; Meinzer, Frederick C; Franco, Augusto C; Cao, Kun-Fang; Goldstein, Guillermo

2007-11-30

9

Greenhouse Detached-leaf and Field Testing Methods to Determine Cucumber Resistance to Gummy Stem Blight  

Microsoft Academic Search

Abstract. The effects of leaf age, guttation, stomata and hydathode characteristics, and wounding on the symptom development of gummy stem blight [Didymella bryoniae (Auersw.) Rehm] of cucumber (Cucumis sativus L.) were studied to develop a useful germplasm screening method. Older cucumber leaves were more susceptible than younger leaves in field, greenhouse, and detached-leaf tests. Compared to seedlings with true leaves,

Paul C. St. Amand; Todd C. Wehner

10

Separating soil and leaf water 18O isotopic signals in plant stem cellulose  

Microsoft Academic Search

The oxygen-18 signal of soil and leaf water are both recorded in heterotrophically synthesized plant stem cellulose. Presently, these signals can only be teased apart with modeling and assumptions on the nature of the isotopic enrichment of leaf water. A method by which these two signals are chemically separated and analyzed is tested here. Heterotrophically synthesized cellulose from germinating seeds

Leonel da Silveira Lobo Sternberg; William T. Anderson; Kanema Morrison

2003-01-01

11

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

12

First Report of Macrophomina phaseolina Causing Leaf and Stem Blight of Tropical Soda Apple in Florida.  

Technology Transfer Automated Retrieval System (TEKTRAN)

In August 2006 progressive leaf necrosis was observed in tropical soda apple (SOLVI ) plants in Fort Pierce, FL. Leaves of the five month old plants presented progressive necrosis, then dried out and dropped. Necrosis progressed quickly from petioles through the stems and caused entire stems to di...

13

Compositions and comparison of the leaf and stem essential oils from Nigerian Hypoestes phyllostachya 'rosea' p. Beau. (acanthaceae)  

Microsoft Academic Search

Leaf and stem volatile oils were obtained differently from Hypoestes phyllostachya 'Rosea' (Acanthaceae) in 0.36 and 0.13% yields, respectively. GC-MS analyses revealed 38 compounds are responsible for 99.86% of the leaf oil, and 26 compounds make-up 99.89% of the stem oil. Identified compounds were 26 in leaf, which make-up 93.43% of it; 21 identified in stem, which represent 90.45% of

D. O. Moronkola; O. C. Atewolara-Odule

14

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

2013-03-28

15

Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems  

Microsoft Academic Search

Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed\\u000a of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there\\u000a were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats\\u000a were studied. Most stem traits,

Guang-You Hao; William A. Hoffmann; Fabian G. Scholz; Sandra J. Bucci; Frederick C. Meinzer; Augusto C. Franco; Kun-Fang Cao; Guillermo Goldstein

2008-01-01

16

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

17

Leaf and Stem Area Relationships to Masses and Their Height Distributions in Native Grasses  

Microsoft Academic Search

i A recently developed wind erasion model (wind erosion prediction system, WEPS) for mop lands is being extended for estimating soil emsion from rangelands, military lands, and desert emsystem,. Wind velocity near the soil surface is calculated as a function of the serial distribution of stem silhouette area and leaf ares of both live plants and standing residue. Grasses either

Amare Retta; Dean V. Armbrust; Lawrence J. Hagen; Edward L. Skidmore

2000-01-01

18

Increasing the Number of STEM Graduates: Insights from the U.S. STEM Education & Modeling Project  

ERIC Educational Resources Information Center

|The Business-Higher Education Forum's (BHEF's) Securing America's Leadership in STEM Initiative has broken new ground in addressing one of the nation's most critical challenges--increasing the number of students who are interested in and pursue careers in science, technology, engineering or mathematics, the so-called "STEM" fields. The…

Business-Higher Education Forum (NJ1), 2010

2010-01-01

19

Intrinsic and Extrinsic Control of Hemopoietic Stem Cell Numbers: Mapping of a Stem Cell Gene  

Microsoft Academic Search

Summary We evaluated in vivo interactions between extrinsic (growth factor induced) and intrinsic (ge- netically determined) effectors of mouse primitive hemopoietic stem cell proliferation and numbers. Accordingly, stem cell frequency and cell cycle kinetics were assessed in eight strains of inbred mice using the cobblestone area-forming cell (CAFC) assay. A strong inverse correla- tion was observed between mouse lifespan and

Gerald de Haan; Gary Van Zant

20

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

21

Relationships between stem diameter, sapwood area, leaf area and transpiration in a young mountain ash forest.  

PubMed

We examined relationships between stem diameter, sapwood area, leaf area and transpiration in a 15-year-old mountain ash (Eucalyptus regnans F. Muell.) forest containing silver wattle (Acacia dealbata Link.) as a suppressed overstory species and mountain hickory (Acacia frigescens J.H. Willis) as an understory species. Stem diameter explained 93% of the variation in leaf area, 96% of the variation in sapwood area and 88% of the variation in mean daily spring transpiration in 19 mountain ash trees. In seven silver wattle trees, stem diameter explained 87% of the variation in sapwood area but was a poor predictor of the other variables. When transpiration measurements from individual trees were scaled up to a plot basis, using stem diameter values for 164 mountain ash trees and 124 silver wattle trees, mean daily spring transpiration rates of the two species were 2.3 and 0.6 mm day(-1), respectively. The leaf area index of the plot was estimated directly by destructive sampling, and indirectly with an LAI-2000 plant canopy analyzer and by hemispherical canopy photography. All three methods gave similar results. PMID:14965913

Vertessy, R A; Benyon, R G; O'Sullivan, S K; Gribben, P R

1995-09-01

22

Direct somatic embryogenesis and plant regeneration from leaf, petiole, and stem explants of Golden Pothos  

Microsoft Academic Search

Somatic embryos directly formed at cut edges or on the surface of leaf explants, around cut ends or along side surfaces of petiole and stem explants of ‘Golden Pothos’ [ Epipremnum aureum (Linden & Andre) Bunt.] on Murashige and Skoog (MS) medium supplemented with N-(2-chloro-4-pyridyl)- N?-phenylurea (CPPU) or N-phenyl- N?-1, 2, 3-thiadiazol-5-ylurea (TDZ) with ?-naphthalene acetic acid (NAA) and a

Q. Zhang; J. Chen; R. J. Henny

2005-01-01

23

Antioxidant activities of the essential oils and methanol extracts from myrtle ( Myrtus communis var. italica L.) leaf, stem and flower  

Microsoft Academic Search

This study was designed to examine the chemical composition and antioxidant activity of the essential oils and methanol extracts of Myrtus communis var. italica L. leaf, stem and flower. Myrtle leaf and flower were the valuable organs for the essential oil production representing a yield of 0.61% and 0.30% (w\\/w), respectively. The essential oil composition of myrtle leaf and flower

Wissem Aidi Wannes; Baya Mhamdi; Jazia Sriti; Mariem Ben Jemia; Olfa Ouchikh; Ghaith Hamdaoui; Mohamed Elyes Kchouk; Brahim Marzouk

2010-01-01

24

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

25

Mammary stem cell number as a determinate of breast cancer risk  

Microsoft Academic Search

The 'cancer stem cell hypothesis' posits that cancers, including breast cancer, arise in tissue stem or progenitor cells. If this is the case, then it follows that the risk for developing breast cancer may be determined in part by the number of breast stem\\/progenitor cells that can serve as targets for transformation. Stem cell number may be set during critical

Christophe Ginestier; Max S Wicha

2007-01-01

26

Identification and mapping of leaf, stem and stripe rust resistance quantitative trait loci and their interactions in durum wheat.  

PubMed

Leaf rust (Puccinia triticina Eriks.), stripe rust (Puccinia striiformis f. tritici Eriks.) and stem rust (Puccinia graminis f. sp. tritici) cause major production losses in durum wheat (Triticum turgidum L. var. durum). The objective of this research was to identify and map leaf, stripe and stem rust resistance loci from the French cultivar Sachem and Canadian cultivar Strongfield. A doubled haploid population from Sachem/Strongfield and parents were phenotyped for seedling reaction to leaf rust races BBG/BN and BBG/BP and adult plant response was determined in three field rust nurseries near El Batan, Obregon and Toluca, Mexico. Stripe rust response was recorded in 2009 and 2011 nurseries near Toluca and near Njoro, Kenya in 2010. Response to stem rust was recorded in field nurseries near Njoro, Kenya, in 2010 and 2011. Sachem was resistant to leaf, stripe and stem rust. A major leaf rust quantitative trait locus (QTL) was identified on chromosome 7B at Xgwm146 in Sachem. In the same region on 7B, a stripe rust QTL was identified in Strongfield. Leaf and stripe rust QTL around DArT marker wPt3451 were identified on chromosome 1B. On chromosome 2B, a significant leaf rust QTL was detected conferred by Strongfield, and at the same QTL, a Yr gene derived from Sachem conferred resistance. Significant stem rust resistance QTL were detected on chromosome 4B. Consistent interactions among loci for resistance to each rust type across nurseries were detected, especially for leaf rust QTL on 7B. Sachem and Strongfield offer useful sources of rust resistance genes for durum rust breeding. PMID:23396999

Singh, A; Pandey, M P; Singh, A K; Knox, R E; Ammar, K; Clarke, J M; Clarke, F R; Singh, R P; Pozniak, C J; Depauw, R M; McCallum, B D; Cuthbert, R D; Randhawa, H S; Fetch, T G

2012-10-20

27

[Allelopathic effect of Nelumbo nucifera stem and leaf tissue extract on the growth of Microcystis aeruginosa and Scenedesmus quadricanda].  

PubMed

Effects of Nelumbo nucifera stem and leaf tissue extract on the growth of Microcystis aeruginosa and Scenedesmus quadricanda were studied to verify its potential in entriphication control. Five concentrations of Nelumbo nucifera stem and leaf tissue extract were chosen to compare their inhibitory effects on the growth of Microcystis aeruginosa and Scenedesmus quadricanda. The result showed that the leaf extract inhibited the algae bloom more effectively than the stem extract on the whole. When the leaf extract normality was 25 g x L(-1), the highest inhibition rate of Microcystis aeruginosa and Scenedesmus quadricanda was 71.33% and 78.14%, respectively, while for the stem extract, the values were 49.78% and 52.14%. Propanamide was found in both the stem and leaf tissue extracts of Nelumbo nucifera by GC-MS analysis, with concentrations of 1.1 mg x L(-1) and 0.2 mg x L(-1), respectively. The EC50 values of the two kinds of algae were calculated by the probability method. PMID:24027993

He, Lian-Sheng; Meng, Fan-Li; Diao, Xiao-Jun; Li, Yi-Wei; Meng, Rui; Xi, Bei-Dou; Shu, Jian-Min

2013-07-01

28

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

29

Direct somatic embryogenesis and plant regeneration from leaf, petiole, and stem explants of Golden Pothos.  

PubMed

Somatic embryos directly formed at cut edges or on the surface of leaf explants, around cut ends or along side surfaces of petiole and stem explants of 'Golden Pothos' [Epipremnum aureum (Linden & Andre) Bunt.] on Murashige and Skoog (MS) medium supplemented with N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) or N-phenyl-N'-1, 2, 3-thiadiazol-5-ylurea (TDZ) with alpha-naphthalene acetic acid (NAA) and a medium called MK containing MS salts with Kao's vitamins, supplemented with 2.0 mg/l TDZ and 0.2 mg/l NAA. Somatic embryos were also produced on MS medium containing 2.0 mg/l kinetin (KN) and 0.5 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) from leaf and petiole explants, MS medium supplemented with 2.0 mg/l CPPU and 0.5 mg/l 2,4-D from petiole and stem explants, and 2.0 mg/l TDZ and 0.2 mg/l or 0.5 mg/l 2,4-D from stem explants. In addition, somatic embryos occurred from stem explants on Chu's N6 medium containing 2.0 mg/l CPPU and 0.2 mg/l NAA. Somatic embryos matured and grew into multiple buds, shoots, or even plantlets after 2-3 months on the initial culture medium. Germination was optimal on MS medium containing either 2 mg/l 6-benzylaminopurine (BA) and 0.2 mg/l NAA or 2 mg/l zeatin and 0.2 mg/l NAA. Shoots elongated better and roots developed well on MS medium with no growth regulators. Approximately 30-100 plantlets were regenerated from each explant. The regenerated plants grew vigorously after transplanting to a soil-less container substrate in a shaded greenhouse. PMID:15688236

Zhang, Q; Chen, J; Henny, R J

2004-11-16

30

Identification and characterization of Apple stem grooving virus causing leaf distortion on pear ( Pyrus pyrifolia ) in Taiwan  

Microsoft Academic Search

A putative virus-induced disease of pear (Pyrus pyrifolia var. Hengshen) showing symptoms of reduced size of foliage and leaf distortion was observed in orchards in central Taiwan\\u000a in 2004. The sap of symptomatic leaf samples reacted positively to an antiserum against Apple stem grooving virus (ASGV). Two virus cultures, designated as TS1 and TS2, were isolated from symptomatic pears. Flexuous

Zhong-Bin Wu; You-Xiu Zheng; Chiou-Chu Su; Chung-Jan Chang; Fuh-Jyh Jan

2010-01-01

31

Separating soil and leaf water 18O isotopic signals in plant stem cellulose  

NASA Astrophysics Data System (ADS)

The oxygen-18 signal of soil and leaf water are both recorded in heterotrophically synthesized plant stem cellulose. Presently, these signals can only be teased apart with modeling and assumptions on the nature of the isotopic enrichment of leaf water. A method by which these two signals are chemically separated and analyzed is tested here. Heterotrophically synthesized cellulose from germinating seeds having a mixture of isotopic signals from the reserve carbohydrate (starch) and that of the water during cellulose synthesis was hydrolyzed and the resulting glucose converted to glucose phenylosazone. The analysis of the 18O/ 16O ratios of cellulose and of glucose phenylosazone were used to calculate the oxygen isotope ratio of the oxygen attached to the second carbon of the glucose moieties of the cellulose molecule. The calculated ? 18O value of this oxygen was highly correlated with that of the water available for cellulose synthesis showing a nearly one-to-one relationship (slope = 1.027) and leading to the conclusion that it completely exchanges with water during heterotrophic cellulose synthesis. Once this method is refined so as to increase precision, it will be possible to derive the ? 18O values of soil water available to plants from the oxygen isotope analysis of stem cellulose and its derivative.

Sternberg, Leonel da Silveira Lobo; Anderson, William T.; Morrison, Kanema

2003-07-01

32

Estimation of leaf number and leaf area of hydroponic pak-choi plants ( Brassica campestns ssp, chinensis ) using growing degree-days  

Microsoft Academic Search

Temperature is a principal environmental factor that directly affects the growth and timing of appearance for crop leaves.\\u000a To estimate the leaf number and leaf area of ‘Seoul’ pak-choi plants (Brassica campestns ssp.chinensis), we applied the concept of growing degree-days GDD=(Tavg-Tbase) × days, where Tavg, Tbase and days were the daily average air temperature, base temperature, and days after transplanting,

Young Yeol Cho; Jung Eek Son

2007-01-01

33

Antioxidant and antimicrobial properties of Moltkia petraea (Tratt.) Griseb. flower, leaf and stem infusions.  

PubMed

Antioxidant and antimicrobial activities as well as the quantity of phenolic substances (total phenol, flavonoid and phenolic acid contents) were determined in aqueous extracts of leaves, stems and flowers of Moltkia petraea (Tratt.) Griseb. from two mountainous localities (Sveti Jure and Snijeznica) in Croatia. In addition, the profile of phenolic acids was analyzed by UPLC-MS/MS. Antioxidant activities of all extracts in different test systems, namely the DPPH radical scavenging, reducing power assay and chelating activity, increased with extract concentration. Activity of the extracts from Snijeznica in beta-carotene-linoleic acid assay did not differ from the activity of standard, BHA. The leaf extracts from Snijeznica demonstrated superior antioxidant activity in most of the assays, while the stem extract from the same locality was the most effective Fe(2+) ion chelator. In general, the extracts from Snijeznica were more effective antioxidants than the corresponding extracts from Sveti Jure. The aqueous extracts of M. petraea did not show antimicrobial activity against bacteria and fungi tested in the diffusion and dilution assays. PMID:20304028

Konci?, M Zovko; Kremer, D; Gruz, J; Strnad, M; Bisevac, G; Kosalec, I; Samec, D; Piljac-Zegarac, J; Karlovi?, K

2010-03-19

34

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

PubMed

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 alkaline phosphatase in various tissues of the vector snail Lymnaea acuminata in time and dose dependent manner. Euphorbia hirta (family-Euphorbiaceae) commonly known as Dudhi, is a common medicinal plant of India, which is used in variety of diseases i.e. cough, asthma, colic, dysentery, genito urinary diseases. PMID:15722098

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

2004-12-15

35

Sedative effects of Arachis hypogaea L. stem and leaf extracts on sleep-deprived rats  

PubMed Central

Arachis hypogaea L. stem and leaf extracts (AHSLE) are reputed to aid sleep. The purpose of this study was to evaluate the sedative effects of AHSLE on sleep-deprived (SD) rats and the effect on energy system pathways. Furthermore, we analyzed the essential oil components of Arachis hypogaea L. stems and leaves (AHSL) to explain the sedative effects. AHSLE were obtained by extracting AHSL twice with water at 98°C for 3 h. Animal experiments were performed in the Laboratory Animal Resource Center, University of Tsukuba, Japan, and the levels of neurotransmitters were analyzed by high performance liquid chromatography (HPLC). The essential oil of the AHSL was obtained by simultaneous distillation and extraction (SDE) and analyzed by gas chromatography-mass spectrometry (GC-MS). Following treatment with AHSLE, the adenosine triphosphate (ATP) levels of the SD rats increased, which is a different effect from that previously observed in freely behaving rats. Adenosine (Ad) were not elevated by AHSLE uniformly throughout the brain, but accumulated in site-specific and time-prolonged manners. Following GC-MS analysis of the AHSL essential oil, a total of 37 compounds were identified; the major components were linalool (16.17%, which has sedative-like activity), n-hexadecanoic acid (16.42%), and 1-octen-3-ol (8.48%; a product of linalool decomposition). AHSLE affect the target neurotransmitters related to the rat circadian rhythms in specific brain regions, suggesting that AHSLE have the potential to increase sleep during the SD phase, and the sedative effects of AHSLE may be due to high levels of linalool and its decomposition products. AHSLE are potentially useful as sedatives or sleep aids in hypnotic therapy.

ZU, XIAOYAN; ZHANG, ZHENYA; XIONG, GUANGQUAN; LIAO, TAO; QIAO, YU; LI, YITING; GENG, SHENGRONG; LI, XIN

2013-01-01

36

Rhythmic Stem Extension Growth and Leaf Movements as Markers of Plant Behaviour: the Integral Output from Endogenous and Environmental Signals  

Microsoft Academic Search

With the model systems Chenopodium rubrum (short-day plant) and Chenopodium murale (long-day plant), growth and behaviour have been studied in response to photo- and thermoperiod. With time-lapse photography, rhythmic integration of the plant as a whole could be monitored. Upon photoperiodic flower initiation, rhythmic stem extension rate (SER) and leaf movement (LM) change their phase relationship in a specific way.

Johannes Normann; Marco Vervliet-Scheebaum; Jolana Albrechtová; Edgar Wagner

37

Phenolic contents and antioxidant activities of bitter gourd ( Momordica charantia L.) leaf, stem and fruit fraction extracts in vitro  

Microsoft Academic Search

Bitter gourd (Momordica charantia L.) has long been regarded as a food and medicinal plant. We investigated the antioxidant activity of the water extract of leaf, stem and fruit fractions by several in vitro systems of assay, namely DPPH radical-scavenging activity, hydroxyl radical-scavenging activity, ?-carotene–linoleate bleaching assay, ferric reducing\\/antioxidant power (FRAP) assay and total antioxidant capacity. Total phenolic content was

Jittawan Kubola; Sirithon Siriamornpun

2008-01-01

38

Arabidopsis REGULATOR OF AXILLARY MERISTEMS1 Controls a Leaf Axil Stem Cell Niche and Modulates Vegetative Development[W  

PubMed Central

Shoot branching is a major determinant of variation in plant stature. Branches, which form secondary growth axes, originate from stem cells activated in leaf axils. The initial steps by which axillary meristems (AMs) are specified and their stem cells organized are still poorly understood. We identified gain- and loss-of-function alleles at the Arabidopsis thaliana REGULATOR OF AXILLARY MERISTEMS1 (RAX1) locus. RAX1 is encoded by the Myb-like transcription factor MYB37 and is an Arabidopsis homolog of the tomato (Solanum lycopersicum) Blind gene. RAX1 is transiently expressed in a small central domain within the boundary zone separating shoot apical meristem and leaf primordia early in leaf primordium development. RAX1 genetically interacts with CUP-SHAPED COTYLEDON (CUC) genes and is required for the expression of CUC2 in the RAX1 expression domain, suggesting that RAX1 acts through CUC2. We propose that RAX1 functions to positionally specify a stem cell niche for AM formation. RAX1 also affects the timing of developmental phase transitions by negatively regulating gibberellic acid levels in the shoot apex. RAX1 thus defines a novel activity that links the specification of AM formation with the modulation of the rate of progression through developmental phases.

Keller, Thomas; Abbott, Jessica; Moritz, Thomas; Doerner, Peter

2006-01-01

39

Anti-hyperglycemic and antinociceptive activity of methanol leaf and stem extract of Nypa fruticans Wurmb.  

PubMed

Nypa fruticans Wurmb. (Arecaceae) is a mangrove palm well-known for its traditional uses by the local practitioners against different ailments in southern regions of Bangladesh. However, the plant is yet to be scientifically studied. The present study was done to evaluate the anti-hyperglycemic and antinociceptive potential of methanolic extract of leaf and stem of Nypa fruticans Wurmb. (MENF). The anti-hyperglycemic activity was tested on glucose loaded hyperglycemic mice whereas antinociceptive activity was evaluated using a model of acetic acid-induced writhing in mice. The crude MENF was found to show significant oral anti-hyperglycemic activity on glucose loaded mice at every dose. Maximum anti-hyperglycemic activity was observed at a dose of 500 mg MENF/kg body weight, which was more than what was obtained with a standard drug glibenclamide at a dose of 10 mg glibenclamide/kg body weight). Significant antinociceptive activity was also demonstrated by MENF in acetic acid-induced writhing mice model. The extract caused a maximum of 39.88% (p<0.001) inhibition of writhing at the dose of 600 mg/kg body weight, which was better than the result obtained with a standard drug (200 mg aspirin/kg body weight, 49.34% inhibition). These findings indicate that MENF has significant anti-hyperglycemic and antinociceptive activity and thus have great potential as a source of natural products. PMID:21959809

Reza, Hasan; Haq, Wahid Mozammel; Das, Asish K; Rahman, Shahnaz; Jahan, Rownak; Rahmatullah, Mohammed

2011-10-01

40

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

41

Extensive genomic copy number variation in embryonic stem cells  

Microsoft Academic Search

Recent analysis of the human and mouse genomes has revealed that highly identical duplicated elements account for >5% of the sequence content. These elements vary in copy number between individuals. Copy number variations (CNVs) contribute significantly to genetic differences among individuals and are increasingly recognized as a causal factor in human diseases with different etiologies. In inbred mouse strains, CNVs

Qi Liang; Nathalie Conte; William C. Skarnes; Allan Bradley

2008-01-01

42

The ratio of leaf to total photosynthetic area influences shade survival and plastic response to light of green-stemmed leguminous shrub seedlings.  

PubMed

Different plant species and organs within a plant differ in their plastic response to light. These responses influence their performance and survival in relation to the light environment, which may range from full sunlight to deep shade. Plasticity, especially with regard to physiological features, is linked to a greater capacity to exploit high light and is usually low in shade-tolerant species. Among photosynthetic organs, green stems, which represent a large fraction of the total photosynthetic area of certain species, are hypothesized to be less capable of adjustment to light than leaves, because of biomechanical and hydraulic constraints. The response to light by leaves and stems of six species of leguminous, green-stemmed shrubs from dry and high-light environments was studied by growing seedlings in three light environments: deep shade, moderate shade and sun (3, 30 and 100 % of full sunlight, respectively). Survival in deep shade ranged from 2 % in Retama sphaerocarpa to 74 % in Ulex europaeus. Survival was maximal at moderate shade in all species, ranging from 80 to 98 %. The six species differed significantly in their ratio of leaf to total photosynthetic area, which influenced their light response. Survival in deep shade increased significantly with increasing ratio of leaf to total photosynthetic area, and decreased with increasing plasticity in net photosynthesis and dark respiration. Responses to light differed between stems and leaves within each species. Mean phenotypic plasticity for the variables leaf or stem specific mass, chlorophyll content, chlorophyll a/b ratio, and carotenoid to chlorophyll ratio of leaves, was inversely related to that of stems. Although mean plasticity of stems increased with the ratio of leaf to total photosynthetic area, the mean plasticity of leaves decreased. Shrubs with green stems and a low ratio of leaf to total photosynthetic area are expected to be restricted to well-lit habitats, at least during the seedling stage, owing to their inefficient light capture and the low plasticity of their stems. PMID:12646502

Valladares, Fernando; Hernández, Libertad G; Dobarro, Iker; García-Pérez, Cristina; Sanz, Rubén; Pugnaire, Francisco I

2003-04-01

43

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

44

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

PubMed

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. PMID:24049413

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

2013-01-01

45

Phytochemical analysis and antimicrobial activities of methanolic extracts of leaf, stem and root from different varieties of Labisa pumila Benth.  

PubMed

A local herb, Kacip Fatimah, is famous amongst Malay women for its uses in parturition; however, its phytochemical contents have not been fully documented. Therefore, a study was performed to evaluate the phenolics, flavonoids, and total saponin contents, and antibacterial and antifungal properties of the leaf, stem and root of three varieties of Labisia pumila Benth. Total saponins were found to be higher in the leaves of all three varieties, compared to the roots and stems. Leaves of var. pumila exhibited significantly higher total saponin content than var. alata and lanceolata, with values of 56.4, 43.6 and 42.3 mg diosgenin equivalent/g dry weight, respectively. HPLC analyses of phenolics and flavonoids in all three varieties revealed the presence of gallic acid, caffeic acid, rutin, and myricetin in all plant parts. Higher levels of flavonoids (rutin, quercitin, kaempferol) were observed in var. pumila compared with alata and lanceolata, whereas higher accumulation of phenolics (gallic acid, pyrogallol) was recorded in var. alata, followed by pumila and lanceolata. Antibacterial activities of leaf, stem and root extracts of all varieties determined against both Gram positive (Micrococcus luteus, Bacillus subtilis B145, Bacillus cereus B43, Staphylococcus aureus S1431) and Gram negative (Enterobacter aerogenes, Klebsiella pneumonia K36, Escherichia coli E256, Pseudomonas aeruginosa PI96) pathogens showed that crude methanolic extracts are active against these bacteria at low concentrations, albeit with lower antibacterial activity compared to kanamycin used as the control. Antifungal activity of methanolic extracts of all plant parts against Fusarium sp., Candida sp. and Mucor using the agar diffusion disc exhibited moderate to appreciable antifungal activities compared to streptomycin used as positive control. PMID:21623314

Karimi, Ehsan; Jaafar, Hawa Z E; Ahmad, Sahida

2011-05-27

46

Antifungal Activity of Leaf and Stem Extracts from Various Plant Species on the Incidence of Colletotrichum gloeosporioides of Papaya and Mango Fruit After Storage  

Microsoft Academic Search

Bautista-Baños, S., Barrera-Necha, L.L., Bravo-Luna, L., and Bermudez-Torres, K. 2002. Antifungal activity of leaf and stem extracts from various plant species on the incidence of Colletotrichum gloeosporioides of papaya and mango fruit after storage. Revista Mexicana de Fitopatología 20:8-12. Aqueous extracts of leaves and stems of Achras sapota, Annona reticulata, Bromelia hemisphaerica, Carica papaya, Citrus limon, Chrysophylum cainito, Dyospiros ebenaster,

Silvia Bautista-Baños; Laura Leticia Barrera-Necha; Leticia Bravo-Luna

2002-01-01

47

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

2013-05-29

48

Chemical Composition and Antimicrobial Characteristic of the Essential Oils Obtained from the Flower, Leaf and Stem of Salvia officinalis L. Originating from Southeast Serbia  

Microsoft Academic Search

A comparison of the yield, chemical composition and antimicrobial action of the essential oils obtained from the flower, leaf and stem of Salvia officinalis L., originating from the southeast region of Serbia was carried out. The oils were obtained by different procedures of distillation (water and steam distillation). Water distillation contributed to a larger oil yield from all parts of

Dragan T. Velickovic; Mihailo S. Ristic; Novica V. Randjelovic; Andrija A. Smelcerovic

2002-01-01

49

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

50

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

2013-09-04

51

Changes in chloroplast number per cell during leaf development in spinach  

Microsoft Academic Search

The amounts of chlorophyll and nitrogen and the numbers of cells per unit area change as the green leaves of spinach plants grow and increase in size in the light. The changes in the numbers of chloroplasts per cell were measured by a new method. A 5-fold increase in the numbers of chloroplasts per cell took place in both palisade

J. V. Possingham; W. Saurer

1969-01-01

52

Net photosynthesis, dark respiration, specific leaf weight, and growth of young apple trees as influenced by light regime  

Microsoft Academic Search

Eight different light treatments did not affect shoot length, leaf number, or total leaf area of young Red Yorking apple (Malus pumila Mill.) trees grown in a greenhouse. Dry weights of leaves and stems were suppressed by 80% shade. Net photosynthesis Pn, dark respiration (Rd), and specific leaf weight (SLW) were higher in sun than in shade leaves and adaptations

Barden

1974-01-01

53

Asymmetric leaves1 mediates leaf patterning and stem cell function in Arabidopsis  

Microsoft Academic Search

Meristem function in plants requires both the maintenance of stem cells and the specification of founder cells from which lateral organs arise. Lateral organs are patterned along proximodistal, dorsoventral and mediolateral axes. Here we show that the Arabidopsis mutant asymmetric leaves1 (as1) disrupts this process. AS1 encodes a myb domain protein, closely related to PHANTASTICA in Antirrhinum and ROUGH SHEATH2

Mary E. Byrne; Ross Barley; Mark Curtis; Juana Maria Arroyo; Maitreya Dunham; Andrew Hudson; Robert A. Martienssen

2000-01-01

54

Genetic variation in leaf and stem glucosinolates in resynthesized lines of winter rapeseed ( Brassica napus L.)  

Microsoft Academic Search

Glucosinolates are secondary components characteristic for the Brassicaceae with complex biological functions. Glucosinolates\\u000a in the seeds are anti-nutritive when feeding animals and their inheritance have been extensively investigated. Much less is\\u000a known about the genetics of glucosinolates in leaves and stems, which may attract some insects, while repelling others. They\\u000a may also inhibit bacterial processes of importance when using green

Stijn CleemputHeiko; Heiko C. Becker

55

Antioxidant and antimicrobial properties of Moltkia petraea (Tratt.) Griseb. flower, leaf and stem infusions  

Microsoft Academic Search

Antioxidant and antimicrobial activities as well as the quantity of phenolic substances (total phenol, flavonoid and phenolic acid contents) were determined in aqueous extracts of leaves, stems and flowers of Moltkia petraea (Tratt.) Griseb. from two mountainous localities (Sveti Jure and Sniježnica) in Croatia. In addition, the profile of phenolic acids was analyzed by UPLC–MS\\/MS. Antioxidant activities of all extracts

M. Zovko Kon?i?; D. Kremer; J. Gruz; M. Strnad; G. Biševac; I. Kosalec; D. Šamec; J. Piljac-Žegarac; K. Karlovi?

2010-01-01

56

Organogenesis in callus derived from stem and leaf tissues of apple and cherry rootstocks  

Microsoft Academic Search

Callus formation from stem internodes of the apple rootstocks M.9, M.25, M.26, M.27 and the cherry rootstock Colt, and from pith of Nicotiana tabacum cv. Wisconsin 38 was initiated on 4 a-naphthaleneacetic acid (NAA)-based media (2.0–10.0 mg1-1). Transfer of callus to corresponding media lacking NAA allowed regeneration of shoots from callus of M.25, M.27, Colt and tobacco but not of

David J. James; Andrew J. Passey; Suman B. Malhotra

1984-01-01

57

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

58

Genetic analysis of Na(+) and K (+) concentrations in leaf and stem as physiological components of salt tolerance in Tomato.  

PubMed

The sodium and potassium concentrations in leaf and stem have been genetically studied as physiological components of the vegetative and reproductive development in two populations of F(8) lines, derived from a salt sensitive genotype of Solanum lycopersicum cv. Cerasiforme, as female parent, and two salt tolerant lines, as male parents, from S. pimpinellifolium, the P population (142 lines), and S. cheesmaniae, the C population (116 lines). Genetic parameters of ten traits under salinity and five of them under control conditions were studied by ANOVA, correlation, principal component and QTL analysis to understand the global response of the plant. Two linkage maps including some tomato flowering time and salt tolerance candidate genes encoding for SlSOS1, SlSOS2, SlSOS3, LeNHX1, LeNHX3, were used for the QTL detection. Thirteen and 20 QTLs were detected under salinity in the P and C populations, respectively, and four under control conditions. Highly significant and contributing QTLs (over 40%) for the concentrations of Na(+) and K(+) in stems and leaves have been detected on chromosome 7 in both the populations. This is the only genomic position where the concentration QTLs for both the cations locate together. The proportion of QTLs significantly affected by salinity was larger in the P population (64.3%, including all QTLs detected under control) than in the C population (21.4%), where the estimated genetic component of variance was larger for most traits. A highly significant association between the leaf area and fruit yield under salinity was found only in the C population, which is supported by the location of QTLs for these traits in a common region of chromososome C1. As far as breeding for salt tolerance is concerned, only two sodium QTLs (lnc1.1 and lnc8.1) map in genomic regions of C1 and C8 where fruit yield QTLs are also located but in both the cases the profitable allele corresponds to the salt sensitive, cultivated species. One of those QTLs, lnc1.1 might involve LeNHX3. PMID:18251001

Villalta, I; Reina-Sánchez, A; Bolarín, M C; Cuartero, J; Belver, A; Venema, K; Carbonell, E A; Asins, M J

2008-02-05

59

Organ-specific and dosage-dependent expression of a leaf/stem specific gene from potato after tagging and transfer into potato and tobacco plants.  

PubMed Central

ST-LS1, a single copy gene from potato displaying a leaf/stem specific gene expression, was tagged by an exon modification and introduced into both potato and tobacco cells using Agrobacterium vectors. After regeneration of whole plants, the expression of the tagged gene was analyzed with respect to its organ specificity and compared to the expression of the corresponding resident gene. The expression of the transferred gene in transgenic plants closely followed the expression of the resident gene. No marked influence of the plant species serving as host was observed. The level of expression of the introduced gene varied by a factor of at least 100 in independent transformants when normalized to the expression of the resident gene. Southern analysis performed on the transformed plants indicated a correlation between copy number of the introduced gene and its expression level. The activity of the tagged gene as well as of the resident gene was significantly inhibited by treatment of the transgenic plants with the herbicide norfluorazon, indicating that this gene activity is dependent on the presence of functional chloroplasts in the leaves. Images

Stockhaus, J; Eckes, P; Blau, A; Schell, J; Willmitzer, L

1987-01-01

60

Composition of the leaf, stem bark and root bark oils of Isolona cooperi investigated by GC (retention index), GC-MS and 13C-NMR spectroscopy.  

PubMed

The leaf, stem bark and root bark oils of Isolona cooperi Hutchinson & Dalziel from the Ivory Coast have been analysed by GC (retention index), GC-MS and 13C-NMR spectroscopy. Two types of essential oil were produced by the plant. The leaf and stem bark oils were monoterpene-rich, containing principally (Z)-beta-ocimene and gamma-terpinene and three lactones, 5-[(E and Z)-hexylidene]-5H-furan-2-ones and massoia lactone, were present in appreciable amounts. Conversely, the root bark oil was dominated by 5-isopentenylindole and (E)-beta-caryophyllene. The strategy for the analysis of each oil was adapted according to the nature of the components. PMID:16223093

Boti, Jean Brice; Koukoua, Gérard; N'Guessan, Thomas Yao; Muselli, Alain; Bernardini, Antoine-François; Casanova, Joseph

61

Neuroprotection of the leaf and stem of Vitis amurensis and their active compounds against ischemic brain damage in rats and excitotoxicity in cultured neurons  

Microsoft Academic Search

Vitis amurensis (Vitaceae) has been reported to have anti-oxidant and anti-inflammatory activities. The present study investigated a methanol extract from the leaf and stem of V. amurensis for neuroprotective effects on cerebral ischemic damage in rats and on excitotoxicity induced by glutamate in cultured rat cortical neurons. Transient focal cerebral ischemia was induced by 2h middle cerebral artery occlusion followed

Joo Youn Kim; Ha Yeon Jeong; Hong Kyu Lee; SeungHwan Kim; Bang Yeon Hwang; KiHwan Bae; Yeon Hee Seong

62

Transcriptional regulation of the ADP-glucose pyrophosphorylase isoforms in the leaf and the stem under long and short photoperiod in lentil.  

PubMed

ADP-glucose pyrophosphorylase (AGPase) is a key enzyme in plant starch biosynthesis. It contains large (LS) and small (SS) subunits encoded by two different genes. In this study, we explored the transcriptional regulation of both the LS and SS subunits of AGPase in stem and leaf under different photoperiods length in lentil. To this end, we first isolated and characterized different isoforms of the LS and SS of lentil AGPase and then we performed quantitative real time PCR (qPCR) to see the effect of photoperiod length on the transcription of the AGPase isforms under the different photoperiod regimes in lentil. Analysis of the qPCR results revealed that the transcription of different isoforms of the LSs and the SSs of lentil AGPase are differentially regulated when photoperiod shifted from long-day to short-day in stem and leaves. While transcript levels of LS1 and SS2 in leaf significantly decreased, overall transcript levels of SS1 increased in short-day regime. Our results indicated that day length affects the transcription of lentil AGPase isoforms differentially in stems and leaves most likely to supply carbon from the stem to other tissues to regulate carbon metabolism under short-day conditions. PMID:23498860

Seferoglu, Ayse Bengisu; Baris, Ibrahim; Morgil, Hande; Tulum, Isil; Ozdas, Sule; Cevahir, Gul; Kavakli, Ibrahim Halil

2013-02-01

63

Comparative Gene Expression Of Architectural And Nutritional ESTs In Apple Root, Leaf And Stem Tissues  

Technology Transfer Automated Retrieval System (TEKTRAN)

There are number of phenotypic traits conferred by apple rootstock upon the scion and desirable rootstock traits. In an attempt to identify genes which may be responsible for these traits, we have used the public expressed sequences (ESTs and cDNA) to identify genes expressed uniquely in apple roots...

64

Effect of cell number on mesenchymal stem cell transplantation in a canine disc degeneration model.  

PubMed

Transplantation of mesenchymal stem cells (MSCs) inhibits the progression of disc degeneration in animal models. We know of no study to determine the optimal number of cells to transplant into the degenerated intervertebral disc (IVD). To determine the optimal donor cell number for maximum benefit, we conducted an in vivo study using a canine disc degeneration model. Autologous MSCs were transplanted into degenerative discs at 10(5), 10(6), or 10(7)?cells per disc. The MSC-transplanted discs were evaluated for 12 weeks using plain radiography, magnetic resonance imaging, and gross and microscopic evaluation. Preservation of the disc height, annular structure was seen in MSC-transplantation groups compared to the operated control group with no MSC transplantation. Result of the number of remaining transplanted MSCs, the survival rate of NP cells, and apoptosis of NP cells in transplanted discs showed both structural microenvironment and abundant extracellular matrix maintained in 10(6) MSCs transplanted disc, while less viable cells were detected in 10(5) MSCs transplanted and more apoptotic cells in 10(7) MSCs transplanted discs. The results of this study demonstrate that the number of cells transplanted affects the regenerative capability of MSC transplants in experimentally induced degenerating canine discs. It is suggested that maintenance of extracellular matrix by its production from transplanted cells and/or resident cells is important for checking the progression of structural disruption that leads to disc degeneration. PMID:20839317

Serigano, Kenji; Sakai, Daisuke; Hiyama, Akihiko; Tamura, Futoshi; Tanaka, Masahiro; Mochida, Joji

2010-10-01

65

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

66

Microclimatic conditions determined by stem density influence leaf anatomy and leaf physiology of beech ( Fagus sylvatica L.) growing within stands that naturally regenerate from clear-cutting  

Microsoft Academic Search

Beech forests naturally regenerating from clear-cutting can exhibit different microclimates depending on size of saplings\\u000a and stem density. When beech trees are young and stem density is low, the level of radiation inside the ecosystem reaching\\u000a the soil surface is high; consequently, air and soil temperatures rise and the soil water content may decrease. These microclimatic\\u000a parameters presumably will affect

Iván Closa; Juan José Irigoyen; Nieves Goicoechea

2010-01-01

67

Neuroprotection of the leaf and stem of Vitis amurensis and their active compounds against ischemic brain damage in rats and excitotoxicity in cultured neurons.  

PubMed

Vitis amurensis (Vitaceae) has been reported to have anti-oxidant and anti-inflammatory activities. The present study investigated a methanol extract from the leaf and stem of V. amurensis for neuroprotective effects on cerebral ischemic damage in rats and on excitotoxicity induced by glutamate in cultured rat cortical neurons. Transient focal cerebral ischemia was induced by 2h middle cerebral artery occlusion followed by 24h reperfusion (MCAO/reperfusion) in rats. Orally administered V. amurensis (25-100 mg/kg) reduced MCAO/reperfusion-induced infarct and edema formation, neurological deficits, and neuronal death. Depletion of glutathione (GSH) level and lipid peroxidation induced by MCAO/reperfusion was inhibited by administration of V. amurensis. The increase of phosphorylated mitogen-activated protein kinases (MAPKs), cyclooxygenase-2 (COX-2), and pro-apoptotic proteins and the decrease of anti-apoptotic protein in MCAO/reperfusion rats were significantly inhibited by treatment with V. amurensis. Exposure of cultured cortical neurons to 500 ?M glutamate for 12h induced neuronal cell death. V. amurensis (1-50 ?g/ml) and (+)-ampelopsin A, ?-2-viniferin, and trans-?-viniferin isolated from the leaf and stem of V. amurensis inhibited glutamate-induced neuronal death, the elevation of intracellular calcium ([Ca(2+)](i)), the generation of reactive oxygen species (ROS), and changes of apoptosis-related proteins in cultured cortical neurons, suggesting that the neuroprotective effect of V. amurensis may be partially attributed to these compounds. These results suggest that the neuroprotective effect of V. amurensis against focal cerebral ischemic injury might be due to its anti-apoptotic effect, resulting from anti-excitotoxic, anti-oxidative, and anti-inflammatory effects and that the leaf and stem of V. amurensis have possible therapeutic roles for preventing neurodegeneration in stroke. PMID:21778042

Kim, Joo Youn; Jeong, Ha Yeon; Lee, Hong Kyu; Kim, SeungHwan; Hwang, Bang Yeon; Bae, KiHwan; Seong, Yeon Hee

2011-07-20

68

Bone Marrow B cell Precursor Number after Allogeneic Stem Cell Transplantation and GVHD Development  

PubMed Central

Patients without chronic graft-versus-host disease (cGVHD) have robust B cell reconstitution and are able to maintain B cell homeostasis after allogeneic hematopoietic stem cell transplantation (HSCT). To determine whether B lymphopoiesis differs before cGVHD develops, we examined bone marrow (BM) biopsies for terminal deoxynucleotidyl transferase (TdT) and PAX5 immunostaining early post-HSCTat day 30 when all patients have been shown to have high B cell activating factor (BAFF) levels. We found significantly greater numbers of BM B cell precursors in patients who did not develop cGVHD compared with those who developed cGVHD (median = 44 vs 2 cells/high powered field [hpf]; respectively; P < .001). Importantly, a significant increase in precursor B cells was maintained when patients receiving high-dose steroid therapy were excluded (median = 49 vs 20 cells/hpf; P =.017). Thus, we demonstrate the association of BM B cell production capacity in human GVHD development. Increased BM precursor B cell number may serve to predict good clinical outcome after HSCT.

Fedoriw, Yuri; Samulski, T. Danielle; Deal, Allison M.; Dunphy, Cherie H.; Sharf, Andrew; Shea, Thomas C.; Serody, Jonathan S.; Sarantopoulos, Stefanie

2013-01-01

69

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

70

Leaf Development  

PubMed Central

The shoot system is the basic unit of development of seed plants and is composed of a leaf, a stem, and a lateral bud that differentiates into a lateral shoot. The most specialized organ in angiosperms, the flower, can be considered to be part of the same shoot system since floral organs, such as the sepal, petal, stamen, and carpel, are all modified leaves. Scales, bracts, and certain kinds of needle are also derived from leaves. Thus, an understanding of leaf development is critical to an understanding of shoot development. Moreover, leaves play important roles in photosynthesis, respiration and photoperception. Thus, a full understanding of leaves is directly related to a full understanding of seed plants. The details of leaf development remain unclear. The difficulties encountered in studies of leaf development, in particular in dicotyledonous plants such as Arabidopsis thaliana (L.) Henyn., are derived from the complex process of leaf development, during which the division and elongation of cells occur at the same time and in the same region of the leaf primordium (Maksymowych, 1963; Poethig and Sussex, 1985). Thus, we cannot divide the entire process into unit processes in accordance with the tenets of classical anatomy. Genetic approaches in Arabidopsis, a model plant (Meyerowitz and Pruitt, 1985), have provided a powerful tool for studies of mechanisms of leaf development in dicotyledonous plants, and various aspects of the mechanisms that control leaf development have been revealed in recent developmental and molecular genetic studies of Arabidopsis (for reviews, see Tsukaya, 1995 and 1998; Van Lijsebettens and Clarke, 1998; Sinha, 1999; Van Volkenburgh, 1999; Tsukaya, 2000; Byrne et al., 2001; Dengler and Kang, 2001; Dengler and Tsukaya, 2001; Tsukaya, 2001). In this review, we shall examine the information that is currently available about various mechanisms of leaf development in Arabidopsis. Vascular patterning is also an important factor in the determination of leaf shape, and this topic is reviewed in this resource by Turner (see also Dengler and Kang, 2001). The interested reader is also referred to work on the basic characterization of the vascular patterning in foliage leaves of Arabidopsis has been carried out by Candela et al. (1999) and Semiarti et al. (2001). For terminology, see Fig. 1.

Tsukaya, Hirokazu

2002-01-01

71

The impact of copy number variation on local gene expression in mouse hematopoietic stem/progenitor cells  

PubMed Central

The extent to which differences in germ line DNA copy number contribute to natural phenotypic variation is unknown. We analyzed the copy number content of the mouse genome to a sub-10 kb resolution. We identified over 1,300 copy number variant regions (CNVRs), most of which are < 10 kb in length, are found in more than one strain, and, in total, span 3.2% (85 Mb) of the genome. To assess the potential functional impact of copy number variation, we mapped expression profiles of purified hematopoietic stem/progenitor cells, adipose tissue and hypothalamus to CNVRs in cis. Of the more than 600 significant associations between CNVRs and expression profiles, most map to CNVRs outside of the transcribed regions of genes. In hematopoietic stem/progenitor cells, up to 28% of strain-dependent expression variation is associated with copy number variation, supporting the role of germ line CNVs as major contributors to natural phenotypic variation in the laboratory mouse.

Cahan, Patrick; Li, Yedda; Izumi, Masayo; Graubert, Timothy A.

2009-01-01

72

Evidence That Sucrose Loaded into the Phloem of a Poplar Leaf Is Used Directly by Sucrose Synthase Associated with Various ?-Glucan Synthases in the Stem  

PubMed Central

Sucrose (Suc) synthase (SuSy) is believed to function in channeling UDP-Glc from Suc to various ?-glucan synthases. We produced transgenic poplars (Populus alba) overexpressing a mutant form (S11E) of mung bean (Vigna radiata) SuSy, which appeared in part in the microsomal membranes of the stems. Expression of SuSy in these membranes enhanced the incorporation of radioactive Suc into cellulose, together with the metabolic recycling of fructose (Fru), when dual-labeled Suc was fed directly into the phloem of the leaf. This overexpression also enhanced the direct incorporation of the glucosyl moiety of Suc into the glucan backbone of xyloglucan and increased recycling of Fru, although the Fru recycling system for cellulose synthesis at the plasma membrane might differ from that for xyloglucan synthesis in the Golgi network. These findings suggest that some of the Suc loaded into the phloem of a poplar leaf is used directly by SuSys associated with xyloglucan and cellulose synthases in the stem. This may be a key function of SuSy because the high-energy bond between the Glc and Fru moieties of Suc is conserved and used for polysaccharide syntheses in this sink tissue.

Konishi, Teruko; Ohmiya, Yasunori; Hayashi, Takahisa

2004-01-01

73

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

2012-11-18

74

Assessment of Euphorbia hirta L. leaf, flower, stem and root extracts for their antibacterial and antifungal activity and brine shrimp lethality.  

PubMed

The antimicrobial activities of the methanolic extracts of Euphorbia hirta L leaves, flowers, stems and roots were evaluated against some medically important bacteria and yeast using the agar disc diffusion method. Four Gram positive (Staphylococcus aureus, Micrococcus sp., Bacillus subtilis and Bacillus thuringensis), four Gram negative (Escherichia coli, Klebsiella pneumonia, Salmonella typhi and P. mirabilis) and one yeast (Candida albicans) species were screened. Inhibition zones ranged between 16-29 mm. Leaves extract inhibited the growth of all tested microorganisms with large zones of inhibition, followed by that of flowers, which also inhibited all the bacteria except C. albicans. The most susceptible microbes to all extracts were S. aureus and Micrococcus sp. Root extract displayed larger inhibition zones against Gram positive bacteria than Gram negative bacteria and had larger inhibition zones compared to stem extract. The lowest MIC values were obtained with E. coli and C. albicans (3.12 mg/mL), followed by S. aureus (12.50 mg/mL) and P. mirabilis (50.00 mg/mL). All the other bacteria had MIC values of 100.00 mg/mL. Scanning Electron Microscopic (SEM) studies revealed that the cells exposed to leaf extract displayed a rough surface with multiple blends and invaginations which increased with increasing time of treatment, and cells exposed to leaf extract for 36 h showed the most damage, with abundant surface cracks which may be related to final cell collapse and loss of function. Time-kill assay of C. albicans indicated a primarily fungicidal effect at 1- and 2-fold MIC. E. hirta extracts had LC(50) values of 0.71, 0.66, 0.41 and 0.03 mg/mL for stems, leaves, roots and flowers, respectively against Artemia salina. Hence, these plants can be used to discover new bioactive natural products that may serve as leads in the development of new pharmaceuticals. PMID:20877206

Rajeh, Mohammad Abu Basma; Zuraini, Zakaria; Sasidharan, Sreenivasan; Latha, Lachimanan Yoga; Amutha, Santhanam

2010-08-31

75

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

76

Phenolic acids and flavonoids in leaf and floral stem of cultivated and wild Cynara cardunculus L. genotypes  

Microsoft Academic Search

Ten genotypes, cultivated and wild of Cynara cardunculus L. were evaluated for their content of phenolic acids, flavonoids and their antioxidant activity. The major compounds present in the leaf were luteolin derivatives in globe artichoke and apigenin derivatives in wild and cultivated cardoon. Apart from ‘Cimiciusa di Mazzarino’ (var. scolymus), caffeoylquinic acids represent the main phenolic compounds in the floral

Gaetano Pandino; Sara Lombardo; Giovanni Mauromicale; Gary Williamson

2011-01-01

77

Composition and Antimicrobial Activity of Cymbopogon giganteus (Hochst.) Chiov. Essential Flower, Leaf and Stem Oils from Cameroon  

Microsoft Academic Search

The essential oils of fresh flowers (2 samples), leaves and stems of Cymbopogon giganteus (Hochst.) Chiovenda from Cameroon were investigated by GC and GC\\/MS. More than 55 components have been identified in the samples 1 (flowers 1), 2 (leaves), 3 (stems) and 4 (flowers 2) with main compounds possessing the p-menthadiene skeleton as follows: cis-p-mentha-1(7),8-dien-2-ol (1: 22.8%, 2: 27.7%, 3:

Leopold Jirovetz; Gerhard Buchbauer; Gernot Eller; Martin Benoit Ngassoum; Pierre M. Maponmetsem

2007-01-01

78

Are lianas more drought-tolerant than trees? A test for the role of hydraulic architecture and other stem and leaf traits.  

PubMed

Lianas are an important component of Neotropical forests, where evidence suggests that they are increasing in abundance and biomass. Lianas are especially abundant in seasonally dry tropical forests, and as such it has been hypothesized that they are better adapted to drought, or that they are at an advantage under the higher light conditions in these forests. However, the physiological and morphological characteristics that allow lianas to capitalize more on seasonal forest conditions compared to trees are poorly understood. Here, we evaluate how saplings of 21 tree and liana species from a seasonal tropical forest in Panama differ in cavitation resistance (P50) and maximum hydraulic conductivity (K(h)), and how saplings of 24 tree and liana species differ in four photosynthetic leaf traits (e.g., maximum assimilation and stomatal conductance) and six morphological leaf and stem traits (e.g., wood density, maximum vessel length, and specific leaf area). At the sapling stage, lianas had a lower cavitation resistance than trees, implying lower drought tolerance, and they tended to have a higher potential hydraulic conductivity. In contrast to studies focusing on adult trees and lianas, we found no clear differences in morphological and photosynthetic traits between the life forms. Possibly, lianas and trees are functionally different at later ontogenetic stages, with lianas having deeper root systems than trees, or experience their main growth advantage during wet periods, when they are less vulnerable to cavitation and can achieve high conductivity. This study shows, however, that the hydraulic characteristics and functional traits that we examined do not explain differences in liana and tree distributions in seasonal forests. PMID:23277211

van der Sande, Masha T; Poorter, Lourens; Schnitzer, Stefan A; Markesteijn, Lars

2013-01-01

79

A basal gradient of Wnt and stem-cell number influences regional tumour distribution in human and mouse intestinal tracts  

PubMed Central

Objective Wnt signalling is critical for normal intestinal development and homeostasis. Wnt dysregulation occurs in almost all human and murine intestinal tumours and an optimal but not excessive level of Wnt activation is considered favourable for tumourigenesis. The authors assessed effects of pan-intestinal Wnt activation on tissue homeostasis, taking into account underlying physiological Wnt activity and stem-cell number in each region of the bowel. Design The authors generated mice that expressed temporally controlled, stabilised ?-catenin along the crypt–villus axis throughout the intestines. Physiological Wnt target gene activity was assessed in different regions of normal mouse and human tissue. Human intestinal tumour mutation spectra were analysed. Results In the mouse, ?-catenin stabilisation resulted in a graduated neoplastic response, ranging from dysplastic transformation of the entire epithelium in the proximal small bowel to slightly enlarged crypts of non-dysplastic morphology in the colorectum. In contrast, stem and proliferating cell numbers were increased in all intestinal regions. In the normal mouse and human intestines, stem-cell and Wnt gradients were non-identical, but higher in the small bowel than large bowel in both species. There was also variation in the expression of some Wnt modulators. Human tumour analysis confirmed that different APC mutation spectra are selected in different regions of the bowel. Conclusions There are variable gradients in stem-cell number, physiological Wnt activity and response to pathologically increased Wnt signalling along the crypt-villus axis and throughout the length of the intestinal tract. The authors propose that this variation influences regional mutation spectra, tumour susceptibility and lesion distribution in mice and humans.

Rodenas-Cuadrado, Pedro; Howarth, Kimberley; Lewis, Annabelle; Mallappa, Sreelakshmi; Segditsas, Stefania; Davis, Hayley; Jeffery, Rosemary; Rodriguez-Justo, Manuel; Keshav, Satish; Travis, Simon P L; Graham, Trevor A; East, James; Clark, Susan; Tomlinson, Ian P M

2013-01-01

80

Determination of the Photoperiod-Sensitive Inductive Phase in Maize with Leaf Numbers and Morphologies of Stem Apical Meristem  

Microsoft Academic Search

It is vital to determine the effective photoperiods of maize for making full use of tropical germplasm, which is the foundation for determining the effect of latitude and planting date on the development of photoperiod-sensitive maize cultivars. The objective of this study is to determine the photoperiod-sensitive inductive phase using reciprocal transfer between long-day (LD) (15 h d-1) and short-day

Lian-cheng WU; Tie-gu WANG; Li-xia KU; Qun-ce HUANG; Zhao-hui SUN; Zhong-liang XIA; Yan-hui CHEN

2008-01-01

81

Osmotic adjustment and the inhibition of leaf, root, stem and silk growth at low water potentials in maize  

Microsoft Academic Search

The expansion growth of plant organs is inhibited at low water potentials (?w), but the inhibition has not been compared in different organs of the same plant. Therefore, we determined elongation rates of the roots, stems, leaves, and styles (silks) of maize (Zea mays L.) as soil water was depleted. The ?w was measured in the region of cell expansion

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

1985-01-01

82

STORM: A General Model to Determine the Number and Adaptive Changes of Epithelial Stem Cells in Teleost, Murine and Human Intestinal Tracts  

PubMed Central

Intestinal stem cells play a pivotal role in the epithelial tissue renewal, homeostasis and cancer development. The lack of a general marker for intestinal stem cells across species has hampered analysis of stem cell number in different species and their adaptive changes upon intestinal lesions or during development of cancer. Here a two-dimensional model, named STORM, has been developed to address this issue. By optimizing epithelium renewal dynamics, the model examines the epithelial stem cell number by taking experimental input information regarding epithelium proliferation and differentiation. As the results suggest, there are 2.0–4.1 epithelial stem cells on each pocket section of zebrafish intestine, 2.0–4.1 stem cells on each crypt section of murine small intestine and 1.8–3.5 stem cells on each crypt section of human duodenum. The model is able to provide quick results for stem cell number and its adaptive changes, which is not easy to measure through experiments. Its general applicability to different species makes it a valuable tool for analysis of intestinal stem cells under various pathological conditions.

Wang, Zhengyuan; Matsudaira, Paul; Gong, Zhiyuan

2010-01-01

83

STORM: a general model to determine the number and adaptive changes of epithelial stem cells in teleost, murine and human intestinal tracts.  

PubMed

Intestinal stem cells play a pivotal role in the epithelial tissue renewal, homeostasis and cancer development. The lack of a general marker for intestinal stem cells across species has hampered analysis of stem cell number in different species and their adaptive changes upon intestinal lesions or during development of cancer. Here a two-dimensional model, named STORM, has been developed to address this issue. By optimizing epithelium renewal dynamics, the model examines the epithelial stem cell number by taking experimental input information regarding epithelium proliferation and differentiation. As the results suggest, there are 2.0-4.1 epithelial stem cells on each pocket section of zebrafish intestine, 2.0-4.1 stem cells on each crypt section of murine small intestine and 1.8-3.5 stem cells on each crypt section of human duodenum. The model is able to provide quick results for stem cell number and its adaptive changes, which is not easy to measure through experiments. Its general applicability to different species makes it a valuable tool for analysis of intestinal stem cells under various pathological conditions. PMID:21124758

Wang, Zhengyuan; Matsudaira, Paul; Gong, Zhiyuan

2010-11-19

84

Hematopoietic Stem-Cell Transplantation in the Pediatric Population. Executive Summary. Effective Health Care Program. Comparative Effectiveness Review Number 48.  

National Technical Information Service (NTIS)

Hematopoietic stem-cell transplantation (HSCT) refers to a procedure in which hematopoietic progenitor cells, including repopulating stem cells, are infused to restore bone marrow function in patients. HSCT is categorized by the source of the stem cells, ...

2012-01-01

85

The Endophytic Mycoflora of Bark, Leaf, and Stem Tissues of Azadirachta indica A. Juss (Neem) from Varanasi (India)  

Microsoft Academic Search

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\\u000a representing 18 fungal taxa were obtained from segments of bark, stem, and leaves of this tree. Hyphomycetes (62.2%) were\\u000a the most prevalent followed by the Coelomycetes (27.4%)

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

2007-01-01

86

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

87

The Number of Stem Cells in the Subependymal Zone of the Adult Rodent Brain is Correlated with the Number of Ependymal Cells and Not with the Volume of the Niche  

PubMed Central

The mammalian subependymal zone (SEZ; often called subventricular) situated at the lateral walls of the lateral ventricles of the brain contains a pool of relatively quiescent adult neural stem cells whose neurogenic activity persists throughout life. These stem cells are positioned in close proximity both to the ependymal cells that provide the cerebrospinal fluid interface and to the blood vessel endothelial cells, but the relative contribution of these 2 cell types to stem cell regulation remains undetermined. Here, we address this question by analyzing a naturally occurring example of volumetric scaling of the SEZ in a comparison of the mouse SEZ with the larger rat SEZ. Our analysis reveals that the number of stem cells in the SEZ niche is correlated with the number of ependymal cells rather than with the volume, thereby indicating the importance of ependymal-derived factors in the formation and function of the SEZ. The elucidation of the factors generated by ependymal cells that regulate stem cell numbers within the SEZ is, therefore, of importance for stem cell biology and regenerative neuroscience.

ffrench-Constant, Charles

2012-01-01

88

Remodeling of the postnatal mouse testis is accompanied by dramatic changes in stem cell number and niche accessibility.  

PubMed

Little is known about stem cell biology or the specialized environments or niches believed to control stem cell renewal and differentiation in self-renewing tissues of the body. Functional assays for stem cells are available only for hematopoiesis and spermatogenesis, and the microenvironment, or niche, for hematopoiesis is relatively inaccessible, making it difficult to analyze donor stem cell colonization events in recipients. In contrast, the recently developed spermatogonial stem cell assay system allows quantitation of individual colonization events, facilitating studies of stem cells and their associated microenvironment. By using this assay system, we found a 39-fold increase in male germ-line stem cells during development from birth to adult in the mouse. However, colony size or area of spermatogenesis generated by neonate and adult stem cells, 2-3 months after transplantation into adult tubules, was similar ( approximately 0.5 mm(2)). In contrast, the microenvironment in the immature pup testis was 9.4 times better than adult testis in allowing colonization events, and the area colonized per donor stem cell, whether from adult or pup, was about 4.0 times larger in recipient pups than adults. These factors facilitated the restoration of fertility by donor stem cells transplanted to infertile pups. Thus, our results demonstrate that stem cells and their niches undergo dramatic changes in the postnatal testis, and the microenvironment of the pup testis provides a more hospitable environment for transplantation of male germ-line stem cells. PMID:11371640

Shinohara, T; Orwig, K E; Avarbock, M R; Brinster, R L

2001-05-22

89

Remodeling of the postnatal mouse testis is accompanied by dramatic changes in stem cell number and niche accessibility  

PubMed Central

Little is known about stem cell biology or the specialized environments or niches believed to control stem cell renewal and differentiation in self-renewing tissues of the body. Functional assays for stem cells are available only for hematopoiesis and spermatogenesis, and the microenvironment, or niche, for hematopoiesis is relatively inaccessible, making it difficult to analyze donor stem cell colonization events in recipients. In contrast, the recently developed spermatogonial stem cell assay system allows quantitation of individual colonization events, facilitating studies of stem cells and their associated microenvironment. By using this assay system, we found a 39-fold increase in male germ-line stem cells during development from birth to adult in the mouse. However, colony size or area of spermatogenesis generated by neonate and adult stem cells, 2–3 months after transplantation into adult tubules, was similar (?0.5 mm2). In contrast, the microenvironment in the immature pup testis was 9.4 times better than adult testis in allowing colonization events, and the area colonized per donor stem cell, whether from adult or pup, was about 4.0 times larger in recipient pups than adults. These factors facilitated the restoration of fertility by donor stem cells transplanted to infertile pups. Thus, our results demonstrate that stem cells and their niches undergo dramatic changes in the postnatal testis, and the microenvironment of the pup testis provides a more hospitable environment for transplantation of male germ-line stem cells.

Shinohara, Takashi; Orwig, Kyle E.; Avarbock, Mary R.; Brinster, Ralph L.

2001-01-01

90

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

91

Loss of stem cell repopulating ability upon transplantation. Effects of donor age, cell number, and transplantation procedure  

SciTech Connect

Long-term functional capacities of marrow cell lines were defined by competitive repopulation, a technique capable of detecting a small decline in repopulating abilities. There was little or no difference between cells from old and young donors, but a single serial transplantation caused a large decline in repopulating ability. Varying the numbers of marrow cells transplanted into the initial carrier from 10(5) to 10(7) did not alter the ability of the carrier's marrow cells to repopulate in competition with previously untransplanted cells. This ability was improved only in carriers that had received 10(8) marrow cells, although deleterious effects of transplantation were still present. These effects were not solely caused by cell damage from the transplantation procedure, because transplantation by parabiosis, or recovery from sublethal irradiation without transplantation, reduced repopulating abilities as much as transplanting 10(5) to 10(7) marrow cells. The transplantation effect also was not caused solely by irradiation, because the same effect appeared in unirradiated W/Wv carriers. The transplantation effect was more pronounced when donors were identified by hemoglobin type than by chromosome markers, implying that nonerythroid cell lines may be less affected by transplantation than erythroid precursor cells. When the effects of a lifetime of normal function and a single transplantation were compared, the latter caused 3-7 times more decline in repopulating abilities of phytohemagglutinin-responsive cell precursors, and at least 10-20 times more decline in erythroid cell precursors. Stem cell lines can be serially transplanted at least five times before losing their ability to repopulate and save lethally irradiated recipients or to cure genetically anemic mice. Therefore, if transplantation causes an acceleration of the normal aging process, these figures suggest that stem cells should be able to function normally through at least 15-50 life spans.

Harrison, D.E.; Astle, C.M.

1982-12-01

92

A number of bone marrow mesenchymal stem cells but neither phenotype nor differentiation capacities changes with age of rats.  

PubMed

Bone marrow (BM) derived mesenchymal stem cells (MSC) are pluripotent cells which can differentiate into osteogenic, adipogenic and other lineages. In spite of the broad interest, the information about the changes in BM cell composition, in particularly about the variation of MSC number and their properties in relation to the age of the donor is still controversial. The aim of this study was to investigate the age associated changes in variations of BM cell composition, phenotype and differentiation capacities of MSC using a rat model. Cell populations were characterized by flow cytometry using light scattering parameters, DNA content and a set of monoclonal antibodies. Single cell analysis was performed by conventional fluorescent microscopy. In vitro culture of MSC was established and their phenotype and capability for in vitro differentiation into osteogenic and adipogenic cells was shown. Age related changes in tibiae and femurs, amount of BM tissue, BM cell composition, proportions of separated MSC and yield of MSC in 2 weeks of in vitro culture were found. At the same time, neither change in phenotype no in differentiation capacities of MSC was registered. Age-related changes of the number of MSC should be taken into account whenever MSC are intended to be used for investigations. PMID:17978579

Tokalov, Sergey V; Gruener, Susanne; Schindler, Sebastian; Iagunov, Alexey S; Baumann, Michael; Abolmaali, Nasreddin D

2007-10-31

93

The effects of vibration loading on adipose stem cell number, viability and differentiation towards bone-forming cells  

PubMed Central

Mechanical stimulation is an essential factor affecting the metabolism of bone cells and their precursors. We hypothesized that vibration loading would stimulate differentiation of human adipose stem cells (hASCs) towards bone-forming cells and simultaneously inhibit differentiation towards fat tissue. We developed a vibration-loading device that produces 3g peak acceleration at frequencies of 50 and 100 Hz to cells cultured on well plates. hASCs were cultured using either basal medium (BM), osteogenic medium (OM) or adipogenic medium (AM), and subjected to vibration loading for 3 h d–1 for 1, 7 and 14 day. Osteogenesis, i.e. differentiation of hASCs towards bone-forming cells, was analysed using markers such as alkaline phosphatase (ALP) activity, collagen production and mineralization. Both 50 and 100 Hz vibration frequencies induced significantly increased ALP activity and collagen production of hASCs compared with the static control at 14 day in OM. A similar trend was detected for mineralization, but the increase was not statistically significant. Furthermore, vibration loading inhibited adipocyte differentiation of hASCs. Vibration did not affect cell number or viability. These findings suggest that osteogenic culture conditions amplify the stimulatory effect of vibration loading on differentiation of hASCs towards bone-forming cells.

Tirkkonen, Laura; Halonen, Heidi; Hyttinen, Jari; Kuokkanen, Hannu; Sievanen, Harri; Koivisto, Anna-Maija; Mannerstrom, Bettina; Sandor, George K. B.; Suuronen, Riitta; Miettinen, Susanna; Haimi, Suvi

2011-01-01

94

The effects of vibration loading on adipose stem cell number, viability and differentiation towards bone-forming cells.  

PubMed

Mechanical stimulation is an essential factor affecting the metabolism of bone cells and their precursors. We hypothesized that vibration loading would stimulate differentiation of human adipose stem cells (hASCs) towards bone-forming cells and simultaneously inhibit differentiation towards fat tissue. We developed a vibration-loading device that produces 3g peak acceleration at frequencies of 50 and 100 Hz to cells cultured on well plates. hASCs were cultured using either basal medium (BM), osteogenic medium (OM) or adipogenic medium (AM), and subjected to vibration loading for 3 h d(-1) for 1, 7 and 14 day. Osteogenesis, i.e. differentiation of hASCs towards bone-forming cells, was analysed using markers such as alkaline phosphatase (ALP) activity, collagen production and mineralization. Both 50 and 100 Hz vibration frequencies induced significantly increased ALP activity and collagen production of hASCs compared with the static control at 14 day in OM. A similar trend was detected for mineralization, but the increase was not statistically significant. Furthermore, vibration loading inhibited adipocyte differentiation of hASCs. Vibration did not affect cell number or viability. These findings suggest that osteogenic culture conditions amplify the stimulatory effect of vibration loading on differentiation of hASCs towards bone-forming cells. PMID:21613288

Tirkkonen, Laura; Halonen, Heidi; Hyttinen, Jari; Kuokkanen, Hannu; Sievänen, Harri; Koivisto, Anna-Maija; Mannerström, Bettina; Sándor, George K B; Suuronen, Riitta; Miettinen, Susanna; Haimi, Suvi

2011-05-25

95

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.

96

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

PubMed Central

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. 

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

2012-01-01

97

Leaf death and decomposition during pasture regrowth  

Microsoft Academic Search

Data are presented that describe the pattern of leaf death per ramet and per unit area. Leaf death per ramet was influenced by the number of leaves that died and the weight of the dead leaves. Leaf weight was important in determining differences in seasonal and species death rate per ramet.Leaf death rates reached a maximum of 56 lb D.M.

W. F. Hunt

1971-01-01

98

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

2013-04-10

99

Stem Water Potential is a Sensitive Indicator of Grapevine Water Status  

Microsoft Academic Search

Dawn leaf water potential (dawnC), leaf water potential (leafC) and stem water potential (stemC) were measured on mature leaves to determine non-irrigated vine water status in vineyards during the growing season. StemC was the most discriminating indicator for both moderate and severe water deficits. The diÄerence between stemC and leafC (DC) provided an indirect measurement of mean leaf transpiration which

XAVIER CHONE; CORNELIS VAN LEEUWEN; DENIS DUBOURDIEU

2001-01-01

100

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

101

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

PubMed

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. PMID:21841904

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

2009-01-01

102

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

103

Human blood and marrow side population stem cell and Stro-1 positive bone marrow stromal cell numbers decline with age, with an increase in quality of surviving stem cells: correlation with cytokines.  

PubMed

Hematological deficiencies increase with aging leading to anemias, reduced hematopoietic stress responses and myelodysplasias. This study tested the hypothesis that side population hematopoietic stem cells (SP-HSC) would decrease with aging, correlating with IGF-1 and IL-6 levels and increases in bone marrow fat. Marrow was obtained from the femoral head and trochanteric region of the femur at surgery for total hip replacement (N=100). Whole trabecular marrow samples were ground in a sterile mortar and pestle and cellularity and fat content determined. Marrow and blood mononuclear cells were stained with Hoechst dye and the SP-HSC profiles acquired. Marrow stromal cells (MSC) were enumerated flow cytometrically employing the Stro-1 antibody, and clonally in the colony forming unit fibroblast (CFU-F) assay. Plasma levels of IGF-1 (ng/ml) and IL-6 (pg/ml) were measured by ELISA. SP-HSC in blood and bone marrow decreased with age but the quality of the surviving stem cells increased. MSC decreased non-significantly. IGF-1 levels (mean=30.7, SEM=2) decreased and IL-6 levels (mean=4.4, SEM=1) increased with age as did marrow fat (mean=1.2mmfat/g, SEM=0.04). There were no significant correlations between cytokine levels or fat and SP-HSC numbers. Stem cells appear to be progressively lost with aging and only the highest quality stem cells survive. PMID:21035480

Brusnahan, S K; McGuire, T R; Jackson, J D; Lane, J T; Garvin, K L; O'Kane, B J; Berger, A M; Tuljapurkar, S R; Kessinger, M A; Sharp, J G

2010-10-28

104

A highly sensitive and accurate method to quantify absolute numbers of c-kit+ cardiac stem cells following transplantation in mice.  

PubMed

Although transplantation of c-kit+ cardiac stem cells (CSCs) alleviates post-myocardial infarction left ventricular dysfunction, there are no reliable methods that enable measurement of the absolute number of CSCs that persist in the recipient heart. To overcome this limitation, we developed a highly sensitive and accurate method to quantify the absolute number of murine CSCs after transplantation. This method has two unique features: (1) real-time PCR-based detection of a novel male-specific, multiple-copy gene, Rbmy, which significantly increases the sensitivity of detection of male donor cells in a female recipient, and (2) an internal standard, which permits quantification of the absolute number of CSCs as well as the total number of cells in the recipient organ. Female C57BL/6 mice underwent coronary occlusion and reperfusion; 2 days later, 10(5) male mouse CSCs were injected intramyocardially. Tissues were analyzed by real-time PCR at serial time points. In the risk region, >75 % of CSCs present at 5 min were lost in the ensuing 24 h; only 7.6 ± 2.1 % of the CSCs present at 5 min could still be found at 7 days after transplantation and only 2.8 ± 0.5 % (i.e., 1,224 ± 230 cells/heart) at 35 days. Thus, even after direct intramyocardial injection, the total number of CSCs that remain in the murine heart is minimal (at 24 h, ~10 % of the cells injected; at 35 days, ~1 %). This new quantitative method of stem cell detection, which enables measurement of absolute cell number, should be useful to optimize cell-based therapies, not only for CSCs but also for other stem cells and other organs. PMID:23549981

Hong, Kyung U; Li, Qian-Hong; Guo, Yiru; Patton, Nikita S; Moktar, Afsoon; Bhatnagar, Aruni; Bolli, Roberto

2013-04-03

105

An external heat pulse method for measurement of sap flow through fruit pedicels, leaf petioles and other small-diameter stems.  

PubMed

The external heat ratio method is described for measurement of low rates of sap flow in both directions through stems and other plant organs, including fruit pedicels, with diameters up to 5 mm and flows less than 2 g h(-1). Calibration was empirical, with heat pulse velocity (v(h)) compared to gravimetric measurements of sap flow. In the four stem types tested (Actinidia sp. fruit pedicels, Schefflera arboricola petioles, Pittosporum crassifolium stems and Fagus sylvatica stems), v(h) was linearly correlated with sap velocity (v(s)) up to a v(s) of approximately 0.007 cm s(-1), equivalent to a flow of 1.8 g h(-1) through a 3-mm-diameter stem. Minimum detectable v(s) was approximately 0.0001 cm s(-1), equivalent to 0.025 g h(-1) through a 3-mm-diameter stem. Sensitivity increased with bark removal. Girdling had no effect on short-term measurements of in vivo sap flow, suggesting that phloem flows were too low to be separated from xylem flows. Fluctuating ambient temperatures increased variability in outdoor sap flow measurements. However, a consistent diurnal time-course of fruit pedicel sap flow was obtained, with flows towards 75-day-old kiwifruit lagging behind evaporative demand and peaking at 0.3 g h(-1) in the late afternoon. PMID:19671100

Clearwater, Michael J; Luo, Zhiwei; Mazzeo, Mariarosaria; Dichio, Bartolomeo

2009-08-07

106

IGF-1/IGFBP-1 increases blastocyst formation and total blastocyst cell number in mouse embryo culture and facilitates the establishment of a stem-cell line  

PubMed Central

Background Apoptosis occurs frequently for blastocysts cultured in vitro, where conditions are suboptimal to those found in the natural environment. Insulin-like growth factor-1 (IGF-1) plays an important role in preventing apoptosis in the early development of the embryo, as well as in the progressive regulation of organ development. We hypothesize that IGF-1 and its dephosphorylated binding protein (IGFBP-1) may be able to improve embryo culture with an associated reduced cell death, and that the resultant increase in the total cell number of the embryo could increase the chances of establishing an embryonic stem-cell line. Results In vivo fertilized zygotes were cultured in medium containing supplementary IGF-1, or IGFBP-1/IGF-1. The stages of the resultant embryos were evaluated at noon on day five post-hCG injection. The extent of apoptosis and necrosis was evaluated using Annexin V and propidium iodine staining under fluorescent microscopy. The establishment of embryonic stem-cell lines was performed using the hatching blastocysts that were cultured in the presence of IGF-1 or IGFBP-1/IGF-1. The results show that the rate of blastocyst formation in a tissue-culture system in the presence of IGF-1 was 88.7% and IGFBP-1/IGF-1 it was 94.6%, respectively, and that it was significantly greater than the figure for the control group (81.9%). IGFBP-1/IGF-1 also resulted in a higher hatching rate than was the case for the control group (68.8% vs. 48.6% respectively). IGF-1 also increased the number of Annexin V-free and propidium iodine-free blastocysts in culture (86.8% vs. 75.9% respectively). Total cell number of blastocyst in culture was increased by 18.9% for those examples cultured with dephosphorylated IGFBP-1/IGF-1. For subsequent stem-cell culture, the chances of the successful establishment of a stem-cell line was increased for the IGF-1 and IGFBP-1/IGF-1 groups (IGF-1 vs. IGFBP-1/IGF-1 vs. control: 45.8% vs. 59.6% vs. 27.3% respectively). Conclusion IGF-1 or dephosphorylated IGFBP-1/IGF-1 supplement does result in an anti-apoptotic effect for early embryo development in culture, with a subsequent increased total cell number resulting from cell culture. The effect is beneficial for the later establishment of a stem-cell line.

Lin, Ta-Chin; Yen, Jui-Mei; Gong, Kun-Bing; Hsu, Teng-Tsao; Chen, Lih-Ren

2003-01-01

107

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

108

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.

109

Plant Structure--Leaves, Stems, and Roots  

NSDL National Science Digital Library

Page one consists of a full color illustration of an idealized plant, showing various leaf, stem and root features. Page two illustrates various adaptations of plant flowers, leaves and stems. All illustrations are accompanied by explanations of the structures' functions.

2000-01-01

110

Does leaf manipulation affect leaf appearance in italian ryegrass (Lolium multiflorum Lam.)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mechanical stimuli such as rubbing, shaking, or flexing plants can alter their growth rates and morphologies. Plant response to mechanical stress can result in delayed plant growth, reduced leaf size, shorten and thicken stems, and reduced yields. Repeated measurements, such as leaf counting or me...

111

Mechanisms of Ion Uptake by Leaves with Special Reference to Isolated Leaf Cells and Their Components.  

National Technical Information Service (NTIS)

The micro-nutrient zinc and possibly all other micronutrients are absorbed by plant tissues (intact roots, isolated leaf cells, leaf disks, excised roots, stem callus tissue) primarily by a passive process. Absorption as compared with phosphate uptake, is...

1970-01-01

112

From the Cover: Remodeling of the postnatal mouse testis is accompanied by dramatic changes in stem cell number and niche accessibility  

Microsoft Academic Search

Little is known about stem cell biology or the specialized environments or niches believed to control stem cell renewal and differentiation in self-renewing tissues of the body. Functional assays for stem cells are available only for hematopoiesis and spermatogenesis, and the microenvironment, or niche, for hematopoiesis is relatively inaccessible, making it difficult to analyze donor stem cell colonization events in

Takashi Shinohara; Kyle E. Orwig; Mary R. Avarbock; Ralph L. Brinster

2001-01-01

113

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

2013-06-07

114

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

Microsoft Academic Search

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

Hans Gehrig; Karin Faist; Manfred Kluge

1998-01-01

115

Habitat Complexity of Stream Leaf Packs: Effects on Benthic Macroinvertebrates and Leaf Litter Breakdown  

NASA Astrophysics Data System (ADS)

We investigated two attributes of leaf-pack complexity (i.e., leaf-pack mass and leaf surface area) on fish predation, colonization of benthic macroinvertebrates, and leaf breakdown rates in a coldwater Michigan stream. We manipulated three factors using a factorial design: fish (exclusion or control cage), leaf-pack mass (1, 3, or 5 g dry mass), and leaf surface area (<7, 7-10, or >10 cm leaf width). Acer leaves were fastened into leaf packs. Exclusion cages had mesh on all sides; control cages lacked mesh on two sides to provide access to fishes. Two replicate leaf packs were randomly collected after 25-31 d from two sections of the stream (n = 4). Common shredders were Gammarus, Pycnopsyche, and Lepidostoma. We did not detect a significant effect of fish predation on benthic macroinvertebrates or leaf breakdown (i.e., mass loss). Colonization of benthic macroinvertebrates appeared proportional to leaf-pack mass but was unaffected by the surface area of leaves. Leaf breakdown was more rapid among leaf packs with fewer leaves (i.e., leaves with large surface area and leaf packs with low mass) and greater numbers of shredders. We suspect that physical fragmentation is the primary mechanism for higher breakdown rates among leaf packs with fewer leaves.

Ruetz, C. R.; Vanhaitsma, D. L.; Breen, M. J.

2005-05-01

116

[Photoprotective mechanisms of leaf anthocyanins: research progress].  

PubMed

Anthocyanin is widely distributed in plant organs such as root, stem, leaf, flower and fruit, being a kind of secondary metabolites generated in plant morphogenesis or for stress response. Leaf anthocyanin has special chemical structure and spectral properties, playing important roles in plant photoprotection, and becomes a hotspot in plant photosynthetic physiological ecology. This paper summarized the recent research progress in the effects of leaf anthocyanin on plant photosynthesis, including the distribution of leaf anthocyanin, its spectral properties, and its relationships with photosynthetic pigments, with the focus on the potential mechanisms of anthocyanins photoprotection, including light absorption, antioxidation, and osmotic regulation. The further research directions on the effects of leaf anthocyanin on photoprotection were proposed. PMID:22720633

Wang, Liang-Zai; Hu, Yan-Bo; Zhang, Hui-Hui; Xu, Nan; Zhang, Xiu-Li; Sun, Guang-Yu

2012-03-01

117

Test plan for composting studies involving weight and volume reduction of leaf and stalk biomass: DOE/OTD TTP(number sign) SR17SS53 (ampersand) TTP(number sign) SR18SS41.  

National Technical Information Service (NTIS)

SRTC and a panel of experts from off-site previously determined that composting was the most attractive alternative for reducing the volume and weight of biomass that was slightly radioactive. The SRTC proposed scope of work for Subtask 2 of TTP(number si...

E. W. Wilde J. Kastner C. Murphy J. Santo Domingo

1997-01-01

118

Aging does not alter the number or phenotype of putative stem/progenitor cells in the neurogenic region of the hippocampus.  

PubMed

To investigate whether dramatically waned dentate neurogenesis during aging is linked to diminution in neural stem/progenitor cell (NSC) number, we counted cells immunopositive for Sox-2 (a putative marker of NSCs) in the subgranular zone (SGZ) of young, middle-aged and aged F344 rats. The young SGZ comprised approximately 50,000 Sox-2+ cells and this amount did not diminish with aging. Quantity of GFAP+ cells and vimentin+ radial glia also remained stable during aging in this region. Besides, in all age groups, analogous fractions of Sox-2+ cells expressed GFAP (astrocytes/NSCs), NG-2 (oligodendrocyte-progenitors/NSCs), vimentin (radial glia), S-100beta (astrocytes) and doublecortin (new neurons). Nevertheless, analyses of Sox-2+ cells with proliferative markers insinuated an increased quiescence of NSCs with aging. Moreover, the volume of rat-endothelial-cell-antigen-1+ capillaries (vascular-niches) within the SGZ exhibited an age-related decline, resulting in an increased expanse between NSCs and capillaries. Thus, decreased dentate neurogenesis during aging is not attributable to altered number or phenotype of NSCs. Instead, it appears to be an outcome of increased quiescence of NSCs due to changes in NSC milieu. PMID:17092610

Hattiangady, Bharathi; Shetty, Ashok K

2006-11-07

119

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

120

STEM, STEM Education, STEMmania  

ERIC Educational Resources Information Center

|In this article, the author introduces integrative STEM (science, technology, engineering, and/or mathematics) education and discusses the importance of the program. The notion of integrative STEM education includes approaches that explore teaching and learning between/among any two or more of the STEM subject areas, and/or between a STEM subject…

Sanders, Mark

2009-01-01

121

Understanding STEM: Current Perceptions  

ERIC Educational Resources Information Center

|In many ways, the push for STEM (science, technology, engineering, and mathematics) education appears to have grown from a concern for the low number of future professionals to fill STEM jobs and careers and economic and educational competitiveness. The proponents of STEM education believe that by increasing math and science requirements in…

Brown, Ryan; Brown, Joshua; Reardon, Kristin; Merrill, Chris

2011-01-01

122

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

2012-08-06

123

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

124

Towards an integrated model for breast cancer etiology: The crucial role of the number of mammary tissue-specific stem cells  

Microsoft Academic Search

Perinatal events and conditions, notably birth weight, are associated with breast cancer risk in offspring, and correlates of mammary gland mass are predictors of breast cancer risk. These findings may be interpreted as indicating that high levels of estrogens and components of the insulin-like growth factor system during pregnancy favour the generation of mammary tissue-specific stem cells, and that the

Dimitrios Trichopoulos; Pagona Lagiou; Hans-Olov Adami

2005-01-01

125

Stem Cell Factor Increases Colony-Forming Unit-Spleen Number In Vitro in Synergy With Interleukin6, and In Vivo in SIISZd Mice as a Single Factor  

Microsoft Academic Search

ICE BEARING two mutant alleles at either the M Dominant White Spotting (W) or Steel (SI) loci have identical phenotypes of hypopigmentation, sterility, and a severe macrocytic anemia.' Bone marrow (BM) transplantation studies have shown that the defect in W mice is intrinsic to primitive hematopoietic stem cells, while the defect in SI mice is intrinsic to the hematopoietic microenvironment.'\\

David M. Bodine; Donald Orlic; Neal C. Birkett; Nancy E. Seidel; Krisztina M. Zsebo

1992-01-01

126

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

127

7 CFR 29.2301 - Stem.  

Code of Federal Regulations, 2013 CFR

... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.2301 Section 29.2301 Agriculture Regulations...Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2301 Stem. The midrib or large central vein of a tobacco leaf....

2013-01-01

128

7 CFR 29.3059 - Stem.  

Code of Federal Regulations, 2013 CFR

... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.3059 Section 29.3059 Agriculture Regulations...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf....

2013-01-01

129

7 CFR 29.1061 - Stem.  

Code of Federal Regulations, 2013 CFR

... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.1061 Section 29.1061 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf....

2013-01-01

130

7 CFR 29.3549 - Stem.  

Code of Federal Regulations, 2013 CFR

... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.3549 Section 29.3549 Agriculture Regulations...s. Types 35, 36, 37 and Foreign Type 95) § 29.3549 Stem. The midrib or large central vein of a tobacco leaf....

2013-01-01

131

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

132

Mapping leaf surface landscapes.  

PubMed Central

Leaf surfaces provide the ecologically relevant landscapes to those organisms that encounter or colonize the leaf surface. Leaf surface topography directly affects microhabitat availability for colonizing microbes, microhabitat quality and acceptability for insects, and the efficacy of agricultural spray applications. Prior detailed mechanistic studies that examined particular fungi-plant and pollinator-plant interactions have demonstrated the importance of plant surface topography or roughness in determining the outcome of the interactions. Until now, however, it has not been possible to measure accurately the topography--i.e., the three-dimensional structure--of such leaf surfaces or to record precise changes in patterns of leaf surface elevation over time. Using contact mode atomic force microscopy, we measured three-dimensional coordinates of upper leaf surfaces of Vaccinium macrocarpon (cranberry), a perennial plant, on leaves of two age classes. We then produced topographic maps of these leaf surfaces, which revealed striking differences between age classes of leaves: old leaves have much rougher surfaces than those of young leaves. Atomic force microscope measurements were analyzed by lag (1) autocorrelation estimates of leaf surfaces by age class. We suggest that the changes in topography result from removal of epicuticular lipids and that the changes in leaf surface topography influence phylloplane ecology. Visualizing and mapping leaf surfaces permit detailed investigations into leaf surface-mediated phenomena, improving our understanding of phylloplane interactions. Images Fig. 1

Mechaber, W L; Marshall, D B; Mechaber, R A; Jobe, R T; Chew, F S

1996-01-01

133

BD™ Stem Cell Enumeration Kit  

Center for Biologics Evaluation and Research (CBER)

... BD™ Stem Cell Enumeration Kit. Applicant: BD Biosciences. 510(k) number: BK110037. Product: BD™ Stem Cell Enumeration Kit. ... More results from www.fda.gov/biologicsbloodvaccines/bloodbloodproducts/approvedproducts

134

Artificial Stem Cell Niches  

PubMed Central

Stem cells are characterized by their dual ability to reproduce themselves (self-renew) and specialize (differentiate), yielding a plethora of daughter cells that maintain and regenerate tissues. In contrast to their embryonic counterparts, adult stem cells retain their unique functions only if they are in intimate contact with an instructive microenvironment, termed stem cell niche. In these niches, stem cells integrate a complex array of molecular signals that, in concert with induced cell-intrinsic regulatory networks, control their function and balance their numbers in response to physiologic demands. This progress report provides a perspective on how advanced materials technologies could be used (i) to engineer and systematically analyze specific aspects of functional stem cells niches in a controlled fashion in vitro and (ii) to target stem cell niches in vivo. Such “artificial niches” constitute potent tools for elucidating stem cell regulatory mechanisms with the capacity to directly impact the development of novel therapeutic strategies for tissue regeneration.

Lutolf, Matthias P.; Blau, Helen M.

2011-01-01

135

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.

136

Effects of leaf blade narrowness and petiole length on the light capture efficiency of a shoot  

Microsoft Academic Search

Effects of the length: width ratio of a leaf blade and petiole length on shoot light capture were studied with computer simulation.\\u000a Both a larger length: width ratio and longer petiole contributed to larger light capture per unit leaf area due to a reduced\\u000a aggregation of leaf area around the stem. Other conditions being equal, shoots with narrow leaves and

Akio Takenaka

1994-01-01

137

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

138

Response of Arundo Donax L. (Giant Reed) To Leaf Damage and Partial Defoliation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Arundo donax (giant reed) is a tall clonal invasive grass which has impacted many riparian ecosystems in the U.S. Experiments tested the hypotheses 1) that defoliation would affect A. donax stem growth and leaf production and 2) that leaf damage or removal would influence A. donax photosynthetic ra...

139

Organ shape and size: a lesson from studies of leaf morphogenesis  

Microsoft Academic Search

Control of the shape and size of indeterminate organs, such as roots and stems, is directly related to the control of the shape and size of the cells in these organs, as predicted by orthodox cell theory. For example, the polarity-dependent growth of leaf cells directly affects the polar expansion of leaves. Thus, the control of leaf shape is related

Hirokazu Tsukaya

2003-01-01

140

Leaf cutter ants  

NSDL National Science Digital Library

There is much diversity between ants. Leaf cutter ants use their mandibles to cut leaf fragments and take them back to their home. They don't eat the leaves, but instead use them to grow fungus on. They then eat the fungus.

N/A N/A (None;)

2007-12-15

141

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

142

Woody stem galls interact with foliage to affect community associations.  

PubMed

Gall wasps (Hymenoptera: Cynipidae) hijack the physiology of their host plant to produce galls that house wasps throughout their immature stages. The gall-maker-host plant interaction is highly evolved, and galls represent an extended phenotype of the gall wasp. We evaluated two-way interactions between stem galls produced by Dryocosmus kuriphilus Yasumatsu on Castanea spp. (Fagales: Fagaceae) and foliage directly attached to galls (gall leaves) using gall leaf excision experiments and herbivore bioassays. Early season gall leaf excision decreased the dry weight per chamber (nutritive index) and thickness of the protective schlerenchyma layer and increased the number of empty chambers and the occurrence and size of exterior fungal lesions. Leaf excision also caused a modestly significant (alpha = 0.1) increase in the incidence of feeding chamber fungi and herbivory by Curculio sayi Gyllenhal (Coleoptera: Curculionidae), and a modest decrease in parasitoids. This study shows that gall leaves are important for stem gall development, quality, and defenses, adding support for the nutrient and enemy hypotheses. We also evaluated the effects of stem galls on the suitability of gall leaves to Lymantria dispar L. (Lepidoptera: Lymantriidae) herbivory to assess the extent of gall defenses in important source leaves. Relative growth rate of L. dispar larvae was greater on gall leaves compared with normal leaves, indicating that, despite their importance, gall leaves may be more suitable to generalist insect herbivores, suggesting limitations to the extended phenotype of the gall wasp. Our results improve our knowledge of host-cynipid interactions, gall source-sink relations, and D. kuriphilus community interactions. PMID:19389291

Cooper, W R; Rieske, L K

2009-04-01

143

Independent recruitment of a conserved developmental mechanism during leaf evolution  

Microsoft Academic Search

Vascular plants evolved in the Middle to Late Silurian period, about 420 million years ago. The fossil record indicates that these primitive plants had branched stems with sporangia but no leaves. Leaf-like lateral outgrowths subsequently evolved on at least two independent occasions. In extant plants, these events are represented by microphyllous leaves in lycophytes (clubmosses, spikemosses and quillworts) and megaphyllous

C. Jill Harrison; Susie B. Corley; Elizabeth C. Moylan; Debbie L. Alexander; Robert W. Scotland; Jane A. Langdale

2005-01-01

144

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

145

Estimating Near-Infrared Leaf Reflectance from Leaf Structural Characteristics  

Microsoft Academic Search

The relationship between near-infrared reflectance at 800 nm (NIRR) from leaves and characteristics of leaf structure known to affect photosynthesis was investigated in 48 species of alpine angiosperms. This wavelength was selected to discriminate the effects of leaf structure vs. chemical or water content on leaf reflectance. A quantitative model was first constructed correlating NIRR with leaf structural characteristics for

Michele R. Slaton; E. Raymond Hunt; William K. Smith

2001-01-01

146

Autologous Stem Cell Transplantation Following High-Dose Whole-Body Irradiation of Dogs - Influence of Cell Number and Fractionation Regimes.  

National Technical Information Service (NTIS)

The acute radiation syndrome after a single dose of 1600 R (approx. 12-14 Gy in body midline) and after fractionated irradiation with 2400 R (approx. 18-20 Gy) was studied with regard to fractionation time and to the number of bone marrow cells infused. T...

U. Bodenberger

1981-01-01

147

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

148

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

149

Leaf movement of bush bean: a biometeorological perspective  

NASA Astrophysics Data System (ADS)

Leaf movements of bush bean plants were studied at the relatively low photon flux density of 0.2 mmol/m2 per s, and air temperatures of 25° and 35° C in a growth chamber. A beta-ray gauge system was used to monitor continuously pulvinus water status and bending. Leaf angles were below the horizontal and were linearly related to the soil water content (R>=-0.91 at 25° C and R>=-0.93 at 35° C). The beta-ray transmission maxima coincided with the stem temperature minima in darkness and vice versa when brightness prevailed as the growth chamber temperature varied with the photoperiod. Leaf angle increased linearly with increased beta-ray transmission. The Q10 temperature coefficient, a measure of the metabolic energy requirement for leaf movement between 25° and 35° C was estimated at 1.8, and the corresponding mean Arrhenius constant at 423 kJ/mol for bush bean.

Raeini-Sarjaz, M.; Barthakur, N. N.; Arnold, N. P.

150

Do Leaf Breakdown Rates Actually Measure Leaf Disappearance from Streams?  

Microsoft Academic Search

Abstract Wemeasured leaf input, leaf breakdown, and benthic leaf standing stock in Hugh White Creek, a second-order, Appalachian Mountain stream in North Carolina, U. S. A. Leaf input and leaf breakdown data were used in a ,computer ,model to predict standing stocks. Predicted standing stocks were then compared,with measured,values. Once the model was modified to include leaves in four breakdown,rate

J. R. Webster; E. F. Benfield; J. J. Hutchens; J. L. Tank; S. W. Golladay; J. C. Adams

2001-01-01

151

Costs of Measuring Leaf Area Index of Corn.  

National Technical Information Service (NTIS)

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 e...

C. S. T. Daughtry S. E. Hollinger

1984-01-01

152

Wind induced deformation and vibration of a Platanus acerifolia leaf  

NASA Astrophysics Data System (ADS)

Deformation and vibration of twig-connected single leaf in wind is investigated experimentally. Results show that the Reynolds number based on wind speed and length of leaf blade is a key parameter to the aerodynamic problem. In case the front surface facing the wind and with an increase of Reynolds number, the leaf experiences static deformation, large amplitude and low frequency sway, reconfiguration to delta wing shape, flapping of tips, high frequency vibration of whole leaf blade, recovery of delta wing shape, and twig-leaf coupling vibration. Abrupt changes from one state to another occur at critical Reynolds numbers. In case the back surface facing the wind, the large amplitude and low frequency sway does not occur, the recovered delta wing shape is replaced by a conic shape, and the critical Reynolds numbers of vibrations are higher than the ones corresponding to the case with the front surface facing the wind. A pair of ram-horn vortex is observed behind the delta wing shaped leaf. A single vortex is found downstream of the conic shaped leaf. A lift is induced by the vortex, and this lift helps leaf to adjust position and posture, stabilize blade distortion and reduce drag and vibration.

Shao, Chuan-Ping; Chen, Ye-Jun; Lin, Jian-Zhong

2012-06-01

153

The wetting of leaf surfaces  

Microsoft Academic Search

Recent advances in the area of the wetting of leaf areas are reviewed with particular emphasis on their relation to agrochemical application. Areas reviewed include leaf wax composition, leaf wetting and superhydrophobicity, agrochemical deposit formation and spray retention. It is thought that most progress has been made in the area of leaf wetting through the work on lotus leaves. In

Philip Taylor

2011-01-01

154

In planta analysis of the Agrobacterium tumefaciens T-cyt gene promoter: identification of an upstream region essential for promoter activity in leaf, stem and root cells of transgenic tobacco  

Microsoft Academic Search

The promoter region of the Agrobacterium tumefaciens T-cyt gene was fused to a ß-glucuronidase (gusA) reporter gene and introduced into tobacco plants. Detection of gusA expression in transgenic F1 progeny revealed that the T-cyt promoter is active in many, if not all, cell types in leaves, stems and roots of fully developed plants. Developmental stage-dependent promoter activity was observed in

Saskia T. C. Neuteboom; Esther Hulleman; Rob A. Schilperoort; J. Harry C. Hoge

1993-01-01

155

Leaf and stem CO/sub 2/ uptake in the three subfamilies of the Cactaceae. [Pereskia aculeata; Pereskia grandifolia; Maihuenia poeppigii; Carnegiea gigantea; Ferocactus acanthodes; Coryphantha vivipara; Mammillaria dioica; Opuntia ficus-inidica; Pereskiopsis porteri; Quiabentia chacoensis; Austrocylindropuntia subulata  

SciTech Connect

Net CO/sub 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/sub 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/sub 2/ uptake was by the stems and at night. Similarly, for leafless Opuntia ficus-indica (subfamily Opuntioideae), all net CO/sub 2/ uptake occurred at night. For leafy members of the Opuntioideae (Pereskiopsis porteri, Quiabentia chacoensis, Austrocylindropuntia subulata), at least 88% of the shoot CO/sub 2/ uptake over 24 hours was by the leaves and some CO/sub 2/ uptake occurred at night. Leaves responded to the instantaneous level of photosynthetically active radiation (PAR) during the daytime, as occurs for C/sub 3/ plants, whereas nocturnal CO/sub 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/sub 3/ plants, the Cactoideae behaved as CAM plants, and the Opuntioideae exhibited characteristics of both pathways.

Nobel, P.S.; Hartsock, T.L.

1986-04-01

156

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

157

Leaf Absorbance and Photosynthesis.  

National Technical Information Service (NTIS)

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not ...

K. Schurer

1994-01-01

158

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

159

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

160

[Effects of stand density on Oligostachyum lubricum leaf carbon, nitrogen, and phosphorus stoichiometry and nutrient resorption].  

PubMed

Taking pure Oligostachyum lubricum forest as test object, this paper studied the matured and withered leaves carbon (C), nitrogen (N), and phosphorus (P) stoichiometry and N and P resorption patterns of 1-3 years old stands at the densities of 24600-29800 stem hm-2 (D, ), 37500-42600 stem hm-2 (D2 ), 46500 - 52800 stem hm-2 (D3), and 76500 - 85500 stem hm-2 (D4). With increasing stand density, the matured leaves C, N, and P contents and withered leaves C and P contents had an overall decrease, the withered leaves N content decreased after an initial increase, and the matured leaves C content at density )4 decreased dramatically. The leaf C/N and C/P ratio increased with increasing stand density, whereas the leaf N/P ratio increased first but decreased then. At stand densities D3 and D4, the leaf N and P utilization efficiencies were significantly higher than those at D, and D2. With increasing stand density, the leaf N resorption capacity increased after an initial decrease, while the leaf P resorption capacity increased steadily. At stand densities D,-D3, the matured leaves N/P ratio was 16.24-19.37, suggesting that the P limitation occurred, leaf establishment increased, and population increase and expansion enhanced. At density D4, the matured leaves N/P ratio was 13.42-15.74, implying that the N limitation strengthened, leaf withering and defoliation increased, and population increase inhibited. All the results indicated that O. lubricum could regulate its leaf C, N and P contents and stoichiometry and enhance the leaf N and P utilization efficiency and resorption capacity to adapt to the severe competition of environment resources at high stand density. In our experimental condition, 46500-52800 stem hm-2 could be the appropriate stand density for O. lubricum management. PMID:23898642

Guo, Zi-Wu; Chen, Shuang-Lin; Yang, Qing-Ping; Li, Ying-chun

2013-04-01

161

Mechanical role of the leaf sheath in rattans.  

PubMed

Leaf sheaths of rattans are long, tubular and persistent and unlike many self-supporting palms, extend far from the apex of the plant. The mechanical role of the leaf sheath was investigated in eight rattan species of the subfamily Calamoideae. The main objective was to analyse its influence on the mechanical architecture and contribution to the climbing habit. Bending mechanical properties were measured along climbing axes before and after removal of leaf sheaths. Results were related to stem and leaf sheath geometry and mechanical properties. Contribution of the leaf sheath to axial flexural rigidity was high (c. 90%) in the early stages of growth and towards the apex of older climbing axes for all climbing palms tested. Senescence and loss of the leaf sheath strongly influenced axial stiffness. A nonclimbing species, Calamus erectus, showed a different mechanical architecture. Although lacking secondary growth, palms have been able to develop successful climbers with a mechanical architecture broadly analogous to, although developmentally different from, dicotyledonous lianas. The role of the leaf sheath in modulating mechanical properties during ontogeny ought not to be neglected in studies on monocotyledons, as it possibly contributed significantly to the ways in which different growth forms have evolved in the group. PMID:18067530

Isnard, S; Rowe, N P

2007-12-07

162

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

163

ASSESSMENT OF PHYSIOLOGICAL STATUS OF CORN: NON-DESTRUCTIVE ESTIMATION OF LEAF CHLOROPHYLL CONTENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Leaf chlorophyll content provides valuable information about the physiological status of plants. Measurement of leaf spectral reflectance provides a non-destructive technique for chlorophyll estimation. A large number of spectral indices have been developed for the estimation of leaf chlorophyll con...

164

[Stem cell properties of therapeutic potential].  

PubMed

Stem cell research is a innovative technology that focuses on using undifferentiated cells able to self-renew through the asymmetrical or symmetrical divisions. Three types of stem cells have been studied in laboratory including embryonic stem cell, adult stem cells and induced pluripotent stem cells. Embryonic stem cells are pluripotent stem cells derived from the inner cell mass and it can give rise to any fetal or adult cell type. Adult stem cells are multipotent, have the ability to differentiate into a limited number of specialized cell types, and have been obtained from the bone marrow, umbilical cord blood, placenta and adipose tissue. Stem cell therapy is the most promising therapy for several degenerative and devastating diseases including digestive tract disease such as liver failure, inflammatory bowel disease, Celiac sprue, and pancreatitis. Further understanding of biological properties of stem cells will lead to safe and successful stem cell therapies. (Korean J Gastroenterol 2011;58: 125-132). PMID:21960099

Seo, Geom Seog

2011-09-25

165

Leaf ties as colonization sites for forest arthropods: an experimental study  

Microsoft Academic Search

Secondary colonization of leaf shelters constructed by caterpillars has been reported from a number of systems. Both the mechanism (larval or adult movement vs. oviposition) and the cues used by arthropods in locating leaf shelters,however,have received little attention. 2. Artificial leaf shelters (i.e. leaf ties or pairs of leaves clipped together to form sandwiches) were constructed on understorey white oak

JOHN T. L ILL; OBERT J. M ARQUIS

166

Leaf habit influences nitrogen remobilization in Vaccinium species.  

PubMed

The effect of N supply on plant growth and leaf demography of a deciduous and an evergreen Ericaceae was studied in relation to their internal cycling of N. Mature ramets of Vaccinium myrtillus (deciduous) and Vaccinium vitis-idaea (evergreen) were established in sand culture for 1 year with an adequate supply of a balanced nutrient solution. During one growing season, the plants were given two levels of N supply enriched with 15N and eight sequential destructive harvests were taken. Recovery of unlabelled N in the new shoot was used to determine the remobilization of N from storage. Initially, growth was unaffected by N supply. After May, High N enhanced growth for both species but the nature of their growth response differed. For both species, new shoot biomass and leaf number increased but root biomass production was affected for V. myrtillus only. Whole plant biomass production was similar for both species under High N, but was greater for V. vitis-idaea under Low N. The amount of N remobilized to support new shoot growth was similar for the two species and was independent of N current supply. N was remobilized predominantly from previous year leaves for V. vitis-idaea and from previous year stems and roots for V. myrtillus. The contribution of remobilization to new shoot N was similar for the two species, but depended on N supply. Remobilization was faster in V. myrtillus, but lasted longer in V. vitis-idaea. The results are discussed in relation to species growth in N-poor environments, focusing on the extent to which species-differences in the dynamic of N remobilization and growth may explain their adaptation to constant and/or changeable N supply. PMID:11432916

Grelet, G A; Alexander, I J; Proe, M F; Frossard, J S; Millard, P

2001-05-01

167

Renal Stem Cells and Kidney Regeneration  

Microsoft Academic Search

\\u000a Significant advances have been made in stem cell research over the past decade. A number of non-hematopoietic sources of stem\\u000a cells (or progenitor cells) have been identified including endothelial stem cells and neural stem cells. These discoveries\\u000a have been a major step towards the potential regeneration of organs for clinical applications using stem cells. The worldwide\\u000a shortage of donor kidneys

Takashi Yokoo; Akira Fukui; Kei Matsumoto; Tetsuya Kawamura

168

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

169

Stem Cell Task Force  

NSDL National Science Digital Library

This Web site from the National Institutes of Health (NIH) provides an overview of the activities of an NIH task force established to move the stem cell research agenda forward. The section titled Scientific Research may be of particular interest to researchers in this area. It provides links to the Web sites of stem cell-related research at a number of NIH institutes, as well as an extensive information index, a FAQs page about stem cell research, information on funding opportunities, and much more.

170

Physiological Studies with Isolated Leaf Cells  

PubMed Central

A number of plants have been surveyed with respect to isolation by mild grinding in large quantities of leaf cells. The extent of recovery of mesophyll cells per unit leaf area was found to vary with plant species and the method of grinding. Greater than 70% recovery was obtained from the leaves of Canna indica L., Crotalaria Laburnifolia L., and Thunbergia grandiflora Roxb. By pulse-chase time course experiments, the photosynthetically fixed primary carbon compounds of bean leaf cells were not converted into the ethanol-insoluble fraction. About 25% of total 14C-photoassimilates were found to leak out into the incubation medium. In contrast, Euglena and Chlorella cells incorporated their primary photosynthetic products into cellular macromolecules and the amount of “leak” was very little. 14C-Leucine supplied to the bean cells was absorbed readily and incorporated into the trichloroacetic acid insoluble fraction. Images

Kulandaivelu, G.; Gnanam, A.

1974-01-01

171

Cellulose Synthase-Like D1 is integral to normal cell division, expansion, and leaf development in maize.  

PubMed

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. PMID:22123901

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

2011-11-28

172

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

173

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

174

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

175

Cleared Leaf Collection  

NSDL National Science Digital Library

The University of California-Berkeley Museum of Paleontology has recently launched this online database of the Daniel I. Axelrod and the Berkeley leaf collections, which contain over 2000 modern leaf specimens bleached and stained to make their venation patterns more visible. Data records for both collections are now online, and images (including a higher resolution mode) will eventually become available for each specimen beginning with those in the Axelrod collection. Using the database is somewhat tricky, but a detailed help page is provided.

176

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

2013-07-30

177

Composition of speciose leaf litter alters stream detritivore growth, feeding activity and leaf breakdown.  

PubMed

Leaf litter derived from riparian trees can control secondary production of detritivores in forested streams. Species-rich assemblages of leaf litter reflect riparian plant species richness and represent a heterogeneous resource for stream consumers. Such variation in resource quality may alter consumer growth and thus the feedback on leaf breakdown rate via changes in feeding activity. To assess the consequences of this type of resource heterogeneity on both consumer growth and subsequent litter breakdown, we performed a laboratory experiment where we offered a leaf-shredding stream detritivore (the stonefly Tallaperla maria, Peltoperlidae) ten treatments of either single- or mixed-species leaf litter. We measured consumer growth rate, breakdown rate and feeding activity both with and without consumers for each treatment and showed that all three variables responded to speciose leaf litter. However, the number of leaf species was not responsible for these results, but leaf species composition explained the apparent non-additive effects. T. maria growth responded both positively and negatively to litter composition, and growth on mixed-litter could not always be predicted by averaging estimates of growth in single-species treatments. Furthermore, breakdown and feeding rates in mixed litter treatments could not always be predicted from estimates of single-species rates. Given that species richness and composition of senesced leaves in streams reflects riparian plant species richness, in-stream secondary production of detritivores and organic matter dynamics may be related to species loss of trees in the riparian zone. Loss of key species may be more critical to maintaining such processes than species richness per se. PMID:16425049

Swan, Christopher M; Palmer, Margaret A

2006-01-20

178

Ramularia Leaf Spot  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ramularia leaf spot of sugar beet, a disease caused by Ramularia beticola, is a sporadic problem in the United States, particularly in seed production. It is a more common problem in parts of Europe. Symptoms include light brown, angular spots on the leaves and can cause death of leaves. Epidemiol...

179

Leaf area index measurements  

Microsoft Academic Search

Leaf area index (LAI) is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LA1 estimates are required in studies of ecophysiology , atmosphere-ecosystem interactions, and global change. The objective of this paper is to evaluate LA1 values obtained by several research teams using

Jing M. Chen; Paul Steven Plummer; M. Rich; Stith T. Gower; John M. Norman

1997-01-01

180

Essential oil yield and chemical composition changes during leaf ontogeny of palmarosa (Cymbopogon martinii var. motia).  

PubMed

Changes in leaf biomass yield, essential oil yield, and chemical composition were investigated during leaf ontogeny of palmarosa {Cymbopogon martinii (Roxb.) Wats. var. motia Burk., family Poaceae}. Eleven leaves representing different developmental stages, serially numbered from the apex to the base of the plant were utilized for the study. Leaf biomass yield increased up to the eighth leaf. Essential oil recovery increased up to the third leaf; thereafter it decreased. Minimum essential oil recovery was observed in the eleventh leaf. Essential oil yield/leaf increased up to the sixth leaf. Essential oil yield and concentrations of linalool, alpha-terpineol, geranyl isobutyrate and geraniol were relatively higher in the essential oils of mature, older leaves. Essential oil recovery, and percentages of myrcene, beta-caryophyllene, geranyl acetate, (E,Z) farnesol and geranyl hexanoate were higher in the essential oils of young, expanding leaves. PMID:21299128

Rao, Bhaskaruni R Rajeswara; Rajput, Dharmendra K; Patel, Rajendra P; Purnanand, Somasi

2010-12-01

181

A model for leaf initiation  

PubMed Central

A biophysical model is proposed for how leaf primordia are positioned on the shoot apical
meristem in both spiral and whorl phyllotaxes. Primordia are initiated by signals that propagate
in the epidermis in both azimuthal directions away from the cotyledons or the most recently
specified primordia. The signals are linear waves as inferred from the spatial periodicity of the
divergence angle and a temporal periodicity. The periods of the waves, which represent actively
transported auxin, are much smaller than the plastochron interval. Where oppositely directed
waves meet at one or more angular positions on the periphery of the generative circle, auxin
concentration builds and as in most models this stimulates local movement of auxin to
underlying cells, where it promotes polarized cell division and expansion. For higher order
spirals the wave model requires asymmetric function of auxin transport; that is, opposite wave
speeds differ. An algorithm for determination of the angular positions of leaves in common leaf
phyllotaxic configurations is proposed. The number of turns in a pattern repeat, number of leaves
per level and per pattern repeat, and divergence angle are related to speed of auxin transport and
radius of the generative circle. The rule for composition of Fibonacci or Lucas numbers
associated with some phyllotaxes is discussed. A subcellular model suggests how the shoot
meristem might specify either symmetric or asymmetric transport of auxin away from the
forming primordia that produce it. Biological tests that could make or break the mathematical
and molecular hypotheses are proposed.

Abraham-Shrauner, Barbara; Pickard, Barbara G

2011-01-01

182

Plant stem cell maintenance involves direct transcriptional repression of differentiation program.  

PubMed

In animal systems, master regulatory transcription factors (TFs) mediate stem cell maintenance through a direct transcriptional repression of differentiation promoting TFs. Whether similar mechanisms operate in plants is not known. In plants, shoot apical meristems serve as reservoirs of stem cells that provide cells for all above ground organs. WUSCHEL, a homeodomain TF produced in cells of the niche, migrates into adjacent cells where it specifies stem cells. Through high-resolution genomic analysis, we show that WUSCHEL represses a large number of genes that are expressed in differentiating cells including a group of differentiation promoting TFs involved in leaf development. We show that WUS directly binds to the regulatory regions of differentiation promoting TFs; KANADI1, KANADI2, ASYMMETRICLEAVES2 and YABBY3 to repress their expression. Predictions from a computational model, supported by live imaging, reveal that WUS-mediated repression prevents premature differentiation of stem cell progenitors, being part of a minimal regulatory network for meristem maintenance. Our work shows that direct transcriptional repression of differentiation promoting TFs is an evolutionarily conserved logic for stem cell regulation. PMID:23549482

Yadav, Ram Kishor; Perales, Mariano; Gruel, Jérémy; Ohno, Carolyn; Heisler, Marcus; Girke, Thomas; Jönsson, Henrik; Reddy, G Venugopala

2013-01-01

183

Treatment of Oral Mucositis in Hematologic Patients Undergoing Autologous or Allogeneic Transplantation of Peripheral Blood Stem Cells: a Prospective, Randomized Study with a Mouthwash Containing Camelia Sinensis Leaf Extract  

PubMed Central

Oral mucositis is an important side effect of hematopoietic stem cell transplantation (HCST), mainly due to toxicity of conditioning regimens. It produces significant pain and morbidity. The present study reports a prospective, randomized, non-blinded study testing the efficacy of a new mouthwash, called Baxidil Onco® (Sanitas Farmaceutici Srl, Tortona, Italy) in 60 hematologic patients undergoing HCST (28 autologous, 32 allogeneic). Baxidil Onco®, used three times a day from Day -1 to Day +30, in addition to standard prophylactic schedules, was administered to 14 patients undergoing autologous and 14 patients undergoing allogeneic HCST. The remaining 32 patients (14 autologous and 18 HCST) were treated only with standard prophylactic schedules and served as control. In our study, the overall incidence of oral mucositis, measured according to the World Health Organization 0-4 scale, was 50% in the Baxidl Onco® group versus 82% in the control group (P=0.022). In addition, a significant reduction in scale 2-4 oral mucositis was observed in the Baxidil Onco® group (25% vs 56.2%; P=0.0029). The results obtained indicate that incidence, severity and duration of oral mucositis induced by conditioning regimens for HCST can be significantly reduced by oral rinsing with Baxidil Onco®, in addition to the standard prophylaxis scheme. Since Camelia Sinensin extract, which is used to produce green tea, is the main agent in this mouthwash, we hypothesize that the anti-oxidative properties of polyphenolic compounds of tea might exert protective effects on oral mucosa.

Carulli, Giovanni; Rocco, Melania; Panichi, Alessia; Chios, Chiara Feira; Ciurli, Ester; Mannucci, Chiara; Sordi, Elisabetta; Caracciolo, Francesco; Papineschi, Federico; Benedetti, Edoardo; Petrini, Mario

2013-01-01

184

Treatment of oral mucositis in hematologic patients undergoing autologous or allogeneic transplantation of peripheral blood stem cells: a prospective, randomized study with a mouthwash containing camelia sinensis leaf extract.  

PubMed

Oral mucositis is an important side effect of hematopoietic stem cell transplantation (HCST), mainly due to toxicity of conditioning regimens. It produces significant pain and morbidity. The present study reports a prospective, randomized, non-blinded study testing the efficacy of a new mouthwash, called Baxidil Onco(®) (Sanitas Farmaceutici Srl, Tortona, Italy) in 60 hematologic patients undergoing HCST (28 autologous, 32 allogeneic). Baxidil Onco(®), used three times a day from Day -1 to Day +30, in addition to standard prophylactic schedules, was administered to 14 patients undergoing autologous and 14 patients undergoing allogeneic HCST. The remaining 32 patients (14 autologous and 18 HCST) were treated only with standard prophylactic schedules and served as control. In our study, the overall incidence of oral mucositis, measured according to the World Health Organization 0-4 scale, was 50% in the Baxidl Onco(®) group versus 82% in the control group (P=0.022). In addition, a significant reduction in scale 2-4 oral mucositis was observed in the Baxidil Onco(®) group (25% vs 56.2%; P=0.0029). The results obtained indicate that incidence, severity and duration of oral mucositis induced by conditioning regimens for HCST can be significantly reduced by oral rinsing with Baxidil Onco(®), in addition to the standard prophylaxis scheme. Since Camelia Sinensin extract, which is used to produce green tea, is the main agent in this mouthwash, we hypothesize that the anti-oxidative properties of polyphenolic compounds of tea might exert protective effects on oral mucosa. PMID:23888242

Carulli, Giovanni; Rocco, Melania; Panichi, Alessia; Chios, Chiara Feira; Ciurli, Ester; Mannucci, Chiara; Sordi, Elisabetta; Caracciolo, Francesco; Papineschi, Federico; Benedetti, Edoardo; Petrini, Mario

2013-04-04

185

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

2012-12-13

186

Volatile Oils from the Root, Stem and Leaves of Schefflera stellata (Gaertn.) Harms (Araliaceae): Chemical Characterization and Antimicrobial Activity  

Microsoft Academic Search

Volatile oils from the roots, stem and leaves of Schefflera stellata (Gaertn.) Harms were isolated by hydrodistillation and characterized by analytical gas chromatography and gas chromatography-mass spectroscopy. Sixty-nine (98.3%), seventy-eight (97.9%) and sixty-seven (98.0%) constituents were identified from the root, stem and leaf oils, respectively. Sesquiterpene hydrocarbons were the most abundant compounds in the root (73.8%), stem (68.8%) and leaf

Baby Sabulal; Varughese George; Nediyaparambu Sukumaran Pradeep; Mathew Dan

2008-01-01

187

Physically based Animation of Broad-leaf Plant  

Microsoft Academic Search

Summary This paper describes the modeling and animation of broad-leaf plant moving with the wind. There are many instances where animations of vegetation and foliage are limited to simple textures in non real-time. To address this limitation, we show how to use a physically based animation method to realistically simulate the movement of stem and foliage in real-time. Our emphasis

Guo Wu; Li WenHui; Feng Guanghui

2006-01-01

188

Recovery of diurnal depression of leaf hydraulic conductance in a subtropical woody bamboo species: embolism refilling by nocturnal root pressure.  

PubMed

Despite considerable investigations of diurnal water use characteristics in different plant functional groups, the research on daily water use strategies of woody bamboo grasses remains lacking. We studied the daily water use and gas exchange of Sinarundinaria nitida (Mitford) Nakai, an abundant subtropical bamboo species in Southwest China. We found that the stem relative water content (RWC) and stem hydraulic conductivity (K(s)) of this bamboo species did not decrease significantly during the day, whereas the leaf RWC and leaf hydraulic conductance (K(leaf)) showed a distinct decrease at midday, compared with the predawn values. Diurnal loss of K(leaf) was coupled with a midday decline in stomatal conductance (g(s)) and CO(2) assimilation. The positive root pressures in the different habitats were of sufficient magnitude to refill the embolisms in leaves. We concluded that (i) the studied bamboo species does not use stem water storage for daily transpiration; (ii) diurnal down-regulation in K(leaf) and gs has the function to slow down potential water loss in stems and protect the stem hydraulic pathway from cavitation; (iii) since K(leaf) did not recover during late afternoon, refilling of embolism in bamboo leaves probably fully depends on nocturnal root pressure. The embolism refilling mechanism by root pressure could be helpful for the growth and persistence of this woody monocot species. PMID:22499596

Yang, Shi-Jian; Zhang, Yong-Jiang; Sun, Mei; Goldstein, Guillermo; Cao, Kun-Fang

2012-04-11

189

Distribution of stomata on the second leaf of Zea mays following root hypoxia  

Microsoft Academic Search

The changes in leaf dimensions, transverse and longitudinal gradients in stomatal density and the total number of stomata\\u000a under the influence of root hypoxia were followed. In spite of considerably reduced leaf area following hypoxia the total\\u000a number of stomata per leaf was not changed significantly. The resulting increase in stomatal density was not uniform being\\u000a the most prominent in

O. Votrubová; J. Kade?ábek; J. Albrrechtová

1992-01-01

190

Excising the Root from STEM  

ERIC Educational Resources Information Center

There are a number of well-intentioned STEM initiatives, some designed to improve the recruitment and retention of science teachers. Sometimes it appears that the initiators are remote from direct contact with the "grass roots" issues that feed the "stem" on which the blossoms of young enthusiastic recruits to the science teaching profession are…

Lock, Roger

2009-01-01

191

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

192

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

193

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

194

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

195

Ecological Impact of Climate Change on Leaf Economic Strategies Across the Paleocene Eocene Thermal Maximum, Bighorn Basin, Wyoming  

Microsoft Academic Search

Deciphering the ecological impacts of climate change is a key priority for paleontologists and ecologists alike. An important ecological metric in vegetated settings is the leaf economics spectrum, which represents an adaptive continuum running from rapid resource acquisition to maximized resource retention. This spectrum is comprised of a large number of coordinated traits, including leaf mass per area (LMA), leaf

D. L. Royer; E. D. Currano; P. Wilf; S. L. Wing; C. C. Labandeira; E. C. Lovelock

2007-01-01

196

Leaf surface and histological perturbations of leaves of Phaseolus vulgaris and Helianthus annuus after exposure to simulated acid rain  

Microsoft Academic Search

Initial injury to adaxial leaf surfaces of Phaseolus vulgaris and Helianthus annuus occurred near trichomes and stomata after exposure to simulated sulfate acid rain. Lesion frequency was not correlated with density of either stomata or trichomes but was correlated with degree of leaf expansion. The number of lesions per unit area increased with total leaf area. Results suggest that characteristics

Lance S. Evans; Nicholas F. Gmur; Filomena Da Costa

1977-01-01

197

Effects of leaf area profiles and canopy stratification on simulated energy fluxes: the problem of vertical spatial scale  

Microsoft Academic Search

We investigated the effects of the shape of leaf area profiles and the number of canopy layers on simulated sensible and latent heat fluxes using a gradient diffusion-based biometeorological model. Three research questions were addressed through simulation experiments: (1) Given the same amount of cumulative leaf area in the vertical direction, how does the shape of the leaf area profile

Jianguo Wu; Yuanbo Liu; Dennis E. Jelinski

2000-01-01

198

Leaf Phenology of the Climbing Fern Lygodium venustum in a Semideciduous Lowland Forest on the Gulf of Mexico  

Microsoft Academic Search

Leaf phenology in a population of the climbing fern Lygodium venustum was observed during a 31-month period in Veracruz, Mexico. The study site is located 100-200 m from the Gulf coast in the understory of a semideciduous lowland forest dominated by trees of Enterolobium and Ficus. Four leaf parameters: leaf growth of main and secondary axes, number of living leaves,

Klaus Mehltreter

2006-01-01

199

Relationships of net CO/sub 2/ assimilation and leaf expansion to vegetative growth in Lycospersicum esculentum, var Jubilee  

SciTech Connect

Relationships between net plant CO/sub 2/ exchange rate (CER) and canopy development were examined in jubilee tomato over the initial 4 weeks of vegetative growth. A comparison was made between two plant groups that were alternatively exposed to 200 or 800 microeinsteins per square meter per second midday irradiation to establish a differential in net CER. Plants exposed to higher irradiation demonstrate a 2- and 4-fold greater net photosynthetic rate per leaf area and 100% average higher net CO/sub 2/ assimilation rate/plant day. However, leaf-stem growth differed by <50% suggesting a poor relationship to CER. Leaf area growth rate (LAGR) of individual leaves appeared closely related to CER during initial leaf expansion but a greater function of odor of emergence in successive leaf growth. LAGR on a per plant basis increased linearly with leaf dry weight but appeared more limited by factors determining maximum leaf enlargement and rate of new leaf development. Net CO/sub 2/ assimilation/leaf area and leaf starch consistently declined with time while net CO/sub 2/ assimilation plant/day approached a constant rate following 2 to 3 weeks growth. Composite results suggested a simple relationship for successive growth where accumulated leaf carbohydrate in excess of 200 milligrams/plant day could be expected to be partitioned to other plant segments. 30 references, 5 figures, 1 table.

Campbell, D.E.; Lyman, M.; Corse, J.; Hautala, E.

1986-01-01

200

Signal transduction in leaf senescence.  

PubMed

Leaf senescence is a complex developmental phase that involves both degenerative and nutrient recycling processes. It is characterized by loss of chlorophyll and the degradation of proteins, nucleic acids, lipids, and nutrient remobilization. The onset and progression of leaf senescence are controlled by an array of environmental cues (such as drought, darkness, extreme temperatures, and pathogen attack) and endogenous factors (including age, ethylene, jasmonic acid, salicylic acid, abscisic acid, and cytokinin). This review discusses the major breakthroughs in signal transduction during the onset of leaf senescence, in dark- and drought-mediated leaf senescence, and in various hormones regulating leaf senescence achieved in the past several years. Various signals show different mechanisms of controlling leaf senescence, and cross-talks between different signaling pathways make it more complex. Key senescence regulatory networks still need to be elucidated, including cross-talks and the interaction mechanisms of various environmental signals and internal factors. PMID:23096425

Zhang, Haoshan; Zhou, Chunjiang

2012-10-25

201

The worldwide leaf economics spectrum.  

PubMed

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate. PMID:15103368

Wright, Ian J; Reich, Peter B; Westoby, Mark; Ackerly, David D; Baruch, Zdravko; Bongers, Frans; Cavender-Bares, Jeannine; Chapin, Terry; Cornelissen, Johannes H C; Diemer, Matthias; Flexas, Jaume; Garnier, Eric; Groom, Philip K; Gulias, Javier; Hikosaka, Kouki; Lamont, Byron B; Lee, Tali; Lee, William; Lusk, Christopher; Midgley, Jeremy J; Navas, Marie-Laure; Niinemets, Ulo; Oleksyn, Jacek; Osada, Noriyuki; Poorter, Hendrik; Poot, Pieter; Prior, Lynda; Pyankov, Vladimir I; Roumet, Catherine; Thomas, Sean C; Tjoelker, Mark G; Veneklaas, Erik J; Villar, Rafael

2004-04-22

202

Prostate Stem Cells and Cancer in Animals  

Microsoft Academic Search

The mouse prostate has been the primary focus of research in regards to both normal stem cells and cancer stem cell-like cell\\u000a populations in the animal prostate. The proximal region is the probable location of stem cells because it contains a high\\u000a number of label-retaining cells, which express stem-cell specific markers, that are resistant to androgen ablation and have\\u000a a

Alexander Yu. Nikitin; Melia G. Nafus; Zongxiang Zhou; Chun-Peng Liao; Pradip Roy-Burman

203

Recovery of Photosynthesis in Sunflower after a Period of Low Leaf Water Potential 1  

PubMed Central

Photosynthesis was studied in sunflower plants subjected to 1 to 2 days of desiccation and then permitted to recover. The leaf water potential to which leaves returned after rewatering was dependent on the severity of desiccation and the evaporative conditions. Under moderately evaporative conditions, leaf water potential returned to predesiccation levels after 3 to 5 hours when desiccation was slight. Leaf water potentials remained below predesiccation levels for several days after rewatering when leaf water potentials decreased to ?13 to ?19 bars during desiccation. Leaf water potential showed no sign of recovery when leaf water potentials decreased to ?20 bars or below during desiccation. The lack of full recovery of leaf water potential was attributable to increased resistance to water transport in the roots and stem. The resistance ultimately became large enough to result in death of the leaves because net water loss continued even after the soil had been rewatered. Measurements of photosynthesis were made at high light intensities, where stomatal aperture often affects photosynthesis, and at low light intensities, where the photochemical activity of the leaves limits photosynthesis. Providing leaf water potentials remained above ?12 bars during the desiccation period and returned to predesiccation levels during recovery, photosynthesis under both low and high light paralleled the recovery in leaf water potential after rewatering. After desiccation to leaf water potentials below ?12 bars, recovery was incomplete under high light and could be attributed to lack of full stomatal opening. Lack of full opening persisted for 3 days and showed no sign of eventual recovery even though leaf water potentials recovered fully. Under low light, however, recovery in photochemical activity was complete within 15 hours after desiccation to leaf water potentials as low as ?17 bars.

Boyer, J. S.

1971-01-01

204

From thin to thick: major transitions during stem development  

PubMed Central

The variability of shoot architecture in plants is striking and one of the most extreme examples of adaptive growth in higher organisms. Mediated by the differential activity of apical and lateral meristems, flexibility in stem growth essentially contributes to this variability. In spite of this importance, the regulation of major events in stem development is largely unexplored. Recently, however, novel approaches exploiting knowledge from root and leaf development are starting to shed light on molecular mechanisms that regulate this essential plant organ. In this review, we summarize our understanding of initial patterning events in stems, discuss prerequisites for the initiation of lateral stem growth and highlight the burning questions in this context.

Sanchez, Pablo; Nehlin, Lilian; Greb, Thomas

2012-01-01

205

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

2013-05-23

206

Salt allocation during leaf development and leaf fall in mangroves  

Microsoft Academic Search

By taking samples along individual branches and measuring leaf size, thickness and Na+ and K+ concentrations, we have shown in Bruguiera cylindrica, Avicennia rumphiana and Avicennia marina that there are two phases of salt accumulation by leaves. This is confirmed by re-analysis of published data for other species. The first phase is a rapid increase in leaf content as it

John W. Cram; Peter G. Torr; Derek A. Rose

2002-01-01

207

Number Models  

NSDL National Science Digital Library

Students are given a worksheet with a representation of a number in base-ten blocks. Students are asked to write the number with numerals and determine how the number changes, when blocks are added and taken away.

Sherdan, Danielle

2010-07-26

208

Effect of CO sub 2 enriched air on the kinetics of leaf expansion. [Pisum sativa; Glycine max  

SciTech Connect

Vegetative plants of Pisum sativum (pea) and Glycine max (soybean) were transferred from 350 to 1,200 ppm CO{sub 2} when they had one (pea) or two (soybean) mature leaves and several developing leaves. Controls were kept at 350 ppm. For pea, high CO{sub 2} for 8 days increased dry mass of root, stem, and leaf fractions by 30-50%. Leaf dry mass increase was due primarily to carbohydrate, particularly starch. Dawn levels of starch increased 10-fold within 1 day at high CO{sub 2} and 20-fold at 2 days. At 2 days after transfer leaf starch levels were 1.0 mg cm{sup {minus}2} of leaf area or nearly 30% of leaf dry weight. Soybean data are less complete, but 10 days at high CO{sub 2} increased leaf + stem dry mass by 50% and leaf weight per unit area increased by 14 and 48% at dawn within 1 and 2 days, respectively, at high CO{sub 2}. However 8-10 days at high CO{sub 2} increased total leaf area only slightly (about 15%) for both species, with all the leaf area increase occurring at nodes that were nearly microscopic at the time of transfer. For soybean, most of the increased leaf area due to high CO{sub 2} was from lateral bud break despite a high CO{sub 2} did not stimulated more leaves per plant. Apparently, extra photosynthate had a delayed effect on leaf expansion and did not increase nodes along the main axis. Leaf expansion under high CO{sub 2} was not limited by photosynthate.

Potter, J.R. (Dept. of Agriculture, Corvallis, OR (United States))

1991-05-01

209

The artificial leaf.  

PubMed

To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a corner-sharing, head-to-tail dimer. The ability to perform the oxygen-evolving reaction in water at neutral or near-neutral conditions has several consequences for the construction of the artificial leaf. The NiMoZn alloy may be used in place of Pt to generate hydrogen. To stabilize silicon in water, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in water and holding it up to sunlight can effect direct solar energy conversion via water splitting. By constructing a simple, stand-alone device composed of earth-abundant materials, the artificial leaf provides a means for an inexpensive and highly distributed solar-to-fuels system that employs low-cost systems engineering and manufacturing. Through this type of system, solar energy can become a viable energy supply to those in the non-legacy world. PMID:22475039

Nocera, Daniel G

2012-04-04

210

The worldwide leaf economics spectrum  

Microsoft Academic Search

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional

Ian J. Wright; Peter B. Reich; Mark Westoby; David D. Ackerly; Zdravko Baruch; Frans Bongers; Jeannine Cavender-Bares; Terry Chapin; Johannes H. C. Cornelissen; Matthias Diemer; Jaume Flexas; Eric Garnier; Philip K. Groom; Javier Gulias; Kouki Hikosaka; Byron B. Lamont; Tali Lee; William Lee; Christopher Lusk; Jeremy J. Midgley; Marie-Laure Navas; Ülo Niinemets; Jacek Oleksyn; Noriyuki Osada; Pieter Poot; Lynda Prior; Vladimir I. Pyankov; Catherine Roumet; Sean C. Thomas; Mark G. Tjoelker; Erik J. Veneklaas; Rafael Villar

2004-01-01

211

Leaf retention and cassava productivity  

Microsoft Academic Search

Increased longevity of leaves, or improved leaf retention, has been suggested as a possible means to increase productivity of cassava (Manihot esculenta Crantz). This study evaluated variation in leaf retention and its relation to cassava productivity under irrigated and stressed conditions. In the first trial 1350 clones were evaluated on the North Coast of Colombia with a 5-month dry period

J. I. Lenis; F. Calle; G. Jaramillo; J. C. Perez; H. Ceballos; J. H. Cock

2006-01-01

212

Simulating Leaf Appearance in Rice  

Microsoft Academic Search

Most rice (Oryza sativa L.) simulation models assume that only temperature aff ects leaf appearance rate (LAR). Th is assumption ignores results from controlled environment studies that show that LAR in rice is not constant with time (calendar days) under constant temperature. Th e Streck model, which takes into account age eff ects on LAR, improved the prediction of leaf

Nereu Augusto Streck; Leosane Cristina Bosco; Isabel Lago

2008-01-01

213

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

214

Effects of Irrigation Treatments and Rates of Nitrogen Fertilization on Young Hass Avocado Trees. II. Relation to Leaf Tipburn, Tree Sunburn, Shoot Dieback, Leaf Scorch, Leaf Color, Leaf Size, Tree Vigor, and Leaf Moisture Deficits  

Microsoft Academic Search

Periodic observations were made during the years 1955 and 1956. The presence and extent of leaf tipburn, tree sunburn, shoot dieback, leaf scorch, leaf color, leaf size, and tree vigor were noted. Leal: moisture deficits were determined during part of the 1956 irrigation season. LEAF TIPBURN Leaf tipburn, due to the accumulation of Cl and SO4 in mature leaves, is

P. W. Moore; S. J. Richards

215

Identification of Differentially Expressed Transcripts from Maturing Stem of Sugarcane by in silico Analysis of Stem Expressed Sequence Tags and Gene Expression Profiling  

Microsoft Academic Search

Sugarcane accumulates high concentrations of sucrose in the mature stem and a number of physiological processes on-going in maturing stem tissue both directly and indirectly allow this process. To identify transcripts that are associated with stem maturation, we compared patterns of gene expression in maturing and immature stem tissue by expression profiling and bioinformatic analysis of sets of stem ESTs.

Rosanne E. Casu; Christine M. Dimmock; Scott C. Chapman; Christopher P. L. Grof; C. Lynne McIntyre; Graham D. Bonnett; John M. Manners

2004-01-01

216

Number Factory  

NSDL National Science Digital Library

This interactive game develops fluency and flexibility with whole number operations. In each round the player is given 4 single-digit whole numbers, presented in the context of a factory. The player uses each number exactly once with the interactive calculator to arrive as close as possible to a given target number.

Doorman, Michiel

2003-01-01

217

Mimicking Stem Cell Niches to Increase Stem Cell Expansion  

PubMed Central

Summary Niches regulate lineage-specific stem cell self-renewal vs. differentiation in vivo and are comprised of supportive cells and extracellular matrix components arranged in a 3-dimensional topography of controlled stiffness in the presence of oxygen and growth factor gradients. Mimicking stem cell niches in a defined manner will facilitate production of the large numbers of stem cells needed to realize the promise of regenerative medicine and gene therapy. Progress has been made in mimicking components of the niche. Immobilizing cell-associated Notch ligands increased the self-renewal of hematopoietic (blood) stem cells. Culture on a fibrous scaffold that mimics basement membrane texture increased the expansion of hematopoietic and embryonic stem cells. Finally, researchers have created intricate patterns of cell-binding domains and complex oxygen gradients.

Dellatore, Shara M.; Garcia, A. Sofia; Miller, William M.

2008-01-01

218

Another call to increase STEM education  

NASA Astrophysics Data System (ADS)

As science, technology, engineering, and mathematics (STEM) education becomes increasingly important, U.S. students are lagging behind other nations on international assessments, according to a recent Trends in International Mathematics and Science study. A 22 June report from the U.S. National Research Council (NRC) calls for increasing the focus on STEM education in the United States. “To make progress in improving STEM education for all students, policy makers at the national, state, and local levels should elevate science to the same level of importance as reading and mathematics,” states the report, “Successful K-12 STEM Education: Identifying Effective Approaches in Science, Technology, Engineering, and Mathematics.” It outlines several goals: expand the number of students who pursue advanced degrees and careers in STEM fields; expand the STEM-capable workforce, while also broadening the participation of women and minorities; and increase STEM literacy for all students, whether or not they pursue STEM-related careers or additional study in those areas.

Showstack, Randy

2011-07-01

219

Number Sense  

NSDL National Science Digital Library

In this online math game from Cyberchase, learners play against Hacker in a place value game. The goal is to make a number bigger than the one created by Hacker's number machine. Learners select the numbers in the order in which they want them to go into their machine. The challenge is to either make a number larger than the one on Hacker's machine or realize that it's impossible to make a number bigger than Hacker's, no matter what the combination.

Wnet.org

2011-01-01

220

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

221

Phaeoramularia fruit and leaf spot of citrus with special reference to Kenya  

Microsoft Academic Search

Fruit and leaf spot of citrus caused by Phaeoramularia angolensis was first observed in Angola and Mozambique in 1952. The disease has now spread to 15 countries, south of Sahara, and recently to Yemen, in the Arabian Peninsula. All citrus species are affected with grapefruit, with orange being the most susceptible. P. angolensis infects foliage, fruit and stems. Severe infection

A. A. Seif; R. J. Hillocks

1993-01-01

222

Temperature influences on leaf CO 2exchange, cell viability and cultivation range for Agave tequilana  

Microsoft Academic Search

Agave tequilana, a species exhibiting crassulacean acid metabolism, is cultivated in Mexico for its stem and attached leaf bases from which the distilled beverage tequila is obtained. The physiological reasons why its cultivation was mostly restricted to regions in Jalisco with minimum air temperatures in 1996 above ?4°C and maximum temperatures below 36°C was investigated using plants under controlled conditions

Park S. Nobel; Miguel Castañeda; Gretchen North; Eulogio Pimienta-Barrios; Ariel Ruiz

1998-01-01

223

Radio-Frequency Dielectric Properties of Some Tropical African Leaf Vegetables.  

National Technical Information Service (NTIS)

The variation of the relative permittivity epsilon'sub(r), the loss factor epsilon'' and a.c. conductivity sigma with the frequency of an applied electromagnetic field over the range 0.5 to 50 MHz has been studied in the leaf and stem tissues of three tro...

A. A. Laogun N. O. Ajayi

1985-01-01

224

Shoot Meristem Function and Leaf Polarity: The Role of Class III HD–ZIP Genes  

Microsoft Academic Search

The shoot apical meristem comprises an organized cluster of cells with a central region population of self-maintaining stem cells providing peripheral region cells that are recruited to form differentiated lateral organs. Leaves, the principal lateral organ of the shoot, develop as polar structures typically with distinct dorsoventrality. Interdependent interactions between the meristem and developing leaf provide essential cues that serve

Mary E. Byrne

2006-01-01

225

Leaf herbivory and decomposability in a Malaysian tropical rain forest.  

PubMed

There is accumulating evidence that similar suites of plant traits may affect leaf palatability and leaf litter decomposability. However, the possible association between leaf herbivory and litter decomposition rates across species in species-diverse natural ecosystems such as tropical rain forests remains unexplored, despite its importance in estimating the herbivory effects on carbon and nutrient cycling of ecosystems. We found no strong association between leaf herbivory and litter decomposition rates across 40 tree species in a Malaysian tropical rain forest, even though the leaf and litter traits were tightly correlated. This is because the leaf and litter traits related to herbivory and decomposition rates in the field were inconsistent. Leaf toughness accounted for only a small part of the variation in the herbivory rate, whereas a number of litter traits (the leaf mass per area, lignin to nitrogen ratio, and condensed tannin concentration) accurately predicted the decomposition rate across species. These results suggest that herbivory rate across species may not be strongly related to single leaf traits, probably because plant-herbivore interactions in tropical rain forests are highly diverse; on the other hand, plant-decomposer interactions are less specific and can be governed by litter chemicals. We also investigated two factors, phylogeny and tree functional types, that could affect the relationship between herbivory and decomposition across species. Phylogenetic relatedness among the species did not affect the relationship between herbivory and decomposition. In contrast, when the plants were segregated according to their leaf emergence pattern, we found a significant positive relationship between herbivory and decomposition rates for continuous-leafing species. In these species, the condensed tannin to N ratios in leaves and litter were related to herbivory and decomposition rates, respectively. However, we did not observe a similar trend for synchronous-leafing species. These results suggest that the relationship between herbivory and decomposition may be more greatly affected by functional types than by phylogenetic relatedness among species. In conclusion, our results suggest that well-defended leaves are not necessarily less decomposable litter in a tropical rain forest community, implying that herbivory may not generate positive feedback for carbon and nutrient cycling in this type of ecosystem. PMID:18831185

Kurokawa, Hiroko; Nakashizuka, Tohru

2008-09-01

226

Laryngeal brain stem evoked response.  

PubMed

Sensory stimuli to the larynx evoke a laryngeal adductor reflex mediated by the brain stem via superior and recurrent laryngeal nerves. Aberrant laryngeal reflexes have been proposed to explain a number of poorly understood disorders, including "reflex apnea," idiopathic laryngospasm, and sudden infant death syndrome. The purpose of the present study was to evaluate far field brain stem recordings following stimulation of the superior laryngeal nerve to determine whether laryngeal brain stem response is a valid measure of laryngeal activity at the brain stem level. The nerve was stimulated electrically in adult cats, and the resultant laryngeal adductor response as well as far field brain stem activity was recorded. For the latter, six reproducible positive and five reproducible negative waves were obtained via posterior pharyngeal (+) and posterior cervical (-) recording electrodes. Response threshold and latencies were measured and evaluated as a function of stimulus parameters. Wave latencies corresponded closely to those reported in prior near and far field evoked response recordings. PMID:2782801

Anonsen, C K; Lalakea, M L; Hannley, M

1989-09-01

227

Strengthening the STEM Education & Workforce Pipeline: Insights from the BHEF U.S. STEM Education Model Led to the STEM Higher Education and Workforce Project.  

National Technical Information Service (NTIS)

Business-Higher Education Forum's STEM Initiative seeks to answer two questions: Could we double the number of college graduates in the STEM disciplines in 10 years. What would be the highest leverage strategies to achieve this goal.

2011-01-01

228

Genetic control of duration of pre-anthesis phases in wheat (Triticum aestivum L.) and relationships to leaf appearance, tillering, and dry matter accumulation  

PubMed Central

The duration of pre-anthesis developmental phases is of interest in breeding for improved adaptation and yield potential in temperate cereals. Yet despite numerous studies on the genetic control of anthesis (flowering) time and floral initiation, little is known about the genetic control of other pre-anthesis phases. Furthermore, little is known about the effect that changes in the duration of pre-anthesis phases could have on traits related to leaf appearance and tillering, or dry matter accumulation before terminal spikelet initiation (TS). The genetic control of the leaf and spikelet initiation phase (LS; from sowing to TS), the stem elongation phase (SE; from TS to anthesis), and, within the latter, from TS to flag leaf appearance and from then to anthesis, was studied in two doubled-haploid, mapping bread wheat populations, Cranbrook×Halberd and CD87×Katepwa, in two field experiments (ACT and NSW, Australia). The lengths of phases were estimated from measurements of both TS and the onset of stem elongation. Dry weight per plant before TS, rate of leaf appearance, tillering rate, maximum number of tillers and number of leaves, and dry weight per plant at TS were also estimated in the Cranbrook×Halberd population. More genomic regions were identified for the length of the different pre-anthesis phases than for total time to anthesis. Although overall genetic correlations between LS and SE were significant and positive, independent genetic variability between LS and SE, and several quantitative trait loci (QTLs) with different effects on both phases were found in the two populations. Several of these QTLs (which did not seem to coincide with reported major genes) could be of interest for breeding purposes since they were only significant for either LS or SE. There was no relationship between LS and the rate of leaf appearance. LS was strongly and positively correlated with dry weight at TS but only slightly negatively correlated with early vigour (dry weight before TS). Despite significant genetic correlations between LS and some tillering traits, shortening LS so as to lengthen SE without modifying total time to anthesis would not necessarily reduce tillering capacity, as QTLs for tillering traits did not coincide with those QTLs significant only for LS or SE. Therefore, the study of different pre-anthesis phases is relevant for a better understanding of genetic factors regulating developmental time and may offer new tools for fine-tuning it in breeding for both adaptability and yield potential.

Borras-Gelonch, Gisela; Rebetzke, Greg J.; Richards, Richard A.; Romagosa, Ignacio

2012-01-01

229

Influence of the holly leaf miner, Phytomyza ilicis (Diptera Agromyzidae), on leaf abscission  

Microsoft Academic Search

Holly trees were sampled at two heights for 11 annual generations of Phytomyza ilicis Curtis. The number of mines per 1000 leaves, mine intensity, was consistently more at the lower height. Mine-induced leaf abscission led to a reduction in mine intensity from 1- to 2-year-old leaves. Abscission was shown to have been greater in samples taken from higher in the

R. James; I. M. Pritchard

1988-01-01

230

NUMBER SENSE  

NSDL National Science Digital Library

Students will practice counting to 100, making numbers with base ten blocks and practicing ordinal numbers! Math is FUN! Lets have fun practicing counting to 100 ! Click when you are ready!Counting Now that you have practiced counting to 100, lets use the base ten blocks to make the number that is on the screen. Click when you are ready!Working with Base Ten Blocks We have now practiced counting and making numbers, lets ...

Simpson, Ms.

2007-10-27

231

Leftist Numbers  

ERIC Educational Resources Information Center

|The leftist number system consists of numbers with decimal digits arranged in strings to the left, instead of to the right. This system fails to be a field only because it contains zerodivisors. The same construction with prime base yields the p-adic numbers.|

Rich, Andrew

2008-01-01

232

Number Time  

ERIC Educational Resources Information Center

|This article features Number Time, a site developed by the British Broadcasting Corporation (BBC) for young mathematics learners, located at www.bbc.co.uk/schools/numbertime. The site uses interactive animation to help children in pre-K through grade 2 understand and practice number basics. Users will find online games, videos that tell number

Herrera, Terese A.

2004-01-01

233

Number theory  

Microsoft Academic Search

Number theory, an abstract branch of mathematics that deals with relationships between whole numbers, has provided highly useful answers to numerous real-world problems. The author briefly reviews earlier uses of number theory and then examines recent applications to music, cryptography, and error-correction codes

M. R. Schroeder

1989-01-01

234

Number Factory  

NSDL National Science Digital Library

This interactive Java applet promotes number sense, estimation, and provides practice with order of operations. The player's goal is to make a numerical expression using the four given numbers and the four basic operations with the result being the target number (or as close as they can get to it). The student can also use brackets in their calculation.

Doorman, Michiel

2012-01-07

235

Dianthus caryophyllus stems and Zantedeschia aethiopica petioles\\/pedicels show anatomical features indicating efficient photosynthesis  

Microsoft Academic Search

The fine structure of the green stem of Dianthus caryophyllus, the leaf petiole and the flower pedicel of Zantedeschia aethiopica were studied using light and scanning electron microscopy. It was revealed that these non-foliar plant parts of both species possess epidermis with numerous stomata. Stomatal density of D. caryophyllus stem was found to be relatively high (79 vs 100 per

Charilaos Yiotis; George K. Psaras

2011-01-01

236

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

2003-05-24

237

Attractants for rice leaf bug, Trigonotylus caelestialium (Kirkaldy), are emitted from flowering rice panicles.  

PubMed

Volatiles were extracted from rice plants of various growth stages with solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS) to identify attractants that cause invasion of the rice leaf bug Trigonotylus caelestialium (Kirkaldy) into paddy fields. The composition of volatile blends produced by rice plants changed with rice development. In addition, volatile blend compositions differed between the panicles and the stems and leaves. The relative geranyl acetone content was high in all plant structures analyzed. In volatiles from whole plants in the fourth-leaf stage and panicles in the full-ripe stage, the relative content of green leaf volatiles (GLVs) was higher than that found in other rice plant structures. In contrast, relative terpene levels emitted from whole plants in the panicle-formation stage and by panicles and stems and leaves in the flowering stage were higher than those of other rice plant structures. However, the type of terpenes found differed between the panicles and the stems and leaves. Relative levels of ?-caryophyllene in whole plants in the panicle-formation stage and panicles in the flowering stage were much higher than that in stems and leaves in the flowering stage. Our previous studies demonstrated that the odor from whole plants in the panicle-formation stage and panicles in the flowering stage is attractive to rice leaf bugs. Here, the attractiveness of ?-caryophyllene to adult bugs was investigated in olfactometer assays. Adult females were attracted to ?-caryophyllene at a concentration of 0.001%, which is approximately equivalent to the concentration produced by flowering rice panicles. However, ?-caryophyllene also was present in the odor of whole plants in the fourth-leaf stage and in stems and leaves in the flowering stage. Furthermore, the amounts of this compound emitted from these structures were similar. Therefore, we suggest that the relative abundance of this compound in a volatile blend is important for attractance of the bugs. PMID:20680414

Fujii, Tatsuya; Hori, Masatoshi; Matsuda, Kazuhiro

2010-08-01

238

Superharmonic numbers  

NASA Astrophysics Data System (ADS)

Let tau(n) denote the number of positive divisors of a natural number n>1 and let sigma(n) denote their sum. Then n is superharmonic if sigma(n)mid n^ktau(n) for some positive integer k . We deduce numerous properties of superharmonic numbers and show in particular that the set of all superharmonic numbers is the first nontrivial example that has been given of an infinite set that contains all perfect numbers but for which it is difficult to determine whether there is an odd member.

Cohen, Graeme L.

2009-03-01

239

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

240

Isolation of 6-hydroxykynurenic acid from the tobacco leaf  

PubMed Central

1. 6-Hydroxykynurenic acid (4,6-dihydroxyquinoline-2-carboxylic acid, 6-HKA) was isolated in crystalline form from both green and cured tobacco leaves. 2. A method for the determination of 6-HKA by paper chromatography and fluorimetry is described. 3. The content of 6-HKA in the flowers, stem and roots of the tobacco plant was much lower than that in the leaf. 4. The 6-HKA content increased throughout leaf development and senescence. 5. 6-HKA was detected in the leaves of plants representing 11 out of 27 families sampled. 6. 6-HKA was found to be devoid of antibacterial and antifungal activity, and was inactive in the Avena-coleoptile and cress-seed-germination tests. 7. The presence of 6-HKA is taken as evidence in plants of the tryptophan-catabolic pathway already known in mammals and micro-organisms.

Macnicol, P. K.

1968-01-01

241

The biochemical transformation of oak ( Quercus robur) leaf litter consumed by the pill millipede ( Glomeris marginata)  

Microsoft Academic Search

Soil macrofauna play an essential role in the initial comminution and degradation of organic matter entering the soil environment and yet the chemical effects of digestion on leaf litter are poorly understood at the molecular level. This study was undertaken to assess the selective chemical transformations that saprophagous soil invertebrates mediate in consumed leaf litter. A number of pill millipedes

Andrew J. Rawlins; Ian D. Bull; Natacha Poirier; Philip Ineson; Richard P. Evershed

2006-01-01

242

Regulation of Brassica rapa chloroplast proliferation in vivo and in cultured leaf disks  

Microsoft Academic Search

Summary. To understand the regulatory mechanisms of chloroplast proliferation, chloroplast replication was studied in cultured leaf disks cut from plants of 25 species. In leaf disks from Brassica rapa var. perviridis, the number of chloroplasts per cell increased remarkably in culture. We examined chloroplast replication in this plant in vivo and in culture media with and without benzyladenine, a cytokinin.

F. Yagisawa; T. Mori; T. Higashiyama; H. Kuroiwa; T. Kuroiwa

2003-01-01

243

Treatment with Plerixafor in non-Hodgkin's Lymphoma and Multiple Myeloma Patients to Increase the Number of Peripheral Blood Stem Cells When Given a Mobilizing Regimen of G-CSF: Implications for the Heavily Pretreated Patient  

Microsoft Academic Search

We investigated the efficacy and toxicity of combining granulocyte-colony stimulating factor (G-CSF) at standard doses with plerixafor, a CXCR4 inhibitor, to mobilize stem cells in patients with non-Hodgkin's lymphoma (NHL) and multiple myeloma (MM). Patients with NHL and MM underwent mobilization with G-CSF (10 ?g\\/kg\\/day) for up to 9 days and plerixafor (240 ?g\\/kg\\/day), which started on the evening of

Patrick Stiff; Ivana Micallef; Philip McCarthy; Margarida Magalhaes-Silverman; Daniel Weisdorf; Mary Territo; Karin Badel; Gary Calandra

2009-01-01

244

Human embryonic stem cells  

Microsoft Academic Search

The property of pluripotency confers the capacity for differentiation into a large number of cell types including extra-embryonic,\\u000a somatic and germinal cells. During normal development, pluripotency is acquired by the cells of the early embryo, which shortly\\u000a thereafter undergo differentiation, whereas embryonic stem cells (ESCs) uniquely maintain pluripotency while undergoing extensive\\u000a in vitro proliferation. Studies using ESCs have begun to

Ludovic Vallier; Roger A. Pedersen

2005-01-01

245

Number Patterns  

NSDL National Science Digital Library

This Java applet allows users to practice recognizing patterns with integers and completing a sequence of numbers by adding or subtracting a common difference. The user is given the first five terms of a number pattern and asked to complete the pattern with the next two numbers. There is a check answer button for feedback and a new pattern button for additional practice. Instructions for users and teacher information are available through links at the top of the page.

2005-09-30

246

Number Grid  

NSDL National Science Digital Library

With this interactive Flash applet, intended for use with a projector or interactive white board, teachers can help students understand place value and the structure of our number system. Shapes can be placed on the 100 chart; students use number patterns to determine which numbers are hidden under the shapes. By choosing Hide or Highlight and then selecting specific rows or columns to hide or highlight, the teacher can adjust the challenge level or bring attention to parts of the chart.

2012-01-01

247

Why do leaf-tying caterpillars abandon their leaf ties?  

PubMed Central

Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm2 leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf tie due to food limitation and interactions with other caterpillars, but this is a costly behavior.

Sliwinski, Michelle

2013-01-01

248

Number Cruncher  

NSDL National Science Digital Library

In this online puzzle game, learners need to choose a path from a starting number to a goal number. Along the path are simple operations (e.g. add 1, subtract 2, multiply by 2) to change the current number to a new number. This is a good challenge for young learners. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. As a larger assessment, learners can complete the Bug Blaster game after they've completed several activities.

Science, American A.

2009-01-01

249

Response of Leaf Ontogeny and Photosynthetic Activity to Reproductive Growth in Cotton  

PubMed Central

This study was conducted to determine if reproductive growth in cotton (Gossypium hirsutum L.) affects concurrent leaf development. Apparent photosynthesis (AP), stomatal conductance (Cs), soluble protein (SP), ribulose bisphosphate carboxylase (RuBisCO), and chlorophyll (Chl) were monitored in four main-stem cotton leaves which emerged at approximately 2 week intervals. The leaf which emerged during vegetative growth (48 days after planting) had higher AP, SP, and RuBisCO levels than that present in any leaves which emerged during fruit development. The last leaf studied (89 days after planting) was still present after boll maturation was completed and exhibited a rejuvenation in AP, SP, RuBisCO, and Chl starting at 30 days after leaf emergence. At 96 days after planting, the P700 Chl a-protein complex (PSI) was virtually absent from the leaves that emerged at 48 and 62 days after planting. The light harvesting Chl a/b complex was still present in these leaves, indicating greater degradation of PSI. The data emphasize the influence of developing fruit on concurrently developing leaves, an effect which was alleviated after boll maturation was completed. The declining AP per unit leaf area and smaller leaf size at the top of the plant results in a reduced photosynthetic potential of successively later emerging leaves. This reduction in leaf AP is consistent with earlier reported seasonal canopy photosynthesis patterns. Images Fig. 1 Fig. 7

Wells, Randy

1988-01-01

250

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

251

Number Watch  

NSDL National Science Digital Library

John Brignell, Professor Emeritus from the Department of Electronics & Computer Science at the University of Southampton, is the author of this informal website "devoted to the monitoring of the misleading numbers that rain down on us via the media." Brignell says he aims to "nail" a few of the "Single Issue Fanatics (SIFs), politicians, bureaucrats, quasi-scientists (junk, pseudo- or just bad)," who use misleading numbers to write catchy articles or who try to keep numbers away from public notice. Since April 2000, he has been posting a "number of the month" as well as a "number for the year," which offer his commentary on media usage of misleading numbers and explanations for why the numbers are misleading. He also posts book reviews and an extensive list of online resources on statistics and statistics education. The FAQ section includes answers to some interesting questions, such as "Is there such a thing as average global temperature?" and some more basic questions such as "What is the Normal Distribution and what is so normal about it?" The Bits and Pieces section includes a variety of short articles on statistics and his definitions for some terms he uses on the website. Visitors are also invited to join the discussion forum (complete with a few advertisements) and view comments by others who want to discuss "wrong numbers in science, politics and the media." A few comments sent to Brignell and his responses are also posted online. This site is also reviewed in the February 11, 2005_NSDL MET Report_.

252

Characterization of stem rust resistant derivatives of wheat cultivar Amigo  

Microsoft Academic Search

Originally developed for resistance to greenbug derived from Insave rye, Amigo wheat carries two genes for resistance to stem rust. One of these genes is associated with a rye chromosome 1RS segment carrying the Sec-1 protein marker and presumably greenbug resistance. The second gene which is genetically linked to leaf rust resistance is associated with an Agropyron-derived segment. Rust tests

T. T. The; R. B. Gupta; P. L. Dyck; R. Appels; U. Hohmann; R. A. McIntosh

1991-01-01

253

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

254

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

255

In vitro organogenesis from leaf explants of Annona squamosa Linn  

Microsoft Academic Search

Multiple shoot formation was induced from excised leaf explants of Annona squamosa Linn. (custard apple) seedlings on a Murashige and Skoog basal medium containing benzylaminopurine and kinetin. Various auxins in combination with the above medium produced callusing of the explants. In an investigation of environmental factors affecting shoot induction it was seen that the maximum number of shoots were obtained

S. Nair; P. K. Gupta; M. V. Shirgurkar; A. F. Mascarenhas

1985-01-01

256

Measuring leaf material in ginned cotton from surface images  

Microsoft Academic Search

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

Robert A. Taylor

1995-01-01

257

Structural Adaptation of the Leaf Mesophyll to Shading  

Microsoft Academic Search

Structural characteristics of the mesophyll were studied in five boreal grass species experiencing a wide range of light and water supply conditions. Quantitative indices of the palisade and spongy mesophyll tissues (cell and chloroplast sizes, the number of chloroplasts per cell, the total cell and chloroplast surface area per unit leaf surface area) were determined in leaves of each of

L. A. Ivanova; V. I. P'yankov

2002-01-01

258

NON-DESTRUCTIVE ASSESSMENT OF ARUNDO DONAX (POACEAE) LEAF QUALITY.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Leaf quality information (i.e., leaf C content, leaf N content, leaf C:N ratio) is especially useful for understanding plant-herbivore interactions and may be important in developing control methods for the invasive riparian plant Arundo donax L. We measured leaf C content, leaf N content, leaf C:N ...

259

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

260

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.

261

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

262

Number Patterns  

NSDL National Science Digital Library

Students are given a worksheet and asked to identify and extend the growing or repeating numerical patterns. Students develop their own number pattern and create a model showing the pattern and the next three stages of the pattern.

Cornwell, Susan

2010-07-22

263

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

264

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

265

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

266

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

267

Vitis Resistance to Pierce's Disease Is Characterized by Differential Xylella fastidiosa Populations in Stems and Leaves.  

PubMed

ABSTRACT The pattern of Xylella fastidiosa infection in resistant and susceptible grapevines representing a diverse selection of Vitis spp. was characterized through measurements of X. fastidiosa bacterial movement and accumulation in artificially inoculated greenhouse-grown grapevines. A double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was optimized for quantification of X. fastidiosa populations and tested on known amounts of X. fastidiosa added to grape tissue extracts. Predicted versus known X. fastidiosa concentrations proved to be highly correlated (R(2) = 0.99). Populations of X. fastidiosa in stem internode, stem node, petiole, and leaf blade samples from the genotypes in this study were measured at 12 weeks postinoculation using the optimized ELISA procedure. Samples from each plant part were taken at eight positions along the inoculated shoots. Systemic infection was detected in both susceptible and resistant genotypes. Resistant genotypes were characterized by significant differences in X. fastidiosa populations between stem internodes and leaves (1.0 x 10(6) and 1.1 x 10(7) cells/g of sample, respectively). In contrast, the susceptible genotypes were characterized by high mean X. fastidiosa populations in both stems and leaves (5.6 x 10(7) and 4.8 x 10(7) cells/g, respectively) the latter of which were not significantly different from the resistant genotypes. A high correlation (R(2) = 0.97) between stem X. fastidiosa numbers to previously characterized field Pierce's disease (PD) performance indicates that the quantitative ELISA measurements of X. fastidiosa in greenhouse-grown grapevines should be a useful tool for predicting PD resistance under field conditions. PMID:18943835

Krivanek, A F; Walker, M A

2005-01-01

268

Stemming the Stem Cell Setback  

Microsoft Academic Search

This Comment highlights the recent federal funding setbacks in the biotechnology industry and considers the resulting challenges to future research collaboration. After providing a historical background to stem cell technology, Mr. Fleis examines the passionately opposed public responses to the technology's use of embryos and to its future applications. Fleis continues by noting past legislative initiatives that have accelerated the

Patrick J. Fleis

2003-01-01

269

Influence of elevated CO{sub 2} on leaf starch of field-grown cotton  

SciTech Connect

Experiments were conducted to determine the effects of free-air carbon dioxide enrichment (FACE) upon cotton grown in fields near Yazoo City, MS and Maricopa, AZ. Among the measured responses was the starch content of cotton leaves. Leaf starch is an important carbon pool in cotton, since its degradation during the night and subsequent translocation of the products from the leaf is the major process supplying substrates for energy necessary for nocturnal growth and metabolism in this species. The nocturnal carbon supply is of particular importance in cotton as it provides the energy for a number of significant growth events which occur during dark periods, including flowering, fruit set and leaf growth. Earlier work has shown that the magnitude of cotton leaf carbon export during dark periods could be established by comparing the starch content in leaf samples collected from the same leaf at dusk and dawn. The difference between evening and morning leaf starch content equals the nocturnal contribution of carbon from that particular leaf to the growth and respiration of the plant. Moreover, the cotton growth model COTCO2 accounts for such diurnal changes in the starch pool and observations of actual leaf starch content can provide data with which to validate this aspect of the model. 6 refs., 3 figs.

Hendrix, D.L. [Western Cotton Lab., Phoenix, AZ (United States)

1992-12-31

270

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

271

Expression analysis of RING zinc finger genes from Triticum aestivum and identification of TaRZF70 that contains four RING-H2 domains and differentially responds to water deficit between leaf and root  

Microsoft Academic Search

RING zinc finger proteins are known for their role predominantly in targeted protein degradation and participate in gene regulation through interaction with other regulatory proteins. In this study seven RING zinc finger genes from Triticum aestivum (bread wheat) were analysed for expression profiles in various organs (leaf, root, stem, spike, endosperm and embryo) and during leaf development and aging as

Jason Kam; Peter Gresshoff; Ray Shorter; Gang-Ping Xue

2007-01-01

272

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

273

[Stem cell therapy: an update].  

PubMed

Medicine will be faced with a major challenge in coming years, namely how to treat for tissue dysfunction due to disease and aging There are two basic options: drug therapy and cell therapy. Stem cells have been the subject of intense speculation and controversy for several years, as they open up radically new therapeutic possibilities. Classical drugs can only smoothen consequences of tissue dysfunction, whereas cell therapy has the potential to restore tissue function by providing fresh cells. Cell therapy is totally different from organ transplantation, which can only benefit a limited number of patients. The use of the generic term "stem cells" to designate a whole variety of cell types that are present throughout life, is a source of confusion and ambiguity. It will take years of cognitive research to unravel the molecular mechanisms that govern a stem cell's multi- or totipotent status before we can fully exploit this therapeutic tool to the full. The younger a stem cell the greater its potential and, probably, the more durable its benefits, but the use of embryonic stem cells raises ethical issues. The redundancy or equivalence of diferent categories of cells is another source of controversy, yet researchers must be able to study stem cells in all their diversity, as complementary rather than competitive alternatives, in an acceptable ethical and regulatory environment. We briefly describe the three types of stem cells: pluripotent embryonic stem cells, fetal and adult stem cells, and pluripotent reprogrammed adult somatic cells. Only the former two categories have physiological functions: the first gives rise to tissues and organs while the second maintains tissue function during adulthood PMID:19883007

Coulombel, Laure

2009-03-01

274

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

275

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

276

Stem Cells  

Microsoft Academic Search

\\u000a To fully understand the biological meaning of the term stem cell (SC) it is useful to clarify the derivation of the root staminal, even though modern research published in English-speaking journals never seem to use the term staminal. While there are\\u000a no doubts that the term SC originated in the context of two major embryological questions, the continuity of the

Manuela Monti; Carlo Alberto Redi

277

Ultraviolet radiation as a limiting factor in leaf expansion and development.  

PubMed

Reductions in leaf growth are a commonly observed response to ultraviolet radiation, but the underlying mechanisms remain poorly defined. This study examined the response of leaves exposed to a UV environment across a range of organizational scales, including leaf expansion rate, epidermal cell size and number, biomechanical properties, leaf-water relations and activity of cell-wall peroxidases. Two experimental approaches were used; Lettuce (Lactuca sativa L.) plants were propagated under (a) supplementary UV-B (9 kJ m(-2) day(-1)) in controlled environment (CE) conditions, and (b) field conditions, where plants were placed under three horticultural films with differing UV transmissions. In both experiments, UV-B caused the greatest reductions in leaf expansion and final leaf size, with some reductions attributable to UV-A wavelengths. In supplementary UV-B conditions, adaxial cell size was reduced, while in field plants, both cell size and cell number were lower in an increased UV environment, as was the case with abaxial cells in CE plants. Although leaf turgor and leaf extensibility were not affected by UV wavelengths, breaking strain of leaf tissue was decreased under supplementary UV-B. Cell-wall peroxidase activity was increased in both supplementary UV conditions and in the field, where only a zero UV environment showed no upregulation of cell-wall peroxidase. PMID:18764892

Wargent, Jason J; Moore, Jason P; Roland Ennos, A; Paul, Nigel D

2008-08-27

278

Differential response of pitted morning glory and ivy leaf morning glory to acifluorfen, fomesafen, and lactofen  

SciTech Connect

Field and laboratory investigations were conducted to examine the response of soybeans (Glycine max (L.) Merr.), pitted morning glory (Ipomoea lacunosa L.number/sup 1/ IPOLA), and ivy leaf morning glory (Ipomoea hederacea (L.) Jacq. number IPOHE) to acifluorfen, fomesafen, and lactofen. In field studies, greatest soybean injury was observed with acifluorfen and lactofen. All treatments provided 80% or greater control of pitted morning glory 15 days after treatment. Only acifluorfen and fomesafen at 0.6 kg ai ha/sup -1/ provided 80% or greater ivy leaf morning glory. The differential response of pitted morning glory and ivy leaf morning glory to these diphenyl ether herbicides was reflected in soybean seed yields. In laboratory studies, 71 to 84% of applied /sup 14/C-acifluorfen was not absorbed into the leaf surface of ivy leaf morning glory. Thirty-two to 46% of applied acifluorfen was recovered from the leaf surface of pitted morning glory. Sixty-four percent of applied /sup 14/C-lactofen was recovered from leaf surfaces of both morning glory species 96 h after treatment. Treated leaves of pitted morning glory contained 35 to 37% more /sup 14/C-acifluorfen than ivy leaf morning glory. Less than 28% of applied /sup 14/C-lactofen was absorbed into treated leaves of both morning glory species at 24, 48, and 96 h harvests.

Higgins, J.M.

1987-01-01

279

Number Fun  

NSDL National Science Digital Library

We will work on number sense. Play a fun counting game. IXL Counting Review Help Curious George count chicks! Count Your Chickens! Help Sagwa count the fish. Counting Fish Rescue the octopi by counting! Octopus Count Play the five frame games! Five Frame Game ...

Hoffmann, Mrs.

2011-08-05

280

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

281

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

282

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.

283

Number Sense!  

NSDL National Science Digital Library

Perform operations with whole numbers, simple fractions, and decimals. 1. Begin your work at the Comparing Fractions website. Complete 10 problems. 2. When you are finished Comparing Fractions, I\\'m sure you will hunger for more! Click on the website, Who Wants Pizza? These activities are sure to fill your brain with nutritious information. 3. Explore Egyptian ...

Painter, Ms.

2006-10-27

284

Number Pairs  

NSDL National Science Digital Library

With this interactive Flash applet students make use of complements of 10 to develop fluency with addition within 100. Users "repair" a water slide by selecting pairs of numbers that add to 20 in the first round, and then to 100. In successive rounds they may choose to practice with any multiple of 10 from 30 to 90.

Bunker, Dan

2010-01-01

285

Blood Ties: Banking the Stem Cell Promise  

Microsoft Academic Search

This paper explores the banking of cord blood stem cells by new parents, a growing phenomenon that raises a number of questions for scholars interested in the role of expectations in innovation. In particular, we focus on the relationships between imagination and materiality, the way in which today's expectations of a future stem cell revolution have become embodied (materialised) in

Nik Brown; Alison Kraft

2006-01-01

286

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

287

Boosting STEM Interest in High School  

ERIC Educational Resources Information Center

|One of the most critical labor shortages facing the U.S. involves the number of young adults entering careers in what's now commonly referred to as STEM (science, technology, engineering, and mathematics). Equally troubling is that the participation of blacks and Hispanics in STEM careers continues to lag that of whites and Asians. High school is…

Schneider, Barbara; Judy, Justina; Mazuca, Christina

2012-01-01

288

Diet, Stem Cells, and Breast Cancer Prevention.  

National Technical Information Service (NTIS)

Breast cancer is considered to be initiated by mutations in a limited population of undifferentiated cells termed stem cells that 'sit' at the top of the mammary epithelial hierarchy. Over-expansion of the stem cell population leads to increased numbers o...

R. C. Simmen

2009-01-01

289

Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales  

PubMed Central

The Gnomoniaceae are characterised by ascomata that are generally immersed, solitary, without a stroma, or aggregated with a rudimentary stroma, in herbaceous plant material especially in leaves, twigs or stems, but also in bark or wood. The ascomata are black, soft-textured, thin-walled, and pseudoparenchymatous with one or more central or eccentric necks. The asci usually have a distinct apical ring. The Gnomoniaceae includes species having ascospores that are small, mostly less than 25 ?m long, although some are longer, and range in septation from non-septate to one-septate, rarely multi-septate. Molecular studies of the Gnomoniaceae suggest that the traditional classification of genera based on characteristics of the ascomata such as position of the neck and ascospores such as septation have resulted in genera that are not monophyletic. In this paper the concepts of the leaf-inhabiting genera in the Gnomoniaceae are reevaluated using multiple genes, specifically nrLSU, translation elongation factor 1-alpha (tef1-?), and RNA polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences were generated for 322 isolates. Six genera of leaf-inhabiting Gnomoniaceae are defined based on placement of their type species within the multigene phylogeny. The new monotypic genus Ambarignomonia is established for an unusual species, A. petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is presented and 22 species of Gnomoniaceae are described and illustrated.

Sogonov, M.V.; Castlebury, L.A.; Rossman, A.Y.; Mejia, L.C.; White, J.F.

2008-01-01

290

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

291

cDNA-AFLP-based numerical comparison of leaf and root organ cDNAs in Catharanthus roseus.  

PubMed

Comparative transcriptome study of the leaf and root tissues of Catharanthus roseus is a prerequisite for causing any favorable tissue-specific change in the secondary metabolism of this species. This study was aimed at comparative analysis of the leaf and root cDNAs in C. roseus, using a cDNA-AFLP approach. Using 64 primer combinations (EcoRI and MseI), a total of 784 distinct transcriptionally-defined fragments (TDFs) could be detected in the root and leaf tissue transcript populations. The leaf tissue yielded a larger number of TDFs than the root tissue (556 versus 464), indicating a greater variety of expressing genes in the leaf. The leaf-specific TDFs (320) outnumbered the root-specific TDFs (228), indicating a higher number of leaf-specific functions and the relative complexity of the leaf tissue vis-à-vis the root tissue. Among the 236 TDFs that were detected in both types of tissues, 42 had nearly equal expression levels in both the tissues (L=R). Common TDFs having higher expression levels in the leaf (L>R; 124) outnumbered those having higher expression levels in the root (Lleaf transcriptome over the root transcriptome. PMID:22734886

Shukla, Ashutosh K; Shasany, Ajit K; Khanuja, Suman P S

2012-06-26

292

Effects of mechanical stress or abscisic acid on growth, water status and leaf abscisic acid content of eggplant seedlings.  

PubMed

Container-grown eggplant (Solanum melongena L. var esculentum Nees. 'Burpee's Black Beauty') seedlings were conditioned with brief, periodic mechanical stress or abscisic acid (ABA) in a greenhouse prior to outdoor exposure. Mechanical stress consisted of seismic (shaking) or thigmic (stem flexing) treatment. Exogenous ABA (10(-3) or 10(-4)M) was applied as a soil drench 3 days prior to outdoor transfer. During conditioning, only thigmic stress reduced stem elongation and only 10(-3) M ABA reduced relative growth rate (RGR). Both conditioning treatments increased leaf specific chlorophyll content, but mechanical stress did not affect leaf ABA content. Outdoor exposure of unconditioned eggplant seedlings decreased RGR and leaf-specific chlorophyll content, but tended to increase leaf ABA content relative to that of plants maintained in the greenhouse. Conditioning did not affect RGR of plants subsequently transferred outdoors, but did reduce stem growth. Seismic stress applied in the greenhouse reduced dry weight gain by plants subsequently transferred outdoors. Mechanical stress treatments increased leaf water potential by 18-25% relative to that of untreated plants. PMID:11539768

Latimer, J G; Mitchell, C A

1988-01-01

293

Wounding-induced xylem occlusion in stems of cut chrysanthemum flowers: roles of peroxidase and cathechol oxidase  

Microsoft Academic Search

A wounding-induced xylem occlusion, resulting in severe leaf wilting, occurs in stems of cut chrysanthemum flowers (Dendranthema grandiflora), cv. Vyking. The blockage develops after about 1 h in flowers held in air at 20°C. It is initially located in the lowermost 2 cm of the stem and upon prolonged exposure to air it is also found above 2 cm. We

Wouter G van Doorn; Nicolas Vaslier

2002-01-01

294

Bead Numbers  

NSDL National Science Digital Library

This page links to an interactive Flash abacus that helps develop and reinforce pupils' understanding of place value. [Click "Start the Activity" to begin.] The abacus has three pegs (representing units, tens and hundreds) onto which users drop beads. The activity has two areas: a "free" (unstructured) area where pupils can represent 3-digit numbers, and a "computer questions" area that presents six challenging tasks to carry out. The page includes notes for teachers and pupils.

Netmedia

2011-01-01

295

Value Numbering  

Microsoft Academic Search

SUMMARY Value numbering is a compiler-based program analysis method that allows redundant computations to be removed. This paper compares hash-based approaches derived from the classic local algorithm1 with partitioning approaches based on the work of Alpern, Wegman, and Zadeck2. Historically, the hash-based algorithm has been applied to single basic blocks or extended basic blocks. We have improved the technique to

Preston Briggs; Keith D. Cooper; L. Taylor Simpson

1997-01-01

296

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Leaf tobacco. 30.2 Section 30.2 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of...

2013-01-01

297

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

298

7 CFR 29.3648 - Thin Leaf (C Group).  

Code of Federal Regulations, 2013 CFR

...tolerance. C2F Fine Quality Medium-brown Thin Leaf. ...injury tolerance. C3F Good Quality Medium-brown Thin Leaf. ...injury tolerance. C3G Good Quality Green Thin Leaf. Underripe, medium body, firm leaf...

2013-01-01

299

The effects of aging on stem cell behavior in Drosophila  

Microsoft Academic Search

Throughout life, adult stem cells play essential roles in maintaining tissue and organ function by providing a reservoir of cells for homeostasis and regeneration. A decline in stem cell number or activity may, therefore, lead to compromised organ and tissue function that is characteristic of aging. Drosophila has emerged as an ideal system for studying the relationship between stem cells

Lei Wang; D. Leanne Jones

2011-01-01

300

Age Changes in Stem Cells of Murine Small Intestinal Crypts  

Microsoft Academic Search

Cell senescence is seen in many types of differentiated cells but age changes in stem cells have not previously been clearly demonstrated. Changes in stem cells may be of great importance for the ageing process, because any decline with age in the numbers and functional integrity of stem cells can lead to progressive deterioration of function and of proliferative homeostasis

K. Martin; T. B. L. Kirkwood; C. S. Potten

1998-01-01

301

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

302

Characteristics of leaf structure and photosynthetic apparatus within the crown of systematically shaded Quercus petraea and Nothofagus procera seedlings  

Microsoft Academic Search

Four-year-old seedlings ofQuercus petraea (Matt.) Liebl. andNothofagus procera (Poepp. et Endl.) Querst were grown outdoors in pots while subjected to full, medium and low irradiances. Shading and decrease\\u000a in height of leaf attachment generally increased specific leaf area, the diameters of chloroplasts and of palisade and spongy\\u000a mesophyll cells, but decreased leaf thickness, number of palisade cell layers, length of

A. B. I. Igboanugo

1992-01-01

303

SEMI-ROLLED LEAF1 Encodes a Putative Glycosylphosphatidylinositol-Anchored Protein and Modulates Rice Leaf Rolling by Regulating the Formation of Bulliform Cells1[W][OA  

PubMed Central

Leaf rolling is an important agronomic trait in rice (Oryza sativa) breeding and moderate leaf rolling maintains the erectness of leaves and minimizes shadowing between leaves, leading to improved photosynthetic efficiency and grain yields. Although a few rolled-leaf mutants have been identified and some genes controlling leaf rolling have been isolated, the molecular mechanisms of leaf rolling still need to be elucidated. Here we report the isolation and characterization of SEMI-ROLLED LEAF1 (SRL1), a gene involved in the regulation of leaf rolling. Mutants srl1-1 (point mutation) and srl1-2 (transferred DNA insertion) exhibit adaxially rolled leaves due to the increased numbers of bulliform cells at the adaxial cell layers, which could be rescued by complementary expression of SRL1. SRL1 is expressed in various tissues and is expressed at low levels in bulliform cells. SRL1 protein is located at the plasma membrane and predicted to be a putative glycosylphosphatidylinositol-anchored protein. Moreover, analysis of the gene expression profile of cells that will become epidermal cells in wild type but probably bulliform cells in srl1-1 by laser-captured microdissection revealed that the expression of genes encoding vacuolar H+-ATPase (subunits A, B, C, and D) and H+-pyrophosphatase, which are increased during the formation of bulliform cells, were up-regulated in srl1-1. These results provide the transcript profile of rice leaf cells that will become bulliform cells and demonstrate that SRL1 regulates leaf rolling through inhibiting the formation of bulliform cells by negatively regulating the expression of genes encoding vacuolar H+-ATPase subunits and H+-pyrophosphatase, which will help to understand the mechanism regulating leaf rolling.

Xiang, Jing-Jing; Zhang, Guang-Heng; Qian, Qian; Xue, Hong-Wei

2012-01-01

304

Fermat Numbers and Mersenne Numbers.  

National Technical Information Service (NTIS)

An IBM 7090 computer program, and results of testing Mersenne numbers M sub p = (2 raised to the power p) - 1 with p prime, p < 5000, have been described by Hurwitz. This paper describes modifications made to his program, and further computational results...

J. L. Selfridge A. Hurwitz

1968-01-01

305

Microenvironment Design for Stem Cell Fate Determination.  

PubMed

Stem cells are characterized by their dual ability for self-renewal and differentiation, potentially yielding large numbers of cells that can be used in cell therapy and tissue engineering for repairing devastating diseases. Attaining control over stem cell fate decision in culture is a great challenge since these cells integrate a complex array of "niche" signals, which regulate their fate. Given this, the recent findings that synthetic microenvironments can be designed to gain some level of control over stem cell fate are encouraging. This chapter provides an overview of the current state and knowledge of the design of synthetic microenvironments bio-inspired by the adult stem cell niche. We describe the biomaterials used for reconstituting the niche, highlighting the bioengineering principles used in the process. Such synthetic microenvironments constitute powerful tools for elucidating stem cell regulatory mechanisms that should fuel the development of advanced culture systems with accurate regulation of stem cell fate. PMID:21975955

Re'em, Tali; Cohen, Smadar

2011-10-01

306

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

307

Influence of leaf trichomes on predatory mite density and distribution in plant assemblages and implications for biological control  

Microsoft Academic Search

Non-glandular trichomes on leaves or stems are strongly positively correlated with the abundance of many predatory phytoseiid mite species. Some perennial fruit crops have few or no trichomes and overcoming this limitation of leaf habitat for natural enemy mites could improve biological control of pest mites in agricultural crops. This study evaluated whether juxtaposing plants with and without trichomes will

R. Loughner; K. Wentworth; G. Loeb; J. Nyrop

2010-01-01

308

Amnion-derived stem cells: in quest of clinical applications  

PubMed Central

In the promising field of regenerative medicine, human perinatal stem cells are of great interest as potential stem cells with clinical applications. Perinatal stem cells could be isolated from normally discarded human placentae, which are an ideal cell source in terms of availability, the fewer number of ethical concerns, less DNA damage, and so on. Numerous studies have demonstrated that some of the placenta-derived cells possess stem cell characteristics like pluripotent differentiation ability, particularly in amniotic epithelial (AE) cells. Term human amniotic epithelium contains a relatively large number of stem cell marker-positive cells as an adult stem cell source. In this review, we introduce a model theory of why so many AE cells possess stem cell characteristics. We also describe previous work concerning the therapeutic applications and discuss the pluripotency of the AE cells and potential pitfalls for amnion-derived stem cell research.

2011-01-01

309

Leaf Photosynthesis Under Drought Stress  

Microsoft Academic Search

The photosynthetic apparatus is resistant to drought. Net CO2 uptake of a leaf submitted to a mild desiccation decreases because of stomatal closure. As aresult, CO2 concentration in the chloroplast decreases in plants exposed to water shortage. This drop in the chloroplast CO2 concentration causes: (i) a decrease in photochemical yield of open PS II centers and, consequently, an increase

Gabriel Cornic; Angelo Massacci

310

CORN LEAF CHLOROPHYLL STATUS FROM HYPERSPECTRAL IMAGES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Leaf chlorophyll concentration is an indicator of plant N status. Subtle differences in canopy reflectance due to changes in leaf chlorophyll concentration are often overwhelmed by the large changes in reflectance associated with soil brightness and leaf area index (LAI). Our objective was to devel...

311

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...2 2010-01-01 2010-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture ...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its...

2010-01-01

312

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...2 2009-01-01 2009-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture ...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its...

2009-01-01

313

Leaf litter decomposition in three Adirondack lakes  

Microsoft Academic Search

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,

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

1983-01-01

314

Malate Dehydrogenases in the Rusted Bean Leaf.  

PubMed

Rust growth in the bean leaf was accompanied by the appearance of one new malate dehydrogenase isozyme and continuation of one otherwise lost during the development of the healthy leaf. The new isozyme was contributed by the fungus, the other by the leaf. Both enzymes were cytoplasmic proteins. Rusting caused the loss of a mitochondrial isozyme. PMID:17802172

Staples, R C; Stahmann, M A

1963-06-21

315

The Arabidopsis PHYTOCHROME KINASE SUBSTRATE2 Protein Is a Phototropin Signaling Element That Regulates Leaf Flattening and Leaf Positioning1[W][OA  

PubMed Central

In Arabidopsis (Arabidopsis thaliana), the blue light photoreceptor phototropins (phot1 and phot2) fine-tune the photosynthetic status of the plant by controlling several important adaptive processes in response to environmental light variations. These processes include stem and petiole phototropism (leaf positioning), leaf flattening, stomatal opening, and chloroplast movements. The PHYTOCHROME KINASE SUBSTRATE (PKS) protein family comprises four members in Arabidopsis (PKS1–PKS4). PKS1 is a novel phot1 signaling element during phototropism, as it interacts with phot1 and the important signaling element NONPHOTOTROPIC HYPOCOTYL3 (NPH3) and is required for normal phot1-mediated phototropism. In this study, we have analyzed more globally the role of three PKS members (PKS1, PKS2, and PKS4). Systematic analysis of mutants reveals that PKS2 (and to a lesser extent PKS1) act in the same subset of phototropin-controlled responses as NPH3, namely leaf flattening and positioning. PKS1, PKS2, and NPH3 coimmunoprecipitate with both phot1-green fluorescent protein and phot2-green fluorescent protein in leaf extracts. Genetic experiments position PKS2 within phot1 and phot2 pathways controlling leaf positioning and leaf flattening, respectively. NPH3 can act in both phot1 and phot2 pathways, and synergistic interactions observed between pks2 and nph3 mutants suggest complementary roles of PKS2 and NPH3 during phototropin signaling. Finally, several observations further suggest that PKS2 may regulate leaf flattening and positioning by controlling auxin homeostasis. Together with previous findings, our results indicate that the PKS proteins represent an important family of phototropin signaling proteins.

de Carbonnel, Matthieu; Davis, Phillip; Roelfsema, M. Rob G.; Inoue, Shin-ichiro; Schepens, Isabelle; Lariguet, Patricia; Geisler, Markus; Shimazaki, Ken-ichiro; Hangarter, Roger; Fankhauser, Christian

2010-01-01

316

Single leaf area estimation models based on leaf weight of eucalyptus in southern China  

Microsoft Academic Search

Leaf area is an important parameter for modeling tree growth and physiological processes of trees. The single young and mature\\u000a leaf area estimation models of eucalyptus were developed based on leaf fresh weight. In total, leaf area and leaf weight were\\u000a measured from 455 fresh leaves of 25 trees of eucalyptus in southern China. The majority of the data (80%)

Jun Diao; Xiang-dong Lei; Ling-xia Hong; Jian-tao Rong; Qiang Shi

2010-01-01

317

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

318

Algorithm for retrieving vegetative canopy and leaf parameters from multi- and hyperspectral imagery  

NASA Astrophysics Data System (ADS)

In recent years hyper-spectral data has been used to retrieve information about vegetative canopies such as leaf area index and canopy water content. For the environmental scientist these two parameters are valuable, but there is potentially more information to be gained as high spatial resolution data becomes available. We developed an Amoeba (Nelder-Mead or Simplex) based program to invert a vegetative canopy radiosity model coupled with a leaf (PROSPECT5) reflectance model and modeled for the background reflectance (e.g. soil, water, leaf litter) to a measured reflectance spectrum. The PROSPECT5 leaf model has five parameters: leaf structure parameter Nstru, chlorophyll a+b concentration Cab, carotenoids content Car, equivalent water thickness Cw and dry matter content Cm. The canopy model has two parameters: total leaf area index (LAI) and number of layers. The background reflectance model is either a single reflectance spectrum from a spectral library() derived from a bare area pixel on an image or a linear mixture of soil spectra. We summarize the radiosity model of a layered canopy and give references to the leaf/needle models. The method is then tested on simulated and measured data. We investigate the uniqueness, limitations and accuracy of the retrieved parameters on canopy parameters (low, medium and high leaf area index) spectral resolution (32 to 211 band hyperspectral), sensor noise and initial conditions.

Borel, Christoph

2009-05-01

319

Shoot biomass growth is related to the vertical leaf nitrogen gradient in Salix canopies.  

PubMed

Plant canopy optimization models predict that leaf nitrogen (N) distribution in the canopy will parallel the vertical light gradient, and numerous studies with many species have confirmed this prediction. Further, it is predicted that for a given canopy leaf area, a low vertical light extinction coefficient will promote rapid growth. Therefore, the ideal canopy of fast-growing plants should combine high leaf area index with a low light extinction coefficient; the latter being reflected in a flat vertical leaf N gradient throughout the canopy. Based on data from an experimental Salix stand (six varieties) grown on agricultural land in central Sweden, we tested the hypothesis that shoot growth is correlated with vertical leaf N gradient in canopies of hybrid willows bred for biomass production, which could have implications for Salix breeding. Tree improvement research requires screening of growth-related traits in large numbers of plants, but assessment of canopy leaf N gradients by chemical analysis is expensive, time-consuming and destructive. An alternative to analytical methods is to estimate leaf N gradients nondestructively with an optical chlorophyll meter (SPAD method). Here we provide a specific calibration for interpreting SPAD data measured in hybrid willows grown in biomass plantations on fertile agricultural land. Based on SPAD measurements, a significant and inverse relationship (r(2) = 0.88) was found between shoot biomass growth and vertical leaf N gradient across canopies of six Salix varieties. PMID:17669744

Weih, Martin; Rönnberg-Wästjung, Ann-Christin

2007-11-01

320

Water Deficit and Spatial Pattern of Leaf Development. Variability in Responses Can Be Simulated Using a Simple Model of Leaf Development1  

PubMed Central

We analyzed the effect of short-term water deficits at different periods of sunflower (Helianthus annuus L.) leaf development on the spatial and temporal patterns of tissue expansion and epidermal cell division. Six water-deficit periods were imposed with similar and constant values of soil water content, predawn leaf water potential and [ABA] in the xylem sap, and with negligible reduction of the rate of photosynthesis. Water deficit did not affect the duration of expansion and division. Regardless of their timing, deficits reduced relative expansion rate by 36% and relative cell division rate by 39% (cells blocked at the G0-G1 phase) in all positions within the leaf. However, reductions in final leaf area and cell number in a given zone of the leaf largely differed with the timing of deficit, with a maximum effect for earliest deficits. Individual cell area was only affected during the periods when division slowed down. These behaviors could be simulated in all leaf zones and for all timings by assuming that water deficit affects relative cell division rate and relative expansion rate independently, and that leaf development in each zone follows a stable three-phase pattern in which duration of each phase is stable if expressed in thermal time (C. Granier and F. Tardieu [1998b] Plant Cell Environ 21: 695–703).

Granier, Christine; Tardieu, Francois

1999-01-01

321

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

322

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

323

The dosimetric impact of leaf interdigitation and leaf width on VMAT treatment planning in Pinnacle: comparing Pareto fronts  

Microsoft Academic Search

To evaluate in an objective way the effect of leaf interdigitation and leaf width on volumetric modulated arc therapy plans in Pinnacle. Three multileaf collimators (MLCs) were modeled: two 10 mm leaf width MLCs, with and without interdigitating leafs, and a 5 mm leaf width MLC with interdigitating leafs. Three rectum patients and three prostate patients were used for the

Z van Kesteren; T M Janssen; E Damen; C van Vliet-Vroegindeweij

2012-01-01

324

Purification of potato leaf roll virus and an evaluation of methods for its diagnosis  

Microsoft Academic Search

To evaluate four diagnostic methods for potato leaf roll virus (PLRV), an antiserum was prepared against a virus preparation\\u000a purified from infectedDatura stramonium L. by an exudation method. The antiserum had a titer of 1:64 in microprecipitin tests. In a procedure developed subsequently\\u000a PLRV was purified by a method that involved grinding liquid nitrogen frozen stems, petioles, and veins from

R. F. Hepp; G. A. de Zoeten

1978-01-01

325

Cardiac Stem and Progenitor Cells  

Microsoft Academic Search

\\u000a Since the early days of cardiovascular biology, it has been believed that mammalian adult cardiomyocytes exit from the cell\\u000a cycle soon after birth, with the total number of cardiomyocytes being pre-determined. Recently, the identification of resident\\u000a cardiac stem\\/progenitor cells by several independent laboratories has challenged this long-held paradigm and has provoked\\u000a an exponential increase in the number of investigations. As

Ronglih Liao; Regina L. Sohn

326

Regulation of asymmetric stem cell division: spindle orientation and the centrosome  

PubMed Central

Asymmetric stem cell division, as a means of maintaining adequate numbers of stem cells, has attracted widespread attention from researchers in the stem cell biology field. Yet, the molecular and cellular mechanisms that govern asymmetric stem cell division remain poorly understood. Stem cells are not the only cell population that divides asymmetrically, and fortunately, great progress has been made in the understanding of asymmetric cell division during development, providing insight into strategies that stem cells may employ to divide asymmetrically. This review will summarize the importance of stem cell function and the role of asymmetric division in controlling stem cell behavior.

Yamashita, Yukiko M.

2010-01-01

327

The inherent variability of water stress indicators in apple, nectarine and pear orchards, and the validity of a leaf-selection procedure for water potential measurements  

Microsoft Academic Search

The following two topics were examined: (1) The variability in the measurement of leaf water potential (LWP), stem water potential\\u000a (SWP), maximum daily trunk shrinkage (MDS), and soil water tension (SWT) in apple, nectarine and pear orchards; and (2) The\\u000a validity of a leaf-selection procedure for SWP measurements in commercial apple orchards. 27 trees were selected in an apple\\u000a orchard,

Amos Naor; Yoni Gal; Moti Peres

2006-01-01

328

A Fast Scheme for Mapping Leaf Chlorophyll and Leaf Area Index Using Inverse Canopy Reflectance Modeling and SPOT Reflectance Data  

NASA Astrophysics Data System (ADS)

Reflectance data in the green, red and near-infrared wavelength region were acquired by the SPOT high resolution visible and geometric imaging instruments for an agricultural area in Denmark for the purpose of estimating leaf chlorophyll content (Cab) and green leaf area index (LAI). SPOT reflectance observations were atmospherically corrected using aerosol data from MODIS and profiles of air temperature, humidity and ozone from the Atmospheric Infrared Sounder (AIRS), and used as input for the inversion of a two-layer homogeneous canopy reflectance model. Since inversions are computationally slow, land cover and site specific inverse modeling was applied to a restricted number of pixels to build multiple species- and site dependent formulations relating the two biophysical properties of interest to vegetation indices (VI) or single spectral band reflectances. Subsequently, the established relationships were employed for a computationally efficient pixel- wise mapping of Cab and LAI for the entire region. The inversion scheme assumes prior knowledge of mean leaf inclination angle and specific dry matter content but solves implicitly for soil/background reflectance, leaf mesophyll structure, Cab and LAI. Significant correlations were observed between inverse estimates of Cab and green reflectance when the relationships were established independently for each land cover class, whereas the high canopy penetration ability of the near-infrared reflectance effectuated robust near-linear relationships with LAI for intermediate to high leaf biomass. Due to a successful correction for background influences, LAI-NDVI relationships were employed efficiently for sparse vegetation covers. Cab estimated using the generated green reflectance relationships was correlated with in-situ SPAD-502 measurements for barley, wheat and maize fields (r2 = 0.76). A comparison of calibrated SPAD values and Cab estimates yielded an overall root mean square deviation of 6.5 ?g cm-2. The results of this study support the use of satellite measurements of green reflectance data for quantifying leaf chlorophyll concentrations in time and space.

Houborg, R.; Boegh, E.; Schelde, K.; Thomsen, A.

2006-12-01

329

Leaf hairs influence phytopathogenic fungus infection and confer an increased resistance when expressing a Trichoderma  -1,3-glucanase  

Microsoft Academic Search

The leaf surface of a very large number of plant species are covered by trichomes. Non-glandular trichomes are specialized unicellular or multicellular structures that occur in many different plant species and function in xenobiotic detoxification and protecting the plant against pest attack. By analysing the susceptibility of trichome mutants, evidence is provided that indicates the influence of leaf trichomes on

Leticia Calo; Irene Garcia; Cecilia Gotor; Luis C. Romero

2006-01-01

330

Visual assessment of seasonal changes in amount of mycelium of Acremonium loliae in leaf sheaths of perennial ryegrass  

Microsoft Academic Search

Counts were made of hyphae of the endophyte Acremonium loliae Latch, Christensen & Samuels in leaf sheaths of perennial ryegrass (Lolium perenne L.) cv. Ellett. Material was collected from grazed plots at 4 North Island sites during a 2-year period. Numbers of hyphae\\/mm breadth of leaf sheath varied by over tenfold in infected tillers collected from the same site at

M. E. di Menna; J. E. Waller

1986-01-01

331

Banking on Immortality? Exploring the Stem Cell Supply Chain from Embryo to Therapeutic Application  

Microsoft Academic Search

This article addresses a number of difficult and controversial issues surrounding the development of stem cell lines from embryonic stem cells derived from unused embryos during IVF treatment. The UK has recently established the world’s first Stem Cell Bank to be a repository for stem cell lines from the UK and elsewhere, and to make them available for use by

Peter Glasner

2005-01-01

332

Stem cells and the Planarian Schmidtea mediterranea  

PubMed Central

In recent years, somatic 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 limitation in the study of somatic stem cells lies in the difficulty of accessing and studying these cells in vivo. This barrier is further compounded by the limitations of in vitro culture systems, which are unable to emulate the microenvironments in which stem cells reside and which are known to provide critical regulatory signals for their proliferation and differentiation. Given the complexity of vertebrate adult somatic stem cell populations and their relative inaccessibility to in vivo molecular analyses, the study of somatic stem cells should benefit from analyzing their counterparts in simpler model organisms. In the past, the use of Drosophila or C. elegans has provided invaluable contributions to our understanding of genes and pathways involved in a variety of human diseases. However, stem cells in these organisms are mostly restricted to the gonads, and more importantly neither Drosophila, nor C. elegans are capable of regenerating body parts lost to injury. Therefore, a simple animal with experimentally accessible stem cells playing a role in tissue maintenance and/or regeneration should be very useful in identifying and functionally testing the mechanisms regulating stem cell activities. The planarian Schmidtea mediterranea is poised to fill this experimental gap. S. mediterranea displays robust regenerative properties driven by an adult, somatic stem cell population capable of producing the ?40 different cell types found in this organism, including the germ cells. Given that all known metazoans depend on stem cells for their survival, it is extremely likely that the molecular events regulating stem cell biology would have been conserved throughout evolution, and that the knowledge derived from studying planarian stem cells could be vertically integrated to the study of vertebrate somatic stem cells. Current efforts, therefore, are aimed at further characterizing the somatic population of planarian stem cells in order to define its suitability as a model system in which to mechanistically dissect the basic biological attributes of metazoans stem cells.

Sanchez Alvarado, Alejandro

2007-01-01

333

Trafficking of stem cells.  

PubMed

Stem cells undergo regulated trafficking from the developmental stages to the adulthood. Stem cell migration is critical to organize developing organs and likely contributes postnatally to tissue regeneration. Here, we review the molecular mechanisms underlying migration of hematopoietic stem cells, neural stem cells, and primordial germ cells, revealing common operative pathways. PMID:21618080

Magnon, Claire; Lucas, Daniel; Frenette, Paul S

2011-01-01

334

Stem Cells and Cancer  

Microsoft Academic Search

Proteins from the Polycomb group (PcG) are epigenetic chromatin modifiers involved in cancer development and also in the maintenance of embryonic and adult stem cells. The therapeutic potential of stem cells and the growing conviction that tumors contain stem cells highlights the importance of understanding the extrinsic and intrinsic circuitry controlling stem cell fate and their connections to cancer.

Merel E. Valk-Lingbeek; Sophia W. M. Bruggeman; Maarten van Lohuizen

2004-01-01

335

Toward ‘SMART’ stem cells  

Microsoft Academic Search

Stem cell research is at the heart of regenerative medicine, which holds great promise for the treatment of many devastating disorders. However, in addition to hurdles posed by well-publicized ethical issues, this emerging field presents many biological challenges. What is a stem cell? How are embryonic stem cells different from adult stem cells? What are the physiological bases for therapeutically

T Cheng

2008-01-01

336

Temporal Isotopic Variations of Leaf Water in Pine Needles  

NASA Astrophysics Data System (ADS)

Understanding the isotopic variations in a plant's leaf water is important for a number of climatological and biogeochemical studies. Leaf water isotopic composition is affected by the isotopic composition of the source water and the relative humidity of the air, both of which are related to climate. This dependency is the basis for climate reconstruction using isotopic compositions of tree-ring cellulose. The isotopic composition of leaf water is also important for the assessment of terrestrial biological productivity and the quantification of the Dole effect. We have studied the oxygen and hydrogen isotopic variations in leaf water of biennial needles from red pine (Pinus resinosa) and white pine (Pinus strobes) in Hanover, New Hampshire, USA. We have examined the leaf water ?D and ?18O values along pine needles from base to tip, and the isotopic differences between young and old leaves. Within a needle, progressive enrichments of both oxygen-18 and deuterium were observed toward the tip, ranging for ?D from -60.1 to 9.4 permil in white pine and -67.1 to -34.9 permil in red pine, and for ?18O from -3.1 to 19.1 for white pine and -7.3 to 5.5 permil in red pine. For both species, ?D and ?18O were higher in old leaves than in young leaves. The isotopic difference between old and young leaves was most pronounced earlier in the growing season; the gap narrowed with time and finally disappeared in early fall. Early in the growing season, the ?D values of young needles were -21 and -30 permil in white and red pine, respectively, and that of old needles were -3.0 and -8.0 permil, respectively. The ?18O values showed similar trends, and the ?D vs. ?18O slope for the young leaves decreased from 3.6 in spring to ~1 in early autumn. Our observations can be simulated using the progressive isotopic enrichment model proposed by Barnes and Farquhar for monocotyledoneous leaves. Two variables, the transpiration rate and length of the needle, can explain the observed isotopic variations. These two variables can be combined into one parameter in the model as the longitudinal Peclet number of the leaf. In addition, the model can also explain the change in the slope of the ?D vs. ?18O relationship in leaf water.

Shu, Y.; Feng, X.; Faiia, A. M.

2005-05-01

337

In vitro shoot regeneration from leaf explants of Roman Chamomile  

Microsoft Academic Search

Murashige and Skoog (1962) medium supplemented with 1.0 to 4.5 µM of BA and 1.0 µM of NAA induced adventitious bud formation and shoot development in leaf explants of Roman Chamomile. A higher number of adventitious buds was observed at the proximal end of the explants. Plantlets were replicated and multiplied on MS medium supplemented with 2.25 µM of BA

S. Echeverrigaray; F. Fracaro; L. B. Andrade; S. Biasio; L. Atti-Serafini

2000-01-01

338

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

PubMed Central

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 Fv/Fm 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.

Ghanem, Michel Edmond; Albacete, Alfonso; Martinez-Andujar, Cristina; Acosta, Manuel; Romero-Aranda, Remedios; Dodd, Ian C.; Lutts, Stanley; Perez-Alfocea, Francisco

2008-01-01

339

Partitioning of nitrate assimilation among leaves, stems and roots of poplar.  

PubMed

Plants differ in tissue localization of nitrate reduction and assimilation. Some species reduce nitrate primarily in the leaves, whereas other species localize nitrate reduction and assimilation in the roots. We determined how nitrate assimilation is partitioned among leaves, stems and roots of poplar (Populus tremula L. x P. alba L.) by comparing tissue differences in in vivo nitrate reductase activity (NRA), nitrate reductase abundance and tissue nitrate concentration. Compared with stems or roots, NRA was greater in leaves, and the highest leaf NRA was found in young leaves. Leaf and root NRA increased with increasing nitrate supply, whereas stem NRA remained constant. Leaf NRA was at least 10-fold greater than root NRA at all external nitrate concentrations. Nitrate reductase abundance increased in all tissues with increasing nitrate availability, and nitrate reductase abundance was at least 10-fold greater in leaves than in stems or roots at all nitrate availabilities. Tissue nitrate concentration increased with increasing nitrate supply and was greater in roots than in stems and leaves. Photoperiod influenced NRA, with leaf NRA declining in nitrate-fertilized plants with short daily photoperiods (8-h). We conclude that different tissues of poplar vary in nitrate assimilation with little nitrate assimilation occurring in roots and the most nitrate assimilation taking place in leaves. PMID:12091153

Black, Brent L; Fuchigami, Leslie H; Coleman, Gary D

2002-07-01

340

Brain tumor stem cells  

Microsoft Academic Search

The concept of brain tumor stem cells is gaining increased recognition in neuro-oncology. Until recently, the paradigm of\\u000a a tumor-initiating stem cell was confined to hematopoietic malignancies where the hierarchical lineages of stem progenitor\\u000a cells are well established. The demonstration of persistent stem cells and cycling progenitors in the adult brain, coupled\\u000a with the expansion of the cancer stem cell

Georgia Panagiotakos; Viviane Tabar

2007-01-01

341

Potential Use of Stem Cells for Kidney Regeneration  

PubMed Central

Significant advances have been made in stem cell research over the past decade. A number of nonhematopoietic sources of stem cells (or progenitor cells) have been identified, including endothelial stem cells and neural stem cells. These discoveries have been a major step toward the use of stem cells for potential clinical applications of organ regeneration. Accordingly, kidney regeneration is currently gaining considerable attention to replace kidney dialysis as the ultimate therapeutic strategy for renal failure. However, due to anatomic complications, the kidney is believed to be the hardest organ to regenerate; it is virtually impossible to imagine such a complicated organ being completely rebuilt from pluripotent stem cells by gene or chemical manipulation. Nevertheless, several groups are taking on this big challenge. In this manuscript, current advances in renal stem cell research are reviewed and their usefulness for kidney regeneration discussed. We also reviewed the current knowledge of the emerging field of renal stem cell biology.

Yokoo, Takashi; Matsumoto, Kei; Yokote, Shinya

2011-01-01

342

Leaf orientation and distribution in a Phaseolus vulgaris L. crop and their relation to light microclimate  

NASA Astrophysics Data System (ADS)

Changes in canopy structure parameters (leaflet orientation, leaflet inclination and leaf area index) were measured in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. These changes were compared with the corresponding changes in seasonal light transmission. The beans showed clear heliotropic behaviour, with preferential orientation of leaflets towards the sun's beam, especially on sunny days. Nevertheless a significant proportion of the leaves pointed in other directions, with as much as 20% oriented towards the north. The highest proportion of leaf inclinations was in the range 30-40° on cloudy days and between 40° and 50° on sunny days. Two methods were compared for assessing changes in light transmission: (a) the use of a Sunfleck Ceptometer and (b) the use of continuous records obtained with sensors installed in the canopy. Over the growth period studied, the total of the leaf plus stem area indices (LS) increased from 0.26 to 5.2 with the transmission coefficient (?) for photosynthetic photon flux density (PPFD), obtained using the Ceptometer, correspondingly decreasing from 0.72 to 0.05, and the canopy extinction coefficient decreasing from 1.4 to 0.62. The continuous records of light transmission gave generally similar estimates of ?. Some contrasting leaf angle distribution functions were compared for estimation of LS from the light measurements. The best leaf angle function to predict LS from the observed light transmission was a conical function corrected by the degree of heliotropism.

Barradas, V. L.; Jones, H. G.; Clark, Jerry A.

343

Leaf respiratory acclimation to climate: comparisons among boreal and temperate tree species along a latitudinal transect.  

PubMed

In common gardens along an ?900 km latitudinal transect through Wisconsin and Illinois, U.S.A., tree species typical of boreal and temperate forests were compared with respect to the nature and magnitude of leaf respiratory acclimation to contrasting climates. The boreal representatives were trembling aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh.), while the temperate species were eastern cottonwood (Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum (Liquidambar styraciflua L.). Assessments were conducted on seedlings grown from seed sources collected near southern and northern range boundaries, respectively. Nighttime rates of leaf dark respiration (R(d)) at common temperatures, as well as R(d)'s short-term temperature sensitivity (energy of activation, E(o)), were assessed for all species and gardens twice during a growing season. Little evidence of R(d) thermal acclimation was observed, despite a 12 °C range in average air temperature across gardens. Instead, R(d) variation at warm temperatures was linked most closely with prior leaf photosynthetic performance, while R(d) variation at cooler temperatures was most strongly related to leaf nitrogen concentration. Moreover, E(o) differences across species and gardens appeared to stem from the somewhat independent limitations on warm versus cool R(d). Based on this construct, an empirical model relying on R(d) estimates from leaf photosynthesis and nitrogen concentration explained 55% of the observed E(o) variation. PMID:21990024

Dillaway, Dylan N; Kruger, Eric L

2011-10-01

344

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

2013-06-21

345

Antiinflammatory and analgesic effects of Psidium guajava Linn. (Myrtaceae) leaf aqueous extract in rats and mice.  

PubMed

In many parts of Africa, the leaf, stem-bark, and roots of Psidium guajava Linn. (Family: Myrtaceae) are used traditionally for the management, control, and/or treatment of an array of human disorders. In an effort to scientifically appraise some of the ethnomedical properties of P. guajava leaf, and probe its efficacy and safety, the present study was undertaken to examine the antiinflammatory and analgesic properties of the plant's leaf aqueous extract in some experimental animal paradigms. The antiinflammatory property of the aqueous leaf extract was investigated in rats, using fresh egg albumin-induced pedal (paw) edema, while the analgesic effect of the plant extract was evaluated by the "hot-plate" and "acetic acid" test models of pain in mice. Diclofenac (100 mg/kg, i.p.) and morphine (10 mg/kg, i.p.) were used respectively as standard, reference antiinflammatory and analgesic agents for comparison. P. guajava leaf aqueous extract (PGE, 50-800 mg/kg, i.p.) produced dose-dependent and significant (p < 0.05-0.001) inhibition of fresh egg albumin-induced acute inflammation (edema) in rats. The plant extract (PGE, 50-800 mg/kg, i.p.) also produced dose-dependent and significant (p < 0.05-0.001) analgesic effects against thermally and chemically induced nociceptive pain in mice. The numerous tannins, polyphenolic compounds, flavonoids, ellagic acid, triterpenoids, guiajaverin, quercetin, and other chemical compounds present in the plant are speculated to account for the observed antiinflammatory and analgesic effects of the plant's leaf extract. In summary, the findings of this experimental animal study indicate that the leaf aqueous extract of P. guajava possesses analgesic and antiinflammatory properties, and thus lend pharmacological credence to the suggested ethnomedical, folkloric uses of the plant in the management and/or control of painful, arthritic and other inflammatory conditions in some rural communities of Africa. PMID:17003849

Ojewole, J A O

2006-09-01

346

STEm Minority Graduate Program  

SciTech Connect

ABSTRACT The state of science, technology, engineering and math (STEM) education in the United States has seen some unfavorable assessments over the past decade. In early February, 2010 the House of Representatives heard testimony on undergraduate and graduate education. The message from the panel, which included experts from academia, STEM-based industries, and the National Science Foundation (NSF) was dire and required an urgent response. The experts along with the committee���¢��������s chairperson, U. S. Representative Daniel Lipinski (D-IL) cited that the complexity of Science, Technology, Engineering, and Mathematics applications and coursework and the methodology utilized to teach these subjects are forcing students out of these disciplines. As the National Academies described in its 2007 report Rising Above the Gathering Storm, successful STEM education is not just an academic pursuit���¢��������it���¢��������s a necessity for competing in the knowledge-based economy that the United States had a key role in creating. The potential for action is being made available again as the America COMPETES Act of 2007 is up for reauthorization. Its initial focus was on STEM education at the K-12 levels, but efforts at the undergraduate and graduate levels are needed to retain students to fill the jobs left vacant as baby boomers retire. The Educational Advancement Alliance, Inc. (EAA) has for two decades created programs that have not only addressed the issues of ensuring that students are aptly prepared for college but have focused its efforts over the past decade on increasing the number of students who pursue degrees in STEM disciplines. For the EAA, the introduction of the wonders of science begins at the elementary and middle school level via the Learning Lab, a state-of-the-art mobile science laboratory that visits students in grades 4-6 at the various schools throughout Philadelphia and The Math/Tech Academy which meets on Saturdays for students in grades 5-7. For the past two years the EAA has assisted college graduates in their quest to attain advanced degrees in STEM by providing fellowships. The EAA continued this effort by recruiting and providing fellowships to students who aspired to continue their education at the graduate level. The fellowships provided funding for tuition, fees, books, technology, and stipends to assist with room, board, and living expenses during the academic year and salary, transportation, and living expenses to those students who secured internships with the Department of Energy. Additionally the EAA designed and implemented needed support systems to ensure successful completion of the Masters degree programs, including but not limited to membership in professional associations, attendance at industry and academic conferences, and professional development workshops, and tutorial assistance if needed. This program assisted over 80 students directly and society-at-large by helping to educate and develop future physicists, engineers, biostatisticians, and researchers who will have the necessary skillsets to fill the increasing numbers of positions that require such expertise.

Kaen E. Nicholas

2012-09-20

347

How close are we to targeting the leukemia stem cell?  

PubMed

There are a number of approaches for selective targeting of leukemic stem cells (LSCs). These include targeting stem-cell properties, such as self-renewal, inducing cycling of quiescent LSCs to sensitize them to conventional agents, employing or inducing immune-based mechanisms, and targeting tumor-specific physiology. Agents such as parthenolide inhibit the ability of leukemic stem cells to respond to oxidative stress and make leukemic stem cells and bulk leukemic cells susceptible to cell death, while normal stem cells remain relatively unharmed by these agents. The major mechanism of action of these small molecules appears to revolve around the aberrant glutathione metabolism pathway found in leukemic cells. PMID:23200537

Pei, Shanshan; Jordan, Craig T

2012-10-23

348

7 CFR 28.466 - Leaf Grade 6.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Leaf Grade 6. 28.466 Section 28.466 Agriculture Regulations of the Department of Agriculture...for the Leaf Grade of American Upland Cotton § 28.466 Leaf Grade 6. Leaf Grade 6 is leaf which is...

2013-01-01

349

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...firm leaf structure, medium body, rich in oil...10 percent. B3LâGood Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong...firm leaf structure, medium body, stringy. Uniformity...percent waste. B3SâGood Quality Slick Leaf...

2013-01-01

350

7 CFR 29.3647 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...Medium-brown Heavy Leaf. Ripe, medium body, open leaf structure...injury tolerance. B3F Good Quality Medium-brown Heavy Leaf. Mature...injury tolerance. B3M Good Quality Mixed Heavy Leaf. Mature, medium body, firm leaf...

2013-01-01

351

Genomic instability in induced stem cells.  

PubMed

The ability to reprogram adult cells into stem cells has raised hopes for novel therapies for many human diseases. Typical stem cell reprogramming protocols involve expression of a small number of genes in differentiated somatic cells with the c-Myc and Klf4 proto-oncogenes typically included in this mix. We have previously shown that expression of oncogenes leads to DNA replication stress and genomic instability, explaining the high frequency of p53 mutations in human cancers. Consequently, we wondered whether stem cell reprogramming also leads to genomic instability. To test this hypothesis, we examined stem cells induced by a variety of protocols. The first protocol, developed specifically for this study, reprogrammed primary mouse mammary cells into mammary stem cells by expressing c-Myc. Two other previously established protocols reprogrammed mouse embryo fibroblasts into induced pluripotent stem cells by expressing either three genes, Oct4, Sox2 and Klf4, or four genes, OSK plus c-Myc. Comparative genomic hybridization analysis of stem cells derived by these protocols revealed the presence of genomic deletions and amplifications, whose signature was suggestive of oncogene-induced DNA replication stress. The genomic aberrations were to a significant degree dependent on c-Myc expression and their presence could explain why p53 inactivation facilitates stem cell reprogramming. PMID:21311564

Pasi, C E; Dereli-Öz, A; Negrini, S; Friedli, M; Fragola, G; Lombardo, A; Van Houwe, G; Naldini, L; Casola, S; Testa, G; Trono, D; Pelicci, P G; Halazonetis, T D

2011-02-11

352

Patenting human genes and stem cells.  

PubMed

Cell lines and genetically modified single cell organisms have been considered patentable subjects for the last two decades. However, despite the technical patentability of genes and stem cell lines, social and legal controversy concerning their 'ownership' has surrounded stem cell research in recent years. Some granted patents on stem cells with extremely broad claims are casting a shadow over the commercialization of these cells as therapeutics. However, in spite of those early patents, the number of patent applications related to stem cells is growing exponentially. Both embryonic and adult stem cells have the ability to differentiate into several cell lineages in an organism as a result of specific genetic programs that direct their commitment and cell fate. Genes that control the pluripotency of stem cells have been recently identified and the genetic manipulation of these cells is becoming more efficient with the advance of new technologies. This review summarizes some of the recent published patents on pluripotency genes, gene transfer into stem cells and genetic reprogramming and takes the hematopoietic and embryonic stem cell as model systems. PMID:19075916

Martin-Rendon, Enca; Blake, Derek J

2007-01-01

353

Hemopoietic stem cells: sources and applications.  

PubMed

Classically hemopoietic stem cells to be used for transplantation or autologous reinfusion have been harvested from the bone marrow which has remained the major source of stem cells for allogeneic transplantation. However, pluripotent stem cells also circulate in peripheral blood under physiological conditions and can be "mobilized" to appear in very large numbers in peripheral blood by treatment with cytotoxic chemotherapy, hemopoietic growth factors, or both. These cells are now being used widely for autologous stem cell support. They have the advantage of very rapid hemopoietic reconstitution, thereby shortening the posttransplant period of pancytopenia. Fetal liver cells, another classic source of stem cells, are currently used only infrequently. However, there is a growing interest in the use of umbilical cord blood which is rich in stem cells and easily accessible. Cord blood stem cells have been used successfully for pediatric transplants even across major histocompatibility barriers. Technology has been developed which may permit sufficient in vitro expansion so that these cells can also be used for transplants in adults. Furthermore, there is evidence that these cells may be preferable to marrow or even mobilised peripheral blood stem cells for the purpose of gene transfer. PMID:7850265

Hong, D S; Deeg, H J

1994-01-01

354

Apical correlative effects in leaf epinasty of tomato.  

PubMed

The influence of the stem apex on leaf curvature was investigated using debudded tomato (Lycopersicon esculentum Mill. cv Anahu) plants and petiole explants, consisting of a section of petiole attached to a section of stem.Decapitation of the main shoot of tomato plants induced hyponasty of petioles in young leaves. Application of auxin in place of the removed apex or fumigation of intact tomato plants with ethylene produced epinastic curvature at the base of the petiole. Simultaneous carbon dioxide treatments prevented the development of petiolar epinasty due to auxin and ethylene treatments. Application of ethylene gas to the decapitated shoot or injection into the stem, induced petiolar epinasty. In a saturating level of ethylene gas, tomato petioles did not respond to indole-3-acetic acid applied to the cut apex. Auxin-induced ethylene production in petiole explants preceded the development of epinasty. Application of indoleacetic acid in lanolin to the entire lower side of the petioles of leaves in situ produced petiole epinasty. Petiolar epinasty due to apically applied indoleacetic acid resulted from differential cell elongation.The auxins indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid, and naphthalene-1-acetic acid induced epinasty when applied apically to decapitated tomato plants, while gibberellic acid, kinetin, abscisic acid, and auxin or gibberellin antagonists had no effect. When such compounds were applied to petiole explants, only indole-3-acetic acid and kinetin caused an increase in ethylene production and the effect of kinetin was relatively weak.Application of 2,3,5-triiodobenzoic acid around the stem did not change the effect on petiolar epinasty of auxin applied to the decapitated shoot or around the stem. Radioautography showed that the label from (14)C-indoleacetic acid applied apically entered the petiole and midrib tissue; however, extraction showed that only a fraction of the label in these tissues was in the form of indoleacetic acid.Removal of leaflets from leaves induced hyponasty in the midrib region, and application of auxin to the leaflet stubs produced midrib epinasty; carbon dioxide did not block the action of auxin in this type of epinasty. Removal of leaflets from leaves did not alter the effect of apically applied auxin on petiolar epinasty.The data are consistent with the hypothesis that the oblique orientation of leaves in tomato plants is influenced by two epinastic responses. Petiolar epinasty is controlled by the apical region on the stem and is due to the action of auxin-induced ethylene; and midrib epinasty is due to an action of auxin other than through ethylene. PMID:16658919

Kazemi, S; Kefford, N P

1974-10-01

355

Apical Correlative Effects in Leaf Epinasty of Tomato 1  

PubMed Central

The influence of the stem apex on leaf curvature was investigated using debudded tomato (Lycopersicon esculentum Mill. cv Anahu) plants and petiole explants, consisting of a section of petiole attached to a section of stem. Decapitation of the main shoot of tomato plants induced hyponasty of petioles in young leaves. Application of auxin in place of the removed apex or fumigation of intact tomato plants with ethylene produced epinastic curvature at the base of the petiole. Simultaneous carbon dioxide treatments prevented the development of petiolar epinasty due to auxin and ethylene treatments. Application of ethylene gas to the decapitated shoot or injection into the stem, induced petiolar epinasty. In a saturating level of ethylene gas, tomato petioles did not respond to indole-3-acetic acid applied to the cut apex. Auxin-induced ethylene production in petiole explants preceded the development of epinasty. Application of indoleacetic acid in lanolin to the entire lower side of the petioles of leaves in situ produced petiole epinasty. Petiolar epinasty due to apically applied indoleacetic acid resulted from differential cell elongation. The auxins indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid, and naphthalene-1-acetic acid induced epinasty when applied apically to decapitated tomato plants, while gibberellic acid, kinetin, abscisic acid, and auxin or gibberellin antagonists had no effect. When such compounds were applied to petiole explants, only indole-3-acetic acid and kinetin caused an increase in ethylene production and the effect of kinetin was relatively weak. Application of 2,3,5-triiodobenzoic acid around the stem did not change the effect on petiolar epinasty of auxin applied to the decapitated shoot or around the stem. Radioautography showed that the label from 14C-indoleacetic acid applied apically entered the petiole and midrib tissue; however, extraction showed that only a fraction of the label in these tissues was in the form of indoleacetic acid. Removal of leaflets from leaves induced hyponasty in the midrib region, and application of auxin to the leaflet stubs produced midrib epinasty; carbon dioxide did not block the action of auxin in this type of epinasty. Removal of leaflets from leaves did not alter the effect of apically applied auxin on petiolar epinasty. The data are consistent with the hypothesis that the oblique orientation of leaves in tomato plants is influenced by two epinastic responses. Petiolar epinasty is controlled by the apical region on the stem and is due to the action of auxin-induced ethylene; and midrib epinasty is due to an action of auxin other than through ethylene.

Kazemi, Saidollah; Kefford, Noel P.

1974-01-01

356

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

Microsoft Academic Search

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

Biao Jin; Li Wang; Jing Wang; Ke-Zhen Jiang; Yang Wang; Xiao-Xue Jiang; Cheng-Yang Ni; Yu-Long Wang; Nian-Jun Teng

2011-01-01

357

Ecology and ecophysiology of tree stems: corticular and wood photosynthesis  

NASA Astrophysics Data System (ADS)

Below the outer peridermal or rhytidomal layers, most stems of woody plants possess greenish tissues. These chlorophyll-containing tissues (the chlorenchymes) within the stems are able to use the stem internal CO2 and the light penetrating the rhytidome to photoassimilate and produce sugars and starch. Although net photosynthetic uptake of CO2 is rarely found, stem internal re-fixation of CO2 in young twigs and branches may compensate for 60-90% of the potential respiratory carbon loss. Isolated chlorenchymal tissues reveal rather high rates of net photosynthesis (being up to 75% of the respective rates for leaf photosynthesis). Corticular photosynthesis is thus thought to be an effective mechanism for recapturing respiratory carbon dioxide before it diffuses out of the stem. Furthermore, chloroplasts of the proper wood or pith fraction also take part in stem internal photosynthesis. Although there has been no strong experimental evidence until now, we suggest that the oxygen evolved during wood or pith photosynthesis may play a decisive role in avoiding/reducing stem internal anaerobiosis.

Pfanz, H.; Aschan, G.; Langenfeld-Heyser, R.; Wittmann, C.; Loose, M.

2002-03-01

358

Leaf emergence in relation to leaf traits in temperate woody species in East-Chinese Quercus fabri forests  

NASA Astrophysics Data System (ADS)

To determine the effect of leaf traits on leaf emergence phenology, timing of leaf emergence, leaf expansion rate, durations of leaf emergence and expansion, leaf mass per area (LMA) and leaf size were investigated for 48 woody species from 25 families in two closed Chinese white oak ( Quercus fabri) forests of eastern China. Cross-species regression and phylogenetic regression were employed to examine the relationship between leaf phenology and leaf traits. Leaf area, LMA, and leaf expansion rate were found to be significantly greater in canopy trees than in understory shrubs in the oak forests. However, there was no significant difference in timing of leaf emergence and durations of leaf emergence and expansion between canopy and understory species. The large-LMA species leafed out earlier than the species with small LMA. The small-leaved species leafed out earlier than the species with large leaves, but the large-leaved species were greater in leaf expansion rate than their counterparts. Leaf expansion rate was positively correlated with leaf area and timing of leaf emergence, but no significant relationship was found between leaf size and leaf expansion period. These results suggest that large- and small-leaved species possibly employed different strategies to minimize herbivory damage, i.e. early leafing to avoid defoliator damage in small-leaved species and fast expanding and thereby shortening vulnerable time to herbivores in large-leaved species. It could be inferred that the species with small leaves and large-LMA leafed out early in the oak forests, thereby permitting less energy loss than their counterparts under the influence of frost in early spring. In general, early leaf emergence is of significance for high LMA species to increase carbon gain in temperate broad-leaved forests, but it is not related to plant height. Leaf size and leaf expansion period are not necessarily correlated.

Sun, Shucun; Jin, Dongmei; Li, Rongjin

2006-09-01

359

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

360

CANOPY PHOTOSYNTHESIS, SPECIFIC LEAF WEIGHT, AND YIELD COMPONENTS OF COTTON UNDER VARYING NITROGEN SUPPLY  

Microsoft Academic Search

Nitrogen (N) nutrition greatly affects the number of nodes above the uppermost white flower (NAWF), an indicator of plant growth and development in cotton (Gossypium hirsutum L). In this study, we examined relationships of NAWF with canopy photosynthesis (CP), specific leaf weight (SLW), and yield components, boll number, and dry weight in cotton under varying N supply. Four pre-plant soil

Bhaskar R. Bondada; Derrick M. Oosterhuis

2001-01-01

361

Telomeres, stem cells, senescence, and cancer  

PubMed Central

Mammalian aging occurs in part because of a decline in the restorative capacity of tissue stem cells. These self-renewing cells are rendered malignant by a small number of oncogenic mutations, and overlapping tumor suppressor mechanisms (e.g., p16INK4a-Rb, ARF-p53, and the telomere) have evolved to ward against this possibility. These beneficial antitumor pathways, however, appear also to limit the stem cell life span, thereby contributing to aging.

Sharpless, Norman E.; DePinho, Ronald A.

2004-01-01

362

Adult stem cells and cardiac regeneration.  

PubMed

There is worldwide demand for therapies to promote the robust repair and regeneration with maximum regain of function of particular tissues and organs damaged by disease or injury. The potential role of adult stem cells has been highlighted by an increasing number of in vitro and in vivo studies. Nowhere is this more evident than in adult stem cell-based therapies being explored to promote cardiac regeneration. In spite of encouraging advances, significant challenges remain. PMID:23775698

Turksen, Kursad

2013-10-01

363

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

PubMed

"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. PMID:24167510

Burkhardt, Juergen; Hunsche, Mauricio

2013-10-24

364

"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

365

High frequency, direct shoot regeneration from greenhouse-derived leaf disks of six strawberry cultivars.  

PubMed

Leaf disks derived from either two-month-old GreenHouse-grown (GHD) strawberry plants or in vitro plantlets were cultured on MS media amended with 2 mg L(-1) Thidiazuron (TDZ), incubated for four weeks in the dark then for another four weeks under 16/8 h light regime. Regeneration capacity of leaf disks was compared to meristem-derived propagules in six strawberry cultivars. Direct shoot regeneration occurred in all tested cultivars with different frequencies depending on explant source. From GDH leaf disks, the cultivars Camarosa, Gaviota and Seascape produced the highest number of shoots/explant (38, 31 and 31 shoots, respectively). However, optimum number of shoots/explant from in vitro leaf disks was achieved in the cultivars Carlsbad, Chandler and Sweet Charlie (13.3, 12.6 and 12.3 shoots, respectively). In general, regeneration capacity of GHD leaf discs was more than two-folds of that obtained from in vitro leaf disks. The efficiency of meristem culture was intermediate between the above two systems. Rooted plantlets were successfully acclimatized under mist. The only morphological abnormality detected was a white streaked variant observed out of 456 Camarosa plants derived from meristem culture. SDS-PAGE of protein profile proved consistency in banding patterns of mother plants and those derived from direct regeneration or meristem proliferation. PMID:19069992

Mohamed, Fouad H; Beltagi, Mohamed S; Ismail, Mona A; Omar, Ginesia F

2007-01-01

366

A mathematical model linking tree sap flow dynamics to daily stem diameter fluctuations and radial stem growth.  

PubMed

To date, models for simulating sap flow dynamics in individual trees with a direct link to stem diameter variation include only the diameter fluctuation driven by a change in stem water storage. This paper reports results obtained with a comprehensive flow and storage model using whole-tree leaf transpiration as the only input variable. The model includes radial stem growth based on Lockhart's equation for irreversible cell expansion. It was demonstrated that including growth is essential to obtaining good simulation results. To model sap flow dynamics, capacitance of storage tissues was assumed either constant (i.e., electrical analogue approach) or variable and dependent on the water content of the respective storage tissue (i.e., hydraulic system approach). These approaches resulted in different shapes for the desorption curve used to calculate the capacitance of storage tissues. Comparison of these methods allowed detection of specific differences in model simulation of sap flow at the stem base (F(stem)) and stem diameter variation (D). Sensitivity analysis was performed to select a limited subset of identifiable parameters driving most of the variability in model predictions of F(stem) and D Both the electrical analogue and the hydraulic system approach for the flow and storage model were successfully calibrated and validated for the case of a young beech tree (Fagus sylvatica L.). Use of an objective model selection criterion revealed that the flow and storage model based on the electrical analogue approach yielded better predictions. PMID:16356899

Steppe, Kathy; De Pauw, Dirk J W; Lemeur, Raoul; Vanrolleghem, Peter A

2006-03-01

367

7 CFR 29.2438 - Thin Leaf (C Group).  

Code of Federal Regulations, 2013 CFR

...and specifications C1L Choice Light-brown Thin Leaf. Thin to medium body, mature to ripe...Light-brown Thin Leaf. Thin to medium body, mature to ripe...percent injury tolerance. Choice Medium-brown Thin Leaf....

2013-01-01

368

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, narrow...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, stringy... Ripe, firm leaf structure, fleshy, lean in oil, weak color intensity,...

2009-01-01

369

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, narrow...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, stringy... Ripe, firm leaf structure, fleshy, lean in oil, weak color intensity,...

2010-01-01

370

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

2013-01-01

371

7 CFR 29.2437 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...injury tolerance. B3F Good Medium-brown Heavy Leaf. ...injury tolerance. B3M Good Mixed Color Heavy Leaf. Medium to heavy body, mature...injury tolerance. B3G Good Green Heavy Leaf. Medium to heavy body,...

2013-01-01

372

7 CFR 29.2662 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...injury tolerance. B3F Good Medium-brown Heavy Leaf. Medium...injury tolerance. B3VF Good Greenish Medium-brown Heavy Leaf. Medium...injury tolerance. B3G Good Green Heavy Leaf. Medium to heavy body,...

2013-01-01

373

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

374

Automobile leaf springs from composite materials  

Microsoft Academic Search

The automobile industry has shown increased interest in the replacement of steel springs with fiberglass reinforced composite leaf springs. Therefore, the aim of this paper is to present a general study on the analysis, design and fabrication of composite springs. From this viewpoint, the suspension spring of a compact car, “a jeep” was selected as a prototype.A single leaf, variable

H. A. Al-Qureshi

2001-01-01

375

Leaf Litter Decomposition in Three Adirondack Lakes.  

National Technical Information Service (NTIS)

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. ...

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

1983-01-01

376

Photovoltaic Leaf Area Meter Development and Testing  

Microsoft Academic Search

Photovoltaic (PV) panel was used to develop a simple and practical leaf area meter. Components of the developed PV leaf area meter include a PV panel as sensor, a wooden cabinet as enclosure, a flashlight as light source, and a commercial digital multimeter for voltage measurement. The principle of projected area measurement is the voltage generated by the PV panel

C. Igathinathane; B. Chennakesavulu; K. Manohar; A. R. Womac; L. O. Pordesimo

2008-01-01

377

Cardiac stem cell therapy: stemness or commitment?  

PubMed

Cardiac stem cell therapy to promote engraftment of de novo beating cardiac muscle cells in cardiomyopathies could potentially improve clinical outcomes for many patients with congestive heart failure. Clinical trials carried out over the last decade for cardiac regeneration have revealed inadequacy of current approaches in cell therapy. Chief among them is the choice of stem cells to achieve the desired outcomes. Initial enthusiasm of adult bone marrow stems cells for myocyte regeneration has largely been relegated to paracrine-driven, donor cell-independent, endogenous cardiac repair. However, true functional restoration in heart failure is likely to require considerable myocyte replacement. In order to match stem cell application to various clinical scenarios, we review the necessity to preprime stem cells towards cardiac fate before myocardial transplantation and if these differentiated stem cells could confer added advantage over current choice of undifferentiated stem cells. We explore differentiation ability of various stem cells to cardiac progenitors/cardiomyocytes and compare their applicability in providing targeted recovery in light of current clinical challenges of cell therapy. PMID:22943934

Mehta, Ashish; Shim, Winston

2012-08-27

378

Targeting Leukemic Stem Cells  

Microsoft Academic Search

The stem cell concept and asymmetric cell division are best understood in the hematopoietic system. Hematopoietic malignancies\\u000a resemble many of the known normal mature hematopoietic lineages that originate from stem cells. Leukemias in particular, were\\u000a shown to arise from leukemic stem cells. General characteristics of stem cells such as self-renewal, self-protection and proliferative\\u000a quiescence clearly point toward the need for

Angelika M. Burger

379

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

380

Stem cell culture engineering  

Microsoft Academic Search

Stem cells have the capacity for self renewal and undergo multilineage differentiation. Stem cells isolated from both blastocysts and adult tissues represent valuable sources of cells for applications in cell therapy, drug screening and tissue engineering. While expanding stem cells in culture, it is critical to maintain their self?renewal and differentiation capacity. In generating particular cell types for specific applications,

Gargi Seth; Catherine M. Verfaillie

2005-01-01

381

Human Embryonic Stem Cells  

Microsoft Academic Search

Human embryonic stem cells hold great promise in furthering our treatment of disease and increasing our understanding of early development. This chapter describes protocols for the derivation and maintenance of human embryonic stem cells. In addition, it summarizes briefly several alternative methods for the culture of human embryonic stem cells. Thus, this chapter provides a good starting point for researchers

Hidenori Akutsu; Chad A. Cowan; Douglas Melton

2006-01-01

382

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...

2013-07-01

383

Stem Cells in Regenerative Medicine  

PubMed Central

Background: A number of cardiovascular, neurological, musculoskeletal and other diseases have a limited capacity for repair and only a modest progress has been made in treatment of brain diseases. The discovery of stem cells has opened new possibilities for the treatment of these maladies, and cell therapy now stands at the cutting-edge of modern regenerative medicine and tissue engineering. Experimental data and the first clinical trials employing stem cells have shown their broad therapeutic potential and have brought hope to patients suffering from devastating pathologies of different organs and systems. Aims: Here, we briefly review the main achievements and trends in cell-based therapy, with an emphasis on the main types of stem cells: embryonic, mesenchymal stromal and induced pluripotent cells. Discussion: Many questions regarding the application of stem cells remain unanswered, particularly tumorigenicity, immune rejection and danger of gene manipulation. Currently, only MSC seems to be safe and might be considered to be a leading candidate for human application to treat pathologies that affect the cardiovascular, neurological and musculoskeletal systems.

Sykova, Eva; Forostyak, Serhiy

2013-01-01

384

Stem Cells and Liver Regeneration  

PubMed Central

One of the defining features of the liver is the capacity to maintain a constant size despite injury. Although the precise molecular signals involved in the maintenance of liver size are not completely known, it is clear that the liver delicately balances regeneration with overgrowth. Mammals, for example, can survive surgical removal of up to 75% of the total liver mass. Within 1 week after liver resection, the total number of liver cells is restored. Moreover, liver overgrowth can be induced by a variety of signals, including hepatocyte growth factor or peroxisome proliferators; the liver quickly returns to its normal size when the proliferative signal is removed. The extent to which liver stem cells mediate liver regeneration has been hotly debated. One of the primary reasons for this controversy is the use of multiple definitions for the hepatic stem cell. Definitions for the liver stem cell include the following: (1) cells responsible for normal tissue turnover, (2) cells that give rise to regeneration after partial hepatectomy, (3) cells responsible for progenitor-dependent regeneration, (4) cells that produce hepatocyte and bile duct epithelial phenotypes in vitro, and (5) transplantable liver-repopulating cells. This review will consider liver stem cells in the context of each definition.

DUNCAN, ANDREW W.; DORRELL, CRAIG; GROMPE, MARKUS

2011-01-01

385

High-Resolution Genomic Profiling of Chromosomal Abnormalities in Human Stem Cells Using the 135 K StemArray  

PubMed Central

Culturing stem cells for an extended period of time can lead to acquired chromosomal aberrations. Determining the copy number variant (CNV) profile of stem cell lines is critical since CNVs can have dramatic effects on gene expression and tumorigenic potential. Here, we describe an improved version of our StemArray, a stem-cell-focused comparative genomic hybridization (aCGH) microarray, which contains 135,000 probes and covers over 270 stem cell and cancer related genes at the exon level. We have dramatically increased the median probe spacing throughout the genome in order to obtain a higher resolution genetic profile of the cell lines. To illustrate the importance of using the StemArray, we describe a karyotypically normal iPSC line in which we detected acquired chromosomal variations that could affect the cellular phenotype of the cells. Identifying adaptive chromosomal aberrations in stem cell lines is essential if they are to be used in regenerative medicine.

Elliott, Aaron M.; Hohenstein Elliott, Kristi A.; Kammesheidt, Anja

2012-01-01

386

Maturation in Douglas-fir: I. Changes in stem, branch and foliage characteristics associated with ontogenetic aging.  

PubMed

Two experiments were conducted to characterize changes associated with ontogenetic aging in coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and to identify possible maturation "markers" for this species. In the first experiment (Experiment 1), scions of ages 1, 4 and 9 years were collected from four seed zones in field progeny tests and grafted onto 1-year-old rootstocks. In Experiment 2, scions from five full-sib families of ages 1 and 10 years were collected from one progeny test and similarly grafted. Grafts for both experiments were planted in the field in a completely randomized design. The grafts were measured after two and six growing seasons. In Experiment 1, graft diameter, number of terminal bud flushes per year, number of branches, and branch length decreased with age. Plagiotropic angle and needle weight increased. All variables except needle length had a significant age x seed zone interaction. After 6 years, internodal stem diameters, numbers of nodal and internodal branches, and length and diameter of internodal branches decreased with age, and there were age x seed zone interactions with most variables. In Experiment 2, graft height and diameter, number of flushes, number and size of lateral branches, needle length and weight decreased with age. After 6 years, height and diameter, size and number of nodal and internodal branches, and leaf chlorophyll concentration (measured in April) decreased, but there were relatively few age x family interactions. An analysis based on traits that were significantly affected by age, but that did not interact with seed zone or family, indicated that main stem diameter, nodal branch length and nodal branch diameter were the most consistent and reliable maturation markers. PMID:14967615

Ritchie, G A; Keeley, J W

1994-11-01

387

Mitochondria in stem cells  

PubMed Central

The current status of knowledge about mitochondrial properties in mouse, monkey and human embryonic, adult and precursor stem cells is discussed. Topics include mitochondrial localization patterns, oxygen consumption and ATP content in cells as they relate to the maintenance of stem cell properties and subsequent differentiation of stem cells into specific cell types. The significance of the perinuclear arrangement of mitochondria, which may be a characteristic feature of stem cells, as well as the expression of mitochondrial DNA regulatory proteins and mutations in the mitochondrial stem cell genome is also discussed.

Lonergan, Thomas; Bavister, Barry; Brenner, Carol

2011-01-01

388

Effects of coal-smoke pollutants from different sources on the growth, chlorophyll content, stem anatomy and cuticular traits of Euphorbia hirta L.  

PubMed

Variations occurred in the growth, assimilate partitioning, chlorophyll content, stem anatomy and leaf cuticular traits of Euphorbia hirta L. on long-term exposure to coal-smoke pollutants prevailing at two sites, one situated close to a railway loco shed (site B) and another in the vicinity of a thermal power plant (site C). The Botanical Garden of Aligarh Muslim University, Aligarh, was considered as a control site (A). Site C possessed a greater load of coal-smoke pollutants than site B. The present study had shown that coal-smoke pollutants have led to a decrease in plant height, jeopardised the production of leaves and enhanced their fall, and caused a reduction in leaf area, leading to decreases of the total photosynthetic area of the plants, with increasing pollution load. The losses incurred in chlorophyll a were relatively more than chlorophyll b and, as a result, the total chlorophyll contents of leaves were decreased in polluted plants. The dry weights of stems, roots and leaves were decreased to different degrees, whereas the shoot/root dry weight ratio was found to increase in the polluted environment. The growth of stem cortex and pith were slightly affected on site B, but showed significant decreases on site C, due to a greater load of pollutants. Decreased area of xylem tissue was found to couple with an increasing number of vessels of reduced sizes. The stomatal density, pore size and index showed decreases, while the epidermal cells were larger and trichomes longer, on both surfaces of polluted leaves. PMID:15092709

Gupta, M C; Ghouse, A K

1987-01-01

389

Amnion-derived stem cells: in quest of clinical applications  

Microsoft Academic Search

In the promising field of regenerative medicine, human perinatal stem cells are of great interest as potential stem cells\\u000a with clinical applications. Perinatal stem cells could be isolated from normally discarded human placentae, which are an ideal\\u000a cell source in terms of availability, the fewer number of ethical concerns, less DNA damage, and so on. Numerous studies have\\u000a demonstrated that

Toshio Miki

2011-01-01

390

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

391

The Proliferation and Differentiation of Stem Cell Journals  

Microsoft Academic Search

As scientists position themselves in translating the therapeutic potential of stem cells from laboratory to clinical applications,\\u000a publishing companies have taken this rapidly evolving field as a unique opportunity to launch new journals for dissemination\\u000a of stem cell research. Over the last decade, the significant increase in the number of stem cell-based journals has created\\u000a a conundrum. At stake is

Paul R. Sanberg; Cesar V. Borlongan

2010-01-01

392

Mobilization of Stem Cells\\/Progenitor Cells by Physical Activity  

Microsoft Academic Search

\\u000a A number of publications have provided evidence that exercise and physical activity are linked to the activation, mobilization,\\u000a and differentiation of various types of stem cells. Exercise may improve organ regeneration and function. This review characterizes\\u000a different stem and progenitor cells and their sources and summarizes mechanisms by which exercise contributes to stem-cell-induced\\u000a regeneration and adaptation in different tissues. The

Patrick Wahl; Wilhelm Bloch

393

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

394

Leaf-area index and light attenuation in rapidly expanding shrub thickets.  

PubMed

There is increasing interest in the changes in ecosystem services that accompany the conversion of grasslands to shrub-dominated communities. Shrub structure and associated effects on the light environment may be especially important in affecting productivity and diversity. Leaf-area index (LAI) and understory light levels of Morella cerifera shrub thickets were assessed on Hog Island, Virginia, USA, at four sites along a soil chronosequence. LAI was estimated from annual leaf litter, with allometric models relating stem diameter to leaf area, with a portable integrating radiometer (LI-COR LAI-2000), and from photosynthetically active radiation (PAR) using the Beer-Lambert law. For the two youngest thickets, LAI estimates from leaf litter (approximately 10.0) approached levels often associated with tropical rain forest. Allometric models estimated LAI values at 9.8 and 12.5 for the same thickets. High LAI in thickets also results in high light attenuation. Light levels within thickets were as low as 0.7% of above-canopy PAR in the youngest thicket. These data suggest that M. cerifera shrub thickets have a very high potential for annual net primary production. Furthermore, extreme modification of the light environment, coupled with heavy shrub litter fall, may exclude potential competitors during thicket establishment and rapidly alter community structure and ecosystem function. PMID:17479769

Brantley, Steven T; Young, Donald R

2007-02-01

395

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

396

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

397

Geotaxis and leaf-surface preferences mitigate negative effects of a predatory mite on an herbivorous mite.  

PubMed

Reproductive success and population growth of an herbivorous mite are limited by activities of phytoseiid predators. However, occurrences on upper versus lower leaf surfaces are sometimes mismatched between these prey and predators. The mismatch potentially mitigates predation risk for the prey species. We assessed factors that affect mite distributions on leaf surfaces, testing whether the presence of the phytoseiid mite Phytoseius nipponicus alters the leaf-surface distribution and reproductive success of the herbivorous false spider mite Brevipalpus obovatus. The host plant was Viburnum erosum var. punctatum (Adoxaceae). Leaves were set in natural (TRUE) and reversed (upside down; INVERTED) orientations using experimental devices. Both surfaces were accessible to mites. We detected lower and abaxial leaf-surface preferences in P. nipponicus. In contrast, upper and adaxial surfaces were preferred by B. obovatus. Thus, prey and predatory mites accumulated on different sides of leaves. Presence of the predator also indirectly decreased egg production in B. obovatus. Brevipalpus obovatus females actively avoided leaf surfaces with elevated predator numbers; these females shifted their distributions and changed oviposition sites to leaf surfaces with fewer predators. In consequence, B. obovatus eggs on the upper sides of leaves were less frequently preyed upon than were those on lower sides. We suggest that upper leaf-surface exploitation in this particular herbivorous mite species mitigates predation risk from phytoseiid mites, which prefer lower leaf surfaces. PMID:23011108

Sudo, Masaaki; Osakabe, Masahiro

2012-09-26

398

De Novo Kidney Regeneration with Stem Cells  

PubMed Central

Recent studies have reported on techniques to mobilize and activate endogenous stem-cells in injured kidneys or to introduce exogenous stem cells for tissue repair. Despite many recent advantages in renal regenerative therapy, chronic kidney disease (CKD) remains a major cause of morbidity and mortality and the number of CKD patients has been increasing. When the sophisticated structure of the kidneys is totally disrupted by end stage renal disease (ESRD), traditional stem cell-based therapy is unable to completely regenerate the damaged tissue. This suggests that whole organ regeneration may be a promising therapeutic approach to alleviate patients with uncured CKD. We summarize here the potential of stem-cell-based therapy for injured tissue repair and de novo whole kidney regeneration. In addition, we describe the hurdles that must be overcome and possible applications of this approach in kidney regeneration.

Yokote, Shinya; Yamanaka, Shuichiro; Yokoo, Takashi

2012-01-01

399

Ionizing Radiation Induces Stemness in Cancer Cells  

PubMed Central

The cancer stem cell (CSC) model posits the presence of a small number of CSCs in the heterogeneous cancer cell population that are ultimately responsible for tumor initiation, as well as cancer recurrence and metastasis. CSCs have been isolated from a variety of human cancers and are able to generate a hierarchical and heterogeneous cancer cell population. CSCs are also resistant to conventional chemo- and radio-therapies. Here we report that ionizing radiation can induce stem cell-like properties in heterogeneous cancer cells. Exposure of non-stem cancer cells to ionizing radiation enhanced spherogenesis, and this was accompanied by upregulation of the pluripotency genes Sox2 and Oct3/4. Knockdown of Sox2 or Oct3/4 inhibited radiation–induced spherogenesis and increased cellular sensitivity to radiation. These data demonstrate that ionizing radiation can activate stemness pathways in heterogeneous cancer cells, resulting in the enrichment of a CSC subpopulation with higher resistance to radiotherapy.

Ghisolfi, Laura; Keates, Andrew C.; Hu, Xingwang; Lee, Dong-ki; Li, Chiang J.

2012-01-01

400

Influence of leaf detritus type on production and longevity of container-breeding mosquitoes.  

PubMed

Freshwater ecosystems are positioned at low levels in the landscape and receive large inputs of diverse plant-based detritus, a major source of energy for consumers in aquatic ecosystems. We conducted field experiments in Urbana, IL to determine the independent and combined effects of leaves of common tree species including the northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marshall), and common hackberry (Celtis occidentalis L.) on the performance of container-dwelling mosquitoes, especially Culex restuans Theobald (Diptera: Culicidae). We tested the hypothesis that leaf species have asymmetric effects on adult mosquito production and longevity. Hackberry followed by combined leaf treatments and maple produced the greatest number of pupae, whereas oak leaves produced the fewest. Leaf treatments had no significant effects on adult female sizes but female longevity was significantly lower in oak leaf treatments compared with the other leaf treatments. These findings support the hypothesis that leaf species identity influences the performance of container-dwelling mosquitoes with potential consequences for the transmission of infectious diseases. PMID:23068161

Muturi, Ephantus J; Allan, Brian F; Ricci, James

2012-10-01

401

Why so strong for the lotus leaf?  

NASA Astrophysics Data System (ADS)

The authors discussed the potential reasons why the lotus leaf is so strong by means of scanning electron microscopy (SEM). The results showed that the good mechanical properties of lotus leaf should be attributed to its architecture, such as paralleled microtubes structure, umbrellalike structure, and hierarchically layered hexagon structure. The important observation from this work is that the surface of the rear face of the lotus leaf seems to be constituted by the layers of hexagons whose hierarchical pilling up of size decreases as we go deeper from surface. This is a typical fractal-like phenomenon.

Guo, Zhiguang; Liu, Weimin; Su, Bao-Lian

2008-11-01

402

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

403

Stem cells in the postnatal pituitary?  

PubMed

Tissue-specific stem cells are uncovered in a growing number of organs by their molecular expression profile and their potential for self-renewal, multipotent differentiation and tissue regeneration. Whether the pituitary gland also contains a pool of versatile 'master' cells that drive homeostatic, plastic and regenerative cell ontogenesis is at present unknown. Here, I will give an overview of data that may lend support to the existence of stem cells in the postnatal pituitary. During the many decades of pituitary research, various approaches have been used to hunt for the pituitary stem cells. Transplantation and regeneration studies advanced chromophobes as possible source of new hormonal cells. Clonogenicity approaches identified pituitary cells that clonally expand to floating spheres, or to colonies in adherent cell cultures. Behavioural characteristics and changes of marginal, follicular and folliculostellate cells during defined developmental and (patho-)physiological conditions have been interpreted as indicative of a stem cell role. Expression of potential stem cell markers like nestin, as well as topographical localization in the marginal zone around the cleft has also been considered to designate pituitary stem cells. Finally, a 'side population' was recently identified in the postnatal pituitary which in many other tissues represents a stem cell-enriched fraction. Taken together, in the course of the long-standing study of the pituitary, several arguments have been presented to support the existence of stem cells, and multiple cell types have been placed in the spotlight as possible candidates. However, none of these cells has until now unequivocally been shown to meet all quintessential characteristics of stem cells. PMID:17337880

Vankelecom, Hugo

2007-02-23

404

Global leaf trait relationships: mass, area, and the leaf economics spectrum.  

PubMed

The leaf economics spectrum (LES) describes multivariate correlations that constrain leaf traits of plant species primarily to a single axis of variation if data are normalized by leaf mass. We show that these traits are approximately distributed proportional to leaf area instead of mass, as expected for a light- and carbon dioxide-collecting organ. Much of the structure in the mass-normalized LES results from normalizing area-proportional traits by mass. Mass normalization induces strong correlations among area-proportional traits because of large variation among species in leaf mass per area (LMA). The high LMA variance likely reflects its functional relationship with leaf life span. A LES that is independent of mass- or area-normalization and LMA reveals physiological relationships that are inconsistent with those in global vegetation models designed to address climate change. PMID:23539179

Osnas, Jeanne L D; Lichstein, Jeremy W; Reich, Peter B; Pacala, Stephen W

2013-03-28

405

Lymphohematopoietic stem cell engraftment.  

PubMed

Traditional dogma has stated that space needs to be opened by cytoxic myeloablative therapy in order for marrow stem cells to engraft. Recent work in murine transplant models, however, indicates that engraftment is determined by the ratio of donor to host stem cells, i.e., stem cell competition. One hundred centigray whole body irradiation is stem cell toxic and nonmyelotoxic, thus allowing for higher donor chimerism in a murine syngeneic transplant setting. This nontoxic stem cell transplantation can be applied to allogeneic transplant with the addition of a tolerizing step; in this case presensitization with donor spleen cells and administration of CD40 ligand antibody to block costimulation. The stem cells that engraft in the nonmyeloablated are in G0, but are rapidly induced (by 12 hours) to enter the S phase after in vivo engraftment. Exposure of murine marrow to cytokines (IL-3, IL-6, IL-11 and steel factor) expands progenitor clones, induces stem cells into cell cycle, and causes a fluctuating engraftment phenotype tied to phase of cell cycle. These data indicate that the concepts of stem cell competition and fluctuation of stem cell phenotype with cell cycle transit should underlie any new stem cell engraftment strategy. PMID:10372109

Quesenberry, P J; Stewart, F M; Zhong, S; Habibian, H; McAuliffe, C; Reilly, J; Carlson, J; Dooner, M; Nilsson, S; Peters, S; Stein, G; Stein, J; Emmons, R; Benoit, B; Bertoncello, I; Becker, P

1999-04-30

406

Hematopoietic Stem Cells and Somatic Stem Cells  

Microsoft Academic Search

\\u000a Stem cells are unspecialized cells that can differentiate to generate more specialized cell types responsible for tissue-specific\\u000a function. During development, the differentiation of pluripotent embryonic stem cells leads to the production of specialized\\u000a somatic cells that are ultimately responsible for the structure and function of all adult tissues and organs. “Naturally”\\u000a pluripotent cells exist only at the earliest stages of

Kah Yong Tan; Francis S. Kim; Amy J. Wagers; Shane R. Mayack

407

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

408

Genetic control of stem cells: implications for aging.  

PubMed

Stem cells are currently at the center of both controversy and notoriety. The harvest of human embryonic or fetal stem cells, at least with methods available now, necessarily involves the sacrifice of the embryo or fetus. This critical step in the procurement of stem cells has stimulated intense discussion at all levels of academia, government, and society in general. What societal benefits, if any, justify such a strategy for obtaining these stem cells? In other species it has been possible to generate virtually all cell types found in adult organs from embryonic stem cells. This ability has opened endless clinical possibilities for tissue and organ replacement through the transplantation of cells derived from embryonic stem cells. Luckily, there may be an alternative to this ethical dilemma. It is becoming increasingly clear that stem cells exist in many, if not all, adult tissues. Adult stem cells normally replenish tissue cells lost through the wear and tear of aging or damage from injury or disease. With the proper coaxing in tissue culture and when transplanted, these stem cells may regenerate the full repertoire of organotypic cells and thus may therapeutically regenerate tissues in vivo in much the same way as embryonic stem cells do. For several reasons, the best-studied stem cells are those of the blood-forming system. Mature blood cells generally have short functional life spans, usually measured in days, and therefore require replenishment at a steady pace throughout one's lifetime. Stem cells are intimately involved in this renewal and, because of the relative ease of access to the bone marrow, stem cells have been well studied. Second, bone marrow transplantation following radiation or high-dose chemotherapy in the treatment of cancer has fostered research on the basic biology and therapeutic uses of hematopoietic stem cells over the more than 30 years stem cell transplantation has been used clinically. It is my aim to review what is known about the genes controlling hematopoietic stem cell function. Identifying, and ultimately manipulating, the genes that regulate stem cell number, replication rate, and self-renewal capacity may have important clinical benefits. I discuss evidence suggesting that the characterization of least some of these stem cell genes will shed light on mechanisms important in the aging process. I advance the hypothesis that stem cells accumulate cellular damage during aging that diminishes their developmental potency and ability to replenish blood cells, particularly after hematopoietic stress. In this view, the impaired function of stem cells in hematopoietic and in other self-renewing tissues limits the longevity of animals, and perhaps of humans. PMID:12568297

Van Zant, Gary

2003-01-01

409

Relationships between specific leaf weight and mineral concentration among genotypes  

Microsoft Academic Search

Physiological functions are usually expressed on a leaf area basis, whereas leaf mineral concentrations are often expressed on a dry matter basis. If specific leaf weight (SLW; g DM m?2 leaf) differs among genotypes then variability in mineral concentration may depend on the basis of expression. Data from experiments with peanut (Arachis hypogaea L.) and pearl millet [Pennisetum glaucum (L.)

R. Harold Brown; George T. Byrd

1997-01-01

410

Simulating Leaf Area of Corn Plants at Contrasting Water Status  

Technology Transfer Automated Retrieval System (TEKTRAN)

An exponential decay function was fitted with literature data to describe the decrease in leaf expansion rate as leaf water potential decreases. The fitted function was then applied to modify an existing leaf area simulation module in a soil-plant-atmosphere continuum model in order to simulate leaf...

411

Calibration of the Minolta SPAD502 leaf chlorophyll meter  

Microsoft Academic Search

Use of leaf meters to provide an instantaneous assessment of leaf chlorophyll has become common, but calibration of meter output into direct units of leaf chlorophyll concentration has been difficult and an understanding of the relationship between these two parameters has remained elusive. We examined the correlation of soybean (Glycine max) and maize (Zea mays L.) leaf chlorophyll concentration, as

John Markwell; John C. Osterman; Jennifer L. Mitchell

1995-01-01

412

7 CFR 29.2663 - Thin Leaf (C Group).  

Code of Federal Regulations, 2013 CFR

...injury tolerance. C3F Good Medium-brown Thin Leaf...tolerance. C3VF Good Greenish Medium-brown Thin Leaf... C5VF Low Greenish Medium-brown Thin Leaf...injury tolerance. C3G Good Green Thin Leaf....

2013-01-01

413

Assessing the generality of global leaf trait relationships  

Microsoft Academic Search

Summary • Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation- climate models. • A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus

Ian J. Wright; Peter B. Reich; Johannes H. C. Cornelissen; Daniel S. Falster; Eric Garnier; Kouki Hikosaka; Byron B. Lamont; William Lee; C. H. Lusk; J. Oleksyn; N. Osada; R. Villar; D. I. Warton; M. Westoby

2005-01-01

414

Elevated COâ and leaf shape: Are dandelions getting toothier?  

Microsoft Academic Search

Heteroblastic leaf development in Taraxacum officinale is compared between plants grown under ambient (350 ppm) vs. elevated (700 ppm) COâ levels. Leaves of elevated COâ plants exhibited more deeply incised leaf margins and relatively more slender leaf laminae than leaves of ambient COâ plants. These differences were found to be significant in allometric analyses that controlled for differences in leaf

S. C. Thomas; F. A. Bazzaz

1996-01-01

415

RFLP tagging of QTLs conditioning specific leaf weight and leaf size in soybean  

Microsoft Academic Search

Selection for high specific leaf weight (SLW) in soybean [Glycine max (L) Merr.] may increase apparent photosynthetic rate per unit leaf area (AP), which in turn may improve seed yield. In general,\\u000a the SLW and leaf size are negatively correlated in soybean. To maximize total photosynthetic performance, and perhaps the\\u000a seed yield, of a soybean cultivar, it would be necessary

M. A. R. Mian; R. Wells; T. E. Carter Jr.; D. A. Ashley; H. R. Boerma

1998-01-01

416

Effect of Image Processing of a Leaf Photograph on the Calculated Fractal Dimension of Leaf Veins  

Microsoft Academic Search

Digital photography is a promised method for estimating the fractal characteristics of leaf veins. In this study, the effects\\u000a of different threshold levels and image processing methods using Adobe Photoshop software on the fractal dimension values\\u000a were examined from a digital photo of nectarine leaf. The results showed that the nectarine leaf vein has typical fractal\\u000a characteristics and its fractal

Yun Kong; Shaohui Wang; Chengwei Ma; Baoming Li; Yuncong Yao

2007-01-01

417

Bionetworking: experimental stem cell therapy and patient recruitment in India  

Microsoft Academic Search

Over the last three to four years, an increasing number of private and public sector tertiary level hospitals and research centres in India have been using stem cell therapy, especially adult stem cell therapy, in the guise of experimental therapy for a variety of medical conditions. The promotion and growth of this experimental field across local and national borders traverses

Prasanna Kumar Patra; Margaret Sleeboom-Faulkner

2009-01-01

418

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

419

Identification and Characterization of Mouse Cochlear Stem Cells  

Microsoft Academic Search

Genetic, noise- and drug-induced loss of hair cells in the mouse and human cochlea leads to permanent hearing loss due to lack of regeneration of hair cells, which may be due to reduced numbers or loss of the regenerative ability of stem cells in the adult cochlea. We hypothesized that the mouse neonate cochlea harbors stem cells capable of differentiating

Michael V. Yerukhimovich; Lianhua Bai; Daniel H.-C. Chen; Robert H. Miller; Kumar N. Alagramam

2007-01-01

420

Regulating autologous adult stem cells: the FDA steps up.  

PubMed

The Food and Drug Administration (FDA) has sought an injunction to prevent a US-based company from offering an autologous adult stem cell treatment for musculoskeletal and spinal injuries. Given the alarming number of clinics promoting stem-cell-based interventions, the outcome of this case could have wide-ranging implications. PMID:22056136

Lysaght, Tamra; Campbell, Alastair V

2011-11-01

421

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

2008-01-01

422

Nitric Oxide Is a Regulator of Hematopoietic Stem Cell Activity  

Microsoft Academic Search

Hematopoietic stem cells give rise to various multipotent progenitor populations, which expand in response to cytokines and which ultimately generate all of the elements of the blood. Here we show that it is possible to increase the number of stem and progenitor cells in the bone marrow (BM) by suppressing the activity of NO synthases (NOS). Exposure of mice to

Tatyana Michurina; Peter Krasnov; Alejandro Balazs; Naoki Nakaya; Tamara Vasilieva; Boris Kuzin; Nikolay Khrushchov; Richard C. Mulligan; Grigori Enikolopov

2004-01-01

423

Leaf Decomposition in a Tropical Rainforest Stream.  

National Technical Information Service (NTIS)

Fungi play an important part in leaf litter decomposition in terrestrial ecosystems in both temperate and tropical regions. There are few published reports dealing with decomposition in running waters, and no work has been done in tropical streams. Result...

D. E. Padgett

1975-01-01

424

Monitoring Air Quality with Leaf Yeasts.  

ERIC Educational Resources Information Center

|Proposes that leaf yeast serve as quick, inexpensive, and effective techniques for monitoring air quality. Outlines procedures and provides suggestions for data analysis. Includes results from sample school groups who employed this technique. (ML)|

Richardson, D. H. S.; And Others

1985-01-01

425

Guava leaf extract and topical haemostasis.  

PubMed

The effects of guava leaf extract on the bleeding time and the three main mechanisms of haemostasis: vasoconstriction, platelet aggregation and blood coagulation, were investigated. The water extract of guava leaves did not shorten bleeding times in rats. Guava leaf extract potentiated the vascular muscle contraction induced in rabbits by phenylephrine, and when given alone it stimulated human platelet aggregation in vitro in a dose-dependent manner. On the other hand, it significantly prolonged blood coagulation; activated partial thromboplastin time (APTT) test (p < 0.05). The higher the concentration of the extract, the longer APTT was observed. Thus, a water extract of guava leaves showed ambiguous effects on the haemostatic system. Guava leaf extract did not affect bleeding times, it stimulated vasoconstriction and platelet aggregation but it inhibited blood coagulation. Therefore, guava leaf extract is not recommended as a haemostatic agent. PMID:10925412

Jaiarj, P; Wongkrajang, Y; Thongpraditchote, S; Peungvicha, P; Bunyapraphatsara, N; Opartkiattikul, N

2000-08-01

426

Photosynthesis and Respiration in Leaf Slices.  

ERIC Educational Resources Information Center

|Demonstrates how leaf slices provide an inexpensive material for illustrating several fundamental points about the biochemistry of photosynthesis and respiration. Presents experiments that illustrate the effects of photon flux density and herbicides and carbon dioxide concentration. (DDR)|

Brown, Simon

1998-01-01

427

An Exploration of Distributed Leaf Wetness and Dew Detection Using Inexpensive Radios  

NASA Astrophysics Data System (ADS)

Our understanding of latent heat transfer between the soil surface and canopy is not complete. A major contributing factor to the uncertainty is the presence and amount of dew on the plant canopy. Improved measurements of dew duration, and possibly amount would help refine land surface process models. There are automated leaf wetness sensors available that consist of a simple sensor that attempts to simulate a single leaf. The electrical resistivity of the sensor is a function of the amount of liquid water that has condensed on its surface. These sensors generally provide reliable dew/no dew indication, but do not provide good information on dew amount. It may be possible to obtain dew amount from such sensors, but that would require careful calibration, because of the nonlinear relationship between dew amount and resistivity. The alternative is traditional measurements that require manually sampling and measuring dew amount. This latter is time-consuming and labor-intensive. Further, all these methods are point measurements that suffer from sampling errors. We are exploring the use of very inexpensive radios that operate in the unlicensed industrial, scientific, and medical (ISM) band as leaf wetness sensors. Our hypothesis is that dew on plant leafs attenuates the radio signals, and by recording the received signal strength, one can detect changes in leaf wetness. Further, such measurements are distributed/volume measurements that counter sampling errors inherent in point measurements. By using directional antennas, there is the exciting possibility to perform tomographic dew measurements. To test our hypothesis, we have deployed a number of radios operating at 2.4 GHz and 900 MHz, collocated with traditional leaf-wetness sensors in a corn field near Ames, Iowa. We have also made a large number of traditional leaf wetness/dew amount measurements at this location. Preliminary data analysis for the radio-based technique is promising. In this work, we present and discuss the data, along with comparison with output from a land surface process model.

Niemeier, J. J.; Rowlandson, T. L.; Kruger, A.; Hornbuckle, B. K.

2009-12-01

428

Stem water transport and freeze-thaw xylem embolism in conifers and angiosperms in a Tasmanian treeline heath  

Microsoft Academic Search

The effect of freezing on stem xylem hydraulic conductivity and leaf chlorophyll a fluorescence was measured in 12 tree and shrub species from a treeline heath in Tasmania, Australia. Reduction in stem hydraulic conductivity after a single freeze-thaw cycle was minimal in conifers and the vessel-less angiosperm species Tasmannia lanceolata (Winteraceae), whereas mean loss of conductivity in vessel-forming angiosperms fell

Taylor S. Feild; Tim Brodribb

2001-01-01

429

Leaf Senescence: Gene Expression and Regulation  

Microsoft Academic Search

\\u000a Each autumn leaf senescence leaves its mark on the planet in the form of dramatic changes in color that can be seen from space.\\u000a Annually, leaf senescence mediates the breakdown of 300 million tons of chlorophyll while changing green forests and fields\\u000a to yellow and orange (1). The drama of these color changes is matched by the dramatic nature of

Louis M. Weaver; Edward Himelblau; Richard M. Amasino

430

Leaf Impressions: A Model for Carbonization  

NSDL National Science Digital Library

In this activity students make leaf impressions on paper to illustrate how carbonization works. They use the leaf press method to demonstrate staining as a model for carbonization, when living tissue leaves a carbon film in sediment and rock. The students will discover that many plant fossils are preserved through carbonization and that soft parts of animals including skin and fur have also been preserved as fossils through the process of carbonization.

Greb, Stephen

431

Somatic embryogenesis from leaf cultures of potato  

Microsoft Academic Search

An efficient procedure has been developed for inducing somatic embryogenesis from leaf cultures of potato cv. Jyothi. Leaf sections were initially cultured on 2,4-dichlorophenoxyacetic acid (2,4-D) + benzyladenine (BA) and a-naphthaleneacetic acid (NAA) + BA supplemented Murashige and Skoog (MS) media. Nodular embryogenic callus developed from the cut ends of explants on media containing 2,4-D and BA, whereas compact callus

T. JayaSree; U. Pavan; M. Ramesh; A. V. Rao; K. Jagan Mohan Reddy; A. Sadanandam

2001-01-01

432

Diel Variations Of Leaf Water Oxygen Isotope Ratios In Tropical Forest And Pasture Vegetation Of The Amazon Are Consistent With Non-Steady-State-Model Predictions  

NASA Astrophysics Data System (ADS)

We evaluated diel variations in the 2H and 18O of leaf and source water for vegetation within a primary forest and a pasture in eastern Brazilian Amazonia. During both the dry and wet seasons of 2004, we collected leaf water, stem water, and atmospheric water every 1-2 hours during 3-day intensive field campaigns. Leaf water isotope enrichment for upper canopy trees and lianas in the rainforest showed a significant fit to a non-steady state transient model developed by Cernuzack et al. (2002). The adequate fitting of measured data to the model contrasted with isotope values predicted by a steady-state Craig-Gordon model particularly for early morning and evening time periods. These filed observations suggest a longer leaf-water isotopic equilibration period for tropical vegetation than has previously been considered. In contrast, leaf water isotope ratios of C4 pasture grasses showed a strong fit with the steady state model, suggesting that time lags were much reduced in this vegetation type. Diurnal fluctuations in the oxygen isotope ratio of leaf water in rainforest vegetation during the dry season varied from 0‰ to +16‰ and -6‰ to +28‰, for oxygen and hydrogen isotopes, respectively. Isotopic enrichment of leaf water in grasses during the same period was greater. The hydrogen and oxygen isotope ratio variations during the wet season were greatly reduced when compared to dry season patterns. These applications of these observations to partitioning carbon dioxide fluxes in both vegetation types are discussed.

Ometto, J. P.; Ehleringer, J. R.; Martinelli, L. A.; Berry, J.; Lai, C.

2005-12-01

433

Stem cells on the way to restorative medicine.  

PubMed

Stem cells are defined by their unique properties of self-renewal and multilineage differentiation. Several decades ago, cells with such developmental plasticity have been identified in the embryo and in the bone marrow of the adult; in other organs, such cells could not be demonstrated. Here, recent findings are briefly summarized indicating that the elementary stem cell capabilities are retained by a limited number of cells present in many organs of the adult. Other data suggest that, on response to another microenvironment, "organ-specific" stem cells are able to acquire different fates. If confirmed these findings will have considerable impact on the future of clinical stem cell therapy. PMID:12057849

Keller, Robert

2002-08-01

434

Performance of stem flow gauges in greenhouse and desert environments  

SciTech Connect

This study was conducted to evaluate the accuracy and general performance of a heat balance method for estimating transpirational sap flow through plant stems on two tree species in greenhouse and field experiments in Tucson, Arizona. Sap flow through 20-mm diameter stems of oak (Quercus virginiana `Heritage`) and mesquite (Prosopis alba `Colorado`.) trees in containers was measured using stem flow gauges and a precision balance, from January to October, 1991. Overall gauge accuracy, and the effects of gauge location on the tree stem, gauge ventilation, gauge insulation, sheath conductance factor (Ksh) selection method, and increased numbers of vertical thermocouple pairs on gauge performance were evaluated.

Levitt, D.G. [Reynolds Electrical and Engineering Co., Inc., Las Vegas, NV (United States); Simpson, J.R. [California Univ., Davis, CA (United States). Dept. of Environmental Horticulture; Tipton, J.L. [Arizona Univ., Tucson, AZ (United States). Dept. of Plant Sciences

1995-06-01

435

Brain tumour stem cells: the undercurrents of human brain cancer and their relationship to neural stem cells  

Microsoft Academic Search

Conceptual and technical advances in neural stem cell biology are being applied to the study of human brain tumours. These studies suggest that human brain tumours are organized as a hierarchy and are maintained by a small number of tumour cells that have stem cell properties. Most of the bulk population of human brain tumours comprise cells that have lost

Peter B. Dirks

2008-01-01

436

Relationship between hydraulic resistance and leaf morphology in broadleaf Quercus species: a new interpretation of leaf lobation  

Microsoft Academic Search

We investigated the relationship between leaf shape and leaf hydraulic resistance in a set of broadleaf Quercus tree species (Q. cerris, Q. frainetto, Q. petraea, Q. pyrenaica, Q. robur, Q. rubra, Q. velutina). Seedlings of all the studied species were grown under uniform environmental conditions. A new high-pressure flowmeter was designed to measure leaf-blade hydraulic resistance. Leaf shape was characterised

S. Sisó; J. J. Camarero; Eustaquio Gil-Pelegrín

2001-01-01

437

Leaf morphology shift linked to climate change  

PubMed Central

Climate change is driving adaptive shifts within species, but research on plants has been focused on phenology. Leaf morphology has demonstrated links with climate and varies within species along climate gradients. We predicted that, given within-species variation along a climate gradient, a morphological shift should have occurred over time due to climate change. We tested this prediction, taking advantage of latitudinal and altitudinal variations within the Adelaide Geosyncline region, South Australia, historical herbarium specimens (n = 255) and field sampling (n = 274). Leaf width in the study taxon, Dodonaea viscosa subsp. angustissima, was negatively correlated with latitude regionally, and leaf area was negatively correlated with altitude locally. Analysis of herbarium specimens revealed a 2 mm decrease in leaf width (total range 1–9 mm) over 127 years across the region. The results are consistent with a morphological response to contemporary climate change. We conclude that leaf width is linked to maximum temperature regionally (latitude gradient) and leaf area to minimum temperature locally (altitude gradient). These data indicate a morphological shift consistent with a direct response to climate change and could inform provenance selection for restoration with further investigation of the genetic basis and adaptive significance of observed variation.

Guerin, Greg R.; Wen, Haixia; Lowe, Andrew J.

2012-01-01

438

Chemistry and Biology of Plant Leaf Movements.  

PubMed

The leaves of Mimosa pudica L. are well known for their rapid movement when touched. Recently, we were able to isolate an excitatory substance in small quantities from this plant, which consists of three different components (potassium L-malate, magnesium trans-aconitate, and dimethylammonium salt). Many plants close their leaves in the evening, as if to sleep, and open them early in the morning (nyctinastic leaf movement). This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-opening substances (LOSs) and leaf-closing substances (LCSs). Based on our experiments on these bioactive substances, we found that the circadian rhythmic leaf movement of these plants is initiated by the regulated balance of LOSs and LCSs. The balance of concentration between the two leaf-movement factors (LMFs) is inversed during the day. The glycoside-type LMF is hydrolyzed with beta-glucosidase, the activity of which is regulated by the biological clock. The circadian rhythm observed in the leaf movement is introduced by activation of beta-glucosidase regulated by the biological clock. PMID:10777626

Ueda; Yamamura

2000-04-01

439

Endophytic and epiphytic phyllosphere fungi of Camellia japonica: seasonal and leaf age-dependent variations.  

PubMed

Seasonal and leaf age-dependent variations in the endophytic and epiphytic phyllosphere fungal assemblages of Camellia japonica were examined and compared. Live leaves of C. japonica were collected in four seasons (May, Aug, Nov, Feb), and fungi were isolated from healthy-looking leaves of 0, 1, 2 and 3 y old. The infection rate and total number of endophytic fungi increased May-Feb, and species richness of endophytes increased as leaves aged. In contrast the infection rate of epiphytic fungi was 100% for all leaf ages at every sampling date. The total number of epiphytic fungi isolated was greatest in May and lowest in Aug. The species richness of epiphytes did not differ significantly by season or leaf age. Eight fungal species were recorded as major phyllosphere fungi of C. japonica. Seasonal variations were detected for the frequencies of Colletotrichum gloeosporioides, C. acutatum, and epiphytes Pestalotiopsis sp.1, Aureobasidium pullulans, Phoma sp.1 and Ramichloridium sp., whereas the frequency of the endophyte Geniculosporium sp.1 varied with leaf age. The frequency of the epiphyte Cladosporium cladosporioides varied with both season and leaf age. PMID:18751546

Osono, Takashi

440

Stem Cell Transplants  

NSDL National Science Digital Library

Transplanting embryonic stem cells from embryo into adult as a means of rejuvenating diseased cells, tissues, and organs poses ethical and moral challenges. In recent years, stem cell-derived nerve and glandular tissue has been transplanted into the brains and pancreas of Parkinson's disease and diabetes patients, respectively, with mixed results. This chapter provides background information on stem cell research, the future treatment of Parkins