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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

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

ERIC Educational Resources Information Center

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

Pascale, Pietro J.; Smith, Joseph

1986-01-01

3

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

4

Ginseng leaf-stem: bioactive constituents and pharmacological functions  

PubMed Central

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 extract contains numerous active ingredients, such as ginsenosides, polysaccharides, triterpenoids, flavonoids, volatile oils, polyacetylenic alcohols, peptides, amino acids and fatty acids. The extract contains larger amounts of the same active ingredients than the root. These active ingredients produce multifaceted pharmacological effects on the central nervous system, as well as on the cardiovascular, reproductive and metabolic systems. Ginseng leaf-stem extract also has anti-fatigue, anti-hyperglycemic, anti-obesity, anti-cancer, anti-oxidant and anti-aging properties. In normal use, ginseng leaf-stem extract is quite safe; adverse effects occur only when it is over dosed or is of poor quality. Extracts from ginseng root and leaf-stem have similar multifaceted pharmacological activities (for example central nervous and cardiovascular systems). In terms of costs and source availability, however, ginseng leaf-stem has advantages over its root. Further research will facilitate a wider use of ginseng leaf-stem. PMID:19849852

Wang, Hongwei; Peng, Dacheng; Xie, Jingtian

2009-01-01

5

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

PubMed Central

Background Biomass recalcitrance is affected by a number of chemical, physical and biological factors. In this study we looked into the differences in recalcitrance between two major anatomical fractions of wheat straw biomass, leaf and stem. A set of twenty-one wheat cultivars was fractionated and illustrated the substantial variation in leaf-to-stem ratio between cultivars. The two fractions were compared in terms of chemical composition, enzymatic convertibility, cellulose crystallinity and glucan accessibility. The use of water as a probe for assessing glucan accessibility was explored using low field nuclear magnetic resonance and infrared spectroscopy in combination with hydrogen-deuterium exchange. Results Leaves were clearly more degradable by lignocellulolytic enzymes than stems, and it was demonstrated that xylose removal was more linked to glucose yield for stems than for leaves. Comparing the locations of water in leaf and stem by low field NMR and FT-IR revealed that the glucan hydroxyl groups in leaves were more accessible to water than glucan hydroxyl groups in stems. No difference in crystallinity between leaf and stem was observed using wide angle x-ray diffraction. Hydrothermal pretreatment increased the accessibility towards water in stems but not in leaves. The results in this study indicate a correlation between the accessibility of glucan to water and to enzymes. Conclusions Enzymatic degradability of wheat straw anatomical fractions can be indicated by the accessibility of the hydroxyl groups to water. This suggests that water may be used to assess glucan accessibility in biomass samples. PMID:24860617

2014-01-01

6

Leaf number, water stress and carbon nutrition effects on poplar leaf growth  

E-print Network

Leaf number, water stress and carbon nutrition effects on poplar leaf growth J.P. Gaudillère area of a leaf is described by the number and the mean size of epidermal cells. Water stress, nitrogen at different levels in the process of leaf production. The main susceptible physio- logical mechanisms are cell

Paris-Sud XI, Université de

7

Genetics of resistance to wheat leaf rust, stem rust, and powdery mildew in Aegilops sharonensis.  

PubMed

Aegilops sharonensis (Sharon goatgrass) is a wild relative of wheat and a rich source of genetic diversity for disease resistance. The objectives of this study were to determine the genetic basis of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis and also the allelic relationships between genes controlling resistance to each disease. Progeny from crosses between resistant and susceptible accessions were evaluated for their disease reaction at the seedling and/or adult plant stage to determine the number and action of genes conferring resistance. Two different genes conferring resistance to leaf rust races THBJ and BBBB were identified in accessions 1644 and 603. For stem rust, the same single gene was found to confer resistance to race TTTT in accessions 1644 and 2229. Resistance to stem rust race TPMK was conferred by two genes in accessions 1644 and 603. A contingency test revealed no association between genes conferring resistance to leaf rust race THBJ and stem rust race TTTT or between genes conferring resistance to stem rust race TTTT and powdery mildew isolate UM06-01, indicating that the respective resistance genes are not linked. Three accessions (1644, 2229, and 1193) were found to carry a single gene for resistance to powdery mildew. Allelism tests revealed that the resistance gene in accession 1644 is different from the respective single genes present in either 2229 or 1193. The simple inheritance of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis should simplify the transfer of resistance to wheat in wide crosses. PMID:18944087

Olivera, P D; Millet, E; Anikster, Y; Steffenson, B J

2008-03-01

8

Leaf Petiole and Stem Blight Disease of Sweet Potato Caused by Alternaria Bataticola in Uganda  

Technology Transfer Automated Retrieval System (TEKTRAN)

Alternaria leaf petiole and stem blight is an important disease of sweet potato (Ipomoea batatus (L.) Lam.) in tropical and sub-tropical regions. In surveys conducted in Uganda from 2001 to 2003, disease incidence ranged from 0-49%. Symptoms of Alternaria leaf and stem blight disease consisted of sm...

9

Bacterial leaf and stem blight of safflower in M. Afazal AKHTAR M. Siddique MIRZA M. ASLAM  

E-print Network

NOTE Bacterial leaf and stem blight of safflower in Pakistan M. Afazal AKHTAR M. Siddique MIRZA M SUMMARY Bacterial leaf and stem blight disease on safflower (Carthamus tinctorus L.) was detected in 1985 to be the first identification of this bacterium on safflower from Pakistan. Additional key words : Pseudomonas

Boyer, Edmond

10

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

Microsoft Academic Search

Metal contents of decomposing leaf blades, leaf sheaths and stems of common reed (Phragmites australis) were monitored by a litter bag method on the sediment of an intertidal brackish marsh in the Scheldt estuary (The Netherlands). On monthly intervals, two litter bags were retrieved from the marsh during 9 months for both leaf blades and sheaths and during 16 months

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

2006-01-01

11

Formation of shoots from leaf axils of Alstroemeria: The effect of the position on the stem  

Microsoft Academic Search

Direct shoot regeneration was induced from leaf explants of Alstroemeria. The explants contained a leaf blade and a small\\u000a portion of stem node, which were cut from the erect shoots of in vitro multiplicated plantlets. The shoot regeneration capacity\\u000a of the excised leaf explants was significantly related to the position of the explant on the stem. The youngest explant which

Hsueh-Shih Lin; Marjo J. De Jeu; Evert Jacobsen

1998-01-01

12

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

PubMed Central

In 2010, symptoms of leaf and stem rot were observed on potted plants (Peperomia quadrangularis) in a greenhouse in Yongin, Korea. The causative pathogen was identified as Myrothecium roridum based on morphological data, internal transcribed spacer sequence analysis, and pathogenicity test. To our knowledge, this is the first report of M. roridum causing leaf and stem rot disease on P. quadrangularis in Korea and elsewhere worldwide. PMID:25071393

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

2014-01-01

13

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...

14

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

PubMed Central

The aim of the present study was to observe the curative effect of traditional Chinese cajan leaves, combined with administration of bone marrow-derived mesenchymal stem cells (BMSCs), on osteonecrosis of the femoral head (ONFH) in rats and to investigate the underlying mechanisms. A total of 40 rat ONFH models were established through liquid nitrogen freezing and were subsequently divided into groups: A, control; B, treated with cajan leaf; C, treated with BMSCs and D, treated with cajan leaf combined with BMSCs. Samples were obtained 30 days following treatment, and immunohistochemical staining of vascular endothelial growth factor (VEGF) and image analysis were performed. Chondrocytes and vascular endothelial cells were stained as a result of immunohistochemical staining and group D exhibited markedly deeper staining, and a significantly larger number of stained cells, compared with group A. Thus, in the present study, cajan leaf combined with BMSCs was shown to promote VEGF expression and improve ONFH repair. PMID:24926328

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

2014-01-01

15

Wheat leaf and stem rust in the United States  

Microsoft Academic Search

Leaf rust, caused by Puccinia triticina, is a common and widespread disease of wheat in the US. On an annual basis, over 50 races of the leaf rust fungus are detected. There are at least 5 major groups of genetically distinct P. triticina isolates in the US based on allelic variation at microsatellite loci. Distinct regional race populations of P.

J. A. KolmerA; Y. Jin; D. L. LongA

2007-01-01

16

Sorghum mutant RG displays antithetic leaf shoot lignin accumulation resulting in improved stem saccharification properties  

PubMed Central

Background Improving saccharification efficiency in bioenergy crop species remains an important challenge. Here, we report the characterization of a Sorghum (Sorghum bicolor L.) mutant, named REDforGREEN (RG), as a bioenergy feedstock. Results It was found that RG displayed increased accumulation of lignin in leaves and depletion in the stems, antithetic to the trend observed in wild type. Consistent with these measurements, the RG leaf tissue displayed reduced saccharification efficiency whereas the stem saccharification efficiency increased relative to wild type. Reduced lignin was linked to improved saccharification in RG stems, but a chemical shift to greater S:G ratios in RG stem lignin was also observed. Similarities in cellulose content and structure by XRD-analysis support the correlation between increased saccharification properties and reduced lignin instead of changes in the cellulose composition and/or structure. Conclusion Antithetic lignin accumulation was observed in the RG mutant leaf-and stem-tissue, which resulted in greater saccharification efficiency in the RG stem and differential thermochemical product yield in high lignin leaves. Thus, the red leaf coloration of the RG mutant represents a potential marker for improved conversion of stem cellulose to fermentable sugars in the C4 grass Sorghum. PMID:24103129

2013-01-01

17

Antibacterial activity of stem and leaf extract of Kedrostis foetidissima (Jacq.) Cogn.  

PubMed Central

The present study aimed at evaluating the antimicrobial activity of chloroform extracts of stem and leaf of Kedrostis foetidissima (jacq.) cogn. (Cucurbitaceae) against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens and Klebsiella pneumoniae. was carried out using agar disc diffusion technique. The results revealed that the chloroform extract of stem presented the highest zone of inhibition against Pseudomonas aeruginosa others show significant zone of inhibition. PMID:22557304

Priyavardhini, S.; Gowri, S. Shyamala; Vasantha, K.; Umadevi, M.

2008-01-01

18

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

19

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

20

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

PubMed Central

Background The present study was carried out to assess the phytochemical and anti-dermatophytic effect of the leaf and bark extracts of Xylosma longifolium Clos. The leaf and stem bark are used by the indigenous people of Manipur, India for treatment of skin diseases. Methods The leaves and stem barks of Xylosma longifolium were extracted using petroleum ether, chloroform and methanol respectively. The different extracts of each plant parts were tested for antioxidant activity using DPPH assay. The phenolic content was assayed using Folin-Ciocalteu colorimetric method. Each extracts was further analysed by RP-HPLC to quantify some individual flavonoid components. The anti-dermatophytic activity was evaluated both by agar diffusion method and micro wells dilution method against the Microsporum boullardii MTCC 6059, M. canis (MTCC 2820 and MTCC 32700), M. gypseum MTCC 2819, Trichophyton ajelloi MTCC 4878, T. rubrum (MTCC 296 and MTCC 3272). Results The free radical scavenging activity values were ranged from 0.7 to 1.41 mg/ml and 0.6 to 1.23 mg/ml, respectively for leaf and stem bark extracts. The amount of total phenolic contents of the extracts occurred in both leaf and bark in the range of 12 to 56.6 mg GAE/100 g and 16 to 58 mg GAE/100 g respectively. RP-HPLC analysis for flavonoids revealed the presence of two major flavonoid compounds, rutin and catechin. Kaempferol was in trace or absent. Methanol leaf extract showed significant low inhibitory effect against tested fungus Trichophyton ajelloi MTCC 4878 (0.140625 mg/ml) as the most sensitive. These finding suggest that the methanol leaf extract tested contain compounds with antimicrobial properties. Conclusion The results of our study may partially justify the folkloric uses on the plant studied and further provide an evidence that the leaf extract of Xylosma longifolium might be indeed a potential sources of antimicrobial agents. PMID:23819459

2013-01-01

21

In vitro evaluation of cytotoxic activity of flower, leaf, stem and root extracts of five Artemisia species  

PubMed Central

The present study was carried out to investigate cytotoxic activity of flower, leaf, stem and root extracts of five Artemisia species against breast cancer cell line (MCF7) and human embryonic kidney normal cell line (HEK293). The studied Artemisia species were A. absinthium, A. vulgaris, A. incana, A. fragrans and A. spicigera. The cytotoxic activity was measured by MTT assay at different concentrations (62.5, 125, 250, 500 ?g/ml). Among these five species, methanol extracts of flower, leaf, stem and root of A. absinthium and A. vulgaris exhibited considerable cytotoxic activity. The flower extracts of these two species were found to have higher cytotoxic effect on MCF7 cell with an IC50 value of 221.5 and >500 ?g/ml, respectively. Leaf methanol extract of A. incana also showed cytotoxic activity. Cytotoxic activity of different extracts of A. absinthium, A. vulgaris and A. incana against MCF7 was 10%-40% more than HEK293 cells. Not only the extracts of A. spicigera and A. fragrans did not show any cytotoxic effect against both cell lines, but also increased the number of cells. This study revealed that A. absinthium and A. vulgaris may have a great potential to explore new anticancer drugs.

Gordanian, B.; Behbahani, M.; Carapetian, J.; Fazilati, M.

2014-01-01

22

Changes in Clonal Poplar Leaf Chemistry Caused by Stem Galls Alter Herbivory and Leaf Litter Decomposition  

PubMed Central

Gall-inducing insects are highly specialized herbivores that modify the phenotype of their host plants. Beyond the direct manipulation of plant morphology and physiology in the immediate environment of the gall, there is also evidence of plant-mediated effects of gall-inducing insects on other species of the assemblages and ecosystem processes associated with the host plant. We analysed the impact of gall infestation by the aphid Pemphigus spirothecae on chemical leaf traits of clonal Lombardy poplars (Populus nigra var. italica) and the subsequent effects on intensity of herbivory and decomposition of leaves across five sites. We measured the herbivory of two feeding guilds: leaf-chewing insects that feed on the blade (e.g. caterpillars and sawfly larvae) and skeletonising insects that feed on the mesophyll of the leaves (e.g. larvae of beetles). Galled leaves had higher phenol (35%) and lower nitrogen and cholorophyll contents (35% respectively 37%) than non-galled leaves, and these differences were stronger in August than in June. Total herbivory intensity was 27% higher on galled than on non-galled leaves; damage by leaf chewers was on average 61% higher on gall infested leaves, whereas damage by skeletonising insects was on average 39% higher on non-galled leaves. After nine months the decomposition rate of galled leaf litter was 15% lower than that of non-galled leaf litter presumably because of the lower nitrogen content of the galled leaf litter. This indicated after-life effects of gall infestation on the decomposers. We found no evidence for galling x environment interactions. PMID:24260333

Knkler, Nora; Brandl, Roland; Brndle, Martin

2013-01-01

23

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

24

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

PubMed Central

Objective: Labisia pumila var. alata, commonly known as Kacip Fatimah or Selusuh Fatimah in Southeast Asia, is traditionally used by members of the Malay community because of its post-partum medicinal properties. Its various pharmaceutical applications cause an excessive harvesting and lead to serious shortage in natural habitat. Thus, this in vitro propagation study investigated the effects of different plant growth regulators (PGRs) on in vitro leaf and stem explants of L. pumila. Methods: The capabilities of callus, shoot, and root formation were evaluated by culturing both explants on Murashige and Skoog (MS) medium supplemented with various PGRs at the concentrations of 0, 1, 3, 5, and 7 mg/L. Results: Medium supplemented with 3 mg/L indole-3-butyric acid (IBA) showed the optimal callogenesis from both leaf and stem explants with (72.3419.55)% and (70.4014.14)% efficacy, respectively. IBA was also found to be the most efficient PGR for root induction. A total of (50.007.07)% and (77.7816.47)% of root formation were obtained from the in vitro stem and leaf explants after being cultured for (26.55.0) and (30.08.5) d in the medium supplemented with 1 and 3 mg/L of IBA, respectively. Shoot formation was only observed in stem explant, with the maximum percentage of formation ((100.000.00)%) that was obtained in 1 mg/L zeatin after (11.02.8) d of culture. Conclusions: Callus, roots, and shoots can be induced from in vitro leaf and stem explants of L. pumila through the manipulation of types and concentrations of PGRs. PMID:23825148

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

2013-01-01

25

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

PubMed

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

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

2012-02-01

26

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

27

Changes in leaf, stem, and root anatomy of Chrysanthemum cv. Lillian Hoek following paclobutrazol application  

Microsoft Academic Search

Plants ofChrysanthemum cv. Lillian Hoek were treated with a paclobutrazol (PBZ) soil drench and histologically examined after 3 months. PBZ application\\u000a resulted in thicker leaves, reduced stem diameter, and roots with an increased diameter and an unusual segmented appearance.\\u000a Increased leaf thickness was partly due to an additional layer of palisade mesophyll, although individual palisade cells were\\u000a shorter, of smaller

G. E. Burrows; T. S. Boag; W. P. Stewart

1992-01-01

28

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

29

Essential Oil Gland Number and Ultrastructure During Mentha arvensis Leaf Ontogeny  

Microsoft Academic Search

Alterations in essential oil gland number, distribution and fine structure, and the oil content in the leaf of Mentha arvensis\\u000a L. were examined during its growth and senescence. Accumulation of essential oil occurred predominantly during the rapid leaf\\u000a expansion phase followed by a similar decline. The oil gland (trichome) number increased upto leaf maturation and declined\\u000a thereafter. Initially, cuticle remains

S. Shanker; P. V. Ajayakumar; Sangwan; S. Kumar; R. S. Sangwan

1999-01-01

30

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 Initiative,

Business-Higher Education Forum (NJ1), 2010

2010-01-01

31

Scutellaria baicalensis stem-leaf total flavonoid reduces neuronal apoptosis induced by amyloid beta-peptide (2535)?  

PubMed Central

Scutellaria baicalensis stem-leaf total flavonoid might attenuate learning/memory impairment and neuronal loss in rats induced by amyloid beta-peptide. This study aimed to explore the effects of Scutellaria baicalensis stem-leaf total flavonoid on amyloid beta-peptide-induced neuronal apoptosis and the expression of apoptosis-related proteins in the rat hippocampus. Male Wistar rats were given intragastric administration of Scutellaria baicalensis stem-leaf total flavonoid, 50 or 100 mg/kg, once per day. On day 8 after administration, 10 ?g amyloid beta-peptide (2535) was injected into the bilateral hippocampus of rats to induce neuronal apoptosis. On day 20, hippocampal tissue was harvested and probed with the terminal deoxyribonucleotidyl transferase-mediated biotin-16-dUTP nick-end labeling assay. Scutellaria baicalensis stem-leaf total flavonoid at 50 and 100 mg/kg reduced neuronal apoptosis induced by amyloid beta-peptide (2535) in the rat hippocampus. Immunohistochemistry and western blot assay revealed that expression of the pro-apoptotic protein Bax, cytochrome c and caspase-3 was significantly diminished by 50 and 100 mg/kg Scutellaria baicalensis stem-leaf total flavonoid, while expression of the anti-apoptotic protein Bcl-2 was increased. Moreover, 100 mg/kg Scutellaria baicalensis stem-leaf total flavonoid had a more dramatic effect than the lower dosage. These experimental findings indicate that Scutellaria baicalensis stem-leaf total flavonoid dose-dependently attenuates neuronal apoptosis induced by amyloid beta-peptide in the hippocampus, and it might mediate this by regulating the expression of Bax, cytochrome c, caspase-3 and Bcl-2. PMID:25206402

Wang, Ruiting; Shen, Xingbin; Xing, Enhong; Guan, Lihua; Xin, Lisheng

2013-01-01

32

Rapid hydraulic recovery in Eucalyptus pauciflora after drought: linkages between stem hydraulics and leaf gas exchange.  

PubMed

In woody plants, photosynthetic capacity is closely linked to rates at which the plant hydraulic system can supply water to the leaf surface. Drought-induced embolism can cause sharp declines in xylem hydraulic conductivity that coincide with stomatal closure and reduced photosynthesis. Recovery of photosynthetic capacity after drought is dependent on restored xylem function, although few data exist to elucidate this coordination. We examined the dynamics of leaf gas exchange and xylem function in Eucalyptus pauciflora seedlings exposed to a cycle of severe water stress and recovery after re-watering. Stomatal closure and leaf turgor loss occurred at water potentials that delayed the extensive spread of embolism through the stem xylem. Stem hydraulic conductance recovered to control levels within 6?h after re-watering despite a severe drought treatment, suggesting an active mechanism embolism repair. However, stomatal conductance did not recover after 10?d of re-watering, effecting tighter control of transpiration post drought. The dynamics of recovery suggest that a combination of hydraulic and non-hydraulic factors influenced stomatal behaviour post drought. PMID:23937187

Martorell, Sebasti; Diaz-Espejo, Antonio; Medrano, Hiplito; Ball, Marilyn C; Choat, Brendan

2014-03-01

33

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

2005-02-01

34

Effect of cytokinins on shoot regeneration from cotyledon and leaf segment of stem mustard ( Brassica juncea var. tsatsai )  

Microsoft Academic Search

Cotyledon and leaf segments of stem mustard (Brassica juncea var. tsatsai) were cultured on Murashige and Skoog medium supplemented with various concentrations of different cytokinins [6-benzyladenine (BA), N-(2-chloro-4-pyridyl)-n-phenylurea (CPPU), 6-furfurylaminopurine (KT) and thidiazuron (TDZ)] in combinations with different levels of ?-naphthalene acetic acid (NAA). The shoot regeneration frequency of cotyledon and leaf segment was dependent on the kinds and concentrations

De-Ping Guo; Zhu-Jun Zhu; Xiao-Xiang Hu; Si-Jun Zheng

2005-01-01

35

STEM CELLS AND DEVELOPMENT Volume 18, Number 2, 2009  

E-print Network

and are multipotent [2,3]. Moreover, in the future, there is great po- tential for using these cells in patient meniscus, requires that these multipotent cells be dif- ferentiated down a brocartilaginous lineage283 STEM CELLS AND DEVELOPMENT Volume 18, Number 2, 2009 © Mary Ann Liebert, Inc. DOI: 10.1089/scd

Athanasiou, Kyriacos

36

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

PubMed

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

do Rocio Duarte, Mrcia; Carvalho de Souza, Danielle

2014-08-01

37

Control of Leaf and Stem Growth in Light-grown Pea Seedlings by Two High Irradiance Responses 1  

PubMed Central

The control exerted by light on leaf and stem growth in light-grown Alaska pea seedlings was studied during the main photoperiod. Two high irradiance responses were observed. The action spectrum for one had a single sharp peak at 600 nanometers. The action spectrum for the other showed a broad peak between 440 and 470 nanometers. These two light responses must be activated simultaneously for any inhibition of stem growth or promotion of leaf growth. Both action spectra may be explained in terms of the high irradiance response of phytochrome. PMID:16660822

Elliott, William M.

1979-01-01

38

DETECTION OF APPLE CHLOROTIC LEAF SPOT VIRUS (ACLSV) AND APPLE STEM GROOVING VIRUS (ASGV) IN DIFFERENT TISSUES OF 'MUTSU' APPLE CULTIVAR TREES BY ELISA  

Microsoft Academic Search

The detection of Apple chlorotic leaf spot virus (ACLSV) and Apple stem grooving vi- rus (ASGV) by a modified-ELISA test was investigated. ACLSV was detected in breaking leaf buds, young leaves, flowers or phloem + periderm + cortex paren- chyma samples. ASGV was found only in breaking leaf buds samples from Budzi- szynek. ACLSV and ASGV were detected in different

E. Paduch-Cichal; K. Tomala

39

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

NSDL National Science Digital Library

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

Program, The W.

40

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

E-print Network

Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis Alexandria L. Pivovaroff1 , Lawren Sack2 and Louis S. Santiago1 1 2014 New Phytologist (2014) 203: 842­850 doi: 10.1111/nph.12850 Key words: chaparral, hydraulic

Sack, Lawren

41

The effect of leaf presence on the rooting of stem cutting of bitter melon and on changes in polyamine levels  

Technology Transfer Automated Retrieval System (TEKTRAN)

The study was conducted to investigate the optimal hormone treatment for rooting in bitter melon and the effect of defoliation on rooting and polyamine levels. Commercial preparation (diluted 1:10 and 1: 20) gave extensive rooting within five days after treatment. The presence of leaf with the stem ...

42

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

ERIC Educational Resources Information Center

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

Cooper, Linda L.; Shore, Felice S.

2008-01-01

43

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

PubMed

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 was characterized by high proportions of alpha-pinene, the main compound of monoterpene hydrocarbon class, with 58.05% for leaf and 17.53% for flower. Stem was rich in oxygenated monoterpenes, largely due to 1,8-cineole with 32.84%. The total phenol contents varied between different myrtle parts; leaf extract had higher total phenol content (33.67 mg GAE/g) than flower (15.70 mg GAE/g) and stem (11.11 mg GAE/g) extracts. Significant differences were also found in total tannin contents among different myrtle parts, representing 26.55 mg GAE/g in leaf, 11.95 mg GAE/g in flower, 3.33 mg GAE/g in stem. The highest contents of total flavonoids and condensed tannins were observed in stem (5.17 and 1.99 mg CE/g, respectively) and leaf (3 and 1.22 mg CE/g, respectively) extracts. The HPLC analysis indicated that the main phenolic class was hydrolysable tannins (gallotannins) in leaf (79.39%, 8.90 mg/g) and flower (60.00%, 3.50mg/g) while the stem was characterized by the predominance of flavonoid class (61.38%, 1.86 mg/g) due to the high presence of catechin (36.91%, 1.12 mg/g). Antioxidant activities of the essential oil and the methanolic extract from different myrtle parts were evaluated by using DPPH radical scavenging, beta-carotene-linoleic acid bleaching, reducing power and metal chelating activity assays. In all tests, methanolic extracts of different myrtle parts showed better antioxidant activity than essential oils. PMID:20211674

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

2010-05-01

44

The Effects of Hydroalcoholic Extract of Apium graveolens Leaf on the Number of Sexual Cells and Testicular Structure in Rat  

PubMed Central

Background: Use of medicinal plants with high antioxidant properties could be effective to increase fertility and improvement of disorders such as hormonal imbalance, impotency, oligospermia and immotile sperm. Celery (Apium graveolens) is rich in antioxidant agents. The leaf and stems of celery contain phenols, furanocoumarin and luteolin. Apigenin is one of the main flavonoids of celery leaf. Objectives: This study aimed to investigate the effects of hydroalcoholic extract of celery on histological properties of testis and number of sexual cells in male rats. Materials and Methods: Thirty-two male Wistar rats were divided into four groups of eight rats each. Control, did not receive any medication; sham, received normal saline; and two groups received celery extract orally in dosages of 100 and 200 mg/kg/BW once every two days for 60 days. At the end, animals were anesthetized, and caudal part of the right epididymis was used for sperm counting. After fixation of testis, tissue sections were prepared and studied microscopically to evaluate morphometric (lumen diameter, number of primary spermatocyte and sertoli cell) and histological changes. Data was analyzed by one-way ANOVA test using SPSS15 software. P < 0.05 was considered as statistically significant. Results: There was a significant increase in the number of sperms, sertoli cells, and primary spermatocyte (P < 0.05) in groups receiving extract; however, structural changes were not observed in the groups. Conclusions: It seems that celery increases spermatogenesis in male rats, but has no destructive effects on testicular tissue.

Kooti, Wesam; Mansouri, Esrafil; Ghasemiboroon, Maryam; Harizi, Mahmoud; Ashtary-Larky, Damoon; Afrisham, Reza

2014-01-01

45

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

2005-04-01

46

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 98C 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. PMID:24137234

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

2013-01-01

47

The acute and subchronic toxicity studies of aqueous leaf and stem bark extract of Costus afer ker (Zingiberaceae) in mice  

Microsoft Academic Search

This work investigated the acute and subchronic toxicity profile of aqeous stem bark and leaf extract of Costus afer ker (Zingiberaceae). This plant is used extensively for food, economic, and medicinal purposes in Nigeria. Acute oral toxicity\\u000a studies in male and female mice did not produce any sign of acute toxicity or death even at the dose of 4,000mg\\/kg. Thirty-six

Samuel Chukwuneke Udem; Chukwunonso K. Ezeasor

2010-01-01

48

Feasibility study: Alfalfa leaf meal as a value-added crop and alfalfa stems as biomass fuel. Final report  

SciTech Connect

The grantee recognizes the importance of alfalfa production to agricultural economics in the western United States. With this grant, it secured the assistance of experts at the University of Wyoming to explore alternative uses for and, thus, ways to add value to alfalfa. The study was prompted by periodic unstable demand and price fluctuations for hay. The agricultural infrastructure and expertise for producing alfalfa is well established in the Western U.S. Alfalfa is a well-adapted, environmentally friendly crop which avoids a large fertilizer subsidy by fixing atmospheric nitrogen into a form utilized for plant growth. Leaf-stem fractions were evaluated for forage quality, biofuel energy content, and co-product yield due to seperation procedure. The feasibility of conducting alfalfa leaf-stem separations in both stationary and mobile plants was considered on the basis of three factors: (1) price received for each fraction, (2) cost of the hay to be processed, and (3) cost of processing the hay. Both stationary and mobile separation plants showed positive net income potentials. Alfalfa stem pellets could be marked at appreciably lower cost than equivalent wood pellets for use in wood stoves. The report recommends that sufficient quantities of high-quality alfalfa leaf meal be produced and tested for evaluation in dairy, beef, aquaculture, poultry, and swine rations.

Gray, A.; Kaan, D.

1996-05-28

49

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

PubMed Central

This study was conducted to evaluate the sedative effects of Arachis hypogaea L. stem and leaf extract (AHSLE) and determine its effect pathways through ?-aminobutyric acid (GABA)-gated channels on male Sprague-Dawley rats treated with pentobarbital. AHSLE was obtained from 98C water (3 h, extracted twice). AHSLE and flumazenil (a GABA type A receptor antagonist) were administered to the rats orally, whereas pentobarbital sodium and muscimol (a GABA type A receptor agonist) were administered intraperitoneally (i.p.). The results demonstrated that AHSLE decreased sleep latency and increased sleep time in pentobarbital-treated rats (50 mg/kg, i.p.). The coadministration of AHSLE and muscimol (0.05 mg/kg) significantly increased sleep time and reduced sleep latency in pentobarbital-treated rats and these actions were significantly antagonized by flumazenil at a dose of 3.5 mg/kg. These results indicated that AHSLE improved the sleep behavior in pentobarbital-treated rats, possibly through GABA-gated channel-related mechanisms. PMID:24748980

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

2014-01-01

50

[Determination of myclobutanil 25% WG degradation dynamics in ginseng root, stem, leaf and soil by HPLC-MS/MS].  

PubMed

A high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method was developed for determining degradation dynamics and final residues of myclobutanil 25% WG in ginseng root, stem, leaf and soil. The samples were extracted with acetonitrile, cleaned-up with primary secondary amine (PSA) solid phase extraction cartridge, separated by Kromasil Eternity-5-C18 (2.1 mm x 150 mm, 5 microm) column with a gradient of acetonitrile and 0.1% formate in water as mobile phases, and analyzed with the multiple reaction monitoring (MRM) in positive ion mode by employing the external standard method. The average recoveries and the relative standard derivations (RSDs) of myclobutanil at the spiked level of 0.01-0.20 mg x kg(-1) were 80.9%-90.7% and 5.54%-9.29%, respectively, and the limit of quantification (LOQ) was 0.005 mg x kg(-1). The method with good reproducible, high precision and low detection limit could meet the requirements of residual analysis on ginseng production. The half-lives of myclobutanil were from 6.25 days to 9.94 days in ginseng root, stem, leaf and soil at spraying dosage of 1 152 g x hm(-2) The final residues were below 0.060 1 mg x kg(-1) in root, below 0.081 7 mg x kg(-1) in stem, 0.006 0-0.102 2 mg x kg(-1) in leaf and below 0.037 6 mg x kg(-1) in soil at spraying dosage range from 576 to 1 152 g x hm(-2). It is recommended that the MRLs of myclobutanil in dried ginseng may be suggested to be 0.10 mg x kg(-1) temporarily, and the preharvest interval was set at 35 days. PMID:25276964

Wang, Yan; Wang, Chun-Wei; Gao, Jie; Cui, Li-Li; Xu, Yun-Cheng

2014-07-01

51

Leaf Arrangement  

NSDL National Science Digital Library

This illustrated guide to leaf arrangement shows students how leaves attached at a stem node can be in alternate, opposite, or whorled arrangements. This single Web page can be easily printed for use at field sites.

52

Poly(ADP-Ribose)Polymerase Activity Controls Plant Growth by Promoting Leaf Cell Number  

PubMed Central

A changing global environment, rising population and increasing demand for biofuels are challenging agriculture and creating a need for technologies to increase biomass production. Here we demonstrate that the inhibition of poly (ADP-ribose) polymerase activity is a promising technology to achieve this under non-stress conditions. Furthermore, we investigate the basis of this growth enhancement via leaf series and kinematic cell analysis as well as single leaf transcriptomics and plant metabolomics under non-stress conditions. These data indicate a regulatory function of PARP within cell growth and potentially development. PARP inhibition enhances growth of Arabidopsis thaliana by enhancing the cell number. Time course single leaf transcriptomics shows that PARP inhibition regulates a small subset of genes which are related to growth promotion, cell cycle and the control of metabolism. This is supported by metabolite analysis showing overall changes in primary and particularly secondary metabolism. Taken together the results indicate a versatile function of PARP beyond its previously reported roles in controlling plant stress tolerance and thus can be a useful target for enhancing biomass production. PMID:24587323

Schulz, Philipp; Jansseune, Karel; Degenkolbe, Thomas; Mret, Michal; Claeys, Hannes; Skirycz, Aleksandra; Teige, Markus; Willmitzer, Lothar; Hannah, Matthew A.

2014-01-01

53

Downward vascular translocation of a green fluorescent protein-tagged strain of Dickeya sp. (Biovar 3) from stem and leaf inoculation sites on potato.  

PubMed

Translocation of a green fluorescent protein (GFP)-tagged Dickeya sp. from stems or from leaves to underground parts of potato plants was studied in greenhouse experiments. Thirty days after stem inoculation, 90% of plants expressed symptoms at the stem base and 95% of plants showed browning of internal stem tissue. The GFP-tagged Dickeya sp. was detected by dilution plating in extracts of the stem interiors (100%), stem bases (90%), roots (80%), stolons (55%), and progeny tubers (24%). In roots, the GFP-tagged Dickeya sp. was found inside and between parenchyma cells whereas, in stems and stolons, the GFP-tagged Dickeya sp. was found in the xylem vessels and protoxylem cells. In progeny tubers, this strain was detected in the stolon end. Thirty days after leaf inoculation, the GFP-tagged Dickeya sp. was detected in extracts of 75% of the leaves, 88% of the petioles, 63% of the axils, and inside 25% of the stems taken 15 cm above the ground level. UV microscopy confirmed the presence of the GFP-tagged Dickeya sp. inside petioles and in the main leaf veins. No blackleg or aerial stem rot and no translocation of the GFP-tagged Dickeya sp. to underground plant parts was observed. The implications for contamination of progeny tubers are discussed. PMID:20932162

Czajkowski, Robert; de Boer, Waldo J; van Veen, Johannes A; van der Wolf, Jan M

2010-11-01

54

Cauliflower Plant Organ Water Status and Nitrogen Translocation From LeafStem Sources to Head Sinks in Its Three Hybrid Cultivars  

Microsoft Academic Search

Cauliflower's (Brassica oleracea var. botrytis L.) fresh appearance and high nutritional values may be related to plant organ water holding and nitrogen (N) translocation from leafstem sources to head sinks. Cauliflower plant water and N nutrition relations were examined in a two-site field study in Nova Scotia. The objectives of this study were to assess cauliflower plant organ water and

Hong Li

2011-01-01

55

An Immunocapture RT-PCR Procedure Using Apple stem grooving virus Antibodies Facilitates Molecular Genetic Characterization of Citrus tatter leaf virus from the Original Meyer Lemon Host  

Technology Transfer Automated Retrieval System (TEKTRAN)

A magnetic bead-based immonocapture system using polyclonal antiserum against Apple stem grooving virus (ASGV) successfully facilitated polymerase chain reaction (PCR) amplification of sequences from three Citrus tatter leaf virus (CTLV) isolates originally isolated from the citrus host Meyer lemon....

56

Somatic embryogenesis from stem and leaf explants of Quercus robur L  

Microsoft Academic Search

Internodal and leaf segments from pedunculate oak (Quercus robur L.) seedlings were used as explant source to induce somatic embryogenesis. Auxin treatment influenced embryogenic response, which\\u000a only occurred in explants initially cultured on media containing 4 mg\\/l naphthaleneacetic acid (NAA) and different benzyladenine\\u000a (BA) concentrations. After 6 weeks of culture on induction medium, the explants were transferred to medium supplemented

B. Cuenca; M. T. Martnez; A. Ballester; A. M. Vieitez

1999-01-01

57

Leaf, stem and root tissue strategies across 758 Neotropical tree species  

E-print Network

2005). The shoot system is com- prised of leaves to capture light and CO2 as the primary photosynthetic Introduction Terrestrial plants are fixed organisms whose basic modular organization into shoot and root organs, and stems that support leaves, transport water and nutrients between the root and shoot systems

Fine, Paul V.A.

58

Effects of potato psyllid-vectored 'Candidatus Liberibacter solanacearum' infection on potato leaf and stem physiology.  

PubMed

The bacterium 'Candidatus Liberibacter solanacearum' (Lso) is associated with zebra chip (ZC) disease, a threat to potato production in North America and New Zealand. It is vectored by potato psyllids. Previous studies observed that Lso infection causes potato tubers to undergo ZC-symptom associated shifts in physiology, such as increased levels of amino acids, sugars, and phenolics. However, little is known about how Lso infections caused by psyllid vector feeding may affect metabolism in potato foliage and stems. This study compared metabolism in potatoes fed upon by Lso-positive psyllids with potato plants not exposed to psyllids. Foliar levels of asparagine, aspartic acid, glutamine, fructose, glucose, sucrose, a ferulic acid derivative, and quinic acid were lower in Lso-inoculated than non-infected plants. However, foliar levels of proline, serine, four phenolic compounds, and most terpenoids were greater in Lso-inoculated than non-infected plants. Upper stem levels of asparagine and aspartic acid, upper and lower stem levels of ellagitannins and most monoterpenoids, and lower stem level of sesquiterpenoids were greater in Lso-inoculated than non-infected plants. These results suggest that many defense-related terpenoid compounds might increase in plants which had psyllids inoculate Lso. This could impact progression and spread of ZC. PMID:25469656

Wallis, Christopher; Rashed, Arash; Chen, Jianchi; Paetzold, Li; Workneh, Fekede; Rush, Charles M

2014-12-01

59

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 (2.010.0 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

60

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

PubMed

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

Nobel, P S; Hartsock, T L

1986-04-01

61

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. PMID:16664741

Nobel, Park S.; Hartsock, Terry L.

1986-01-01

62

GENETIC CONTROL OF THE NUMBER OF NODES PER STEM IN MILLET (Panicum miliaceum L.)  

Microsoft Academic Search

The number of nodes per stem in millet has a special contribution to plant growth and development, being directly, positively and significantly correlated with the number of leaves and panicles per plant, TKW, green mass, grain and protein yield. The researches performed at Agricultural Research and Development Station Podu- Iloaiei pointed out an average variability for this trait. Hybridological analyses

Mihai Pricop

63

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

64

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

PubMed Central

Background MicroRNAs (miRNAs) are ubiquitous components of endogenous plant transcriptome. miRNAs are small, single-stranded and ~21 nt long RNAs which regulate gene expression at the post-transcriptional level and are known to play essential roles in various aspects of plant development and growth. Previously, a number of miRNAs have been identified in potato through in silico analysis and deep sequencing approach. However, identification of miRNAs through deep sequencing approach was limited to a few tissue types and developmental stages. This study reports the identification and characterization of potato miRNAs in three different vegetative tissues and four stages of tuber development by high throughput sequencing. Results Small RNA libraries were constructed from leaf, stem, root and four early developmental stages of tuberization and subjected to deep sequencing, followed by bioinformatics analysis. A total of 89 conserved miRNAs (belonging to 33 families), 147 potato-specific miRNAs (with star sequence) and 112 candidate potato-specific miRNAs (without star sequence) were identified. The digital expression profiling based on TPM (Transcripts Per Million) and qRT-PCR analysis of conserved and potato-specific miRNAs revealed that some of the miRNAs showed tissue specific expression (leaf, stem and root) while a few demonstrated tuberization stage-specific expressions. Targets were predicted for identified conserved and potato-specific miRNAs, and predicted targets of four conserved miRNAs, miR160, miR164, miR172 and miR171, which are ARF16 (Auxin Response Factor 16), NAM (NO APICAL MERISTEM), RAP1 (Relative to APETALA2 1) and HAM (HAIRY MERISTEM) respectively, were experimentally validated using 5? RLM-RACE (RNA ligase mediated rapid amplification of cDNA ends). Gene ontology (GO) analysis for potato-specific miRNAs was also performed to predict their potential biological functions. Conclusions We report a comprehensive study of potato miRNAs at genome-wide level by high-throughput sequencing and demonstrate that these miRNAs have tissue and/or developmental stage-specific expression profile. Also, predicted targets of conserved miRNAs were experimentally confirmed for the first time in potato. Our findings indicate the existence of extensive and complex small RNA population in this crop and suggest their important role in pathways involved in diverse biological processes, including tuber development. PMID:24397411

2014-01-01

65

Identification of drought-responsive microRNAs in leaf and stem tissues of Oryza sativa by Solexa sequencing  

NASA Astrophysics Data System (ADS)

In this study we profiled the microRNA (miRNA) sequences from three rice varieties: Vandana (droughttolerant), Aday Sel (drought-tolerant) and IR64 (drought-susceptible) in greenhouse conditions. Drought treatment was given to three week old seedlings by withholding watering until leaf rolling was observed while controls were given sufficient water. Among the 21 highly conserved miRNA families in rice, we found that 10 families have at least a common mature miRNA member that is differentially expressed between leaf and stem tissues. Our results also suggest that the predicted target genes in these differentially expressed conserved and non-conserved miRNAs are functionally diverse. A wide range of biological processes are found to be regulated by these target genes between both tissues, namely root development (5.3-5.7%), cell transport (13.2-18.4%), response to stress (10.5-11.3%), lignin catabolic process (3.8-5.3%), metabolic processes (32.1-39.5%), oxidation-reduction process (9.4-13.2%) and DNA replication (5.7-7.9%). Progress is still being made to study the expression profiles of differentially expressed miRNAs in our datasets in order to select the potential miRNA candidates that play major regulatory roles in plant molecular response under drought stress conditions. We hope that the miRNA profiling data will provide new information to better understand the regulation of drought-tolerant genes at the genome level.

Huat, Cheah Boon; Nadarajah, Kalaivani; Ratnam, Wickneswari

2014-09-01

66

Piper nigrum Leaf and Stem Assisted Green Synthesis of Silver Nanoparticles and Evaluation of Its Antibacterial Activity Against Agricultural Plant Pathogens  

PubMed Central

Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460?nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 750?nm and 930?nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology. PMID:24558336

Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Rajeshkumar, Shanmugam; Malarkodi, Chelladurai; Pandian, Kannaiyan; Annadurai, Gurusamy

2014-01-01

67

Pretreatment with scutellaria baicalensis stem-leaf total flavonoid protects against cerebral ischemia/reperfusion injury in hippocampal neurons  

PubMed Central

Previous experimental studies have shown that cerebral infarction can be effectively reduced following treatment with scutellaria baicalensis stem-leaf total flavonoid (SSTF). However, the mechanism of action of SSTF as a preventive drug to treat cerebral infarction remains unclear. In this study, Sprague-Dawley rats were pretreated with 50, 100, 200 mg/kg SSTF via intragastric administration for 1 week prior to the establishment of focal cerebral ischemia/reperfusion injury. The results showed that pretreatment with SSTF effectively improved neurological function, reduced brain water content and the permeability of blood vessels, ameliorated ischemia-induced morphology changes in hippocampal microvessels, down-regulated Fas and FasL protein expression, elevated the activity of superoxide dismutase and glutathione peroxidase, and decreased malondialdehyde content. In contrast to low-dose SSTF pretreatment, the above changes were most obvious after pretreatment with moderate- and high-doses of SSTF. Experimental findings indicate that SSTF pretreatment can exert protective effects on the brain against cerebral ischemia/reperfusion injury. The underlying mechanisms may involve reducing brain water content, increasing microvascular recanalization, inhibiting the apoptosis of hippocampal neurons, and attenuating free radical damage.

Kong, Xiangyu; Kong, Wei; Miao, Guangxin; Zhao, Shumin; Chen, Meng; Zheng, Xiaoying; Bai, Jiangtao

2014-01-01

68

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

2013-05-01

69

Grain Amaranths Are Defoliation Tolerant Crop Species Capable of Utilizing Stem and Root Carbohydrate Reserves to Sustain Vegetative and Reproductive Growth after Leaf Loss  

PubMed Central

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

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

2013-01-01

70

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

E-print Network

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 ...

Wang, Zhengyuan

71

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

PubMed

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

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

2013-07-01

72

Two alternative recessive quantitative trait loci influence resistance to spring black stem and leaf spot in Medicago truncatula  

PubMed Central

Background Knowledge of the genetic basis of plant resistance to necrotrophic pathogens is incomplete and has been characterised in relatively few pathosystems. In this study, the cytology and genetics of resistance to spring black stem and leaf spot caused by Phoma medicaginis, an economically important necrotrophic pathogen of Medicago spp., was examined in the model legume M. truncatula. Results Macroscopically, the resistant response of accession SA27063 was characterised by small, hypersensitive-like spots following inoculation while the susceptible interaction with accessions A17 and SA3054 showed necrotic lesions and spreading chlorosis. No unique cytological differences were observed during early infection (<48 h) between the resistant and susceptible genotypes, except pathogen growth was restricted to one or a few host cells in SA27063. In both interactions reactive oxygen intermediates and phenolic compounds were produced, and cell death occurred. Two F2 populations segregating for resistance to spring black stem and leaf spot were established between SA27063 and the two susceptible accessions, A17 and SA3054. The cross between SA27063 and A17 represented a wider cross than between SA27063 and SA3054, as evidenced by higher genetic polymorphism, reduced fertility and aberrant phenotypes of F2 progeny. In the SA27063 A17 F2 population a highly significant quantitative trait locus (QTL, LOD = 7.37; P < 0.00001) named resistance to the necrotroph Phoma medicaginis one (rnpm1) genetically mapped to the top arm of linkage group 4 (LG4). rnpm1 explained 33.6% of the phenotypic variance in the population's response to infection depicted on a 15 scale and was tightly linked to marker AW256637. A second highly significant QTL (LOD = 6.77; P < 0.00001), rnpm2, was located on the lower arm of LG8 in the SA27063 SA3054 map. rnpm2 explained 29.6% of the phenotypic variance and was fine mapped to a 0.8 cM interval between markers h2_16a6a and h2_21h11d. rnpm1 is tightly linked to a cluster of Toll/Interleukin1 receptor-nucleotide binding site-leucine-rich repeat (TIR-NBS-LRR) genes and disease resistance protein-like genes, while no resistance gene analogues (RGAs) are apparent in the genomic sequence of the reference accession A17 at the rnpm2 locus. Conclusion The induction of defence responses and cell death in the susceptible interaction following infection by P. medicaginis suggested this pathogen is not negatively affected by these responses and may promote them. A QTL for resistance was revealed in each of two populations derived from crosses between a resistant accession and two different susceptible accessions. Both loci are recessive in nature, and the simplest explanation for the existence of two separate QTLs is the occurrence of host genotype-specific susceptibility loci that may interact with undetermined P. medicaginis virulence factors. PMID:18366746

Kamphuis, Lars G; Lichtenzveig, Judith; Oliver, Richard P; Ellwood, Simon R

2008-01-01

73

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

74

In vitro shoot proliferation of 5-leaf aralia explants from field grown plants and forced dormant stems  

Microsoft Academic Search

A. Sieboldianus (5-leaf aralia) is recalcitrant for micropropagation, but has very good landscaping potential. This research was conducted\\u000a with the following objectives: (1) to study effects of BA, TDZ, CPPU, 2iP, kinetin and zeatin in woody plant medium on the\\u000a performance of softwood shoot nodal explants produced by field grown 5-leaf aralia plants; (2) to investigate influences of\\u000a BA or

Guochen Yang; Paul E. Read

1997-01-01

75

Phylogeny in Defining Model Plants for Lignocellulosic Ethanol Production: A Comparative Study of Brachypodium distachyon, Wheat, Maize, and Miscanthus x giganteus Leaf and Stem Biomass  

PubMed Central

The production of ethanol from pretreated plant biomass during fermentation is a strategy to mitigate climate change by substituting fossil fuels. However, biomass conversion is mainly limited by the recalcitrant nature of the plant cell wall. To overcome recalcitrance, the optimization of the plant cell wall for subsequent processing is a promising approach. Based on their phylogenetic proximity to existing and emerging energy crops, model plants have been proposed to study bioenergy-related cell wall biochemistry. One example is Brachypodium distachyon, which has been considered as a general model plant for cell wall analysis in grasses. To test whether relative phylogenetic proximity would be sufficient to qualify as a model plant not only for cell wall composition but also for the complete process leading to bioethanol production, we compared the processing of leaf and stem biomass from the C3 grasses B. distachyon and Triticum aestivum (wheat) with the C4 grasses Zea mays (maize) and Miscanthus x giganteus, a perennial energy crop. Lambda scanning with a confocal laser-scanning microscope allowed a rapid qualitative analysis of biomass saccharification. A maximum of 108117 mg ethanolg?1 dry biomass was yielded from thermo-chemically and enzymatically pretreated stem biomass of the tested plant species. Principal component analysis revealed that a relatively strong correlation between similarities in lignocellulosic ethanol production and phylogenetic relation was only given for stem and leaf biomass of the two tested C4 grasses. Our results suggest that suitability of B. distachyon as a model plant for biomass conversion of energy crops has to be specifically tested based on applied processing parameters and biomass tissue type. PMID:25133818

Meineke, Till; Manisseri, Chithra; Voigt, Christian A.

2014-01-01

76

Phylogeny in defining model plants for lignocellulosic ethanol production: a comparative study of Brachypodium distachyon, wheat, maize, and Miscanthus x giganteus leaf and stem biomass.  

PubMed

The production of ethanol from pretreated plant biomass during fermentation is a strategy to mitigate climate change by substituting fossil fuels. However, biomass conversion is mainly limited by the recalcitrant nature of the plant cell wall. To overcome recalcitrance, the optimization of the plant cell wall for subsequent processing is a promising approach. Based on their phylogenetic proximity to existing and emerging energy crops, model plants have been proposed to study bioenergy-related cell wall biochemistry. One example is Brachypodium distachyon, which has been considered as a general model plant for cell wall analysis in grasses. To test whether relative phylogenetic proximity would be sufficient to qualify as a model plant not only for cell wall composition but also for the complete process leading to bioethanol production, we compared the processing of leaf and stem biomass from the C3 grasses B. distachyon and Triticum aestivum (wheat) with the C4 grasses Zea mays (maize) and Miscanthus x giganteus, a perennial energy crop. Lambda scanning with a confocal laser-scanning microscope allowed a rapid qualitative analysis of biomass saccharification. A maximum of 108-117 mg ethanolg(-1) dry biomass was yielded from thermo-chemically and enzymatically pretreated stem biomass of the tested plant species. Principal component analysis revealed that a relatively strong correlation between similarities in lignocellulosic ethanol production and phylogenetic relation was only given for stem and leaf biomass of the two tested C4 grasses. Our results suggest that suitability of B. distachyon as a model plant for biomass conversion of energy crops has to be specifically tested based on applied processing parameters and biomass tissue type. PMID:25133818

Meineke, Till; Manisseri, Chithra; Voigt, Christian A

2014-01-01

77

Chemical Composition of the Essential Oils Obtained From the Flower, Leaf and Stem of Artemisia campestris L. From Iran  

Microsoft Academic Search

The composition of the essential oils obtained from the flowers, leaves and stems of Artemisia campestris L. were analyzed by GC and GC\\/MS. Nineteen compounds representing 95.4% of the oil were identified in the flower oil, 22 compounds making up 90.3% of the oil were characterized in the oil obtained from leaves, and 14 compounds representing 96.7% of the stem

Masoud Kazemi; Maryam Tabatabaei-Anaraki; Abdolhossein Rustaiyan; Alireza Motevalizadeh; Shiva Masoudi

2009-01-01

78

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

79

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 810 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--brac (bab) locus, all encoding nuclear BTB/POZ factors of the Tramtrack Group, are involved in limiting the number of ovarioles in D. melanogaster. At least two different processes are differentially perturbed by reducing the function of these genes. We found that when the bab dose is reduced, sorting of TF cells into TFs was affected such that each TF contains fewer cells and more TFs are formed. In contrast, psq mutants exhibited a greater number of TF cells per ovary, with a normal number of cells per TF, thereby leading to formation of more TFs per ovary than in the wild type. Our results indicate that two parallel genetic pathways under the control of a network of nuclear BTB factors are combined in order to negatively control the number of germline stem cell niches. PMID:23185495

Chalvet, Fabienne; Netter, Sophie; Dos Santos, Nicolas; Poisot, Emilie; Paces-Fessy, Mlanie; Cumenal, Delphine; Peronnet, Frdrique; Pret, Anne-Marie; Thodore, Laurent

2012-01-01

80

Original article Photosynthesis, leaf area and productivity  

E-print Network

Original article Photosynthesis, leaf area and productivity of 5 poplar clones during; The stem volume and biomass (stem + branches) production, net photosynthesis of mature leaves and leaf area found in volume production, woody biomass production, total leaf area and net photosynthesis. Above

Paris-Sud XI, Université de

81

Notch and EGFR pathway interaction regulates neural stem cell number and self-renewal  

PubMed Central

Specialized cellular microenvironments, or niches, modulate stem cell properties, including cell number, self-renewal and fate decisions1,2. In the adult brain, niches that maintain a source of neural stem cells (NSCs) and neural progenitor cells (NPCs) are the subventricular zone (SVZ) of the lateral ventricle and the dentate gyrus of the hippocampus35. The size of the NSC population of the SVZ at any time is the result of several ongoing processes, including self-renewal, cell differentiation, and cell death. Maintaining the balance between NSC and NPCs in the SVZ niche is critical to supply the brain with specific neural populations, both under normal conditions or after injury. A fundamental question relevant to both normal development and to cell-based repair strategies in the central nervous system is how the balance of different NSC and NPC populations is maintained in the niche. EGFR and Notch signaling pathways play fundamental roles during development of multicellular organisms6. In Drosophila and in C. elegans these pathways may have either cooperative or antagonistic functions79. In the SVZ, Notch regulates NSC identity and self-renewal, whereas EGFR specifically affects NPC proliferation and migration1013. This suggests that interplay of these two pathways may maintain the balance between NSC and NPC numbers. Here we show that functional cell-cell interaction between NPCs and NSCs through epidermal growth factor receptor (EGFR) and Notch signaling plays a crucial role in maintaining the balance between these cell populations in the SVZ. Enhanced EGFR signaling in vivo results in the expansion of the NPC pool, and reduces NSC number and self-renewal. This occurs through a non-cell-autonomous mechanism involving EGFR-mediated regulation of Notch signaling. Our findings define a novel interaction between EGFR and Notch pathways in the adult SVZ, and thus provide a mechanism for NSC and NPC pool maintenance. PMID:20844536

Aguirre, Adan; Rubio, Maria E.; Gallo, Vittorio

2010-01-01

82

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

Microsoft Academic Search

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

Gerardo Avalos; Olivia Sylvester

2010-01-01

83

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

2013-08-01

84

Cell Stem Cell Dynamic Changes in the Copy Number of Pluripotency  

E-print Network

and induced pluripotent stem cells. We performed high-resolution SNP (single- nucleotide polymorphism the dynamic nature of genomic abnormalities in pluripotent stem cells and the need for frequent genomic are free from cancer-associated genomic alterations. Human embryonic stem cell (hESC) lines have been shown

Shamir, Ron

85

Getting more for your marrow: boosting hematopoietic stem cell numbers with PGE2.  

PubMed

Throughout the lifetime of an individual, hematopoietic stem cells (HSCs) self-renew and differentiate into lineages that include erythrocytes, platelets and all immune cells. HSC transplantation offers a potentially curative treatment for a number of hematopoietic and non-hematopoietic malignancies as well as immune and genetic disorders. Limited availability of immune-matched donors reduces the viable options for many patients in need of HSC transplantation, particularly those of diverse racial and ethnic backgrounds. Due to rapid availability and less stringent immune-matching requirements, umbilical cord blood (UCB) has emerged as a valuable source of transplantable HSCs. A single UCB unit contains a suboptimal number of HSCs for treating larger children or adults and there has thus been great clinical interest in expanding UCB HSCs ex vivo for use in transplantation. In this review we discuss the latest research and future avenues for the therapeutic use of small lipid mediator dmPGE2 to expand HSC numbers for transplantation. Originally identified in a chemical screen in zebrafish, dmPGE2 has now advanced to a phase II clinical trial as a therapy for patients with leukemia and lymphoma who are undergoing UCB transplantation. PMID:25094063

Hagedorn, Elliott J; Durand, Ellen M; Fast, Eva M; Zon, Leonard I

2014-12-10

86

Myrothecium roridum leaf spot and stem canker on watermelon in the southern Great Plains: Possible factors for its outbreak  

Technology Transfer Automated Retrieval System (TEKTRAN)

Diseases are generally the greatest yield-limiting factor for watermelon across the U.S. In 2010, a foliar and stem-lesion disease was observed for the first time in Oklahoma causing moderate to severe defoliation. Using microscopic examination, the physical features of the fungus were consistent ...

87

Alfalfa leaf protein and stem cell wall polysaccharide yields and theoretical ethanol production under hay and biomass management systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

Alfalfa (Medicago sativa L.) has been proposed as a biofuel feedstock, where the stems would be processed to produce ethanol and the leaves sold separately as a livestock feed. We propose a different management regime reducing population density, delaying harvest and cutting less frequently per grow...

88

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

89

7 CFR 30.4 - Stemmed.  

Code of Federal Regulations, 2013 CFR

...TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been...

2013-01-01

90

7 CFR 30.4 - Stemmed.  

Code of Federal Regulations, 2012 CFR

...TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been...

2012-01-01

91

7 CFR 30.4 - Stemmed.  

Code of Federal Regulations, 2010 CFR

...Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been removed, including strip...

2010-01-01

92

7 CFR 30.4 - Stemmed.  

...Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been removed, including strip...

2014-01-01

93

7 CFR 30.4 - Stemmed.  

Code of Federal Regulations, 2011 CFR

...Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been removed, including strip...

2011-01-01

94

PHARMACOGNOSTICAL STUDIES OF ON Cnicus wallichi DC LEAF  

PubMed Central

Cnicus wallichi DC belonging to the family Asteraceae, was studied to fix the parameters for pharmacognostical standards in order to ensure the use of only genuine and uniform materials of such herbal remedies, work on standardization assumes vital significance. Pharmacognostical study has therefore, been carried out, covering detailed morphological and anatomical characters, features of the powdered drug including leaf constants like Vein islet number, Vein termination number, Stomatal number, Stomatal index, Palisade ratio, Powder microscopy of the leaf and stem. Physical constants like ash values and extractive values. PMID:22557202

Nanjan, M.J.; Suresh, B.

2006-01-01

95

Changes in leaf hydraulic conductance during leaf shedding in seasonally dry tropical forest  

Microsoft Academic Search

Summary The hydraulic conductance of leaves ( k leaf ) was examined to determine whether this little understood component of the water transport pathway plays a role in governing leaf phenology of two deciduous dry forest trees ( Calycophyllum candidissimum and Rhedera trinervis ). k leaf was monitored in parallel with stem hydraulic conductivity (K stem ) during

T. J. Brodribb; N. M. Holbrook

2003-01-01

96

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

97

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

PubMed Central

Adiantum capillus veneris is a medicinally essential plant used for the treatment of diverse infectious diseases. The study of phytochemical and antimicrobial activities of the plant extracts against multidrug-resistant (MDR) bacteria and medically important fungi is of immense significance. Extracts from the leaves, stems, and roots of Adiantum capillus veneris were extracted with water, methanol, ethanol, ethyl acetate, and hexane and screened for their antimicrobial activity against ten MDR bacterial strains and five fungal strains isolated from clinical and water samples. Ash, moisture, and extractive values were determined according to standard protocols. FTIR (Fourier transform infrared Spectroscopy) studies were performed on different phytochemicals isolated from the extracts of Adiantum capillus Veneris. Phytochemical analysis showed the presence of flavonoids, alkaloids, tannins, saponins, cardiac glycosides, terpenoids, steroids, and reducing sugars. Water, methanol, and ethanol extracts of leaves, stems, and roots showed significant antibacterial and antifungal activities against most of the MDR bacterial and fungal strains. This study concluded that extracts of Adiantum capillus veneris have valuable phytochemicals and significant activities against most of the MDR bacterial strains and medically important fungal strains. PMID:24592156

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

2014-01-01

98

In vitro phytochemical, antibacterial, and antifungal activities of leaf, stem, and root extracts of Adiantum capillus veneris.  

PubMed

Adiantum capillus veneris is a medicinally essential plant used for the treatment of diverse infectious diseases. The study of phytochemical and antimicrobial activities of the plant extracts against multidrug-resistant (MDR) bacteria and medically important fungi is of immense significance. Extracts from the leaves, stems, and roots of Adiantum capillus veneris were extracted with water, methanol, ethanol, ethyl acetate, and hexane and screened for their antimicrobial activity against ten MDR bacterial strains and five fungal strains isolated from clinical and water samples. Ash, moisture, and extractive values were determined according to standard protocols. FTIR (Fourier transform infrared Spectroscopy) studies were performed on different phytochemicals isolated from the extracts of Adiantum capillus Veneris. Phytochemical analysis showed the presence of flavonoids, alkaloids, tannins, saponins, cardiac glycosides, terpenoids, steroids, and reducing sugars. Water, methanol, and ethanol extracts of leaves, stems, and roots showed significant antibacterial and antifungal activities against most of the MDR bacterial and fungal strains. This study concluded that extracts of Adiantum capillus veneris have valuable phytochemicals and significant activities against most of the MDR bacterial strains and medically important fungal strains. PMID:24592156

Ishaq, Muhammad Saqib; Hussain, Muhammad Medrar; Afridi, Muhammad Siddique; Ali, Ghadir; Khattak, Mahrukh; Ahmad, Sohail; Shakirullah

2014-01-01

99

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

PubMed

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

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

2013-01-01

100

PROLIFERATION ACTIVITY AND NUMBER OF STROMAL (CFU-f) AND HAEMOPOIETIC (CFUs) STEM CELLS IN BONE MARROW AND SPLEEN OF RATS OF DIFFERENT AGES  

Microsoft Academic Search

Vacek A.: Proliferation Activity and Number of Stromal and Haemopoietic Stem Cells in Bone Marrow and Spleen of Rats of Different Ages. Acta Vet. Brno 2000, 69: 25-31. The number and proliferation activity of stromal (CFU-f) and haemopoietic (CFUs) stem cells of the femoral bone marrow and the spleen of Wistar rats of different ages were investigated. CFUs were assayed

A. VACEK

101

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

PubMed Central

A Lathyrus sativus L. mutant isolated in ethylmethane sulfonate-treated M2 progeny of mother variety BioL-212 and designated as rlfL-1 was characterized by inwardly rolled-leaf and stem and bud fasciations. The mutant exhibited karyomorphological peculiarities in both mitosis and meiosis with origin of aneuploidy. The mitosis was vigorous with high frequency of divisional cells and their quick turnover presumably steered cell proliferations. Significant transcriptional upregulations of cysteine and glutathione synthesis and concomitant stimulations of glutathione-mediated antioxidant defense helped rlfL-1 mutant to maintain balanced reactive oxygen species (ROS) metabolisms, as deduced by ROS-imaging study. Glutathione synthesis was shut down in buthionine sulfoximine- (BSO-) treated mother plant and mutant, and leaf-rolling and stems/buds fasciations in the mutant were reversed, accompanied by normalization of mitotic cell division process. Antioxidant defense was downregulated under low glutathione-redox but cysteine-desulfurations and photorespiratory glycolate oxidase transcripts were markedly overexpressed, preventing cysteine overaccumulation but resulted in excess H2O2 in BSO-treated mutant. This led to oxidative damage in proliferating cells, manifested by severe necrosis in rolled-leaf and fasciated stems. Results indicated vital role of glutathione in maintaining abnormal proliferations in plant organs, and its deficiency triggered phenotypic reversal through metabolic diversions of cysteine and concomitant cellular and metabolic modulations. PMID:24987684

Talukdar, Dibyendu; Talukdar, Tulika

2014-01-01

102

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

PubMed Central

Background and Aims The leaf sizetwig size spectrum is one of the leading dimensions of plant ecological variation, and now it is under development. The purpose of this study was to test whether the relationship between leaf size and twig size is isometric or allometric, and to examine the relationship between plant allometric growth and life history strategies in the spectrum. Methods Leaf and stem charactersincluding leaf and stem mass, total leaf area, individual leaf area, stem cross-sectional area, leaf number and stem lengthat the twig level for 59 woody species were investigated along an altitudinal gradient on Changbaishan Mountain in the temperate zone of China. The environmental gradient ranges from temperate broad-leaved mixed forest at low altitude, to conifer forest at middle altitude, and to sub-alpine birch forest at high altitude. The scaling relationships between stem cross-sectional area and stem mass, stem mass and leaf mass, and leaf mass and leaf area at the twig level were simultaneously determined. Key Results Twig cross-sectional area was found to have invariant allometric scaling relationships with the stem mass, leaf mass, total leaf area and individual leaf area, all with common slopes being significantly larger than 1, for three altitudinal-zoned vegetation types under investigation. However, leaf mass was found to be isometrically related to stem mass and leaf area along the environmental gradient. Based on the predictions of previous models, the exponent value of the relationship between twig cross-sectional area and total leaf area can be inferred to be 15, which falls between the confidence intervals of the relationship at each altitude, and between the confidence intervals of the common slope value (117156) of this study. This invariant scaling relationship is assumed to result from the fractural network and/or developmental constraints of plants. The allometric constants (y-intercepts) of the relationships between the stem cross-sectional area and leaf area (both total leaf area and individual leaf area) were found to decrease significantly along the altitudinal gradient. This suggests that the species would support less leaf area at a given twig cross-sectional area with increasing environmental stress. Conclusions This study demonstrated that plants respond to the environmental gradient by changing the y-intercepts of the relationship between leaf sizetwig size, while keeping the exponent value of the allometric relationship as an invariant constant. The allometric growth in the twig sizeleaf size spectrum is related to many other components of plant life history strategy, including the well established life history trade-off between efficiency and safety in the hydraulic transport of water. PMID:16254019

SUN, SHUCUN; JIN, DONGMEI; SHI, PEILI

2006-01-01

103

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

PubMed Central

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

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

2009-01-01

104

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. PMID:23160490

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

105

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

PubMed Central

Objectives: Trichomoniasis is one of the most common sexually transmitted diseases in humans and is caused by the protozoan Trichomonas vaginalis. Nowadays, increasing resistance to drugs such as metronidazole resulted in many problem, so new effective remedies are needed. In this study, we evaluate constituents of essential oil and anti-trichomonas activity of Rheum ribes. Materials and Methods: The essential oil from Rheum ribes L. flower growing wild in Iran was analyzed by GC/MS. The parasites were treated with different extract and fractions of the flower, stem, and leave of the plant. Anti-trichomonas activity was evaluated using an in vitro assay. Results: In all, 19 compounds were identified; palmitic acid [27.08%], n-eicosane [9.9%], n-tetracosane [7.34%], linoleic acid [6.56%], and ethyl linoleate [4.76%] were the main components of the oil. Rheum ribes extracts and fractions concentration dependently inhibited the ability of parasites to growth. This was associated with polarity of solvent used for fractionation and plant parts used for extraction. Conclusion: Findings demonstrate the potential of Rheum ribes extracts as an anti-trichomonas agent for human use. Further studies are required to evaluate its toxicity and safety. PMID:25050317

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

2014-01-01

106

Effects of Full-Season Temperature Free-Air-Controlled Enhancement (T-FACE) Ecosystem Warming on Leaf Number  

Technology Transfer Automated Retrieval System (TEKTRAN)

Global warming is likely to affect crop canopy development. However, our ability to quantitatively predict how temperature affects processes such as leaf appearance rates still requires refinement. Although controlled-environment chambers can be used to study temperature responses, they introduce nu...

107

New Multilocus Variable-Number Tandem-Repeat Analysis Tool for Surveillance and Local Epidemiology of Bacterial Leaf Blight and Bacterial Leaf Streak of Rice Caused by Xanthomonas oryzae.  

PubMed

Multilocus variable-number tandem-repeat analysis (MLVA) is efficient for routine typing and for investigating the genetic structures of natural microbial populations. Two distinct pathovars of Xanthomonas oryzae can cause significant crop losses in tropical and temperate rice-growing countries. Bacterial leaf streak is caused by X. oryzae pv. oryzicola, and bacterial leaf blight is caused by X. oryzae pv. oryzae. For the latter, two genetic lineages have been described in the literature. We developed a universal MLVA typing tool both for the identification of the three X. oryzae genetic lineages and for epidemiological analyses. Sixteen candidate variable-number tandem-repeat (VNTR) loci were selected according to their presence and polymorphism in 10 draft or complete genome sequences of the three X. oryzae lineages and by VNTR sequencing of a subset of loci of interest in 20 strains per lineage. The MLVA-16 scheme was then applied to 338 strains of X. oryzae representing different pathovars and geographical locations. Linkage disequilibrium between MLVA loci was calculated by index association on different scales, and the 16 loci showed linear Mantel correlation with MLSA data on 56 X. oryzae strains, suggesting that they provide a good phylogenetic signal. Furthermore, analyses of sets of strains for different lineages indicated the possibility of using the scheme for deeper epidemiological investigation on small spatial scales. PMID:25398857

Poulin, L; Grygiel, P; Magne, M; Gagnevin, L; Rodriguez-R, L M; Forero Serna, N; Zhao, S; El Rafii, M; Dao, S; Tekete, C; Wonni, I; Koita, O; Pruvost, O; Verdier, V; Vernire, C; Koebnik, R

2015-01-15

108

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. PMID:19270704

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

2009-01-01

109

Adipocyte amino acid sensing controls adult germline stem cell number via the amino acid response pathway and independently of Target of Rapamycin signaling in Drosophila.  

PubMed

How adipocytes contribute to the physiological control of stem cells is a critical question towards understanding the link between obesity and multiple diseases, including cancers. Previous studies have revealed that adult stem cells are influenced by whole-body physiology through multiple diet-dependent factors. For example, nutrient-dependent pathways acting within the Drosophila ovary control the number and proliferation of germline stem cells (GSCs). The potential role of nutrient sensing by adipocytes in modulating stem cells in other organs, however, remains largely unexplored. Here, we report that amino acid sensing by adult adipocytes specifically modulates the maintenance of GSCs through a Target of Rapamycin-independent mechanism. Instead, reduced amino acid levels and the consequent increase in uncoupled tRNAs trigger activation of the GCN2-dependent amino acid response pathway within adipocytes, causing increased rates of GSC loss. These studies reveal a new step in adipocyte-stem cell crosstalk. PMID:25359724

Armstrong, Alissa R; Laws, Kaitlin M; Drummond-Barbosa, Daniela

2014-12-01

110

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 dierence between stemC and leafC (DC) provided an indirect measurement of mean leaf transpiration which

XAVIER CHONE; CORNELIS VAN LEEUWEN; DENIS DUBOURDIEU

2001-01-01

111

Volume 156, number 1,2 PHYSICS LETTERS A 3 June 1991 Poisson bracket for the Vlasov equation on a symplectic leaf  

E-print Network

for the Vlasov equation on a symplectic leaf Huanchun Ye, P.J. Morrison Physics Department and Institute to a given symplectic leaf. The restricted equation of motion is written in terms of a generating function leaf is the phase space of an ordinary Hamiltonian system.) Thus it is of interest to study

Morrison, Philip J.,

112

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

PubMed Central

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

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

2014-01-01

113

Leaf Shape  

NSDL National Science Digital Library

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

114

An analysis of leaf shapes for a selection of deciduous trees  

E-print Network

An analysis of leaf shapes for a selection of deciduous trees David E. Rydeheard 1 Introduction. Measure at half-way pointMeasure at quarter-way point Measure at three-quarter-way point Leaf base: join with leaf-stem Leaf length Figure 1: Diagram of leaf measurements. To capture the range of shapes

Rydeheard, David

115

An analysis of leaf shapes for a selection of deciduous trees  

E-print Network

An analysis of leaf shapes for a selection of deciduous trees David E. Rydeheard #3; 1 Introduction. Measure at half-way point Measure at quarter-way point Measure at three-quarter-way point Leaf base: join with leaf-stem Leaf length Figure 1: Diagram of leaf measurements. To capture the range of shapes

Rydeheard, David

116

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. PMID:22253226

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

2012-01-01

117

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

118

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.

119

Plants: Roots, Stems and Leaves 85 Plants: Roots, Stems and Leaves  

E-print Network

are at the tips (or apices) of plant parts. The shoot apical meristem is at the tip of the shoot, while the root;Plants: Roots, Stems and Leaves 87 The basic parts of the leaf are a leaf base, which is the region wherePlants: Roots, Stems and Leaves 85 Plants: Roots, Stems and Leaves Unlike animals, plants only have

Koptur, Suzanne

120

Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions.  

PubMed

Some tissue types give rise to human cancers millions of times more often than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue's homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to "bad luck," that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes. PMID:25554788

Tomasetti, Cristian; Vogelstein, Bert

2015-01-01

121

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

PubMed Central

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

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

2013-01-01

122

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

123

7 CFR 29.1029 - Leaf scrap.  

Code of Federal Regulations, 2011 CFR

... Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

2011-01-01

124

7 CFR 29.1029 - Leaf scrap.  

Code of Federal Regulations, 2010 CFR

... Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

2010-01-01

125

7 CFR 29.1029 - Leaf scrap.  

Code of Federal Regulations, 2012 CFR

... Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

2012-01-01

126

7 CFR 29.1029 - Leaf scrap.  

Code of Federal Regulations, 2013 CFR

... Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

2013-01-01

127

7 CFR 29.1029 - Leaf scrap.  

... Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

2014-01-01

128

7 CFR 28.525 - Symbols and code numbers.  

Code of Federal Regulations, 2010 CFR

...b) Symbols and Code Numbers used for Leaf Grades of American Upland Cotton. Leaf grade Symbol Code No. Leaf Grade 1 LG1 1 Leaf Grade 2 LG2 2 Leaf Grade 3 LG3 3 Leaf Grade 4 LG4 4 Leaf Grade 5 LG5 5 Leaf Grade 6...

2010-01-01

129

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

PubMed

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

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

2013-09-01

130

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  

SciTech Connect

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_sign} SR17SS53 and TTP{number_sign} SR18SS41 involves bench scale studies to assess the rates and efficiencies of various composting schemes for volume and weight reduction of leaf and stalk biomass (SB). Ultimately, the data will be used to design a composting process for biomass proposed by MSE for phytoremediation studies at SRS. This could drastically reduce costs for transporting and disposing of contaminated biomass resulting from a future major phytoremediation effort for soil clean-up at the site. The composting studies at SRTC includes collaboration with personnel from the University of Georgia, who will conduct chemical analyses of the plant material after harvest, pre-treatment, and composting for specific time periods. Parameters to be measured will include: lignin, hemicellulose, cellulose, carbon and nitrogen. The overall objective of this project is to identify or develop: (1) an inexpensive source of inoculum (consisting of nutrients and/or microorganisms) capable of significantly enhancing biomass degradation, (2) an optimum range of operating parameters for the composting process, and (3) a process design for the solid state degradation of lignocellulosic biomass contaminated with radionuclides that is superior to existing alternatives for dealing with such waste.

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

1997-05-28

131

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.

132

Numbers  

NSDL National Science Digital Library

The purpose of this video tutorial is to review a couple ways in which we think about numbers. Thinking in terms of street numbers, money in bank accounts, and quantum particles (e.g. Bose-Einstein condensate) is contrasted with focusing on associating numbers with distinguishable manipulatives, as is more familiar in K-8 courses. This video concludes with a reminder that the symbol "infinity" is not, itself, a number.

2013-06-14

133

Numbers  

NSDL National Science Digital Library

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

Edkins, Jo

2006-01-01

134

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. PMID:21841904

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

2011-01-01

135

Recovery of Leaf Area through Accelerated Shoot Ontogeny in Thrips?damaged Cotton Seedlings  

PubMed Central

Background and Aims Leaf area of cotton seedlings (Gossypium hirsutum) can be reduced by as much as 50% by early season thrips infestations, but it is well documented that plants can regain the difference in leaf area once infestation ceases. The processes involved in the recovery have not been identified. Hypotheses include enhancement of the photosynthetic rate of the damaged leaves, more efficient leaf construction (i.e. more leaf area per unit of dry matter invested in new leaves), and more branching. Methods This 2?year field study examined these hypotheses and found that thrips?affected plants recovered from a 30% reduction in total leaf area. During the recovery period, repeated measurements of gas exchange, leaf morphology and individual leaf areas at all nodes were made to assess their contribution to the recovery. Key Results Recovery was not achieved through the previously proposed mechanisms. The pattern of nodal development indicated that the duration of leaf expansion of the smaller deformed leaves was shorter than that of control leaves, possibly because they had fewer cells. The production and expansion of healthy upper node leaves in thrips?affected plants could, therefore, begin sooner, about 125 nodes in advance of control plants. The proposed process of recovery was evident but weaker in the second year where thrips numbers were higher. Conclusions It is concluded that thrips?affected plants overcame the leaf area disparity through an accelerated ontogeny of main stem leaves. By completing the expansion of smaller but normally functioning lower node leaves earlier, resources were made available to the unfolding of larger upper node leaves in advance of control plants. The generality of this mode of plant resistance in pest damage remains to be determined. PMID:15155380

LEI, TOM T.; WILSON, LEWIS J.

2004-01-01

136

Leaf Development  

PubMed Central

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

2013-01-01

137

Leaf Living  

NSDL National Science Digital Library

In this outdoor fall activity, learners find out what living in or under a layer of leaves is like. Learners will discover that animals that live in leaf litter use different senses to find prey, avoid predators, and to navigate through the litter. Learners role play predator and preythe "prey" hides in a large pile of leaves, and the "predator" tries to "strike" by reaching straight into the leaf pile to grab the "prey." Learners also consider what body adaptations help organisms that spend part of their life under the leaves.

Lawrence Hall of Science

1981-01-01

138

Variable Number of Tandem Repeat Markers in the Genome Sequence of Mycosphaerella Fijiensis, the Causal Agent of Black Leaf Streak Disease of Banana (Musa spp.)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mycosphaerella fijiensis, the causal agent of banana leaf streak disease (commonly known as black Sigatoka), is the most devastating pathogen attacking bananas (Musa spp). Recently the whole genome sequence of M. fijiensis became available. This sequence was screened for the presence of Variable Num...

139

Enrichment of cardiac differentiation by a large starting number of embryonic stem cells in embryoid bodies is mediated by the Wnt11-JNK pathway.  

PubMed

Embryoid bodies (EBs) with large starting numbers of embryonic stem cells (ESCs) have a greater degree of cardiac differentiation than from low numbers of EBs. However, the biological roles of signaling molecules in these effects are not well understood. Here, we show that groups of EBs with different starting numbers of ESCs had differential gene expression patterns for Wnt5a and Wnt11. Wnt11 significantly increased the percentage of beating EBs by up-regulating the expression of the cardiac-specific genes. Wnt5a did not show these effects. Moreover, Wnt11 significantly increased the level of phosphorylated Jun N-terminal kinase. The inhibition of the JNK pathway by SP600125 blocked the effects of Wnt11. Thus, enrichment of cardiac differentiation in groups of EBs with a larger starting number of ESCs is mediated by the Wnt11-JNK pathway. PMID:25312921

Chen, Ming; Qian, Cheng; Bi, Lin-Lin; Zhao, Fang; Zhang, Guang-Yu; Wang, Zhi-Quan; Gan, Xue-Dong; Wang, Yang-Gan

2015-02-01

140

Seasonal patterns of leaf photosynthetic and secondary xylem vascular traits in current-year stems of three Sorbus species with contrasting growth habits.  

PubMed

Seasonal effects of environmental variables on photosynthetic activity and secondary xylem formation provide data to demonstrate how environmental factors together with leaf ageing during the season control tree growth. In this study, we assessed physiological responses in photosynthetic behaviour to seasonal climate changes, and also identified seasonal differences in vascular traits within differentiating secondary xylem tissue from three diploid species of the taxonomically complex genus Sorbus. From sampling day 150, a clear physiological segregation of S. chamaemespilus from S. torminalis and S. aria was evident. The shrubby species S. chamaemespilus could be distinguished by a higher photosynthetic capacity between days 150 and 206. This was reflected in its associations with net CO2 assimilation rate (PN), maximum photochemical efficiency of PSII (F(v)/F(m)), variable-to-initial fluorescence ratio (F(v)/F(0)), potential electron acceptor capacity ('area') in multivariate space, and also its associations with log-transformed vessel area and log-transformed relative conductivity between days 239 and 268. The maximum segregation and differentiation among the examined Sorbus species was on sampling day 206. The largest differences between S. torminalis and S. aria were found on day 115, when the latter species clearly showed closer associations with high values of vessel density and transpiration (E). Sampling day clusters were arranged along an arch-like gradient that reflected the positioning of the entire growing season in multivariate space. This arch-like pattern was most apparent in the case of S. chamaemespilus, but was also observed in S. torminalis and S. aria. PMID:24456305

?urkovi?, J; ?a?ov, I; Kardoov, M; Kurjak, D

2014-09-01

141

Leaf Type  

NSDL National Science Digital Library

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

142

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

143

Effect of harvesting interval and defoliation on yield and chemical composition of leaves, stems and tubers of sweet potato ( Ipomoea batatas L. (Lam.)) plant parts  

Microsoft Academic Search

Fifteen sweet potato varieties were grown for 120 days, in two planting seasons in Hue, Vietnam. Leaf, stem and tuber dry matter (DM) yields were measured and chemically analysed. In Experiments 1 and 2, sweet potato vines were harvested at intervals of 15, 20 or 30 days. In Experiment 3, 25, 50, 75 or 100% of the total number of

Le Van An; Bodil E Frankow-Lindberg; Jan Erik Lindberg

2003-01-01

144

Predicting Stem Length of Cut Flower Roses at Harvest Using Stem Elongation Rates in Relationship to Developmental Events  

E-print Network

113 Predicting Stem Length of Cut Flower Roses at Harvest Using Stem Elongation Rates Sciences, One Shields Ave. University of California, Davis, CA 95616 USA Keywords: Richards function, stem quality, leaf unfolding, Rosa hybrida Abstract Stem length is a major determinant of rose productivity

Lieth, J. Heinrich

145

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

146

Geminin deletion increases the number of fetal hematopoietic stem cells by affecting the expression of key transcription factors.  

PubMed

Balancing stem cell self-renewal and initiation of lineage specification programs is essential for the development and homeostasis of the hematopoietic system. We have specifically ablated geminin in the developing murine hematopoietic system and observed profound defects in the generation of mature blood cells, leading to embryonic lethality. Hematopoietic stem cells (HSCs) accumulated in the fetal liver following geminin ablation, while committed progenitors were reduced. Genome-wide transcriptome analysis identified key HSC transcription factors as being upregulated upon geminin deletion, revealing a gene network linked with geminin that controls fetal hematopoiesis. In order to obtain mechanistic insight into the ability of geminin to regulate transcription, we examined Hoxa9 as an example of a key gene in definitive hematopoiesis. We demonstrate that in human K562 cells geminin is associated with HOXA9 regulatory elements and its absence increases HOXA9 transcription similarly to that observed in vivo. Moreover, silencing geminin reduced recruitment of the PRC2 component SUZ12 to the HOXA9 locus and resulted in an increase in RNA polymerase II recruitment and H3K4 trimethylation (H3K4me3), whereas the repressive marks H3K9me3 and H3K27me3 were reduced. The chromatin landscape was also modified at the regulatory regions of HOXA10 and GATA1. K562 cells showed a reduced ability to differentiate to erythrocytes and megakaryocytes upon geminin silencing. Our data suggest that geminin is indispensable for fetal hematopoiesis and regulates the generation of a physiological pool of stem and progenitor cells in the fetal hematopoietic system. PMID:25516969

Karamitros, Dimitris; Patmanidi, Alexandra L; Kotantaki, Panoraia; Potocnik, Alexandre J; Bhr-Ivacevic, Tomi; Benes, Vladimir; Lygerou, Zoi; Kioussis, Dimitris; Taraviras, Stavros

2015-01-01

147

Stem Cells  

MedlinePLUS

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

148

The Analysis of Leaf Shape Using Fractal Geometry.  

ERIC Educational Resources Information Center

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

Hartvigsen, Gregg

2000-01-01

149

LeafJ: An ImageJ Plugin for Semi-automated Leaf Shape Measurement  

PubMed Central

High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review1 and recent examples2-4). Leaves are the primary photosynthetic organ, and their size and shape vary developmentally and environmentally within a plant. For these reasons studies on leaf morphology require measurement of multiple parameters from numerous leaves, which is best done by semi-automated phenomics tools5,6. Canopy shade is an important environmental cue that affects plant architecture and life history; the suite of responses is collectively called the shade avoidance syndrome (SAS)7. Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices8. To date, leaf shape programs (e.g. SHAPE9, LAMINA10, LeafAnalyzer11, LEAFPROCESSOR12) can measure leaf outlines and categorize leaf shapes, but can not output petiole length. Lack of large-scale measurement systems of leaf petioles has inhibited phenomics approaches to SAS research. In this paper, we describe a newly developed ImageJ plugin, called LeafJ, which can rapidly measure petiole length and leaf blade parameters of the model plant Arabidopsis thaliana. For the occasional leaf that required manual correction of the petiole/leaf blade boundary we used a touch-screen tablet. Further, leaf cell shape and leaf cell numbers are important determinants of leaf size13. Separate from LeafJ we also present a protocol for using a touch-screen tablet for measuring cell shape, area, and size. Our leaf trait measurement system is not limited to shade-avoidance research and will accelerate leaf phenotyping of many mutants and screening plants by leaf phenotyping. PMID:23380664

Mumbach, Maxwell R.; Palmer, Christine M.

2013-01-01

150

``Stemness'': Transcriptional Profiling of Embryonic and Adult Stem Cells  

Microsoft Academic Search

The transcriptional profiles of mouse embryonic, neural, and hematopoietic stem cells were compared to define a genetic program for stem cells. A total of 216 genes are enriched in all three types of stem cells, and several of these genes are clustered in the genome. When compared to differentiated cell types, stem cells express a significantly higher number of genes

Miguel Ramalho-Santos; Soonsang Yoon; Yumi Matsuzaki; Richard C. Mulligan; Douglas A. Melton

2002-01-01

151

[Effect of hydroxyurea on the number of hematopoietic stem cells, stromal cell precursors and cell precursors of thymus lymphoid tissue in the bone marrow of mice during aging].  

PubMed

The concentration of hemopoietic stem cells (colony-forming cells in the spleen - CFC-S) decreases in the bone marrow of CBA mice during ageing, whereas the concentration of precursors for stromal fibroblasts (colony-forming cells for fibroblasts-CFC-F) increases. The total numbers of nucleated cells, CFC-S and CFC-F in the bone marrow of old mice essentially increase. Hydroxyurea, administered in vivo, does not effect the concentration of CFC-S, but it increases CFC-F concentration in the bone marrow of mice. Hydroxyurea produces just the same suppressive effect on the numbers of nucleated cells, CFC-S and CFC-F in the mice of different ages, and stimulates the capacity of bone marrow donors to repopulate the thymus of the irradiated young recipients. PMID:6485091

Sidorenko, A V; Andrianova, L F

1984-07-01

152

Environmental control on eastern broadleaf forest species' leaf wax distributions and D/H ratios  

E-print Network

Environmental control on eastern broadleaf forest species' leaf wax distributions and D/H ratios plant's leaf waxes D/H ratios are affected by these parameters remains in question. Understanding Coast of the US, from Florida to Maine. Hydrogen isotopic compo- sitions of leaf wax n-alkanes, stem

Tipple, Brett

153

Environmental control on eastern broadleaf forest species' leaf wax distributions and D/H ratios  

E-print Network

Environmental control on eastern broadleaf forest species' leaf wax distributions and D/H ratios the degree to which an individual plant's leaf waxes D/H ratios are affected by these parameters remains- sitions of leaf wax n-alkanes, stem and surface waters were analyzed and compared against high

154

7 CFR 28.525 - Symbols and code numbers.  

Code of Federal Regulations, 2013 CFR

...Below Middling Yellow Stained) BG 85 (b) Symbols and Code Numbers used for Leaf Grades of American Upland Cotton. Leaf grade Symbol Code No. Leaf Grade 1 LG1 1 Leaf Grade 2 LG2 2 Leaf Grade 3 LG3 3 Leaf Grade...

2013-01-01

155

7 CFR 28.525 - Symbols and code numbers.  

...Below Middling Yellow Stained) BG 85 (b) Symbols and Code Numbers used for Leaf Grades of American Upland Cotton. Leaf grade Symbol Code No. Leaf Grade 1 LG1 1 Leaf Grade 2 LG2 2 Leaf Grade 3 LG3 3 Leaf Grade...

2014-01-01

156

7 CFR 28.525 - Symbols and code numbers.  

Code of Federal Regulations, 2011 CFR

...Below Middling Yellow Stained) BG 85 (b) Symbols and Code Numbers used for Leaf Grades of American Upland Cotton. Leaf grade Symbol Code No. Leaf Grade 1 LG1 1 Leaf Grade 2 LG2 2 Leaf Grade 3 LG3 3 Leaf Grade...

2011-01-01

157

7 CFR 28.525 - Symbols and code numbers.  

Code of Federal Regulations, 2012 CFR

...Below Middling Yellow Stained) BG 85 (b) Symbols and Code Numbers used for Leaf Grades of American Upland Cotton. Leaf grade Symbol Code No. Leaf Grade 1 LG1 1 Leaf Grade 2 LG2 2 Leaf Grade 3 LG3 3 Leaf Grade...

2012-01-01

158

Changes in Leaf Trichomes and Epicuticular Flavonoids during Leaf Development in Three Birch Taxa  

PubMed Central

Background and Aims Changes in number of trichomes and in composition and concentrations of their exudates throughout leaf development may have important consequences for plant adaptation to abiotic and biotic factors. In the present study, seasonal changes in leaf trichomes and epicuticular flavonoid aglycones in three Finnish birch taxa (Betula pendula, B. pubescens ssp. pubescens, and B. pubescens ssp. czerepanovii) were followed. Methods Trichome number and ultrastructure were studied by means of light, scanning and transmission electron microscopy, while flavonoid aglycones in ethanolic leaf surface extracts were analysed by high-pressure liquid chromatography. Key Results Density of both glandular and non-glandular trichomes decreased drastically with leaf expansion while the total number of trichomes per leaf remained constant, indicating that the final number of trichomes is established early in leaf development. Cells of glandular trichomes differentiate before those of the epidermis and produce secreted material only during the relatively short period (around 12 weeks) of leaf unfolding and expansion. In fully expanded leaves, glandular trichomes appeared to be at the post-secretory phase and function mainly as storage organs; they contained lipid droplets and osmiophilic material (probably phenolics). Concentrations (mg g?1 d. wt) of surface flavonoids decreased with leaf age in all taxa. However, the changes in total amount (g per leaf) of flavonoids during leaf development were taxon-specific: no changes in B. pubescens ssp. czerepanovii, increase in B. pendula and in B. pubescens ssp. pubescens followed by the decline in the latter taxon. Concentrations of most of the individual leaf surface flavonoids correlated positively with the density of glandular trichomes within species, suggesting the participation of glandular trichomes in production of surface flavonoids. Conclusions Rapid decline in the density of leaf trichomes and in the concentrations of flavonoid aglycones with leaf age suggests that the functional role of trichomes is likely to be most important at the early stages of birch leaf development. PMID:15238348

VALKAMA, ELENA; SALMINEN, JUHA-PEKKA; KORICHEVA, JULIA; PIHLAJA, KALEVI

2004-01-01

159

Tree Leaf Identification and Leaf Display Activity  

NSDL National Science Digital Library

This activity is a tree leaf collection, identification, and display of dried and pressed leaves. It teaches students about distinguishing leaf characteristics as well as a way to display and label their collection.

Hansing, Rebecca

160

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

NASA Technical Reports Server (NTRS)

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

Dougher, Tracy A. O.; Bugbee, Bruce

2004-01-01

161

7 CFR 29.2301 - Stem.  

... Agriculture 2 2014-01-01 2014-01-01 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....

2014-01-01

162

7 CFR 29.3059 - Stem.  

... Agriculture 2 2014-01-01 2014-01-01 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....

2014-01-01

163

7 CFR 29.2301 - Stem.  

Code of Federal Regulations, 2010 CFR

... Agriculture 2 2010-01-01 2010-01-01 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....

2010-01-01

164

7 CFR 29.3059 - Stem.  

Code of Federal Regulations, 2011 CFR

... Agriculture 2 2011-01-01 2011-01-01 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....

2011-01-01

165

7 CFR 29.2553 - Stem.  

Code of Federal Regulations, 2013 CFR

... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

2013-01-01

166

7 CFR 29.3549 - Stem.  

... Agriculture 2 2014-01-01 2014-01-01 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....

2014-01-01

167

7 CFR 29.3059 - Stem.  

Code of Federal Regulations, 2010 CFR

... Agriculture 2 2010-01-01 2010-01-01 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....

2010-01-01

168

7 CFR 29.1061 - Stem.  

Code of Federal Regulations, 2012 CFR

... Agriculture 2 2012-01-01 2012-01-01 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....

2012-01-01

169

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

170

7 CFR 29.2553 - Stem.  

... Agriculture 2 2014-01-01 2014-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

2014-01-01

171

7 CFR 29.1061 - Stem.  

Code of Federal Regulations, 2011 CFR

... Agriculture 2 2011-01-01 2011-01-01 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....

2011-01-01

172

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

173

7 CFR 29.3549 - Stem.  

Code of Federal Regulations, 2012 CFR

... Agriculture 2 2012-01-01 2012-01-01 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....

2012-01-01

174

7 CFR 29.3549 - Stem.  

Code of Federal Regulations, 2011 CFR

... Agriculture 2 2011-01-01 2011-01-01 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....

2011-01-01

175

7 CFR 29.2553 - Stem.  

Code of Federal Regulations, 2011 CFR

... Agriculture 2 2011-01-01 2011-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

2011-01-01

176

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

177

7 CFR 29.1061 - Stem.  

... Agriculture 2 2014-01-01 2014-01-01 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....

2014-01-01

178

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

179

7 CFR 29.2301 - Stem.  

Code of Federal Regulations, 2012 CFR

... Agriculture 2 2012-01-01 2012-01-01 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....

2012-01-01

180

7 CFR 29.3059 - Stem.  

Code of Federal Regulations, 2012 CFR

... Agriculture 2 2012-01-01 2012-01-01 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....

2012-01-01

181

7 CFR 29.2301 - Stem.  

Code of Federal Regulations, 2011 CFR

... Agriculture 2 2011-01-01 2011-01-01 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....

2011-01-01

182

7 CFR 29.2553 - Stem.  

Code of Federal Regulations, 2012 CFR

... Agriculture 2 2012-01-01 2012-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

2012-01-01

183

7 CFR 29.1061 - Stem.  

Code of Federal Regulations, 2010 CFR

... Agriculture 2 2010-01-01 2010-01-01 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....

2010-01-01

184

Nuclear receptor regulation of stemness and stem cell differentiation  

PubMed Central

Stem cells include a diverse number of toti-, pluri-, and multi-potent cells that play important roles in cellular genesis and differentiation, tissue development, and organogenesis. Genetic regulation involving various transcription factors results in the self-renewal and differentiation properties of stem cells. The nuclear receptor (NR) superfamily is composed of 48 ligand-activated transcription factors involved in diverse physiological functions such as metabolism, development, and reproduction. Increasing evidence shows that certain NRs function in regulating stemness or differentiation of embryonic stem (ES) cells and tissue-specific adult stem cells. Here, we review the role of the NR superfamily in various aspects of stem cell biology, including their regulation of stemness, forward- and trans-differentiation events; reprogramming of terminally differentiated cells; and interspecies differences. These studies provide insights into the therapeutic potential of the NR superfamily in stem cell therapy and in treating stem cell-associated diseases (e.g., cancer stem cell). PMID:19696553

Jeong, Yangsik

2009-01-01

185

STEM CELL REGULATION IN THE ARABIDOPSIS SHOOT APICAL MERISTEM  

Technology Transfer Automated Retrieval System (TEKTRAN)

The aerial structure of higher plants is generated dynamically throughout the life cycle through the activity of stem cells that are located at the growing shoot tip, the apical meristem. The stem cells continuously divide to renew themselves and provide cells for leaf, stem and flower formation. St...

186

Discovering candidate genes that regulate resin canal number in Pinus taeda stems by integrating genetic analysis across environments, ages, and populations.  

PubMed

Genetically improving constitutive resin canal development in Pinus stems may enhance the capacity to synthesize terpenes for bark beetle resistance, chemical feedstocks, and biofuels. To discover genes that potentially regulate axial resin canal number (RCN), single nucleotide polymorphisms (SNPs) in 4027 genes were tested for association with RCN in two growth rings and three environments in a complex pedigree of 520 Pinus taeda individuals (CCLONES). The map locations of associated genes were compared with RCN quantitative trait loci (QTLs) in a (P.taedaנPinuselliottii)נP.elliottii pseudo-backcross of 345 full-sibs (BC1). Resin canal number was heritable (h(2) 0.12-0.21) and positively genetically correlated with xylem growth (rg 0.32-0.72) and oleoresin flow (rg 0.15-0.51). Sixteen well-supported candidate regulators of RCN were discovered in CCLONES, including genes associated across sites and ages, unidirectionally associated with oleoresin flow and xylem growth, and mapped to RCN QTLs in BC1. Breeding is predicted to increase RCN 11% in one generation and could be accelerated with genomic selection at accuracies of 0.45-0.52 across environments. There is significant genetic variation for RCN in loblolly pine, which can be exploited in breeding for elevated terpene content. PMID:25266813

Westbrook, Jared W; Walker, Alejandro R; Neves, Leandro G; Munoz, Patricio; Resende, Marcio F R; Neale, David B; Wegrzyn, Jill L; Huber, Dudley A; Kirst, Matias; Davis, John M; Peter, Gary F

2015-01-01

187

Better Algorithms and Bounds for Directed Maximum Leaf Problems  

E-print Network

Better Algorithms and Bounds for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 of Mathematical Sciences Chennai, 600 017, India saket@imsc.res.in Abstract. The Directed Maximum Leaf Out Maximum Leaf Out­Branching problem is to find an out­branching in a given digraph with the maximum number

Krivelevich, Michael

188

Seasonality of Leaf Carbon Isotopic Composition and Leaf Water Isotopic Enrichment in a Mixed Evergreen Forest in Southern California  

NASA Astrophysics Data System (ADS)

Leaf carbon isotopic composition and leaf water isotopic enrichment reflect physiological processes and are important for linking local and regional scale processes to global patterns. We investigated how seasonality affects the isotopic composition of bulk leaf carbon, leaf sugar carbon, and leaf water hydrogen under a Mediterranean climate. Leaf and stem samples were collected monthly from four tree species (Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Quercus chrysolepis) at the James San Jacinto Mountain Reserve in southern California. Mean monthly bulk leaf carbon isotopic composition varied from -34.5 % in P. ponderosa to -24.7 % in P. lambertiana and became more depleted in 13C from the spring to the summer. Mean monthly leaf sugar varied from -29.3 % in P. ponderosa to -21.8 % in P. lambertiana and was enriched in 13C during the winter, spring and autumn, but depleted during the mid-summer. Leaf water hydrogen isotopic composition was 28.4 to 68.8 % more enriched in deuterium than source water and this enrichment was greater as seasonal drought progressed. These data indicate that leaf carbon and leaf water hydrogen isotopic composition provide sensitive measures that connect plant physiological processes to short-term climatic variability.

Santiago, L. S.; Sickman, J. O.; Goulden, M.; DeVan, C.; Pasquini, S. C.; Pivovaroff, A. L.

2011-12-01

189

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

PubMed

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

Spencer, David F

2014-01-01

190

Xylem cavitation in the leaf of Prunus laurocerasus and its impact on leaf hydraulics.  

PubMed

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. PMID:11299351

Nardini, A; Tyree, M T; Salleo, S

2001-04-01

191

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. PMID:11299351

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

2001-01-01

192

Auxin depletion from leaf primordia contributes to organ patterning.  

PubMed

Stem cells are responsible for organogenesis, but it is largely unknown whether and how information from stem cells acts to direct organ patterning after organ primordia are formed. It has long been proposed that the stem cells at the plant shoot apex produce a signal, which promotes leaf adaxial-abaxial (dorsoventral) patterning. Here we show the existence of a transient low auxin zone in the adaxial domain of early leaf primordia. We also demonstrate that this adaxial low auxin domain contributes to leaf adaxial-abaxial patterning. The auxin signal is mediated by the auxin-responsive transcription factor MONOPTEROS (MP), whose constitutive activation in the adaxial domain promotes abaxial cell fate. Furthermore, we show that auxin flow from emerging leaf primordia to the shoot apical meristem establishes the low auxin zone, and that this auxin flow contributes to leaf polarity. Our results provide an explanation for the hypothetical meristem-derived leaf polarity signal. Opposite to the original proposal, instead of a signal derived from the meristem, we show that a signaling molecule is departing from the primordium to the meristem to promote robustness in leaf patterning. PMID:25512543

Qi, Jiyan; Wang, Ying; Yu, Ting; Cunha, Alexandre; Wu, Binbin; Vernoux, Teva; Meyerowitz, Elliot; Jiao, Yuling

2014-12-30

193

Gene expression analysis of human induced pluripotent stem cell-derived neurons carrying copy number variants of chromosome 15q11-q13.1  

PubMed Central

Background Duplications of the chromosome 15q11-q13.1 region are associated with an estimated 1 to 3% of all autism cases, making this copy number variation (CNV) one of the most frequent chromosome abnormalities associated with autism spectrum disorder (ASD). Several genes located within the 15q11-q13.1 duplication region including ubiquitin protein ligase E3A (UBE3A), the gene disrupted in Angelman syndrome (AS), are involved in neural function and may play important roles in the neurobehavioral phenotypes associated with chromosome 15q11-q13.1 duplication (Dup15q) syndrome. Methods We have generated induced pluripotent stem cell (iPSC) lines from five different individuals containing CNVs of 15q11-q13.1. The iPSC lines were differentiated into mature, functional neurons. Gene expression across the 15q11-q13.1 locus was compared among the five iPSC lines and corresponding iPSC-derived neurons using quantitative reverse transcription PCR (qRT-PCR). Genome-wide gene expression was compared between neurons derived from three iPSC lines using mRNA-Seq. Results Analysis of 15q11-q13.1 gene expression in neurons derived from Dup15q iPSCs reveals that gene copy number does not consistently predict expression levels in cells with interstitial duplications of 15q11-q13.1. mRNA-Seq experiments show that there is substantial overlap in the genes differentially expressed between 15q11-q13.1 deletion and duplication neurons, Finally, we demonstrate that UBE3A transcripts can be pharmacologically rescued to normal levels in iPSC-derived neurons with a 15q11-q13.1 duplication. Conclusions Chromatin structure may influence gene expression across the 15q11-q13.1 region in neurons. Genome-wide analyses suggest that common neuronal pathways may be disrupted in both the Angelman and Dup15q syndromes. These data demonstrate that our disease-specific stem cell models provide a new tool to decipher the underlying cellular and genetic disease mechanisms of ASD and may also offer a pathway to novel therapeutic intervention in Dup15q syndrome.

2014-01-01

194

Leaf Modeling and Constrained Leaf Morphing in Leaf Space Saurabh Garg1  

E-print Network

Leaf Modeling and Constrained Leaf Morphing in Leaf Space Saurabh Garg1 , Leow Wee Kheng1 1 School@comp.nus.edu.sg Morphing from an elliptic leaf (first row, first image) to a deltoid leaf (second row, last image) with a constraint of a leaf with both basal and apical extension (second row, first image). Abstract Leaf modeling

Leow, Wee Kheng

195

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

PubMed Central

Background and Aims Leaf life span is widely recognized as a key life history trait associated with herbivory resistance, but rigorous comparative data are rare for seedlings. The goal of this study was to examine how light environment affects leaf life span, and how ontogenetic development during the first year may influence leaf fracture toughness, lamina density and stem density that are relevant for herbivory resistance, leaf life span and seedling survival. Methods Data from three experiments encompassing 104 neotropical woody species were combined. Leaf life span, lamina and vein fracture toughness, leaf and stem tissue density and seedling survival were quantified for the first-year seedlings at standardized ontogenetic stages in shade houses and common gardens established in gaps and shaded understorey in a moist tropical forest in Panama. Mortality of naturally recruited seedlings till 1 year later was quantified in 800 1-m2 plots from 1994 to 2011. Key Results Median leaf life span ranged widely among species, always greater in shade (ranging from 151 to >1790 d in the understorey and shade houses) than in gaps (115867 d), but with strong correlation between gaps and shade. Leaf and stem tissue density increased with seedling age, whereas leaf fracture toughness showed only a weak increase. All these traits were positively correlated with leaf life span. Leaf life span and stem density were negatively correlated with seedling mortality in shade, while gap mortality showed no correlation with these traits. Conclusions The wide spectrum of leaf life span and associated functional traits reflects variation in shade tolerance of first-year seedlings among coexisting trees, shrubs and lianas in this neotropical forest. High leaf tissue density is important in enhancing leaf toughness, a known physical defence, and leaf life span. Both seedling leaf life span and stem density should be considered as key functional traits that contribute to seedling survival in tropical forest understoreys. PMID:23532047

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

2013-01-01

196

Root Hypoxia Reduces Leaf Growth 1  

PubMed Central

This study examined the potential role of restricted phloem export, or import of substances from the roots in the leaf growth response to root hypoxia. In addition, the effects of root hypoxia on abscisic acid (ABA) and zeatin riboside (ZR) levels were measured and their effects on in vitro growth determined. Imposition of root hypoxia in the dark when transpirational water flux was minimal delayed the reduction in leaf growth until the following light period. Restriction of phloem transport by stem girdling did not eliminate the hypoxia-induced reduction in leaf growth. In vitro growth of leaf discs was inhibited in the presence of xylem sap collected from hypoxic roots, and also by millimolar ABA. Disc growth was promoted by sap from aerated roots and by 0.1 micromolar ZR. The flux of both ABA and ZR was reduced in xylem sap from hypoxic roots. Leaf ABA transiently increased twofold after 24 hours of hypoxia exposure but there were no changes in leaf cytokinin levels. Images Figure 3 Figure 4 PMID:16667366

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

1990-01-01

197

Mesenchymal stem cells alleviate atherosclerosis by elevating number and function of CD4(+)CD25 (+)FOXP3 (+) regulatory T-cells and inhibiting macrophage foam cell formation.  

PubMed

Atherosclerosis is a chronic inflammatory disease characterized by the formation of plaques inside arteries, leading to narrowing and blockage. Potential therapeutic strategies include expanding the population of regulatory T-cells (Tregs) to enhance atheroprotective immunity, and inhibiting the formation of macrophage foam cells. Here, we studied the effect of bone marrow-derived mesenchymal stem cells (BM-MSCs) on atherosclerotic plaque formation in Apolipoprotein E(-/-) (ApoE-KO) mice, and elucidated the underlying mechanism. BM-MSCs isolated from 4week-old ApoE-KO mice were evaluated by flow cytometry for expression of MSC-specific markers. Thirty eight week-old ApoE-KO mice were randomly divided into three experimental groups (n=10 per group): 1. MSC group-received BM-MSCs intravenously; 2. Vehicle group-received DMEM; 3. Control group-did not receive any treatment. Administration of MSCs resulted in a marked decrease in the size of atherosclerotic plaques 3months after treatment. In addition, the number and function of CD4(+)CD25(+)FOXP3(+) regulatory T-cells (Tregs) in cultured splenocytes, and the expression of FOXP3 at both mRNA and protein levels, was significantly increased in the MSC group. In vitro experiments further indicated that the formation of macrophage foam cells was inhibited by treatment with MSCs, accompanied by a significant downregulation in CD36 and scavenger receptor A (SRA). Our findings suggest that MSCs play an atheroprotective role by enhancing the number and function of Tregs and inhibiting the formation of macrophage foam cells. Hence, administration of MSCs to atherosclerotic patients might have significant clinical benefits. PMID:25389006

Wang, Zhi Xiao; Wang, Chong Quan; Li, Xiao Yan; Feng, Gao Ke; Zhu, Hong Ling; Ding, Yan; Jiang, Xue Jun

2015-02-01

198

Elm Leaf Beetle  

E-print Network

Elm leaf beetles damage all varieties of elm trees. Learn how to identify this insect and understand its biology and life cycle. There are suggestions for controlling elm leaf beetles, as well as a table of insecticides effective against...

Patrick, Carl D.

2002-05-22

199

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

200

Functional relationships between leaf hydraulics and leaf economic traits in response to nutrient addition in subtropical tree species.  

PubMed

Leaves can be both a hydraulic bottleneck and a safety valve against hydraulic catastrophic dysfunctions, and thus changes in traits related to water movement in leaves and associated costs may be critical for the success of plant growth. A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) addition was done in a semideciduous Atlantic forest in northeastern Argentina. Saplings of five dominant canopy species were grown in similar gaps inside the forests (five control and five N?+?P addition plots). Leaf lifespan (LL), leaf mass per unit area (LMA), leaf and stem vulnerability to cavitation, leaf hydraulic conductance (K(leaf_area) and K(leaf_mass)) and leaf turgor loss point (TLP) were measured in the five species and in both treatments. Leaf lifespan tended to decrease with the addition of fertilizers, and LMA was significantly higher in plants with nutrient addition compared with individuals in control plots. The vulnerability to cavitation of leaves (P50(leaf)) either increased or decreased with the nutrient treatment depending on the species, but the average P50(leaf) did not change with nutrient addition. The P50(leaf) decreased linearly with increasing LMA and LL across species and treatments. These trade-offs have an important functional significance because more expensive (higher LMA) and less vulnerable leaves (lower P50(leaf)) are retained for a longer period of time. Osmotic potentials at TLP and at full turgor became more negative with decreasing P50(leaf) regardless of nutrient treatment. The K(leaf) on a mass basis was negatively correlated with LMA and LL, indicating that there is a carbon cost associated with increased water transport that is compensated by a longer LL. The vulnerability to cavitation of stems and leaves were similar, particularly in fertilized plants. Leaves in the species studied may not function as safety valves at low water potentials to protect the hydraulic pathway from water stress-induced cavitation. The lack of rainfall seasonality in the subtropical forest studied probably does not act as a selective pressure to enhance hydraulic segmentation between leaves and stems. PMID:24284866

Villagra, Mariana; Campanello, Paula I; Bucci, Sandra J; Goldstein, Guillermo

2013-12-01

201

STEM Career  

NSDL National Science Digital Library

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

202

Assessing soybean leaf area and leaf biomass by spectral measurements  

NASA Technical Reports Server (NTRS)

Red and photographic infrared spectral radiances were correlated with soybean total leaf area index, green leaf area index, chlorotic leaf area index, green leaf biomass, chlorotic leaf biomass, and total biomass. The most significant correlations were found to exist between the IR/red radiance ratio data and green leaf area index and/or green leaf biomass (r squared equals 0.85 and 0.86, respectively). These findings demonstrate that remote sensing data can supply information basic to soybean canopy growth, development, and status by nondestructive determination of the green leaf area or green leaf biomass.

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

1979-01-01

203

Leaf and stem CO 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  

Microsoft Academic Search

Net CO 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 uptake was by the leaves and during the daytime. In contrast, for the leafless species Carnegiea gigantea, Ferocactus acanthodes, Coryphantha vivipara,

P. S. Nobel; T. L. Hartsock

1986-01-01

204

Stem Up  

NSDL National Science Digital Library

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

205

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.

206

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.

207

Tomato leaf curl geminivirus associated with cantaloupe yellow leaf disease in Thailand  

Microsoft Academic Search

Geminivirus associated with yellow leaf disease of cantaloupe plants was detected using polymerase chain reaction (PCR) with geminivirus-specific degenerate primers which anneal within the AC1 ORF (replication initiator protein gene) and the AV1 ORF (coat protein gene). A DNA fragment of 1.2 kbp was amplified, cloned and sequenced. The 32-base stem loop region was found in the amplified fragment. This

Kloyjai Samretwanich; Pissawan Chiemsombat; Kruapan Kittipakorn; Masato Ikegami

2000-01-01

208

Increased Cycling Cell Numbers and Stem Cell Associated Proteins as Potential Biomarkers for High Grade Human Papillomavirus+ve Pre-Neoplastic Cervical Disease  

PubMed Central

High risk (oncogenic) human papillomavirus (HPV) infection causes cervical cancer. Infections are common but most clear naturally. Persistent infection can progress to cancer. Pre-neoplastic disease (cervical intraepithelial neoplasia/CIN) is classified by histology (CIN1-3) according to severity. Cervical abnormalities are screened for by cytology and/or detection of high risk HPV but both methods are imperfect for prediction of which women need treatment. There is a need to understand the host virus interactions that lead to different disease outcomes and to develop biomarker tests for accurate triage of infected women. As cancer is increasingly presumed to develop from proliferative, tumour initiating, cancer stem cells (CSCs), and as other oncogenic viruses induce stem cell associated gene expression, we evaluated whether presence of mRNA (detected by qRT-PCR) or proteins (detected by flow cytometry and antibody based proteomic microarray) from stem cell associated genes and/or increased cell proliferation (detected by flow cytometry) could be detected in well-characterised, routinely collected cervical samples from high risk HPV+ve women. Both cytology and histology results were available for most samples with moderate to high grade abnormality. We found that stem cell associated proteins including human chorionic gonadotropin, the oncogene TP63 and the transcription factor SOX2 were upregulated in samples from women with CIN3 and that the stem cell related, cell surface, protein podocalyxin was detectable on cells in samples from a subset of women with CIN3. SOX2, TP63 and human gonadotrophin mRNAs were upregulated in high grade disease. Immunohistochemistry showed that SOX2 and TP63 proteins clearly delineated tumour cells in invasive squamous cervical cancer. Samples from women with CIN3 showed increased proliferating cells. We believe that these markers may be of use to develop triage tests for women with high grade cervical abnormality to distinguish those who may progress to cancer from those who may be treated more conservatively. PMID:25531390

Canham, Maurice; Charsou, Chara; Stewart, June; Moncur, Sharon; Hoodless, Laura; Bhatia, Ramya; Cong, Duanduan; Cubie, Heather; Busby-Earle, Camille; Williams, Alistair; McLoughlin, Victoria; Campbell, John D. M.; Cuschieri, Kate; Howie, Sarah

2014-01-01

209

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

210

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

211

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

212

Phase identity of the maize leaf is determined after leaf initiation  

PubMed Central

The vegetative development of the maize shoot can be divided into juvenile and adult phases based on the types of leaves produced at different times in shoot development. Models for the regulation of phase change make explicit predictions about when the identity of these types of leaves is determined. To test these models, we examined the timing of leaf type determination in maize. Clones induced in transition leaf primordia demonstrated that the juvenile and adult regions of these leaves do not become clonally distinct until after the primordium is 700 ?m in length, implying that these cell fates were undetermined at this stage of leaf development. Adult shoot apices were cultured in vitro to induce rejuvenation. We found that leaf primordia as large as 3 mm in length can be at least partially rejuvenated by this treatment, and the location of rejuvenated tissue is correlated with the maturation pattern of the leaf. The amount and distribution of juvenile tissue in rejuvenated leaves suggests that rejuvenation occurs nearly simultaneously in all leaf primordia. In vitro culture rejuvenated existing leaf primordia and the P0 primordium, but did not change the identity of subsequent primordia or the total number of leaves produced by the shoot. This result suggests that leaf identity can be regulated independently of the identity of the shoot apical meristem, and it implies that vegetative phase change is not initiated by a change in the identity of the shoot apical meristem. PMID:10973480

Orkwiszewski, Joseph A. J.; Poethig, R. Scott

2000-01-01

213

Leaf Hydraulics Lawren Sack1  

E-print Network

Leaf Hydraulics Lawren Sack1 and N. Michele Holbrook2 1 Department of Botany, University of Hawai influence rates of transpiration and photosynthesis. Leaf hydraulic conductance (Kleaf) varies more than 65. #12;Contents INTRODUCTION. . . . . . . . . . . . . . . . . 362 LEAF HYDRAULIC CONDUCTANCE

Sack, Lawren

214

STEM crisis or STEM surplus?  

E-print Network

The science, technology, engineering, and mathematics (STEM) workforce is a crucial driver of the U.S. economy. Over the last decade, there has been significant concern regarding the adequacy of the supply of STEM workers ...

Xue, Yi, S.M. Massachusetts Institute of Technology

2014-01-01

215

TEMPERATURE INFLUENCE ON POTATO LEAF AND BRANCH DISTRIBUTION AND CANOPY PHOTOSYNTHETIC RATE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mature potato (Solanum tuberosum cv. Kennebec) canopies are composed of leaves originating from main stem and axillary stem branches. Canopy leaf distribution and corresponding contribution to whole canopy photosynthetic rates has not been quantified. An experiment using six Soil-Plant-Atmospheric...

216

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

217

LEAF MARGIN INFLORESCENCE  

E-print Network

image. Consider submitting multiple images, each one focused ILLUSTRATION OFTHEVARIOUS PLANT PARTS USED{ LEAF BLADE LEAF MARGIN PETIOLE INFLORESCENCE WS-27-W Guidelines for Submitting Digital Plant Assistant Professor of Weed Science Purdue University The accuracy of identifying a plant from digital

Holland, Jeffrey

218

The Novel Free Radical Scavenger, Edaravone, Increases Neural Stem Cell Number Around the Area of Damage Following Rat Traumatic Brain Injury  

Microsoft Academic Search

Edaravone is a novel free radical scavenger that is clinically employed in patients with acute cerebral infarction, but has\\u000a not previously been used to treat traumatic brain injury (TBI). In this study, we investigated the effect of edaravone administration\\u000a on rat TBI. In particular, we used immunohistochemistry to monitor neural stem cell (NSC) proliferation around the area damaged\\u000a by TBI.

Tatsuki Itoh; Takao Satou; Shozo Nishida; Masahiro Tsubaki; Shigeo Hashimoto; Hiroyuki Ito

2009-01-01

219

Impact of plant architecture versus leaf quality on attack by leaf-tying caterpillars on five oak species.  

PubMed

Because shelter-building herbivorous insect species often consider structural features of their host plants in selecting construction sites, their probability of attack is likely to be a function of some combination of plant architectural traits and leaf quality factors. We tested the hypothesis that plant architecture, in the form of the number of touching leaves, influences interspecific variation in attack by leaf-tying caterpillars in five species of sympatric Missouri oaks (Quercus). We compared colonization on control branches, in which both architecture and leaf quality were potentially important, with colonization on experimental branches for which we controlled for the effects of architecture by creating equal numbers of artificial ties. Colonization of artificial ties was highly correlated with natural colonization on neighboring control branches, suggesting that leaf quality factors and not architecture influenced interspecific variation in attack by leaf-tying caterpillars. Of the leaf quality factors measured (water, protein-binding capacity, nitrogen, specific leaf area, pubescence, and toughness), nitrogen was the most explanatory. With the exception of white oak, natural leaf tie colonization was positively correlated with nitrogen availability (ratio of nitrogen to protein-binding capacity), and negatively correlated with protein-binding capacity of leaf extracts. Both host plant species and subgenus oak influenced the community composition of leaf-tying caterpillars and the non-tying symbionts colonizing the ties. Host plant differences in leaf nitrogen content were positively correlated with pupal weight of one of two caterpillar species reared on all five host plant species. Thus, interspecific differences in nitrogen, nitrogen availability, and protein-binding capacity of leaf extracts are the best predictors at this time of interspecific differences in attack by leaf-tying caterpillars, in turn affecting their success on individual host plants in the laboratory. PMID:19960353

Marquis, Robert J; Lill, John T

2010-05-01

220

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

PubMed

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

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

2013-02-12

221

Leaf-wax n-alkanes record the plantwater 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. PMID:23359675

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

2013-01-01

222

[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

223

Short communication Leaf optical properties and photosynthetic leaf absorptances  

E-print Network

Short communication Leaf optical properties and photosynthetic leaf absorptances in several-species variability in the leaf optical properties of eight large-bodied seagrasses, Posidonia australis, Posidonia of Australia. Leaf spectral transmittance [TL(l)], reflectance [RL(l)], and non-photosynthetic absorptance [AL

Durako, Michael J.

224

Global Leaf Trait Relationships: Mass, Area, and the Leaf  

E-print Network

Global Leaf Trait Relationships: Mass, Area, and the Leaf Economics Spectrum Jeanne L. D. Osnas,1,2 * Jeremy W. Lichstein,2 Peter B. Reich,3,4 Stephen W. Pacala1 The leaf economics spectrum (LES) describes multivariate correlations that constrain leaf traits of plant species primarily to a single axis of variation

Minnesota, University of

225

Autophagy in stem cells  

PubMed Central

Autophagy is a highly conserved cellular process by which cytoplasmic components are sequestered in autophagosomes and delivered to lysosomes for degradation. As a major intracellular degradation and recycling pathway, autophagy is crucial for maintaining cellular homeostasis as well as remodeling during normal development, and dysfunctions in autophagy have been associated with a variety of pathologies including cancer, inflammatory bowel disease and neurodegenerative disease. Stem cells are unique in their ability to self-renew and differentiate into various cells in the body, which are important in development, tissue renewal and a range of disease processes. Therefore, it is predicted that autophagy would be crucial for the quality control mechanisms and maintenance of cellular homeostasis in various stem cells given their relatively long life in the organisms. In contrast to the extensive body of knowledge available for somatic cells, the role of autophagy in the maintenance and function of stem cells is only beginning to be revealed as a result of recent studies. Here we provide a comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells. We discuss how recent studies of different knockout mice models have defined the roles of various autophagy genes and related pathways in the regulation of the maintenance, expansion and differentiation of various stem cells. We also highlight the many unanswered questions that will help to drive further research at the intersection of autophagy and stem cell biology in the near future. PMID:23486312

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

2013-01-01

226

A Thermistor Leaf Thermometer  

PubMed Central

An instrument is described which allows measurements of leaf temperature within about 0.3 C. It consists of a special thermistor probe, a small circuit box, and a standard ammeter. The circuit box can easily be fixed to the meter and contains a battery, which passes 0.3 milliampere through the thermistor, and also contains an integrated circuit amplifier, so that the meter reads 20 C full scale deflection, with ranges adjustable in 10 C steps. Calibration experiments show the superiority of the thermistor leaf thermometer to a thermocouple pressed onto a rubber surface with a resilience resembling that of a leaf. Images PMID:16657432

Linacre, E. T.; Harris, W. J.

1970-01-01

227

Four-Leaf Clover  

NSDL National Science Digital Library

Scientist-in-training Summer Praetorius has an unusual skillshe 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 observationa skill Praetorius uses to spot tiny shelled animals called foraminiferaand 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

228

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

PubMed Central

The objective of this work is to investigate the relationship between endo-?-mannanase and leaf abscission, and response to wounding in soybean (Glycine max). An endo-?-mannanase gene GmMAN1 was cloned from the abscission zone in petiole explants, and was heterologously expressed in E. coli. Polyclonal antibodies were raised against the fusion protein. The increases in activity, isoform numbers, and amounts of transcripts and proteins of GmMAN1 were found not only in the abscission zone but also in the non-abscission zone during petiole abscission in the explants, but not in these two tissues during leaf abscission artificially induced by ethephon treatment in the intact plants. The changes in endo-?-mannanase expression patterns in these two tissues were probably induced by the inherent mechanical wounding during the preparation of explants. When soybean plants were wounded by removing half of the leaf blade of the first pair of true leaves, the transcripts and proteins of GmMAN1 were induced in the leaves and stem, leading to the increases in enzyme activity and isoform numbers in them. It is concluded that the soybean endo-?-mannanase GmMAN1 is not associated with leaf abscission, but might be involved in the response to wounding. PMID:23173047

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

2012-01-01

229

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

230

Cell Stem Cell Clinical Progress  

E-print Network

, 2009), low cell numbers in single UCB units have limited the suitability of UCB transplan- tationCell Stem Cell Clinical Progress Rapid Expansion of Human Hematopoietic Stem Cells by Automated, Toronto, ON M5S 3E1, Canada 4Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins

Zandstra, Peter W.

231

Relationships between leaf pigment content and spectral reflectance across a wide range of species, leaf structures and developmental stages  

Microsoft Academic Search

Leaf pigment content can provide valuable insight into the physiological performance of leaves. Measurement of spectral reflectance provides a fast, nondestructive method for pigment estimation. A large number of spectral indices have been developed for estimation of leaf pigment content. However, in most cases these indices have been tested for only one or at most a few related species and

Daniel A. Sims; John A. Gamon

2002-01-01

232

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

233

Leaf Tissue Senescence  

PubMed Central

During winter, excised leaf tissue from Rumex obtusifolius degrades chlorophyll at twice the summer rate but the plant hormones, gibberellic acid and zeatin, inhibit the senescence rate by a constant percentage, regardless of season. PMID:16659225

Manos, Peter J.; Goldthwaite, Jonathan

1975-01-01

234

Human Embryonic Stem Cell Registry  

NSDL National Science Digital Library

The National Institutes of Health (NIH) has recently released the Human Embryonic Stem Cell Registry in response to the President's announcement on August 9, 2001 to allow federal funds for stem cell research. The site lists the eleven laboratories or companies that meet the specific criteria for approved stem cell lines and explains the criteria themselves. The NIH gives the number of actual lines for each entity, the NIC and providers code for each, as well as contact information. The Website also provides links to those seeking additional information about NIH stem cell information, grants and funding opportunities, technology transfer issues, and further facts about the NIH.

2001-01-01

235

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; Lo Niinemets; Matthew J. Germino

236

Chloroplast to Leaf  

Microsoft Academic Search

\\u000a Leaf shapes and morphologies are very diverse. Obviously there are many successful solutions to the challenge of constructing\\u000a an organ that intercepts light, enables CO2 uptake, restricts water loss, and withstands or avoids temperature extremes, herbivory, and disease. Tradeoffs exist among\\u000a capturing CO2 and light, water loss, or construction cost. So, to some extent, the various leaf structures represent different

John R. Evans; Ichiro Terashima; Yuko Hanba; Francesco Loreto

237

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; lo Niinemets

238

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

239

Photosynthetic and growth responses of two broad-leaf tree species to irrigation with municipal landfill leachate  

Microsoft Academic Search

A study was undertaken to investigate leaf photosynthesis and stem growth responses of saplings of two broad-leaf tree species to irrigation with municipal solid waste (MSW) leachate in a northern temperate climate at Ontario, Canada. The objective was to quantify plant stresses or changes in plant productivity that could be attributed to this low technology option for the treatment and

S. C. Shrive; R. A. McBride; A. M. Gordon

1994-01-01

240

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

Microsoft Academic Search

BACKGROUND: An increased understanding of leaf area development is important in a number of fields: in food and non-food crops, for example short rotation forestry as a biofuels feedstock, leaf area is intricately linked to biomass productivity; in paleontology leaf shape characteristics are used to reconstruct paleoclimate history. Such fields require measurement of large collections of leaves, with resulting conclusions

Max Bylesj; Vincent Segura; Raju Y Soolanayakanahally; Anne M Rae; Johan Trygg; Petter Gustafsson; Stefan Jansson

2008-01-01

241

FPT Algorithms and Kernels for the Directed k-Leaf Problem  

E-print Network

FPT Algorithms and Kernels for the Directed k-Leaf Problem Jean Daligault , Gregory Gutin , Eun-degree zero are leaves. In the Directed Max Leaf Problem, we wish to find the maximum number of leaves in an out-branching of a given digraph D (or, to report that D has no out-branching). In the Directed k-Leaf

Paris-Sud XI, Université de

242

STEM Thinking!  

ERIC Educational Resources Information Center

Science, Technology, Engineering, and Mathematics (STEM) is a term seen almost daily in the news. In 2009, President Obama launched the Educate to Innovate initiative to move American students from the middle to the top of the pack in science and math achievement over the next decade (The White House, n.d.). Learning about the attributes of STEM

Reeve, Edward M.

2015-01-01

243

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

244

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

PubMed

A microdilution technique for the assessment of in vitro activity against Entamoeba histolytica was devised and validated with metronidazole. The test was used to detect the antiamoebic activities of plant extracts prepared from the traditional remedies Brucea javanica fruits and Simarouba amara stems. The activity was associated with quassinoid-containing fractions. The 50% inhibitory concentrations for some quassinoids against amoebae were determined by using the microdilution method. These concentrations ranged from 0.019 micrograms.ml-1 for bruceantin, the most active quassinoid, to greater than 5 micrograms.ml-1 for glaucarubol, the least active compound tested. These results are discussed with reference to the known activities of these compounds against Plasmodium falciparum. Overall, the activities of the quassinoids against both protozoa are similar. The microdilution technique will be useful in the search for novel antiamoebic drugs. PMID:2908094

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

1988-11-01

245

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

PubMed Central

A microdilution technique for the assessment of in vitro activity against Entamoeba histolytica was devised and validated with metronidazole. The test was used to detect the antiamoebic activities of plant extracts prepared from the traditional remedies Brucea javanica fruits and Simarouba amara stems. The activity was associated with quassinoid-containing fractions. The 50% inhibitory concentrations for some quassinoids against amoebae were determined by using the microdilution method. These concentrations ranged from 0.019 micrograms.ml-1 for bruceantin, the most active quassinoid, to greater than 5 micrograms.ml-1 for glaucarubol, the least active compound tested. These results are discussed with reference to the known activities of these compounds against Plasmodium falciparum. Overall, the activities of the quassinoids against both protozoa are similar. The microdilution technique will be useful in the search for novel antiamoebic drugs. PMID:2908094

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

1988-01-01

246

STEM At Work  

NSDL National Science Digital Library

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

2011-03-17

247

BOREAS TE-9 NSA Leaf Chlorophyll Density  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

248

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

PubMed

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

Terfa, Meseret Tesema; Solhaug, Knut Asbjrn; Gislerd, Hans Ragnar; Olsen, Jorunn Elisabeth; Torre, Sissel

2013-05-01

249

Sapwood Area as an Estimator of Leaf Area and Foliar Weight in Cherrybark Oak and Green Ash  

Microsoft Academic Search

The relationships between foliar weight\\/leaf area and four stem dimensions (dbh, total stem cross-sectional area, total sapwood area, and current sapwood area at breast height) were investigated in two important bottomland tree species of the southern United States, cherrybark oak (Quercus falcata var. pagodifolia EN.) and green ash (fraxinus pennsylvanica Marsh.). In all models tested and for both species, total

James S. Meadows; John D. Hodges

250

LEAF-E: a tool to analyze grass leaf growth using function fitting.  

PubMed

In grasses, leaf growth is often monitored to gain insights in growth processes, biomass accumulation, regrowth after cutting, etc. To study the growth dynamics of the grass leaf, its length is measured at regular time intervals to derive the leaf elongation rate (LER) profile over time. From the LER profile, parameters such as maximal LER and leaf elongation duration (LED), which are essential for detecting inter-genotype growth differences and/or quantifying plant growth responses to changing environmental conditions, can be determined. As growth is influenced by the circadian clock and, especially in grasses, changes in environmental conditions such as temperature and evaporative demand, the LER profiles show considerable experimental variation and thus often do not follow a smooth curve. Hence it is difficult to quantify the duration and timing of growth. For these reasons, the measured data points should be fitted using a suitable mathematical function, such as the beta sigmoid function for leaf elongation. In the context of high-throughput phenotyping, we implemented the fitting of leaf growth measurements into a user-friendly Microsoft Excel-based macro, a tool called LEAF-E. LEAF-E allows to perform non-linear regression modeling of leaf length measurements suitable for robust and automated extraction of leaf growth parameters such as LER and LED from large datasets. LEAF-E is particularly useful to quantify the timing of leaf growth, which forms an important added value for detecting differences in leaf growth development. We illustrate the broad application range of LEAF-E using published and unpublished data sets of maize, Miscanthus spp. and Brachypodium distachyon, generated in independent experiments and for different purposes. In addition, we show that LEAF-E could also be used to fit datasets of other growth-related processes that follow the sigmoidal profile, such as cell length measurements along the leaf axis. Given its user-friendliness, ability to quantify duration and timing of leaf growth and broad application range, LEAF-E is a tool that could be routinely used to study growth processes following the sigmoidal profile. PMID:25435898

Voorend, Wannes; Lootens, Peter; Nelissen, Hilde; Roldn-Ruiz, Isabel; Inz, Dirk; Muylle, Hilde

2014-01-01

251

Living in the Leaf Litter  

NSDL National Science Digital Library

This online article, from the museum's Musings newsletter for educators, provides some mind-boggling facts about leaf litter. It has an overview of what leaf litter is and how it's produced and a link for further research.

252

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. PMID:18725291

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

2008-01-01

253

The triple oxygen isotope composition of leaf waters in Mpala, central Kenya  

NASA Astrophysics Data System (ADS)

The triple oxygen isotopic composition of water is an emerging tool for investigating the hydrological environment. The ?18O-?17O relationship differs during kinetic and equilibrium isotope fractionation, such that the 17O depletion can be sensitive to relative humidity (Rh) during kinetic fractionation, mixing among different pools, and to the specific mode of kinetic fractionation. It has been proposed that the ?18O-?17O relationship during evapotranspiration, as characterized by the slope ?(stem-leaf) on a ln(?17O+1) vs. ln(?18O+1) plot, is mainly controlled by Rh but not affected by other environmental conditions or by plant species. In order to understand the sensitivity of ?(stem-leaf) to Rh and the utility of 17O-excess (the deviation of ?17O from a reference slope) in the terrestrial biosphere as a tracer of Rh conditions today and in the past, this study expands the triple oxygen isotope measurements of leaf waters to additional species in a semiarid environment. Paired stem and leaf waters of Acacia and grasses were collected in the Mpala Research Center in central Kenya and analyzed for their triple oxygen isotope composition. Leaf waters that were sampled diurnally (8 sampling intervals between 6 am and 5 pm) exhibit a range in ?18O and 17O-excess values of 11.2 and 107 per meg respectively for Acacia brevispica, and 14.4 and 147 per meg for the grass Panicum maximum. Except for one sample collected at 7am, the ?(stem-leaf) values for grasses are systematically lower (0.0012 to 0.0110) than Acacia ?(stem-leaf) values at the corresponding time of day; this might be explained by the progressive evaporative isotopic enrichment and mixing processes of leaf water along parallel veins of grass leaves. Most of the triple oxygen isotope composition of the Acacia leaf waters can be predicted using Craig-Gordon model. We built a mass balance model of an evolving leaf water system from nonsteady-state to steady-state conditions during evapotranspiration to explain the diurnal 17O-excess variation of the Acacia leaf waters. The results from this model indicate that 17O-excess of the leaf waters may be affected by variations in stomatal conductance, leaf water volume, and water residence time, in addition to variations in Rh. Our study emphasizes that the triple oxygen isotope composition of leaf waters is controlled both physically by Rh conditions but also by the physiological responses of a plant to its environment. The triple oxygen isotope composition of grass leaf water is a result of both evapotranspiration and mixing processes, and thus species effects should be considered in the discussion of ?(stem-leaf)-Rh relationships. A better understanding of the ?(stem-leaf)-Rh relationships could provide a framework for interpreting variations of triple oxygen isotopes of tree cellulose or fossil tissues as proxies for paleo-hydrological change.

Li, S.; Levin, N.; Soderberg, K.; Dennis, K. J.; Caylor, K. K.

2013-12-01

254

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

255

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

256

LSD: a leaf senescence database  

PubMed Central

By broad literature survey, we have developed a leaf senescence database (LSD, http://www.eplantsenescence.org/) that contains a total of 1145 senescence associated genes (SAGs) from 21 species. These SAGs were retrieved based on genetic, genomic, proteomic, physiological or other experimental evidence, and were classified into different categories according to their functions in leaf senescence or morphological phenotypes when mutated. We made extensive annotations for these SAGs by both manual and computational approaches, and users can either browse or search the database to obtain information including literatures, mutants, phenotypes, expression profiles, miRNA interactions, orthologs in other plants and cross links to other databases. We have also integrated a bioinformatics analysis platform WebLab into LSD, which allows users to perform extensive sequence analysis of their interested SAGs. The SAG sequences in LSD can also be downloaded readily for bulk analysis. We believe that the LSD contains the largest number of SAGs to date and represents the most comprehensive and informative plant senescence-related database, which would facilitate the systems biology research and comparative studies on plant aging. PMID:21097471

Liu, Xiaochuan; Li, Zhonghai; Jiang, Zhiqiang; Zhao, Yi; Peng, Jinying; Jin, Jinpu; Guo, Hongwei; Luo, Jingchu

2011-01-01

257

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. PMID:22212121

Abraham-Shrauner, Barbara; Pickard, Barbara G

2011-01-01

258

Bacterial leaf spot  

Technology Transfer Automated Retrieval System (TEKTRAN)

Bacterial leaf spot has been reported in Australia (Queensland), Egypt, El Salvador, India, Japan, Nicaragua, Sudan, and the United States (Florida, Iowa, Kansas, Maryland, and Wisconsin). It occasionally causes locally severe defoliation and post-emergence damping-off and stunting. The disease is...

259

Science Nation: Leaf Sensor  

NSDL National Science Digital Library

Who might know more about what a plant needs than a farmer or a greenhouse owner? How about the plant itself? What if plants could tell us when they are thirsty? With funding from the National Science Foundation (NSF), AgriHouse has developed a leaf sensor that is enabling plants to do just that.

260

The enigma of effective pathlength for 18O enrichment in leaf water of conifers  

NASA Astrophysics Data System (ADS)

The stable isotopes of oxygen (?18O) in tree ring cellulose provide valuable proxy information about past environments and climate. Mechanistic models have been used to clarify the important drivers of isotope fractionation and help interpret ?18O variation in tree rings. A critical component to these models is an estimate of leaf water enrichment. However, standard models seldom accurately predict 18O enrichment in conifer needles and Pclet corrections often require effective pathlengths (L) that seem unreasonable from the perspective of needle morphology (>0.5 m). To analyze the potential role of path length on the Pclet effect in conifers we carried out experiments in controlled environment chambers. We exposed seedlings of six species of conifer (Abies alba, Larix decidua, Picea abies, Pinus cembra, P. sylvestris, Taxus bacata), that differ in needle morphology, to four different vapor pressure deficits (VPD), in order to modify transpiration rates (E) and leaf water 18O enrichment. Environmental and ?18O data (leaf, stem and chamber water vapor) were collected to parameterize leaf water models. Cross-sections of needles were sampled for an analysis of needle anatomy. Conifer needles have a single strand of vascular tissue making pathlength determinations through anatomical assessments possible. The six species differed in mesophyll distance (measured from endodermis to epidermis) and cell number, with Pinus and Picea species having the shortest distance and Abies and Taxus the longest (flat needle morphology). Other anatomical measures (transfusion distance, cell size etc.) did not differ significantly. A suberized strip was apparent in the endodermis of all species except Taxus and Abies. Conifer needles have a large proportion (from 0.2 to 0.4) of needle cross-sectional area in vascular tissues that may not be subject to evaporative enrichment. As expected, leaf water ?18O and E responded strongly to VPD and standard models (Craig-Gordon) overestimated leaf water ?18O. A single species-specific value for L could not be determined as the fractional difference between modeled and measured leaf water ?18O did not increase with E as theory predicts. Accounting for potentially unenriched water in vascular and transfusion tissues as well as a Pclet correction that allows the value for L to change with E (as in Song et al., 2013) produced accurate predictions of leaf water ?18O. Estimates of L (for a given E) were positively correlated with mean mesophyll thickness, which to our knowledge is the first time L has been related to a leaf anatomical measure. We repeated the experiment using young needles with much higher values for E, and found a continuing trend of reduced fractional difference with E, implying that Pclet corrections may need to be modified to predict conifer needle water over the range of needle phenology and physiology. Our study will help to better quantify effective pathlength and needle water ?18O in conifers, which are some of the most important organisms used for paleoclimate reconstruction.

Roden, J. S.; Kahmen, A.; Buchmann, N. C.; Siegwolf, R. T.

2013-12-01

261

Adult skeletal muscle stem cells.  

PubMed

Skeletal muscles in vertebrates have a phenomenal regenerative capacity. A muscle that has been crushed can regenerate fully both structurally and functionally within a month. Remarkably, efficient regeneration continues to occur following repeated injuries. Thousands of muscle precursor cells are needed to accomplish regeneration following acute injury. The differentiated muscle cells, the multinucleated contractile myofibers, are terminally withdrawn from mitosis. The source of the regenerative precursors is the skeletal muscle stem cells-the mononucleated cells closely associated with myofibers, which are known as satellite cells. Satellite cells are mitotically quiescent or slow-cycling, committed to myogenesis, but undifferentiated. Disruption of the niche after muscle damage results in their exit from quiescence and progression towards commitment. They eventually arrest proliferation, differentiate, and fuse to damaged myofibers or make de novo myofibers. Satellite cells are one of the well-studied adult tissue-specific stem cells and have served as an excellent model for investigating adult stem cells. They have also emerged as an important standard in the field of ageing and stem cells. Several recent reviews have highlighted the importance of these cells as a model to understand stem cell biology. This chapter begins with the discovery of satellite cells as skeletal muscle stem cells and their developmental origin. We discuss transcription factors and signalling cues governing stem cell function of satellite cells and heterogeneity in the satellite cell pool. Apart from satellite cells, a number of other stem cells have been shown to make muscle and are being considered as candidate stem cells for amelioration of muscle degenerative diseases. We discuss these "offbeat" muscle stem cells and their status as adult skeletal muscle stem cells vis-a-vis satellite cells. The ageing context is highlighted in the concluding section. PMID:25344672

Sambasivan, Ramkumar; Tajbakhsh, Shahragim

2015-01-01

262

Leaf drop in evergreen Ceanothus velutinus as a means of reducing herbivory.  

PubMed

Conventional explanations for deciduousness do not include losses to herbivory. However, a recent explanation posits that deciduous leaf drop allows trees to reduce their herbivore loads and that this benefit of the deciduous habit may partly offset lost opportunities for photosynthesis. Much of the damage caused by chewing herbivores occurs early in the season when adult insects colonize as new leaves are expanding; trees without leaves from previous leaf flushes at this time are less attractive and suffer less cost of herbivory. I tested this hypothesis using Ceanothus velutinus, an evergreen shrub that shows considerable individual variation in leaf retention. Stems that held more leaves through winter experienced more chewing damage the following season. Stems with leaves experimentally removed through winter also were less likely to receive chewing damage the following season. At least some herbivores in this system make oviposition decisions before new leaves have expanded, and old leaves may provide cues about the suitability of the stem. Holding leaves through winter increased the likelihood of herbivory, and experimental protection from herbivores caused 60% greater inflorescence production compared to unprotected stems. However, the cost of leaf retention was more than offset by an overall benefit. Stems that were allowed to keep winter leaves produced larger new leaves in summer and expanded them more rapidly in the season than stems with winter leaves experimentally removed. As a result, stems with leaves through winter experienced higher survival, four times as many inflorescences, and 40 times as many fruits as shoots that were experimentally defoliated. Losses to herbivores may be an unappreciated cost of leaf retention, and cost-benefit models of deciduous and evergreen behavior should include these losses. PMID:18831166

Karban, Richard

2008-09-01

263

Mesenchymal Stem Cells and Tissue Engineering  

Microsoft Academic Search

Mesenchymal stem cells (MSCs) have become one of the most studied stem cells, especially toward the healing of diseased and damaged tissues and organs. MSCs can be readily isolated from a number of adult tissues by means of minimally invasive approaches. MSCs are capable of self?replication to many passages and, therefore, can potentially be expanded to sufficient numbers for tissue

Nicholas W. Marion; Jeremy J. Mao

2006-01-01

264

LEAF GUI: User Manual (Leaf Extraction and Analysis Framework Graphical User Interface)  

E-print Network

LEAF GUI: User Manual (Leaf Extraction and Analysis Framework Graphical User Interface) #12;LEAF GUI User Manual Price et al. Index How to cite the LEAF GUI......................................................................................................................Page 28 2 #12;LEAF GUI User Manual Price et al. How to cite the LEAF GUI The LEAF GUI

Weitz, Joshua S.

265

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

PubMed Central

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

Surez, N.

2010-01-01

266

Extinction models for cancer stem cell therapy  

PubMed Central

Cells with stem cell-like properties are now viewed as initiating and sustaining many cancers. This suggests that cancer can be cured by driving these cancer stem cells to extinction. The problem with this strategy is that ordinary stem cells are apt to be killed in the process. This paper sets bounds on the killing differential (difference between death rates of cancer stem cells and normal stem cells) that must exist for the survival of an adequate number of normal stem cells. Our main tools are birthdeath Markov chains in continuous time. In this framework, we investigate the extinction times of cancer stem cells and normal stem cells. Application of extreme value theory from mathematical statistics yields an accurate asymptotic distribution and corresponding moments for both extinction times. We compare these distributions for the two cell populations as a function of the killing rates. Perhaps a more telling comparison involves the number of normal stem cells NH at the extinction time of the cancer stem cells. Conditioning on the asymptotic time to extinction of the cancer stem cells allows us to calculate the asymptotic mean and variance of NH. The full distribution of NH can be retrieved by the finite Fourier transform and, in some parameter regimes, by an eigenfunction expansion. Finally, we discuss the impact of quiescence (the resting state) on stem cell dynamics. Quiescence can act as a sanctuary for cancer stem cells and imperils the proposed therapy. We approach the complication of quiescence via multitype branching process models and stochastic simulation. Improvements to the ?-leaping method of stochastic simulation make it a versatile tool in this context. We conclude that the proposed therapy must target quiescent cancer stem cells as well as actively dividing cancer stem cells. The current cancer models demonstrate the virtue of attacking the same quantitative questions from a variety of modeling, mathematical, and computational perspectives. PMID:22001354

Sehl, Mary; Zhou, Hua; Sinsheimer, Janet S.; Lange, Kenneth L.

2012-01-01

267

The potential of biomonitoring of air quality using leaf characteristics of white willow ( Salix alba L.)  

Microsoft Academic Search

In this study, we assess the potential of white willow (Salix alba L.) as bioindicator for monitoring of air quality. Therefore, shoot biomass, specific leaf area, stomatal density, stomatal\\u000a pore surface, and stomatal resistance were assessed from leaves of stem cuttings. The stem cuttings were introduced in two\\u000a regions in Belgium with a relatively high and a relatively low level

Tatiana Wuytack; Kris Verheyen; Karen Wuyts; Fatemeh Kardel; Sandy Adriaenssens; Roeland Samson

2010-01-01

268

Leaf absorbance and photosynthesis  

NASA Technical Reports Server (NTRS)

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 necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Schurer, Kees

1994-01-01

269

Variable depth recursion algorithm for leaf sequencing  

SciTech Connect

The processes of extraction and sweep are basic segmentation steps that are used in leaf sequencing algorithms. A modified version of a commercial leaf sequencer changed the way that the extracts are selected and expanded the search space, but the modification maintained the basic search paradigm of evaluating multiple solutions, each one consisting of up to 12 extracts and a sweep sequence. While it generated the best solutions compared to other published algorithms, it used more computation time. A new, faster algorithm selects one extract at a time but calls itself as an evaluation function a user-specified number of times, after which it uses the bidirectional sweeping window algorithm as the final evaluation function. To achieve a performance comparable to that of the modified commercial leaf sequencer, 2-3 calls were needed, and in all test cases, there were only slight improvements beyond two calls. For the 13 clinical test maps, computation speeds improved by a factor between 12 and 43, depending on the constraints, namely the ability to interdigitate and the avoidance of the tongue-and-groove under dose. The new algorithm was compared to the original and modified versions of the commercial leaf sequencer. It was also compared to other published algorithms for 1400, random, 15x15, test maps with 3-16 intensity levels. In every single case the new algorithm provided the best solution.

Siochi, R. Alfredo C. [Department of Radiation Oncology, University of Iowa, 200 Hawkins Street, Iowa City, Iowa 52240 (United States)

2007-02-15

270

Co-ordination between Leaf Initiation and Leaf Appearance in Field-grown Maize (Zea mays): Genotypic Differences in Response of Rates to Temperature  

PubMed Central

Background and Aims In maize (Zea mays), early flowering date, which is a valuable trait for several cropping systems, is associated with the number of leaves per plant and the leaf appearance rate. Final leaf number depends upon the rate and duration of leaf initiation. The aims of this study were to analyse the genotypic variation in the response to temperature of leaf appearance rate and leaf initiation rate, and to investigate the co-ordination between these processes under field conditions. Methods Sixteen hybrids of different origins were grown under six contrasting environmental conditions. The number of appeared leaves was measured twice a week to estimate leaf appearance rate (leaves d?1). Plants were dissected at four sampling dates to determine the number of initiated leaves and estimate leaf initiation rate (leaves d?1). A co-ordination model was fitted between the number of initiated leaves and the number of appeared leaves. This model was validated using two independent data sets. Key Results Significant (P < 005) differences were found among hybrids in the response to temperature of leaf initiation rate (plastochron) and leaf appearance rate (phyllochron). Plastochron ranged between 243 and 364 degree days (Cd), with a base temperature (Tb) between 40 and 82?C. Phyllochron ranged between 486 and 655?Cd, with a Tb between 29 and 50?C. A single co-ordination model was fitted between the two processes for all hybrids and environments (r2 = 096, P < 00001), and was successfully validated (coefficient of variation < 9 %). Conclusions This work has established the existence of genotypic variability in leaf initiation rate and leaf appearance rate in response to temperature, which is a promising result for maize breeding; and the interdependence between these processes from seedling emergence up to floral initiation. PMID:16126778

PADILLA, J. M.; OTEGUI, M. E.

2005-01-01

271

ETIOLOGY AND HOST RANGE OF A CLOSTEROVIRUS ASSOCIATED WITH PLUM BARK NECROSIS-STEM PITTING DISEASE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Diseased plum (Prunus salicina) cv. Black Beaut trees developed stem gumming, severe bark necrosis, and stem pitting symptoms on the woody cylinder of the main trunk and scaffold branches. The sucker shoots of the peach (Prunus persica) cv. Nemaguard understocks exhibited oak-leaf patterns, but lack...

272

High Number of Memory T Cells Is Associated with Higher Risk of Acute Graft-versus-Host Disease after Allogeneic Stem Cell Transplantation.  

PubMed

The pathophysiology of acute graft-versus-host disease (GVHD) remains poorly understood in humans. Although T cell subsets have been identified to play a major role in disease initiation in rodents, clinical data on the effect of these different subsets are scarce and conflicting. To address this question, immunophenotyping analyses were performed on the graft in 210 patients. The onset of acute GVHD was retrospectively correlated with these subpopulations. In an adjusted analysis, only the absolute count of CD45lo/CD62Llo CD8(+) T cells (effector memory T cells) was significantly associated with the onset of grade 2 to 4 acute GVHD. Thus, in contrast to experimental data, we found that the number of effector memory but not of nave T cells was associated with the onset of GVHD. These results should be kept in mind while clinical trials, which aim to deplete nave T cells, are underway in several institutions. PMID:25528387

Loschi, Michael; Porcher, Raphael; Peffault de Latour, Regis; Vanneaux, Valerie; Robin, Marie; Xhaard, Alienor; Sicre de Fontebrune, Flore; Larghero, Jerome; Socie, Gerard

2015-03-01

273

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

274

Dormancy in the stem cell niche.  

PubMed

Tissues characterized by constant turnover contain post-mitotic, terminally differentiated cells originating from highly proliferative progenitors, which in turn derive from a relatively small population of stem cells. At the population level, self-renewal and differentiation are the possible outcomes of stem cell proliferation; overall, however, stem cells are quiescent if compared with their direct progeny. The recent discovery of a particularly quiescent, or dormant, subpopulation of hematopoietic stem cells (HSCs) raises a number of fundamental questions. As stem cell fate is influenced by the signals integrated by the stem cell niche, will dormant HSCs reside in specific dormant niches? Is the mechanism of dormancy common to multiple regenerating tissues or specific to the hematopoietic system? If cancer is maintained by a few cancer stem cells, do they also contain a subpopulation of dormant cells, and could this be exploited for therapeutic purposes? PMID:22429750

Sottocornola, Roberta; Lo Celso, Cristina

2012-01-01

275

Dormancy in the stem cell niche  

PubMed Central

Tissues characterized by constant turnover contain post-mitotic, terminally differentiated cells originating from highly proliferative progenitors, which in turn derive from a relatively small population of stem cells. At the population level, self-renewal and differentiation are the possible outcomes of stem cell proliferation; overall, however, stem cells are quiescent if compared with their direct progeny. The recent discovery of a particularly quiescent, or dormant, subpopulation of hematopoietic stem cells (HSCs) raises a number of fundamental questions. As stem cell fate is influenced by the signals integrated by the stem cell niche, will dormant HSCs reside in specific dormant niches? Is the mechanism of dormancy common to multiple regenerating tissues or specific to the hematopoietic system? If cancer is maintained by a few cancer stem cells, do they also contain a subpopulation of dormant cells, and could this be exploited for therapeutic purposes? PMID:22429750

2012-01-01

276

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

277

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

PubMed Central

The Cellulose Synthase-Like D (CslD) genes have important, although still poorly defined, roles in cell wall formation. Here, we show an unexpected involvement of CslD1 from maize (Zea mays) in cell division. Both division and expansion were altered in the narrow-organ and warty phenotypes of the csld1 mutants. Leaf width was reduced by 35%, due mainly to a 47% drop in the number of cell files across the blade. Width of other organs was also proportionally reduced. In leaf epidermis, the deficiency in lateral divisions was only partially compensated by a modest, uniform increase in cell width. Localized clusters of misdivided epidermal cells also led to the formation of warty lesions, with cell clusters bulging from the epidermal layer, and some cells expanding to volumes 75-fold greater than normal. The decreased cell divisions and localized epidermal expansions were not associated with detectable changes in the cell wall composition of csld1 leaf blades or epidermal peels, yet a greater abundance of thin, dense walls was indicated by high-resolution x-ray tomography of stems. Cell-level defects leading to wart formation were traced to sites of active cell division and expansion at the bases of leaf blades, where cytokinesis and cross-wall formation were disrupted. Flow cytometry confirmed a greater frequency of polyploid cells in basal zones of leaf blades, consistent with the disruption of cytokinesis and/or the cell cycle in csld1 mutants. Collectively, these data indicate a previously unrecognized role for CSLD activity in plant cell division, especially during early phases of cross-wall formation. PMID:22123901

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

2012-01-01

278

Cell Stem Cell Stem Cell States, Fates,  

E-print Network

and Stem Cell Research, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, Lund SE-223 62, Sweden 4Lund Strategic Research Center for Stem Cell Biology and Cell Therapy, LundCell Stem Cell Review Stem Cell States, Fates, and the Rules of Attraction Tariq Enver,1 Martin

Peterson, Carsten

279

Stem cells, cancer, and cancer stem cells  

Microsoft Academic Search

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

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

2001-01-01

280

STEM Colorado: Random Walk  

NSDL National Science Digital Library

This applet demonstrates random walk in two dimensions. The user can specify how many particles appear at the center of the circle and the mean free path as a fraction of the radius of the circle. The path lengths are randomized with an exponential distribution. A histogram shows the number of times each particle has been deflected before it escapes the circle. It also shows the mean number of scatterings and the standard deviation. This is part of a larger collection of applets by STEM Colorado focused mostly on topics in astronomy.

Mccray, Richard; Koelemay, Andrew

2008-11-04

281

Stem cell therapy for osteoporosis.  

PubMed

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

Antebi, Ben; Pelled, Gadi; Gazit, Dan

2014-03-01

282

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.

283

Radiative characteristics of plant leaf  

Microsoft Academic Search

Existing leaf radiation models are reviewed. A new concept of the optical model of the leaf as a multiphase system containing\\u000a three aggregate ensembles of particles significantly different in microphysical and optical characteristics is proposed. The\\u000a proposed model is based on the reconstruction of the particle size distribution function from the experimental leaf absorption\\u000a spectrum. Based on the obtained microphysical

G. M. Krekov; M. M. Krekova; A. A. Lisenko; A. Ya. Sukhanov

2009-01-01

284

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

285

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 Snchez Alvarado

2007-01-01

286

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

287

Combining Leaf Salient Points and Leaf Contour Descriptions for Plant Species Recognition  

E-print Network

Combining Leaf Salient Points and Leaf Contour Descriptions for Plant Species Recognition Sofiene for plant species recognition, based on the leaf observation. We consider two sources of information: the leaf margin and the leaf salient points. For the leaf shape description, we investigate the shape

Verroust-Blondet, Anne

288

Seasonal changes in leaf area of Amazon forests from leaf flushing and abscission  

E-print Network

Seasonal changes in leaf area of Amazon forests from leaf flushing and abscission Arindam Samanta,1 as seasonal change in leaf area resulting from net leaf flushing in the dry season or net leaf abscission and as change in leaf scattering and absorption properties between younger and older leaves covered

Goldberg, Bennett

289

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 ?4C and maximum temperatures below 36C was investigated using plants under controlled conditions

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

1998-01-01

290

Estimating Corn Leaf Chlorophyll Concentration from Leaf and Canopy Reflectance  

Microsoft Academic Search

Farmers must balance the competing goals of supplying adequate N for their crops while minimizing N losses to the environment. To characterize the spatial variability of N over large fields, traditional methods (soil testing, plant tissue analysis, and chlorophyll meters) require many point samples. Because of the close link between leaf chlorophyll and leaf N concentration, remote sensing techniques have

C. S. T. Daughtry; C. L. Walthall; M. S. Kim; E. Brown de Colstoun; J. E. McMurtrey III

2000-01-01

291

Plasticity in sunflower leaf and cell growth under high salinity.  

PubMed

A group of sunflower lines that exhibit a range of leaf Na(+) concentrations under high salinity was used to explore whether the responses to the osmotic and ionic components of salinity can be distinguished in leaf expansion kinetics analysis. It was expected that at the initial stages of the salt treatment, leaf expansion kinetics changes would be dominated by responses to the osmotic component of salinity, and that later on, ion inclusion would impose further kinetics changes. It was also expected that differential leaf Na(+) accumulation would be reflected in specific changes in cell division and expansion rates. Plants of four sunflower lines were gradually treated with a relatively high (130mm NaCl) salt treatment. Leaf expansion kinetics curves were compared in leaves that were formed before, during and after the initiation of the salt treatment. Leaf areas were smaller in salt-treated plants, but the analysis of growth curves did not reveal differences that could be attributed to differential Na(+) accumulation, since similar changes in leaf expansion kinetics were observed in lines with different magnitudes of salt accumulation. Nevertheless, in a high leaf Na(+) -including line, cell divisions were affected earlier, resulting in leaves with proportionally fewer cells than in a Na(+) -excluding line. A distinct change in leaf epidermal pavement shape caused by salinity is reported for the first time. Mature pavement cells in leaves of control plants exhibited typical lobed, jigsaw-puzzle shape, whereas in treated plants, they tended to retain closer-to-circular shapes and a lower number of lobes. PMID:24942979

Cccoli, G; Bustos, D; Ortega, L I; Senn, M E; Vegetti, A; Taleisnik, E

2014-06-18

292

The role of gravity in leaf blade curvatures  

NASA Technical Reports Server (NTRS)

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

Hayes, A. B.

1984-01-01

293

BOREAS TE-5 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

294

7 CFR 29.6023 - Leaf structure.  

Code of Federal Regulations, 2011 CFR

...2 2011-01-01 2011-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture ...INSPECTION Standards Definitions 29.6023 Leaf structure. The cell development of a leaf as indicated by its...

2011-01-01

295

7 CFR 29.6023 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...2 2010-01-01 2010-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture ...INSPECTION Standards Definitions 29.6023 Leaf structure. The cell development of a leaf as indicated by its...

2010-01-01

296

7 CFR 29.6023 - Leaf structure.  

Code of Federal Regulations, 2013 CFR

...2 2013-01-01 2013-01-01 false Leaf structure. 29.6023 Section 29.6023...INSPECTION Standards Definitions 29.6023 Leaf structure. The cell development of a leaf as indicated by its porosity. The degrees...

2013-01-01

297

7 CFR 29.6022 - Leaf scrap.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2013-01-01

298

7 CFR 29.6023 - Leaf structure.  

...2 2014-01-01 2014-01-01 false Leaf structure. 29.6023 Section 29.6023...INSPECTION Standards Definitions 29.6023 Leaf structure. The cell development of a leaf as indicated by its porosity. The degrees...

2014-01-01

299

7 CFR 29.6022 - Leaf scrap.  

... 2014-01-01 2014-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2014-01-01

300

7 CFR 29.2529 - Leaf scrap.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2010-01-01

301

7 CFR 29.6022 - Leaf scrap.  

Code of Federal Regulations, 2012 CFR

... 2012-01-01 2012-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2012-01-01

302

7 CFR 29.6022 - Leaf scrap.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2010-01-01

303

7 CFR 29.2529 - Leaf scrap.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2013-01-01

304

7 CFR 29.6023 - Leaf structure.  

Code of Federal Regulations, 2012 CFR

...2 2012-01-01 2012-01-01 false Leaf structure. 29.6023 Section 29.6023...INSPECTION Standards Definitions 29.6023 Leaf structure. The cell development of a leaf as indicated by its porosity. The degrees...

2012-01-01

305

7 CFR 29.2529 - Leaf scrap.  

Code of Federal Regulations, 2012 CFR

... 2012-01-01 2012-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2012-01-01

306

7 CFR 29.2529 - Leaf scrap.  

... 2014-01-01 2014-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2014-01-01

307

7 CFR 29.6022 - Leaf scrap.  

Code of Federal Regulations, 2011 CFR

... 2011-01-01 2011-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2011-01-01

308

Stem diameter changes before bud opening in Zelkova serrata saplings.  

PubMed

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

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

2003-02-01

309

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

2012-05-15

310

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

311

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; lo 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

312

Exserohilum Leaf Spot on Tigergrass  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tigergrass (Thysanolaena maxima (Roxb.) Kuntze ) is a popular ornamental grass grown throughout landscapes in South Florida. In the summer of 2006, a leaf spot was observed on tigergrass in the landscape and a commercial nursery in Homestead, FL. The causal agent of the leaf spot was isolated, cha...

313

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

314

Stem Cells and Diseases  

MedlinePLUS

... U.S. policy? More FAQs Links to related resources Stem Cell Research Center for Regenerative Medicine NIH Stem Cell Unit ... Help My Medical Condition? The International Society for Stem Cell Research (ISSCR) ISSCR has developed information to help you ...

315

Stem Cell Transplants  

MedlinePLUS

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

316

The basis for variation in leaf longevity of plants  

Microsoft Academic Search

Any theory of leaf phenology must predict leaf longevity, leaf habit, leaf expansion and its timing among other variables. These phenological traits may be important keys to understand the response of trees to climatic change. Here I concentrate on and review two of these critical phenological traits, leaf longevity and leaf habit. Theories of leaf longevity were re-evaluated and leaf

Kihachiro Kikuzawa

1995-01-01

317

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. PMID:21724835

Yoshida, Saiko; Mandel, Therese; Kuhlemeier, Cris

2011-01-01

318

Stem cell activation by light guides plant organogenesis.  

PubMed

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. PMID:21724835

Yoshida, Saiko; Mandel, Therese; Kuhlemeier, Cris

2011-07-01

319

Lineage tracing quantification reveals symmetric stem cell division in Drosophila male germline stem cells  

PubMed Central

Summary In the homeostatic state, adult stem cells divide either symmetrically to increase the stem cell number to compensate stem cell loss, or asymmetrically to maintain the population while producing differentiated cells. We have investigated the mode of stem cell division in the testes of Drosophila melanogaster by lineage tracing and confirm the presence of symmetric stem cell division in this system. We found that the rate of symmetric division is limited to 1-2% of total germline stem cell (GSC) divisions, but it increases with expression of a cell adhesion molecule, E-cadherin, or a regulator of the actin cytoskeleton, Moesin, which may modulate adhesiveness of germ cells to the stem cell niche. Our results indicate that the decision regarding asymmetric vs. symmetric division is a dynamically regulated process that contributes to tissue homeostasis, responding to the needs of the tissue. PMID:24465278

Salzmann, Viktoria; Inaba, Mayu; Cheng, Jun; Yamashita, Yukiko M.

2014-01-01

320

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

PubMed

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

2007-01-01

321

Generation of functional hemangioblasts from human embryonic stem cells  

E-print Network

Generation of functional hemangioblasts from human embryonic stem cells Shi-Jiang Lu1, Qiang Feng1 equivalent of the heman- gioblast was isolated using a mouse embryonic stem cell differ- entiation system12 for generating large numbers of these bipotential progenitors--known as hemangioblasts--from human embryonic stem

Cai, Long

322

Cytoskeleton-based forecasting of stem cell lineage fates  

E-print Network

for stem cell tissue regeneration. During the process of lineage commitment, cells undergo a numberCytoskeleton-based forecasting of stem cell lineage fates Matthew D. Treisera , Eric H. Yanga, and approved November 13, 2009 (received for review August 24, 2009) Stem cells that adopt distinct lineages

Androulakis, Ioannis (Yannis)

323

STEM: Science Technology Engineering Mathematics. State-Level Analysis  

ERIC Educational Resources Information Center

The science, technology, engineering, and mathematics (STEM) state-level analysis provides policymakers, educators, state government officials, and others with details on the projections of STEM jobs through 2018. This report delivers a state-by-state snapshot of the demand for STEM jobs, including: (1) The number of forecast net new and

Carnevale, Anthony P.; Smith, Nicole; Melton, Michelle

2011-01-01

324

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. PMID:5665251

Macnicol, P. K.

1968-01-01

325

Leaf hydraulics II: vascularized tissues.  

PubMed

Current models of leaf hydration employ an Ohm's law analogy of the leaf as an ideal capacitor, neglecting the resistance to flow between cells, or treat the leaf as a plane sheet with a source of water at fixed potential filling the mid-plane, neglecting the discrete placement of veins as well as their resistance. We develop a model of leaf hydration that considers the average conductance of the vascular network to a representative areole (region bounded by the vascular network), and represent the volume of tissue within the areole as a poroelastic composite of cells and air spaces. Solutions to the 3D flow problem are found by numerical simulation, and these results are then compared to 1D models with exact solutions for a range of leaf geometries, based on a survey of temperate woody plants. We then show that the hydration times given by these solutions are well approximated by a sum of the ideal capacitor and plane sheet times, representing the time for transport through the vasculature and tissue respectively. We then develop scaling factors relating this approximate solution to the 3D model, and examine the dependence of these scaling factors on leaf geometry. Finally, we apply a similar strategy to reduce the dimensions of the steady state problem, in the context of peristomatal transpiration, and consider the relation of transpirational gradients to equilibrium leaf water potential measurements. PMID:24012489

Rockwell, Fulton E; Holbrook, N Michele; Stroock, Abraham D

2014-01-01

326

Costs of measuring leaf area index of corn  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

327

STEM Careers Exploration  

NSDL National Science Digital Library

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

328

H-Isotopic Fractionation During Biosynthesis of Leaf Waxes in C3 Plants: Trees vs. Grasses  

NASA Astrophysics Data System (ADS)

Recent studies indicate that hydrogen isotope (D/H) ratios of higher-plant leaf waxes in lake sediments have great potential to be used as a proxy for reconstructing past source water isotope composition and/or relative humidity on continents. However, hydrogen isotopic fractionation during biosynthesis of leaf waxes in various terrestrial plants remains poorly understood. A recent study of 7 terrestrial and aquatic plant types from a single site in Massachusetts shows that D/H ratios among different plant types can vary as much as 70, with the largest difference occurring between tree and grasses (Hou et al., in review). This variability may have been caused by different degrees of evapotranspiration among different plant types (e.g., trees vs. grasses), but could also be attributed to different biosynthetic isotopic fractionation. We designed a series of growth chamber experiments to trace the sources of hydrogen isotopic difference between trees and grasses. Five tree species [white ash (Fraxinus pennsylvanica), red oak (Quercus rubra), red maple (Acer rubrum), spruce (Picea sp.) and white cedar (Thuja occidentalis)] and three grass species [orchard grass (Dactylis glomerata), timothy weed (Phleum pratense), Foxtail (Setaria sp.)] were grown in a growth chamber under controlled conditions. Plants were irrigated with the same source water. We tracked hydrogen isotopic variation of water from source water to stem water to leaf water, and eventually to leaf waxes. Fifty-three leaf and stem samples were harvested. Water from these samples was vacuum-extracted and analyzed for D/H ratios, and compared with D/H ratios of corresponding leaf waxes. Our results allow us to determine whether evapotranspiration rates or intrinsic isotopic fractionation during biosynthesis was the dominant factor controlling the H isotopic ratios of leaf waxes in trees and grasses. Our results are also helpful for interpreting hydrogen isotopic variations of sedimentary leaf waxes.

Toney, J. L.; Hou, J.; Huang, Y.

2006-12-01

329

QTLs for shelf life in lettuce co-locate with those for leaf biophysical properties but not with those for leaf developmental traits.  

PubMed

Developmental and biophysical leaf characteristics that influence post-harvest shelf life in lettuce, an important leafy crop, have been examined. The traits were studied using 60 informative F9 recombinant inbed lines (RILs) derived from a cross between cultivated lettuce (Lactuca sativa cv. Salinas) and wild lettuce (L. serriola acc. UC96US23). Quantitative trait loci (QTLs) for shelf life co-located most closely with those for leaf biophysical properties such as plasticity, elasticity, and breakstrength, suggesting that these are appropriate targets for molecular breeding for improved shelf life. Significant correlations were found between shelf life and leaf size, leaf weight, leaf chlorophyll content, leaf stomatal index, and epidermal cell number per leaf, indicating that these pre-harvest leaf development traits confer post-harvest properties. By studying the population in two contrasting environments in northern and southern Europe, the genotype by environment interaction effects of the QTLs relevant to leaf development and shelf life were assessed. In total, 107 QTLs, distributed on all nine linkage groups, were detected from the 29 traits. Only five QTLs were common in both environments. Several areas where many QTLs co-located (hotspots) on the genome were identified, with relatively little overlap between developmental hotspots and those relating to shelf life. However, QTLs for leaf biophysical properties (breakstrength, plasticity, and elasticity) and cell area correlated well with shelf life, confirming that the ideal ideotype lettuce should have small cells with strong cell walls. The identification of QTLs for leaf development, strength, and longevity will lead to a better understanding of processability at a genetic and cellular level, and allow the improvement of salad leaf quality through marker-assisted breeding. PMID:17347132

Zhang, Fang Z; Wagstaff, Carol; Rae, Anne M; Sihota, Arinder K; Keevil, C William; Rothwell, Steve D; Clarkson, Graham J J; Michelmore, Richard W; Truco, Mara Jos; Dixon, Mark S; Taylor, Gail

2007-01-01

330

Evolution of leaf warbler songs (Aves: Phylloscopidae)  

PubMed Central

Songs in passerine birds are important for territory defense and mating. Speciation rates in oscine passerines are so high, due to cultural evolution, that this bird lineage makes up half of the extant bird species. Leaf warblers are a speciose Old-World passerine family of limited morphological differentiation, so that songs are even more important for species delimitation. We took 16 sonographic traits from song recordings of 80 leaf warbler taxa and correlated them with 15 potentially explanatory variables, pairwise, and in linear models. Based on a well-resolved molecular phylogeny of the same taxa, all pairwise correlations were corrected for relatedness with phylogenetically independent contrasts and phylogenetic generalized linear models were used. We found a phylogenetic signal for most song traits, but a strong one only for the duration of the longest and of the shortest element, which are presumably inherited instead of learned. Body size of a leaf warbler species is a constraint on song frequencies independent of phylogeny. At least in this study, habitat density had only marginal impact on song features, which even disappeared through phylogenetic correction. Maybe most leaf warblers avoid the deterioration through sound propagation in dense vegetation by singing from exposed perches. Latitudinal (and longitudinal) extension of the breeding ranges was correlated with most song features, especially verse duration (longer polewards and westwards) and complexity (lower polewards). Climate niche or expansion history might explain these correlations. The number of different element types per verse decreases with elevation, possibly due to fewer resources and congeneric species at higher elevations. PMID:25691998

Tietze, Dieter Thomas; Martens, Jochen; Fischer, Balduin S; Sun, Yue-Hua; Klussmann-Kolb, Annette; Pckert, Martin

2015-01-01

331

Determining Leaf-Angle Distribution of Vineyards in Delano, CA Using Terrestrial LiDAR  

NASA Astrophysics Data System (ADS)

Plants can regulate the solar exposure they receive by adjusting their leaf-angles, and as a result, leaf-angle can serve as an indicator for plant health and photosynthetic activity. Leaf-angle also serves as an important input parameter for the calculation of reflectance and transmittance in vegetation canopies. This study presents an indirect and nondestructive method to retrieve leaf-angle by calculating surface normal vectors of grapevine leaves using terrestrial LiDAR scanning (TLS). Three scans were performed in June of 2012 at a table grape vineyard located in Delano, CA. Data points collected were classified based on scan number, elevation, red-green-blue (RGB) values, and hue-saturation-value (HSV) values. Individual leaf-angles were found by calculating the surface normal of a subset of leaf points. Subsets were made up of all points within a 5cm spherical radius of the central point of each individual leaf, with the origin calculated as the mean of all points in the subset. This process was repeated for all leaf centroid points in order to define the distribution of leaf-angles. Leaf-angles and their distribution in canopies can now serve as better inputs into corresponding research and models determining plant productivity and health. Utilizing more accurate import parameters allows agriculturalists to better monitor plant stress and practice more sustainable water management policies.

Hopkins, A.; Grigsby, S.; Harburger, A.; Ustin, S.

2012-12-01

332

Field studies of leaf gas exchanges in oil palm tree (Elaeis guineensis Jacq.)  

E-print Network

(PLC, A.D.C.3) and a portable C02 analyzer (LCA2, A.D.C.) connected in an open system. Leaf tempera leaf fully opened is numbered 1). Light was the only limiting factor. Relative error of measurements because of rapid stoma- tal closing (Fig. 3a, b). There was no change in the C02 assimilation rate

Paris-Sud XI, Université de

333

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

334

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 20C. 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

335

7 CFR 29.3036 - Leaf surface.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2013-01-01

336

7 CFR 29.2528 - Leaf.  

Code of Federal Regulations, 2012 CFR

...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2012-01-01

337

7 CFR 29.3525 - Leaf.  

Code of Federal Regulations, 2012 CFR

...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2012-01-01

338

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2013 CFR

...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2013-01-01

339

7 CFR 29.3525 - Leaf.  

...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2014-01-01

340

7 CFR 29.1028 - Leaf.  

Code of Federal Regulations, 2011 CFR

...Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2011-01-01

341

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2010 CFR

...Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2010-01-01

342

7 CFR 29.3036 - Leaf surface.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2010-01-01

343

7 CFR 29.1028 - Leaf.  

Code of Federal Regulations, 2010 CFR

...Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2010-01-01

344

7 CFR 29.3525 - Leaf.  

Code of Federal Regulations, 2013 CFR

...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2013-01-01

345

7 CFR 29.2528 - Leaf.  

Code of Federal Regulations, 2011 CFR

...Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2011-01-01

346

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2012 CFR

...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2012-01-01

347

7 CFR 29.2528 - Leaf.  

Code of Federal Regulations, 2013 CFR

...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2013-01-01

348

7 CFR 29.3036 - Leaf surface.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2012-01-01

349

7 CFR 29.1028 - Leaf.  

Code of Federal Regulations, 2012 CFR

...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2012-01-01

350

7 CFR 29.3036 - Leaf surface.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2011-01-01

351

7 CFR 29.1028 - Leaf.  

...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2014-01-01

352

7 CFR 29.1028 - Leaf.  

Code of Federal Regulations, 2013 CFR

...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2013-01-01

353

7 CFR 29.3525 - Leaf.  

Code of Federal Regulations, 2011 CFR

...Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2011-01-01

354

7 CFR 29.2528 - Leaf.  

...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2014-01-01

355

7 CFR 29.3036 - Leaf surface.  

...2014-01-01 2014-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2014-01-01

356

7 CFR 29.3033 - Leaf.  

...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2014-01-01

357

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2011 CFR

...Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

2011-01-01

358

Very Sparse Leaf Languages Lance Fortnow  

E-print Network

Very Sparse Leaf Languages Lance Fortnow Department of Computer Science University of Chicago studied the balanced leaf languages defined via poly-logarithmically sparse leaf pattern sets. Unger shows that NP-complete sets are not polynomial-time many-one reducible to such balanced leaf language unless

Fortnow, Lance

359

Very Sparse Leaf Languages # Lance Fortnow +  

E-print Network

Very Sparse Leaf Languages # Lance Fortnow + Department of Computer Science University of Chicago studied the balanced leaf languages defined via poly­logarithmically sparse leaf pattern sets. Unger shows that NP­complete sets are not polynomial­time many­one reducible to such balanced leaf language unless

Fortnow, Lance

360

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

PubMed

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

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

2014-01-01

361

Switchgrass (Panicum virgatum L) flag leaf transcriptomes reveal molecular signatures of leaf development, senescence, and mineral dynamics.  

PubMed

Switchgrass flag leaves can be expected to be a source of carbon to the plant, and its senescence is likely to impact the remobilization of nutrients from the shoots to the rhizomes. However, many genes have not been assigned a function in specific stages of leaf development. Here, we characterized gene expression in flag leaves over their development. By merging changes in leaf chlorophyll and the expression of genes for chlorophyll biosynthesis and degradation, a four-phase molecular roadmap for switchgrass flag leaf ontogeny was developed. Genes associated with early leaf development were up-regulated in phase 1. Phase 2 leaves had increased expression of genes for chlorophyll biosynthesis and those needed for full leaf function. Phase 3 coincided with the most active phase for leaf C and N assimilation. Phase 4 was associated with the onset of senescence, as observed by declining leaf chlorophyll content, a significant up-regulation in transcripts coding for enzymes involved with chlorophyll degradation, and in a large number of senescence-associated genes. Of considerable interest were switchgrass NAC transcription factors with significantly higher expression in senescing flag leaves. Two of these transcription factors were closely related to a wheat NAC gene that impacts mineral remobilization. The third switchgrass NAC factor was orthologous to an Arabidopsis gene with a known role in leaf senescence. Other genes coding for nitrogen and mineral utilization, including ureide, ammonium, nitrate, and molybdenum transporters, shared expression profiles that were significantly co-regulated with the expression profiles of the three NAC transcription factors. These data provide a good starting point to link shoot senescence to the onset of dormancy in field-grown switchgrass. PMID:25173486

Palmer, Nathan A; Donze-Reiner, Teresa; Horvath, David; Heng-Moss, Tiffany; Waters, Brian; Tobias, Christian; Sarath, Gautam

2015-01-01

362

BOREAS TE-12 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

The BOREAS TE-12 team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, and gas exchange of boreal vegetation. This data set contains measurements of leaf gas exchange conducted in the SSA during the growing seasons of 1994 and 1995 using a portable gas exchange system. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Arkebauer, Timothy J.; Yang, Litao

2000-01-01

363

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

PubMed Central

Background and Aims Despite long-held interest, knowledge on why leaf size varies widely among species is still incomplete. This study was conducted to assess whether abiotic factors, phylogenetic histories and multi-trait interactions act together to shape leaf size. Methods Fifty-seven pairs of altitudinal vicariant species were selected in northern Spain, and leaf area and a number of functionally related leaf, shoot and whole plant traits were measured for each pair. Structural equation modelling helped unravel trait interactions affecting leaf size, and Mantel tests weighed the relative relevance of phylogeny, environment and trait interactions to explain leaf size reduction with altitude. Key Results Leaves of highland vicariants were generally smaller than those of lowlands. However, the extent of leaf size reduction with increasing altitude was widely variable among genera: from approx. 700 cm2 reduction (96 % in Polystichum) to approx. 30 cm2 increase (37 % in Sorbus). This was partially explained by shifts in leaf, shoot and whole plant traits (3564 % of explained variance, depending on models), with size/number trade-offs more influential than shifts in leaf form and leaf economics. Shifts in traits were more important than phylogenetic distances or site-specific environmental variation in explaining the degree of leaf size reduction with altitude. Conclusions Ecological filters, constraints due to phylogenetic history (albeit modest in the study system), and phenotypic integration contribute jointly to shape single-trait evolution. Here, it was found that phenotypic change was far more important than shared ancestry to explaine leaf size differences of closely related species segregated along altitudes. PMID:21199835

Milla, Rubn; Reich, Peter B.

2011-01-01

364

Near infrared leaf reflectance modeling  

NASA Technical Reports Server (NTRS)

Near infrared leaf reflectance modeling using Fresnel's equation (Kumar and Silva, 1973) and Snell's Law successfully approximated the spectral curve for a 0.25-mm turgid oak leaf lying on a Halon background. Calculations were made for ten interfaces, air-wax, wax-cellulose, cellulose-water, cellulose-air, air-water, and their inverses. A water path of 0.5 mm yielded acceptable results, and it was found that assignment of more weight to those interfaces involving air versus water or cellulose, and less to those involving wax, decreased the standard deviation of the error for all wavelengths. Data suggest that the air-cell interface is not the only important contributor to the overall reflectance of a leaf. Results also argue against the assertion that the near infrared plateau is a function of cell structure within the leaf.

Parrish, J. B.

1985-01-01

365

Hormonal Regulation of Leaf Abscission  

PubMed Central

A review is given of the progress made during the last 6 years in elucidating the nature, locus of action, and transport properties of the endogenous hormones that control leaf abscission. PMID:16657014

Jacobs, William P.

1968-01-01

366

Rotatable stem and lock  

DOEpatents

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

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

1981-10-27

367

Rotatable stem and lock  

DOEpatents

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

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

1984-01-01

368

Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L. 1  

PubMed Central

In this paper we describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L. I. Gordon ([1965] in E Tongiorgi, ed, Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, Italy, pp 9-130) for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AWV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively depleted in heavy isotopes when exposed to AWV with a low heavy isotope composition, and leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate. PMID:16668226

Flanagan, Lawrence B.; Comstock, Jonathan P.; Ehleringer, James R.

1991-01-01

369

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

Microsoft Academic Search

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

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

1998-01-01

370

[Bioethical challenges of stem cell tourism].  

PubMed

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

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

2013-08-01

371

Characterization of leaf senescence and pod development in soybean explants.  

PubMed

Excised soybean (Glycine max [L.] Merrill) cv Anoka leaf discs tend to remain green even after the corresponding intact leaves have turned yello on fruiting plants. We have found that explants which include a leaf along with a stem segment (below the node) and one or more pods (maintained on distilled H(2)O) show similar but accelerated leaf yellowing and abscission compared with intact plants. In podded explants excised at pre-podfill, the leaves begin to yellow after 16 days, whereas those excised at late podfill begin to yellow after only 6 days. Although stomatal resistances remain low during the first light period after excision, they subsequently increase to levels above those in leaves of intact plants. Explants taken at mid to late podfill with one or more pods per node behave like intact plants in that pod load does not affect the time lag to leaf yellowing. Explant leaf yellowing and abscission are delayed by removal of the pods or seeds or by incubation in complete mineral nutrient solution or in 4.6 micromolar zeatin. Like chorophyll breakdown, protein loss is accelerated in the explants, but minerals or especially zeatin can retard the loss. Pods on explants show rates and patterns of color change (green to yellow to brown) similar to those of pods on intact plants. These changes start earlier in explants on water than in intact plants, but they can be delayed by adding zeatin. Seed dry weight increased in explants, almost as much as in intact plants. Explants appear to be good analogs of the corresponding parts of the intact plant, and they should prove useful for analyzing pod development and mechanisms of foliar senescence. Moreover, our data suggest that the flux of minerals and cytokinin from the roots could influence foliar senescence in soybeans, but increased stomatal resistance does not seem to cause foliar senescence. PMID:16662956

Neumann, P M; Tucker, A T; Noodn, L D

1983-05-01

372

Stem cell therapy without the cells.  

PubMed

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

Maguire, Greg

2013-11-01

373

Stem cell therapy without the cells  

PubMed Central

As an example of the burgeoning importance of stem cell therapy, this past month the California Institute for Regenerative Medicine (CIRM) has approved $70 million to create a new network of stem cell clinical trial centers. Much work in the last decade has been devoted to developing the use of autologous and allogeneic adult stem cell transplants to treat a number of conditions, including heart attack, dementia, wounds, and immune system-related diseases. The standard model teaches us that adult stem cells exists throughout most of the body and provide a means to regenerate and repair most tissues through replication and differentiation. Although we have often witnessed the medical cart placed in front of the scientific horse in the development of stem cell therapies outside of academic circles, great strides have been made, such as the use of purified stem cells1 instead of whole bone marrow transplants in cancer patients, where physicians avoid re-injecting the patients with their own cancer cells.2 We most often think of stem cell therapy acting to regenerate tissue through replication and then differentiation, but recent studies point to the dramatic effects adult stem cells exert in the repair of various tissues through the release of paracrine and autocrine substances, and not simply through differentiation. Indeed, up to 80% of the therapeutic effect of adult stem cells has been shown to be through paracrine mediated actions.3 That is, the collected types of molecules released by the stem cells, called the secretome, or stem cell released molecules (SRM), number in the 100s, including proteins, microRNA, growth factors, antioxidants, proteasomes, and exosomes, and target a multitude of biological pathways through paracrine actions. The composition of the different molecule types in SRM is state dependent, and varies with cell type and conditions such as age and environment. PMID:24567776

Maguire, Greg

2013-01-01

374

Response of azalea cuttings to leaf damage and leaf removal  

Technology Transfer Automated Retrieval System (TEKTRAN)

Binucleate Rhizoctonia species, the pathogens that cause azalea web blight, can be carried on stem cuttings, perpetuating the disease through subsequent crops. Previous studies have demonstrated that submerging Rhizoctonia-infested stem pieces of 'Gumpo White' azalea in 122F (50C) water for 20 min...

375

Plant stem cells as innovation in cosmetics.  

PubMed

The stem cells thanks to their ability of unlimited division number or transformation into different cell types creating organs, are responsible for regeneration processes. Depending on the organism in which the stem cells exists, they divide to the plant or animal ones. The later group includes the stem cells existing in both embryo's and adult human's organs. It includes, among others, epidermal stem cells, located in the hair follicle relieves and also in its basal layers, and responsible for permanent regeneration of the epidermis. Temporary science looks for method suitable for stimulation of the epidermis stem cells, amongst the other by delivery of e.g., growth factors for proliferation that decrease with the age. One of the methods is the use of the plant cell culture technology, including a number of methods that should ensure growth of plant cells, issues or organs in the environment with the microorganism-free medium. It uses abilities of the different plant cells to dedifferentiation into stem cells and coming back to the pluripotent status. The extracts obtained this way from the plant stem cells are currently used for production of both common or professional care cosmetics. This work describes exactly impact of the plant stem cell extract, coming from one type of the common apple tree (Uttwiler Sptlauber) to human skin as one of the first plant sorts, which are used in cosmetology and esthetic dermatology. PMID:25362798

Moru?, Martyna; Baran, Monika; Rost-Roszkowska, Magdalena; Skotnicka-Graca, Urszula

2014-01-01

376

Adventitious in vitro plantlet formation from immature floral stems of Crinum macowanii  

Microsoft Academic Search

Adventitious shoots and plantlets were regenerated in vitro from floral stem explants of Crinum macowanii (Bak.) (bush lily). The length (age) of the floral stem as well as the orientation and position of the explant disc in the floral stem were the most important factors affecting shoot regeneration. The highest number of shoots were regenerated when immature floral stems of

M. M. Slabbert; M. H. Bruyn; D. I. Ferreira; J. Pretorius

1995-01-01

377

Verbal stem space and verb to noun conversion in French1  

E-print Network

Verbal stem space and verb to noun conversion in French1 Delphine Tribout Abstract In this paper I present the verbal stem space in French and its use in lexeme formation. First, I present the stem spaces stem space needs to be extended with an extra slot in order to account for a number of lexeme

Paris-Sud XI, Université de

378

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

379

Direct regeneration of Drosera from leaf explants and shoot tips  

Microsoft Academic Search

An efficient protocol for the micropropagation of Drosera anglica, D. binata and D. cuneifolia is described. Proliferation was obtained from leaf segments and shoot tips, which served as initial explants. The regeneration capacity of explants was influenced by factors such as nutrient media, concentrations of growth regulators and the type of medium (liquid or solid). The highest number of plants

Anna Kawiak; Aleksandra Krlicka; Ewa Lojkowska

2003-01-01

380

Seasonal polyphenism and leaf mimicry in the comma butterfly  

E-print Network

Seasonal polyphenism and leaf mimicry in the comma butterfly CHRISTER WIKLUND & BIRGITTA S 2003; final acceptance 21 December 2003; MS. number: 7774) The comma butterfly, Polygonia c as a result of high predation pressure. Although butterflies in temperate areas that start reproduction soon

Tullberg, Birgitta

381

First Record of Alternaria simsimi Causing Leaf Spot on Sesame (Sesamum indicum L.) in Korea  

PubMed Central

Leaf spot disease was observed in sesame (Sesamum indicum L.) during 2009 and 2010 in Korea. The pathogen was identified as Alternaria simsimi based on morphological and cultural characteristics. The morphological identification was well supported by phylogenetic analysis of the ribosomal DNA-internal transcribed spacer region. A. simsimi isolates caused spot symptoms on leaves and stems of sesame plants 2 wk after artificial inoculation, which were similar to those observed in the field. This is the first record of leaf spot disease in Korea caused by A. simsimi. PMID:25606015

Choi, Young Phil; Paul, Narayan Chandra

2014-01-01

382

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

Microsoft Academic Search

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

Nathalie DruartA; Marisa Rodr iguez-BueyA; Andreas Sj

383

Significance of leaf orientation for leaf temperature in an Amazonian sclerophyll vegetation.  

PubMed

The influence of leaf orientation on leaf temperature has been studied in an sclerophyll vegetation of the Amazon basin, which grows on white sandy soils of very low water retention capacity and variable depth of the water table. Leaf size of the species studied is mainly mesophyllous (sensu Raunkiaer). The high degree of leaf inclination in all species is very characteristic; 55% of the leaves present inclination angles (relative to the vertical) smaller than 45 degrees. Water potential is generally high, not being lower than -14 bars. Leaf resistance increases toward noon during the course of sunny days, indicating either water stress at leaf level or the influence of low relative humidity on stomata opening. Leaf temperature under sunny conditions reflects the influence of leaf orientation on the amount of radiation absorbed by the leaf. Temperature differences recorded range from 1.8--5.4 degrees C. The difference depends on leaf angle, leaf color and leaf diffusion resistance during the period of measurement. Analysis of the relationship between leaf angle and leaf temperature, using Gates leaf energy balance, shows that under the conditions prevailing at noon in sunny days, leaf angles smaller than 50 degrees are effective in reducing leaf temperature within a wide range of leaf resistances to water vapor transfer. PMID:724979

Medina, E; Sobrado, M; Herrera, R

1978-08-10

384

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

385

Mesenchymal stem cells secreting angiopoietin-like-5 support efficient expansion of human hematopoietic stem cells without compromising their repopulating potential  

E-print Network

Clinical and preclinical applications of human hematopoietic stem cells (HSCs) are often limited by scarcity of cells. Expanding human HSCs to increase their numbers while maintaining their stem cell properties has therefore ...

Drake, Adam

386

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

NASA Technical Reports Server (NTRS)

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.

Latimer, J. G.; Mitchell, C. A.

1988-01-01

387

Volatile organic compounds emitted after leaf wounding: On-line analysis by proton-transfer-reaction mass spectrometry  

Microsoft Academic Search

Volatile organic compounds (VOCs) released from vegetation, including wound-induced VOCs, can have important effects on atmospheric chemistry. The analytical methods for measuring wound-induced VOCs, especially the hexenal family of VOCs (hexenals, hexenols, and hexenyl esters), are complicated by their chemical instability and the transient nature of their formation after leaf and stem wounding. Here we demonstrate that formation and emission

Ray Fall; Thomas Karl; Armin Hansel; Alfons Jordan; Werner Lindinger

1999-01-01

388

Allogeneic stem cell transplantation.  

PubMed

Allogeneic stem cell transplantation (HSCT) requires the harvest of an adequate number of stem cells (SC) from a histocompatible donor and their infusion into a patient following a conditioning regimen. During the past 35 years, the role of HSCT has changed from an experimental procedure for terminally ill patients to a curative treatment. In 2003, 1170 procedures were registered in Italy (Italian Group for Blood and Marrow Transplantation). The main reported indications were as follows: leukemia, lymphoproliferative diseases, myelodysplasia, and nonmalignant diseases such as thalassemia and severe aplastic anemia. Important changes have been observed in the last 5 years: the shift from bone marrow to peripheral blood as the SC source, the increasing number of alternative donors such as unrelated, partially matched family donors and cord blood SC, and the new extra-hematological indications including solid tumors. Moreover, the development of nonmyeloablative conditioning regimens have allowed physicians to perform HSCT in patients with advanced age or important comorbidities. In contrast, the availability of the Tyrosine kinase inhibitor (STI-571) for treatment of patients affected by chronic myelogenous leukemia, which was formerly the main indication for HSCT, has produced a dramatic decrease in the number of transplantations in this setting. HSCT performed in the early phases of disease and in young patients offers more than a 50% cure rate. The transplant-related mortality still represents the greatest obstacle, ranging from 20%-30%, despite the less toxic conditioning regimens, high-resolution HLA typing, and better supportive care. GvHD and infections remain the main causes of morbidity. As regards relapses, they correlate with disease status at the time of transplantation. Promising results have been recently obtained with haploidentical and with cord blood SC transplantation also in adult patients. PMID:16182779

Bosi, A; Bartolozzi, B; Guidi, S

2005-01-01

389

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. PMID:19287541

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

2008-01-01

390

Ocular microtremor in brain stem death  

PubMed

OBJECTIVE: This study was undertaken to establish whether measurement of ocular microtremor (OMT) activity could be used as a method to establish brain stem death. Presently, the diagnosis of brain stem death can be made using clinical criteria alone. OMT is a high-frequency, low-amplitude physiological tremor of the eye caused by impulses emanating from the brain stem. There have been a number of reports indicating that the recording of OMT may be useful in the assessment of comatose states and in establishing brain stem viability or death. METHODS: We obtained the OMT recordings of 32 patients suspected of having brain stem death using the piezoelectric strain gauge technique. This method involves mounting the piezoelectric probe in a headset and lowering the rubber-tipped end piece onto the anesthetized scleral surface of the subject. The signal produced is recorded on audiomagnetic tape and later played back and analyzed on an electrocardiographic tape analyzer. RESULTS: In 28 patients, initial clinical assessment confirmed the diagnosis of brain stem death and no OMT activity was recorded from these subjects. In three patients in whom initial clinical assessment demonstrated brain stem function, OMT activity was present; when brain stem death was subsequently diagnosed in these three patients, no OMT activity could be demonstrated. In the remaining patient, two of three OMT recordings demonstrated activity in spite of the absence of clinical evidence of brain stem function. A post mortem revealed bacterial cerebritis in this subject. CONCLUSION: The results suggest that OMT is a sensitive method of detecting brain stem life and that it could play an important role in the assessment of brain stem death. PMID:10371619

Bolger; Bojanic; Phillips; Sheahan; Coakley; Malone

1999-06-01

391

Better Algorithms and Bounds for Directed Maximum Leaf Problems  

Microsoft Academic Search

The Directed Maximum Leaf Out-Branching problem is to flnd an out-branching (i.e. a rooted oriented spanning tree) in a given digraph with the maximum number of leaves. In this paper, we improve known parameterized algorithms and combinatorial bounds on the number of leaves in out-branchings. We show that { every strongly connected digraph D of order n with minimum in-

Noga Alon; Fedor V. Fomin; Gregory Gutin; Michael Krivelevich; Saket Saurabh

2007-01-01

392

STEM Learning Quality Indicator Map  

E-print Network

STEM Learning Quality Indicator Map Quality Indicator Initiation Involvement Implementation Innovation Student Engagement STEM learning experiences are engaging and inspire creativity and imagination STEM learning experience is activity driven with specific step by step directions STEM learning

US Army Corps of Engineers

393

OPT STEM EXTENSION APPLICATION What is the OPT STEM Extension?  

E-print Network

OPT STEM EXTENSION APPLICATION What is the OPT STEM Extension? The OPT STEM Extension is a 17-month based on a bachelor's, master's, or Ph.D in certain STEM (Science, Technology, Engineering, Math) fields. Who is Eligible for the OPT STEM Extension? F-1 students who: 1). hold a STEM degree (see pg. 2

394

Stem cell therapy in neurodegenerative diseases  

PubMed Central

The lack of curative therapies for neurodegenerative diseases has high economic impact and places huge burden on the society. The contribution of stem cells to cure neurodegenerative diseases has been unraveled and explored extensively over the past few years. Beyond substitution of the lost neurons, stem cells act as immunomodulators and neuroprotectors. A large number of preclinical and a small number of clinical studies have shown beneficial outcomes in this context. In this review, we have summarized the current concepts of stem cell therapy in neurodegenerative diseases and the recent advances in this field, particularly between 2010 and 2012. Further studies should be encouraged to resolve the clinical issues and vague translational findings for maximum optimization of the efficacy of stem cell therapy in neurodegenerative diseases.

Sakthiswary, Rajalingham; Raymond, Azman Ali

2012-01-01

395

Leaf Senescence and GABA Shunt  

PubMed Central

Leaf senescence is highly regulated and complex developmental process that involves degradation of macromolecules as well as its recycling. Senescence process involves loss of chlorophyll, degradation of proteins, nucleic acid, lipid and mobilization of nutrients through its transport to the growing parts, developing fruits and seeds. Nitrogen is the most important nutrient to be recycled in senescence process. GABA-transaminase (?-aminobutyric acid) is found to play very important role in nitrogen recycling process through GABA-shunt. Therefore, it is of interest to review the significance of GABA shunt in leaf senescence.

Ansari, Mohammad Israil; Hasan, Saba; Jalil, Syed Uzma

2014-01-01

396

Life in the Leaf Litter  

NSDL National Science Digital Library

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

397

Isolation and Enrichment of Stem Cells  

NASA Astrophysics Data System (ADS)

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

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

398

Quantitative STEM: Experimental Methods and Applications  

NASA Astrophysics Data System (ADS)

High-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM) is highly sensitive to both the atomic number and the Debye-Waller factor of the atom columns. We will discuss the experimental requirements for a quantitative understanding of STEM image contrast, in particular the determination of the precise specimen thickness. We show that near perfect agreement can be achieved between theory and experiment and demonstrate that quantitative STEM allows for column-by-column counting of all the atoms in an arbitrarily shaped specimen.

LeBeau, J. M.; Findlay, S. D.; Allen, L. J.; Stemmer, S.

2012-07-01

399

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

400

UW Summer STEM Undergraduate  

E-print Network

UW Summer STEM Undergraduate Research Poster SessionWednesday, August 21st, 2013 9:00 am--12 noon to conduct research in STEM fields. For more information, contact the Undergraduate Research Program at: urp

Kaminsky, Werner

401

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

PubMed

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

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

2010-06-01

402

Semi-rolled leaf1 encodes a putative glycosylphosphatidylinositol-anchored protein and modulates rice leaf rolling by regulating the formation of bulliform cells.  

PubMed

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. PMID:22715111

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

2012-08-01

403

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. PMID:22715111

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

2012-01-01

404

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2013-01-01

405

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2012-01-01

406

7 CFR 28.471 - Below Leaf Grade Cotton.  

...2014-01-01 2014-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2014-01-01

407

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2010-01-01

408

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2011-01-01

409

Spectral reflectance relationships to leaf water stress  

NASA Technical Reports Server (NTRS)

Spectral reflectance data were collected from detached snapbean leaves in the laboratory with a multiband radiometer. Four experiments were designed to study the spectral response resulting from changes in leaf cover, relative water content of leaves, and leaf water potential. Spectral regions included in the analysis were red (630-690 nm), NIR (760-900 nm), and mid-IR (2.08-2.35 microns). The red and mid-IR bands showed sensitivity to changes in both leaf cover and relative water content of leaves. The NIR was only highly sensitive to changes in leaf cover. Results provided evidence that mid-IR reflectance was governed primarily by leaf moisture content, although soil reflectance was an important factor when leaf cover was less than 100 percent. High correlations between leaf water potentials and reflectance were attributed to covariances with relative water content of leaves and leaf cover.

Ripple, William J.

1986-01-01

410

An Innovative Way to Monitor Leaf Age  

NASA Astrophysics Data System (ADS)

Anthony John Garnello, Karina Paredes, Uyen Khanh Ho Trinh, Jin Wu, Scott Saleska Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA Abstract: Leaf age is an important characteristic for controlling plant functional performance and is associated with the changes of leaf physical, chemical, and physiological properties. Understanding how plant physiology changes over time will allow more accurate predictions of growth patterns, and a more comprehensive understanding of vegetative life histories. There still lacks an efficient technique in monitoring leaf age, tagging leaves is still the only way to accurately monitor leaf age. The goal of this study is to develop a multi-metric, accurate technique for better monitoring of leaf age. In order to acquire true leaf age records, 10 individual plant species were selected at the University of Arizona campus, and newly flushing leaves were tagged and monitored during the Monsoon season (from early June, 2013, to mid October, 2013). Every 2 weeks, 10 to 15 leaves in relative age order were harvested from each 1-meter branch to measure multiple key leaf metrics, including leaf thickness (via micrometer), fresh and dry weight, fresh and dry area (via ImageJ software), and leaf hyperspectral reflectance (via a handheld ASD Field Pro). Other leaf traits were also derived from our measurements, such as specific leaf area (SLA), leaf density (fresh weight/leaf volume), water percentage, and shrinkage ratio (1-dry area/fresh area). The hyperspectral version of vegetation index (a ratio derived from two spectral channels) was generated for each branch sample, by randomly selecting two channels from within the spectral domain of 350 nm to 2500 nm. The preliminary result documents three types of hyperspectral vegetation index (VI) which are highly related with leaf relative age order (R2>0.9). These include the sensitive spectral domains correlated with (a) leaf pigments (~550nm) and leaf physical structure (750nm-1000nm), (b) leaf pigments (~550nm) and leaf water concentration (1400nm-2300nm), and (c) leaf physical structure (750nm-1000nm) and leaf water concentration (1400nm-2300nm). Preliminary results showed that (1) among the key leaf traits, leaf shrinkage is the only trait that showed a consistent correlation with relative age order across the samples; (2) a power function best modeled the interspecies relationship between leaf shrinkage and leaf age (R2 = 0.81, p-value < 0.01, 22 data points for 7 species); (3) a strong correlation was found between the predicted leaf age using the species specific power functions of leaf shrinkage and true leaf age (R2= 0.96, p-value < 0.01), suggesting that leaf shrinkage could be a useful trait for prediction of absolute leaf age in the future. In the next step, we will integrate leaf shrinkage based leaf age prediction with hyperspectral VI framework, aiming to derive some reliable VIs which can be universal for leaf aging prediction among all the species.

Garnello, A.; Paredes, K.; Trinh, U.; Saleska, S. R.; Wu, J.

2013-12-01

411

7 CFR 30.2 - Leaf tobacco.  

...2014-01-01 2014-01-01 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...

2014-01-01

412

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 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...

2012-01-01

413

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 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...

2011-01-01

414

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 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...

2010-01-01

415

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

416

Neurological Complications of Hematopoietic Stem Cell Transplantation  

Microsoft Academic Search

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

Eudocia Quant; Patrick Y. Wen

417

Hematopoietic Stem Cell Transplantation  

Microsoft Academic Search

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

Robbie Norville; Deborah Tomlinson

418

Educating The Local STEM Community On The Way To Institutional Transformation  

E-print Network

--major goals: ¡ 1) to increase the number and success of STEM women faculty of color ¡ 2) to increase the success and leadership of women faculty in STEM ¡ 3) to educate all the faculty and in particular) to increase the number and success of STEM women faculty of color ¡ 2) to increase the success and leadership

Tilbury, Dawn

419

HLA Association with Hematopoietic Stem Cell Transplantation Outcome: The Number of Mismatches at HLA-A, B, -C, -DRB1, or -DQB1 Is Strongly Associated with Overall Survival  

Microsoft Academic Search

HLA matching between the donor and recipient improves the success of unrelated hematopoietic stem cell transplantation (HSCT). Because many patients in need of an unrelated transplant have only donors with mismatch, information is needed to evaluate the limits of HLA mismatching. We examined the association of survival, acute graft-versus-host disease (aGVHD) and relapse with HLA-A, -B, -C, -DRB, -DQB1, and

Pascale Loiseau; Marc Busson; Marie-Lorraine Balere; Anne Dormoy; Jean-Denis Bignon; Katia Gagne; Lucette Gebuhrer; Valrie Dubois; Isabelle Jollet; Monique Bois; Pascale Perrier; Dominique Masson; Agns Moine; Lna Absi; Denis Reviron; Virginia Lepage; Ryad Tamouza; Antoine Toubert; Evelyne Marry; Zina Chir; Jean-Pierre Jouet; Didier Blaise; Dominique Charron; Colette Raffoux

2007-01-01

420

Remote estimation of leaf area index and green leaf biomass in maize canopies  

E-print Network

Remote estimation of leaf area index and green leaf biomass in maize canopies Anatoly A. Gitelson,1 750 nm). The technique was tested in agricultural fields under a maize canopy, and proved suitable of leaf area index and green leaf biomass in maize canopies, Geophys. Res. Lett., 30(5), 1248, doi:10

Gitelson, Anatoly

421

Stem Cell Basics  

MedlinePLUS

... U.S. policy? More FAQs Links to related resources Stem Cell Research Center for Regenerative Medicine NIH Stem Cell Unit ... of scientific research, and the potential use of stem cells in research and in treating disease. The primer includes information ...

422

Understanding Embryonic Stem Cells  

NSDL National Science Digital Library

This indexed webcast video along with synchronized lecture slides is from Howard Hughes Medical Institute's 2006 Holiday LecturesPotent Biology: Stem Cells, Cloning, and Regeneration. Douglas A. Melton presents an introduction to stem cells, as well as answers to questions about the role of stem cells in the human body. This video requires RealPlayer 10.

Douglas A. Melton, Ph.D. (Howard Hughes Medical Institute; )

2008-04-10

423

STEM Bridge Scholarship Program  

E-print Network

2015-2016 STEM Bridge Scholarship Program Virginia Space Grant Consortium (VSGC) provides renewable STEM Bridge Scholarships of $1,000 to sophomore students from any federally recognized minority group enrolled full-time in a program of study in science, technology, engineering, or math (STEM) at one

Buehrer, R. Michael

424

Growth and leaf physiology of monkeyflowers with different altitude ranges.  

PubMed

Every species is limited both geographically and ecologically to a subset of available habitats, yet for many species the causes of distribution limits are unknown. Temperature is thought to be one of the primary determinants of species distributions along latitudinal and altitudinal gradients. This study examined leaf physiology and plant performance under contrasting temperature regimes of sister species of monkeyflower, Mimulus cardinalis and Mimulus lewisii (Phrymaceae), that differ in altitude distribution to test the hypothesis that temperature is the primary determinant of differences in fitness versus altitude. Each species attained greatest aboveground biomass, net photosynthetic rate, and effective quantum yield of photosystem II when grown under temperatures characteristic of the altitudinal range center. Although both species exhibited greater stem length, stomatal conductance, and intercellular CO2 concentration in hot than in cold temperatures, these traits showed much greater reductions under cold temperature for M. cardinalis than for M. lewisii. Survival of M. lewisii was also sensitive to temperature, showing a striking decrease in hot temperatures. Within each temperature regime, the species native to that temperature displayed greatest growth and leaf physiological capacity. Populations from the altitude range center and range margin of each species were used to examine population differentiation, but central and marginal populations did not differ in most growth or leaf physiological responses to temperature. This study provides evidence that M. cardinalis and M. lewisii differ in survival, growth, and leaf physiology under temperature regimes characterizing their contrasting low and high altitude range centers, and suggests that the species' altitude range limits may arise, in part, due to metabolic limitations on growth that ultimately decrease survival and limit reproduction. PMID:16468056

Angert, Amy Lauren

2006-06-01

425

AGO1 defines a novel locus of Arabidopsis controlling leaf development  

Microsoft Academic Search

An allelic series of the novel argonaute mutant (ago1-1 to ago1-6) of the herbaceous plant Arabidopsis thaliana has been isolated. The ago1 mutation pleotropically affects general plant architecture. The apical shoot meristem generates rosette leaves and a single stem, but axillary meristems rarely develop. Rosette leaves lack a leaf blade but still show adaxial\\/abaxial differen- tiation. Instead of cauline leaves,

Karen Bohmert; Isabelle Camus; Catherine Bellini; David Bouchez

1998-01-01

426

7 CFR 29.3528 - Leaf surface.  

...TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign...3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2014-01-01

427

7 CFR 29.3528 - Leaf surface.  

Code of Federal Regulations, 2012 CFR

...TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign...3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2012-01-01

428

7 CFR 29.3528 - Leaf surface.  

Code of Federal Regulations, 2010 CFR

...TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign...3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2010-01-01

429

7 CFR 29.3528 - Leaf surface.  

Code of Federal Regulations, 2013 CFR

...TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign...3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2013-01-01

430

7 CFR 29.3528 - Leaf surface.  

Code of Federal Regulations, 2011 CFR

...TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign...3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

2011-01-01

431

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

432

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2011 CFR

...2 2011-01-01 2011-01-01 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...

2011-01-01

433

7 CFR 29.2277 - Leaf scrap.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2013-01-01

434

7 CFR 29.3034 - Leaf scrap.  

... 2014-01-01 2014-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2014-01-01

435

7 CFR 29.3034 - Leaf scrap.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2013-01-01

436

7 CFR 29.3034 - Leaf scrap.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2010-01-01

437

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2013 CFR

...2 2013-01-01 2013-01-01 false Leaf structure. 29.2278 Section 29.2278...Fire-Cured Tobacco (u.s. Type 21) 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See...

2013-01-01

438

7 CFR 29.3526 - Leaf scrap.  

Code of Federal Regulations, 2012 CFR

... 2012-01-01 2012-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2012-01-01

439

7 CFR 29.2277 - Leaf scrap.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2010-01-01

440

7 CFR 29.2278 - Leaf structure.  

...2 2014-01-01 2014-01-01 false Leaf structure. 29.2278 Section 29.2278...Fire-Cured Tobacco (u.s. Type 21) 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See...

2014-01-01

441

7 CFR 29.2277 - Leaf scrap.  

... 2014-01-01 2014-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2014-01-01

442

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2012 CFR

...2 2012-01-01 2012-01-01 false Leaf structure. 29.2278 Section 29.2278...Fire-Cured Tobacco (u.s. Type 21) 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See...

2012-01-01

443

On magnetic leaf-wise intersections  

E-print Network

In this article we introduce the notion of a magnetic leaf-wise intersection point which is a generalization of the leaf-wise intersection point with magnetic effects. We also prove the existence of magnetic leaf-wise intersection points under certain topological assumptions.

Bae, Youngjin

2011-01-01

444

7 CFR 29.2277 - Leaf scrap.  

Code of Federal Regulations, 2012 CFR

... 2012-01-01 2012-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2012-01-01

445

7 CFR 29.2277 - Leaf scrap.  

Code of Federal Regulations, 2011 CFR

... 2011-01-01 2011-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2011-01-01

446

7 CFR 29.3526 - Leaf scrap.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2013-01-01

447

7 CFR 29.3034 - Leaf scrap.  

Code of Federal Regulations, 2011 CFR

... 2011-01-01 2011-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2011-01-01

448

7 CFR 29.3526 - Leaf scrap.  

... 2014-01-01 2014-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2014-01-01

449

7 CFR 29.3526 - Leaf scrap.  

Code of Federal Regulations, 2011 CFR

... 2011-01-01 2011-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

2011-01-01

450

7 CFR 29.3034 - Leaf scrap.  

Code of Federal Regulations, 2012 CFR

... 2012-01-01 2012-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

2012-01-01

451

ORIGINAL PAPER Leaf wax d2  

E-print Network

ORIGINAL PAPER Leaf wax d2 H and varve-thickness climate proxies from proglacial lake sediments Science+Business Media B.V. 2012 Abstract We present a multiproxy paleoclimate record using leaf wax Á Leaf wax Á Proglacial lake Á Varve Introduction Arctic proglacial lake sediments are excellent

Briner, Jason P.

452

Leaf Sequencing Algorithms for Segmented Multileaf Collimation  

E-print Network

Leaf Sequencing Algorithms for Segmented Multileaf Collimation Srijit Kamath, Sartaj Sahni fluence map into a leaf sequence file that controls the movement of the MLC during radiation delivery. It is imperative that the fluence map delivered using the leaf sequence file is as close as possible to the fluence

Sahni, Sartaj K.

453

Parameterized Algorithms for Directed Maximum Leaf Problems  

E-print Network

Parameterized Algorithms for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 spanning tree, then D contains one with at least (n/2) 1/5 - 1 leaves. 1 Introduction The Maximum Leaf a digraph D, the Directed Maximum Leaf Out­Branching problem is the problem of finding an out­branching in D

Krivelevich, Michael

454

ZONATE LEAF SPOT (CAUSED BY CRISTULARIELLA MORICOLA)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Zonate leaf spot derives it name from the occurrence of large, circular leaf lesions with distinct concentric rings. Initially the leaf lesions are light tan in color and the concentric rings are symmetrical appearing as a bulls eye. Initial lesions are 5-10 mm in diameter and continue to expand...

455

Seasonal Conductivity and Embolism in the Roots and Stems of Two Clonal Ring-Porous Trees, Sassafras albidum (Lauraceae) and Rhus typhina (Anacardiaceae)  

Microsoft Academic Search

Seasonal xylem (wood) conductivity and embolism (air blockage) patterns were monitored in roots vs. stems of two clonal ring- porous tree species, Sassafras albidum and Rhus typhina, throughout 1996 and 1997. Stems of both species were 100% embolized in the early spring and became conductive by late June following leaf expansion and maturation of new earlywood vessels. Dyes indicated the

Laura L. Jaquish; Frank W. Ewers

2001-01-01

456

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2011 CFR

...percent may be waste. B4GFair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5GLow Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6GPoor Quality Green Leaf Immature, tight leaf...

2011-01-01

457

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2012 CFR

...percent may be waste. B4GFair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5GLow Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6GPoor Quality Green Leaf Immature, tight leaf...

2012-01-01

458

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...percent may be waste. B4GFair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5GLow Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6GPoor Quality Green Leaf Immature, tight leaf...

2013-01-01

459

7 CFR 29.1162 - Leaf (B Group).  

...percent may be waste. B4GFair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5GLow Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6GPoor Quality Green Leaf Immature, tight leaf...

2014-01-01

460

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...percent may be waste. B4GFair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5GLow Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6GPoor Quality Green Leaf Immature, tight leaf...

2010-01-01

461

On Number Representation  

E-print Network

Place value numbers, such as the binary or decimal numbers can be represented by the end vertices (leaf or pendant vertices) of rooted symmetrical trees. Numbers that consist of at most a fixed number of digits are represented by vertices that are equidistant from the root vertex and the corresponding number representations do not depend on the distance from the root vertex. In this paper, we introduce place value number systems which are representable by rooted symmetrical trees and in which the representation of a number depends on the distance of the corresponding vertex from the root vertex. Such dependence activates the role of zero in such a way as to render its function equivalent to that of any other single digit number. Thus, in addition to being a place value holder, the digit zero (just as any other single digit numeral) affects the value of a number regardless of its position. For example 012 is different, in the new systems, from 12. As such, these new number systems could be thought of as a natural development for the role of zero. We also illustrate how addition is performed in these newly constructed number systems. In addition to being mathematical structures which could be of mathematical interest, these new number systems could possibly have applications in computing and computing security.

Rafael I. Rofa

2013-10-30

462

STEM Disability Transition Group A representative from Royal Holloway, University of London will act as Chair.  

E-print Network

greater numbers of young people with disabilities developing STEM skills and working in STEM industries. Where a vote has to be taken, decisions will be by simple majority of members present. Decisions

Royal Holloway, University of London

463

Stem Cell Quick Guide: Stem Cell Basics What is a Stem Cell?  

E-print Network

Stem Cell Quick Guide: Stem Cell Basics What is a Stem Cell? Stem cells are the starting point from to line blood vessels. All of these highly specialized cells have to grow from unspecialized stem cells. Stem cells produce new cells by dividing. In the right conditions, these new cells can then continue

Schladow, S. Geoffrey

464

Hematopoietic stem cells: an overview.  

PubMed

Considerable efforts have been made in recent years in understanding the mechanisms that govern hematopoietic stem cell (HSC) origin, development, differentiation, self-renewal, aging, trafficking, plasticity and transdifferentiation. Hematopoiesis occurs in sequential waves in distinct anatomical locations during development and these shifts in location are accompanied by changes in the functional status of the stem cells and reflect the changing needs of the developing organism. HSCs make a choice of either self-renewal or committing to differentiation. The balance between self-renewal and differentiation is considered to be critical to the maintenance of stem cell numbers. It is still under debate if HSC can rejuvenate infinitely or if they do not possess ''true" self-renewal and undergo replicative senescence such as any other somatic cell. Gene therapy applications that target HSCs offer a great potential for the treatment of hematologic and immunologic diseases. However, the clinical success has been limited by many factors. This review is intended to summarize the recent advances made in the human HSC field, and will review the hematopoietic stem cell from definition through development to clinical applications. PMID:25457002

Mosaad, Youssef Mohamed

2014-12-01

465

The potential of biomonitoring of air quality using leaf characteristics of white willow (Salix alba L.).  

PubMed

In this study, we assess the potential of white willow (Salix alba L.) as bioindicator for monitoring of air quality. Therefore, shoot biomass, specific leaf area, stomatal density, stomatal pore surface, and stomatal resistance were assessed from leaves of stem cuttings. The stem cuttings were introduced in two regions in Belgium with a relatively high and a relatively low level of air pollution, i.e., Antwerp city and Zoersel, respectively. In each of these regions, nine sampling points were selected. At each sampling point, three stem cuttings of white willow were planted in potting soil. Shoot biomass and specific leaf area were not significantly different between Antwerp city and Zoersel. Microclimatic differences between the sampling points may have been more important to plant growth than differences in air quality. However, stomatal pore surface and stomatal resistance of white willow were significantly different between Zoersel and Antwerp city. Stomatal pore surface was 20% lower in Antwerp city due to a significant reduction in both stomatal length (-11%) and stomatal width (-14%). Stomatal resistance at the adaxial leaf surface was 17% higher in Antwerp city because of the reduction in stomatal pore surface. Based on these results, we conclude that stomatal characteristics of white willow are potentially useful indicators for air quality. PMID:20033771

Wuytack, Tatiana; Verheyen, Kris; Wuyts, Karen; Kardel, Fatemeh; Adriaenssens, Sandy; Samson, Roeland

2010-12-01

466

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

467

Leaf area dynamics of conifer forests  

SciTech Connect

Estimating the surface area of foliage supported by a coniferous forest canopy is critical for modeling its biological properties. Leaf area represents the surface area available for the interception of energy, the absorption of carbon dioxide, and the diffusion of water from the leaf to the atmosphere. The concept of leaf area is pertinent to the physiological and ecological dynamics of conifers at a wide range of spatial scales, from individual leaves to entire biomes. In fact, the leaf area of vegetation at a global level can be thought of as a carbon-absorbing, water-emitting membrane of variable thickness, which can have an important influence on the dynamics and chemistry of the Earth`s atmosphere over both the short and the long term. Unless otherwise specified, references to leaf area herein refer to projected leaf area, i.e., the vertical projection of needles placed on a flat plane. Total leaf surface area is generally from 2.0 to 3.14 times that of projected leaf area for conifers. It has recently been suggested that hemisurface leaf area, i.e., one-half of the total surface area of a leaf, a more useful basis for expressing leaf area than is projected area. This chapter is concerned with the dynamics of coniferous forest leaf area at different spatial and temporal scales. In the first part, we consider various hypotheses related to the control of leaf area development, ranging from simple allometric relations with tree size to more complex mechanistic models that consider the movement of water and nutrients to tree canopies. In the second part, we consider various aspects of leaf area dynamics at varying spatial and temporal scales, including responses to perturbation, seasonal dynamics, genetic variation in crown architecture, the responses to silvicultural treatments, the causes and consequences of senescence, and the direct measurement of coniferous leaf area at large spatial scales using remote sensing.

Margolis, H.; Oren, R.; Whitehead, D.; Kaufmann, M.R.

1995-07-01

468

Embryonic stem cells. Stem cell programs.  

PubMed

The availability of human embryonic stem cell lines provides an important tool for scientists to explore the fundamental mechanisms that regulate differentiation into specific cell types. When more is known about the mechanisms that govern these processes, human embryonic stem cells may be clinically useful in generating cell types that have been damaged or depleted by a variety of human diseases. The NIH is actively pursuing a variety of initiatives to promote this developing research field, while continuing and expanding its long-standing investment in adult stem cells and research. PMID:12738840

Zerhouni, Elias

2003-05-01

469

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

PubMed Central

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

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

2013-01-01

470

The circulative pathway of begomoviruses in the whitefly vector Bemisia tabaci - insights from studies with Tomato yellow leaf curl virus  

Microsoft Academic Search

Summary Our current knowledge concerning the transmission of begomoviruses by the whitefly vector Bemisia tabaci is based mainly on research performed on the Tomato yellow leaf curl virus (TYLCV) complex and on a number of viruses originating from the Old World, such as Tomato leaf curl virus , and from the New World, including Abutilon mosaic virus , Tomato mottle

HENRYK CZOSNEK; MIRIAM GHANIM; MURAD GHANIM

2002-01-01

471

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

Microsoft Academic Search

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

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

1988-01-01

472

Time to Reconsider Stem Cell Induction Strategies  

PubMed Central

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

Denker, Hans-Werner

2012-01-01

473

Environmental modification of yield and nutrient composition of 'Waldmann's Green' leaf lettuce  

NASA Technical Reports Server (NTRS)

Leaf number, dry weight, and nutrient composition of Lactuca sativa L. cv. Waldmann's Green leaves were compared following 9 days of treatment in a controlled environment room under various combinations of photosynthetic photon flux (PPF:350 vs 800 micromoles m-2 s-1), atmospheric CO2 level (ambient vs 1500 micromoles mol-1), and single-strength (1X:15 mM) vs double-strength (2X:30 mM) nitrogen (N) as NO3- alone or as NH4(+) + NO3- (1:5 molar ratio). CO2 enrichment greatly enhanced leaf number under all PPF and N conditions, but increased leaf dry weight only at high PPF. Conditions favoring high photosynthesis enhanced leaf starch content 3-fold, and protein content increased as much as 64% with 2X NH4(+)+NO3-. Free sugar content was 6 to 9% of leaf dry weight for all treatment combinations, while fat was 1.5 to 3.5%. Ash content varied from 15 to 20% of leaf dry weight. Modified controlled environments can be used to enhance the nutritional content as well as the yield of crops to be used for life support in space-deployed, self-sustaining human habitats. Leaf lettuce is a useful model crop for demonstrating the potential of nutritional value added by environmental manipulation.

Mitchell, C. A.; Chun, C.; Brandt, W. E.; Nielsen, S. S.

1997-01-01

474

Leaf architectural, vascular and photosynthetic acclimation to temperature in two biennials.  

PubMed

Acclimation of leaf features to growth temperature was investigated in two biennials (whose life cycle spans summer and winter seasons) using different mechanisms of sugar loading into exporting conduits, Verbascum phoeniceum (employs sugar-synthesizing enzymes driving symplastic loading through plasmodesmatal wall pores of phloem cells) and Malva neglecta (likely apoplastic loader transporting sugar via membrane transport proteins of phloem cells). In both species, acclimation to lower temperature involved greater maximal photosynthesis rates and vein density per leaf area in close correlation with modification of minor vein cellular features. While the symplastically loading biennial exhibited adjustments in the size of minor leaf vein cells (consistent with adjustment of the level of sugar-synthesizing enzymes), the putative apoplastic biennial exhibited adjustments in the number of cells (consistent with adjustment of cell membrane area for transporter placement). This upregulation of morphological and anatomical features at lower growth temperature likely contributes to the success of both the species during the winter. Furthermore, while acclimation to low temperature involved greater leaf mass per area in both species, this resulted from greater leaf thickness in V. phoeniceum vs a greater number of mesophyll cells per leaf area in M. neglecta. Both types of adjustments presumably accommodate more chloroplasts per leaf area contributing to photosynthesis. Both biennials exhibited high foliar vein densities (particularly the solar-tracking M. neglecta), which should aid both sugar export from and delivery of water to the leaves. PMID:24818515

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

2014-12-01

475

Rooting of clematis microshoots and stem cuttings in different substrates  

Microsoft Academic Search

Microshoots and softwood stem cuttings of five clematis varieties (Clematis section Atragene) were rooted in different substrates (perlite, peatperlite, and sandperlite). Microshoots rooted better and quicker than stem cuttings, independent of the substrate. Root dry mass of microshoots was more than twice as high compared to root dry mass of stem cuttings.For microshoots, number of primary roots was highest in

Silja Kreen; Margaret Svensson; Kimmo Rumpunen

2002-01-01

476

Dnmt3a is essential for hematopoietic stem cell differentiation  

Microsoft Academic Search

Loss of the de novo DNA methyltransferases Dnmt3a and Dnmt3b in embryonic stem cells obstructs differentiation; however, the role of these enzymes in somatic stem cells is largely unknown. Using conditional ablation, we show that Dnmt3a loss progressively impairs hematopoietic stem cell (HSC) differentiation over serial transplantation, while simultaneously expanding HSC numbers in the bone marrow. Dnmt3a-null HSCs show both

Grant A Challen; Deqiang Sun; Mira Jeong; Min Luo; Jaroslav Jelinek; Jonathan S Berg; Christoph Bock; Aparna Vasanthakumar; Hongcang Gu; Yuanxin Xi; Shoudan Liang; Yue Lu; Gretchen J Darlington; Alexander Meissner; Jean-Pierre J Issa; Lucy A Godley; Wei Li; Margaret A Goodell

2011-01-01

477

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

478

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

479

The relationship of leaf photosynthetic traits - V cmax and J max - to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta-analysis and modeling study.  

PubMed

Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (V cmax) and the maximum rate of electron transport (J max). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between V cmax and J max and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between V cmax and J max and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of V cmax and J max with leaf N, P, and SLA. V cmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of V cmax to leaf N. J max was strongly related to V cmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm(-2)), increasing leaf P from 0.05 to 0.22 gm(-2) nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of J max to V cmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting. PMID:25473475

Walker, Anthony P; Beckerman, Andrew P; Gu, Lianhong; Kattge, Jens; Cernusak, Lucas A; Domingues, Tomas F; Scales, Joanna C; Wohlfahrt, Georg; Wullschleger, Stan D; Woodward, F Ian

2014-08-01

480

Leaf hydraulic conductance is coordinated with leaf morpho-anatomical traits and nitrogen status in the genus Oryza.  

PubMed

Leaf hydraulic conductance (K leaf) is a major determinant of photosynthetic rate in plants. Previous work has assessed the relationships between leaf morpho-anatomical traits and K leaf with woody species, but there has been very little focus on cereal crops. The genus Oryza, which includes rice (Oryza sativa) and wild species (such as O. rufipogon cv. Griff), is ideal material for identifying leaf features associated with K leaf and gas exchange. Leaf morpho-anatomical traits, K leaf, leaf N content per leaf area, and CO2 diffusion efficiency were investigated in 11 Oryza cultivars. K leaf was positively correlated with leaf thickness and related traits, and therefore positively correlated with leaf mass per area and leaf N content per leaf area, and negatively with inter-veinal distance. K leaf was also positively correlated with leaf area and its related traits, and therefore negatively correlated with the proportion of minor vein length per area. In addition, coordination between K leaf and CO2 diffusion conductance in leaves was observed. We conclude that leaf morpho-anatomical traits and N content per leaf area strongly influence K leaf. Our results suggest that more detailed anatomical and structural studies are needed to elucidate the impacts of leaf feature traits on K leaf and gas exchange in grasses. PMID:25429002

Xiong, Dongliang; Yu, Tingting; Zhang, Tong; Li, Yong; Peng, Shaobing; Huang, Jianliang

2015-02-01

481

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

NASA Technical Reports Server (NTRS)

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

Carter, Gregory A.; Knapp, Alan K.

1999-01-01

482

MOLECULAR DETECTION OF A CLOSTEROVIRUS ASSOCIATED WITH APRICOT STEM PITTING IN SOUTHERN ITALY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Electrophoretic analysis of cortical and leaf tissue extracts from apricot trees of cv. 'Tyrinthos' from Apulia (southern Italy) affected by stem pitting, contained multiple double-stranded RNA (dsRNA) species, the largest with an estimated size of 15 kbp. A segment of 590 nucleotides, showing seque...