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1

Solanum nigrum: an indigenous weed reservoir for a tomato yellow leaf curl geminivirus in southern Spain  

Microsoft Academic Search

A tomato yellow leaf curl geminivirus (TYLCV-AL), was first identified in tomato plants in Almeria, southern Spain in 1992. This virus is transmitted by the tobacco whitefly, Bemisia tabaci (Gennadius), and is presently infecting tomato crops throughout the south eastern region of Spain. Solanum nigrum, collected from a field in south east Spain and exhibiting leaf curl symptoms, was squash

I. D. Bedford; A. Kelly; G. K. Banks; R. W. Briddon; J. L. Cenis; P. G. Markham

1998-01-01

2

Molecular characterization of Chilli leaf curl virus and satellite molecules associated with leaf curl disease of Amaranthus spp.  

PubMed

Amaranthus, collectively known as amaranth, is an annual or short-lived perennial plant used as leafy vegetables, cereals and for ornamental purposes in many countries including India. During 2011, leaf samples of Amaranthus plants displaying leaf curling, leaf distortion, leaf crinkling and yellow leaf margins were collected from Banswara district, Rajasthan in India. Full-length clones of a monopartite begomovirus, a betasatellite and an alphasatellite were characterized. The complete nucleotide sequence of the isolated begomovirus features as a typical 'Old World' begomovirus with the highest nucleotide per cent identity with Chilli leaf curl virus and hence, considered as an isolate of Chilli leaf curl virus. The complete nucleotide sequences of betasatellite and alphasatellite possess maximum nucleotide identity with Tomato yellow leaf curl Thailand betasatellite and Chilli leaf curl alphasatellite, respectively. This is the first report of the association of chilli-infecting begomovirus and satellite molecules infecting a new host, Amaranthus, causing leaf curl disease. PMID:24368759

George, B; Kumar, R Vinoth; Chakraborty, S

2014-04-01

3

A worldwide survey of tomato yellow leaf curl viruses  

Microsoft Academic Search

Summary.  ?The name tomato yellow leaf curl virus (TYLCV) has been given to several whitefly-transmitted geminiviruses affecting tomato\\u000a cultures in many tropical and subtropical regions. Hybridization tests with two DNA probes derived from a cloned isolate of\\u000a TYLCV from Israel (TYLCV-ISR) were used to assess the affinities of viruses in naturally infected tomato plants with yellow\\u000a leaf curl or leaf curl

H. Czosnek; H. Laterrot

1997-01-01

4

Association of a recombinant Cotton leaf curl Bangalore virus with yellow vein and leaf curl disease of okra in India.  

PubMed

A begomovirus isolate (OY136A) collected from okra plants showing upward leaf curling, vein clearing, vein thickening and yellowing symptoms from Bangalore rural district, Karnataka, India was characterized. The sequence comparisons revealed that, this virus isolate share highest nucleotide identity with isolates of Cotton leaf curl Bangalore virus (CLCuBV) (AY705380) (92.8 %) and Okra enation leaf curl virus (81.1-86.2 %). This is well supported by phylogentic analysis showing, close clustering of the virus isolate with CLCuBV. With this data, based on the current taxonomic criteria for the genus Begomovirus, the present virus isolate is classified as a new strain of CLCuBV, for which CLCuBV-[India: Bangalore: okra: 2006] additional descriptor is proposed. The betasatellite (KC608158) associated with the virus is having more than 95 % sequence similarity with the cotton leaf curl betasatellites (CLCuB) available in the GenBank.The recombination analysis suggested, emergence of this new strain of okra infecting begomovirus might have been from the exchange of genetic material between BYVMV and CLCuMuV. The virus was successfully transmitted by whitefly and grafting. The host range of the virus was shown to be very narrow and limited to two species in the family Malvaceae, okra (Abelmoschus esculentus) and hollyhock (Althaea rosea), and four in the family Solanaceae. PMID:24426275

Venkataravanappa, V; Lakshminarayana Reddy, C N; Devaraju, A; Jalali, Salil; Krishna Reddy, M

2013-09-01

5

Predominance of tomato leaf curl Gujarat virus as a monopartite begomovirus: association with tomato yellow leaf curl Thailand betasatellite.  

PubMed

Tomato leaf curl is a serious malady in the state of Maharashtra, India, causing nearly 100 % yield loss. An extensive survey was done in the affected fields of tomato in the year 2008, and members of three species of begomoviruses were identified as causing the disease. More than 60 % of the samples from diseased plants were infected with tomato leaf curl Gujarat virus (ToLCGuV). Isolates collected from these fields differed from the Varanasi isolate of ToLCGuV in not having a DNA B component. Instead, they were like typical Old World monopartite begomoviruses in that they were associated with only one betasatellite, tomato yellow leaf curl Thailand betasatellite (TYLCTHB). ToLCGuV alone is readily infectious, expressing systemic symptoms in Nicotiana benthamiana and tomato. Co-inoculation of ToLCGuV with TYLCTHB, increased symptom severity and reduced the incubation time required for symptom expression. ToLCGuV successfully interacted with heterologous DNA B component of ToLCNDV [IN:Pun:JID:08], and co-inoculation of these two resulted in yellow mottling symptoms that were typical of DNA B. PMID:22983111

Jyothsna, P; Rawat, Ramaveer; Malathi, V G

2013-01-01

6

Tomato leaf curl Joydebpur virus: a monopartite begomovirus causing severe leaf curl in tomato in West Bengal.  

PubMed

A begomovirus was isolated from tomato plants showing leaf curl and stunting symptoms in farmers' fields near the district of Kalyani, West Bengal, India. Viral genomic components amplified by rolling-circle amplification were cloned and sequenced. The genome organization of this virus was found to be similar to those of Old World monopartite begomovirus, with DNA A and a betasatellite component. Neither alphasatellite nor DNA B component was detected. The begomovirus showed highest sequence identity of 93.6% to tomato leaf curl Joydebpur virus (ToLCJoV-[IN:Kal:Chi:06]) and was thus identified to be an isolate of ToLCJoV. The betasatellite isolated from these samples was identified as tomato leaf curl Joydebpur betasatellite. ToLCJoV-[IN:Kal:Tom:08] alone induced severe symptoms in Solanum lycopersicum, N. benthamiana and N. glutinosa plants, and its severity was enhanced when co-inoculated with the cognate betasatellite. ToLCJoV-[IN:Kal:Tom:08] trans-replicated four more non-cognate betasatellites and induced severe symptoms in N. benthamiana and tomato. Since DNA A replicated efficiently and caused systemic symptom expression, it is hypothesized that ToLCJoV is essentially a monopartite virus, which could have acquired a betasatellite from an unknown source. PMID:22918555

Tiwari, Neha; Singh, Veer B; Sharma, P K; Malathi, V G

2013-01-01

7

Evidence of local evolution of tomato-infecting begomovirus species in West Africa: characterization of tomato leaf curl Mali virus and tomato yellow leaf crumple virus from Mali.  

PubMed

Tomato yellow leaf curl (TYLC) and tomato leaf curl (ToLC) diseases are serious constraints to tomato production in Mali and other countries in West Africa. In 2003 and 2004, samples of tomato showing virus-like symptoms were collected during a survey of tomato virus diseases in Mali. Three predominant symptom phenotypes were observed: (1) TYLC/ToLC (stunted upright growth and upcurled leaves with interveinal yellowing and vein purpling), (2) yellow leaf crumple and (3) broccoli or bonsai (severe stunting and distorted growth). Squash blot (SB) hybridization with a general begomovirus probe and/or SB/PCR analyses revealed begomovirus infection in plants with each of these symptom phenotypes and no evidence of phytoplasma infection. Sequence analysis of PCR-amplified begomovirus fragments revealed two putative new begomovirus species associated with the TYLC/ToLC and yellow leaf crumple symptom phenotypes, respectively. Full-length clones of these begomoviruses were obtained using PCR and overlapping primers. When introduced into N. benthamiana and tomato plants, these clones induced upward leaf curling and crumpling (the TYLC/ToLC-associated begomovirus) or downward leaf curl/yellow mottle (yellow leaf crumple-associated begomovirus) symptoms. Thus, these begomoviruses were named tomato leaf curl Mali virus (ToLCMLV) and tomato yellow leaf crumple virus (ToYLCrV). The genome organization of both viruses was similar to those of other monopartite begomoviruses. ToLCMLV and ToYLCrV were most closely related to each other and to tobacco leaf curl Zimbabwe virus (TbLCZV-[ZW]) and tomato curly stunt virus from South Africa (ToCSV-ZA). Thus, these likely represent tomato-infecting begomoviruses that evolved from indigenous begomoviruses on the African continent. Mixed infections of ToLCMLV and ToYLCrV in N. benthamiana and tomato plants resulted in more severe symptoms than in plants infected with either virus alone, suggesting a synergistic interaction. Agroinoculation experiments indicated that both viruses induced symptomatic infections in tomato and tobacco, whereas neither virus induced disease symptoms in pepper, common bean, small sugar pumpkin, African eggplant, or Arabidopsis. Virus-specific PCR primers were developed for detection of ToLCMLV and ToYLCrV and will be used to further investigate the distribution and host range of these viruses. PMID:18278427

Zhou, Y-C; Noussourou, M; Kon, T; Rojas, M R; Jiang, H; Chen, L-F; Gamby, K; Foster, R; Gilbertson, R L

2008-01-01

8

Suppressors of RNA silencing encoded by tomato leaf curl betasatellites.  

PubMed

Virus encoded RNA-silencing suppressors (RSSs) are the key components evolved by the viruses to counter RNA-silencing defense of plants. Whitefly-transmitted begomoviruses infecting tomato crop code for five different proteins, ORF AC4, ORF AC2 and ORF AV2 in DNA-A component, ORF BV1 in DNA-B and ORF beta C1 in satellite DNA beta which are predicted to function as silencing suppressors. In the present study suppressor function of ORF beta C1 of three betasatellites Tomato leaf curl Bangalore betasatellite ToLCBB-[IN:Hess:08], Cotton leaf curl Multan betasatellite CLCuMB-[IN:Sri:02] and Luffa leaf distortion betasatellite LuLDB-[IN:Lu:04] were examined. Agroinfiltration of GFP-silenced Nicotiana tabaccum cv. Xanthi with the cells expressing betaC1 protein resulted in reversal of silenced GFP expression. GFP-siRNA level was more than 50-fold lower compared to silenced plants in plants infiltrated with betaC1 gene from ToLCBB. However, in the case of 35S-beta C1 CLCuMB and 35S- beta C1 LuLDB construct, although GFP was expressed, siRNA level was not reduced, indicating that the step at which beta C1 interfere in RNA-silencing pathway is different. PMID:23385812

Shukla, Richa; Dalal, Sunita; Malathi, V G

2013-03-01

9

Regulation of leaf morphology by microRNA394 and its target LEAF CURLING RESPONSIVENESS.  

PubMed

The present study identified Arabidopsis miR394 and its target, an F-box (SKP1-Cullin/CDC53-F-box) gene At1g27340 (here referred to as LEAF CURLING RESPONSIVENESS, LCR), for regulation of leaf curling-related morphology. The loss-of-function lcr mutants exhibit pleiotropic defects with semi-dwarfism, altered leaf shape and a shorter stem. Overexpression of an miR394-resistant version of LCR under the 35S promoter (35S:m5LCR) and target mimicry MIM394 resulted in a curled-down leaf defect. Conversely, transgenic plants overexpressing 35S:MIR394a/b display a curled-up leaf phenotype. Detailed analyses show that there is a certain level of LCR that is optimal for leaf morphology, but lower or higher levels lead to abnormal leaf development, indicating that expression of miR394 in the leaf lamina is necessary for proper leaf morphology. Because the phytohormone auxin plays a crucial role in leaf morphogenesis and patterning, the DR5-GUS reporter gene was used to monitor the auxin response. We show that DR5 expression patterns in lcr and 35S::m5LCR plants were significantly different from those in the wild type. Also, overexpression of LCR in 35S::m5LCR plants drastically decreased the expression of the auxin-responsive genes IAA3, AXR3 and IAMT1, whereas increased expression of the genes was found in 35S::MIR394a plants. These results indicate that miR394 and its target LCR are involved in the regulation of leaf development. PMID:22619471

Song, Jian Bo; Huang, Si Qi; Dalmay, Tamas; Yang, Zhi Min

2012-07-01

10

Curl  

NSDL National Science Digital Library

The cursor object in BField is able to calculate the vector curl of the field. Enter x and y field components using this applet's simple user interface and compare the numerical calculation to the analytic answer.

Christian, Wolfgang; Belloni, Mario

2008-02-09

11

MicroRNA profiling of tomato leaf curl new delhi virus (tolcndv) infected tomato leaves indicates that deregulation of mir159\\/319 and mir172 might be linked with leaf curl disease  

Microsoft Academic Search

BACKGROUND: Tomato leaf curl virus (ToLCV), a constituent of the genus Begomovirus, infects tomato and other plants with a hallmark disease symptom of upward leaf curling. Since microRNAs (miRs) are known to control plants developmental processes, we evaluated the roles of miRNAs in Tomato leaf curl New Delhi virus (ToLCNDV) induced leaf curling. RESULTS: Microarray analyses of miRNAs, isolated from

Afsar R Naqvi; Sunil K Mukherjee

2010-01-01

12

[Molecular detection of tomato yellow leaf curl virus (TYLCV)].  

PubMed

Tomato yellow leaf curl virus (TYLCV) is currently considered as one of the most devastating viruses in cultivated tomatoes (Solanum lycopersicum) worldwide. We reported here the development of a PCR-based method to quickly detect TYLCV using the primer pairs (TYLCV-F: 5'-ACG CAT GCC TCT AAT CCA GTG TA-3' and TYLCV-R: 5'-CCA ATA AGG CGT AAG CGT GTA GAC-3'), which was designed based on the genome sequence of TYLCV. A TYLCV-specific band of 543 bp was amplified from infected tomato plants. This protocol provides a rapid, reliable, and sensitive tool for molecular detection and identification of TYLCV in the industrial seedling and virus resistance breeding to facilitate safe and sustainable production of tomato. PMID:22425956

Li, Chang-Bao; Cui, Yan-Ling; Zhang, Li-Ying; Li, Chuan-You

2012-03-01

13

Transcript mapping of Cotton leaf curl Burewala virus and its cognate betasatellite, Cotton leaf curl Multan betasatellite  

PubMed Central

Background Whitefly-transmitted geminiviruses (family Geminiviridae, genus Begomovirus) are major limiting factors for the production of numerous dicotyledonous crops throughout the warmer regions of the world. In the Old World a small number of begomoviruses have genomes consisting of two components whereas the majority have single-component genomes. Most of the monopartite begomoviruses associate with satellite DNA molecules, the most important of which are the betasatellites. Cotton leaf curl disease (CLCuD) is one of the major problems for cotton production on the Indian sub-continent. Across Pakistan, CLCuD is currently associated with a single begomovirus (Cotton leaf curl Burewala virus [CLCuBuV]) and the cotton-specific betasatellite Cotton leaf curl Multan betasatellite (CLCuMuB), both of which have recombinant origins. Surprisingly, CLCuBuV lacks C2, one of the genes present in all previously characterized begomoviruses. Virus-specific transcripts have only been mapped for few begomoviruses, including one monopartite begomovirus that does not associate with betasatellites. Similarly, the transcripts of only two betasatellites have been mapped so far. The study described has investigated whether the recombination/mutation events involved in the evolution of CLCuBuV and its associated CLCuMuB have affected their transcription strategies. Results The major transcripts of CLCuBuV and its associated betasatellite (CLCuMuB) from infected Nicotiana benthamiana plants have been determined. Two complementary-sense transcripts of ~1.7 and ~0.7 kb were identified for CLCuBuV. The ~1.7 kb transcript appears similar in position and size to that of several begomoviruses and likely directs the translation of C1 and C4 proteins. Both complementary-sense transcripts can potentially direct the translation of C2 and C3 proteins. A single virion-sense transcript of ~1 kb, suitable for translation of the V1 and V2 genes was identified. A predominant complementary-sense transcript was also confirmed for the betasatellite. Conclusions Overall, the transcription of CLCuBuV and the recombinant CLCuMuB is equivalent to earlier mapped begomoviruses/betasatellites. The recombination events that featured in the origins of these components had no detectable effects on transcription. The transcripts spanning the mutated C2 gene showed no evidence for involvement of splicing in restoring the ability to express intact C2 protein. PMID:23106938

2012-01-01

14

Identification of DNA Components Required for Induction of Cotton Leaf Curl Disease  

Microsoft Academic Search

Cotton leaf curl disease (CLCuD) is a major constraint to cotton production in Pakistan. Infectious clones of the monopartite begomovirus cotton leaf curl virus (CLCuV), associated with diseased cotton, are unable to induce typical symptoms in host plants. We have identified and isolated a single-stranded DNA molecule approximately 1350 nucleotides in length which, when coinoculated with the begomovirus to cotton,

R. W. Briddon; S. Mansoor; I. D. Bedford; M. S. Pinner; K. Saunders; Y. Zafar; K. A. Malik; P. G. Markham

2001-01-01

15

Posttranscriptional gene silencing in controlling viruses of the Tomato yellow leaf curl virus complex  

Microsoft Academic Search

Summary.  Tomato yellow leaf curl disease (TYLCD) is caused by a group of geminiviruses that belong to the Tomato yellow leaf curl virus\\u000a (TYLCV) complex and are transmitted by the whitefly (Bemisia tabaci Genn.). The disease causes great yield losses in many countries throughout the Mediterranean region and the Middle East.\\u000a In this study, the efficacy of post-transcriptional gene silencing (PTGS)

M. K. Abhary; G. H. Anfoka; M. K. Nakhla; D. P. Maxwell

2006-01-01

16

Infectious clones of Tomato leaf curl Palampur virus with a defective DNA B and their pseudo-recombination with Tomato leaf curl New Delhi virus  

PubMed Central

Background Tomato leaf curl Palampur virus (ToLCPMV) is a bipartite begomovirus which has been reported from India and Iran but infectious clones have not been obtained. We have previously shown the association of Zucchini yellow mosaic virus (ZYMV), a potyvirus, with severe leaf curl disease of muskmelon in Pakistan. However, the severity of symptoms in the field and yield losses led us to believe that some other agent, such as a begomovirus, could be associated with the disease. Results A bipartite begomovirus associated with a severe yellow leaf curl disease on muskmelon in Pakistan has been characterized. Analysis of the complete nucleotide sequence of the DNA A and DNA B components of the begomovirus showed that it has the highest DNA sequence identity with ToLCPMV. However, the gene encoding the nuclear shuttle protein (NSP) was truncated in comparison to previously characterised isolates. Agrobacterium-mediated inoculation of Nicotiana benthamiana with the ToLCPMV clones obtained here did not result in symptoms. However, inoculation of plants with the DNA A component of ToLCPMV and the DNA B component of Tomato leaf curl New Delhi virus (ToLCNDV) lead to systemic infection with leaf curl symptoms. This suggested that the lack of infectivity of the ToLCPMV clones was due to the defect in DNA B. The DNA B of ToLCPMV was able to move systemically when inoculated with DNA A of the either virus. Agro-infiltration of muskmelon with the DNA A and DNA B components of ToLCPMV did not lead to symptomatic infection whereas inoculation with the DNA A with the DNA B of ToLCNDV resulted in a hypersensitive response (HR) along the veins. Additionally, agro-infiltration of muskmelon with a construct for the expression of the NSP gene of ToLCNDV under the control of the cauliflower mosaic virus 35S promoter induced a HR, suggesting that this is the gene causing the HR. Conclusions Both ToLCPMV and ZYMV are associated with muskmelon leaf curl disease in Pakistan. However, the ToLCPMV variant identified in association with ZYMV has a defective NSP. The results suggest that a variant with a defective NSP may have been selected for in muskmelon, as this protein is an avirulence determinant in this species, and possibly that infection requires the synergistic interaction with ZYMV. PMID:21496256

2011-01-01

17

Molecular characterization of begomoviruses and DNA satellites associated with okra leaf curl disease in Cameroon.  

PubMed

Okra leaf curl disease (OLCD) is the most important viral disease of okra in West Africa. In this study, a complex of begomoviruses and associated DNA satellites were identified in symptomatic okra plants from southwestern Cameroon. Sequence analyses showed that two of the plants (Lik1 and Njo5) were infected with a begomovirus being a recombinant of cotton leaf curl Gezira virus (CLCuGeV) and okra yellow crinkle virus (OYCrV). The recombinant genome shared highest nucleotide identity with isolates of CLCuGeV at 87.8% and is therefore considered to be member of a new begomovirus species, Okra leaf curl Cameroon virus (OLCuCMV). One plant (Mue5) was infected by a begomovirus with 95.8% nucleotide identy to CLCuGeV, while in the plants Lik1, Mue1 and Njo5, a begomovirus was identified showing highest nucleotide identity at 93.7% with OYCrV. The nucleotide comparisons and phylogenetic analyses suggest that these isolates represent new Cameroonian strains of CLCuGeV and OYCrV (CLCuGeV-CM and OYCrV-CM). Mixed infection of OLCuCMV and OYCrV-CM was found in two of the plants. A betasatellite and two divergent alphasatellites were also associated with the begomoviruses. The betasatellite was identified as cotton leaf curl Gezira betasatellite (CLCuGeB) with the highest nucleotide identity at 93.3% to other African isolates of CLCuGeB. The alphasatellites, herein named Alpha-1 and Alpha-2, shared 97.3% and 95.2% identity, respectively, with cotton leaf curl Gezira alphasatellite (CLCuGeA) and okra leaf curl Burkina Faso alphasatellite (OLCuBFA). These collective results emphasize the extent of diversity among okra-infecting begomovirus-satellite complexes in western Africa. PMID:23535770

Leke, Walter N; Sattar, Muhammad N; Ngane, Emilia B; Ngeve, Jacob M; Kvarnheden, Anders; Brown, Judith K

2013-06-01

18

First report of an alphasatellite associated with Okra enation leaf curl virus.  

PubMed

An alphasatellite DNA associated with Okra enation leaf curl virus (OELCuV) which causes enation and leaf curling in okra (Abelmoschus esculentus) plants was characterized. The full-length DNA comprises 1,350 nucleotides and shows typical genome organization of an alphasatellite. It shows the highest nucleotide sequence identity (79.7 %) to Hollyhock yellow vein virus-associated symptomless alphasatellite (HoYVSLA). This is the first report of the association of an alphasatellite with OELCuV from India. PMID:23475199

Chandran, S A; Packialakshmi, R M; Subhalakshmi, K; Prakash, C; Poovannan, K; Nixon Prabu, A; Gopal, P; Usha, R

2013-06-01

19

Identification of a Novel Circular Single-Stranded DNA Associated with Cotton Leaf Curl Disease in Pakistan  

Microsoft Academic Search

Recent reports have suggested that cotton leaf curl virus (CLCuV), a geminivirus of the genus Begomovirus, may be responsible for cotton leaf curl disease in Pakistan. However, the causal agent of the disease remains unclear as CLCuV genomic components resembling begomovirus DNA A are unable to induce typical disease symptoms when reintroduced into plants. All attempts to isolate a genomic

Shahid Mansoor; Sultan H. Khan; Aftab Bashir; Muhammed Saeed; Yusuf Zafar; Kauser A. Malik; Rob Briddon; John Stanley; Peter G. Markham

1999-01-01

20

Strains of a new bipartite begomovirus, pepper yellow leaf curl Indonesia virus, in leaf-curl-diseased tomato and yellow-vein-diseased ageratum in Indonesia.  

PubMed

The complete nucleotide sequences of begomoviruses from pepper with leaf curl and yellowing symptoms, tomato with leaf curl symptoms, and ageratum with yellow vein in Indonesia were determined. On the basis of genome organization and sequence homology, they were proposed to belong to a new species, Pepper yellow leaf curl Indonesia virus (PepYLCIV), which includes the new strains PepYLCIV-Tomato and PepYLCIV-Ageratum. These viruses had bipartite genomes. Pepper virus DNAs from Indonesia (PepYLCIV, PepYLCIV-Tomato and PepYLCIV-Ageratum DNA-As) were noticeably distinct, forming a separate branch from the viruses infecting pepper. Considerable divergence was observed in the common region (CR) of the genomic components of PepYLCIV (77%), PepYLCIV-Tomato (82%) and PeYLCIV-Ageratum (75%). A stem-loop-forming region and a Rep-binding motif were identical in the CR of the three viruses. The CRs of PepYLCIV-Ageratum DNA-A was approximately 10 nucleotides longer than that of PepYLCIV DNA-A and PepYLCIV-Tomato DNA-A. A similar insertion was also found in the CR of PepYLCIV-Ageratum DNA-B. PepYLCIV DNA-A alone was infectious in pepper and Nicotiana benthamiana plants, and association with DNA-B increased symptom severity. PMID:19015934

Sakata, Jyun-Ji; Shibuya, Yutaka; Sharma, Pradeep; Ikegami, Masato

2008-01-01

21

A new betasatellite associated with cotton leaf curl Burewala virus infecting tomato in India: influence on symptoms and viral accumulation.  

PubMed

A begomovirus and its associated alpha- and betasatellite were detected in tomato plants affected with leaf curl disease. Based on a nucleotide sequence identity of 99 %, this begomovirus was designated an isolate of cotton leaf curl Burewala virus (CLCuBuV). The alphasatellite exhibited 93 % sequence identity to cotton leaf curl Burewala alphasatellite (CLCuBuA) and is hence referred to here as a variant of CLCuBuA. The detected betasatellite was recombinant in nature and showed 70 % sequence identity to the known betasatellites. Inoculation of healthy tomato with CLCuBuV plus betasatellite, either in the presence or the absence of alphasatellite, led to typical leaf curling, while inoculation with CLCuBuV in the absence of betasatellite resulted in mild symptoms. This confirmed the role of the betasatellite in expression of disease symptoms. We propose to name the newly detected betasatellite tomato leaf curl Hajipur betasatellite (ToLCHJB). PMID:23361863

Kumar, Jitendra; Gunapati, Samatha; Singh, Sudhir P; Kumar, Abhinav; Lalit, Adarsh; Sharma, Naresh C; Puranik, Rekha; Tuli, Rakesh

2013-06-01

22

Status of Tomato Yellow Leaf Curl Virus in Tomato in the Western Hills of Nepal  

Microsoft Academic Search

Tomato cultivation in rainy season is being endangered and is becoming less profitable because of tomato yellow leaf curl virus (TYLCV) infection. Studies were conducted at Agriculture Research Station, Lumle to assess the incidence of TYLCV and associated yield losses in various commercial tomato growing pockets of the western hills during the period of 1995 and 1997. The studies revealed

Sita R Ghimire; Phul P Subedi; Sylvia K Green

23

The Spread of Tomato Yellow Leaf Curl Virus from the Middle East to the World  

Microsoft Academic Search

The ongoing global spread of Tomato yellow leaf curl virus (TYLCV; Genus Begomovirus, Family Geminiviridae) represents a serious looming threat to tomato production in all temperate parts of the world. Whereas determining where and when TYLCV movements have occurred could help curtail its spread and prevent future movements of related viruses, determining the consequences of past TYLCV movements could reveal

Pierre Lefeuvre; Darren P. Martin; Gordon Harkins; Philippe Lemey; Alistair J. A. Gray; Sandra Meredith; Francisco Lakay; Adérito Monjane; Jean-Michel Lett; Arvind Varsani; Jahangir Heydarnejad

2010-01-01

24

Tomato leaf curl virus satellite DNA as a gene silencing vector activated by helper virus infection  

Microsoft Academic Search

Tomato leaf curl virus (TLCV) satellite DNA (sat-DNA) constructs containing functional segments of the cauliflower mosaic virus (CaMV) 35S promoter, replicate in tobacco in the presence of helper TLCV and silence GUS activity in transgenic tobacco plants containing a CaMV 35S-GUS expression cassette. We have analysed these plants for evidence of the hallmarks of silencing. The GUS transcript was not

Dongmei Li; Seyed Ali Akbar Behjatnia; Ian Barry Dry; Amanda Ruth Walker; John Wesley Randles; Mohammad Ali Rezaian

2008-01-01

25

Evidence of local evolution of tomato-infecting begomovirus species in West Africa: characterization of tomato leaf curl Mali virus and tomato yellow leaf crumple virus from Mali  

Microsoft Academic Search

Tomato yellow leaf curl (TYLC) and tomato leaf curl (ToLC) diseases are serious constraints to tomato production in Mali and\\u000a other countries in West Africa. In 2003 and 2004, samples of tomato showing virus-like symptoms were collected during a survey\\u000a of tomato virus diseases in Mali. Three predominant symptom phenotypes were observed: (1) TYLC\\/ToLC (stunted upright growth\\u000a and upcurled leaves

Y.-C. Zhou; M. Noussourou; T. Kon; M. R. Rojas; H. Jiang; L.-F. Chen; K. Gamby; R. Foster; R. L. Gilbertson

2008-01-01

26

Molecular analysis of new isolates of Tomato leaf curl Philippines virus and an associated betasatellite occurring in the Philippines.  

PubMed

Three new begomovirus isolates and one betasatellite were obtained from a tomato plant exhibiting leaf curl symptom in Laguna, the Philippines. Typical begomovirus DNA components representing the three isolates (PH01, PH02 and PH03) were cloned, and their full-length sequences were determined to be 2754 to 2746 nucleotides. The genome organizations of these isolates were similar to those of other Old World monopartite begomoviruses. The sequence data indicated that PH01 and PH02 were variants of strain B of the species Tomato leaf curl Philippines virus, while PH03 was a variant of strain A of the species Tomato leaf curl Philippines virus. These isolates were designated ToLCPV-B[PH:Lag1:06], ToLCPV-B[PH:Lag2:06], and ToLCPV-A[PH:Lag3:06], respectively. Phylogenetic analysis revealed that the present isolates form a separate monophyletic cluster with indigenous begomoviruses reported earlier in the Philippines. A betasatellite isolated from same sample belongs to the betasatellite species Tomato leaf curl Philippines betasatellite and designated Tomato leaf curl Philippines betasatellite-[Philippines:Laguna1:2006], ToLCPHB-[PH:Lag1:06]. When co-inoculated with this betasatellite, tomato leaf curl Philippines virus induced severe symptoms in N. benthamiana and Solanum lycopersicum plants. Using a PVX-mediated transient assay, we found that the C4 and C2 proteins of tomato leaf curl Philippines virus and the ?C1 protein of ToLCPHB-[PH:Lag1:06] function as a suppressor of RNA silencing. PMID:21053032

Sharma, Pradeep; Matsuda, N; Bajet, N B; Ikegami, M

2011-02-01

27

Lamium amplexicaule (Lamiaceae): a weed reservoir for tomato yellow leaf curl virus (TYLCV) in Korea.  

PubMed

After the first identification of tomato yellow leaf curl virus (TYLCV) in the southern part of Korea in 2008, TYLCV has rapidly spread to tomato farms in most regions of Korea. From 2008 to 2010, a survey of natural weed hosts that could be reservoirs of TYLCV was performed in major tomato production areas of Korea. About 530 samples were collected and identified as belonging to 25 species from 11 families. PCR and Southern hybridization were used to detect TYLCV in samples, and replicating forms of TYLCV DNA were detected in three species (Achyranthes bidentata, Lamium amplexicaule, and Veronica persica) by Southern hybridization. TYLCV transmission mediated by Bemisia tabaci from TYLCV-infected tomato plants to L. amplexicaule was confirmed, and TYLCV-infected L. amplexicaule showed symptoms such as yellowing, stunting, and leaf curling. TYLCV from infected L. amplexicaule was also transmitted to healthy tomato and L. amplexicaule plants by B. tabaci. The rate of infection of L. amplexicaule by TYLCV was similar to that of tomato. This report is the first to show that L. amplexicaule is a reservoir weed host for TYLCV. PMID:24327090

Kil, Eui-Joon; Park, Jungan; Lee, Hyejung; Kim, Jaedeok; Choi, Hong-Soo; Lee, Kyeong-Yeoll; Kim, Chang-Seok; Lee, Sukchan

2014-06-01

28

Functional characterization of ?C1 gene of Cotton leaf curl Multan betasatellite.  

PubMed

Whitefly-transmitted Begomoviruses having circular single stranded DNA genome cause severe leaf curl diseases in the tropical and subtropical region. The majority of Old World monopartite begomoviruses with DNA A component is associated with a satellite DNA of 1.3 kb length referred to as betasatellites. The presence of betasatellite is required to express typical symptoms in the primary hosts. Increased symptom expression in betasatellite's presence is attributed to a 13-15 kDa ?C1 protein encoded by the ?C1 gene on complementary sense strand. The exact mechanism by which the ?C1 protein contributes to the symptoms' severity and helper viral DNA's accumulation is not yet understood. Here, we studied the ?C1 protein of Cotton leaf curl Multan betasatellite, associated with mono and bipartite begomoviruses. The ?C1 protein was expressed in prokaryotic system as 6XHis-?C1 fusion protein and recombinant protein showed size- and sequence-specific DNA binding activity. The host proteins which may interact with ?C1 were identified by binding ?C1 recombinant protein with heptapeptide in phage display library. The ?C1-interacting host proteins predicted belong to metabolic and defense pathways, indicating that ?C1 protein has a pivotal role in viral pathogenicity. PMID:23054431

Tiwari, Neha; Sharma, P K; Malathi, V G

2013-02-01

29

Regional changes in the sequence of cotton leaf curl multan betasatellite.  

PubMed

Cotton leaf curl disease (CLCuD) in Pakistan and northwestern India is caused by monopartite begomoviruses in association with an essential, disease-specific satellite, Cotton leaf curl Multan betasatellite (CLCuMB). Following a recent upsurge in CLCuD problems in Sindh province (southern Pakistan), sequences of clones of CLCuMB were obtained from Sindh and Punjab province (central Pakistan), where CLCuD has been a problem since the mid-1980s. The sequences were compared to all sequences of CLCuMB available in the databases. Analysis of the sequences shows extensive sequence variation in CLCuMB, most likely resulting from recombination. The range of sequence variants differ between Sindh, the Punjab and northwestern India. The possible significance of the findings with respect to movement of the CLCuD between the three regions is discussed. Additionally, the lack of sequence variation within the only coding sequence of CLCuMB suggests that the betasatellite is not involved in resistance breaking which became a problem after 2001 in the Punjab and subsequently also in northwestern India. PMID:24859342

Akhtar, Sohail; Tahir, Muhammad Nouman; Baloch, Ghulam Rasool; Javaid, Shaista; Khan, Ali Qaiser; Amin, Imran; Briddon, Rob W; Mansoor, Shahid

2014-05-01

30

Pathogenicity and insect transmission of a begomovirus complex between tomato yellow leaf curl virus and Ageratum yellow vein betasatellite.  

PubMed

Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein betasatellite (AYVB) are members of the genus Begomovirus (family Geminiviridae). TYLCV and AYVB have been found in Japan over the last 15 years, and are associated with tomato leaf curl and the tomato yellow leaf curl diseases (TYLCD). AYVB is also associated with some monopartite begomoviruses. We have cloned both TYLCV and AYVB and demonstrated that TYLCV can trans-replicate with AYVB in Nicotiana benthamiana and tomato plants. A mixed infection of TYLCV and AYVB induced more severe symptoms of upward leaf curl, stunting, vein thickening, and swelling compared with TYLCV infection alone. The symptoms induced by infection of AYVB included a rise in abnormal cell proliferation, and pigmentation around leaf vein tissues. This is the first study to show that a complex of TYLCV and AYVB can be transmitted by vector insects among tomato plants. These results indicate that TYLCV possesses the potential to induce severe TYLCD by associating with AYVB. PMID:22105924

Ueda, Shigenori; Onuki, Masatoshi; Yamashita, Masataka; Yamato, Yoichi

2012-04-01

31

Recent evolution of a novel begomovirus causing tomato leaf curl disease in the Al-Batinah region of Oman.  

PubMed

For last two decades, begomoviruses (family Geminiviridae) have been a major constraint for tomato production in Oman, particularly in the Al-Batinah region, the major agricultural area of Oman. Farms in the Al-Batinah region were surveyed during January-March and November-December in 2012 and January-February in 2013. Leaf samples of tomato plants showing typical leaf curl disease symptoms were collected and analyzed for begomoviruses. Out of fifteen begomovirus clones sequenced, seven were shown to be tomato yellow leaf curl virus strain Oman (TYLCV-OM); three, chili leaf curl virus strain Oman (ChLCV-OM); and one, tomato leaf curl Oman virus (ToLCOMV) - viruses that have previously been shown to occur in Oman. Four sequences were shown to have relatively low percent identity values to known begomoviruses, with the highest (86 %) to isolates of pepper leaf curl Lahore virus, indicating that these should be included in a new species, for which the name "Tomato leaf curl Al Batinah virus" (ToLCABV) is proposed. Although the betasatellite tomato leaf curl betasatellite (ToLCB; 7 full-length sequences isolated) was identified with some isolates of ChLCV-OM, TYLCV-OM and ToLCOMV, it was not identified in association with any of the ToLCABV isolates. Analysis of the sequences of the TYLCV-OM and ToLCOMV isolates characterized here did not show them to differ significantly from previously characterized isolates of these viruses. The three isolates of ChLCV-OM characterized were shown to have a recombination pattern distinct from earlier characterized isolates. ToLCABV was shown to have resulted from recombination between ChLCV-OM and ToLCOMV. A clone of ToLCABV was infectious by Agrobacterium-mediated inoculation to Nicotiana benthamiana and tomato, inducing symptoms typical of those seen in tomato in the field. Additionally, ToLCABV was shown to be able to interact in planta with ToLCB, resulting in a change in symptom phenotype, although the betasatellite did not appear to affect viral DNA levels. PMID:24052149

Khan, Akhtar J; Akhtar, Sohail; Singh, Achuit K; Al-Shehi, Adel A; Al-Matrushi, Abdulrahman M; Ammara, Ume; Briddon, Rob W

2014-03-01

32

REACTIONS OF SOME ALMOND (Prunus dulchis ) VARIETIES TO LEAF CURL DISEASE CAUSED BY Taphrina deformans IN ?ANLIURFA PROVINCE OF TURKEY  

Microsoft Academic Search

Leaf curl disease, caused by Taphrina deformans (Berk.) Tul., was screened on almond trees located in arid district of Turkey. Different degrees of infection was displayed by nine almond varieties at orchard stands in ?anliurfa province. Assessments were made on upper five leaves of four reverse shoots per tree and ten trees were monitored for each variety during two years.

Hamit KAVAK

33

Within-Host Dynamics of the Emergence of Tomato Yellow Leaf Curl Virus Recombinants  

PubMed Central

Tomato yellow leaf curl virus (TYLCV) is a highly damaging begomovirus native to the Middle East. TYLCV has recently spread worldwide, recombining with other begomoviruses. Recent analysis of mixed infections between TYLCV and Tomato leaf curl Comoros begomovirus (ToLCKMV) has shown that, although natural selection preserves certain co-evolved intra-genomic interactions, numerous and diverse recombinants are produced at 120 days post-inoculation (dpi), and recombinant populations from different tomato plants are very divergent. Here, we investigate the population dynamics that lead to such patterns in tomato plants co-infected with TYLCV and ToLCKMV either by agro-inoculation or using the natural whitefly vector Bemisia tabaci. We monitored the frequency of parental and recombinant genotypes independently in 35 plants between 18 and 330 dpi and identified 177 recombinants isolated at different times. Recombinants were detected from 18 dpi and their frequency increased over time to reach about 50% at 150 dpi regardless of the inoculation method. The distribution of breakpoints detected on 96 fully sequenced recombinants was consistent with a continuous generation of new recombinants as well as random and deterministic effects in their maintenance. A severe population bottleneck of around 10 genomes was estimated during early systemic infection–a phenomenon that could account partially for the heterogeneity in recombinant patterns observed among plants. The detection of the same recombinant genome in six of the thirteen plants analysed beyond 30 dpi supported the influence of selection on observed recombination patterns. Moreover, a highly virulent recombinant genotype dominating virus populations within one plant has, apparently, the potential to be maintained in the natural population according to its infectivity, within-host accumulation, and transmission efficiency - all of which were similar or intermediate to those of the parent genotypes. Our results anticipate the outcomes of natural encounters between TYLCV and ToLCKMV. PMID:23472190

Urbino, Cica; Gutierrez, Serafin; Antolik, Anna; Bouazza, Nabila; Doumayrou, Juliette; Granier, Martine; Martin, Darren P.; Peterschmitt, Michel

2013-01-01

34

Within-host dynamics of the emergence of Tomato yellow leaf curl virus recombinants.  

PubMed

Tomato yellow leaf curl virus (TYLCV) is a highly damaging begomovirus native to the Middle East. TYLCV has recently spread worldwide, recombining with other begomoviruses. Recent analysis of mixed infections between TYLCV and Tomato leaf curl Comoros begomovirus (ToLCKMV) has shown that, although natural selection preserves certain co-evolved intra-genomic interactions, numerous and diverse recombinants are produced at 120 days post-inoculation (dpi), and recombinant populations from different tomato plants are very divergent. Here, we investigate the population dynamics that lead to such patterns in tomato plants co-infected with TYLCV and ToLCKMV either by agro-inoculation or using the natural whitefly vector Bemisia tabaci. We monitored the frequency of parental and recombinant genotypes independently in 35 plants between 18 and 330 dpi and identified 177 recombinants isolated at different times. Recombinants were detected from 18 dpi and their frequency increased over time to reach about 50% at 150 dpi regardless of the inoculation method. The distribution of breakpoints detected on 96 fully sequenced recombinants was consistent with a continuous generation of new recombinants as well as random and deterministic effects in their maintenance. A severe population bottleneck of around 10 genomes was estimated during early systemic infection-a phenomenon that could account partially for the heterogeneity in recombinant patterns observed among plants. The detection of the same recombinant genome in six of the thirteen plants analysed beyond 30 dpi supported the influence of selection on observed recombination patterns. Moreover, a highly virulent recombinant genotype dominating virus populations within one plant has, apparently, the potential to be maintained in the natural population according to its infectivity, within-host accumulation, and transmission efficiency - all of which were similar or intermediate to those of the parent genotypes. Our results anticipate the outcomes of natural encounters between TYLCV and ToLCKMV. PMID:23472190

Urbino, Cica; Gutiérrez, Serafin; Antolik, Anna; Bouazza, Nabila; Doumayrou, Juliette; Granier, Martine; Martin, Darren P; Peterschmitt, Michel

2013-01-01

35

Phylogenetic analysis and homologies of the replicase of tomato leaf curl geminiviruses: implications for obtaining pathogen derived resistance.  

PubMed

Geminiviruses encode a replication initiator protein, Rep, which binds to iterated DNA motifs functioning as essential elements for virus specific replication. Rep protein gene of three isolates of whitefly transmitted geminivirus causing leaf curl disease of tomato in India were amplified, cloned and sequenced. Nucleotide sequence and the derived amino acid sequence for the replicase gene of these isolates was determined and included in an analysis with the published sequences. Phylogenetic relationship clearly indicates two subsets, one belonging to Tomato leaf curl virus (ToLCV) having bipartite genome and the other having the monopartite genome. Comparisons of various functional domains and motifs involved in specificity determinants, DNA-binding and catalysis were discussed. The implications of the sequence analysis were discussed with respect to the strategy for the generation of engineered resistance having wide spectrum applications. PMID:14976419

Praveen, Shelly; Dasgupta, Arupratan; Varma, Anupam

2004-03-01

36

Molecular analysis of new isolates of Tomato leaf curl Philippines virus and an associated betasatellite occurring in the Philippines  

Microsoft Academic Search

Three new begomovirus isolates and one betasatellite were obtained from a tomato plant exhibiting leaf curl symptom in Laguna,\\u000a the Philippines. Typical begomovirus DNA components representing the three isolates (PH01, PH02 and PH03) were cloned, and\\u000a their full-length sequences were determined to be 2754 to 2746 nucleotides. The genome organizations of these isolates were\\u000a similar to those of other Old

Pradeep Sharma; N. Matsuda; N. B. Bajet; M. Ikegami

2011-01-01

37

Four DNA-A variants among Pakistani isolates of cotton leaf curl virus and their affinities to DNA-A of geminivirus isolates from okra  

Microsoft Academic Search

Complete DNA-A sequences of nine Pakistani geminivirus isolates from leaf curl-affected cotton (CLCuV-PK) or from okra, and the partial sequences of several additional isolates were determined. Sequences of isolates from cotton were of four types. Isolates from leaf curl-affected okra had virtually the same sequences as those from cotton. Isolates from yellow vein mosaic-affected okra were of two types (OYVMV

Xueping Zhou; Yule Liu; David J. Robinson; Bryan D. Harrison

38

Mixed infection by two West African tomato-infecting begomoviruses and ageratum leaf curl Cameroon betasatellite in tomato in Cameroon.  

PubMed

Begomovirus isolates ToF3B2 and ToF3B17 and betasatellite isolate SatBToF3 were obtained from the same infected tomato plant showing begomovirus disease symptoms in Fontem, Cameroon. The full-length nucleotide sequences of ToF3B2, ToF3B17 and SatBToF3 were cloned and sequenced and were determined to be 2,797 nt, 2,794 and 1,373 nt long respectively. When compared with other begomovirus and betasatellite sequences, ToF3B2 was 93.5 % identical to Tomato leaf curl Togo virus, ToF3B17 was 95 % identical to Tomato leaf curl Cameroon virus and SatBToF3 was 92 % identical to Ageratum leaf curl Cameroon betasatellite (ALCCMB), respectively. The identification of ALCCMB in Ageratum and now in tomato strongly suggests Ageratum may be an alternative host to these viruses and that ALCCMB is non host specific and may cause severe diseases when transmitted to other crops. PMID:25008895

Leke, Walter N; Kvarnheden, Anders

2014-11-01

39

An efficient in vitro-inoculation method for Tomato yellow leaf curl virus  

PubMed Central

Background Tomato yellow leaf curl virus (TYLCV) is a member of the family Geminiviridae, genus Begomovirus. To test the infectivity of TYLCV in tomato plants, an improved protocol for inoculation of in vitro-cultured tomato plants was developed. Results A TYLCV isolate was cloned, sequenced and used to construct a 1.8-mer infectious clone. Three weeks old microshoots of TYLCV-susceptible tomato plants were inoculated with Agrobacterium tumefaciens harboring the infectious clone for the TYLCV isolate. After two weeks, the TYLCV symptoms started to appear on the in vitro-inoculated plants and the symptoms became more severe and pronounced eight weeks post-inoculation. The method was used efficiently to uncover the resistance mechanism against TYLCV in Solanum habrochaites accession LA 1777, a wild tomato known for its high resistance to whitefly and TYLCV. Conclusions The reported in vitro-inoculation method can be used to screen tomato genotypes for their responses to TYLCV under controlled conditions and it will be a useful tool for better understanding of the TYLCV biology in tomato plants. PMID:20429892

2010-01-01

40

Genome Sequencing of the Plant Pathogen Taphrina deformans, the Causal Agent of Peach Leaf Curl  

PubMed Central

ABSTRACT Taphrina deformans is a fungus responsible for peach leaf curl, an important plant disease. It is phylogenetically assigned to the Taphrinomycotina subphylum, which includes the fission yeast and the mammalian pathogens of the genus Pneumocystis. We describe here the genome of T. deformans in the light of its dual plant-saprophytic/plant-parasitic lifestyle. The 13.3-Mb genome contains few identifiable repeated elements (ca. 1.5%) and a relatively high GC content (49.5%). A total of 5,735 protein-coding genes were identified, among which 83% share similarities with other fungi. Adaptation to the plant host seems reflected in the genome, since the genome carries genes involved in plant cell wall degradation (e.g., cellulases and cutinases), secondary metabolism, the hallmark glyoxylate cycle, detoxification, and sterol biosynthesis, as well as genes involved in the biosynthesis of plant hormones. Genes involved in lipid metabolism may play a role in its virulence. Several locus candidates for putative MAT cassettes and sex-related genes akin to those of Schizosaccharomyces pombe were identified. A mating-type-switching mechanism similar to that found in ascomycetous yeasts could be in effect. Taken together, the findings are consistent with the alternate saprophytic and parasitic-pathogenic lifestyles of T. deformans. PMID:23631913

Cisse, Ousmane H.; Almeida, Joao M. G. C. F.; Fonseca, Alvaro; Kumar, Ajay Anand; Salojarvi, Jarkko; Overmyer, Kirk; Hauser, Philippe M.; Pagni, Marco

2013-01-01

41

Bemisia tabaci Q carrying tomato yellow leaf curl virus strongly suppresses host plant defenses.  

PubMed

The concurrence of tomato yellow leaf curl virus (TYLCV) with the spread of its vector Bemisia tabaci Q rather than B in China suggests a more mutualistic relationship between TYLCV and Q. Here, we investigated the hypothesis that viruliferous B and Q have different effects on plant defenses. We found the fecundity of nonviruliferous B, nonviruliferous Q, viruliferous Q and viruliferous B was 11.080, 12.060, 10.760, and 11.220 respectively on plants previously attacked by the other biotype, however, on their respective noninfested control leaves fecundity was 12.000, 10.880, 9.760, and 8.020 respectively. Only viruliferous B had higher fecundity on viruliferous Q-infested plants than on control plants. The longevity of viruliferous B showed the same phenomenon. At 1 d infestion, the jasmonic acid content in leaves noninfested and in leaves infested with nonviruliferous B, nonviruliferous Q, viruliferous B and viruliferous Q was 407.000, 281.333, 301.333, 266.667 and 134.000?ng/g FW, respectively. The JA content was lowest in viruliferous Q-infested leaves. The proteinase inhibitor activity and expression of JA-related upstream gene LOX and downstream gene PI II showed the same trend. The substantial suppression of host defenses by Q carrying TYLCV probably enhances the spread of Q and TYLCV in China. PMID:24912756

Shi, Xiaobin; Pan, Huipeng; Zhang, Hongyi; Jiao, Xiaoguo; Xie, Wen; Wu, Qingjun; Wang, Shaoli; Fang, Yong; Chen, Gong; Zhou, Xuguo; Zhang, Youjun

2014-01-01

42

Genetic Structure and Population Variability of Tomato Yellow Leaf Curl China Virus?  

PubMed Central

Geminiviruses have circular single-stranded DNA genomes and are important pathogens in tropical and subtropical regions, but their population diversity and variability are poorly understood. Here, we have investigated variations accumulating in Tomato yellow leaf curl China virus (TYLCCNV), a geminivirus in the genus Begomovirus of the family Geminiviridae. The population variation was analyzed in a naturally infected tomato (Solanum lycopersicom) plant and in Nicotiana benthamiana and tomato plants experimentally infected with a swarm of TYLCCNV DNA clones to provide an identical sequence for initiation of infection. Our results demonstrate that the population of TYLCCNV in a naturally infected tomato plant was genetically heterogeneous and that rapid mutation occurred in the populations amplified from N. benthamiana and tomato plants that had been infected with cloned DNA. This feature of the population of TYLCCNV in these plants consisted of the consensus sequence and a pool of mutants that are not identical but are closely related to the consensus sequence, and it coincides with the quasispecies concept described for many RNA viruses. The mutation frequency was circa 10?4 in N. benthamiana and tomato at 60 days postinoculation, a value comparable to that reported for plant RNA viruses. The quasispecies-like nature of the TYLCCNV populations suggested that TYLCCNV is capable of rapid evolution and adaptation in response to changing agricultural practices. PMID:17376922

Ge, Linmei; Zhang, Jiangtao; Zhou, Xueping; Li, Hongye

2007-01-01

43

Tomato yellow leaf curl virus alters the host preferences of its vector Bemisia tabaci.  

PubMed

Bemisia tabaci, the whitefly vector of Tomato yellow leaf curl virus (TYLCV), seriously reduces tomato production and quality. Here, we report the first evidence that infection by TYLCV alters the host preferences of invasive B. tabaci B (Middle East-Minor Asia 1) and Q (Mediterranean genetic group), in which TYLCV-free B. tabaci Q preferred to settle on TYLCV-infected tomato plants over healthy ones. TYLCV-free B. tabaci B, however, preferred healthy tomato plants to TYLCV-infected plants. In contrast, TYLCV-infected B. tabaci, either B or Q, did not exhibit a preference between TYLCV-infected and TYLCV-free tomato plants. Based on gas chromatography-mass spectrometry (GCMS)analysis of plant terpene volatiles, significantly more ?-myrcene, thymene, ?-phellandrene, caryophyllene, (+)-4-carene, and ?-humulene were released from the TYLCV-free tomato plants than from the TYLCV-infected ones. The results indicate TYLCV can alter the host preferences of its vector Bemisia tabaci B and Q. PMID:24096821

Fang, Yong; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Shi, Xiaobin; Chen, Gong; Su, Qi; Yang, Xin; Pan, Huipeng; Zhang, Youjun

2013-01-01

44

Properties of a virus causing mosaic and leaf curl disease of Celosia argentea L. in Nigeria.  

PubMed

A sap transmissible virus, causing mosaic and leaf curl disease of Celosia argentea, was isolated at vegetable farms in Amuwo Odofin, Tejuoso, and Abule Ado, Lagos, Nigeria. The virus had a restricted host range confined to a few species of the Amaranthaceae, Chenopodiaceae and Solanaceae families. It failed to infect several other species of the Aizoaceae, Brassicaceae, Cucurbitaceae, Fabaceae, Lamiaceae, Malvaceae, Poaceae and Tiliaceae families. The virus was transmitted in a non-persistent manner by Aphis spiraecola and Toxoptera citricidus but not by eight other aphid species tested. There was no evidence of transmission by seeds of C. argentae varieties. The viral coat protein had a relative molecular mass (M(r)) of about 30.2 K. Electron microscopy of purified virus preparations revealed flexuous rod shaped particles of about 750 nm in length. Serological studies were performed using the enzyme-linked immunosorbent assay (ELISA), immunosorbent electron microscopy (ISEM) and Western blot analysis. The virus reacted positively with an universal potyvirus group monoclonal antibody (MoAb) and MoAb P-3-3H8 raised against peanut stripe potyvirus. It also reacted with polyclonal antibodies raised against several potyviruses including asparagus virus-1 (AV-1), turnip mosaic virus (TuMV), maize dwarf mosaic virus (MDMV), watermelon mosaic virus (WMV-2), plum pox virus (PPV), soybean mosaic virus (SoyMV), lettuce mosaic virus (LMV), bean common mosaic virus (BCMV) and beet mosaic virus (BMV) in at least one of the serological assays used. On the basis of host range, mode of transmission, and available literature data, the celosia virus seems to be different from potyviruses previously reported to infect vegetables in Nigeria. The name celosia mosaic virus (CIMV) has been proposed for this virus. PMID:9842442

Owolabi, T A; Taiwo, M A; Thottappilly, G A; Shoyinka, S A; Proll, E; Rabenstein, F

1998-06-01

45

Highly sensitive serological methods for detecting tomato yellow leaf curl virus in tomato plants and whiteflies  

PubMed Central

Background Tomato yellow leaf curl virus (TYLCV) is a member of the genus Begomovirus in the family Geminiviridae, which causes severe losses in tomato production in tropic and subtropic regions. Methods The purified TYLCV virions were used as the immunogen to produce monoclonal antibodies (MAbs) using the hybridoma technology. MAb-based dot enzyme-linked immunosorbent assay (dot-ELISA) and direct tissue blot immunoassay (DTBIA) were developed for sensitive, simple, and rapid detection of TYLCV in field tomato and whitefly (Bemisia tabaci) samples collected from TYLCV prevalent provinces in China. Results Using the hybridoma technology, six murine MAbs (1C4, 8D10, 6E3, 2F2, 3F4 and 4G3) against TYLCV were prepared. Using the MAb 1C4, dot-ELISA and DTBIA were then established for detecting TYLCV in field tomato and whitefly samples collected from TYLCV prevalent provinces in China. The dot-ELISA could detect TYLCV in infected tissue crude extract diluted at 1:5,120 (w/v, g mL-1), and in viruliferous whitefly homogenate diluted at 1:128 (individual whitefly/?L), respectively. Field tomato samples (n=487) and whitefly samples (n=110) from TYLCV prevalent districts in China were screened for the presence of TYLCV using the two developed methods, and the results were further confirmed by PCR and nucleotide sequencing. The survey revealed that TYLCV is widespread on tomato plants in Zhejiang, Shandong and Henan provinces in China. Conclusions The developed dot-ELISA is very suitable for the routine detection of TYLCV in field tomato and whitefly samples, and the DTBIA is more suitable for the routine detection of TYLCV in large-scale tomato plant samples collected from TYLCV prevalent areas. PMID:23647724

2013-01-01

46

A novel shaggy-like kinase interacts with the Tomato leaf curl virus pathogenicity determinant C4 protein  

Microsoft Academic Search

Tomato leaf curl virus-Australia (ToLCV) C4 protein has been shown to be associated with virus pathogenesis. Here, we demonstrate that C4 acts as a suppressor\\u000a of gene silencing. To understand the multifunctional role of C4, a novel shaggy-like kinase (SlSK) from tomato, which interacts\\u000a with ToLCV C4 in a yeast two-hybrid assay, was isolated and interaction between these proteins was

Satish C. Dogra; Omid Eini; M. Ali Rezaian; John W. Randles

2009-01-01

47

Severe outbreak of tomato yellow leaf curl Sardinia virus on pepper in southern Italy.  

PubMed

During summer and autumn 2008 a severe outbreak of pepper leaf curl disease (PLCD) was observed in pepper crops under plastic tunnels in the ionic coast of Basilicata region. Its incidence reached, in some cases, values close to 50%. The beginning of infections was recorded along the perimeter of the tunnels, where it reached a percentage of almost 100%. The infection then progressively spread towards the central areas of the greenhouses. Large populations of whiteflies, identificated as Bemisia tabaci, were observed on the infected crops. Detection assays for TYLCSV and TYLCV were performed in order to ascertain the etiologic agent: 190 symptomatic samples were collected from different fields and assayed in DAS-ELISA using a broad-spectrum reagent combination (distributed by Bioreba AG) detecting TYLCV, TYLCSV and other Begamoviruses: of these, 176 samples resulted positive. In order to discriminate between TYLCSV, TYLCV or any other Begamovirus, 15 positive samples were analyzed by PCR using a couple of synthetic oligonucleotides allowing the amplification of the whole coat protein (CP) gene. RFLP analysis performed on the PCR product, 1008 bp long, showed the presence of only TYLCSV in all assayed samples. The molecular characterization performed by phylogenetic analysis of the sequenced coat protein gene revealed that the isolate shares a similarity of about 97% with the corresponding sequence of a tomato TYLCSV isolate from Sicily (Z28390) and is almost identical with the pepper isolate CAB-It recovered in the same area in 2007 (TYLCSV was first recorded on pepper in Italy in 2007 in Policoro-MT, Fanigliulo et al., 2008. Comm. Appl. Biol. Sci, Ghent University, 73/2, 2008), indicating that there is a very low variability in TYLCSV population in the surveyed area. The further diffusion of PLCD and its hazard has to be connected with the presence of wide tomato cultivations, of weed hosts alternative to pepper (Solanum nigrum, Datura stramonium, Sonchus asper, Cardaria draba and Abutilon theophrasti) and with the strong presence of the vector B. tabaci of the B biotype, more efficient than Q biotype in the virus transmission, and able to feed and reproduce on peppers as well as on tomatoes. PMID:20222578

Comes, Soccorsa; Fanigliulo, Angela; Pacella, Rosa; Crescenzi, Aniello

2009-01-01

48

Transmission of Tomato Yellow Leaf Curl Virus by two invasive biotypes and a Chinese indigenous biotype of the whitefly Bemisia tabaci  

Microsoft Academic Search

The global invasion of certain Bemisia tabaci biotypes provides opportunities to compare the competency of virus transmission between invasive and indigenous biotypes. Here we report on the acquisition, retention and transmission of Tomato Yellow Leaf Curl Virus (TYLCV) by the invasive B, Q and indigenous ZHJ2 biotypes of B. tabaci from Zhejiang, China. For all whitefly biotypes, TYLCV DNA was

Meng Li; Jian Hu; Fang-Cheng Xu; Shu-Sheng Liu

2010-01-01

49

Identification of a disease complex involving a novel monopartite begomovirus with beta- and alphasatellites associated with okra leaf curl disease in Oman.  

PubMed

Okra leaf curl disease (OLCD) is an important viral disease of okra in tropical and subtropical areas. The disease is caused by begomovirus-satellite complexes. A begomovirus and associated betasatellite and alphasatellite were identified in symptomatic okra plants from Barka, in the Al-Batinah region of Oman. Analysis of the begomovirus sequences showed them to represent a new begomovirus most closely related to cotton leaf curl Gezira virus (CLCuGeV), a begomovirus of African origin. The sequences showed less than 85 % nucleotide sequence identity to CLCuGeV isolates. The name okra leaf curl Oman virus (OLCOMV) is proposed for the new virus. Further analysis revealed that the OLCOMV is a recombinant begomovirus that evolved by the recombination of CLCuGeV isolates with tomato yellow leaf curl virus-Oman (TYLCV-OM). An alpha- and a betasatellite were also identified from the same plant sample, which were also unique when compared to sequences available in the databases. However, although the betasatellite appeared to be of African origin, the alphasatellite was most closely related to alphasatellites originating from South Asia. This is the first report of a begomovirus-satellite complex infecting okra in Oman. PMID:24287711

Akhtar, Sohail; Khan, Akhtar J; Singh, Achuit S; Briddon, Rob W

2014-05-01

50

Expression of stress gene networks in tomato lines susceptible and resistant to Tomato yellow leaf curl virus in response to abiotic stresses  

Microsoft Academic Search

The defense response to several abiotic stresses has been compared in two tomato inbred lines issued from the same breeding program, one susceptible and the other resistant to Tomato yellow leaf curl virus (TYLCV) infection. The level of oxidative burst and the amounts of key regulatory stress proteins: pathogenesis-related proteins (PRs), heat shock proteins (HSPs) and mitogen-activated protein kinases (MAPKs)

Rena Gorovits; Henryk Czosnek

2008-01-01

51

Molecular cloning of coat protein gene of an Indian cotton leaf curl virus (CLCuV-HS2) isolate and its phylogenetic relationship with others members of Geminiviridae.  

PubMed

Cotton leaf curl geminivirus is a whitefly (Bemisia tabaci Genn.) transmitted Begomovirus (Family Geminiviridae) causing a serious disease of cotton in northern India. The very typical symptoms of present isolate (CLCuV-HS2) showed thickened veins, dark green discoloration of the leaves with upward curling and leaf like structure known as enation (one in number), which develops into cup-shaped on the reverse side of leaves. The polymerase chain reaction (PCR) based technique can detect the viral DNA in samples stored upto 3 days after the collection and have wide application for the field diagnosis. The complete nucleotide sequence of the Indian isolate of cotton leaf curl geminivirus (CLCuV-HS2) coat protein (CP) gene component was determined using CP specific primers through PCR amplification from field infected cotton plants growing in Haryana, India. Comparison of the amino acid sequence of the putative CP with some other mono and bipartite geminiviruses revealed a maximum of 97.3% identity with Pakistan cotton leaf curl virus (CLCuV-62). A nuclear localization signal located close to the N-terminal of CP gene was determined. PMID:15744566

Sharma, Pradeep; Rishi, Narayan; Malathi, V G

2005-01-01

52

Host range and genetic diversity of croton yellow vein mosaic virus, a weed-infecting monopartite begomovirus causing leaf curl disease in tomato.  

PubMed

Croton yellow vein mosaic virus (CYVMV) is a widely occurring begomovirus in Croton bonplandianum, a common weed in the Indian subcontinent. In this study, CYVMV (genus Begomovirus, family Geminiviridae) was transmitted by whiteflies (Bemisia tabaci) to as many as 35 plant species belonging to 11 families, including many vegetables, tobacco varieties, ornamentals and weeds. CYVMV produced bright yellow vein symptoms in croton, whereas in all the other host species, the virus produced leaf curl symptoms. CYVMV produced leaf curl in 13 tobacco species and 22 cultivars of Nicotiana tabacum and resembled tobacco leaf curl virus (TobLCV) in host reactions. However, CYVMV was distinguished from TobLCV in four differential hosts, Ageratum conyzoides, C. bonplandianum, Euphorbia geniculata and Sonchus bracyotis. The complete genome sequences of four isolates originating from northern, eastern and southern India revealed that a single species of DNA-A and a betasatellite, croton yellow vein mosaic betasatellite (CroYVMB) were associated with the yellow vein mosaic disease of croton. The sequence identity among the isolates of CYVMV DNA-A and CroYVMB occurring in diverse plant species was 91.8-97.9 % and 83.3-100 %, respectively. The CYVMV DNA-A and CroYVMB generated through rolling-circle amplification of the cloned DNAs produced typical symptoms of yellow vein mosaic and leaf curling in croton and tomato, respectively. The progeny virus from both the croton and tomato plants was transmitted successfully by B. tabaci. The present study establishes the etiology of yellow vein mosaic disease of C. bonplandianum and provides molecular evidence that a weed-infecting monopartite begomovirus causes leaf curl in tomato. PMID:23096697

Pramesh, D; Mandal, Bikash; Phaneendra, Chigurupati; Muniyappa, V

2013-03-01

53

Three-way interactions between the tomato plant, tomato yellow leaf curl virus, and Bemisia tabaci (Hemiptera: Aleyrodidae) facilitate virus spread.  

PubMed

Plant defense responses can greatly affect plant viruses and their herbivore vectors. The current article reports on plant defense responses involving jasmonic acid (JA), salicylic acid (SA), and proteinase inhibitor (PI) in the three-way interaction between tomato plants, tomato yellow leaf curl virus, and the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). The results showed that feeding by viruliferous B. tabaci increases the longevity and fecundity of nonviruliferous B. tabaci that subsequently feed on the same plant. Feeding by nonviruliferous B. tabaci alone suppressed plant defense responses involving JA and PI but induced responses involving SA. Feeding by viruliferous B. tabaci increased the suppression of plant defenses involving JA and PI but did not increase responses involving SA. These results indicate that the interactive effects of tomato yellow leaf curl virus and B. tabaci on plants increase vector fitness and virus transmission by reducing plant defense. PMID:25026648

Shi, Xiaobin; Pan, Huipeng; Xie, Wen; Jiao, Xiaoguo; Fang, Yong; Chen, Gong; Yang, Xin; Wu, Qingjun; Wang, L Shaoli; Zhang, Youjun

2014-06-01

54

In vitro Cleavage and Joining at the Viral Origin of Replication by the Replication Initiator Protein of Tomato Yellow Leaf Curl Virus  

Microsoft Academic Search

Replication of the single-stranded DNA genome of geminiviruses occurs via a double-stranded intermediate that is subsequently used as a template for rolling-circle replication of the viral strand. Only one of the proteins encoded by the virus, here referred to as replication initiator protein (Rep protein), is indispensable for replication. We show that the Rep protein of tomato yellow leaf curl

Jurgen Laufs; Wolfgang Traut; Francoise Heyraud; Volker Matzeit; Stephen G. Rogers; Jeff Schell; Bruno Gronenborn

1995-01-01

55

Association of an alphasatellite with tomato yellow leaf curl virus and ageratum yellow vein virus in Japan is suggestive of a recent introduction.  

PubMed

Samples were collected in 2011 from tomato plants exhibiting typical tomato leaf curl disease symptoms in the vicinity of Komae, Japan. PCR mediated amplification, cloning and sequencing of all begomovirus components from two plants from different fields showed the plants to be infected by Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein virus (AYVV). Both viruses have previously been shown to be present in Japan, although this is the first identification of AYVV on mainland Japan; the virus previously having been shown to be present on the Okinawa Islands. The plant harboring AYVV was also shown to contain the betasatellite Tomato leaf curl Java betasatellite (ToLCJaB), a satellite not previously shown to be present in Japan. No betasatellite was associated with the TYLCV infected tomato plants analyzed here, consistent with earlier findings for this virus in Japan. Surprisingly both plants were also found to harbor an alphasatellite; no alphasatellites having previously been reported from Japan. The alphasatellite associated with both viruses was shown to be Sida yellow vein China alphasatellite which has previously only been identified in the Yunnan Province of China and Nepal. The results suggest that further begomoviruses, and their associated satellites, are being introduced to Japan. The significance of these findings is discussed. PMID:24424499

Shahid, Muhammad Shafiq; Ikegami, Masato; Waheed, Abdul; Briddon, Rob W; Natsuaki, Keiko T

2014-01-01

56

Association of an Alphasatellite with Tomato Yellow Leaf Curl Virus and Ageratum Yellow Vein Virus in Japan is Suggestive of a Recent Introduction  

PubMed Central

Samples were collected in 2011 from tomato plants exhibiting typical tomato leaf curl disease symptoms in the vicinity of Komae, Japan. PCR mediated amplification, cloning and sequencing of all begomovirus components from two plants from different fields showed the plants to be infected by Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein virus (AYVV). Both viruses have previously been shown to be present in Japan, although this is the first identification of AYVV on mainland Japan; the virus previously having been shown to be present on the Okinawa Islands. The plant harboring AYVV was also shown to contain the betasatellite Tomato leaf curl Java betasatellite (ToLCJaB), a satellite not previously shown to be present in Japan. No betasatellite was associated with the TYLCV infected tomato plants analyzed here, consistent with earlier findings for this virus in Japan. Surprisingly both plants were also found to harbor an alphasatellite; no alphasatellites having previously been reported from Japan. The alphasatellite associated with both viruses was shown to be Sida yellow vein China alphasatellite which has previously only been identified in the Yunnan Province of China and Nepal. The results suggest that further begomoviruses, and their associated satellites, are being introduced to Japan. The significance of these findings is discussed. PMID:24424499

Shahid, Muhammad Shafiq; Ikegami, Masato; Waheed, Abdul; Briddon, Rob W.; Natsuaki, Keiko T.

2014-01-01

57

A Rapid and Efficient Method for Construction of an Infectious Clone of Tomato yellow leaf curl virus  

PubMed Central

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus, is responsible for one of the most devastating viral diseases in tomato-growing countries and is becoming a serious problem in many subtropical and tropical countries. The climate in Korea is getting warmer and developing subtropical features in response to global warming. These changes are being accompanied by TYLCV, which is now becoming a large problem in the Korean tomato industry. The most effective way to reduce damage caused by TYLCV is to breed resistant varieties of tomatoes. To accomplish this, it is necessary to establish a simple inoculation technique for the efficient evaluation of resistance to TYLCV. Here, we present the rolling circle amplification (RCA) method, which employs a bacteriophage using phi-29 DNA polymerase for construction of infectious TYLCV clones. The RCA method is simple, does not require sequence information for cloning, and is less expensive and time consuming than conventional PCR based-methods. Furthermore, RCA-based construction of an infectious clone can be very useful to other emerging and unknown geminiviruses in Korea. PMID:25289018

Bang, Bongjun; Lee, Jongyun; Kim, Sunyoung; Park, Jungwook; Nguyen, Thao Thi; Seo, Young-Su

2014-01-01

58

New Insecticides for Management of Tomato Yellow Leaf Curl, a Virus Vectored by the Silverleaf Whitefly, Bemisia tabaci.  

PubMed

Greenhouse studies using a randomized complete block design were carried out to evaluate the effect of six insecticides on transmission of Tomato yellow leaf curl virus (TYLCV) by the silverleaf whitefly, Bemisia tabaci biotype B Gennadius (Hemiptera: Aleyrodidae) to tomato, Lycopersicon esculentum (Miller) (Solanales: Solanaceae), seedlings that were inoculated with whiteflies from a TYLCV colony in cages 3, 7, or 14?d after treatment with insecticide. The purpose was to reveal differences in residual efficacy of four materials that are nearing registration for use on tomato-cyazypyr, flupyradifurone, pyrafluquinazon, and sulfoxaflor-and to compare them with two established insecticides, pymetrozine and a zeta-cypermethrin/bifenthrin combination. Differences in efficacy were expected because these six materials represent five distinct modes of action and both contact and systemic materials. Percentage of tomato seedlings expressing virus symptoms tended to be lowest in seedlings treated with flupyradifurone. The zeta-cypermethrin/bifenthrin insecticide demonstrated comparable efficacy to flupyradifurone in some trials at 3 and 7?d after treatment inoculations, but not the 14?d after treatment inoculation. Pyrafluquinazon was not statistically different from cyazypyr or sulfoxaflor in percentage of plants with virus symptoms in any trial. Percentage virus in the cyazypyr and sulfoxaflor treatments was not statistically different in the 3 and 7?d after treatment inoculations. Among seedlings treated with insecticide, percentage with virus symptoms tended to be highest in the seedlings treated with pymetrozine. PMID:25368089

Smith, H A; Giurcanu, M C

2014-01-01

59

Molecular variability and evolution of a natural population of tomato yellow leaf curl virus in Shanghai, China.  

PubMed

Tomato yellow leaf curl virus (TYLCV), belonging to the genus Begomovirus of the family Geminiviridae, is emerging as the most destructive pathogen of tomato plants. Since the first report of TYLCV in Shanghai, China in 2006, TYLCV has spread rapidly to 13 provinces or autonomous regions of China. In this study, the molecular variability and evolution of TYLCV were monitored in Shanghai from its first upsurge in 2006 until 2010. Full-length genomic sequences of 26 isolates were obtained by rolling circle amplification. Sequence analysis showed that the intergenic region was the most variable, with a mean mutation rate of 4.81×10(-3) nucleotide substitutions per site per year. Genetic differentiation was found within isolates obtained from 2006, 2009, and 2010, though a linear increase in genetic diversity over time was not evident. Whilst significant parts of TYLCV genes were under negative selection, the C4 gene embedded entirely within the C1 gene had a tendency to undergo positive selection. Our results indicate that a mechanism of independent evolution of overlapping regions could apply to the natural population of TYLCV in Shanghai, China. PMID:24510706

Yang, Xiu-ling; Zhou, Meng-ning; Qian, Ya-juan; Xie, Yan; Zhou, Xue-ping

2014-02-01

60

High Genetic Stability of the Begomovirus Tomato yellow leaf curl Sardinia virus in Southern Spain Over an 8-Year Period.  

PubMed

ABSTRACT The evolution of the plant single-stranded DNA virus Tomato yellow leaf curl Sardinia virus (TYLCSV) (genus Begomovirus, family Geminiviridae) has been monitored for 8 years after its appearance in southern Spain. Variation within three genomic regions of 166 TYLCSV isolates collected from three locations was assessed by single-strand conformation polymorphism (SSCP) analysis. According to SSCP, the intergenic region (IR) was the most variable. Low genetic diversity was found within the population and geographical or temporal differences were not evident. Nucleotide sequences of specific genomic regions of haplotypes identified by SSCP indicated close relationships among them. Therefore, the Spanish TYLCSV population appears to represent a single, undifferentiated population. The analysis of IR sequences for a subsample of 76 randomly chosen isolates confirmed the limited genetic diversity revealed by the SSCP analysis. A tendency to a lineal increase in diversity over time was observed in Málaga and Almería subpopulations; however, no accumulation of mutations in single isolates was evident. Negative selection to variation seems to operate to conserve certain regions of the genome. Thus, the low genetic diversity found in the studied TYLCSV population might be the result of a founder effect with subsequent selection against less fit variants arising by mutation. PMID:18942962

Sánchez-Campos, S; Díaz, J A; Monci, F; Bejarano, E R; Reina, J; Navas-Castillo, J; Aranda, M A; Moriones, E

2002-08-01

61

Correlation of meteorological parameters and remotely sensed normalized difference vegetation index (NDVI) with cotton leaf curl virus (CLCV) in Multan  

NASA Astrophysics Data System (ADS)

Climate change and weather has a profound effect on the spread of Cotton Leaf Curl Virus (CLCV) which is transmitted by whitefly. Climate change is altering temperature and precipitation patterns, resulting in the shift of some insect/pest from small population to large population thus effecting crops yield. To find out the relationship between the weather conditions, outburst of CLCV and changes in Normalized Difference Vegetation Index (NDVI) values due to the outburst of CLCV, a study was carried out for tehsil Multan. Data was acquired for the months of June, July, August and September for the year 2010. Regression analysis between CLCV and meteorological conditions as well as between CLCV and NDVI was performed. Meteorological parameters included temperature, humidity, precipitation, cloud cover, wind direction, pan evaporation and sunshine hours. NDVI values were calculated from SPOT satellite imagery (1km) using ArcMap10 and WinDisp v5.1. Correlation coefficients obtained in most of the cases were acceptable however the significance F and P-value were higher than their critical value at 95% level of significance. Therefore significant correlation was found only between CLCV and temperature and between CLCV and PAN evaporation during the month of July.

Ahmed, A.; Akhtar, A.; Khalid, B.; Shamim, A.

2013-06-01

62

Functional Characterization of a Bidirectional Plant Promoter from Cotton Leaf Curl Burewala Virus Using an Agrobacterium-Mediated Transient Assay  

PubMed Central

The C1 promoter expressing the AC1 gene, and V1 promoter expressing the AV1 gene are located in opposite orientations in the large intergenic region of the Cotton leaf curl Burewala virus (CLCuBuV) genome. Agro-infiltration was used to transiently express putative promoter constructs in Nicotiana tabacum and Gossypium hirsutum leaves, which was monitored by a GUS reporter gene, and revealed that the bidirectional promoter of CLCuBuV transcriptionally regulates both the AC1 and AV1 genes. The CLCuBuV C1 gene promoter showed a strong, consistent transient expression of the reporter gene (GUS) in N. tabacum and G. hirsutum leaves and exhibited GUS activity two- to three-fold higher than the CaMV 35S promoter. The CLCuBuV bidirectional genepromoter is a nearly constitutive promoter that contains basic conserved elements. Many cis-regulatory elements (CREs) were also analyzed within the bidirectional plant promoters of CLCuBuV and closely related geminiviruses, which may be helpful in understanding the transcriptional regulation of both the virus and host plant. PMID:24424501

Ashraf, Muhammad Aleem; Shahid, Ahmad Ali; Rao, Abdul Qayyum; Bajwa, Kamran Shehzad; Husnain, Tayyab

2014-01-01

63

A Rapid and Efficient Method for Construction of an Infectious Clone of Tomato yellow leaf curl virus.  

PubMed

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus, is responsible for one of the most devastating viral diseases in tomato-growing countries and is becoming a serious problem in many subtropical and tropical countries. The climate in Korea is getting warmer and developing subtropical features in response to global warming. These changes are being accompanied by TYLCV, which is now becoming a large problem in the Korean tomato industry. The most effective way to reduce damage caused by TYLCV is to breed resistant varieties of tomatoes. To accomplish this, it is necessary to establish a simple inoculation technique for the efficient evaluation of resistance to TYLCV. Here, we present the rolling circle amplification (RCA) method, which employs a bacteriophage using phi-29 DNA polymerase for construction of infectious TYLCV clones. The RCA method is simple, does not require sequence information for cloning, and is less expensive and time consuming than conventional PCR based-methods. Furthermore, RCA-based construction of an infectious clone can be very useful to other emerging and unknown geminiviruses in Korea. PMID:25289018

Bang, Bongjun; Lee, Jongyun; Kim, Sunyoung; Park, Jungwook; Nguyen, Thao Thi; Seo, Young-Su

2014-09-01

64

[The C4 proteins of Ageratum yellow vein China virus and Stachytarpheta leaf curl virus are suppressors of RNA silencing].  

PubMed

RNA silencing is a highly conserved mechanism in many eukaryotic organisms that involves sequence-specific RNA degradation. One of the important roles of RNA silencing is antiviral infection. To counter this defense mechanism, many plant viruses have evolved or acquired functional proteins (suppressors) for suppression of RNA silencing. Geminiviruses are a family of small circular single-stranded DNA (ssDNA) viruses that cause severe diseases in major crop plants worldwide. AC2 (C2) and AC4 (C4) proteins of many geminiviruses were reported to be suppressors of RNA silencing. Ageratum yellow vein China virus (AYVCNV) and Stachytarpheta leaf curl virus are two distinct geminiviruses identified in China. In this study, the functions of C4 of AYVCNV and StaLCV were studied, analysis of infectivity of AYVCNV and StaLCV C4 genes using Tobacco rattle virus (TRV) vector were carried out in Nicotiana benthamiana plants, N. benthamiana plants expressing C4 can induce the virus-like symptoms, indicating that the C4 gene of AYVCNV or StaLCV is symptom determinant. In experiment of suppression of RNA silencing, C4 protein of AYVCNV or StaLCV can suppresses the local silencing of gfp in transgenic N. benthamiana plants (16c), suggests that both of them are suppressors of RNA silencing. The above results indicate that C4 of PMID:17436621

Xiong, Qing; Zhou, Xue-Ping

2007-02-01

65

Two new natural begomovirus recombinants associated with the tomato yellow leaf curl disease co-exist with parental viruses in tomato epidemics in Italy.  

PubMed

Two tomato geminivirus species co-exist in protected crops in Sicily, Tomato yellow leaf curl Sardinia virus (TYLCSV, found in 1989) and Tomato yellow leaf curl virus (TYLCV, found in 2002), and mixed infections have been detected. In a field survey conducted in 2004, the viral intergenic region (IR) was amplified from infected plants, and molecules apparently hybrid between the two species were found, but only in plants where one or both parental species were also present. Two of these hybrids, named 2/2 and 2/5, were isolated and infectious clones were obtained. They were both readily whitefly-transmitted to tomato plants; clone 2/5 produced symptoms typical of TYLCSV and TYLCV, while clone 2/2 produced more severe symptoms, with leaves showing downward curling and rugosity. Sequence analysis showed that both 2/2 and 2/5 are newly generated hybrids, with two recombination sites each. One site, common to both hybrids, is in the stem-loop of the IR. The other is close to the 3'-end of the CP ORF in 2/5 and within the Rep ORF in 2/2. Thus, the 2/2 hybrid virus has a hybrid Rep protein, with the 202 amino-terminal aa from TYLCV and the remaining 155 aa from TYLCSV. Replication assays in leaf disc indicated a lower replicative capacity with respect to parental viruses, a fact that might help to explain why plants infected only by a recombinant have not been found so far. PMID:19463717

Davino, Salvatore; Napoli, Chiara; Dellacroce, Chiara; Miozzi, Laura; Noris, Emanuela; Davino, Mario; Accotto, Gian Paolo

2009-07-01

66

Implication of the Bacterial Endosymbiont Rickettsia spp. in Interactions of the Whitefly Bemisia tabaci with Tomato yellow leaf curl virus  

PubMed Central

ABSTRACT Numerous animal and plant viruses are transmitted by arthropod vectors in a persistent, circulative manner. Tomato yellow leaf curl virus (TYLCV) is transmitted by the sweet potato whitefly Bemisia tabaci. We report here that infection with Rickettsia spp., a facultative endosymbiont of whiteflies, altered TYLCV-B. tabaci interactions. A B. tabaci strain infected with Rickettsia acquired more TYLCV from infected plants, retained the virus longer, and exhibited nearly double the transmission efficiency compared to an uninfected B. tabaci strain with the same genetic background. Temporal and spatial antagonistic relationships were discovered between Rickettsia and TYLCV within the whitefly. In different time course experiments, the levels of virus and Rickettsia within the insect were inversely correlated. Fluorescence in situ hybridization analysis of Rickettsia-infected midguts provided evidence for niche exclusion between Rickettsia and TYLCV. In particular, high levels of the bacterium in the midgut resulted in higher virus concentrations in the filter chamber, a favored site for virus translocation along the transmission pathway, whereas low levels of Rickettsia in the midgut resulted in an even distribution of the virus. Taken together, these results indicate that Rickettsia, by infecting the midgut, increases TYLCV transmission efficacy, adding further insights into the complex association between persistent plant viruses, their insect vectors, and microorganism tenants that reside within these insects. IMPORTANCE Interest in bacterial endosymbionts in arthropods and many aspects of their host biology in agricultural and human health systems has been increasing. A recent and relevant studied example is the influence of Wolbachia on dengue virus transmission by mosquitoes. In parallel with our recently studied whitefly-Rickettsia-TYLCV system, other studies have shown that dengue virus levels in the mosquito vector are inversely correlated with bacterial load. Our work here presents evidence of unifying principles between vectors of plant and animal viruses in a role for endosymbionts in manipulating vector biology and pathogen transmission. Our results demonstrate the influence of an interesting and prominent bacterial endosymbiont in Bemisia tabaci in TYLCV transmission, a worldwide disease infecting tomatoes. Besides its agricultural importance, this system provides interesting insights into Bemisia interaction with these newly discovered endosymbionts. PMID:24600010

Kliot, Adi; Cilia, Michelle; Czosnek, Henryk

2014-01-01

67

Molecular detection and partial characterization of a begomovirus causing leaf curl disease of potato in sub-Himalayan West Bengal, India.  

PubMed

The characteristic disease symptoms of apical leaf curl, crinkled leaves and conspicuous mosaic were observed in potato plants grown in areas of Coochbehar, one of the distinct agroclimatic zones of sub-Himalayan West Bengal. Whitefly (Bemisia tabaci) population was also observed in and around the infected plants. The characteristic disease symptoms and presence of whitefly (Bemisia tabaci) population indicated the possibility of begomovirus infection. Total DNA was extracted from infected samples and PCR was carried out using begomovirus specific primers. PCR product of 1539 nucleotide long containing pre-coat protein, coat protein, AC5, AC3, AC2 and partial AC1 gene of DNA-Asegment and 1001 nucleotide long DNA-B containing BV1 and BC1 genes were submitted to the GenBank (accession numbers HQ597033 for DNA-A and JN390432 for DNA-B). The amplified DNA-A and DNA-B segment showed highest 98% and 99% nucleotide sequence similarity respectively with Tomato leaf curl New Delhi virus (ToLCNDV). In phylogenetic analysis also the virus sequence clustered with ToLCNDV isolates. The disease was successfully transmitted to healthy tomato plants using both whitefly vector, B. tabaci and mechanical sap inoculation using sap of infected potato leaves. It is the first record of begomovirus infection of cultivated potato in sub-Himalayan West Bengal of Eastern India. PMID:24813019

Saha, Aniruddha; Saha, Bikram; Saha, Dipanwita

2014-05-01

68

Characterization of a New World Monopartite Begomovirus Causing Leaf Curl Disease of Tomato in Ecuador and Peru Reveals a New Direction in Geminivirus Evolution  

PubMed Central

All characterized whitefly-transmitted geminiviruses (begomoviruses) with origins in the New World (NW) have bipartite genomes composed of a DNA-A and DNA-B component. Recently, an NW begomovirus lacking a DNA-B component was associated with tomato leaf curl disease (ToLCD) in Peru, and it was named Tomato leaf deformation virus (ToLDeV). Here, we show that isolates of ToLDeV associated with ToLCD in Ecuador and Peru have a single, genetically diverse genomic DNA that is most closely related to DNA-A components of NW bipartite begomoviruses. Agroinoculation of multimeric clones of the genomic DNA of three ToLDeV genotypes (two variants and a strain) resulted in the development of tomato leaf curl symptoms indistinguishable from those of ToLCD in Ecuador and Peru. Biological properties of these ToLDeV genotypes were similar to those of Old World (OW) monopartite tomato-infecting begomoviruses, including lack of sap transmissibility, phloem limitation, a resistance phenotype in tomato germplasm with the Ty-1 gene, and functional properties of the V1 (capsid protein) and C4 genes. Differences in symptom phenotypes induced by the ToLDeV genotypes in tomato and Nicotiana benthamiana plants were associated with a highly divergent left intergenic region and C4 gene. Together, these results establish that ToLDeV is an emergent NW monopartite begomovirus that is causing ToLCD in Ecuador and Peru. This is the first report of an indigenous NW monopartite begomovirus, and evidence is presented that it emerged from the DNA-A component of a NW bipartite progenitor via convergent evolution and recombination. PMID:23468482

Melgarejo, Tomas A.; Kon, Tatsuya; Rojas, Maria R.; Paz-Carrasco, Lenin; Zerbini, F. Murilo

2013-01-01

69

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

Microsoft Academic Search

Pepper (Capsicum annuum) is an important crop worldwide. In Israel, approximately 2,500 ha are grown all year round for the local and export markets.\\u000a Herein, we report the identification of a viral pathogen causing a new devastating disease in pepper crops. The disease syndrome\\u000a includes shortening of stem internodes, interveinal yellowing, and upward rolling of the leaf blade, accompanied by fruit

Aviv Dombrovsky; Eyal Glanz; Mali Pearlsman; Oded Lachman; Yehezkel Antignus

2010-01-01

70

Peptide Aptamers That Bind to Geminivirus Replication Proteins Confer a Resistance Phenotype to Tomato Yellow Leaf Curl Virus and Tomato Mottle Virus Infection in Tomato  

PubMed Central

Geminiviruses constitute a large family of single-stranded DNA viruses that cause serious losses in important crops worldwide. They often exist in disease complexes and have high recombination and mutation rates, allowing them to adapt rapidly to new hosts and environments. Thus, an effective resistance strategy must be general in character and able to target multiple viruses. The geminivirus replication protein (Rep) is a good target for broad-based disease control because it is highly conserved and required for viral replication. In an earlier study, we identified a set of peptide aptamers that bind to Rep and reduce viral replication in cultured plant cells. In this study, we selected 16 of the peptide aptamers for further analysis in yeast two-hybrid assays. The results of these experiments showed that all 16 peptide aptamers interact with all or most of the Rep proteins from nine viruses representing the three major Geminiviridae genera and identified two peptide aptamers (A22 and A64) that interact strongly with different regions in the Rep N terminus. Transgenic tomato lines expressing A22 or A64 and inoculated with Tomato yellow leaf curl virus or Tomato mottle virus exhibited delayed viral DNA accumulation and often contained lower levels of viral DNA. Strikingly, the effect on symptoms was stronger, with many of the plants showing no symptoms or strongly attenuated symptoms. Together, these results established the efficacy of using Rep-binding peptide aptamers to develop crops that are resistant to diverse geminiviruses. PMID:23824791

Reyes, Maria Ines; Nash, Tara E.; Dallas, Mary M.; Ascencio-Ibanez, J. Trinidad

2013-01-01

71

Sweet pepper confirmed as a reservoir host for tomato yellow leaf curl virus by both agro-inoculation and whitefly-mediated inoculation.  

PubMed

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus, has a single-stranded DNA genome. TYLCV can induce severe disease symptoms on tomato plants, but other hosts plants such as cucurbits and peppers are asymptomatic. A full-length DNA clone of a Korean TYLCV isolate was constructed by rolling-circle amplification from TYLCV-infected tomatoes in Korea. To assess relative susceptibility of sweet pepper varieties to TYLCV, 19 cultivars were inoculated with cloned TYLCV by agro-inoculation. All TYLCV-infected sweet peppers were asymptomatic, even though Southern hybridization and polymerase chain reaction analysis showed TYLCV genomic DNA accumulation in roots, stems, and newly produced shoots. Southern hybridization indicated that TYLCV replicated and moved systemically from agro-inoculated apical shoot tips to roots or newly produced shoots of sweet peppers. Whitefly-mediated inoculation experiments showed that TYLCV can be transmitted to tomatoes from TYLCV-infected sweet peppers. Taken together, these results indicate that sweet pepper can be a reservoir for TYLCV in nature. PMID:24777825

Kil, Eui-Joon; Byun, Hee-Seong; Kim, Sunhoo; Kim, Jaedeok; Park, Jungan; Cho, Seungchan; Yang, Dong-Cheol; Lee, Kyeong-Yeoll; Choi, Hong-Soo; Kim, Ji-Kwang; Lee, Sukchan

2014-09-01

72

Rapid spread of a recently introduced virus (tomato yellow leaf curl virus) and its vector Bemisia tabaci (Hemiptera: Aleyrodidae) in Liaoning Province, China.  

PubMed

In Liaoning Province, China, tomato yellow leaf curl virus (TYLCV) was first detected in 2009 and in only four counties. To quantify the spread of TYLCV and to identify potential factors influencing its spread in Liaoning Province, we assayed for TYLCV within 1,055 whiteflies (Bemisia tabaci (Gennadius) complex) from 74 populations and 29 counties in 2011. The B. tabaci species of these individuals was determined based on molecular markers. TYLCV was found in 13 counties (Donggang, Liaoyang, Kazuo, Lingyuan, Heishan, Liaozhong, Kaiyuan, Taian, Dawa, Dashiqiao, Beizhen, Linghai, and Xingcheng) and was most frequently detected in the central plain. In addition, the percentage of whiteflies with TYLCV was significantly higher in B. tabaci Q than in B. tabaci B but was unrelated to the hosts (pepper, eggplant, tomato, cucumber, and kidney bean) on which the whiteflies had been collected. These results demonstrate that TYLCV has spread rapidly in Liaoning Province since its first detection and suggest that its spread is more closely associated with the introduction of B. tabaci Q than with the species of host plant. These findings also indicate that controls are now needed to reduce the further spread of TYLCV and that these controls should include the management of B. tabaci Q populations. PMID:24665690

Zhang, Wan-Min; Fu, Hai-Bin; Wang, Wen-Hang; Piao, Chun-Shu; Tao, Yun-Li; Guo, Dong; Chu, Dong

2014-02-01

73

In silico prediction of cotton (Gossypium hirsutum) encoded microRNAs targets in the genome of Cotton leaf curl Allahabad virus.  

PubMed

Cotton leaf curl Allahabad virus (CLCuAV) belongs to genus Begomovirus, family Geminiviridae. It has single stranded monopartite DNA genome transmitted by whitefly (Bemisia tabaci). MicroRNAs (miRNAs) belong to class of endogeneous small RNAs which suppress expression of genes following cleavage or translational inhibition of target messenger RNAs. They are demonstrated to be involved in a number of plant processes such as, development, biotic and abiotic stresses. Employing in silico approach, high scoring miRNA-target pairs satisfying rules of minimum free energy and maximum complementarity were selected to investigate if they possess the potential to bind the genome CLCuAV. Our results revealed that miRNA species viz., ghr-miR2950 can target all the viral genes, ghr-miR408 targets overlapping transcripts of AC1 and AC2 genes; while ghr-miR394 and ghr-miR395a and miR395d could bind overlapping transcripts of AC1 and AC4 genes. This is the first report of prediction of cotton miRNAs which have the potential to target CLCuAV genes including AC1 and AC4, involved in viral replication and gene silencing suppression, respectively. PMID:24966530

Shweta; Khan, Jawaid A

2014-01-01

74

In silico prediction of cotton (Gossypium hirsutum) encoded microRNAs targets in the genome of Cotton leaf curl Allahabad virus  

PubMed Central

Cotton leaf curl Allahabad virus (CLCuAV) belongs to genus Begomovirus, family Geminiviridae. It has single stranded monopartite DNA genome transmitted by whitefly (Bemisia tabaci). MicroRNAs (miRNAs) belong to class of endogeneous small RNAs which suppress expression of genes following cleavage or translational inhibition of target messenger RNAs. They are demonstrated to be involved in a number of plant processes such as, development, biotic and abiotic stresses. Employing in silico approach, high scoring miRNA-target pairs satisfying rules of minimum free energy and maximum complementarity were selected to investigate if they possess the potential to bind the genome CLCuAV. Our results revealed that miRNA species viz., ghr-miR2950 can target all the viral genes, ghr-miR408 targets overlapping transcripts of AC1 and AC2 genes; while ghr-miR394 and ghr-miR395a and miR395d could bind overlapping transcripts of AC1 and AC4 genes. This is the first report of prediction of cotton miRNAs which have the potential to target CLCuAV genes including AC1 and AC4, involved in viral replication and gene silencing suppression, respectively. PMID:24966530

Shweta; Khan, Jawaid A

2014-01-01

75

RNA viruses and their silencing suppressors boost Abutilon mosaic virus, but not the Old World Tomato yellow leaf curl Sardinia virus.  

PubMed

Mixed viral infections can induce different changes in symptom development, genome accumulation and tissue tropism. These issues were investigated for two phloem-limited begomoviruses, Abutilon mosaic virus (AbMV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) in Nicotiana benthamiana plants doubly infected by either the potyvirus Cowpea aphid-borne mosaic virus (CABMV) or the tombusvirus Artichoke mottled crinkle virus (AMCV). Both RNA viruses induced an increase of the amount of AbMV, led to its occasional egress from the phloem and induced symptom aggravation, while the amount and tissue tropism of TYLCSV were almost unaffected. In transgenic plants expressing the silencing suppressors of CABMV (HC-Pro) or AMCV (P19), AbMV was supported to a much lesser extent than in the mixed infections, with the effect of CABMV HC-Pro being superior to that of AMCV P19. Neither of the silencing suppressors influenced TYLCSV accumulation. These results demonstrate that begomoviruses differentially respond to the invasion of other viruses and to silencing suppression. PMID:21843560

Sardo, Luca; Wege, Christina; Kober, Sigrid; Kocher, Conny; Accotto, Gian Paolo; Noris, Emanuela

2011-11-01

76

Kinetics of interaction of Cotton Leaf Curl Kokhran Virus-Dabawali (CLCuKV-Dab) coat protein and its mutants with ssDNA  

SciTech Connect

Gemini viral assembly and transport of viral DNA into nucleus for replication, essentially involve DNA-coat protein interactions. The kinetics of interaction of Cotton Leaf Curl Kokhran Virus-Dabawali recombinant coat protein (rCP) with DNA was studied by electrophoretic mobility shift assay (EMSA) and surface plasmon resonance (SPR). The rCP interacted with ssDNA with a K{sub A}, of 2.6 +- 0.29 x 10{sup 8} M{sup -1} in a sequence non-specific manner. The CP has a conserved C2H2 type zinc finger motif composed of residues C68, C72, H81 and H85. Mutation of these residues to alanine resulted in reduced binding to DNA probes. The H85A mutant rCP showed the least binding with approximately 756 fold loss in the association rate and a three order magnitude decrease in the binding affinity as compared to rCP. The CP-DNA interactions via the zinc finger motif could play a crucial role in virus assembly and in nuclear transport.

Priyadarshini, C.G. Poornima [Department of Biochemistry, Indian Institute of Science, Bangalore 560012 (India); Savithri, H.S., E-mail: bchss@biochem.iisc.ernet.i [Department of Biochemistry, Indian Institute of Science, Bangalore 560012 (India)

2009-04-10

77

A begomovirus associated with Ageratum yellow vein disease in Indonesia: evidence for natural recombination between tomato leaf curl Java virus and Ageratum yellow vein virus-[Java].  

PubMed

A begomovirus (2747 nucleotides) and a satellite DNA beta component (1360 nucleotides) have been isolated from Ageratum conyzoides L. plants with yellow vein symptoms growing in Java, Indonesia. The begomovirus is most closely related to Tomato leaf curl Java virus (ToLCJV) (91 and 98% in the total nucleotide and coat protein amino acid sequences, respectively), although the products of ORFs C1 and C4 are more closely related to those of Ageratum yellow vein virus-[Java] (91 and 95% identity, respectively). For this reason, the begomovirus it is considered to be a strain of ToLCJV and is referred to as ToLCJV-Ageratum. The virus probably derives from a recombination event in which nucleotides 2389-2692 of ToLCJV have been replaced with the corresponding region of the AYVV-[Java] genome, which includes the 5' part of the intergenic region and the C1 and C4 ORFs. Infection of A. conyzoides with ToLCJV-Ageratum alone produced no symptoms, but co-infection with DNAbeta induced yellow vein symptoms. Symptoms induced in Nicotiana benthamiana by ToLCJV-Ageratum, ToLCJV and AYVV-[Java] are consistent with the exchange of pathogenicity determinant ORF C4 during recombination. PMID:17294343

Kon, T; Kuwabara, K; Hidayat, S H; Ikegami, M

2007-01-01

78

Progressive aggregation of Tomato yellow leaf curl virus coat protein in systemically infected tomato plants, susceptible and resistant to the virus.  

PubMed

Tomato yellow leaf curl virus (TYLCV) coat protein (CP) accumulated in tomato leaves during infection. The CP was immuno-detected in the phloem associated cells. At the early stages of infection, punctate signals were detected in the cytoplasm, while in the later stages aggregates of increasing size were localized in cytoplasm and nuclei. Sedimentation of protein extracts through sucrose gradients confirmed that progress of infection was accompanied by the formation of CP aggregates of increasing size. Genomic ssDNA was found in the cytoplasm and in the nucleus, while the dsDNA replicative form was exclusively associated with the nucleus. CP-DNA complexes were detected by immuno-capture PCR in nuclear and cytoplasmic large aggregates. Nuclear aggregates contained infectious particles transmissible to test plants by whiteflies. In contrast to susceptible tomatoes, the formation of large CP aggregates in resistant plants was delayed. By experimentally changing the level of resistance/susceptibility of plants, we showed that maintenance of midsized CP aggregates was associated with resistance, while large aggregates where characteristic of susceptibility. We propose that sequestering of virus CP into midsized aggregates and retarding the formation of large insoluble aggregates containing infectious particles is part of the response of resistant plants to TYLCV. PMID:23099086

Gorovits, Rena; Moshe, Adi; Kolot, Mikhail; Sobol, Iris; Czosnek, Henryk

2013-01-01

79

FOOD PRESERVATION SERIES Summer Squash  

E-print Network

FOOD PRESERVATION SERIES Summer Squash RECOMMENDED VARIETIES hOW TO STORE QUICK AND EASY SERVING squash. 1 to 1 ¼ pounds one pint frozen summer squash. FOOD SAFETY TIPS Summer Squash Purchase squash not become soggy. FREEZING SUMMER SQUASH SLICES Wash and cut summer squash into 1 ½ -inch slices. Bring about

80

Virion Stability Is Important for the Circulative Transmission of Tomato Yellow Leaf Curl Sardinia Virus by Bemisia tabaci, but Virion Access to Salivary Glands Does Not Guarantee Transmissibility? †  

PubMed Central

The capsid protein (CP) of the monopartite begomovirus Tomato yellow leaf curl Sardinia virus (TYLCSV), family Geminiviridae, is indispensable for plant infection and vector transmission. A region between amino acids 129 and 152 is critical for virion assembly and insect transmissibility. Two previously described mutants, one with a double Q129P Q134H mutation (PNHD) and another with a further D152E change (PNHE), were found nontransmissible (NT). Another NT mutant with a single N130D change (QDQD) was retrieved from a new mutational analysis. In this study, these three NT mutants and the wild-type (wt) virus were compared in their relationships with the whitefly vector Bemisia tabaci and the nonvector Trialeurodes vaporariorum. Retention kinetics of NT mutants were analyzed by quantitative dot blot hybridization in whiteflies fed on infected plants. The QDQD mutant, whose virions appeared nongeminate following purification, was hardly detectable in either whitefly species at any sampling time. The PNHD mutant was acquired and circulated in both whitefly species for up to 10 days, like the wt virus, while PNHE circulated in B. tabaci only. Using immunogold labeling, both PNHD and PNHE CPs were detected in B. tabaci salivary glands (SGs) like the wt virus, while no labeling was found in any whitefly tissue with the QDQD mutant. Significant inhibition of transmission of the wt virus was observed after prior feeding of the insects on plants infected with the PNHE mutant, but not on plants infected with the other mutants. Virion stability and ability to cross the SG barrier are necessary for TYLCSV transmission, but interactions with molecular components inside the SGs are also critical for transmissibility. PMID:19321611

Caciagli, Piero; Medina Piles, Vicente; Marian, Daniele; Vecchiati, Manuela; Masenga, Vera; Mason, Giovanna; Falcioni, Tania; Noris, Emanuela

2009-01-01

81

Quantification and Localization of Watermelon Chlorotic Stunt Virus and Tomato Yellow Leaf Curl Virus (Geminiviridae) in Populations of Bemisia tabaci (Hemiptera, Aleyrodidae) with Differential Virus Transmission Characteristics  

PubMed Central

Bemisia tabaci (Gennadius) is one of the economically most damaging insects to crops in tropical and subtropical regions. Severe damage is caused by feeding and more seriously by transmitting viruses. Those of the genus begomovirus (Geminiviridae) cause the most significant crop diseases and are transmitted by B. tabaci in a persistent circulative mode, a process which is largely unknown. To analyze the translocation and to identify critical determinants for transmission, two populations of B. tabaci MEAM1 were compared for transmitting Watermelon chlorotic stunt virus (WmCSV) and Tomato yellow leaf curl virus (TYLCV). Insect populations were chosen because of their high and respectively low virus transmission efficiency to compare uptake and translocation of virus through insects. Both populations harbored Rickettsia, Hamiltonella and Wolbachia in comparable ratios indicating that endosymbionts might not contribute to the different transmission rates. Quantification by qPCR revealed that WmCSV uptake and virus concentrations in midguts and primary salivary glands were generally higher than TYLCV due to higher virus contents of the source plants. Both viruses accumulated higher in insects from the efficiently compared to the poorly transmitting population. In the latter, virus translocation into the hemolymph was delayed and virus passage was impeded with limited numbers of viruses translocated. FISH analysis confirmed these results with similar virus distribution found in excised organs of both populations. No virus accumulation was found in the midgut lumen of the poor transmitter because of a restrained virus translocation. Results suggest that the poorly transmitting population comprised insects that lacked transmission competence. Those were selected to develop a population that lacks virus transmission. Investigations with insects lacking transmission showed that virus concentrations in midguts were reduced and only negligible virus amounts were found at the primary salivary glands indicating for a missing or modified receptor responsible for virus attachment or translocation. PMID:25365330

Kollenberg, Mario; Winter, Stephan; Gotz, Monika

2014-01-01

82

The complete genomic sequence of pepper yellow leaf curl virus (PYLCV) and its implications for our understanding of evolution dynamics in the genus polerovirus.  

PubMed

We determined the complete sequence and organization of the genome of a putative member of the genus Polerovirus tentatively named Pepper yellow leaf curl virus (PYLCV). PYLCV has a wider host range than Tobacco vein-distorting virus (TVDV) and has a close serological relationship with Cucurbit aphid-borne yellows virus (CABYV) (both poleroviruses). The extracted viral RNA was subjected to SOLiD next-generation sequence analysis and used as a template for reverse transcription synthesis, which was followed by PCR amplification. The ssRNA genome of PYLCV includes 6,028 nucleotides encoding six open reading frames (ORFs), which is typical of the genus Polerovirus. Comparisons of the deduced amino acid sequences of the PYLCV ORFs 2-4 and ORF5, indicate that there are high levels of similarity between these sequences to ORFs 2-4 of TVDV (84-93%) and to ORF5 of CABYV (87%). Both PYLCV and Pepper vein yellowing virus (PeVYV) contain sequences that point to a common ancestral polerovirus. The recombination breakpoint which is located at CABYV ORF3, which encodes the viral coat protein (CP), may explain the CABYV-like sequences found in the genomes of the pepper infecting viruses PYLCV and PeVYV. Two additional regions unique to PYLCV (PY1 and PY2) were identified between nucleotides 4,962 and 5,061 (ORF 5) and between positions 5,866 and 6,028 in the 3' NCR. Sequence analysis of the pepper-infecting PeVYV revealed three unique regions (Pe1-Pe3) with no similarity to other members of the genus Polerovirus. Genomic analyses of PYLCV and PeVYV suggest that the speciation of these viruses occurred through putative recombination event(s) between poleroviruses co-infecting a common host(s), resulting in the emergence of PYLCV, a novel pathogen with a wider host range. PMID:23936244

Dombrovsky, Aviv; Glanz, Eyal; Lachman, Oded; Sela, Noa; Doron-Faigenboim, Adi; Antignus, Yehezkel

2013-01-01

83

Evaluation of Cotton Leaf Curl Virus Resistance in BC1, BC2, and BC3 Progenies from an Interspecific Cross between Gossypium arboreum and Gossypium hirsutum  

PubMed Central

Cotton leaf curl virus disease (CLCuD) is an important constraint to cotton production. The resistance of G. arboreum to this devastating disease is well documented. In the present investigation, we explored the possibility of transferring genes for resistance to CLCuD from G. arboreum (2n?=?26) cv 15-Mollisoni into G. hirsutum (2n?=?52) cv CRSM-38 through conventional breeding. We investigated the cytology of the BC1 to BC3 progenies of direct and reciprocal crosses of G. arboreum and G. hirsutum and evaluated their resistance to CLCuD. The F1 progenies were completely resistant to this disease, while a decrease in resistance was observed in all backcross generations. As backcrossing progressed, the disease incidence increased in BC1 (1.7–2.0%), BC2 (1.8–4.0%), and BC3 (4.2–7.0%). However, the disease incidence was much lower than that of the check variety CIM-496, with a CLCuD incidence of 96%. Additionally, the disease incidence percentage was lower in the direct cross 2(G. arboreum)×G. hirsutum than in that of G. hirsutum×G. arboreum. Phenotypic resemblance of BC1 ?BC3 progenies to G. arboreum confirmed the success of cross between the two species. Cytological studies of CLCuD-resistant plants revealed that the frequency of univalents and multivalents was high in BC1, with sterile or partially fertile plants, but low in BC2 (in both combinations), with shy bearing plants. In BC3, most of the plants exhibited normal bearing ability due to the high frequency of chromosome associations (bivalents). The assessment of CLCuD through grafting showed that the BC1 to BC3 progenies were highly resistant to this disease. Thus, this study successfully demonstrates the possibility of introgressing CLCuD resistance genes from G. arboreum to G. hirsutum. PMID:25372141

Nazeer, Wajad; Tipu, Abdul Latif; Ahmad, Saghir; Mahmood, Khalid; Mahmood, Abid; Zhou, Baoliang

2014-01-01

84

Global Analysis of the Transcriptional Response of Whitefly to Tomato Yellow Leaf Curl China Virus Reveals the Relationship of Coevolved Adaptations? †  

PubMed Central

The begomoviruses are the largest and most economically important group of plant viruses transmitted exclusively by the whitefly Bemisia tabaci in a circulative, persistent manner. The circulation of the viruses within the insect vectors involves complex interactions between virus and vector components; however, the molecular mechanisms of these interactions remain largely unknown. Here we investigated the transcriptional response of the invasive B. tabaci Middle East-Asia Minor 1 species to Tomato yellow leaf curl China virus (TYLCCNV) using Illumina sequencing technology. Results showed that 1,606 genes involved in 157 biochemical pathways were differentially expressed in the viruliferous whiteflies. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that TYLCCNV can perturb the cell cycle and primary metabolism in the whitefly, which explains the negative effect of this virus on the longevity and fecundity of B. tabaci. Our data also demonstrated that TYLCCNV can activate whitefly immune responses, such as autophagy and antimicrobial peptide production, which might lead to a gradual decrease of viral particles within the body of the viruliferous whitefly. Furthermore, PCR results showed that TYLCCNV can invade the ovary and fat body tissues of the whitefly, and Lysotracker and Western blot analyses revealed that the invasion of TYLCCNV induced autophagy in both the ovary and fat body tissues. Surprisingly, TYLCCNV also suppressed the whitefly immune responses by downregulating the expression of genes involved in Toll-like signaling and mitogen-activated protein kinase (MAPK) pathways. Taken together, these results reveal the relationship of coevolved adaptations between begomoviruses and whiteflies and will provide a road map for future investigations into the complex interactions between plant viruses and their insect vectors. PMID:21270146

Luan, Jun-Bo; Li, Jun-Min; Varela, Nelia; Wang, Yong-Liang; Li, Fang-Fang; Bao, Yan-Yuan; Zhang, Chuan-Xi; Liu, Shu-Sheng; Wang, Xiao-Wei

2011-01-01

85

A developmentally regulated lipocalin-like gene is overexpressed in Tomato yellow leaf curl virus-resistant tomato plants upon virus inoculation, and its silencing abolishes resistance.  

PubMed

To discover genes involved in tomato resistance to Tomato yellow leaf curl virus (TYLCV), we previously compared cDNA libraries from susceptible (S) and resistant (R) tomato lines. Among the genes preferentially expressed in R plants and upregulated by TYLCV infection was a gene encoding a lipocalin-like protein. This gene was termed Solanum lycopersicum virus resistant/susceptible lipocalin (SlVRSLip). The SlVRSLip structural gene sequence of R and S plants was identical. SlVRSLip was expressed in leaves during a 15-day window starting about 40 days after sowing (20 days after planting). SlVRSLip was upregulated by Bemisia tabaci (the TYLCV vector) feeding on R plant leaves, and even more strongly upregulated following whitefly-mediated TYLCV inoculation. Silencing of SlVRSLip in R plants led to the collapse of resistance upon TYLCV inoculation and to a necrotic response along the stem and petioles accompanied by ROS production. Contrary to previously identified tomato lipocalin gene DQ222981, SlVRSLip was not regulated by cold, nor was it regulated by heat or salt. The expression of SlVRSLip was inhibited in R plants in which the hexose transporter gene LeHT1 was silenced. In contrast, the expression of LeHT1 was not inhibited in SlVRSLip-silenced R plants. Hence, in the hierarchy of the gene network conferring TYLCV resistance, SlVRSLip is downstream of LeHT1. Silencing of another gene involved in resistance, a Permease-I like protein, did not affect the expression of SlVRSLip and LeHT1; expression of the Permease was not affected by silencing SlVRSLip or LeHT1, suggesting that it does not belong to the same network. The triple co-silencing of SlVRSLip, LeHT1 and Permease provoked an immediate cessation of growth of R plants upon infection and the accumulation of large amounts of virus. SlVRSLip is the first lipocalin-like gene shown to be involved in resistance to a plant virus. PMID:22843056

Sade, Dagan; Eybishtz, Assaf; Gorovits, Rena; Sobol, Iris; Czosnek, Henryk

2012-10-01

86

Infection of tomato leaf curl New Delhi virus (ToLCNDV), a bipartite begomovirus with betasatellites, results in enhanced level of helper virus components and antagonistic interaction between DNA B and betasatellites.  

PubMed

Tomato leaf curl New Delhi virus (ToLCNDV) (Geminiviridae) is an important pathogen that severely affects tomato production. An extensive survey was carried out during 2003-2010 to study the diversity of begomoviruses found in tomato, potato, and cucurbits that showed symptoms of leaf puckering, distortion, curling, vein clearing, and yellow mosaic in various fields in different regions of India. Ten begomovirus isolates were cloned from infected samples and identified as belonging to the species ToLCNDV. A total of 44 % of the samples showed association of betasatellites, with CLCuMuB and LuLDB being the most frequent. The ToLCNDV cloned component DNA A and DNA B were agroinoculated on Nicotiana benthamiana and tomato (Solanum lycopersicum) plants with or without betasatellites, CLCuMuB or LuLDB. The viral genome levels were then monitored by real-time polymerase chain reaction at different time points of disease development. Plants co-inoculated with betasatellites showed enhanced symptom severity in both N. benthamiana and tomato, as well as increases in helper viral DNA A and DNA B levels. The DNA B and betasatellites acted antagonistically to each other, so that the level of DNA B was 16-fold greater in the presence of betasatellites, while accumulation of betasatellites, CLCuMuB and LuLDB, were reduced by 60 % in the presence of DNA B. DNA B-mediated symptoms predominated in CLCuMuB-inoculated plants, whereas betasatellite-mediated leaf abnormalities were prominent in LuLDB-co-inoculated plants. Inoculation with the cloned components will be a good biotechnological tool in resistance breeding program. PMID:23306645

Jyothsna, P; Haq, Q M I; Singh, Priyanka; Sumiya, K V; Praveen, Shelly; Rawat, Ramaveer; Briddon, Rob W; Malathi, V G

2013-06-01

87

Faithful Squashed Entanglement  

Microsoft Academic Search

Squashed entanglement is a measure for the entanglement of bipartite quantum states. In this paper we present a lower bound\\u000a for squashed entanglement in terms of a distance to the set of separable states. This implies that squashed entanglement is\\u000a faithful, that is, it is strictly positive if and only if the state is entangled.\\u000a \\u000a \\u000a We derive the lower bound

Fernando G. S. L. Brandão; Matthias Christandl; Jon Yard

2011-01-01

88

Effect of a single amino acid substitution in the NLS domain of Tomato yellow leaf curl virus-Israel (TYLCV-IL) capsid protein (CP) on its activity and on the virus life cycle.  

PubMed

The capsid protein (CP) of Tomato yellow leaf curl virus-Israel (TYLCV-IL), encoded by the v1 gene, is the only known component of the viral capsid. Three point mutations introduced into the conserved NLS region of the CP were investigated. One mutant, in which the Arg at position 19 was converted to Leu, had the most significant effect on the CP-CP homotypic interaction as well as on CP's interaction with its nuclear receptor karyopherin ?1 and with the protein GroEL. The latter has been suggested to protect the virions in the insect vector hemolymph. These effects were first observed by yeast two-hybrid assay and then confirmed in tobacco protoplasts by measuring fluorescence resonance energy transfer (FRET) between YFP- and CFP-tagged proteins. Most importantly, when the point mutation converting Arg 19 to Leu was introduced into the full-length TYLCV genome, it disrupted its ability to cause symptoms. PMID:21376764

Yaakov, Noga; Levy, Yael; Belausov, Eduard; Gaba, Victor; Lapidot, Moshe; Gafni, Yedidya

2011-06-01

89

FOOD PRESERVATION SERIES Winter Squash  

E-print Network

FOOD PRESERVATION SERIES Winter Squash RECOMMENDED VARIETIES hOW TO STORE Winter Squash Michigan, Butternut, Golden Delicious, Hubbard, Spaghetti are recommended for freezing. yield Acorn squash is round be served like pasta. FOOD SAFETY TIPS One pound 1 large acorn squash. 4 half-cup servings. 1 ½ cups mashed

90

First curl, then wrinkle.  

PubMed

The excellent properties of elastomers are exploited to trigger wrinkling instabilities in curved shells. Micro- and nano-fibres are produced by electrospinning and UV irradiated: each fibre consists of a soft core and a stiff outer half-shell. Upon solvent de-swelling, the fibres curl because the shell and the core have different natural lengths. Wrinkling only starts after the fibre has attained a well-defined helical shape. A simple analytical model is proposed to find the curling curvature and wrinkle wavelength, as well as the transition between the "curling" and "wrinkling" regimes. This new instability resembles that found in the tendrils of climbing plants as they dry and lignify. PMID:23959824

Trindade, Ana C; Canejo, João P; Teixeira, Paulo I C; Patrício, Pedro; Godinho, Maria H

2013-10-01

91

Curls of My Dreams.  

ERIC Educational Resources Information Center

Describes an art activity in which students draw ribbons (thin watercolor paper that, when torn, will stand up in a curling fashion). Explains in detail the assignment in which students used pencil rendering or charcoal pencil depending on the type of paper used for the assignment. (CMK)

Greenman, Geri

2001-01-01

92

Curled up pill bug  

NSDL National Science Digital Library

This pill bug, sometimes called a woodlouse, sow bug, or roly poley, is curled into a ball to protect itself. Pill bugs often do this as a defensive measure so that anything that might attack it has a harder time getting to its underside.

Joaquim Alves Gaspar (Portuguese Navy;)

2007-10-09

93

Physics of curling ribbons  

Microsoft Academic Search

Curling decorative ribbons by dragging it past one's thumb and the blade of a scissor is a well known technique used frequently. However a quantitative understanding of this apparently simple phenomenon is still lacking. We present results from recent experimental and theoretical investigations of this problem. Using the insights gained from this we propose a method of generating novel shapes

Anna M. Klales; Buddhapriya Chakrabarti; Vincenzo Vitelli; L. Mahadevan; Vinothan Manoharan

2007-01-01

94

Squash operator and symmetry  

SciTech Connect

This article begins with a simple proof of the existence of squash operators compatible with the Bennett-Brassard 1984 (BB84) protocol that suits single-mode as well as multimode threshold detectors. The proof shows that, when a given detector is symmetric under cyclic group C{sub 4}, and a certain observable associated with it has rank two as a matrix, then there always exists a corresponding squash operator. Next, we go on to investigate whether the above restriction of 'rank two' can be eliminated; i.e., is cyclic symmetry alone sufficient to guarantee the existence of a squash operator? The motivation behind this question is that, if this were true, it would imply that one could realize a device-independent and unconditionally secure quantum key distribution protocol. However, the answer turns out to be negative, and moreover, one can instead prove a no-go theorem that any symmetry is, by itself, insufficient to guarantee the existence of a squash operator.

Tsurumaru, Toyohiro [Mitsubishi Electric Corporation, Information Technology R and D Center, 5-1-1 Ofuna, Kamakura-shi, Kanagawa, 247-8501 Japan (Japan)

2010-01-15

95

Discovering host genes involved in the infection by the Tomato Yellow Leaf Curl Virus complex and in the establishment of resistance to the virus using Tobacco Rattle Virus-based post transcriptional gene silencing.  

PubMed

The development of high-throughput technologies allows for evaluating gene expression at the whole-genome level. Together with proteomic and metabolomic studies, these analyses have resulted in the identification of plant genes whose function or expression is altered as a consequence of pathogen attacks. Members of the Tomato yellow leaf curl virus (TYLCV) complex are among the most important pathogens impairing production of agricultural crops worldwide. To understand how these geminiviruses subjugate plant defenses, and to devise counter-measures, it is essential to identify the host genes affected by infection and to determine their role in susceptible and resistant plants. We have used a reverse genetics approach based on Tobacco rattle virus-induced gene silencing (TRV-VIGS) to uncover genes involved in viral infection of susceptible plants, and to identify genes underlying virus resistance. To identify host genes with a role in geminivirus infection, we have engineered a Nicotiana benthamiana line, coined 2IRGFP, which over-expresses GFP upon virus infection. With this system, we have achieved an accurate description of the dynamics of virus replication in space and time. Upon silencing selected N. benthamiana genes previously shown to be related to host response to geminivirus infection, we have identified eighteen genes involved in a wide array of cellular processes. Plant genes involved in geminivirus resistance were studied by comparing two tomato lines: one resistant (R), the other susceptible (S) to the virus. Sixty-nine genes preferentially expressed in R tomatoes were identified by screening cDNA libraries from infected and uninfected R and S genotypes. Out of the 25 genes studied so far, the silencing of five led to the total collapse of resistance, suggesting their involvement in the resistance gene network. This review of our results indicates that TRV-VIGS is an exquisite reverse genetics tool that may provide new insights into the molecular mechanisms underlying plant infection and resistance to infection by begomoviruses. PMID:23524390

Czosnek, Henryk; Eybishtz, Assaf; Sade, Dagan; Gorovits, Rena; Sobol, Iris; Bejarano, Eduardo; Rosas-Díaz, Tábata; Lozano-Durán, Rosa

2013-03-01

96

Tomato yellow leaf curl virus infection of a resistant tomato line with a silenced sucrose transporter gene LeHT1 results in inhibition of growth, enhanced virus spread, and necrosis.  

PubMed

To identify genes involved in resistance of tomato to Tomato yellow leaf curl virus (TYLCV), cDNA libraries from lines resistant (R) and susceptible (S) to the virus were compared. The hexose transporter LeHT1 was found to be expressed preferentially in R tomato plants. The role of LeHT1 in the establishment of TYLCV resistance was studied in R plants where LeHT1 has been silenced using Tobacco rattle virus-induced gene silencing (TRV VIGS). Following TYLCV inoculation, LeHT1-silenced R plants showed inhibition of growth and enhanced virus accumulation and spread. In addition, a necrotic response was observed along the stem and petioles of infected LeHT1-silenced R plants, but not on infected not-silenced R plants. This response was specific of R plants since it was absent in infected LeHT1-silenced S plants. Necrosis had several characteristics of programmed cell death (PCD): DNA from necrotic tissues presented a PCD-characteristic ladder pattern, the amount of a JNK analogue increased, and production of reactive oxygen was identified by DAB staining. A similar necrotic reaction along stem and petioles was observed in LeHT1-silenced R plants infected with the DNA virus Bean dwarf mosaic virus and the RNA viruses Cucumber mosaic virus and Tobacco mosaic virus. These results constitute the first evidence for a necrotic response backing natural resistance to TYLCV in tomato, confirming that plant defense is organized in multiple layers. They demonstrate that the hexose transporter LeHT1 is essential for the expression of natural resistance against TYLCV and its expression correlates with inhibition of virus replication and movement. PMID:19946703

Eybishtz, Assaf; Peretz, Yuval; Sade, Dagan; Gorovits, Rena; Czosnek, Henryk

2010-02-01

97

Tomato yellow leaf curl Sardinia virus-resistant tomato plants expressing the multifunctional N-terminal domain of the replication-associated protein show transcriptional changes resembling stress-related responses.  

PubMed

The N-terminal domain (amino acids 1-130) of the replication-associated protein (Rep130 ) of Tomato yellow leaf curl Sardinia virus (TYLCSV) retains the ability of full-length Rep to localize to the nucleus and to down-regulate C1 transcription when ectopically expressed in plants, both functions being required to inhibit homologous viral replication. In this study, we analysed the effect of Rep130 expression on virus resistance and the plant transcriptome in the natural and agronomically important host species of TYLCSV, Solanum lycopersicum. Tomato plants accumulating high levels of Rep130 were generated and proved to be resistant to TYLCSV. Using an in vitro assay, we showed that plant-expressed Rep130 also retains the catalytic activity of Rep, thus supporting the notion that this protein domain is fully functional. Interestingly, Rep130 -expressing tomatoes were characterized by an altered transcriptional profile resembling stress-related responses. Notably, the serine-type protease inhibitor (Ser-PI) category was over-represented among the 20 up-regulated genes. The involvement of Rep130 in the alteration of host mRNA steady-state levels was confirmed using a distinct set of virus-resistant transgenic tomato plants expressing the same TYLCSV Rep130 , but from a different, synthetic, gene. Eight genes were found to be up-regulated in both types of transgenic tomato and two encoded Ser-PIs. Four of these eight genes were also up-regulated in TYLCSV-infected wild-type tomato plants. Implications with regard to the ability of this Rep domain to interfere with viral infections and to alter the host transcriptome are discussed. PMID:23910556

Lucioli, Alessandra; Berardi, Alessandra; Gatti, Francesca; Tavazza, Raffaela; Pizzichini, Daniele; Tavazza, Mario

2014-01-01

98

Sport Scholarship programme Squash at Birmingham  

E-print Network

in Birmingham and are often used as hitting partners with the Squash club. #12;Sport scholarships The UniversitySport Scholarship programme Squash at Birmingham University of Birmingham Sport (UBSport) Squash club is one of the most successful student squash clubs in the UK and one of the most consistent across

Heinke, Dietmar

99

Conductance Oscillations in Squashed Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

A combination of molecular dynamics and electrical conductance calculations are used to probe the electromechanical properties of squashed metallic carbon nanotubes. We find that the conductance and bandgap of armchair nanotubes show oscillations upon squashing. The physical origin of these oscillations is attributed to interaction of carbon atoms with a fourth neighbor. Squashing of armchair and zigzag nanotubes ultimately leads to metallic behavior.

Mehrez, H.; Anantram, M. P.; Svizhenko, A.

2003-01-01

100

DNA supercoiling: plectonemes or curls ?  

E-print Network

/decompaction (cell division) mechanical properties influence biology of the cell Tang et al (Structure) 2008 20kbp dsDNA free-energies of straight and supercoiled DNA (experiments) stable mechanical model unstable TransitionDNA supercoiling: plectonemes or curls ? Sébastien Neukirch CNRS & UPMC Univ. Paris 6 (France) John

Neukirch, Sébastien

101

Distributional geometry of squashed cones  

NASA Astrophysics Data System (ADS)

A regularization procedure developed by D. V. Fursaev and S. N. Solodukhin, [Phys. Rev. D 52, 2133 (1995)PRVDAQ0556-2821] for the integral curvature invariants on manifolds with conical singularities is generalized to the case of squashed cones. In general, the squashed conical singularities do not have rotational O(2) symmetry in a subspace orthogonal to a singular surface ? so that the surface is allowed to have extrinsic curvatures. A new feature of the squashed conical singularities is that the surface terms in the integral invariants, in the limit of a small angle deficit, now depend also on the extrinsic curvatures of ?. A case of invariants which are quadratic polynomials of the Riemann curvature is elaborated in different dimensions and applied to several problems related to entanglement entropy. The results are in complete agreement with computations of the logarithmic terms in entanglement entropy of 4D conformal theories [S. N. Solodukhin, Phys. Lett. B 665, 305 (2008)PYLBAJ0370-2693]. Among other applications of the suggested method are logarithmic terms in entanglement entropy of nonconformal theories and a holographic formula for entanglement entropy in theories with gravity duals.

Fursaev, Dmitri V.; Patrushev, Alexander; Solodukhin, Sergey N.

2013-08-01

102

Influence of Water Relations and Temperature on Leaf Movements of Rhododendron Species 1  

PubMed Central

Rhododendron maximum L. and R. Catawbiense L. are subcanopy evergreen shrubs of the eastern United States deciduous forest. Field measurements of climate factors and leaf movements of these species indicated a high correlation between leaf temperature and leaf curling; and between leaf water potential and leaf angle. Laboratory experiments were performed to isolate the influence of temperature and cellular water relations on leaf movements. Significant differences were found between the patterns of temperature induction of leaf curling in the two species. Leaves of the species which curled at higher temperatures (R. catawbiense) also froze at higher leaf temperatures. However, in both cases leaf curling occurred at leaf temperatures two to three degrees above the leaf freezing point. Pressure volume curves indicated that cellular turgor loss was associated with a maximum of 45% curling while 100% or more curling occurred in field leaves which still had positive cell turgor. Moisture release curves indicated that 70% curling requires a loss of greater than 60% of symplastic water which corresponds to leaf water potentials far below those experienced in field situations. Conversely, most laboratory induced changes in leaf angle could be related to leaf cell turgor loss. PMID:16665296

Nilsen, Erik Tallak

1987-01-01

103

Energy Requirements of Squash and Racquetball.  

ERIC Educational Resources Information Center

Oxygen consumption and heart rate were monitored in 32 male adults playing racquetball and squash. Results indicated that energy expenditure in racquetball was only slightly less than for squash, suggesting that either sport is appropriate for developing and maintaining fitness in healthy adults. (Author/CB)

Montpetit, Richard R.; And Others

1987-01-01

104

Swept Away: Exploring the Physics of Curling  

ERIC Educational Resources Information Center

Studying the Olympic sport of curling is a fun and engaging way to learn about the concepts of friction, forces, momentum, and Newton's laws. Each winter, the author takes her eighth-grade physical science class on a field trip to experience curling firsthand. This field trip has become a favorite of the eighth graders at Capitol Hill Day School…

Esser, Liza

2011-01-01

105

Effects of carbohydrate ingestion on skill maintenance in squash players  

Microsoft Academic Search

The effects of carbohydrate (CHO) ingestion during sports which require high levels of motor and cognitive skill, such as squash, have produced conflicting results. This study aimed to explore the effect of CHO ingestion on squash skill following short duration exercise simulating the demands of squash play. Sixteen male squash players of a high standard were recruited. Following a VO2max

Lindsay M. Bottoms; Angus M. Hunter; Stuart D. R. Galloway

2006-01-01

106

Translocation of Sugar and Tritiated Water in Squash Plants 1  

PubMed Central

When 14C-sugar and THO were simultaneously introduced through a cut side vein or flap of a squash leaf (Cucurbita melopepo, Bailey cv. torticollis) concurrent translocation of 14C-sugars, T-photosynthates and THO with parallel, almost flat, gradients was observed in the petiole for periods of 1 to 3 hr. Parallel translocation gradients were not observed when 14C was introduced as 14CO2 and T by painting a leaf with THO. Autoradiography of frozen sections to locate the tissues in which THO was moving was unsuccessful. Steam-girdling blocked the movement of 14C and T when 14C-glucose and THO were introduced simultaneously by the flap-feeding technique. If THO moved as liquid water in the phloem along with the 14C-sugars, as blockage by steam girdling suggests, then solution flow of sugar cannot be excluded as a mechanism of translocation. PMID:16656978

Trip, P.; Gorham, P. R.

1968-01-01

107

Influence of velocity curl on conservation laws  

E-print Network

The paper discusses impact of the velocity curl on some conservation laws in the gravitational field and electromagnetic field, by means of the characteristics of quaternions. When the velocity curl can not be neglected, it will cause the predictions to departure slightly from the conservation laws, which include mass continuity equation, charge continuity equation, and conservation of spin, etc. And the scalar potential of gravitational field has an effect on the speed of light, the conservation of mass, and conservation of charge, etc. The results explain how the velocity curl influences some conservation laws in the gravitational field and electromagnetic field.

Zihua Weng

2008-10-01

108

Comparison of perimeter trap crop varieties: effects on herbivory, pollination, and yield in butternut squash.  

PubMed

Perimeter trap cropping (PTC) is a method of integrated pest management (IPM) in which the main crop is surrounded with a perimeter trap crop that is more attractive to pests. Blue Hubbard (Cucurbita maxima Duch.) is a highly effective trap crop for butternut squash (C. moschata Duch. ex Poir) attacked by striped cucumber beetles (Acalymma vittatum Fabricius), but its limited marketability may reduce adoption of PTC by growers. Research comparing border crop varieties is necessary to provide options for growers. Furthermore, pollinators are critical for cucurbit yield, and the effect of PTC on pollination to main crops is unknown. We examined the effect of five border treatments on herbivory, pollination, and yield in butternut squash and manipulated herbivory and pollination to compare their importance for main crop yield. Blue Hubbard, buttercup squash (C. maxima Duch.), and zucchini (C. pepo L.) were equally attractive to cucumber beetles. Border treatments did not affect butternut leaf damage, but butternut flowers had the fewest beetles when surrounded by Blue Hubbard or buttercup squash. Yield was highest in the Blue Hubbard and buttercup treatments, but this effect was not statistically significant. Native bees accounted for 87% of pollinator visits, and pollination did not limit yield. There was no evidence that border crops competed with the main crop for pollinators. Our results suggest that both buttercup squash and zucchini may be viable alternatives to Blue Hubbard as borders for the main crop of butternut squash. Thus, growers may have multiple border options that reduce pesticide use, effectively manage pests, and do not disturb mutualist interactions with pollinators. PMID:19791616

Adler, L S; Hazzard, R V

2009-02-01

109

Pill bug curled up on back  

NSDL National Science Digital Library

Many pill bugs curl up in a ball to protect themselves. Pill bugs use their antennae to feel around their environment. They use their eyes to see where they are going. They use their legs to walk or crawl around.

Joaquim Alves Gaspar (Portuguese Navy;)

2008-02-09

110

Motion analysis of the international and national rank squash players  

Microsoft Academic Search

In this paper, we present a study on squash player work-rate during the squash matches of two different quality levels. To assess work-rate, the measurement of certain parameters of player motion is needed. The computer vision based software application was used to automatically obtain player motion data from the digitized video recordings of 22 squash matches. The matches were played

G. Vuckovic; B. Dezman; J. Pers; S. Kovacic

2005-01-01

111

FRACTIONAL CURL OPERATOR AND FRACTIONAL WAVEGUIDES  

Microsoft Academic Search

Abstract—Fractional curl operator has been utilized to study the fractional waveguide. The fractional waveguide may,be regarded as intermediate step between the two given waveguides. The two given waveguides are related through the principle of duality. Behavior of field lines in fractional waveguides are studied withrespect to fractional parameter ?.

Akhtar Hussain; Saima Ishfaq; Qaisar A. Naqvi

2006-01-01

112

Stability of squashed Kaluza-Klein black holes  

SciTech Connect

The stability of squashed Kaluza-Klein black holes is studied. The squashed Kaluza-Klein black hole looks like a five-dimensional black hole in the vicinity of horizon and looks like a four-dimensional Minkowski spacetime with a circle at infinity. In this sense, squashed Kaluza-Klein black holes can be regarded as black holes in the Kaluza-Klein spacetimes. Using the symmetry of squashed Kaluza-Klein black holes, SU(2)xU(1){approx_equal}U(2), we obtain master equations for a part of the metric perturbations relevant to the stability. The analysis based on the master equations gives strong evidence for the stability of squashed Kaluza-Klein black holes. Hence, the squashed Kaluza-Klein black holes deserve to be taken seriously as realistic black holes in the Kaluza-Klein spacetime.

Kimura, Masashi; Ishihara, Hideki [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585 (Japan); Murata, Keiju [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan); Soda, Jiro [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan); Kavli Institute for Theoretical Physics, Zhong Guan Cun East Street 55, Beijing 100080 (China)

2008-03-15

113

Squash ball to eye ball: the likelihood of squash players incurring an eye injury.  

PubMed Central

The records of the 118 patients treated as Southampton Eye Hospital during 1978-9 for injuries incurred while playing squash, badminton, tennis, table tennis, cricket, and football show that for squash the main cause of eye injury was the player being hit by the ball. Severe eye injuries--those requiring treatment as an inpatient--were rare but much more frequent than such injuries in other sports. Less serious injuries--those requiring treatment as an outpatient--were also rare, with a frequency comparable with that of similar injuries in football and badminton. Squash players are most unlikely to incur an eye injury, but should this occur it has far-reaching consequences both in the short and the long term. Each individual player must weigh these chances and consequences against the possible inconvenience of using some form of eye protection. PMID:6793167

Barrell, G V; Cooper, P J; Elkington, A R; Macfadyen, J M; Powell, R G; Tormey, P

1981-01-01

114

Leaf peroxidase activities in tomato mutants affecting plant morphology  

Microsoft Academic Search

The leaf peroxidase activity and the electrophoretic banding pattern of 69 tomato mutants affecting plant morphology have been studied. The zymograms of 63 mutants were normal, and their total peroxidase activities were not correlated with a particular plant or leaf trait. However, six mutations, lyrate x-1521, mottled, olivacea, monstrosa, extreme dwarf, and Curl, are characterized by one or two isozymic

G. P. Soressi; E. Gentinetta; M. Odoardi; F. Salamini

1974-01-01

115

Computed tomography of ball pythons (Python regius) in curled recumbency.  

PubMed

Anesthesia and tube restraint methods are often required for computed tomography (CT) of snakes due to their natural tendency to curl up. However, these restraint methods may cause animal stress. The aim of this study was to determine whether the CT appearance of the lungs differs for ball pythons in a curled position vs. tube restraint. Whole body CT was performed on ten clinically healthy ball pythons, first in curled and then in straight positions restrained in a tube. Curved multiplanar reformatted (MPR) lung images from curled position scans were compared with standard MPR lung images from straight position scans. Lung attenuation and thickness were measured at three locations for each scan. Time for positioning and scanning was 12 ± 5 min shorter for curled snakes compared to tube restraint. Lung parenchyma thickness and attenuation declined from cranial to caudal on both straight and curled position images. Mean lung parenchyma thickness was greater in curled images at locations 1 (P = 0.048) and 3 (P = 0.044). Mean lung parenchyma thickness decreased between location 1 and 2 by 86-87% (straight: curled) and between location 1 and 3 by 51-50% (straight: curled). Mean lung attenuation at location 1 was significantly greater on curled position images than tube restraint images (P = 0.043). Findings indicated that CT evaluation of the lungs is feasible for ball pythons positioned in curled recumbency if curved MPR is available. However, lung parenchyma thickness and attenuation in some locations may vary from those acquired using tube restraint. PMID:24438485

Hedley, Joanna; Eatwell, Kevin; Schwarz, Tobias

2014-01-01

116

The physics of sliding cylinders and curling rocks  

NASA Astrophysics Data System (ADS)

The lateral deflection of a rotating cylindrical shell sliding on one of its ends is considered and both theoretical and experimental results are presented. The coefficient of kinetic friction between a curling rock and an ice surface is then derived and compared with experiment. Current models of the motion of a curling rock are discussed and an alternate hypothesis is presented.

Penner, A. Raymond

2001-03-01

117

The Curl of a Vector Field: Beyond the Formula  

ERIC Educational Resources Information Center

It has been widely acknowledged that there is some discrepancy in the teaching of vector calculus in mathematics courses and other applied fields. The curl of a vector field is one topic many students can calculate without understanding its significance. In this paper, we explain the origin of the curl after presenting the standard mathematical…

Burch, Kimberly Jordan; Choi, Youngna

2006-01-01

118

THE CURL OF A VECTOR FIELD: BEYOND THE FORMULA  

Microsoft Academic Search

It has been widely acknowledged that there is some discrepancy in the teaching of vector calculus in mathematics courses and other applied fields. The curl of a vector field is one topic many students can calculate without understanding its significance. In this paper, we explain the origin of the curl after presenting the standard mathematical formulas. We investigate when and

Kimberly Jordan Burch; Youngna Choi

2006-01-01

119

The dynamic behavior of squash balls  

NASA Astrophysics Data System (ADS)

The behavior of a squash ball constitutes an excellent case study of the dynamic behavior of rubbery materials. It is shown that the complex viscoelastic behavior of rubber can be investigated using simple drop bounce tests and compression tests. The drop tests show that the coefficient of restitution increases as the ball temperature increases. The compression tests show that as the speed of compression increases or as the ball temperature decreases, the compressive force and the energy loss both increase. These effects are due to the viscoelastic nature of the rubber and are an excellent example of the time-temperature equivalence of polymers. Compression tests were performed on balls with small holes at the base to separate the effects of the internal air pressure from the material deformation. It was found that the internal air pressure contributed about one-third to the compressive force, but contributed little to energy loss. This behavior shows that the rubber material dominates the rebound behavior and that the normal warming up process at the start of a squash game is important to raise the temperature of the rubber rather than to increase the internal air pressure.

Lewis, Gareth J.; Arnold, J. Cris; Griffiths, Iwan W.

2011-03-01

120

Physical curl forces: dipole dynamics near optical vortices  

NASA Astrophysics Data System (ADS)

The force on a particle with complex electric polarizability is known to be not derivable from a potential, so its curl is non-zero. This ‘curl force’ is studied in detail for motion near an anisotropic optical vortex of arbitrary strength. Fundamental questions are raised by the fact that although the curl force requires the polarizability to have a non-zero imaginary part, reflecting absorption or scattering (‘dissipation’) in the internal dipole dynamics, the particle motion that it generates is non-dissipative (volume-preserving in the position-velocity state space).

Berry, M. V.; Shukla, Pragya

2013-10-01

121

Heart Rate Response and Lactic Acid Concentration in Squash Players.  

ERIC Educational Resources Information Center

It was concluded that playing squash is an activity that results in heart rate responses of sufficient intensity to elicit aerobic training effects without producing high lactic acid concentration in the blood. (MM)

Beaudin, Paula; And Others

1978-01-01

122

The Curl Graphics2d immediate mode rendering API  

E-print Network

(cont.) 170 thousand lines of code in the Curl language. Morgan McGuire has worked on computer graphics and imaging at Morgan Systems, the NEC Research Institute and the IBM T. J. Watson Research Center. He is currently ...

McGuire, Morgan, 1976-

2000-01-01

123

The sports science of curling: a practical review.  

PubMed

Curling is a sport played on ice in which two teams each deliver 8 granite stones towards a target, or 'house'. It is the only sport in which the trajectory of the projectile can be influenced after it has been released by the athlete. This is achieved by sweeping the ice in front of the stone to change the stone-ice friction and thereby enable to stone to travel further, curl more or stay straight. Hard sweeping is physically demanding. Different techniques of sweeping can also have different effects on the stone. This paper will review the current research behind sweeping a curling stone, outline the physiological demands of sweeping, the associated performance effects and suggest potential strategies of sweeping that can be used by both coaches and curling teams. Key pointsSweeping a curling stone can be highly physically demanding.Effective sweeping requires a combination of downward force and brush head speed, determined by the stone velocity.Sweeping on the left or right of a stone can help the stone to remain straight or curl more depending on the rotation of the stone.This can lead to the development of sweeping and playing tactics and contribute to team selection. PMID:24149588

Bradley, John L

2009-01-01

124

Texas Crop Profile: Watermelon  

E-print Network

(Pythium) which is managed with seed treatments, and bacterial fruit blotch (Acidivorax avenae). The squash leaf curl virus, a common dis- ease of fall watermelons, is transmitted by white- flies and can be managed by controlling the white- flies. Other... (Pythium) which is managed with seed treatments, and bacterial fruit blotch (Acidivorax avenae). The squash leaf curl virus, a common dis- ease of fall watermelons, is transmitted by white- flies and can be managed by controlling the white- flies. Other...

Hall, Kent D.; Holloway, Rodney L.; Smith, Dudley

2000-04-12

125

Expression of Ascorbic Acid Oxidase in Zucchini Squash (Cucurbita pepo L.) 1  

PubMed Central

The expression of ascorbic acid oxidase was studied in zucchini squash (Cucurbita pepo L.), one of the most abundant natural sources of the enzyme. In the developing fruit, specific activity of ascorbic acid oxidase was highest between 4 and 6 days after anthesis. Protein and mRNA levels followed the same trend as enzyme activity. Highest growth rate of the fruit occurred before 6 days after anthesis. Within a given fruit, ascorbic acid oxidase activity and mRNA level were highest in the epidermis, and lowest in the central placental region. In leaf tissue, ascorbic acid oxidase activity was higher in young leaves, and very low in old leaves. Within a given leaf, enzyme activity was highest in the fast-growing region (approximately the lower third of the blade), and lowest in the slow-growing region (near leaf apex). High expression of ascorbic acid oxidase at a stage when rapid growth is occurring (in both fruits and leaves), and localization of the enzyme in the fruit epidermis, where cells are under greatest tension during rapid growth in girth, suggest that ascorbic acid oxidase might be involved in reorganization of the cell wall to allow for expansion. Based on the known chemistry of dehydroascorbic acid, the end product of the ascorbic acid oxidase-catalyzed reaction, we have proposed several hypotheses to explain how dehydroascorbic acid might cause cell wall “loosening.” ImagesFigure 3Figure 4Figure 5 PMID:16668145

Lin, Liang-Shiou; Varner, Joseph E.

1991-01-01

126

Esempio 51. In un club sportivo, 36 soci giocano a tennis,28 a squash e 18abadminton. Inoltre, 22soci giocano sia a tennis che a squash, 12sia a tennis che a badminton,  

E-print Network

Esempio 51. In un club sportivo, 36 soci giocano a tennis,28 a squash e 18abadminton. Inoltre, 22soci giocano sia a tennis che a squash, 12sia a tennis che a badminton, 9 sia a squash che a badminton giocano a tennis, S quello dei soci chegio- cano a squash e B quello dei soci che giocano a badminton

Corrado, Tanasi

127

SUSY gauge theories on squashed three-spheres  

NASA Astrophysics Data System (ADS)

We study Euclidean 3D mathcal{N} = 2 supersymmetric gauge theories on squashed three-spheres preserving isometries SU(2) × U(1) or U(1) × U(1). We show that, when a suitable background U(1) gauge field is turned on, these squashed spheres support charged Killing spinors and therefore mathcal{N} = 2 supersymmetric gauge theories. We present the Lagrangian and supersymmetry rules for general gauge theories. The partition functions are computed using localization principle, and are expressed as integrals over Coulomb branch. For the squashed sphere with U(1) × U(1) isometry, its measure and integrand are identified with the building blocks of structure constants in Liouville or Toda conformal field theories with b ? 1.

Hama, Naofumi; Hosomichi, Kazuo; Lee, Sungjay

2011-05-01

128

Fractional Parallel Plate DB Waveguides Using Fractional Curl Operator  

E-print Network

DB boundary conditions have been simulated in terms of perfect electric conductor (PEC) boundary for transverse electric modes and perfect magnetic conductor (PMC) for transverse magnetic modes. Electric and magnetic fields inside the dielectric region of a parallel plate DB boundary waveguide have been derived and fractional curl operator has been utilized to study the fractional parallel plate DB waveguide. Field behavior as well as transverse impedance of the guide walls have been studied with respect to the fractional parameter describing the order of fractional curl operator. The results are also compared with the corresponding results for fractional waveguides with PEC walls.

Akhtar Hussain; Sajid Abbas Naqvi; Ahsan Illahi; Q. A. Naqvi

2011-09-09

129

DIVERGENCE-FREE AND CURL-FREE WAVELETS ON THE SQUARE FOR NUMERICAL SIMULATIONS  

E-print Network

DIVERGENCE-FREE AND CURL-FREE WAVELETS ON THE SQUARE FOR NUMERICAL SIMULATIONS SOULEYMANE KADRI Grenoble cedex 9, France August 30, 2011 Abstract We present a construction of divergence-free and curl-free and integration. We introduce new BMRAs and wavelets for the spaces of divergence-free and curl-free vector

Boyer, Edmond

130

Modelling of transmission through a chiral slab using fractional curl operator  

Microsoft Academic Search

Transmission of electromagnetic plane wave through a slab of reciprocal chiral medium has been modelled using fractional curl operator. It is noted that when order of the fractional curl operator becomes zero, the equivalent situation may correspond to absence of the chiral slab. Variation of the order of fractional curl operator may explore situations which may be regarded as intermediate

S. A. Naqvi; Q. A. Naqvi; A. Hussain

2006-01-01

131

Weed Management in No-Till Zucchini Squash  

Microsoft Academic Search

Weed control in no-tillage (NT) zucchini squash (Cucurbita pepo L.) was determined for various preemergence (PRE) herbicide combinations in herbicide-killed ‘Wheeler’ winter rye (Secale cereale L.) or bare soil. Winter rye provided 65% and 75% control of redroot pigweed (Amaranthus retroflexus L.) and smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.], respectively, in the absence of herbicides compared with no

S. Alan Walters; Bryan G. Young

2011-01-01

132

Tennis-Badminton-Squash Guide. June 1974-June 1976.  

ERIC Educational Resources Information Center

This guide is a collection of essays by various authors on tennis, badminton, and squash. The document is divided into three sections, one for each sport. The topics covered include general teaching methods, methods to employ for teaching specific skills such as the lob or the backhand, the use of visual aids, conditioning drills, study questions,…

Sherman, Patricia, Ed.; And Others

133

Covolume solutions of three dimensional div-curl equations  

NASA Technical Reports Server (NTRS)

Delaunay-Voronoi mesh systems provide a generalization of the classical rectangular staggered meshes to unstructured meshes. It is shown how such 'covolume' discretizations may be applied to div-curl systems in three dimensions. Error estimates are proved and confirmed by a numerical illustration.

Nicolaides, R. A.; Wu, X.

1995-01-01

134

Computation of Surface Integrals of Curl Vector Fields  

ERIC Educational Resources Information Center

This article presents a way of computing a surface integral when the vector field of the integrand is a curl field. Presented in some advanced calculus textbooks such as [1], the technique, as the author experienced, is simple and applicable. The computation is based on Stokes' theorem in 3-space calculus, and thus provides not only a means to…

Hu, Chenglie

2007-01-01

135

Circularly Polarized Curl Antenna Lens With Manual Tilt Properties  

Microsoft Academic Search

A microwave lens based on spatially combining the outputs from a double sided arrangement of circularly polarized printed curl antennas is demonstrated. The lens operating at 2.49 GHz is capable of converting either LH or RH CP incident energy into RH or LH CP respectively. A single element converter is developed as the core lens element. Directivity and coupling studies

Sean M. O'Kane; Vincent F. Fusco

2009-01-01

136

A New Curl-Up Test of Abdominal Endurance.  

ERIC Educational Resources Information Center

This study evaluates a new method of administering a trunk-curl test of abdominal muscular endurance and establishes a series of norms for college students and adults. The test utilizes a piece of cardboard that is cut out so that it can be held at the level of the navel of the testee and perpendicular to the floor. The test is administered with…

Noble, Larry

137

Curl-Noise for Procedural Fluid Flow Robert Bridson  

E-print Network

, without manually adding many vortices, this approach is restricted to fairly laminar flow, and matchingCurl-Noise for Procedural Fluid Flow Robert Bridson University of British Columbia Jim Hourihan are often pre- ferred over simulation, both for speed and for the degree of ani- mator control. We offer

Bridson, Robert

138

The sports science of curling: A practical review  

Microsoft Academic Search

Curling is a sport played on ice in which two teams each deliver 8 granite stones towards a target, or 'house'. It is the only sport in which the trajectory of the projectile can be influenced after it has been released by the athlete. This is achieved by sweeping the ice in front of the stone to change the stone-ice

John L. Bradley

139

Expression of ascorbic acid oxidase in zucchini squash (Cucurbita pepo L. )  

SciTech Connect

The expression of ascorbic acid oxidase was studied in zuchini squash (Cucurbita pepo L.), one of the most abundant natural sources of the enzyme. In the developing fruit, specific activity of ascorbic acid oxidase was highest between 4 and 6 days after anthesis. Protein and mRNA levels followed the same trend as enzyme activity. Highest growth rate of the fruit occurred before 6 days after anthesis. Within a given fruit, ascorbic acid oxidase activity was higher in young leaves, and very low in old leaves. Within a given leaf, enzyme activity was highest in the fast-growing region (approximately the lower third of the blade), and lowest in the central placental region. In leaf tissue, ascorbic acid oxidase activity was higher in young leaves, and very low in old leaves. Within a given leaf, enzyme activity was highest in the fast-growing region (approximately the lower third of the blade), and lowest in the slow-growing region (near leaf apex). High expression of ascorbic acid oxidase at a stage when rapid growth is occurring (in both fruits and leaves), and localization of the enzyme in the fruit epidermis, where cells are under greatest tension during rapid growth in girth, suggest that ascorbic acid oxidase might be involved in reorganization of the cell wall to allow for expansion. Based on the known chemistry of dehydroascorbic acid, the end product of the ascorbic acid oxidase-catalyzed reaction, the authors have proposed several hypotheses to explain how dehydroascorbic acid might cause cell wall loosening.

Lin, Liangshiou; Varner, J.E. (Washington Univ., St. Louis, MO (United States))

1991-05-01

140

Comparative fitness of a wild squash species and three generations of hybrids between wild x virus-resistant transgenic squash.  

PubMed

We compared some fitness components of the wild squash species Cucurbita pepo spp. ovifera var. texana (C. texana) and three generations of hybrids (F1, BC1, and BC2) between C. texana and commercial transgenic squash CZW-3 over three consecutive years under field conditions of low (LDP) and high disease pressure (HDP) by Cucumber mosaic virus (CMV), Zucchini yellow mosaic virus (ZYMV) and Watermelon mosaic virus (WMV). Transgenic squash CZW-3 expresses the coat protein (CP) genes of CMV, ZYMV, and WMV, and is resistant to these three aphid-borne viruses. Across all HDP trials, transgenic BC1 and BC2 hybrids expressing the three CP genes grew more vigorously, displayed resistance to CMV, ZYMV, and WMV, and produced a greater number of mature fruits and viable seeds than nontransgenic hybrid segregants and C. texana. Transgenic F1 hybrids behaved similarly to BC1 and BC2 hybrids but grew less vigorously than C. texana. In contrast, across all LDP trials, C. texana outperformed the transgenic and nontransgenic hybrid segregants. Further, only one back cross was necessary to recover individuals with most of the C. texana characteristics and yet maintain virus resistance. Our data suggest that C. texana acquiring CP transgenes upon hybridization and introgression could have a selective advantage if CMV, ZYMV, and WMV are severely limiting the growth and reproductibility of wild squash populations. PMID:15612352

Fuchs, Marc; Chirco, Ellen M; McFerson, Jim R; Gonsalves, Dennis

2004-01-01

141

Evolution of perturbations of squashed Kaluza-Klein black holes: Escape from instability  

SciTech Connect

The squashed Kaluza-Klien (KK) black holes differ from the Schwarzschild black holes with asymptotic flatness or the black strings even at energies for which the KK modes are not excited yet, so that squashed KK black holes open a window in higher dimensions. Another important feature is that the squashed KK black holes are apparently stable and, thereby, let us avoid the Gregory-Laflamme instability. In the present paper, the evolution of scalar and gravitational perturbations in time and frequency domains is considered for these squashed KK black holes. The scalar field perturbations are analyzed for general rotating squashed KK black holes. Gravitational perturbations for the so-called zero mode are shown to be decayed for nonrotating black holes, in concordance with the stability of the squashed KK black holes. The correlation of quasinormal frequencies with the size of extra dimension is discussed.

Ishihara, Hideki; Kimura, Masashi; Konoplya, Roman A.; Murata, Keiju; Soda, Jiro; Zhidenko, Alexander [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Department of Physics, Kyoto University, Kyoto 606-8501 (Japan); Department of Physics, Kyoto University, Kyoto 606-8501 (Japan) Kavli Institute for Theoretical Physics, Zhong Guan Cun East Street 55, Beijing 100080 (China); Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970, Sao Paulo-SP (Brazil)

2008-04-15

142

Racquet Sports: Tennis, Badminton, Squash, Racquetball, and Handball  

Microsoft Academic Search

\\u000a Racquet sports make up an eclectic group of court activities that can be quite diverse. In this chapter we focus on the following\\u000a racquet sports: tennis, badminton, squash, racquetball, and handball. Though it is beyond the scope of this chapter, it is\\u000a paramount that readers become acquainted with certain background information on each of these individual sports including\\u000a developmental history,

Richard T. Bouché

143

Perturbative partition function for a squashed S5  

NASA Astrophysics Data System (ADS)

We compute the index of 6d {N}=(1,0) theories on S^5× {R} containing vector and hypermultiplets. We only consider the perturbative sector without instantons. By compactifying {R} to S^1 with a twisted boundary condition and taking the small radius limit, we derive the perturbative partition function on a squashed S^5. The 1-loop partition function is represented in a simple form with the triple sine function.

Imamura, Yosuke

2013-07-01

144

Hawking radiation from squashed Kaluza-Klein black holes: A window to extra dimensions  

SciTech Connect

We explore the observability of extra dimensions through five-dimensional squashed Kaluza-Klein black holes residing in the Kaluza-Klein spacetime. With the expectation that the Hawking radiation reflects the five-dimensional nature of the squashed horizon, we study the Hawking radiation of a scalar field in the squashed black hole background. As a result, we show that the luminosity of Hawking radiation tells us the size of the extra dimension, namely, the squashed Kaluza-Klein black holes open a window to extra dimensions.

Ishihara, Hideki [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Soda, Jiro [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan)

2007-09-15

145

Curled encodes the Drosophila homolog of the vertebrate circadian deadenylase Nocturnin.  

PubMed

Drosophila melanogaster curled, one of the first fly mutants described by T. H. Morgan >90 years ago, is the founding member of a series of curled wing phenotype mutants widely used as markers in fruit fly genetics. The expressivity of the wing phenotype is environmentally modulated, suggesting that the mutation affects the metabolic status of cells rather than a developmental control gene. However, the molecular identity of any of the curled wing marker mutant genes is still unknown. In a screen for starvation-responsive genes, we previously identified the single fly homolog of the vertebrate nocturnin genes, which encode cytoplasmic deadenylases that act in the post-transcriptional control of genes by poly(A) tail removal of target mRNAs prior to their degradation. Here we show that curled encodes Drosophila Nocturnin and that the gene is required at pupal stage for proper wing morphogenesis after eclosion of the fly. Despite the complex ontogenetic expression pattern of the gene, curled is not expressed in the developing wing, and wing-specific curled knockdown mediated by RNAi does not result in the curled wing phenotype, indicating a tissue-nonautonomous, systemic mode of curled gene function. Our study not only presents an entry point into the functional analysis of invertebrate nocturnins but also paves the way for the identification of the still elusive Nocturnin target mRNAs by genetic suppressor screens on the curled wing phenotype. PMID:19581445

Grönke, Sebastian; Bickmeyer, Iris; Wunderlich, Roman; Jäckle, Herbert; Kühnlein, Ronald P

2009-09-01

146

Plastic Mulches and Row Covers on Growth and Production of Summer Squash  

Microsoft Academic Search

Row covers and colored plastic mulch are used routinely throughout the United States to grow vegetables but are rarely used in conjunction to produce a crop. Summer squash (Cucurbita pepo L.), cv. Prelude II, was grown on an Orangeburg sandy loam soil in Shorter, AL. The summer squash was direct seeded in single rows. The experiment consisted of 12 treatments

Garry G. Gordon; Wheeler G. Foshee III; Stewart T. Reed; James E. Brown; Edgar Vinson; Floyd M. Woods

2008-01-01

147

Effect of the shoulder position on the biceps brachii emg in different dumbbell curls.  

PubMed

Incline Dumbbell Curl (IDC) and Dumbbell Preacher Curl (DPC) are two variations of the standard Dumbbell Biceps Curl (DBC), generally applied to optimize biceps brachii contribution for elbow flexion by fixing shoulder at a specific angle. The aim of this study is to identify changes in the neuromuscular activity of biceps brachii long head for IDC, DPC and DBC exercises, by taking into account the changes in load moment arm and muscle length elicited by each dumbbell curl protocol. A single cycle (concentric-eccentric) of DBC, IDC and DPC, was applied to 22 subjects using a submaximal load of 40% estimated from an isometric MVC test. The neuromuscular activity of biceps brachii long head was compared by further partitioning each contraction into three phases, according to individual elbow joint range of motion. Although all protocols elicited a considerable level of activation of the biceps brachii muscle (at least 50% of maximum RMS), the contribution of this muscle for elbow flexion/extension varied among exercises. The submaximal elbow flexion (concentric) elicited neuro muscular activity up to 95% of the maximum RMS value during the final phase of IDC and DBC and 80% for DPC at the beginning of the movement. All exercises showed significant less muscle activity for the elbow extension (eccentric). The Incline Dumbbell Curl and the classical Dumbbell Biceps Curl resulted in similar patterns of biceps brachii activation for the whole range of motion, whereas Dumbbell Preacher Curl elicited high muscle activation only for a short range of elbow joint angle. Key pointsThe Incline Dumbbell Curl and the Dumbbell Biceps Curl resulted in a considerable neuromuscular effort throughout the whole elbow range of motion.The Incline Dumbbell Curl and the Dumbbell Biceps Curl may be preferable for the improvement of biceps brachii force in training programs. PMID:24150552

Oliveira, Liliam F; Matta, Thiago T; Alves, Daniel S; Garcia, Marco A C; Vieira, Taian M M

2009-01-01

148

Effect of the shoulder position on the biceps brachii emg in different dumbbell curls  

PubMed Central

Incline Dumbbell Curl (IDC) and Dumbbell Preacher Curl (DPC) are two variations of the standard Dumbbell Biceps Curl (DBC), generally applied to optimize biceps brachii contribution for elbow flexion by fixing shoulder at a specific angle. The aim of this study is to identify changes in the neuromuscular activity of biceps brachii long head for IDC, DPC and DBC exercises, by taking into account the changes in load moment arm and muscle length elicited by each dumbbell curl protocol. A single cycle (concentric-eccentric) of DBC, IDC and DPC, was applied to 22 subjects using a submaximal load of 40% estimated from an isometric MVC test. The neuromuscular activity of biceps brachii long head was compared by further partitioning each contraction into three phases, according to individual elbow joint range of motion. Although all protocols elicited a considerable level of activation of the biceps brachii muscle (at least 50% of maximum RMS), the contribution of this muscle for elbow flexion/extension varied among exercises. The submaximal elbow flexion (concentric) elicited neuro muscular activity up to 95% of the maximum RMS value during the final phase of IDC and DBC and 80% for DPC at the beginning of the movement. All exercises showed significant less muscle activity for the elbow extension (eccentric). The Incline Dumbbell Curl and the classical Dumbbell Biceps Curl resulted in similar patterns of biceps brachii activation for the whole range of motion, whereas Dumbbell Preacher Curl elicited high muscle activation only for a short range of elbow joint angle. Key pointsThe Incline Dumbbell Curl and the Dumbbell Biceps Curl resulted in a considerable neuromuscular effort throughout the whole elbow range of motion.The Incline Dumbbell Curl and the Dumbbell Biceps Curl may be preferable for the improvement of biceps brachii force in training programs. PMID:24150552

Oliveira, Liliam F.; Matta, Thiago T.; Alves, Daniel S.; Garcia, Marco A.C.; Vieira, Taian M.M.

2009-01-01

149

Curling edges: a problem that has plagued scrolls for millennia.  

PubMed

Qi-Wa refers to the up curl on the lengths of hand scrolls and hanging scrolls, which has troubled Chinese artisans and emperors for as long as the art of painting and calligraphy has existed. This warp is unwelcome not only for aesthetic reasons, but its potential damage to the fiber and ink. Although it is generally treated as a part of the cockling and curling due to moisture, consistency of paste, and defects from the mounting procedures, we demonstrate that the spontaneous extrinsic curvature incurred from the storage is in fact more essential to understanding and curing Qi-Wa. In contrast to the former factors whose effects are less predictable, the plastic deformation and strain distribution on a membrane are a well-defined mechanical problem. We study this phenomenon by experiments, theoretical models, and molecular dynamics simulation, and obtain consistent scaling relations for the Qi-Wa height. This knowledge enables us to propose modifications on the traditional mounting techniques that are tested on real mounted paper to be effective at mitigating Qi-Wa. By experimenting on polymer-based films, we demonstrate the possible relevance of our study to the modern development of flexible electronic paper. PMID:24484142

Chou, Ming-Han; Shen, Wei-Chao; Wang, Yi-Ping; Hung, Sun-Hsin; Hong, Tzay-Ming

2014-01-24

150

Curling Edges: A Problem that Has Plagued Scrolls for Millennia  

NASA Astrophysics Data System (ADS)

Qi-Wa refers to the up curl on the lengths of hand scrolls and hanging scrolls, which has troubled Chinese artisans and emperors for as long as the art of painting and calligraphy has existed. This warp is unwelcome not only for aesthetic reasons, but its potential damage to the fiber and ink. Although it is generally treated as a part of the cockling and curling due to moisture, consistency of paste, and defects from the mounting procedures, we demonstrate that the spontaneous extrinsic curvature incurred from the storage is in fact more essential to understanding and curing Qi-Wa. In contrast to the former factors whose effects are less predictable, the plastic deformation and strain distribution on a membrane are a well-defined mechanical problem. We study this phenomenon by experiments, theoretical models, and molecular dynamics simulation, and obtain consistent scaling relations for the Qi-Wa height. This knowledge enables us to propose modifications on the traditional mounting techniques that are tested on real mounted paper to be effective at mitigating Qi-Wa. By experimenting on polymer-based films, we demonstrate the possible relevance of our study to the modern development of flexible electronic paper.

Chou, Ming-Han; Shen, Wei-Chao; Wang, Yi-Ping; Hung, Sun-Hsin; Hong, Tzay-Ming

2014-01-01

151

Out with the Sit-Up, in with the Curl-Up!  

ERIC Educational Resources Information Center

Explains why physical education teachers should discourage full sit-ups and describes the Robertson Modified Curl-Up Test as a recommended alternative test of abdominal muscular strength. Curl-up test administration guidelines are included with some preliminary norms from adult groups. (SM)

MacFarlane, Pamela A.

1993-01-01

152

Curled actuated shapes of ionic polymer metal composites strips  

NASA Astrophysics Data System (ADS)

The curled actuated shapes of ionic polymer metal composites (IPMCs) are described within a nonlinear physics-based model of IPMC actuators. A key characteristic of the model is the refined, even if black box based, modeling of the relative permittivity of the IPMCs which strongly influences the actuation performances of the IPMC, when voltages higher than 1 V are involved. A varying-along-the-thickness relative permittivity is proposed to take into account the highly heterogeneous layers resulting from electrode deposition, where a charge redistribution occurs. Moreover, the presence of the metal electrodes has been considered as hampering the IPMCs' bending deformations, so reducing the actuation performances of the IPMC. A series of numerical tests have been planned and discussed to show the characteristics of the model; in particular, the model is shown to be strong enough to catch the not monotonic behavior of IPMCs, when back relaxation is manifested.

Nardinocchi, Paola; Pezzulla, Matteo

2013-06-01

153

Occurrence of Squash yellow mild mottle virus and Pepper golden mosaic virus in Potential New Hosts in Costa Rica  

PubMed Central

Leaf samples of Solanum lycopersicum, Capsicum annuum, Cucurbita moschata, Cucurbita pepo, Sechium edule and Erythrina spp. were collected. All samples were positive for begomoviruses using polymerase chain reaction and degenerate primers. A sequence of ?1,100 bp was obtained from the genomic component DNA-A of 14 samples. In addition, one sequence of ?580 bp corresponding to the coat protein (AV1) was obtained from a chayote (S. edule) leaf sample. The presence of Squash yellow mild mottle virus (SYMMoV) and Pepper golden mosaic virus (PepGMV) were confirmed. The host range reported for SYMMoV includes species of the Cucurbitaceae, Caricaceae and Fabaceae families. This report extends the host range of SYMMoV to include the Solanaceae family, and extends the host range of PepGMV to include C. moschata, C. pepo and the Fabaceae Erythrina spp. This is the first report of a begomovirus (PepGMV) infecting chayote in the Western Hemisphere. PMID:25288955

Castro, Ruth M.; Moreira, Lisela; Rojas, Maria R.; Gilbertson, Robert L.; Hernandez, Eduardo; Mora, Floribeth; Ramirez, Pilar

2013-01-01

154

Preparation of Drosophila Polytene Chromosome Squashes for Antibody Labeling  

PubMed Central

Drosophila has long been a favorite model system for studying the relationship between chromatin structure and gene regulation due to the cytological advantages provided by the giant salivary gland polytene chromosomes of third instar larvae. In this tissue the chromosomes undergo many rounds of replication in the absence of cell division giving rise to approximately 1000 copies. The DNA remains aligned after each replicative cycle resulting in greatly enlarged chromosomes that provide a unique opportunity to correlate chromatin morphology with the localization of specific proteins. Consequently, there has been a high level of interest in defining the epigenetic modifications present at different genes and at different stages of the transcription process. An important tool for such studies is the labeling of polytene chromosomes with antibodies to the enzyme, transcription factor, or histone modification of interest. This video protocol illustrates the squash technique used in the Johansen laboratory to prepare Drosophila polytene chromosomes for antibody labeling. PMID:20145604

Cai, Weili; Jin, Ye; Girton, Jack; Johansen, Jorgen; Johansen, Kristen M.

2010-01-01

155

Bees visiting squash (Cucurbita moschata Duchesne ex Poiret) in southwestern Colombia (Hymenoptera: Apoidea)  

E-print Network

This note records for the first time 12 bee species belonging to eight genera of Apidae and Halictidae as visitors of cultivated squash (Cucurbita moschata Duchesne ex Poiret: Cucurbitaceae) in the municipality of El Patía, Department of Cauca...

Zambrano-G, Giselle; Gonzalez, Victor H.; Hinojosa-Diaz, Ismael A.; Engel, Michael S.

2013-10-07

156

SHAPESET: A process to reduce sidewall curl springback in high-strength steel rails  

Microsoft Academic Search

High-strength steel rails for structural members can reduce vehicle weight, but sidewall curl springback in these rails causes\\u000a assembly difficulties with adjacent parts. A process to greatly reduce curl springback, known as SHAPESET, was investigated\\u000a for a variety of high-strength steels, including two dual-phase steels. Gridded blanks were stamped by the two-step SHAPESET\\u000a process and by conventional methods. The SHAPESET

R. A. Ayres

1984-01-01

157

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.

2008-09-12

158

Self reported injury patterns among competitive curlers in the United States: a preliminary investigation into the epidemiology of curling injuries  

PubMed Central

Methods: Participants at two curling championship events were asked to complete injury history questionnaires. Results: 76 curlers (39%) participated; 79% of these reported curling related musculoskeletal pain, most commonly involving the knee (54%), back (33%), and shoulder (20%). Sweeping and delivering the stone were most likely to provoke symptoms. Time loss injuries were estimated to occur at a rate of 2 per 1000 athlete exposures. Conclusions: Curling appears to be a relatively safe winter sport. Prospective studies are needed to confirm these preliminary findings and to further define the risk factors for curling related injuries. PMID:15388573

Reeser, J; Berg, R

2004-01-01

159

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

160

Leaf development.  

PubMed

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

Tsukaya, Hirokazu

2013-01-01

161

Cytologic features of the normal pineal gland on squash preparations.  

PubMed

As primary pineal lesions are extremely rare, many surgical pathologists are unfamiliar with normal pineal cytologic features. We describe cytologic features of the normal pineal gland in patients of varying ages and identify common diagnostic pitfalls. We performed a retrospective review of pineal gland biopsies performed at our institution, where approximately 30,000 surgical specimens are accessioned yearly, for the last 23 years. Only two pineal gland biopsies were found. Although both cases were initially diagnosed as low-grade gliomas on frozen section, the final diagnosis was benign pineal tissue based on light microscopy and immunohistochemistry results. Additionally, we performed squash preparations of five normal pineal gland autopsy specimens with Papanicolaou and Diff-Quik® (Dade Behring, Newark, DE) stains. Infant preparations were highly cellular smears composed of numerous, uniform, single cells with indistinct cytoplasm, small round-to-oval nuclei, fine chromatin, and absent nucleoli and calcifications. The vague microfollicular pattern mimicked a pineocytoma and the fine fibrillary background mimicked a glial neoplasm. Young adult smears were similar; however, microcalcifications were present with fewer background single cells. Older patients had much less cellular smears composed of small clusters of cells with fusiform-to-spindle nuclei, a fine chromatin pattern, and indistinct cytoplasmic borders. There were fewer background single cells and more microcalcifications. The cytologic features of the native pineal gland vary with age. Normal pineal tissue can be confused with a pineocytoma or low-grade glioma. Familiarity with normal pineal gland cytological features will help to avoid a potential misdiagnosis. Diagn. Cytopathol. 2014;42:939-943. © 2014 Wiley Periodicals, Inc. PMID:24692343

Murro, Diana; Alsadi, Alaa; Nag, Sukriti; Arvanitis, Leonidas; Gattuso, Paolo

2014-11-01

162

Gourd and squash artifacts yield starch grains of feasting foods from preceramic Peru  

PubMed Central

In a study of residues from gourd and squash artifacts, we recovered starch grains from manioc (Manihot esculenta), potato (Solanum sp.), chili pepper (Capsicum spp.), arrowroot (Maranta arundinacea), and algarrobo (Prosopis sp.) from feasting contexts at the Buena Vista site, a central Peruvian preceramic site dating to ?2200 calendar years B.C. This study has implications for the study of plant food use wherever gourds or squashes are preserved, documents the earliest evidence for the consumption of algarrobo and arrowroot in Peru, and provides insights into foods consumed at feasts. PMID:19633184

Duncan, Neil A.; Pearsall, Deborah M.; Benfer, Robert A.

2009-01-01

163

Gourd and squash artifacts yield starch grains of feasting foods from preceramic Peru.  

PubMed

In a study of residues from gourd and squash artifacts, we recovered starch grains from manioc (Manihot esculenta), potato (Solanum sp.), chili pepper (Capsicum spp.), arrowroot (Maranta arundinacea), and algarrobo (Prosopis sp.) from feasting contexts at the Buena Vista site, a central Peruvian preceramic site dating to approximately 2200 calendar years B.C. This study has implications for the study of plant food use wherever gourds or squashes are preserved, documents the earliest evidence for the consumption of algarrobo and arrowroot in Peru, and provides insights into foods consumed at feasts. PMID:19633184

Duncan, Neil A; Pearsall, Deborah M; Benfer, Robert A

2009-08-11

164

Specificity and Photomorphogenic Nature of Ultraviolet-B-Induced Cotyledon Curling in Brassica napus L.  

PubMed Central

Three general classes of photomorphogenic photoreceptors have been characterized in higher plants: phytochrome, a blue light/ultraviolet (UV)-A photoreceptor(s), and a UV-B sensory system(s). Although a great deal is known about phytochrome and the blue light/UV-A photoreceptor(s), little is known about UV-B detection processes. One reason for this is the lack of readily quantifiable morphogenic responses that are specifically induced by UV-B radiation. We have discovered a response to UV-B, upward curling of Brassica napus L. cotyledons, that may be useful for probing the mechanism of UV-B photoreception. The process was initially observed when B. napus seeds were germinated under visible light plus UV-B radiation, but did not occur under visible light alone or visible light plus UV-A. When 5-d-old seedlings grown in visible light were given relatively short exposures of UV-B (100 min of 5.5 [mu]mol m-2 s-1), the curling response was also observed. Development of curling was separated from the application of this UV-B pulse by a 14-h latent period. Pulses of red light, blue light, farred light, and UV-A (100 min of 5.5 [mu]mol m-2 s-1) did not induce curling, indicating UV-B specificity Additionally, these other spectral regions did not reverse or enhance the UV-B-triggered response. The degree of curling showed a log-linear dependence on UV-B fluence (6-40 mmol m-2) and reciprocity with respect to length of exposure and fluence rate. The data indicate that curling is photomorphogenic in nature and may be triggered by a single photoreceptor species. PMID:12231857

Wilson, M. I.; Greenberg, B. M.

1993-01-01

165

Effects of fertilizer type and rate, and liming on banana squash yield  

Microsoft Academic Search

There is a question whether it is best to use synthetic or alternative materials to fertilize horticultural crops. Levels of applied fertilizer can affect development of crops such as banana squash (Curcubita maxima Duch.). Seed were planted in 1990, 1991, and 1992 into beds treated with sufficient fertilizer to raise the residual nutrient levels to the recommended (base) and twice

V. M. Russo

1993-01-01

166

Occurrence and epidemiology of a potyvirus?like disease of zucchini squash in Nepal  

Microsoft Academic Search

Field incidence of a virus disease of zucchini squash causing severe mosaic, vein banding, shoe stringing, distortion of leaves and fruits with occasional blisters was monitored during 1988–1990 at 12 locations in four districts of Nepal. The causal agent was transmitted by sap and aphids but was not seed?borne. Electron microscopic observation of samples collected from infected plants revealed flexuous

G. Dahal

1992-01-01

167

Diel nectar secretion rhythm in squash (Cucurbita pepo) and its relation with pollinator activity  

E-print Network

Diel nectar secretion rhythm in squash (Cucurbita pepo) and its relation with pollinator activity as simulated drought conditions in the greenhouse. In the presence of active pollinators, diel patterns for pollinator behavior are discussed. bees / foraging / nectar / pollinators / behavior 1. INTRODUCTION

168

Tennis-Badminton-Squash Guide with Official Rules. June 1972 - June 1974.  

ERIC Educational Resources Information Center

Rules in tennis, badminton, and squash for girls and women from June 1972 - June 1974 are discussed. Standards in the sports are detailed along with the Division for Girls and Women's Sports (DGWS) statement of beliefs. Specific articles dealing with teaching techniques, officiating techniques, and rules for tennis and badminton are presented.…

Knight, Martha, Ed.; And Others

169

4th Order Diffusion Tensor Interpolation with Divergence and Curl Constrained Bezier Patches  

Microsoft Academic Search

We present a tensor field interpolation method based on tensor-valued Bezier patches. The control points of the patch are determined by imposing physical constraints on the interpolated field by constraining the divergence and curl of the tensor field. The method generalizes to Cartesian tensors of all orders. Solving for the control points requires the solution of a sparse linear system.

Inas Yassine; Tim McGraw

2009-01-01

170

Horizontal and residual circulations driven by wind stress curl in Tokyo Bay  

NASA Astrophysics Data System (ADS)

study investigates the horizontal and residual circulations in Tokyo Bay using field observations, numerical simulations, and theoretical analysis. Numerical simulations show that the observed deepening of isopycnals and associated anticyclonic horizontal circulation in the bay head are mainly driven by negative wind stress curl. The effects of river discharge, surface heat fluxes, and tides are found to be small. Under strong wind events, the wind stress curl over the bay head can be large enough to make the surface Ekman layer strongly nonlinear. Theoretical and numerical analyses show that, under large negative wind stress curl, the nonlinearity tends to induce positive pumping velocity (at the base of the surface mixed layer) that counteracts the Ekman pumping; however, the typical duration of wind events in the bay head is not long enough to induce positive pumping under negative wind stress curl. These results and historical wind data suggest that the average horizontal circulation and residual circulation immediately below the surface mixed layer in Tokyo Bay are, respectively, cyclonic and convergent in summer but anticyclonic and divergent in winter.

Nakayama, K.; Shintani, T.; Shimizu, K.; Okada, T.; Hinata, H.; Komai, K.

2014-03-01

171

Curl condition for a four-state Born-Oppenheimer system employing the Mathieu equation.  

PubMed

When a group of four states forms a subspace of the Hilbert space, i.e., appears to be strongly coupled with each other but very weakly interacts with all other states of the entire space, it is possible to express the nonadiabatic coupling (NAC) elements either in terms of s or in terms of electronic basis function angles, namely, mixing angles presumably representing the same sub-Hilbert space. We demonstrate that those explicit forms of the NAC terms satisfy the curl conditions--the necessary requirements to ensure the adiabatic-diabatic transformation in order to remove the NAC terms (could be often singular also at specific point(s) or along a seam in the configuration space) in the adiabatic representation of nuclear SE and to obtain the diabatic one with smooth functional form of coupling terms among the electronic states. In order to formulate extended Born-Oppenheimer (EBO) equations [J. Chem. Phys. 2006, 124, 074101] for a group of four states, we show that there should exist a coordinate independent ratio of the gradients for each pair of ADT/mixing angles leading to zero curls and, thereafter, provide a brief discussion on its analytical validity. As a numerical justification, we consider the first four eigenfunctions of the Mathieu equation to demonstrate the interesting features of nonadiabatic coupling (NAC) elements, namely, the validity of curl conditions and the nature of curl equations around CIs. PMID:18785688

Sarkar, Biplab; Adhikari, Satrajit

2008-10-01

172

Wind Stress Curl and ENSO Discharge\\/Recharge in the Equatorial Pacific  

Microsoft Academic Search

Discharge and recharge of the warm water volume (WWV) above the 20°C isotherm in an equatorial Pacific Ocean box extending across the Pacific from 156°E to the eastern ocean boundary between latitudes 5°S and 5°N are key variables in ENSO dynamics. A formula linking WWV anomalies, zonally integrated wind stress curl anomalies along the northern and southern edges of the

Allan J. Clarke; Stephen Van Gorder; Giuseppe Colantuono

2007-01-01

173

FRACTIONAL CURL OPERATOR IN CHIRAL MEDIUM AND FRACTIONAL NON-SYMMETRIC TRANSMISSION LINE  

Microsoft Academic Search

Abstract—Fractional curl operator has,been utilized to wave propagation in lossless, isotropic, homogeneous and reciprocal chiral medium,when it contains interfaces. The fractional solutions for the corresponding standing wave solution and transverse impedance are determined. Equivalent fractional non-symmetric transmission line has also been analyzed.

Akhtar Hussain; Qaisar A. Naqvi

2006-01-01

174

CURL: A Searchable CUrricular Resources Library of Earth and Environmental Science Websites  

NASA Astrophysics Data System (ADS)

A searchable web-based Curricular Resources Library (CURL) has been developed by earth and environmental science faculty from four New England schools (Dartmouth College, Connecticut College, Trinity College, and Wesleyan University) in conjunction with Wesleyan's Information Technology Services (ITS) and librarians. The site (http://www.wesleyan.edu/curl/) provides access to pre-selected earth and environmental science material. CURL sites are identified by faculty who provide information about the site in the following nine fields: Annotation (description), Discipline, Keywords, Origin of Site, Reason for Submission, Submitted By, URL, URL Title, URL Type. Subject Headings conform to those developed by the Library of Congress. These are determined by the Wesleyan University science librarian who enters them into the database. The Curl database can be searched three ways: 1) Browsing alphabetically by Subject Heading (e.g. remote sensing but not satellite pictures), 2) Keyword search which will look for an exact match of a term in any of the designated fields (e.g. URL type, origin of site, discipline), and 3) Advanced search, which allows you to combine terms from any of ten different fields in a single search. Results are displayed in alphabetical order and include the URL title, the URL, and a brief annotation that describes the website. There is an active link to the URL. A web link checker accesses sites to identify broken links. After several unsuccessful attempts, the submitter is contacted and asked to update or delete the site. Between 200 and 250 earth and environmental sites are presently catalogued through CURL. This format could be used by any academic discipline and future plans allow for web resources to span collections.

O'Connell, S.; O'Connell, S.; Klassen, T.; Roy, M.; Glynn, M.

2001-05-01

175

[Effects of shading on squash seedlings' morphological and photosynthetic physiological characteristics].  

PubMed

The study of squash seedlings' morphological and photosynthetic physiological characteristics under different shading showed that under 60% light transmittance, their relative growth rate, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (EVAP), water use efficiency (WUE), saturation steam pressure (MBR), apparent quantum yield of photosynthesis (AQY), and chlorophyll contents were higher, while the intercellular CO2 concentration (Ci) was lower, compared with those under 20% light transmittance and CK. The seedlings under 60% light transmittance had a higher light saturation point (1 125 micromol x m(-2) x s(-1)) but a lower light compensation point (15.2 micromol x m(-2) s(-1)). Squash seedlings under lower light intensity could endure lower concentration of CO2, while those under higher light intensity could endure higher concentration of CO2. Under 60% light transmittance, the malondialdehyde (MDA) and praline (Pro) contents were the lowest, while the peroxidase (POD) and catalase (CAT) activities were the highest. PMID:16836096

Qin, Shuhao; Li, Lingling

2006-04-01

176

A deformation of quantum affine algebra in squashed Wess-Zumino-Novikov-Witten models  

NASA Astrophysics Data System (ADS)

We proceed to study infinite-dimensional symmetries in two-dimensional squashed Wess-Zumino-Novikov-Witten models at the classical level. The target space is given by squashed S3 and the isometry is SU(2)L × U(1)R. It is known that SU(2)L is enhanced to a couple of Yangians. We reveal here that an infinite-dimensional extension of U(1)R is a deformation of quantum affine algebra, where a new deformation parameter is provided with the coefficient of the Wess-Zumino term. Then we consider the relation between the deformed quantum affine algebra and the pair of Yangians from the viewpoint of the left-right duality of monodromy matrices. The integrable structure is also discussed by computing the r/s-matrices that satisfy the extended classical Yang-Baxter equation. Finally, two degenerate limits are discussed.

Kawaguchi, Io; Yoshida, Kentaroh

2014-06-01

177

POLYTENE CHROMOSOME SQUASH METHODS FOR STUDYING TRANSCRIPTION AND EPIGENETIC CHROMATIN MODIFICATION IN DROSOPHILA USING ANTIBODIES  

PubMed Central

The giant polytene chromosomes from Drosophila third instar larval salivary glands provide an important model system for studying the architectural changes in chromatin morphology associated with the process of transcription initiation and elongation. Especially, analysis of the heat shock response has proved useful in correlating chromatin structure remodeling with transcriptional activity. An important tool for such studies is the labeling of polytene chromosome squash preparations with antibodies to the enzymes, transcription factors, or histone modifications of interest. However, in any immunohistochemical experiment there will be advantages and disadvantages to different methods of fixation and sample preparation, the relative merits of which must be balanced. Here we provide detailed protocols for polytene chromosome squash preparation and discuss their relative pros and cons in terms of suitability for reliable antibody labeling and preservation of high resolution chromatin structure. PMID:19272452

Johansen, Kristen M.; Cai, Weili; Deng, Huai; Bao, Xiaomin; Zhang, Weiguo; Girton, Jack; Johansen, J?rgen

2009-01-01

178

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

179

Suppression of powdery mildew in squash by applications of whitewash, clay and antitranspirant materials  

Microsoft Academic Search

The incidence of powdery mildew, caused bySphaerotheca fuliginea (Schlecht. Fr.) Polacci, in squash plants, was suppressed in the field to 50–60% of that in untreated control plants by weekly\\u000a sprays with whitewash (Loven or Yalbin) or clay. Loven or Yalbin sprays resulted in significant reductions in disease level,\\u000a more on the adaxial (59–65%) than on the abaxial (38–52%) surface of

S. Marco; O. Ziv; R. Cohen

1994-01-01

180

Gravity Dual of Supersymmetric Gauge Theories on a Squashed Five-Sphere  

NASA Astrophysics Data System (ADS)

We present the gravity dual of large N supersymmetric gauge theories on a squashed five-sphere. The one-parameter family of solutions is constructed in Euclidean Romans F(4) gauged supergravity in six dimensions, and uplifts to massive type IIA supergravity. By renormalizing the theory with appropriate counterterms we evaluate the renormalized on-shell action for the solutions. We also evaluate the large N limit of the gauge theory partition function, and find precise agreement.

Alday, Luis F.; Fluder, Martin; Richmond, Paul; Sparks, James

2014-10-01

181

The effects of carbohydrate loading 48 hours before a simulated squash match.  

PubMed

The aim of this study was to ascertain whether a high carbohydrate diet in the days before movement patterns simulating a squash match would increase carbohydrate oxidation during the match, and alter physical performance. Nine New Zealand level squash players were recruited to complete a simulated squash match on two occasions: 1) following a 48-hr high carbohydrate (11.1g·kg-1); and 2) following a calorie-matched low carbohydrate (2.1 g·kg-1) diet. The interventions were assigned in a randomized, single-blind, cross-over design. The match simulation was designed to mimic a five-game match lasting approximately 1 hr. Performance was measured as time to complete each game. Expired respiratory gases and heart rate were continuously collected throughout the trial using a portable gas analysis system. Capillary blood glucose and lactate samples were obtained during a 90 s rest period between each game. Rating of perceived exertion was also recorded after each set. Respiratory exchange ratio was significantly higher during exercise following the high CHO diet (0.80 vs. 0.76) p < .001) and this was associated with significantly faster time to complete the games (2340 ± 189 s vs. 2416 ± 128 s, p = .036). Blood glucose and lactate concentrations were also significantly higher in the high carbohydrate condition (p = .038 and p = .021 respectively). These results suggest that ingestion of a diet high in carbohydrate (>10 g/kg body weight) preceding simulated competitive squash produces increased rates of carbohydrate oxidation and maintains higher blood glucose concentrations. These metabolic effects were associated with improved physical performance. PMID:24092769

Raman, Aaron; Macdermid, Paul W; Mündel, Toby; Mann, Michael; Stannard, Stephen R

2014-04-01

182

On Instability of Squashed Spheres in the Kaluza-Klein Theory  

E-print Network

We study in Kaluza-Klein theories stability of the extra space against "squashing", in other words, the homogeneous deformation. Quantum fluctuations of matter fields at one-loop level are taken into consideration. We calculate the effective potential in models of the type, $M^4\\times S^3$ and $M^4\\times S^7$. It is found that in the case of scalar matter fields the stability depends on the coupling to the scalar curvature.

Kiyoshi Shiraishi

2014-06-20

183

EE2 Mathematics The role of grad, div and curl in vector calculus  

E-print Network

EE2 Mathematics The role of grad, div and curl in vector calculus The gradient operator is defined of grad = = ^i x + ^j y + ^k z . Note that is a vector. Since is a vector operator it can act upon a vector field A(x, y, z) = ^i A1(x, y, z) + ^j A2(x, y, z) + ^k A3(x, y, z) through the dot product

Gibbon, J. D.

184

Three dimensional musculoskeletal modelling of the seated biceps curl resistance training exercise  

Microsoft Academic Search

The aim of this study was to evaluate the benefits and limitations of using three dimensional (3D) musculoskeletal modelling (LifeModeler™) in assessing the safety and efficacy of exercising on a seated biceps curl resistance training machine. Three anthropometric cases were studied, representing a 5 percentile female, 50 percentile and 95 percentile male. Results indicated that the LifeModeler™ default model was

Kim Nolte; Pieter E. Krüger; P. Schalk Els

2011-01-01

185

Curling up two spatial dimensions with SU(1,1)\\/U(1)  

Microsoft Academic Search

It is seen that a nonlinear sigma model based on the noncompact coset space SU(1,1)\\/U(1) can curl up two spatial dimensions into a topologically noncompact surface of finite area with a compact U(1) isometry group. This mechanism can be used for several higher-dimensional supergravity theories. In particular, chiral N = 2, D = 10 supergravity would reduce to an N

Murray Gell-Mann; Barton Zwiebach

1984-01-01

186

Fabrication of curled conducting polymer microfibrous arrays via a novel electrospinning method for stretchable strain sensors  

NASA Astrophysics Data System (ADS)

Stretchable strain sensors based on aligned microfibrous arrays of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-poly(vinyl pyrrolidone) (PEDOT:PSS-PVP) with curled architectures have been fabricated by a novel reciprocating-type electrospinning setup with a spinneret in straightforward simple harmonic motion. The incorporation of PEDOT:PSS into PVP is confirmed by Raman spectra, which improves the room-temperature conductivity of the composite fibers (1.6 × 10-5 S cm-1). Owing to the curled architectures of the as-spun fibrous polymer arrays, the sensors can be stretched reversibly with a linear elastic response to strain up to 4%, which is three times higher than that from electrospun nonwoven mats. In addition, the stretchable strain sensor with a high repeatability and durability has a gauge factor of about 360. These results may be helpful for the fabrication of stretchable devices which have potential applications in some fields such as soft robotics, elastic semiconductors, and elastic solar cells.Stretchable strain sensors based on aligned microfibrous arrays of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-poly(vinyl pyrrolidone) (PEDOT:PSS-PVP) with curled architectures have been fabricated by a novel reciprocating-type electrospinning setup with a spinneret in straightforward simple harmonic motion. The incorporation of PEDOT:PSS into PVP is confirmed by Raman spectra, which improves the room-temperature conductivity of the composite fibers (1.6 × 10-5 S cm-1). Owing to the curled architectures of the as-spun fibrous polymer arrays, the sensors can be stretched reversibly with a linear elastic response to strain up to 4%, which is three times higher than that from electrospun nonwoven mats. In addition, the stretchable strain sensor with a high repeatability and durability has a gauge factor of about 360. These results may be helpful for the fabrication of stretchable devices which have potential applications in some fields such as soft robotics, elastic semiconductors, and elastic solar cells. Electronic supplementary information (ESI) available: The movie of stretchability of an individual PEDOT:PSS-PVP microfiber with a curled structure. See DOI: 10.1039/c3nr01832f

Sun, Bin; Long, Yun-Ze; Liu, Shu-Liang; Huang, Yuan-Yuan; Ma, Jie; Zhang, Hong-Di; Shen, Guozhen; Xu, Sheng

2013-07-01

187

Buttercup squash provides a marketable alternative to blue hubbard as a trap crop for control of striped cucumber beetles (Coleoptera: Chrysomelidae).  

PubMed

Winter squash is a vital agricultural commodity worldwide. In the Northeastern United States, the primary insect pest is the striped cucumber beetle, Acalymma vittatum F. Using a Blue Hubbard squash (Cucurbita maxima Duchesne) perimeter trap crop system can reduce insecticide use by >90% in butternut squash (C. moschata Poir), the primary winter squash grown in this region. Despite the savings in insecticide costs, growers may be reluctant to give up field space for a perimeter crop of Blue Hubbard squash, which comprises only 5% of the winter squash market in New England as compared with 19% for buttercup squash. Finding a more marketable trap crop would lower the barrier for adoption of this system. We tested eight varieties of three species of cucurbits for attractiveness to beetles relative to Blue Hubbard and butternut squash, and chose buttercup squash as the most promising replacement. We compared the effect of a buttercup border, Blue Hubbard border, or control (no border) on beetle numbers, herbivory, insecticide use, pollination, and pollen limitation in the main crop. We found that buttercup squash performed equally well as Blue Hubbard as a trap crop, with 97% reduction in total insecticide use compared with control fields. Honey bees (Apis mellifera L.) and squash bees (Peponapis pruinosa Say) were the predominant pollinators, and border treatments did not affect visitation. Hand pollination did not increase reproduction or yield, indicating that natural pollination was sufficient for full yield. This study confirms the effectiveness of perimeter trap crop systems and offers growers a more marketable trap crop for managing cucumber beetle damage. PMID:22182562

Cavanagh, Andrew F; Adler, Lynn S; Hazzard, Ruth V

2010-12-01

188

Abdominal and hip flexor muscle activity during 2 minutes of sit-ups and curl-ups.  

PubMed

Previous studies have compared muscle activity between different types of sit-ups and curl-ups. However, few have examined the exercises used by the armed forces or investigated the influence of exercise duration on muscle activation. The aim of this study was to compare abdominal and hip flexor muscle activity between the style of sit-up used by the British Army and 4 variations of a curl-up, at the start, middle, and end of a 2-minute exercise period. Surface electromyograms (EMGs) were recorded from the upper and lower rectus abdominis, external oblique, transversus abdominis and internal oblique, and the rectus femoris (RF) of 23 British Army personnel. Isometric maximal voluntary contractions were used to normalize integrated EMGs to allow them to be compared between exercises. Curl-ups with arms crossed and feet restrained produced the highest integrated EMG in all the abdominal muscles (p < 0.05). Feet-restrained sit-ups and curl-ups also resulted in significantly higher activity in the RF than in nonrestrained versions of the curl-up (p < 0.001). The significant increase observed in muscle activity between the start and the end of the exercises (p < 0.001) was deemed to be in response to a reduction in force producing capacity of existing motor units. The RF experienced the greatest increase during exercises that activated the muscle the most, that is, sit-ups and curl-ups with feet restrained (p < 0.001). Previous research has indicated that such exercises produce high shear and compressive forces in the lower back, which can be injurious. Thus, if an organization wishes to assess the endurance of abdominal muscles, rather than hip flexors, then curl-ups without restraint of the feet should be performed instead of exercises in which the feet are restrained. PMID:23207881

Burden, Adrian M; Redmond, Colin G

2013-08-01

189

Antidiabetic II drug metformin in plants: uptake and translocation to edible parts of cereals, oily seeds, beans, tomato, squash, carrots, and potatoes.  

PubMed

Residues of pharmaceuticals present in wastewater and sewage sludge are of concern due to their transfer to aquatic and terrestrial food chains and possible adverse effects on nontargeted organisms. In the present work, uptake and translocation of metformin, an antidiabetic II medicine, by edible plant species cultivated in agricultural soil have been investigated in greenhouse experiment. Metformin demonstrated a high uptake and translocation to oily seeds of rape ( Brassica napus cv. Sheik and Brassica rapa cv. Valo); expressed as an average bioconcentration factor (BCF, plant concentration over initial concentration in soil, both in dry weight), BCF values as high as 21.72 were measured. In comparison, BCFs for grains of the cereals wheat, barley, and oat were in the range of 0.29-1.35. Uptake and translocation to fruits and vegetables of tomato (BCFs 0.02-0.06), squash (BCFs 0.12-0.18), and bean (BCF 0.88) were also low compared to rape. BCFs for carrot, potato, and leaf forage B. napus cv. Sola were similar (BCF 1-4). Guanylurea, a known degradation product of metformin by microorganisms in activated sludge, was found in barley grains, bean pods, potato peel, and small potatoes. The mechanisms for transport of metformin and guanidine in plants are still unknown, whereas organic cation transporters (OCTs) in mammals are known to actively transport such compounds and may guide the way for further understanding of mechanisms also in plants. PMID:22712757

Eggen, Trine; Lillo, Cathrine

2012-07-18

190

Understanding the physiological and molecular mechanism of persistent organic pollutant uptake and detoxification in cucurbit species (zucchini and squash).  

PubMed

Cucurbita pepo ssp pepo (zucchini) roots phytoextract significant amounts of persistent organic pollutants (POPs) from soil, followed by effective translocation to aboveground tissues. The closely related C. pepo ssp ovifera (squash) does not have this ability. In a DDE-contaminated field soil, zucchini roots and stems contained 3.6 and 6.6-fold greater contaminant than did squash tissues, respectively, and zucchini phytoextracted 12-times more DDE from soil than squash. In batch hydroponics, squash was significantly more sensitive to DDE (2-20 mg/L) exposure; 4 mg/L DDE significantly reduced squash biomass (14%) whereas for zucchini, biomass reductions were observed at 20 mg/L (20%). PCR select Suppression Subtraction Hybridization was used to identify differentially expressed genes in DDE treated zucchini relative to DDE treated squash or non-treated zucchini. After differential screening to eliminate false positives, unique cDNA clones were sequenced. Out of 40 shoot cDNA sequences, 34 cDNAs have homology to parts of phloem filament protein 1 (PP1). Out of 6 cDNAs from the root tissue, two cDNAs are similar to cytochrome P450 like proteins, and one cDNA matches a putative senescence associated protein. From the DDE exposed zucchini seedlings cDNA library, out of 22 differentially expressed genes, 14 cDNAs were found to have homology with genes involved in abiotic stresses, signaling, lipid metabolism, and photosynthesis. A large number of cDNA sequences were found to encode novel unknown proteins that may be involved in uncharacterized pathways of DDE metabolism in plants. A semiquantitative RT-PCR analysis of isolated genes confirmed up-regulation in response to DDE exposure. PMID:20507062

Chhikara, Sudesh; Paulose, Bibin; White, Jason C; Dhankher, Om Parkash

2010-10-01

191

Tunnelling of scalar and Dirac particles from squashed charged rotating Kaluza-Klein black holes  

E-print Network

Thermal radiation of scalar particles and Dirac fermions from squashed charged rotating five-dimensional black holes is considered. To obtain temperature of the black holes we use the tunnelling method. In case of scalar particles we make use of the Hamilton-Jacobi equation. To consider tunnelling of fermions the Dirac equation was investigated. The examination shows that radial parts of the action for scalar particles and fermions in quasi-classical limit in the vicinity of horizon are almost the same and as a consequence it gives rise to the identical expressions for the temperature in both cases.

Stetsko, M M

2014-01-01

192

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

193

A simplified method of constructing infectious clones of begomovirus employing limited restriction enzyme digestion of products of rolling circle amplification.  

PubMed

Most infectious clones of geminiviruses consist of (partial) tandem repeats of viral genomes in the vectors, which usually involve tedious, multi-step assemblies of genomic fragments in the construction process. A simplified procedure was devised to circumvent these problems, which employs limited restriction digestion of multimeric viral genomes produced by rolling circle amplification (RCA), followed by direct cloning into appropriate vectors. The efficiency of the procedure, and infectivity of the dimeric constructs it produced, were demonstrated using three different geminiviruses, namely ageratum yellow vein virus, tomato leaf curl virus, and squash leaf curl virus. PMID:18031835

Wu, Chia-Ying; Lai, Yi-Chin; Lin, Na-Sheng; Hsu, Yau-Heiu; Tsai, Hsin-Tzu; Liao, Jye-Yann; Hu, Chung-Chi

2008-02-01

194

Improved postharvest quality in patagonian squash ( Cucurbita moschata) coated with radiation depolymerized chitosan  

NASA Astrophysics Data System (ADS)

Different molecular weight chitosans were evaluated on the decay of coated Anquito squashes ( Cucurbita moschata) as well as the maintenance of the fruit quality along five storage months. The original chitosan (Mw=391 kDa, 83% DD), was depolymerized by gamma radiation. Apart from chain scission, other chemical changes were not detected by FTIR or UV-vis analyses. The molecular weight characterization of chitosans was done by size exclusion chromatography with dual light scattering and concentration detection (SEC-MALLS-RI). The coating effectiveness was evaluated on the following parameters: fungal decay incidence, weight loss, firmness, total reducing sugar, soluble solid, flesh color, carotene content, pH and titratable acidity. No sign of fungal decay was observed in squashes coated with 122 and 56 kDa chitosans, which were also the most effective treatments in reducing the weight loss. The chitosan with Mw=122 kDa was also the best treatment considering firmness, internal aspect, sugar and carotene content. Then, radiation degraded chitosan was better in C. moschata preservation than the original chitosan.

Pugliese, Maria Alicia; Goitia, Maria Teresa; Yossen, Mariana; Cifone, Norma; Agulló, Enrique; Andreucetti, Noemi

2011-12-01

195

Cytopatholologic features of gliosarcoma with areas of primitive neuroepithelial differentiation of the brain in squash smears.  

PubMed

Gliosarcoma with areas of primitive neuroepithelial differentiation (GSPNED) is an extremely rare neoplasm. A case is presented here in which squash smears of a left temporal lobe tumor in a 76-year-old male demonstrated two distinct and easily recognizable cellular populations, i.e., densely hyperchromatic cells of a primitive nature in a fibrillary background and pleomorphic spindle-shaped cells. Occasional pseudo-rosette formations and nuclear cannibalism suggestive of neuroendocrine differentiation were also found. A cytologic diagnosis of a malignant tumor was suggested, and histochemical and immunohistochemical studies were conducted on formalin-fixed, paraffin-embedded material. Reticulin stain highlighted increased intercellular collagen and reticulin deposition within the spindled regions, whereas nodules with primitive cells were reticulin-poor. There was a diffuse and strong reactivity to neuron specific enolase, synaptophysin and CD56 immunostains. A stain for glial fibrillary acidic protein and S-100 protein demonstrated a subset of tumor cells including elongated cytoplasmic processes. The spindled component was positive for vimentin and smooth muscle actin, whereas the primitive-appearing tumor cells were negative. The diagnosis of GSPNED was confirmed based on cytopathologic, histopathological and immunohistochemical results. The cytomorphologic features of this distinctive tumor are illustrated, and the adjunctival value of squash smears for frozen-section diagnosis is also discussed. This is the first presentation of a cytopathologic analysis that provides an important clue to an accurate diagnosis of GSPNED. PMID:19582814

Hayashi, Toshitetsu; Kushida, Yoshio; Kadota, Kyuichi; Katsuki, Naomi; Bando, Kenji; Miyai, Yumi; Funamoto, Yasunobu; Haba, Reiji

2009-12-01

196

Effect of floor conditions upon frictional characteristics of squash court shoes.  

PubMed

Vertical (FN) and horizontal (FH) forces were recorded while four vertically-loaded court shoes were dragged horizontally across six types of floor surface. Variation in coefficient of limiting friction (FH/FN) between floor surfaces was greater than that between shoes. Squash strokes were also performed on the same surfaces during which FH/FN was calculated. Slips occurred on some surfaces either at heel contact or upon attainment of full-sole contact. It is concluded that the coefficient of limiting friction obtained during full-sole contact with the floor is a suitable means of distinguishing between tractional qualities of shoes. Alternatively, this measure is an inadequate predictor of the likelihood of slips in the game of squash racquets. Dusty floor conditions produce poor traction as does a damp sealed floor. As sweat droplets are unavoidable in the game, floors sealed with urethane represent a significant hazard. Bare, clean, wooden flooring which can absorb moisture represents a better surface than a sealed floor from the point of view of traction. PMID:1856911

Chapman, A E; Leyland, A J; Ross, S M; Ryall, M

1991-01-01

197

Squashing the Millennium Bug: A Year 2000 Compliance Guide for Elementary/Secondary Schools and School Districts.  

ERIC Educational Resources Information Center

This guide was developed to assist the nation's elementary and secondary schools and school districts address their Year 2000 (Y2K) problem. The guide is divided into three sections: Squashing the Millennium Bug Step-by-Step; Remediating Specific Types of Systems; and Appendix. The first chapter presents the following steps for tackling the Year…

Root, Mark; Carlson, Robert; Dexter, David; Karinch, Samantha; Kaplan, Heather

198

Squashing Cubes: Automating Deformable Model Construction for Graphics Doug L. James Jernej Barbic Christopher D. Twigg (Carnegie Mellon University)  

E-print Network

displacement fields can be obtained for many animation purposes. One practical benefit of voxelization models remains a tedious process for animators. Squashing Cubes (SC) automates the construction are interpolated back onto the original model, thus producing the final animation. Such domain embedding schemes

James, Doug L.

199

The effects of ankle guards and taping on joint motion before, during, and after a squash match  

Microsoft Academic Search

The effects of ankle guards and taping on joint motion before, during, and after exercise were studied. Twelve league squash players played two matches, each last ing 1 hour. Two different ankle guards, and two types of tape applied by the same method, served as sup ports. A specially designed goniometer with electronic digital display (accuracy 1 °) was used

Kathryn H. Myburgh; Christopher L. Vaughan; Sedic K. Isaacs

1984-01-01

200

Relative effects of wind stress curl, topography, and stratification on large-scale circulation in Lake Michigan  

E-print Network

, topography, and stratification on large-scale circulation in Lake Michigan, J. Geophys. Res., 108(C2), 3044, topography, and stratification on large- scale circulation in the Great Lakes and other water bodies. The RaoRelative effects of wind stress curl, topography, and stratification on large-scale circulation

201

Numerical investigation on strength design and curling effect of mechanically fastened joints in cold-formed austenitic stainless steel  

Microsoft Academic Search

A variety of parametric studies utilizing the finite element analysis (FEA) have been performed by Kim et al in order to predict the mechanical behavior (ultimate strength) of single shear bolted joints in cold-formed (thin-walled) stainless steel sheet. Strength equations considering the strength reduction by curling effect in bolted joint with long end distance and edge distance have been suggested.

Tae Soo Kim; Hitoshi Kuwamura

2011-01-01

202

A non-nodulating alfalfa mutant displays neither root hair curling nor early cell division in response to Rhizobium meliloti.  

PubMed Central

The early events in the alfalfa-Rhizobium meliloti symbiosis include deformation of epidermal root hairs and the approximately concurrent stimulation of cell dedifferentiation and cell division in the root inner cortex. These early steps have been studied previously by analysis of R. meliloti mutants. Bacterial strains mutated in nodABC, for example, fail to stimulate either root hair curling or cell division events in the plant host, whereas exopolysaccharide (exo) mutants of R. meliloti stimulate host cell division but the resulting nodules are uninfected. As a further approach to understanding early symbiotic interactions, we have investigated the phenotype of a non-nodulating alfalfa mutant, MnNC-1008 (NN) (referred to as MN-1008). Nodulating and non-nodulating plants were inoculated with wild-type R. meliloti and scored for root hair curling and cell divisions. MN-1008 was found to be defective in both responses. Mutant plants inoculated with Exo- bacteria also showed no cell division response. Therefore, the genetic function mutated in MN-1008 is required for both root hair curling and cell division, as is true for the R. meliloti nodABC genes. These observations support the model that the distinct cellular processes of root hair curling and cell division are triggered by related mechanisms or components, or are causally linked. PMID:2535468

Dudley, M E; Long, S R

1989-01-01

203

Conservative management of a case of medial epicondylosis in a recreational squash player  

PubMed Central

Objective: This case study was conducted to evaluate the treatment and management of a patient presenting with medial elbow pain diagnosed as medial epicondylosis. Case: A 35 year old male presented with medial elbow pain of 4–6 weeks duration that worsened after playing squash. Treatment: A course of fascial stripping techniques was initiated, including: cross friction massage, instrument assisted fascial stripping to the medial epicondyle area and over the belly of the pronator teres muscle, ischemic compression of a trigger point in the pronator teres, active assisted compressions to the trigger point noted in the pronator teres, and mobilizations of the carpals, specifically the scaphoid. Instructions were given to the patient regarding icing the elbow and daily eccentric exercises. At a one year follow up, the patient reported complete resolution of symptoms with no recurrence. Conclusion: Conservative management, including eccentric exercises, mobilizations, and fascial stripping appear to be beneficial in the treatment of medial epicondylosis. PMID:21403779

Hudes, Karen

2011-01-01

204

The gravity dual of supersymmetric gauge theories on a squashed S 1 × S 3  

NASA Astrophysics Data System (ADS)

We present a new one-parameter family of supersymmetric solutions deforming AdS5. This is constructed as an asymptotically locally anti de Sitter (AlAdS) solution of five-dimensional minimal gauged supergravity, with topology ? × ?4 and a non-trivial graviphoton field, and can be uplifted to ten or eleven dimensional supergravities. An analytic continuation of this solution yields the gravity dual to a class of four-dimensional supersymmetric gauge theories on a curved manifold with topology S 1 × S 3, comprising an SU(2) × U(1)-symmetric squashed three-sphere, with a non-trivial background gauge field coupling to the R-symmetry current. We compute the holographically renormalised on-shell action and interpret it in terms of the Casimir energy of the dual field theory. We also determine the holographic conserved charges of the solution and discuss relations between them.

Cassani, Davide; Martelli, Dario

2014-08-01

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

Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona  

NASA Technical Reports Server (NTRS)

The study of magnetic connectivity in the solar corona reveals a need to generalize the field line mapping technique to arbitrary geometry of the boundaries and systems of coordinates. Indeed, the global description of the connectivity in the corona requires the use of the photospheric and solar wind boundaries. Both are closed surfaces and therefore do not admit a global regular system of coordinates. At least two overlapping regular systems of coordinates for each of the boundaries are necessary in this case to avoid spherical-pole-like singularities in the coordinates of the footpoints. This implies that the basic characteristic of magnetic connectivity-the squashing degree or factor Q of elemental flux tubes, according to Titov and coworkers-must be rewritten in covariant form. Such a covariant expression of Q is derived in this work. The derived expression is very flexible and highly efficient for describing the global magnetic connectivity in the solar corona. In addition, a general expression for a new characteristic Q1, which defines a squashing of the flux tubes in the directions perpendicular to the field lines, is determined. This new quantity makes it possible to filter out the quasi-separatrix layers whose large values of Q are caused by a projection effect at the field lines nearly touching the photosphere. Thus, the value Q1 provides a much more precise description of the volumetric properties of the magnetic field structure. The difference between Q and Q1 is illustrated by comparing their distributions for two configurations, one of which is the Titov-Demoulin model of a twisted magnetic field.

Titov, V. S.

2007-01-01

207

Comparison of wind-stress algorithms and their influence on wind-stress curl using buoy measurements over the shelf off Bodega Bay, California  

NASA Astrophysics Data System (ADS)

The main objectives of this study were to compare three wind-stress algorithms of varying intricacy and estimate the extent to which each method altered computed wind-stress curl. The algorithms included (1) a simple bulk formula for neutral conditions that is dependent only on wind velocity components; (2) a formula that in addition to dependence on wind components includes a simplified effect of thermal stability through differences in air and sea temperatures; and (3) an algorithm that includes full treatment of dynamics and atmospheric stability. Data for the analysis were from a field program that used a special buoy network off Bodega Bay during 28 June-4 August 2001. A diamond-shaped setup of five closely separated buoys in Bodega Bay allowed for one of the first attempts to compute wind-stress curl over the ocean using buoy measurements. Based on an analysis of the available dataset, the marine layer over Bodega Bay is characterized by positive wind-stress curl with a median value around 0.2 Pa (100 km) -1 and maximum values reaching 2.5 Pa (100 km) -1. Positive wind-stress curl was observed for all wind speed conditions, whereas negative wind-stress curl episodes were associated mostly with low-wind conditions. Comparison of wind-stress curl computed using the three algorithms showed that differences among them can be significant. The first and third algorithms indicated similar stress curl (difference around 10%), but the differences between these two and the second algorithm were much higher (approximately 40%). The reason for the difference is the stability correction, which in the third algorithm strongly decreases with an increase in wind speeds, but stays at a similar level for all wind speeds in the second algorithm. Consequently, for higher wind speeds the variability of wind stress calculated using the second algorithm is greater than for the other two algorithms, causing significant differences in computed wind-stress curl (root mean-square error equal to 0.19 Pa (100 km) -1). Despite the apparent biases in computed wind stress and wind-stress curl among the algorithms, all of them show a significant trend of decreasing sea-surface temperature (SST) with increasing wind-stress curl. The bootstrapping analysis has revealed that both the along-shore wind stress and wind-stress curl have noticeable correlation with the changes in the sea-surface temperature as an indirect indication of the upwelling. An additional analysis, based on the low-pass filtered data, showed also significant agreement between the measured divergence in the cross-shore surface transport and the wind-stress curl computed for all three algorithms.

Kochanski, Adam; Kora?in, Darko; Dorman, Clive E.

2006-12-01

208

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

209

Agrobacterium-mediated transformation of kabocha squash (Cucurbita moschata Duch) induced by wounding with aluminum borate whiskers.  

PubMed

An efficient genetic transformation method for kabocha squash (Cucurbita moschata Duch cv. Heiankogiku) was established by wounding cotyledonary node explants with aluminum borate whiskers prior to inoculation with Agrobacterium. Adventitious shoots were induced from only the proximal regions of the cotyledonary nodes and were most efficiently induced on Murashige-Skoog agar medium with 1 mg/L benzyladenine. Vortexing with 1% (w/v) aluminum borate whiskers significantly increased Agrobacterium infection efficiency in the proximal region of the explants. Transgenic plants were screened at the T(0) generation by sGFP fluorescence, genomic PCR, and Southern blot analyses. These transgenic plants grew normally and T(1) seeds were obtained. We confirmed stable integration of the transgene and its inheritance in T(1) generation plants by sGFP fluorescence and genomic PCR analyses. The average transgenic efficiency for producing kabocha squashes with our method was about 2.7%, a value sufficient for practical use. PMID:21400224

Nanasato, Yoshihiko; Konagaya, Ken-ichi; Okuzaki, Ayako; Tsuda, Mai; Tabei, Yutaka

2011-08-01

210

Unclosed HIV-1 capsids suggest a curled sheet model of assembly.  

PubMed

The RNA genome of retroviruses is encased within a protein capsid. To gather insight into the assembly and function of this capsid, we used electron cryotomography to image human immunodeficiency virus (HIV) and equine infectious anemia virus (EIAV) particles. While the majority of viral cores appeared closed, a variety of unclosed structures including rolled sheets, extra flaps, and cores with holes in the tip were also seen. Simulations of nonequilibrium growth of elastic sheets recapitulated each of these aberrations and further predicted the occasional presence of seams, for which tentative evidence was also found within the cryotomograms. To test the integrity of viral capsids in vivo, we observed that ~25% of cytoplasmic HIV complexes captured by TRIM5? had holes large enough to allow internal green fluorescent protein (GFP) molecules to escape. Together, these findings suggest that HIV assembly at least sometimes involves the union in space of two edges of a curling sheet and results in a substantial number of unclosed forms. PMID:23079241

Yu, Zhiheng; Dobro, Megan J; Woodward, Cora L; Levandovsky, Artem; Danielson, Cindy M; Sandrin, Virginie; Shi, Jiong; Aiken, Christopher; Zandi, Roya; Hope, Thomas J; Jensen, Grant J

2013-01-01

211

Unclosed HIV-1 Capsids Suggest a Curled Sheet Model of Assembly  

PubMed Central

The RNA genome of retroviruses is encased within a protein capsid. To gather insight into the assembly and function of this capsid, we used electron cryotomography to image human immunodeficiency virus (HIV) and equine infectious anemia virus (EIAV) particles. While the majority of viral cores appeared closed, a variety of unclosed structures including rolled sheets, extra flaps, and cores with holes in the tip were also seen. Simulations of nonequilibrium growth of elastic sheets recapitulated each of these aberrations and further predicted the occasional presence of seams, for which tentative evidence was also found within the cryotomograms. To test the integrity of viral capsids in vivo, we observed that ?25% of cytoplasmic HIV complexes captured by TRIM5? had holes large enough to allow internal green fluorescent protein (GFP) molecules to escape. Together, these findings suggest that HIV assembly at least sometimes involves the union in space of two edges of a curling sheet and results in a substantial number of unclosed forms. PMID:23079241

Yu, Zhiheng; Dobro, Megan J.; Woodward, Cora L.; Levandovsky, Artem; Danielson, Cindy M.; Sandrin, Virginie; Shi, Jiong; Aiken, Christopher; Zandi, Roya; Hope, Thomas J.; Jensen, Grant J.

2012-01-01

212

Effects of mutations in the Arabidopsis Cold Shock Domain Protein 3 (AtCSP3) gene on leaf cell expansion  

PubMed Central

The cold shock domain is among the most evolutionarily conserved nucleic acid binding domains from prokaryotes to higher eukaryotes, including plants. Although eukaryotic cold shock domain proteins have been extensively studied as transcriptional and post-transcriptional regulators during various developmental processes, their functional roles in plants remains poorly understood. In this study, AtCSP3 (At2g17870), which is one of four Arabidopsis thaliana c old s hock domain proteins (AtCSPs), was functionally characterized. Quantitative RT-PCR analysis confirmed high expression of AtCSP3 in reproductive and meristematic tissues. A homozygous atcsp3 loss-of-function mutant exhibits an overall reduced seedling size, stunted and orbicular rosette leaves, reduced petiole length, and curled leaf blades. Palisade mesophyll cells are smaller and more circular in atcsp3 leaves. Cell size analysis indicated that the reduced size of the circular mesophyll cells appears to be generated by a reduction of cell length along the leaf-length axis, resulting in an orbicular leaf shape. It was also determined that leaf cell expansion is impaired for lateral leaf development in the atcsp3 loss-of-function mutant, but leaf cell proliferation is not affected. AtCSP3 loss-of-function resulted in a dramatic reduction of LNG1 transcript, a gene that is involved in two-dimensional leaf polarity regulation. Transient subcellular localization of AtCSP3 in onion epidermal cells confirmed a nucleocytoplasmic localization pattern. Collectively, these data suggest that AtCSP3 is functionally linked to the regulation of leaf length by affecting LNG1 transcript accumulation during leaf development. A putative function of AtCSP3 as an RNA binding protein is also discussed in relation to leaf development. PMID:22888122

Yang, Yongil; Karlson, Dale

2012-01-01

213

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

214

Curl flux, coherence, and population landscape of molecular systems: Nonequilibrium quantum steady state, energy (charge) transport, and thermodynamics  

NASA Astrophysics Data System (ADS)

We established a theoretical framework in terms of the curl flux, population landscape, and coherence for non-equilibrium quantum systems at steady state, through exploring the energy and charge transport in molecular processes. The curl quantum flux plays the key role in determining transport properties and the system reaches equilibrium when flux vanishes. The novel curl quantum flux reflects the degree of non-equilibriumness and the time-irreversibility. We found an analytical expression for the quantum flux and its relationship to the environmental pumping (non-equilibriumness quantified by the voltage away from the equilibrium) and the quantum tunneling. Furthermore, we investigated another quantum signature, the coherence, quantitatively measured by the non-zero off diagonal element of the density matrix. Populations of states give the probabilities of individual states and therefore quantify the population landscape. Both curl flux and coherence depend on steady state population landscape. Besides the environment-assistance which can give dramatic enhancement of coherence and quantum flux with high voltage at a fixed tunneling strength, the quantum flux is promoted by the coherence in the regime of small tunneling while reduced by the coherence in the regime of large tunneling, due to the non-monotonic relationship between the coherence and tunneling. This is in contrast to the previously found linear relationship. For the systems coupled to bosonic (photonic and phononic) reservoirs the flux is significantly promoted at large voltage while for fermionic (electronic) reservoirs the flux reaches a saturation after a significant enhancement at large voltage due to the Pauli exclusion principle. In view of the system as a quantum heat engine, we studied the non-equilibrium thermodynamics and established the analytical connections of curl quantum flux to the transport quantities such as energy (charge) transfer efficiency, chemical reaction efficiency, energy dissipation, heat and electric currents observed in the experiments. We observed a perfect transfer efficiency in chemical reactions at high voltage (chemical potential difference). Our theoretical predicted behavior of the electric current with respect to the voltage is in good agreements with the recent experiments on electron transfer in single molecules.

Zhang, Z. D.; Wang, J.

2014-06-01

215

Leaf to Landscape  

Microsoft Academic Search

\\u000a The capacity of terrestrial plant leaves for photosynthetic CO2 fixation per unit gram of leaf varies over 10-fold (Reich et al. 1997). The results of CO2 fixation, processing and subsequent accumulation of mass (Fig. 8.1) gives plants the most enormous variation in size of organisms\\u000a on earth (Niklas and Enquist 2001). The variation in photosynthetic capacity and in leaf form

David S. Ellsworth; Ülo Niinemets; Peter B. Reich

216

Leaf to Landscape  

Microsoft Academic Search

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

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

217

Inoculation of plants with begomoviruses by particle bombardment without cloning: Using rolling circle amplification of total DNA from infected plants and whiteflies.  

PubMed

A new system for inoculation of plants with begomoviral DNA without cloning or the use insect vectors is described. Total DNA extracted from begomovirus-infected plants was amplified by rolling circle amplification (RCA) using the bacteriophage phi29 DNA polymerase, and inoculated to plants by particle bombardment. Infection rates of up to 100% were obtained using this technique. This technique successfully inoculated all the begomoviruses evaluated: five bipartite (Bean golden yellow mosaic virus, Cabbage leaf curl virus, Squash leaf curl virus, Tomato mottle virus, Watermelon chlorotic stunt virus) as well as one monopartite (Tomato yellow leaf curl virus). The success of the technique was not dependent upon plant species. Four species from three plant families [Phaseolus vulgaris (bean), Solanum lycopersicum (tomato), Cucurbita pepo (squash), and Citrullus lanatus (watermelon)], could all be inoculated by this technique. The success of the method was not dependent upon either the type or the age of the source of virus. Infectious DNA was obtained successfully from fresh, freeze-dried or desiccated plant material, from squashes of plant leaves on FTA cards, as well as from the insect vector. Plant material collected and dried as long as 25 years ago yielded infectious DNA by this method. In summary, this method can be used to obtain infectious DNA of single-stranded circular DNA viruses that can be activated for purposes of completing Koch's postulates, for preservation of pure virus cultures, and for many other applications where infectious DNA is required. PMID:20447420

Guenoune-Gelbart, Dana; Sufrin-Ringwald, Tali; Capobianco, Heather; Gaba, Victor; Polston, Jane E; Lapidot, Moshe

2010-09-01

218

Movement of soil-applied imidacloprid and thiamethoxam into nectar and pollen of squash (Cucurbita pepo).  

PubMed

There has been recent interest in the threat to bees posed by the use of systemic insecticides. One concern is that systemic insecticides may translocate from the soil into pollen and nectar of plants, where they would be ingested by pollinators. This paper reports on the movement of two such systemic neonicotinoid insecticides, imidacloprid and thiamethoxam, into the pollen and nectar of flowers of squash (Cucurbita pepo cultivars "Multipik," "Sunray" and "Bush Delicata") when applied to soil by two methods: (1) sprayed into soil before seeding, or (2) applied through drip irrigation in a single treatment after transplant. All insecticide treatments were within labeled rates for these compounds. Pollen and nectar samples were analyzed using a standard extraction method widely used for pesticides (QuEChERS) and liquid chromatography mass spectrometric analysis. The concentrations found in nectar, 10 ± 3 ppb (mean ± s.d) for imidacloprid and 11 ± 6 ppb for thiamethoxam, are higher than concentrations of neonicotinoid insecticides in nectar of canola and sunflower grown from treated seed, and similar to those found in a recent study of neonicotinoids applied to pumpkins at transplant and through drip irrigation. The concentrations in pollen, 14 ± 8 ppb for imidacloprid and 12 ± 9 ppb for thiamethoxam, are higher than those found for seed treatments in most studies, but at the low end of the range found in the pumpkin study. Our concentrations fall into the range being investigated for sublethal effects on honey bees and bumble bees. PMID:22761727

Stoner, Kimberly A; Eitzer, Brian D

2012-01-01

219

Exogenous methyl jasmonate treatment increases glucosinolate biosynthesis and quinone reductase activity in kale leaf tissue.  

PubMed

Methyl jasmonate (MeJA) spray treatments were applied to the kale varieties 'Dwarf Blue Curled Vates' and 'Red Winter' in replicated field plantings in 2010 and 2011 to investigate alteration of glucosinolate (GS) composition in harvested leaf tissue. Aqueous solutions of 250 µM MeJA were sprayed to saturation on aerial plant tissues four days prior to harvest at commercial maturity. The MeJA treatment significantly increased gluconasturtiin (56%), glucobrassicin (98%), and neoglucobrassicin (150%) concentrations in the apical leaf tissue of these genotypes over two seasons. Induction of quinone reductase (QR) activity, a biomarker for anti-carcinogenesis, was significantly increased by the extracts from the leaf tissue of these two cultivars. Extracts of apical leaf tissues had greater MeJA mediated increases in phenolics, glucosinolate concentrations, GS hydrolysis products, and QR activity than extracts from basal leaf tissue samples. The concentration of the hydrolysis product of glucoraphanin, sulforphane was significantly increased in apical leaf tissue of the cultivar 'Red Winter' in both 2010 and 2011. There was interaction between exogenous MeJA treatment and environmental conditions to induce endogenous JA. Correlation analysis revealed that indole-3-carbanol (I3C) generated from the hydrolysis of glucobrassicin significantly correlated with QR activity (r = 0.800, P<0.001). Concentrations required to double the specific QR activity (CD values) of I3C was calculated at 230 µM, which is considerably weaker at induction than other isothiocyanates like sulforphane. To confirm relationships between GS hydrolysis products and QR activity, a range of concentrations of MeJA sprays were applied to kale leaf tissues of both cultivars in 2011. Correlation analysis of these results indicated that sulforaphane, NI3C, neoascorbigen, I3C, and diindolylmethane were all significantly correlated with QR activity. Thus, increased QR activity may be due to combined increases in phenolics (quercetin and kaempferol) and GS hydrolysis product concentrations rather than by individual products alone. PMID:25084454

Ku, Kang-Mo; Jeffery, Elizabeth H; Juvik, John A

2014-01-01

220

Functional and Neuromuscular Changes in the Hamstrings After Drop Jumps and Leg Curls  

PubMed Central

The purpose of this study was to use a holistic approach to investigate changes in jumping performance, kinaesthesia, static balance, isometric strength and fast stepping on spot during a 5-day recovery period, following an acute bout of damaging exercise consisted of drop jumps and leg curls, where specific emphasis was given on the hamstring muscles. Eleven young healthy subjects completed a series of highly intensive damaging exercises for their hamstring muscles. Prior to the exercise, and during the 5-day recovery period, the subjects were tested for biochemical markers (creatine kinase, aspartate aminotransferase, and lactate dehydrogenase), perceived pain sensation, physical performance (squat jump, counter movement jump, maximal frequency leg stamping, maximal isometric torque production and maximally explosive isometric torque production), kinaesthesia (active torque tracking) and static balance. We observed significant decreases in maximal isometric knee flexion torque production, the rate of torque production, and majority of the parameters for vertical jump performance. No alterations were found in kinaesthesia, static balance and fast stepping on spot. The highest drop in performance and increase in perceived pain sensation generally occurred 24 or 48 hours after the exercise. Damaging exercise substantially alters the neuromuscular functions of the hamstring muscles, which is specifically relevant for sports and rehabilitation experts, as the hamstrings are often stretched to significant lengths, in particular when the knee is extended and hip flexed. These findings are practically important for recovery after high-intensity trainings for hamstring muscles. Key Points Hamstring function is significantly reduced following specifically damaging exercise. It fully recovers 120 hours after the exercise. Prevention of exercise-induced muscle damage is cruicial for maintaining normal training regime. PMID:24149148

Sarabon, Nejc; Panjan, Andrej; Rosker, Jernej; Fonda, Borut

2013-01-01

221

Radionuclide concentrations in pinto beans, sweet corn, and zucchini squash grown in Los Alamos Canyon at Los Alamos National Laboratory  

SciTech Connect

Pinto beans, sweet corn, and zucchini squash (Cucurbita pepo var. black beauty) were grown in a randomized complete-block field/pot experiment at a site that contained the highest observed levels of surface gross gamma radioactivity within Los Alamos Canyon (LAC) at Los Alamos National Laboratory. Soils as well as washed edible and nonedible crop tissues were analyzed for various radionuclides and heavy metals . Most radionuclides, with the exception of {sup 3}H and {sup tot}U, in soil from LAC were detected in significantly higher concentrations (p <0.01) than in soil collected from regional background (RBG) locations. Similarly, most radionuclides in edible crop portions of beans, squash, and corn were detected in significantly higher (p <0.01 and 0.05) concentrations than RBG. Most soil-to-plant concentration ratios for radionuclides in edible and nonedible crop tissues from LAC were within the default values given by the Nuclear Regulatory Commission and Environmental Protection Agency. All heavy metals in soils, as well as edible and nonedible crop tissues grown in soils from LAC, were within RBG concentrations. Overall, the total maximum net positive committed effective dose equivalent (CEDE)--the CEDE plus two sigma for each radioisotope minus background and then all positive doses summed--to a hypothetical 50-year resident that ingested 160 kg of beans, corn, and squash in equal proportions, was 74 mrem y{sup -1}. This dose was below the International Commission on Radiological Protection permissible dose limit (PDL) of 100 mrem y{sup -1} from all pathways; however, the addition of other internal and external exposure route factors may increase the overall dose over the PDL. Also, the risk of an excess cancer fatality, based on 74 mrem y{sup -1}, was 3.7 x 10{sup -5} (37 in a million), which is above the Environmental Protection Agency`s (acceptable) guideline of one in a million. 31 refs., 15 tabs.

Fresquez, P.R.; Mullen, M.A.; Naranjo, L. Jr.; Armstrong, D.R.

1997-05-01

222

a Study of the Real Squashing Mode in Superfluid HELIUM-3-B Using Nonresonant Ultrasonic Transducers.  

NASA Astrophysics Data System (ADS)

Ultrasonic collective mode spectroscopy invites comparison to other, more routine, forms of spectroscopy. Yet ultrasound studies of superfluid ^3He are far from routine, requiring extensive cold times but generally identifying modes at only a few points in the phase space defined by pressure, frequency, temperature and magnetic field. A major difficulty is that the resonant quartz transducers used to generate and detect sound in liquid helium allow phase space to be explored only on surfaces of constant frequency. Since other variables can be changed either slowly or not at all, the spectroscopic investigation is tedious. In the present work, transducers were fashioned from piezoelectric plastic film fastened to a solid substrate. The smooth broadband response up to ~100MHz of these composite transducers allowed a systematic investigation of the real squashing (RSQ, J = 2^+) mode in superfluid ^3He-B. The zero field mode frequency was identified at seven pressures between 0 and 29 bar, over a continuum of temperature. In particular, the zero temperature limit of RSQ frequency at constant pressure transducers was easily measured by repeated frequency sweeps at constant temperatures. Since the B phase mode frequencies approach a constant as T to 0, low temperature data are nearly impossible to obtain with fixed frequency transducers. In fact, the restriction of prior experiments to regions of sizeable partial f_{rm rsq}/ partial T meant that precision was limited by thermometric uncertainties. The broadband approach overcomes this deficiency. Aside from establishing the feasibility of a useful technique, the RSQ measurements have theoretical implications. Precise constraints are placed on the values of x_sp {3}{-1} (a measure of the strength of f-wave coupling) and F_sp{2} {a} (a Fermi interaction parameter). Comparison of these determinations with those from other experiments makes clear that "non-trivial" strong-coupling corrections to collective mode theory are needed in order to explain data at high pressures.

Fraenkel, Peter N.

223

An investigation of leaf mosaics  

Microsoft Academic Search

A field study of leaf mosaics of various species of flowering plants was undertaken as part of a course in photosynthesis. The work required little or no theoretical background knowledge. Leaf mosaics were observed, described, and classified into types. Features of the morphology and growth of each species which contributed to the formation of a leaf mosaic were recorded. The

E. L. Oxlade

1998-01-01

224

Curl-free vector potential observation on the macro-scale and a new dimension to the Lorentz trajectory  

NASA Astrophysics Data System (ADS)

The recently reported curl-free vector potential observation on the macro-scale, which has been attributed to a macro-scale matter wave associated with the quantum modulation of the de Broglie wave along the magnetic field, is seen to be in apparent contravention with the Lorentz equation of classical electrodynamics, which as a descriptor on the macro-scale takes no cognizance of a curl-free vector potential. The two different formalisms—a deterministic one à la Lorentz and a probabilistic one by the quantum modulation—both existing on the macro-scale and, though in apparent contravention, complement each other and are essential for a complete description of all phenomena relating to charged particle dynamics. The quantum modulations which arise in consequence of transition across Landau levels appear as ‘hole’ auto-excitations in the Lorentz trajectory involving internal inelastic scattering. This lends a new dimension to the Lorentz trajectory which, though on the classical macro-scale, acts like a ‘quantum resonator’ and can now exist in a number of self-excited states labelled by the Landau level interval involved in the excitation, and which are of quantum origin and on the macro-scale, with the quantum modulations being the excitations.

Varma, Ram K.

2013-09-01

225

The Effect of Court Location and Available Time on the Tactical Shot Selection of Elite Squash Players  

PubMed Central

No previous research in squash has considered the time between shots or the proximity of the ball to a wall, which are two important variables that influence shot outcomes. The aim of this paper was to analyse shot types to determine the extent to which they are played in different court areas and a more detailed analysis to determine whether the time available had an influence on the shot selected. Ten elite matches, contested by fifteen of the world’s top right handed squash players (age 27 ± 3.2, height 1.81 ± 0.06 m, weight 76.3 ± 3.7 kg), at the men’s World Team Championships were processed using the SAGIT/Squash tracking system with shot information manually added to the system. Results suggested that shot responses were dependent upon court location and the time between shots. When these factors were considered repeatable performance existed to the extent that one of two shots was typically played when there was limited time to play the shot (< 1.20s). For example, it was clear that when players did not have a lot of time to hit the ball (low time i.e. < 1.06s, and mid time i.e. 1.06 - 1.20s) in the front left corner close to the side wall, the crosscourt lob was used frequently (44.30% and 36.31% respectively) whereas when there was more time this shot was seldom used (13.64%). Consequently variant and invariant behaviour were shown to exist in elite squash although for the first time it was suggested that the availability of time to play a shot contributed to which of these behaviours was evident. This analysis could be extended by adopting a case study approach to see how individual differences in strategy and tactics affect shot selections. Key points Previous research has suggested that a playing strategy, elements decided in advance of the match, may be evident for elite players by examining court location and preceding shot type, however these parameters alone are unlikely to be sufficient predictors. At present there is no known analysis in squash, or indeed in any of the racket sports, that has quantified the time available to respond to different shot types. An understanding of the time interval between shots and the movement characteristics of the player responding to different shots according to the court positions might facilitate a better understanding of the dynamics that determine shot selection. Some elements of a general playing strategy were evident e.g. predominately hitting to the back left of the court, but tactical differences in shot selection were also evident on the basis of court location and time available to play a shot. PMID:24149727

Vuckovic, Goran; James, Nic; Hughes, Mike; Murray, Stafford; Sporis, Goran; Pers, Janez

2013-01-01

226

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

227

Giardia Cyst Wall Protein 1 Is a Lectin That Binds to Curled Fibrils of the GalNAc Homopolymer  

PubMed Central

The infectious and diagnostic stage of Giardia lamblia (also known as G. intestinalis or G. duodenalis) is the cyst. The Giardia cyst wall contains fibrils of a unique ?-1,3-linked N-acetylgalactosamine (GalNAc) homopolymer and at least three cyst wall proteins (CWPs) composed of Leu-rich repeats (CWPLRR) and a C-terminal conserved Cys-rich region (CWPCRR). Our goals were to dissect the structure of the cyst wall and determine how it is disrupted during excystation. The intact Giardia cyst wall is thin (?400 nm), easily fractured by sonication, and impermeable to small molecules. Curled fibrils of the GalNAc homopolymer are restricted to a narrow plane and are coated with linear arrays of oval-shaped protein complex. In contrast, cyst walls of Giardia treated with hot alkali to deproteinate fibrils of the GalNAc homopolymer are thick (?1.2 µm), resistant to sonication, and permeable. The deproteinated GalNAc homopolymer, which forms a loose lattice of curled fibrils, is bound by native CWP1 and CWP2, as well as by maltose-binding protein (MBP)-fusions containing the full-length CWP1 or CWP1LRR. In contrast, neither MBP alone nor MBP fused to CWP1CRR bind to the GalNAc homopolymer. Recombinant CWP1 binds to the GalNAc homopolymer within secretory vesicles of Giardia encysting in vitro. Fibrils of the GalNAc homopolymer are exposed during excystation or by treatment of heat-killed cysts with chymotrypsin, while deproteinated fibrils of the GalNAc homopolymer are degraded by extracts of Giardia cysts but not trophozoites. These results show the Leu-rich repeat domain of CWP1 is a lectin that binds to curled fibrils of the GalNAc homopolymer. During excystation, host and Giardia proteases appear to degrade bound CWPs, exposing fibrils of the GalNAc homopolymer that are digested by a stage-specific glycohydrolase. PMID:20808847

Chatterjee, Aparajita; Carpentieri, Andrea; Ratner, Daniel M.; Bullitt, Esther; Costello, Catherine E.; Robbins, Phillips W.; Samuelson, John

2010-01-01

228

Healing the Wounds of War and More: An Integrative Approach to Peace--The Work of Adam Curle and Others with Mir i dobro in Zupanja, Croatia.  

ERIC Educational Resources Information Center

Examines practical implications of Curle's approach to psychological aspects of conflict and peacemaking as evidenced in the Mir i dobro project in Zupanja, taking into consideration some of the current debates concerning treatment of psychological trauma, including validity of the diagnosis of posttraumatic stress disorder and use of so-called…

Mitchels, Barbara

2003-01-01

229

Counting Microfiche: The Utilization of the Microform Section of the ANSI Standard Z39.7-1983 "Library Statistics"; Microfiche Curl; and "Poly" or "Cell"?  

ERIC Educational Resources Information Center

The first of three articles describes procedures for using ANSI statistical methods for estimating the number of pieces in large homogeneous collections of microfiche. The second discusses causes of curl, its control, and measurement, and the third compares the advantages and disadvantages of cellulose acetate and polyester base for microforms.…

Caldwell-Wood, Naomi; And Others

1987-01-01

230

Application of Failure Mode and Effect Analysis (FMEA), Cause and Effect Analysis, and Pareto Diagram in Conjunction with HACCP to a Corn Curl Manufacturing Plant  

Microsoft Academic Search

The Failure Mode and Effect Analysis (FMEA) model has been applied for the risk assessment of corn curl manufacturing. A tentative approach of FMEA application to the snacks industry was attempted in an effort to exclude the presence of GMOs in the final product. This is of crucial importance both from the ethics and the legislation (Regulations EC 1829\\/2003; EC

Theodoros H. Varzakas; Ioannis S. Arvanitoyannis

2007-01-01

231

Islands in locally-forced basin circulations The circulation response of a square basin with an island and localized surface stress curl  

E-print Network

Islands in locally-forced basin circulations Sam Potter 1 Abstract The circulation response of a square basin with an island and localized surface stress curl is discussed. Attempts in a laboratory were experiment. Numerical simulations show that the effect of an island on the circulation of a square basin

Lebovitz, Norman

232

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

233

Relationship Between Fatigue Index and Number of Repetition Maxima with Sub-Maximal Loads in Biceps Curl  

PubMed Central

The aim of this study was to investigate the relationship between the number of repetition maxima to volitional failure (RM) at 60%, 75%, 90% of 1RM and fatigue index (FI), a determinant of the muscular endurance level. Thirty four resistance trained male participants attended two testing sessions. The first session was conducted to assess 1RM load and RM at 60%, 75% and 90% of 1RM in the supine biceps curl (SBC) exercise. In the second session, a FI test protocol consisting of five sets of SBC with 90 s rest between sets was performed to determine FI values. Each set was performed to volitional failure using a sub-maximal load in the range of 15-20RM. Hypothetical high FI and low FI groups (17 participants with the highest and lowest FI values, respectively) were formed for statistical analyses. ANOVA results revealed that RM at 60%, 75%, 90% of 1RM were not significantly different between FI groups when controlled for mean repetition tempo (p=0.11, p=0.38, p=0.13, respectively). Pearson’s correlation coefficients revealed that no significant relationship was present between FI values and RM at 60%, 75%, 90% of 1RM (p=0.40, p=0.46, p=0.14, respectively). In conclusion, the muscular endurance level of participants defined in terms of FI value was not an indicator of RM in SBC. Therefore, athletes with different muscular endurance levels can use similar percentages of 1RM in biceps curl exercise in their training programs when the aim is to elicit training adaptations related to specific RM zones. PMID:24235992

Pekunlu, Ekim; Atalag, Ozan

2013-01-01

234

?C1, the pathogenicity factor of TYLCCNV, interacts with AS1 to alter leaf development and suppress selective jasmonic acid responses  

PubMed Central

Viruses induce pathogenic symptoms on plants but the molecular basis is poorly understood. Here, we show that transgenic Arabidopsis expressing the pathogenesis protein ?C1 of Tomato yellow leaf curl China virus (TYLCCNV), a geminivirus, can phenocopy to a large extent disease symptoms of virus-infected tobacco plants in having upward curled leaves, radialized leaves with outgrowth tissues from abaxial surfaces, and sterile flowers. These morphological changes are paralleled by a reduction in miR165/166 levels and an increase in PHB and PHV transcript levels. Two factors, ASYMMETRIC LEAVES 1 (AS1) and ASYMMETRIC LEAVES 2 (AS2), are known to regulate leaf development as AS1/AS2 complex. Strikingly, ?C1 plants phenocopy plants overexpressing AS2 at the morphological and molecular level and ?C1 is able to partially complement as2 mutation. ?C1 binds directly to AS1, elicits morphological and gene expression changes dependent on AS1 but not AS2, and attenuates expression of selective jasmonic acid (JA)-responsive gene. Our results show that ?C1 forms a complex with AS1 to execute its pathogenic functions and to suppress a subset of JA responses. PMID:18794352

Yang, Jun-Yi; Iwasaki, Mayumi; Machida, Chiyoko; Machida, Yasunori; Zhou, Xueping; Chua, Nam-Hai

2008-01-01

235

Leaf orientation and sunlit leaf area distribution in cotton  

Microsoft Academic Search

The diurnal leaf orientation behaviour of row-planted cotton plants (Gossypium hirsutum L. cv. ‘DES 119’) and its relationship to sunlit leaf area distribution at three stages of development were studied in the field. Electromagnetic digitizing was used for plant geometrical structure measurement for three periods of 2 h during the day. Cotton leaves showed a diaheliotropic response throughout the day.

Sornprach Thanisawanyangkura; Herve Sinoquet; Pierre Rivet; Michel Cretenet; Eric Jallas

1997-01-01

236

Estimation of Moisture in Maize Leaf by Measuring Leaf  

Microsoft Academic Search

Leaf moisture of maize was estimated by variation of dielectric constant. These variations are measured via designed and manufactured capacitive sensors. Capacitance was measured at two frequencies (100 kHz & 1 MHz). The results showed that in all cases the best fitted curve for variations of dielectric constant in relation to leaf moisture percentage was in the form of y=aebx

AMIN AFZAL; SAYED-FARHAD MOUSAVI

237

Short communication Leaf optical properties and photosynthetic leaf absorptances  

E-print Network

assessments of the photo-physiology of seagrasses (Beer et al., 2001). Pulse amplitude modulated (PAM of photosynthetically active radiation (PAR) at the leaf surface and the fraction of the PAR absorbed by the leaf (Beer et al., 1998, 2000, 2001; Beer and Bjo¨rk, 2000; Schreiber, 2004). The fraction of incident PAR

Durako, Michael J.

238

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

239

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

240

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

241

Soaking Summer Squash Seeds in Low Concentrations of Cobalt Solution Before Sowing Increased Plant Growth, Femaleness, and Fruit Yield via Increasing Plant Ethylene Level  

Microsoft Academic Search

.   Soaking summer squash (Cucurbita pepo cv. Eskandarany) seeds in continuously aerated solutions of 0.25, 0.50, and 1.00 ppm Co2+ for 48 h before sowing strongly increased plant growth, femaleness, and fruit yield compared with those of water- (control)\\u000a or 0.5 mm AOA (aminooxyacetic acid)-soaked seeds. Following the same pattern, plants of Co2+-soaked seeds produced significantly higher ethylene levels as

M. A. Atta-Aly

1998-01-01

242

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

243

Application of Failure Mode and Effect Analysis (FMEA), cause and effect analysis, and Pareto diagram in conjunction with HACCP to a corn curl manufacturing plant.  

PubMed

The Failure Mode and Effect Analysis (FMEA) model has been applied for the risk assessment of corn curl manufacturing. A tentative approach of FMEA application to the snacks industry was attempted in an effort to exclude the presence of GMOs in the final product. This is of crucial importance both from the ethics and the legislation (Regulations EC 1829/2003; EC 1830/2003; Directive EC 18/2001) point of view. The Preliminary Hazard Analysis and the Fault Tree Analysis were used to analyze and predict the occurring failure modes in a food chain system (corn curls processing plant), based on the functions, characteristics, and/or interactions of the ingredients or the processes, upon which the system depends. Critical Control points have been identified and implemented in the cause and effect diagram (also known as Ishikawa, tree diagram, and the fishbone diagram). Finally, Pareto diagrams were employed towards the optimization of GMOs detection potential of FMEA. PMID:17457722

Varzakas, Theodoros H; Arvanitoyannis, Ioannis S

2007-01-01

244

Involvement of ethylene biosynthesis and signalling in fruit set and early fruit development in zucchini squash (Cucurbita pepo L.)  

PubMed Central

Background We have identified a kind of parthenocarpy in zucchini squash which is associated with an incomplete andromonoecy, i.e. a partial conversion of female into bisexual flowers. Given that andromonoecy in this and other cucurbit species is caused by a reduction of ethylene production in the female flower, the associated parthenocarpic development of the fruit suggested the involvement of ethylene in fruit set and early fruit development. Results We have compared the production of ethylene as well as the expression of 13 ethylene biosynthesis and signalling genes in pollinated and unpollinated ovaries/fruits of two cultivars, one of which is parthenocarpic (Cavili), while the other is non-parthenocarpic (Tosca). In the latter, unpollinated ovaries show an induction of ethylene biosynthesis and ethylene signal transduction pathway genes three days after anthesis, which is concomitant with the initiation of fruit abortion and senescence. Fruit set and early fruit development in pollinated flowers of both cultivars and unpollinated flowers of Cavili is coupled with low ethylene biosynthesis and signalling, which would also explain the partial andromonoecy in the parthenocarpic genotype. The reduction of ethylene production in the ovary cosegregates with parthenocarpy and partial andromonoecy in the selfing progeny of Cavili. Moreover, the induction of ethylene in anthesis (by ethephon treatments) reduced the percentage of bisexual parthenocarpic flowers in Cavili, while the inhibition of ethylene biosynthesis or response (by AVG and STS treatments) induces not only andromonoecy but also the parthenocarpic development of the fruit in both cultivars. Conclusions Results demonstrate that a reduction of ethylene production or signalling in the zucchini flower is able to induce fruit set and early fruit development, and therefore that ethylene is actively involved in fruit set and early fruit development. Auxin and TIBA treatments, inducing fruit set and early fruit development in this species, also inhibit ethylene production and the expression of ethylene biosynthesis and response genes. A model is presented that discusses the crosstalk between ethylene and auxin in the control of fruit set and early fruit development in zucchini squash. PMID:24053311

2013-01-01

245

Population genetics of the wheat curl mite (Aceria tosichella Keifer) in Australia: implications for the management of wheat pathogens.  

PubMed

The wheat curl mite (WCM), Aceria tosichella Keifer, is a polyphagous eriophyoid mite and the primary vector of wheat streak mosaic virus (WSMV) and five other viral pathogens in cereals. Previous research using molecular markers and a series of laboratory experiments found A. tosichella in Australia to consist of two genetically distinct lineages, which have broad overlapping distributions and differ in their ability to transmit WSMV under controlled conditions. This pattern of transmission also appears to be apparent in the field, whereby a strong association between WSMV detection and a single WCM lineage has been detected. In this study, we conduct a population genetic analysis and provide information on the genetic structure of the Australian viruliferous WCM lineage. We assessed genetic differentiation of 16 WCM populations using nine microsatellite markers. Strong evidence for extensive gene flow and low genetic structuring throughout the Australian wheatbelt was evident, with an exception for Western Australian and far north Queensland populations that appear to be genetically isolated. The data also indicate genetic patterns consistent with an arrhenotokous parthenogenetic mode of reproduction. Implications of these findings are discussed with reference to the management of WCM and associated cereal pathogens in Australia and overseas. PMID:22030277

Miller, A D; Umina, P A; Weeks, A R; Hoffmann, A A

2012-04-01

246

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

247

Experiments in Whole Leaf Photosynthesis  

ERIC Educational Resources Information Center

Described is a simple experimental system, which uses radioactive carbon dioxide to study whole leaf photosynthesis under a variety of conditions. Other experiments and simple apparatus for the experiments are also described. (Author/RH)

Stewart, J. C.; And Others

1974-01-01

248

Why do leaf-tying caterpillars abandon their leaf ties?  

PubMed

Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm(2) leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf tie due to food limitation and interactions with other caterpillars, but this is a costly behavior. PMID:24109557

Sliwinski, Michelle; Sigmon, Elisha

2013-01-01

249

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

Microsoft Academic Search

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

Andrea Nardini; Sebastiano Salleo; Fabio Raimondo

2003-01-01

250

Root Growth Inhibition in Boron-Deficient or Aluminum-Stressed Squash May Be a Result of Impaired Ascorbate Metabolism.  

PubMed Central

Although cessation of growth is the most apparent symptom of boron deficiency, the biochemical function of boron in growth processes is not well understood. We propose that the action of boron in root meristems is associated with ascorbate metabolism. Total inhibition of root growth in squash (Cucurbita pepo L.) plants transferred to boron-free medium coincided with a major decrease (up to 98%) in the ascorbate concentration of root apices. Under low-boron conditions, in which root growth was partially inhibited, ascorbate concentration declined in proportion to growth rate. The decline in ascorbate concentration in boron-deficient root tips was not related to ascorbate oxidation. Ascorbate added to the medium improved root growth in plants supplied with insufficient boron. Increasing concentrations of aluminum in the nutrient medium caused progressive inhibition of root growth and a parallel reduction in ascorbate concentration of root apices. Elevated boron levels improved root growth under toxic aluminum conditions and produced root apices with higher ascorbate concentrations. To our knowledge, this is the first report of a correlation between boron nutrition, ascorbate concentration in root apices, and growth. These findings show that root growth inhibition resulting from either boron deficiency or aluminum toxicity may be a consequence of disrupted ascorbate metabolism. PMID:12226437

Lukaszewski, K. M.; Blevins, D. G.

1996-01-01

251

EXOTICPEST ALERT Horse chestnut leaf miner, Cameraria ohridella Desch. & Dem.  

E-print Network

together. This leads to browning and drying of the leaves, which eventually curl upwards and inwards, competition for space and food can be great and many larvae fail to survive. Life Cycle of Cameraria ohridella

252

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

253

Influence of cover crop and intercrop systems on Bemisia argentifolli (Hemiptera: Aleyrodidae) infestation and associated squash silverleaf disorder in zucchini.  

PubMed

Field experiments were conducted to evaluate the effects of cover cropping and intercropping on population densities of silverleaf whitefly, Bemisia argentifolli Bellow and Perring, and the incidence of squash silverleaf disorder (SSL) in zucchini, Cucurbita pepo L., in Oahu, HI. Two cover crops, buckwheat (BW), Fagopyrum esculentum Moench, and white clover (WC), Trifolium repens L., or sunn hemp (SH), Crotolaria juncea L., and an intercropped vegetable, okra, Abelmonchus esculentus L., were evaluated during the 2003, 2005, and 2006 growing seasons, respectively. Population densities of whiteflies and SSL severity varied during the three field experiments. In 2003, the severity of SSL and percentage of leaves displaying symptoms were significantly lower on zucchini plants in WC than BW plots throughout the crops' growth cycle. Additionally, the percentage of leaves per plant displaying SSL symptoms was significantly greater in bare-ground (BG) compared with the pooled BW and WC treatments on each inspection date. In 2005, zucchini intercropped with okra had lower numbers of adult whiteflies and resulted in significantly lower severity of SSL than pooled BW and WC treatments. During 2006, zucchini grown with SH had significantly lower numbers of all whitefly stages (i.e., egg, immature, and adult) and less SSL severity symptoms than BW. Despite these differences in whitefly numbers and SSL severity, marketable yields were not significantly lower in BW compared with WC or SH treatment plots during the study. The mechanisms underlying these results and the feasibility of using cover crops and intercrops to manage B. argentifolli and SSL are discussed. PMID:19389294

Manandhar, Roshan; Hooks, Cerruti R R; Wright, Mark G

2009-04-01

254

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 with directions for finding mean, median, and mode are given. 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.

Shodor

2012-04-02

255

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

256

7 CFR 29.1028 - Leaf.  

Code of Federal Regulations, 2010 CFR

...AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Flue-Cured Tobacco (u.s. Types 11, 12, 13, 14 and Foreign Type 92) § 29.1028 Leaf. Whole, unstemmed leaf....

2010-01-01

257

SHADE TREE LEAF SCORCH1  

Microsoft Academic Search

The term scorch is commonly used to describe foliar symptoms of marginal and interveinal dessication. A diversity of abiotic and biotic agents cause scorch symptoms in shade trees. Thus there are many physiologic and pathologic bases for leaf scorch. Little research has been performed to define these bases; however, recent research involving fastidious xylem-inhabiting bacteria (FXIB) in elm, sycamore, oak,

R. Hammerschlag; J. Sherald; S. Kostka

1983-01-01

258

Leaf Photosynthesis Under Drought Stress  

Microsoft Academic Search

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

Gabriel Cornic; Angelo Massacci

259

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

260

Tree branch angle: maximizing effective leaf area.  

PubMed

In a computer simulation of branching pattern and leaf cluster in Terminalia catappa, right and left branch angles were varied, and the effective leaf surface areas were calculated. Theoretical branch angles that result in maximum effective leaf area are close to the values observed in nature. PMID:17757590

Honda, H; Fisher, J B

1978-02-24

261

Tree Branch Angle: Maximizing Effective Leaf Area  

Microsoft Academic Search

In a computer simulation of branching pattern and leaf cluster in Terminalia catappa, right and left branch angles were varied, and the effective leaf surface areas were calculated. Theoretical branch angles that result in maximum effective leaf area are close to the values observed in nature.

Hisao Honda; Jack B. Fisher

1978-01-01

262

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

263

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

264

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

265

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

266

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

267

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

268

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

269

Leafing patterns and leaf traits of four evergreen shrubs in the Patagonian Monte, Argentina  

NASA Astrophysics Data System (ADS)

We assessed leafing patterns (rate, timing, and duration of leafing) and leaf traits (leaf longevity, leaf mass per area and leaf-chemistry) in four co-occurring evergreen shrubs of the genus Larrea and Chuquiraga (each having two species) in the arid Patagonian Monte of Argentina. We asked whether species with leaves well-defended against water shortage (high LMA, leaf longevity, and lignin concentration, and low N concentration) have lower leaf production, duration of the leafing period, and inter-annual variation of leafing than species with the opposite traits. We observed two distinctive leafing patterns each related to one genus. Chuquiraga species produced new leaves concentrated in a massive short leafing event (5-48 days) while new leaves of Larrea species emerged gradually (128-258 days). Observed leafing patterns were consistent with simultaneous and successive leafing types previously described for woody plants. The peak of leaf production occurred earlier in Chuquiraga species (mid September) than in Larrea species (mid October-late November). Moreover, Chuquiraga species displayed leaves with the longest leaf lifespan, while leaves of Larrea species had the lowest LMA and the highest N and soluble phenolics concentrations. We also observed that only the leaf production of Larrea species increased in humid years. We concluded that co-occurring evergreen species in the Patagonian Monte displayed different leafing patterns, which were associated with some relevant leaf traits acting as plant defenses against water stress and herbivores. Differences in leafing patterns could provide evidence of ecological differentiation among coexisting species of the same life form.

Campanella, María Victoria; Bertiller, Mónica B.

2009-11-01

270

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

271

Leaf surface flavonoids of Chrysothamnus  

Microsoft Academic Search

Twenty-six flavonoid aglycones have been identified from eight plants covering three species of Chrysothamnus that were collected in eastern Oregon. The flavonoids were identified by NMR spectroscopy, tandem mass spectrometry and co-TLC with authentic markers. Chrysothamnus nauseosus yielded methyl ethers of apigenin, isoscutellarein, luteolin, kaempferol, herbacetin and quercetin. O-Methylated kaempferol and quercetin derivatives were isolated from the leaf exudate of

Jan F Stevens; Eckhard Wollenweber; Monika Ivancic; Victor L Hsu; Scott Sundberg; Max L Deinzer

1999-01-01

272

LeafJ: an ImageJ plugin for semi-automated leaf shape measurement.  

PubMed

High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review and recent examples). 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 tools. 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). Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices. To date, leaf shape programs (e.g. SHAPE, LAMINA, LeafAnalyzer, LEAFPROCESSOR) 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 size. 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

Maloof, Julin N; Nozue, Kazunari; Mumbach, Maxwell R; Palmer, Christine M

2013-01-01

273

Leaf drop affects herbivory in oaks.  

PubMed

Leaf phenology is important to herbivores, but the timing and extent of leaf drop has not played an important role in our understanding of herbivore interactions with deciduous plants. Using phylogenetic general least squares regression, we compared the phenology of leaves of 55 oak species in a common garden with the abundance of leaf miners on those trees. Mine abundance was highest on trees with an intermediate leaf retention index, i.e. trees that lost most, but not all, of their leaves for 2-3 months. The leaves of more evergreen species were more heavily sclerotized, and sclerotized leaves accumulated fewer mines in the summer. Leaves of more deciduous species also accumulated fewer mines in the summer, and this was consistent with the idea that trees reduce overwintering herbivores by shedding leaves. Trees with a later leaf set and slower leaf maturation accumulated fewer herbivores. We propose that both leaf drop and early leaf phenology strongly affect herbivore abundance and select for differences in plant defense. Leaf drop may allow trees to dispose of their herbivores so that the herbivores must recolonize in spring, but trees with the longest leaf retention also have the greatest direct defenses against herbivores. PMID:23774946

Pearse, Ian S; Karban, Richard

2013-11-01

274

Classification and quantification of leaf curvature.  

PubMed

Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields. PMID:20400533

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

2010-06-01

275

Localization of Boron in Cell Walls of Squash and Tobacco and Its Association with Pectin (Evidence for a Structural Role of Boron in the Cell Wall).  

PubMed Central

B deficiency results in a rapid inhibition of plant growth, and yet the form and function of B in plants remains unclear. In this paper we provide evidence that B is chemically localized and structurally important in the cell wall of plants. The localization and chemical fractionation of B was followed in squash plants (Curcurbita pepo L.) and cultured tobacco cells (Nicotiana tabacum) grown in B-replete or B-deficient medium. As squash plants and cultured tobacco cells became deficient, an increasingly large proportion of cellular B was found to be localized in the cell wall. Cytoplasmic B concentrations were reduced to essentially zero as plants became deficient, whereas cell wall B concentration remained at or above 10 [mu]g B/g cell wall dry weight in all experiments. Chemical and enzymic fractionation studies suggest that the majority of cell B is associated with pectins within the cell wall. Physical analysis of B-deficient tissue indicates that cell wall plastic extensibility is greatly reduced under B deficiency, and anatomical observations indicate that B deficiency impairs normal cell elongation in growing plant tissue. In plants in which B deficiency had inhibited all plant growth, tissues remained green and did not show any additional visible symptoms for at least 1 week with no additional B. This occurred even though cytoplasmic B had been reduced to extremely low levels (<0.2 [mu]g/g). This suggests that B in these species is largely associated with the cell wall and that any cytoplasmic role for B is satisfied by very low concentrations of B. The localization of B in the cell wall, its association with cell wall pectins, and the contingent effects of B on cell wall extensibility suggest that B plays a critical, although poorly defined, role in the cell wall structure of higher plants. PMID:12232235

Hu, H.; Brown, P. H.

1994-01-01

276

Yield and leaf blade area comparisons of extra leafy to normal leafed maize (Zea mays L.)  

E-print Network

YIELD AND LEAF BLADE AREA COMPARISONS OF EXTRA LEAFY TO NORMAL LEAFED MAIZE ( Zea ~nays L. ) A Thesis RONALD WAYNE RUSHING Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1996 Major Subject: Plant Breeding YIELD AND LEAF BLADE AREA COMPARISONS OF EXTRA LEAFY TO NORMAL LEAFED MAIZE ( Zea mays L) A Thesis RONALD WAYNE RUSHING Submitted to Texas ASSAM University in partial...

Rushing, Ronald Wayne

2012-06-07

277

7 CFR 28.467 - Leaf Grade 7.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade 7. 28.467 Section 28.467 Agriculture...Standards of the United States for the Leaf Grade of American Upland Cotton § 28.467 Leaf Grade 7. Leaf Grade 7 is leaf which is...

2010-01-01

278

Foliage height influences specific leaf area of three conifer species  

Microsoft Academic Search

Specific leaf area (SLA), the ratio of projected leaf area to leaf dry mass, is a critical parameter in many forest process models. SLA describes the efficiency with which the leaf captures light relative to the biomass invested in the leaf. It increases from top to bottom of a canopy, but it is unclear why. We sampled stands with low

John D. Marshall; Robert A. Monserud

2003-01-01

279

Leaf-wax n-alkanes record the plantwater environment at leaf ush  

E-print Network

Leaf-wax n-alkanes record the plant­water environment at leaf ush Brett J. Tipple1 , Melissa A, UT, and approved December 26, 2012 (received for review August 13, 2012) Leaf-wax n-alkanes 2 H/1 H- ship between n-alkanes 2 H values and climate is appreciated, the quantitative details of the proxy

Tipple, Brett

280

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

Microsoft Academic Search

Leaf litter derived from riparian trees can control secondary production of detritivores in forested streams. Species-rich assemblages of leaf litter reflect riparian plant species richness and represent a heterogeneous resource for stream consumers. Such variation in resource quality may alter consumer growth and thus the feedback on leaf breakdown rate via changes in feeding activity. To assess the consequences of

Christopher M. Swan; Margaret A. Palmer

2006-01-01

281

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

Microsoft Academic Search

BACKGROUND: The leaf is an important plant organ, and how it will respond to future global warming is a question that remains unanswered. The effects of experimental warming on leaf photosynthesis and respiration acclimation has been well studied so far, but relatively little information exists on the structural and biochemical responses to warming. However, such information is very important to

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

2011-01-01

282

Influence of irradiation, soil water potential, and leaf temperature on leaf morphology of a desert broadleaf, Encelia farinosa Gray (Compositae)  

Microsoft Academic Search

Laboratory experiments were performed to evaluate observed seasonal changes in leaf morphology of the desert perennial shrub, Encelia farinosa Gray. Plants were grown under low or high conditions of photosynthetically active irradiation, soil water potential (Psi\\/sup soil\\/), and leaf temperature (8 different experimental regimes). The relative growth rate, leaf water vapor conductance, leaf water potential, and leaf length were all

William K. Smith; Park S. Nobel

1978-01-01

283

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

PubMed

"Microscopic leaf wetness" means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 ?m, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past. PMID:24167510

Burkhardt, Juergen; Hunsche, Mauricio

2013-01-01

284

Feeding behavior of leaf beetles (Coleoptera, Chrysomelidae)  

Microsoft Academic Search

The feeding behavior of adult leaf beetles (41 species from 18 genera and 8 subfamilies) was studied for the first time. Beetles\\u000a of the genera Chrysolina, Chrysomela, Cryptocephalus, Galeruca, Gastrophysa, Labidostomis, Leptinotarsa, Timarcha, and Cassida stigmatica gnaw a leaf from the edge, whereas the representatives of Donacia, Galerucella, Lema, Lilioceris, Oulema, Phyllobrotica, Plagiodera, Zeugophora, Hypocassida, and most species of Cassida

A. O. Bie?kowski

2010-01-01

285

7 CFR 29.3527 - Leaf structure.  

Code of Federal Regulations, 2013 CFR

...Types 35, 36, 37 and Foreign Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality, § 29.3586.) [30 FR 9207, July 23, 1965. Redesignated at 49 FR 16759, Apr. 20,...

2013-01-01

286

7 CFR 29.3035 - Leaf structure.  

...u.s. Type 31 and Foreign Type 93) § 29.3035 Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements of quality.) [24 FR 8771, Oct. 29, 1959. Redesignated at 49 FR 16758, Apr. 20,...

2014-01-01

287

7 CFR 29.1030 - Leaf structure.  

...11, 12, 13, 14 and Foreign Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality Chart.) [42 FR 21092, Apr. 25, 1977. Redesignated at 49 FR 16755, Apr. 20, 1984,...

2014-01-01

288

7 CFR 29.3527 - Leaf structure.  

Code of Federal Regulations, 2011 CFR

...Types 35, 36, 37 and Foreign Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality, § 29.3586.) [30 FR 9207, July 23, 1965. Redesignated at 49 FR 16759, Apr. 20,...

2011-01-01

289

7 CFR 29.1030 - Leaf structure.  

Code of Federal Regulations, 2011 CFR

...11, 12, 13, 14 and Foreign Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality Chart.) [42 FR 21092, Apr. 25, 1977. Redesignated at 49 FR 16755, Apr. 20, 1984,...

2011-01-01

290

7 CFR 29.2530 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2601.) [37 FR 13626, July 12, 1972. Redesignated at 49 FR 16757, Apr. 20,...

2010-01-01

291

7 CFR 29.2530 - Leaf structure.  

...Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2601.) [37 FR 13626, July 12, 1972. Redesignated at 49 FR 16757, Apr. 20,...

2014-01-01

292

7 CFR 29.3527 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...Types 35, 36, 37 and Foreign Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality, § 29.3586.) [30 FR 9207, July 23, 1965. Redesignated at 49 FR 16759, Apr. 20,...

2010-01-01

293

7 CFR 29.3527 - Leaf structure.  

Code of Federal Regulations, 2012 CFR

...Types 35, 36, 37 and Foreign Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality, § 29.3586.) [30 FR 9207, July 23, 1965. Redesignated at 49 FR 16759, Apr. 20,...

2012-01-01

294

7 CFR 29.2530 - Leaf structure.  

Code of Federal Regulations, 2011 CFR

...Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2601.) [37 FR 13626, July 12, 1972. Redesignated at 49 FR 16757, Apr. 20,...

2011-01-01

295

7 CFR 29.3035 - Leaf structure.  

Code of Federal Regulations, 2012 CFR

...u.s. Type 31 and Foreign Type 93) § 29.3035 Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements of quality.) [24 FR 8771, Oct. 29, 1959. Redesignated at 49 FR 16758, Apr. 20,...

2012-01-01

296

7 CFR 29.3035 - Leaf structure.  

Code of Federal Regulations, 2013 CFR

...u.s. Type 31 and Foreign Type 93) § 29.3035 Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements of quality.) [24 FR 8771, Oct. 29, 1959. Redesignated at 49 FR 16758, Apr. 20,...

2013-01-01

297

7 CFR 29.1030 - Leaf structure.  

Code of Federal Regulations, 2012 CFR

...11, 12, 13, 14 and Foreign Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality Chart.) [42 FR 21092, Apr. 25, 1977. Redesignated at 49 FR 16755, Apr. 20, 1984,...

2012-01-01

298

7 CFR 29.3035 - Leaf structure.  

Code of Federal Regulations, 2011 CFR

...u.s. Type 31 and Foreign Type 93) § 29.3035 Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements of quality.) [24 FR 8771, Oct. 29, 1959. Redesignated at 49 FR 16758, Apr. 20,...

2011-01-01

299

7 CFR 29.3527 - Leaf structure.  

...Types 35, 36, 37 and Foreign Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality, § 29.3586.) [30 FR 9207, July 23, 1965. Redesignated at 49 FR 16759, Apr. 20,...

2014-01-01

300

7 CFR 29.2530 - Leaf structure.  

Code of Federal Regulations, 2013 CFR

...Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2601.) [37 FR 13626, July 12, 1972. Redesignated at 49 FR 16757, Apr. 20,...

2013-01-01

301

7 CFR 29.1030 - Leaf structure.  

Code of Federal Regulations, 2013 CFR

...11, 12, 13, 14 and Foreign Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality Chart.) [42 FR 21092, Apr. 25, 1977. Redesignated at 49 FR 16755, Apr. 20, 1984,...

2013-01-01

302

7 CFR 29.2530 - Leaf structure.  

Code of Federal Regulations, 2012 CFR

...Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2601.) [37 FR 13626, July 12, 1972. Redesignated at 49 FR 16757, Apr. 20,...

2012-01-01

303

7 CFR 29.3035 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...u.s. Type 31 and Foreign Type 93) § 29.3035 Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements of quality.) [24 FR 8771, Oct. 29, 1959. Redesignated at 49 FR 16758, Apr. 20,...

2010-01-01

304

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

2011-01-01

305

7 CFR 28.471 - Below Leaf Grade Cotton.  

...2014-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

2014-01-01

306

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2013 CFR

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

2013-01-01

307

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

2012-01-01

308

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 1–2 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 (µg 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

309

Nutrient Influences on Leaf Photosynthesis  

PubMed Central

The net rate of CO2 uptake for leaves of Gossypium hirsutum L. was reduced when the plants were grown at low concentrations of NO3-, PO42-, or K+. The water vapor conductance was relatively constant for all nutrient levels, indicating little effect on stomatal response. Although leaves under nutrient stress tended to be lower in chlorophyll and thinner, the ratio of mesophyll surface area to leaf area did not change appreciably. Thus, the reduction in CO2 uptake rate at low nutrient levels was due to a decrease in the CO2 conductance expressed per unit mesophyll cell wall area (gcellCO2). The use of gcellCO2 and nutrient levels expressed per unit of mesophyll cell wall provides a new means of assessing nutrient effects on CO2 uptake of leaves. PMID:16661231

Longstreth, David J.; Nobel, Park S.

1980-01-01

310

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

PubMed

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

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

2013-05-10

311

Key Proliferative Activity in the Junction between the Leaf Blade and Leaf Petiole of Arabidopsis1[W][OA  

PubMed Central

Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a leaf is clearly divided into the leaf blade and leaf petiole, no study has yet revealed how these are differentiated from a leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the leaf blade and leaf petiole and produces both leaf-blade and leaf-petiole cells. This proliferative region in leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and blade-on-petiole mutations further support the idea that organogenesis of the leaf blade and leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of leaf primordia. Thus, the proliferative zone of leaf primordia is spatially differentiated and supplies both the leaf-blade and leaf-petiole cells. PMID:21880932

Ichihashi, Yasunori; Kawade, Kensuke; Usami, Takeshi; Horiguchi, Gorou; Takahashi, Taku; Tsukaya, Hirokazu

2011-01-01

312

Short communication Leaf optical properties and photosynthetic leaf absorptances in several Australian seagrasses  

Microsoft Academic Search

Thisstudyinvestigated within-and among-species variability intheleafoptical properties ofeightlarge-bodiedseagrasses,Posidoniaaustralis, Posidonia sinuosa, Posidonia coriacea, Posidonia angustifolia, Amphibolis antarctica, Amphibolis griffithii, Zostera tasmanica, and Zostera capricorni and the small-bodied Halophila ovalis from the east and west coasts of Australia. Leaf spectral transmittance (TL(l)), reflectance (RL(l)), and non-photosynthetic absorptance (AL(NP)) were measured in order to calculate leaf spectral absorptance (AL(l)) and photosynthetic leaf absorptance (AL(PAR)).

Michael J. Durako

313

Animal behaviour Ancient death-grip leaf  

E-print Network

Ophiocordyceps unilateralis. In this system, ants attach to major leaf veins along their abaxial surface in a similar manner to O. unilateralis [5] and so this type of manipulation is a probable candi- date

314

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes...semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings, trimmings, shorts, or...

2010-01-01

315

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2011 CFR

...COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes...semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings, trimmings, shorts, or...

2011-01-01

316

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2012 CFR

...COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes...semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings, trimmings, shorts, or...

2012-01-01

317

7 CFR 29.1029 - Leaf scrap.  

Code of Federal Regulations, 2010 CFR

...AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Flue-Cured Tobacco (u.s. Types 11, 12, 13, 14 and Foreign Type 92) § 29.1029 Leaf scrap. A byproduct of...

2010-01-01

318

7 CFR 29.1030 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Flue-Cured Tobacco (u.s. Types 11, 12, 13, 14 and Foreign Type 92) § 29.1030 Leaf structure. The cell...

2010-01-01

319

Interaction between photons and leaf canopies  

NASA Technical Reports Server (NTRS)

The physics of neutral particle interaction for photons traveling in media consisting of finite-dimensional scattering centers that cross-shade mutually is investigated. A leaf canopy is a typical example of such media. The leaf canopy is idealized as a binary medium consisting of randomly distributed gaps (voids) and regions with phytoelements (turbid phytomedium). In this approach, the leaf canopy is represented by a combination of all possible open oriented spheres. The mathematical approach for characterizing the structure of the host medium is considered. The extinction coefficient at any phase-space location in a leaf canopy is the product of the extinction coefficient in the turbid phytomedium and the probability of absence gaps at that location. Using a similar approach, an expression for the differential scattering coefficient is derived.

Knyazikhin, Yuri V.; Marshak, Alexander L.; Myneni, Ranga B.

1991-01-01

320

The red edge of plant leaf reflectance  

NASA Technical Reports Server (NTRS)

A detailed study of the red edge spectral feature of green vegetation based on laboratory reflectance spectrophotometry is presented. A parameter lambda is defined as the wavelength is defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration. Species, development stage, leaf layering, and leaf water content of vegetation also influences lambda. The maximum slope parameter is found to be independent of simulated ground area coverage. The results are interpreted in terms of Beer's Law and Kubelka-Munk theory. The chlorophyll concentration dependence of lambda seems to be explained in terms of a pure absorption effect, and it is suggested that the existence of two lambda components arises from leaf scattering properties. The results indicate that red edge measurements will be valuable for assessment of vegetative chlorophyll status and leaf area index independently of ground cover variations, and will be particularly suitable for early stress detection.

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

1983-01-01

321

Coca leaf as a therapeutic agent.  

PubMed

South American Indians have used coca leaf as a remedy for thousands of years. Coca might be useful as a treatment for gastrointestinal ailments and motion sickness, as a fast-acting antidepressant medication, as a substitute stimulant for coffee in certain cases, and as an adjunct in programs of weight reduction and physical fitness. In leaf form, coca does not produce toxicity or dependence. Its effects are distinct from those of cocaine, which is but one of a number of active compounds in the leaf. Coca can be administered as a chewing gum containing a whole extract of the leaf, including alkaloids, natural flavors, and several nutrients. Legal mechanisms exist for importing, distributing, and dispensing coca, and experimentation with it by interested physicians would be valuable. PMID:696708

Weil, A T

1978-01-01

322

Reflectance model of a plant leaf  

NASA Technical Reports Server (NTRS)

A light ray, incident at 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's Equations and Snell's Law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A Spectroreflectometer. Similarly a light ray, incident at about 60 deg to the normal, is drawn through the palisade cells of a soybean leaf to illustrate the pathway of light, incident at an oblique angle, through the palisade cells.

Kumar, R.; Silva, L.

1973-01-01

323

7 CFR 29.1163 - Smoking Leaf (H Group).  

...2014-01-01 2014-01-01 false Smoking Leaf (H Group). 29.1163 Section...INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group...Tolerances H3F—Good Quality Orange Smoking Leaf Mellow, open leaf...

2014-01-01

324

7 CFR 29.1163 - Smoking Leaf (H Group).  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Smoking Leaf (H Group). 29.1163 Section...INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group...Tolerances H3F—Good Quality Orange Smoking Leaf Mellow, open leaf...

2013-01-01

325

7 CFR 29.1163 - Smoking Leaf (H Group).  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Smoking Leaf (H Group). 29.1163 Section...INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group...Tolerances H3F—Good Quality Orange Smoking Leaf Mellow, open leaf...

2010-01-01

326

7 CFR 29.1163 - Smoking Leaf (H Group).  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Smoking Leaf (H Group). 29.1163 Section...INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group...Tolerances H3F—Good Quality Orange Smoking Leaf Mellow, open leaf...

2012-01-01

327

7 CFR 29.1163 - Smoking Leaf (H Group).  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Smoking Leaf (H Group). 29.1163 Section...INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group...Tolerances H3F—Good Quality Orange Smoking Leaf Mellow, open leaf...

2011-01-01

328

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 Agriculture...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2010-01-01

329

7 CFR 28.514 - Leaf Grade No. 4.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade No. 4. 28.514 Section 28.514 Agriculture...Standards of the United States for the Leaf Grade of American Pima Cotton § 28.514 Leaf Grade No. 4. Leaf grade No. 4 shall be...

2010-01-01

330

7 CFR 28.512 - Leaf Grade No. 2.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade No. 2. 28.512 Section 28.512 Agriculture...Standards of the United States for the Leaf Grade of American Pima Cotton § 28.512 Leaf Grade No. 2. Leaf grade No. 2 shall be...

2010-01-01

331

7 CFR 28.515 - Leaf Grade No. 5.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade No. 5. 28.515 Section 28.515 Agriculture...Standards of the United States for the Leaf Grade of American Pima Cotton § 28.515 Leaf Grade No. 5. Leaf grade No. 5 shall be...

2010-01-01

332

7 CFR 28.516 - Leaf Grade No. 6.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade No. 6. 28.516 Section 28.516 Agriculture...Standards of the United States for the Leaf Grade of American Pima Cotton § 28.516 Leaf Grade No. 6. Leaf grade No. 6 shall be...

2010-01-01

333

7 CFR 28.511 - Leaf Grade No. 1.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade No. 1. 28.511 Section 28.511 Agriculture...Standards of the United States for the Leaf Grade of American Pima Cotton § 28.511 Leaf Grade No. 1. Leaf grade No. 1 shall be...

2010-01-01

334

ORIGINAL PAPER Leaf shape variation and herbivore consumption  

E-print Network

ORIGINAL PAPER Leaf shape variation and herbivore consumption and performance: a case study online: 9 January 2008 Ã? Springer Science+Business Media B.V. 2008 Abstract The effect of leaf shape of leaf shape variation on herbivore consumption and performance. We investigated whether alternative leaf

Stinchcombe, John

335

What Is a Leaf? An Online Tutorial and Tests  

ERIC Educational Resources Information Center

A leaf is a fundamental unit in botany and understanding what constitutes a leaf is fundamental to many plant science activities. My observations and subsequent testing indicated that many students could not confidently and consistently recognise a leaf from a leaflet, or recognise basic leaf arrangements and the various types of compound or…

Burrows, Geoffrey

2008-01-01

336

Antibacterial activity on Citrullus colocynthis Leaf extract.  

PubMed

Studies on the antibacterial activities of the leaf extract of Citrullus colocynthis (Cucurbitaceae), a medicinal plant used for the treatment of various ailments was carried out using agar disc diffusion technique. The results revealed that the crude acetone extract exhibited antibacterial activities against Pseudomonas aeruginosa with zones of inhibition measuring 14.0mm. The chloroform leaf extract exhibited no antibacterial activity against Staphylococcus aureus. The minimum inhibitory concentration for the chloroform extract was 4.0mm for Escherichia coli. PMID:22557336

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

2009-07-01

337

Synthesis of single and multi unit-wall MgB2 nanotubes by arc plasma in inert liquid via self-curling mechanism  

NASA Astrophysics Data System (ADS)

Magnesium diboride (MgB2) is known as a promising superconductor due to its high transmission temperature. Similarly to single-wall carbon nanotube, unique characteristics would be seen if a nanotube structure of MgB2 having a unit-wall of Mg and B atomic bilayer is prepared. However, such MgB2 nanotubes have not ever been synthesized. In this article, formation mechanism of unit-wall MgB2 nanotube is elucidated by molecular mechanics calculation. From the viewpoint of energetic stability, the unit-wall will be curled up to form nanotube structure when MgB2 crystal is disassembled to an isolated unit-wall layer. An experiment using arc plasma in inert liquid was utilized to produce unit-wall MgB2 nanotubes. As a result, a single and multiunit-wall MgB2 nanotube was successfully synthesized. In this reaction field, the arc plasma may play a role to produce isolated MgB2 unit-wall fragment, and the cold cathode surface can contribute to preserve MgB2 nanotube structure.

Sano, Noriaki; Kawanami, Osamu; Tamon, Hajime

2011-02-01

338

Vegetative Development: Total Leaf Area and Surface Area Indexes  

Microsoft Academic Search

\\u000a Canopy management determines canopy shape and spatial leaf area distribution which in turn determines vineyard productivity.\\u000a There are two indexes evaluating vineyard productivity which involve leaf development: total leaf area – LAI – and external\\u000a leaf area – SA –. The first one refers to total leaf area developed per m2 of soil while SA refers to the external leaves,

Patricia Sánchez-de-Miguel; Pilar Baeza; Pedro Junquera; José Ramón Lissarrague

339

Effects of crown development on leaf irradiance, leaf morphology and photosynthetic capacity in a peach tree.  

PubMed

The three-dimensional (3-D) architecture of a peach tree (Prunus persica L. Batsch) growing in an orchard near Avignon, France, was digitized in April 1999 and again four weeks later in May 1999 to quantify increases in leaf area and crown volume as shoots developed. A 3-D model of radiation transfer was used to determine effects of changes in leaf area density and canopy volume on the spatial distribution of absorbed quantum irradiance (PAR(a)). Effects of changes in PAR(a) on leaf morphological and physiological properties were determined. Leaf mass per unit area (M(a)) and leaf nitrogen concentration per unit leaf area (N(a)) were both nonlinearly related to PAR(a), and there was a weak linear relationship between leaf nitrogen concentration per unit leaf mass (N(m)) and PAR(a). Photosynthetic capacity, defined as maximal rates of ribulose-1,5-bisphosphate carboxylase (Rubisco) carboxylation (V(cmax)) and electron transport (J(max)), was measured on leaf samples representing sunlit and shaded micro-environments at the same time that the tree crown was digitized. Both V(cmax) and J(max) were linearly related to N(a) during May, but not in April when the range of N(a) was low. Photosynthetic capacity per unit N(a) appeared to decline between April and May. Variability in leaf nitrogen partitioning between Rubisco carboxylation and electron transport was small, and the partitioning coefficients were unrelated to N(a). Spatial variability in photosynthetic capacity resulted from acclimation to varying PAR(a) as the crown developed, and acclimation was driven principally by changes in M(a) rather than the amount or partitioning of leaf nitrogen. PMID:12204849

Walcroft, Adrian; Le Roux, Xavier; Diaz-Espejo, Antonio; Dones, Nicolas; Sinoquet, Hervé

2002-09-01

340

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

NASA Astrophysics Data System (ADS)

A large increase in near-infrared (NIR) reflectance of Amazon forests during the light-rich dry season and a corresponding decrease during the light-poor wet season has been observed in satellite measurements. This increase has been variously interpreted as seasonal change in leaf area resulting from net leaf flushing in the dry season or net leaf abscission in the wet season, enhanced photosynthetic activity during the dry season from flushing new leaves and as change in leaf scattering and absorption properties between younger and older leaves covered with epiphylls. Reconciling these divergent views using theory and observations is the goal of this article. The observed changes in NIR reflectance of Amazon forests could be due to similar, but small, changes in NIR leaf albedo (reflectance plus transmittance) resulting from the exchange of older leaves for newer ones, but with the total leaf area unchanged. However, this argument ignores accumulating evidence from ground-based reports of higher leaf area in the dry season than the wet season, seasonal changes in litterfall and does not satisfactorily explain why NIR reflectance of these forests decreases in the wet season. More plausibly, the increase in NIR reflectance during the dry season and the decrease during the wet season would result from changes in both leaf area and leaf optical properties. Such change would be consistent with known phenological behavior of tropical forests, ground-based reports of seasonal changes in leaf area, litterfall, leaf optical properties and fluxes of evapotranspiration, and thus, would reconcile the various seemingly divergent views.

Samanta, Arindam; Knyazikhin, Yuri; Xu, Liang; Dickinson, Robert E.; Fu, Rong; Costa, Marcos H.; Saatchi, Sassan S.; Nemani, Ramakrishna R.; Myneni, Ranga B.

2012-03-01

341

Effects of leaf-transmittance versus leaf-reflectance on bidirectional scattering from canopy\\/soil surface: An analytical study  

Microsoft Academic Search

A simple single-scattering model for a surface with sparse ereetophile plants is developed as a plane-parallel canopy consisting of small leaves (relative to leaf-to-leaf spacing) with a spherical-shell distribution of the leaf area. The contributions to the overall surface reflectance in the visible spectral bands by the soil-reflectance, leaf-reflection, and leaf-transmission (which are assumed isotropic) are analyzed under different view\\/illumination

J. Otterman; T. Brakke; J. Smith

1995-01-01

342

Coming of leaf age: control of growth by hydraulics and metabolics during leaf ontogeny.  

PubMed

Leaf growth is the central process facilitating energy capture and plant performance. This is also one of the most sensitive processes to a wide range of abiotic stresses. Because hydraulics and metabolics are two major determinants of expansive growth (volumetric increase) and structural growth (dry matter increase), we review the interaction nodes between water and carbon. We detail the crosstalks between water and carbon transports, including the dual role of stomata and aquaporins in regulating water and carbon fluxes, the coupling between phloem and xylem, the interactions between leaf water relations and photosynthetic capacity, the links between Lockhart's hydromechanical model and carbon metabolism, and the central regulatory role of abscisic acid. Then, we argue that during leaf ontogeny, these interactions change dramatically because of uncoupled modifications between several anatomical and physiological features of the leaf. We conclude that the control of leaf growth switches from a metabolic to a hydromechanical limitation during the course of leaf ontogeny. Finally, we illustrate how taking leaf ontogeny into account provides insights into the mechanisms underlying leaf growth responses to abiotic stresses that affect water and carbon relations, such as elevated CO2, low light, high temperature and drought. PMID:22924516

Pantin, Florent; Simonneau, Thierry; Muller, Bertrand

2012-10-01

343

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

344

Leaf alkaloids, phenolics, and coffee resistance to the leaf miner Leucoptera coffeella (Lepidoptera: Lyonetiidae).  

PubMed

Coffee (Coffea spp.) alkaloids (caffeine and related methylxanthines) and phenolics (caffeic and chlorogenic acids) have recognized pestistatic/pesticidal activity and mediate insect-plant interactions. The present investigation assessed the resistance of 12 coffee genotypes to the leaf miner Leucoptera (= Perileucoptera) coffeella (Guérin-Méneville & Perrottet) (Lepidoptera: Lyonetiidae) and correlated such results with the leaf content of coffee alkaloids and phenolics that probably play a role in the interaction between coffee and this leaf miner. The levels of chlorogenic and caffeic acid, caffeine, and related methylxanthines were measured and quantified in leaf extracts of these genotypes before and 7 d after their infestation by the leaf miner. Some coffee genotypes (Coffea canephora L. and Coffea racemosa Lour. and its hybrids with Coffea arabica L.) exhibited high pesticidal activity (100% mortality) toward the L. coffeella, indicating their antibiosis resistance. However, there was no correlation between this activity and the leaf levels of coffee alkaloids and phenolics. Curiously, infestation by L. coffeella leads to a nearly four-fold decline in the leaf levels of chlorogenic acid, which does not affect this pest species but may affect other generalist species. Indeed, chlorogenic acid sprayed on coffee leaves stimulated locomotory activity of the green scale Coccus viridis (Green) (Hemiptera: Coccidae), thus minimizing their feeding in contrast with the absence of this polyphenol. Therefore, reduction of chlorogenic acid levels in coffee leaves due to leaf miner infestation seems to also favor infestation by generalist insects, such as the green scale. PMID:20857759

Magalhães, S T V; Fernandes, F L; Demuner, A J; Picanço, M C; Guedes, R N C

2010-08-01

345

The prediction of rice leaf's nitrogen content based on leaf spectrum on the heading stage  

Microsoft Academic Search

The change of crops' nitrogen content can cause the surface of crop leaf and the physiological characteristics of the internal organization to change, thus can cause the spectrum reflection characteristic of the crop leaf to change. In this paper, the amount of fertilizer was controlled, and nitrogen-containing samples of the rice cultivation experiment was conducted to study the relevant relations

Sun Jun; Lu Bing; Wu Xiaohong

2010-01-01

346

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 of Amazon forests during the light-rich dry season and a corresponding decrease during the light-poor wet season has been observed in satellite measurements. This increase has been variously interpreted

Goldberg, Bennett

347

In vitro response of leaf tissues from Lolium multiflorum — a comparison with leaf segment position, leaf age and in vivo mitotic activity  

Microsoft Academic Search

Immature gramineous leaves provide a convenient system for comparing the response of cells in culture with their state of differentiation. Callusing frequency is compared with leaf segment position, leaf age and in vivo mitotic activity in Lolium multiflorum. (1) In a succession of one millimeter sections from the immature leaf base, callus was formed from the first and second sections

O. I. Joarder; N. H. Joarder; P. J. Dale

1986-01-01

348

How do leaf veins influence the worldwide leaf economic spectrum? Review and synthesis.  

PubMed

Leaf vein traits are implicated in the determination of gas exchange rates and plant performance. These traits are increasingly considered as causal factors affecting the 'leaf economic spectrum' (LES), which includes the light-saturated rate of photosynthesis, dark respiration, foliar nitrogen concentration, leaf dry mass per area (LMA) and leaf longevity. This article reviews the support for two contrasting hypotheses regarding a key vein trait, vein length per unit leaf area (VLA). Recently, Blonder et al. (2011, 2013) proposed that vein traits, including VLA, can be described as the 'origin' of the LES by structurally determining LMA and leaf thickness, and thereby vein traits would predict LES traits according to specific equations. Careful re-examination of leaf anatomy, published datasets, and a newly compiled global database for diverse species did not support the 'vein origin' hypothesis, and moreover showed that the apparent power of those equations to predict LES traits arose from circularity. This review provides a 'flux trait network' hypothesis for the effects of vein traits on the LES and on plant performance, based on a synthesis of the previous literature. According to this hypothesis, VLA, while virtually independent of LMA, strongly influences hydraulic conductance, and thus stomatal conductance and photosynthetic rate. We also review (i) the specific physiological roles of VLA; (ii) the role of leaf major veins in influencing LES traits; and (iii) the role of VLA in determining photosynthetic rate per leaf dry mass and plant relative growth rate. A clear understanding of leaf vein traits provides a new perspective on plant function independently of the LES and can enhance the ability to explain and predict whole plant performance under dynamic conditions, with applications towards breeding improved crop varieties. PMID:24123455

Sack, Lawren; Scoffoni, Christine; John, Grace P; Poorter, Hendrik; Mason, Chase M; Mendez-Alonzo, Rodrigo; Donovan, Lisa A

2013-10-01

349

Measurement of leaf relative water content by infrared reflectance  

NASA Technical Reports Server (NTRS)

From basic considerations and Beer's law, a leaf water content index incorporating reflectances of wavelengths from 0.76 to 0.90 microns and from 1.55 to 1.75 microns was developed that relates leaf reflectance to leaf relative water content. For the leaf succulent, Agave deserti, the leaf water content index was not significantly different from the relative water content for either individual leaves or an entire plant. Also, the relative water contents of intact plants of Encelia farinosa and Hilaria rigida in the field were estimated by the leaf water content index; variations in the proportion of living to dead leaf area could cause large errors in the estimate of relative water content. Thus, the leaf water content index may be able to estimate average relative water content of canopies when TM4 and TM5 are measured at a known relative water content and fraction of dead leaf material.

Hunt, E. Raymond, Jr.; Rock, Barrett N.; Nobel, Park S.

1987-01-01

350

Leaf allometry of Salix viminalis during the first growing season.  

PubMed

We established linear and exponential relationships between leaf area (A) and leaf length (L), leaf width (W), W(2), L(2) and LW, in Salix viminalis L. Most relationships were significantly nonlinear, but good fits were obtained with both linear and exponential models. The nonlinear relationship between A and LW differed for leaves from sylleptic and proleptic shoots. Leaves from sylleptic and proleptic shoots also differed in specific leaf area (area/weight). Leaf shape (width/length ratio and position of maximum leaf width) changed with leaf size and differed for leaves from sylleptic and proleptic shoots. Leaf area could be modeled adequately using implicit shape descriptions. A good fit was obtained when the basal and distal parts of the leaf were described as a parabola and an ellipse, respectively. The average area of single leaves and specific leaf area increased both along vertical profiles within shoots and during the growing period. Our results (1) indicate that nonlinear models should be used to estimate leaf area from linear leaf dimensions for plant species with leaves that vary in shape with leaf size, and (2) demonstrate the dependence of leaf characteristics on both sampling date during the growing season and spatial position in the canopy. PMID:14871704

Verwijst, T; Wen, D Z

1996-07-01

351

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

352

Mueller matrix of a dicot leaf  

NASA Astrophysics Data System (ADS)

A better understanding of the information contained in the spectral, polarized bidirectional reflectance and transmittance of leaves may lead to improved techniques for identifying plant species in remotely sensed imagery as well as better estimates of plant moisture and nutritional status. Here we report an investigation of the optical polarizing properties of several leaves of one species, Cannabis sativa, represented by a 3x3 Mueller matrix measured over the wavelength region 400-2,400 nm. Our results support the hypothesis that the leaf surface alters the polarization of incident light - polarizing off nadir, unpolarized incident light, for example - while the leaf volume tends to depolarized incident polarized light.

Vanderbilt, Vern C.; Daughtry, Craig S. T.

2012-06-01

353

Is leaf dry matter content a better predictor of soil fertility than specific leaf area?  

PubMed Central

Background and Aims Specific leaf area (SLA), a key element of the ‘worldwide leaf economics spectrum’, is the preferred ‘soft’ plant trait for assessing soil fertility. SLA is a function of leaf dry matter content (LDMC) and leaf thickness (LT). The first, LDMC, defines leaf construction costs and can be used instead of SLA. However, LT identifies shade at its lowest extreme and succulence at its highest, and is not related to soil fertility. Why then is SLA more frequently used as a predictor of soil fertility than LDMC? Methods SLA, LDMC and LT were measured and leaf density (LD) estimated for almost 2000 species, and the capacity of LD to predict LDMC was examined, as was the relative contribution of LDMC and LT to the expression of SLA. Subsequently, the relationships between SLA, LDMC and LT with respect to soil fertility and shade were described. Key Results Although LD is strongly related to LDMC, and LDMC and LT each contribute equally to the expression of SLA, the exact relationships differ between ecological groupings. LDMC predicts leaf nitrogen content and soil fertility but, because LT primarily varies with light intensity, SLA increases in response to both increased shade and increased fertility. Conclusions Gradients of soil fertility are frequently also gradients of biomass accumulation with reduced irradiance lower in the canopy. Therefore, SLA, which includes both fertility and shade components, may often discriminate better between communities or treatments than LDMC. However, LDMC should always be the preferred trait for assessing gradients of soil fertility uncoupled from shade. Nevertheless, because leaves multitask, individual leaf traits do not necessarily exhibit exact functional equivalence between species. In consequence, rather than using a single stand-alone predictor, multivariate analyses using several leaf traits is recommended. PMID:21948627

Hodgson, J. G.; Montserrat-Martí, G.; Charles, M.; Jones, G.; Wilson, P.; Shipley, B.; Sharafi, M.; Cerabolini, B. E. L.; Cornelissen, J. H. C.; Band, S. R.; Bogard, A.; Castro-Díez, P.; Guerrero-Campo, J.; Palmer, C.; Pérez-Rontomé, M. C.; Carter, G.; Hynd, A.; Romo-Díez, A.; de Torres Espuny, L.; Royo Pla, F.

2011-01-01

354

Leaf-level nitrogen use efficiency: definition and importance.  

PubMed

Nitrogen use efficiency (NUE) has been widely used to study the relationship between nitrogen uptake and dry mass production in the plant. As a subsystem of plant nitrogen use efficiency (NUE), I have defined leaf-level NUE as the surplus production (gross production minus leaf respiration) per unit amount of nitrogen allocated to the leaf, with factorization into leaf nitrogen productivity (NP) and mean residence time of leaf nitrogen (MRT). These concepts were applied to two herbaceous stands: a perennial Solidago altissima stand and an annual Amaranthus patulus stand. S. altissima had more than three times higher leaf NUE than A. patulus due to nearly three times longer MRT of leaf N. In both species, NUE and NP were higher at the leaf level than at the plant level, because most leaf N is involved directly in the photosynthetic activity and because leaf surplus production is higher than the plant net production. MRT was longer at the plant level. The more than twice as long MRT at the plant level as at the leaf level in S. altissima was due to a large contribution of nitrogen storage belowground in the winter in this species. Thus, comparisons between a perennial and an annual system and between plant- and leaf-level NUE with their components revealed the importance of N allocation, storage, recycling, and turnover of organs for leaf photosynthetic production and plant dry mass growth. PMID:22179330

Hirose, Tadaki

2012-07-01

355

9 CFR 319.702 - Lard, leaf lard.  

Code of Federal Regulations, 2012 CFR

...result in the adulteration or misbranding of the lard. The tissues shall be reasonably free from blood, and shall not include stomachs, livers, spleens, kidneys, and brains, or settlings and skimmings. “Leaf Lard” is lard prepared from fresh leaf...

2012-01-01

356

9 CFR 319.702 - Lard, leaf lard.  

Code of Federal Regulations, 2013 CFR

...result in the adulteration or misbranding of the lard. The tissues shall be reasonably free from blood, and shall not include stomachs, livers, spleens, kidneys, and brains, or settlings and skimmings. “Leaf Lard” is lard prepared from fresh leaf...

2013-01-01

357

7 CFR 51.1220 - Leaf or limb rub injury.  

Code of Federal Regulations, 2011 CFR

...VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Peaches Definitions § 51.1220 Leaf or limb rub injury. “Leaf or limb rub injury” means that the scarring is not...

2011-01-01

358

7 CFR 51.1220 - Leaf or limb rub injury.  

Code of Federal Regulations, 2010 CFR

...VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Peaches Definitions § 51.1220 Leaf or limb rub injury. “Leaf or limb rub injury” means that the scarring is not...

2010-01-01

359

DIGITAL IMAGE ANALYSIS OF ZOSTERA MARINA LEAF INJURY  

EPA Science Inventory

Current methods for assessing leaf injury in Zostera marina (eelgrass) utilize subjective indexes for desiccation injury and wasting disease. Because of the subjective nature of these measures, they are inherently imprecise making them difficult to use in quantifying complex leaf...

360

Microsoft PowerPoint - Leaf BRN09 POWERPOINT  

Cancer.gov

Oncology Recapitulates Oncology Recapitulates Phylogeny Phylogeny 2 2 nd nd Annual BRN Symposium Annual BRN Symposium March 17, 2009 March 17, 2009 Clifton Leaf Clifton Leaf Dinosaur cladogram The branching of amniotes Onward to mammals . . . And so

361

From Individual Leaf Elongation to Whole Shoot Leaf Area Expansion: a Comparison of Three Aegilops and Two Triticum Species  

PubMed Central

• Background and Aims Rapid leaf area expansion is a desirable trait in the early growth stages of cereal crops grown in low?rainfall areas. In this study, the traits associated with inherent variation in early leaf area expansion rates have been investigated in two wheat species (Triticum aestivum and T. durum) and three of its wild relatives (Aegilops umbellulata, A. caudata and A. tauschii) to find out whether the Aegilops species have a faster leaf area expansion in their early developmental stage than some of the current wheat species. • Methods Growth of individual leaves, biomass allocation, and gas exchange were measured on hydroponically grown plants for 4 weeks. • Key Results Leaf elongation rate (LER) was strongly and positively correlated with leaf width but not with leaf elongation duration (LED). The species with more rapidly elongating leaves showed a faster increase with leaf position in LER, leaf width and leaf area, higher relative leaf area expansion rates, and more biomass allocation to leaf sheaths and less to roots. No differences in leaf appearance rate were found amongst the species. • Conclusions Aegilops tauschii was the only wild species with rapid leaf expansion rates similar to those of wheat, and it achieved the highest photosynthetic rates, making it an interesting species for further study. PMID:15155374

BULTYNCK, LIEVE; TER STEEGE, MARGREET W.; SCHORTEMEYER, MARCUS; POOT, PIETER; LAMBERS, HANS

2004-01-01

362

Pharmacognostic evaluation of Cayratia trifolia (Linn.) leaf  

PubMed Central

Objective To present a detailed pharmacognostic study of the leaf of Cayratia trifolia (C. trifolia) Linn. (Vitaceae), an important plant in the Indian system of medicine. Methods The macroscopy, microscopy, physiochemical analysis, preliminary testing, fluorescence analysis of powder of the plant and other WHO recommended methods for standardization were investigated. Results Leaves are trifoliolated with petioles (2–3 cm) long. Leaflets are ovate to oblong-ovate, (2–8 cm) long, (1.5–5 cm) wide, pointed at the tip. The leaf surface shows the anisocytic type stomata covered with guard cells followed by epidermis layer. Leaf surface contents including veins, vein islet and vein termination were also determined. Transverse section of leaf shows the epidermis layer followed by cuticle layer and vascular bandles (xylem and phloem). The mesophyll is differentiated into palisade and spongy parenchyma. Abundant covering trichomes emerge from the upper epidermis. Trichomes are uniseriate and multicellular. Strips of collenchyma are present below and upper layer of epidermis. Conclusions It can be concluded that the pharmacognostic profile of the C. trifolia is helpful in developing standards for quality, purity and sample identification. PMID:23569825

Kumar, Dinesh; Gupta, Jyoti; Kumar, Sunil; Arya, Renu; Kumar, Tarun; Gupta, Ankit

2012-01-01

363

Deferral of Leaf Senescence with Calcium 1  

PubMed Central

In view of the possibility that senescence may be a consequence of the deterioration of membrane compartments in the cells of leaves, calcium was studied as a possible agent which might defer senescence. The senescence of corn leaf discs was deferred by added calcium, and the effect was additive to the cytokinin deferral of senescence. Likewise, the senescence of Rumex leaf discs was deferred by added calcium, and the effect was additive to the gibberellin deferral of senescence. Detailed experiments with corn leaf discs established that the increase in apparent free space associated with senescence was completely prevented by calcium. An increase in hydraulic permeability during senescence was likewise demonstrated, and this increase was deferred by calcium; calcium plus benzyladenine was even more effective. Each of the measured functions of leaf senescence (chlorophyll content, protein decrease, apparent free space increase, and hydraulic permeability increase) was suppressed by calcium, and the interpretation is offered that the effects are a consequence of the calcium function in maintaining cellular membranes. PMID:16658538

Poovaiah, B. W.; Leopold, A. C.

1973-01-01

364

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

365

Red Leaf Resources and the Commercialization of Oil Shale  

E-print Network

Red Leaf Resources and the Commercialization of Oil Shale #12;About Red Leaf Resources 2006 Company commercial development field activities #12;Highlights Proven, Revolutionary Oil Shale Extraction Process Technology Significant Owned Oil Shale Resource #12;· The executive management team of Red Leaf Resources

Utah, University of

366

7 CFR 28.517 - Leaf Grade No. 7.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf Grade No. 7. 28.517 Section 28.517 Agriculture...Standards of the United States for the Leaf Grade of American Pima Cotton § 28.517 Leaf Grade No. 7. American Pima cotton which in...

2010-01-01

367

Birch Leaf Miner STAN SWIER, Extension Specialist Emeritus, Entomology  

E-print Network

days the eggs hatch (1-20 per leaf). The young larvae mine between the lower and upper surfaces 2014 UNH EXTENSION PEST FACT SHEET 13 Food & Agriculture Introduction Leaf miner larvae David Capaert. Since birch leaf miner attacks may weaken the trees good fertility and horticultural care are needed

New Hampshire, University of

368

Phenotypic selection on leaf ecophysiological traits in Helianthus  

Microsoft Academic Search

Habitats that differ in soil resource availability are expected to differ for selection on resource-related plant traits. Here, we examined spatial and temporal variation in phenotypic selection on leaf ecophysiological traits for 10 Helianthus populations, including two species of hybrid origin, Helianthus anomalus and Helianthus deserticola, and artificial hybrids of their ancestral parents. Leaf traits assessed were leaf size, succulence,

L. A. Donovan; F. Ludwig; D. R. Rosenthal; L. H. Rieseberg; S. A. Dudley

2009-01-01

369

Mandatory Leaf Node Prediction in Hierarchical Multilabel Classification  

E-print Network

Mandatory Leaf Node Prediction in Hierarchical Multilabel Classification Wei Bi James T. Kwok Department of Computer Science and Engineering Hong Kong University of Science and Technology Clear Water Bay be required to always end at leaf nodes. This is called mandatory leaf node prediction (MLNP) and is par

Kwok, James Tin-Yau

370

Turbine rotor-stator leaf seal and related method  

DOEpatents

A seal assembly for installation between rotating and stationary components of a machine includes a first plurality of leaf spring segments secured to the stationary component in a circumferential array surrounding the rotating component, the leaf spring segments each having a radial mounting portion and a substantially axial sealing portion, the plurality of leaf spring segments shingled in a circumferential direction.

Herron, William Lee (Cincinnati, OH); Butkiewicz, Jeffrey John (Simpsonville, SC)

2003-01-01

371

On the Relevance and Control of Leaf Angle  

Microsoft Academic Search

Plants can have constitutive leaf angles that are fixed and do not vary much among different growth environments. Several species, however, have the ability to actively adjust their leaf angles. Active leaf repositioning can be functional in avoiding detrimental environmental conditions, such as avoidance of heat stress and complete submergence, or can be, for example, utilized to maximize carbon gain

M. van Zanten; T. L. Pons; J. A. M. Janssen; L. A. C. J. Voesenek; A. J. M. Peeters

2010-01-01

372

Seasonal variation in Daucus carota leaf-surface and leaf-tissue chemical profiles  

Microsoft Academic Search

The purpose of this work was to document seasonal changes in leaf-surface and whole-leaf chemistry of Daucus carota cohorts that differed in life-cycle phenology (winter annual, annual, or biennial), with particular focus on compounds that serve as contact oviposition stimulants for Papilio polyxenes, the black swallowtail butterfly. Cohorts of carrot plants exhibiting different life-cycle phenologies were established, and plants from

Janie S Brooks; Paul Feeny

2004-01-01

373

An evolutionary perspective on leaf economics: phylogenetics of leaf mass per area in vascular plants  

PubMed Central

In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This “worldwide leaf economics spectrum” consists of a suite of intercorrelated leaf traits, among which leaf mass per area, LMA, is one of the most fundamental as it indicates the cost of leaf construction and light-interception borne by plants. We conducted a broad-scale analysis of the evolutionary history of LMA across a large dataset of 5401 vascular plant species. The phylogenetic signal in LMA displayed low but significant conservatism, that is, leaf economics tended to be more similar among close relatives than expected by chance alone. Models of trait evolution indicated that LMA evolved under weak stabilizing selection. Moreover, results suggest that different optimal phenotypes evolved among large clades within which extremes tended to be selected against. Conservatism in LMA was strongly related to growth form, as were selection intensity and phenotypic evolutionary rates: woody plants showed higher conservatism in relation to stronger stabilizing selection and lower evolutionary rates compared to herbaceous taxa. The evolutionary history of LMA thus paints different evolutionary trajectories of vascular plant species across clades, revealing the coordination of leaf trait evolution with growth forms in response to varying selection regimes. PMID:25165520

Flores, Olivier; Garnier, Eric; Wright, Ian J; Reich, Peter B; Pierce, Simon; Diaz, Sandra; Pakeman, Robin J; Rusch, Graciela M; Bernard-Verdier, Maud; Testi, Baptiste; Bakker, Jan P; Bekker, Renee M; Cerabolini, Bruno E L; Ceriani, Roberta M; Cornu, Guillaume; Cruz, Pablo; Delcamp, Matthieu; Dolezal, Jiri; Eriksson, Ove; Fayolle, Adeline; Freitas, Helena; Golodets, Carly; Gourlet-Fleury, Sylvie; Hodgson, John G; Brusa, Guido; Kleyer, Michael; Kunzmann, Dieter; Lavorel, Sandra; Papanastasis, Vasilios P; Perez-Harguindeguy, Natalia; Vendramini, Fernanda; Weiher, Evan

2014-01-01

374

The effect of elevated CO2 on diel leaf growth cycle, leaf carbohydrate content and canopy growth  

E-print Network

The effect of elevated CO2 on diel leaf growth cycle, leaf carbohydrate content and canopy growth%) in the growing leaf in elevated CO2, suggesting diversion of glucose to starch or other carbohydrates, making of these trees to elevated CO2 is discussed. Keywords: biomass, Biosphere 2 Laboratory, carbohydrates, elevated

Barron-Gafford, Greg

375

Living With Limited Water, Part II: Dynamics of Leaf Rolling, Leaf Water Homeostasis and Water Economy by Hybrid Rice  

Microsoft Academic Search

Change in leaf form or shape has often been enumerated as a potential means of reducing transpiration by plants experiencing water deficit. Because leaf rolling is the first and foremost visible physiological response to water deficit in rice plant, its dynamic nature and impact on leaf water homeostasis and water conservation were studied in hybrid rice (Oryza sativa L.) in

S. Singh; T. N. Singh; J. S. Chauhan

2011-01-01

376

Using Stream Leaf Packs to Explore Community Assembly  

NSDL National Science Digital Library

In this TIEE experiment, students will explore functional and taxonomic diversity in a stream ecosystem, learn about food web relationships, and learn about the ways in which abiotic and biotic factors determine what organisms are present in a community. Students will make and install artificial leaf packs in a stream, wait for the leaf packs to be colonized by stream organisms, measure abiotic variables that could influence leaf pack colonization, retrieve the leaf packs and classify the organisms they find in both taxonomic and functional ways, and participate in a class discussion of how the leaf pack community is situated within a larger ecosystem.

Hartley, Laurel

2011-08-29

377

Variations in the polarized leaf reflectance of Sorghum bicolor  

NASA Technical Reports Server (NTRS)

The polarized reflectance factor, Rq, of sorghum (Sorghum bicolor, L.) leaves from field-grown plants was measured in situ in the summers of 1983 and 1984. In 1983, three leaves of two randomly selected plants were measured at 2-week intervals. The value of Rq varied, depending on leaf and day of measurement. Measured values of Rq for the adaxial leaf surface ranged from 16 to 53; for the abaxial leaf surface the values ranged from 28 to 69. In 1984, measurements consisted of repeated observations made on the same leaf at biweekly intervals. The values of Rq from the adaxial leaf surface ranged from 26 to 38. Values of Rq from the abaxial leaf surface increased throughout the season, from 16 to 45. Differences in Rq were attributed to changes in surface details of the leaf.

Grant, Lois; Daughtry, C. S. T.; Vanderbilt, V. C.

1987-01-01

378

BOREAS TE-5 Leaf Carbon Isotope Data  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

379

Peach Leaf Senescence Delayed by Criconemella xenoplax.  

PubMed

Fall annual leaf senescence of peach was delayed in the field and in microplots in the presence of Criconemella xenoplax. Soil from the rhizosphere of orchard trees with greener leaves had ca. 2.5 x more nematodes than soil around trees in a more advanced state of fall senescence. In microplots, monoclonal antibody enzyme immunoassay (EIA) of leaf cytokinins indicated that concentration of zeatin riboside-like substances and chlorophyll content were greater in leaves of trees growing in nematode-infested soil than in trees in uninfested soil. EIA also indicated the presence of substances resembling trans-zeatin, zeatin riboside, dihydrozeatin, and dihydrozeatin riboside-like substances in whole body homogenates of C. xenoplax. Levels of zeatin-like substances were present in the nematode in greater levels than the other related substances. PMID:19290258

Nyczepir, A P; Wood, B W

1988-10-01

380

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

381

Science Nation: Leaf-cutter Ants  

NSDL National Science Digital Library

In established colonies, millions of leaf-cutter ants cut and carry sections of leaves larger than their own bodies as part of a well choreographed, highly functioning society. With support from the National Science Foundation (NSF),bacteriologist Cameron Currie and his team study ants and their complex, productive societies to help address some of human society's most pressing challenges, such as better drugs and cleaner energy.

382

Interactive electron micrograph--leaf cell  

NSDL National Science Digital Library

The following learning object is an electron micrograph of a spinach leaf cell. It is displayed through Flash and uses Zoomify to simulate a virtual microscope. Some of the organelles have been colored for identification purposes. The accompanying interactive QuickTime using a color legend to display the name of each organelle and to provide additional information, including a higher magnification of the organelle.

PhD Betty L Black (NC State University Biology)

2008-09-15

383

Downregulation of net phosphorus-uptake capacity is inversely related to leaf phosphorus-resorption proficiency in four species from a phosphorus-impoverished environment  

PubMed Central

Background and Aims Previous research has suggested a trade-off between the capacity of plants to downregulate their phosphorus (P) uptake capacity and their efficiency of P resorption from senescent leaves in species from P-impoverished environments. Methods To investigate this further, four Australian native species (Banksia attenuata, B. menziesii, Acacia truncata and A. xanthina) were grown in a greenhouse in nutrient solutions at a range of P concentrations [P]. Acacia plants received between 0 and 500 µm P; Banksia plants received between 0 and 10 µm P, to avoid major P-toxicity symptoms in these highly P-sensitive species. Key Results For both Acacia species, the net P-uptake rates measured at 10 µm P decreased steadily with increasing P supply during growth. In contrast, in B. attenuata, the net rate of P uptake from a solution with 10 µm P increased linearly with increasing P supply during growth. The P-uptake rate of B. menziesii showed no significant response to P supply in the growing medium. Leaf [P] of the four species supported this finding, with A. truncata and A. xanthina showing an increase up to a saturation value of 19 and 21 mg P g?1 leaf dry mass, respectively (at 500 µm P), whereas B. attenuata and B. menziesii both exhibited a linear increase in leaf [P], reaching 10 and 13 mg P g?1 leaf dry mass, respectively, without approaching a saturation point. The Banksia plants grown at 10 µm P showed mild symptoms of P toxicity, i.e. yellow spots on some leaves and drying and curling of the tips of the leaves. Leaf P-resorption efficiency was 69 % (B. attenuata), 73 % (B. menziesii), 34 % (A. truncata) and 36 % (A. xanthina). The P-resorption proficiency values were 0·08 mg P g?1 leaf dry mass (B. attenuata and B. menziesii), 0·32 mg P g?1 leaf dry mass (A. truncata) and 0·36 mg P g?1 leaf dry mass (A. xanthina). Combining the present results with additional information on P-remobilization efficiency and the capacity to downregulate P-uptake capacity for two other Australian woody species, we found a strong negative correlation between these traits. Conclusions It is concluded that species that are adapted to extremely P-impoverished soils, such as many south-western Australian Proteaceae species, have developed extremely high P-resorption efficiencies, but lost their capacity to downregulate their P-uptake mechanisms. The results support the hypothesis that the ability to resorb P from senescing leaves is inversely related to the capacity to downregulate net P uptake, possibly because constitutive synthesis of P transporters is a prerequisite for proficient P remobilization from senescing tissues. PMID:23293017

de Campos, Mariana C. R.; Pearse, Stuart J.; Oliveira, Rafael S.; Lambers, Hans

2013-01-01

384

Interaction between Silver Nanoparticles and Spinach Leaf  

NASA Astrophysics Data System (ADS)

Interactions of engineered nanoparticles (ENPs) with plant surfaces are critical to assessing the bioavailability of ENPs to edible plants and to further evaluating impacts of ENPs on ecological health and food safety. Silver nanoparticles (i.e., nanoAg) could enter the agroecosystems either as an active ingredient in pesticides or from other industrial and consumer applications. Thus, in the events of pesticide application, rainfall, and irrigation, vegetable leaves could become in contact and then interact with nanoAg. The present study was to assess whether the interaction of nanoAg with spinach leaves can be described by classical sorption models and to what extent it depends on and varies with dispersion methods, environmental temperature, and ion release. We investigated the stability and ion release of nanoAg dispersed by sodium dodecyl sulfate (SDS, 1%) and humic acid (HA, 10 mg C/L) solutions, as well as sorption and desorption of nanoAg on and from the fresh spinach leaf. Results showed SDS-nanoAg released about 2%-8% more Ag ion than HA-nanoAg. The sorption of Ag ion, described by the Freundlich model in the initial concentration range of 0.6-50 mg/L, was 2-4 times higher than that of nanoAg. The sorption of nanoAg on spinach leaf can be fitted by the Langmuir model, and the maximum sorption amount of HA-nanoAg and SDS-nanoAg was 0.21 and 0.41 mg/g, respectively. The higher sorption of SDS-nanoAg relative to that of HA-nanoAg could be partially resulted from the higher release of Ag ion from the former. The maximum desorption amount of HA-nanoAg and SDS-nanoAg in 1% SDS solution was 0.08 and 0.10 mg/g, respectively. NanoAg attachment on and its penetration to the spinach leaf was visualized by the Scanning Electron Microscope equipped with an Energy Dispersive Spectrometer (SEM-EDS). It is equally important that the less sorption of nanoAg under low environmental temperature could be partially due to the closure of stomata, as verified by SEM-EDS. CytoViva Hyperspectral Imaging System was also employed to map the distribution of nanoAg in the leaf profile. Significant sorption of nanoAg on spinach leaf should urge the precaution with potential widespread use of ENPs in agriculture.

Tian, Y.; Li, H.; Zhang, Y.; Riser, E.; He, S.; Zhang, W.

2013-12-01

385

Changes in clonal poplar leaf chemistry caused by stem galls alter herbivory and leaf litter decomposition.  

PubMed

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

Künkler, Nora; Brandl, Roland; Brändle, Martin

2013-01-01

386

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

Kunkler, Nora; Brandl, Roland; Brandle, Martin

2013-01-01

387

Estimation of stand-level leaf area for boreal bryophytes  

Microsoft Academic Search

Bryophytes dominate the carbon and nitrogen cycling of many poorly drained terrestrial ecosystems and are important in the\\u000a vegetation-atmosphere exchange of carbon and water, yet few studies have estimated their leaf area at the stand scale. This\\u000a study quantified the bryophyte-specific leaf area (SLA) and leaf area index (LAI) in a group of different-aged boreal forest\\u000a stands in well and

Ben Bond-Lamberty; Stith T. Gower

2007-01-01

388

Generality of leaf trait relationships: A test across six biomes  

SciTech Connect

Convergence in interspecific leaf trait relationships across diverse taxonomic groups and biomes would have important evolutionary and ecological implications. Such convergence has been hypothesized to result from trade-offs that limit the combination of plant traits for any species. Here the authors address this issue by testing for biome differences in the slope and intercept of interspecific relationships among leaf traits: longevity, net photosynthetic capacity (A{sub max}), leaf diffusive conductance (G{sub S}), specific leaf area (SLA), and nitrogen (N) status, for more than 100 species in six distinct biomes of the Americas. The six biomes were: alpine tundra-subalpine forest ecotone, cold temperate forest-prairie ecotone, montane cool temperate forest, desert shrubland, subtropical forest, and tropical rain forest. Despite large differences in climate and evolutionary history, in all biomes mass-based leaf N (N{sub mass}), SLA, G{sub S}, and A{sub max} were positively related to one another and decreased with increasing leaf life span. The relationships between pairs of leaf traits exhibited similar slopes among biomes, suggesting a predictable set of scaling relationships among key leaf morphological, chemical, and metabolic traits that are replicated globally among terrestrial ecosystems regardless of biome or vegetation type. However, the intercept (i.e., the overall elevation of regression lines) of relationships between pairs of leaf traits usually differed among biomes. With increasing aridity across sites, species had greater A{sub max} for a given level of G{sub S} and lower SLA for any given leaf life span. Using principal components analysis, most variation among species was explained by an axis related to mass-based leaf traits (A{sub max}, N, and SLA) while a second axis reflected climate, G{sub S}, and other area-based leaf traits.

Reich, P.B. [Univ. of Minnesota, Saint Paul, MN (United States). Dept. of Forest Resources; Ellsworth, D.S. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science; Walters, M.B. [Michigan State Univ., East Lansing, MI (United States). Dept. of Forestry; Vose, J.M. [Forest Service, Otto, NC (United States). Coweeta Hydrological Lab.; Gresham, C. [Clemson Univ., Georgetown, SC (United States). Baruch Forest Inst.; Volin, J.C. [Florida Atlantic Univ., Davie, FL (United States). Div. of Science; Bowman, W.D. [Inst. of Arctic and Alpine Research, Boulder, CO (United States). Mountain Research Station]|[Univ. of Colorado, Boulder, CO (United States). Dept. of Evolutionary, Population, and Organismic Biology

1999-09-01

389

Rapid biological synthesis of silver nanoparticles using plant leaf extracts  

Microsoft Academic Search

Five plant leaf extracts (Pine, Persimmon, Ginkgo, Magnolia and Platanus) were used and compared for their extracellular synthesis\\u000a of metallic silver nanoparticles. Stable silver nanoparticles were formed by treating aqueous solution of AgNO3 with the plant leaf extracts as reducing agent of Ag+ to Ag0. UV-visible spectroscopy was used to monitor the quantitative formation of silver nanoparticles. Magnolia leaf broth

Jae Yong Song; Beom Soo Kim

2009-01-01

390

Leaf life span of floating-leaved plants  

Microsoft Academic Search

Photosynthetic capacity of floating-leaved plants is relatively high comparable with terrestrial herbaceous plants, though floating-leaved plants have a much smaller biomass with a leaf area index seldom exceeding 2m2m-2. Their rather small biomass accumulation is related to higher turnover of leaf biomass or shorter leaf life span. Life span of floating leaves reported in the literature ranged mostly from 13

T. Tsuchiya

1991-01-01

391

Leaf flavonoids of Galium sect. Aparinoides (Rubiaceae)  

Microsoft Academic Search

13 taxa belonging to 4 “species groups” ofGalium L. sect.Aparinoides (Jord.)Gren. produce 15 leaf flavonoids: Apigenin-7-diglucoside, Luteolin-7-monoglucoside and 7-diglucoside, Diosmetin, Diosmetin-7-monoglucoside and 7-diglucoside; Kaempferol-3-rutinoside, Kaempferol-3,7-diglucoside, Quercetin, two Quercetin-3-monoglycosides, Rutin, Quercetin-3-rutinoside-7-glucoside, Quercetin-7-glycoside and an unidentified aglycone. TheG. trifidum, G. obtusum andG. palustre groups (with the exception of theG. tinctorium subspecies andG. elongatum) have similar flavone-flavonole patterns, while theG. antarcticum group produces

Christian Puff

1975-01-01

392

Photocontrol of Sorghum Leaf Phosphoenolpyruvate Carboxylase 1  

PubMed Central

The mechanism underlying the light effect on phosphoenolpyruvate carboxylase (PEPC) from the C4 plant sorghum (Sorghum vulgare Pers., var Tamaran) leaves was investigated. Following exposure to light a new isozyme of PEPC, specific for the green leaf and responsible for primary CO2 fixation in photosynthesis, was established. Northern blot experiments revealed the presence of PEPC mRNA showing a molecular weight of 3.4 kilobases. During the greening process, concomitant to enzyme activity, PEPC protein and PEPC messenger RNA amounts increased considerably. This photoresponse was shown to be under phytochrome control. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:16665664

Thomas, Martine; Crétin, Claude; Keryer, Eliane; Vidal, Jean; Gadal, Pierre

1987-01-01

393

Allelopathic potential of Rapanea umbellata leaf extracts.  

PubMed

The stressful conditions associated with the Brazilian savanna (Cerrado) environment were supposed to favor higher levels of allelochemicals in Rapanea umbellata from this ecosystem. The allelopathic potential of R. umbellata leaf extracts was studied using the etiolated wheat coleoptile and standard phytotoxicity bioassays. The most active extract was selected to perform a bioassay-guided isolation, which allowed identifying lutein (1) and (-)-catechin (2) as potential allelochemicals. Finally, the general bioactivity of the two compounds was studied, which indicated that the presence of 1 might be part of the defense mechanisms of this plant. PMID:23939802

Novaes, Paula; Imatomi, Maristela; Varela, Rosa M; Molinillo, José M G; Lacret, Rodney; Gualtieri, Sonia C J; Macías, Francisco A

2013-08-01

394

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

395

Antibacterial activity of various leaf extracts of Merremia emarginata  

PubMed Central

Objective To investigate the antibacterial activity and phytochemical screening of the aqueous, methanol and petroleum ether leaf extracts of Merremia emarginata (M. emarginata). Methods The antibacterial activity of leaf extracts of M. emarginata were evaluated by agar well diffusion method against four selected bacterial species. Results The presence of tannins, flavonoids, amino acids, starch, glycosides and carbohydrates in the different leaf extracts was established. The methanol extract was more effective against Bacillus cereus and Escherichia coli, whereas aqueous extract was more effective against Staphylococcus aureus and Pseudomonas aeruginosa. Conclusions : The results in the present study suggest that M. emarginata leaf can be used in treating diseases caused by the tested organisms. PMID:23569802

Elumalai, EK; Ramachandran, M; Thirumalai, T; Vinothkumar, P

2011-01-01

396

Olive leaf extract inhibits lead poisoning-induced brain injury  

PubMed Central

Olive leaves have an antioxidant capacity, and olive leaf extract can protect the blood, spleen and hippocampus in lead-poisoned mice. However, little is known about the effects of olive leaf extract on lead-induced brain injury. This study was designed to determine whether olive leaf extract can inhibit lead-induced brain injury, and whether this effect is associated with antioxidant capacity. First, we established a mouse model of lead poisoning by continuous intragastric administration of lead acetate for 30 days. Two hours after successful model establishment, lead-poisoned mice were given olive leaf extract at doses of 250, 500 or 1 000 mg/kg daily by intragastric administration for 50 days. Under the transmission electron microscope, olive leaf extract attenuated neuronal and capillary injury and reduced damage to organelles and the matrix around the capillaries in the frontal lobe of the cerebral cortex in the lead-poisoned mice. Olive leaf extract at a dose of 1 000 mg/kg had the greatest protective effect. Spectrophotometry showed that olive leaf extract significantly increased the activities of superoxide dismutase, catalase, alkaline phosphatase and acid phosphatase, while it reduced malondialdehyde content, in a dose-dependent manner. Furthermore, immunohistochemical staining revealed that olive leaf extract dose-dependently decreased Bax protein expression in the cerebral cortex of lead-poisoned mice. Our findings indicate that olive leaf extract can inhibit lead-induced brain injury by increasing antioxidant capacity and reducing apoptosis. PMID:25206510

Wang, Yu; Wang, Shengqing; Cui, Wenhui; He, Jiujun; Wang, Zhenfu; Yang, Xiaolu

2013-01-01

397

The reflection and scattering of light by a plant leaf  

NASA Astrophysics Data System (ADS)

The spectral polarization characteristics of the visible radiation reflected and scattered by a plant leaf were investigated. Measurements of the spectral brightness coefficient, the directed reflection coefficients, and the degree and azimuth of polarization of radiation reflected from a leaf were performed at different angles of incidence of radiation on the leaf and different angles of observation. More than 500 measurements were performed for 36 samples. Maple (Acer platanoides) leaves from different trees were used as objects of investigation. Peculiarities of the mechanism of formation of the flux of radiation reflected from a plant leaf have been revealed.

Atrashevskii, Yu. I.; Sikorskii, A. V.; Sikorskii, V. V.; Stel'Makh, G. F.

1999-01-01

398

Interspecfic variation in SOâ flux - leaf surface versus internal flux, and components of leaf conductance  

Microsoft Academic Search

The object of the study was to clarify the relationships among stomatal, residual, and epidermal conductances in determining the flux of SOâ air pollution to leaves. Variations in leaf SOâ and HâO vapor fluxes were determined using four plant species: Pisum sativum L. (garden pea), Lycopersicon esculentum Mill. flacca (mutant of tomato), Geranium carolinianum L. (wild geranium), and Diplacus aurantiacus

D. M. Olszyk; D. T. Tingey

1985-01-01

399

Stomatal Closure during Leaf Dehydration, Correlation with Other Leaf Physiological Traits1  

E-print Network

) at ap- proximately the same time as the evolution of an internal water conducting system in plants desiccation remains controversial. This paper examines characteristics of the vascular and photosynthetic hydraulic conductance (Kleaf) was measured from the relaxation kinetics of leaf water potential ( l

Holbrook, N. Michele

400

INTERSPECFIC VARIATION IN SO2 FLUX - LEAF SURFACE 'VERSUS' INTERNAL FLUX, AND COMPONENTS OF LEAF CONDUCTANCE  

EPA Science Inventory

The object of the study was to clarify the relationships among stomatal, residual, and epidermal conductances in determining the flux of SO2 air pollution to leaves. Variations in leaf SO2 and H2O vapor fluxes were determined using four plant species: Pisum sativum L. (garden pea...

401

The Okra Leaf Shape Mutation in Cotton is Active in all Cell Layers of the Leaf  

Microsoft Academic Search

in the middle mesophyll of the lamina and the vasculature of major lateral veins (L3 derivatives) had no local effect on the expansion of the lamina, but significantly increased lobe length. These results demonstrate that L2 O is active in every tissue layer of the leaf.

Liam Dolan; R. Scott Poethig

1998-01-01

402

Digital measurement of heliotropic leaf response in soybean cultivars and leaf exposure to solar UVB radiation  

Microsoft Academic Search

Inconsistencies in reported sensitivities of soybean cultivars [Glycine max (L.) Merr.] to enhanced ultraviolet-B (UVB) irradiance may in part be due to differences in the radiative environment of the experimental conditions or differences in exposure due to heliotropic response. In order to examine the impact of heliotropic movement on UVB exposure of the soybean upper trifoliate, leaf position was electronically

Cheryl I Bawhey; Richard H Grant; Wei Gao

2003-01-01

403

Food selection by the South Indian leaf-monkey, Presbytis johnii , in relation to leaf chemistry  

Microsoft Academic Search

The leaf-monkey Presbytis johnii has been found to exhibit considerable selectivity in its dietary utilization of mature foliage in a rain-forest habitat. To investigate the basis of this selectivity and to examine the hypothesis that the observed selection is related to the digestibility and toxicity of the available foliage, chemical analyses have been made on 16 of the most important

John F. Oates; Peter G. Waterman; Gillian M. Choo

1980-01-01

404

Estimating leaf photosynthetic pigments information by stepwise multiple linear regression analysis and a leaf optical model  

NASA Astrophysics Data System (ADS)

Leaf pigments are key elements for plant photosynthesis and growth. Traditional manual sampling of these pigments is labor-intensive and costly, which also has the difficulty in capturing their temporal and spatial characteristics. The aim of this work is to estimate photosynthetic pigments at large scale by remote sensing. For this purpose, inverse model were proposed with the aid of stepwise multiple linear regression (SMLR) analysis. Furthermore, a leaf radiative transfer model (i.e. PROSPECT model) was employed to simulate the leaf reflectance where wavelength varies from 400 to 780 nm at 1 nm interval, and then these values were treated as the data from remote sensing observations. Meanwhile, simulated chlorophyll concentration (Cab), carotenoid concentration (Car) and their ratio (Cab/Car) were taken as target to build the regression model respectively. In this study, a total of 4000 samples were simulated via PROSPECT with different Cab, Car and leaf mesophyll structures as 70% of these samples were applied for training while the last 30% for model validation. Reflectance (r) and its mathematic transformations (1/r and log (1/r)) were all employed to build regression model respectively. Results showed fair agreements between pigments and simulated reflectance with all adjusted coefficients of determination (R2) larger than 0.8 as 6 wavebands were selected to build the SMLR model. The largest value of R2 for Cab, Car and Cab/Car are 0.8845, 0.876 and 0.8765, respectively. Meanwhile, mathematic transformations of reflectance showed little influence on regression accuracy. We concluded that it was feasible to estimate the chlorophyll and carotenoids and their ratio based on statistical model with leaf reflectance data.

Liu, Pudong; Shi, Runhe; Wang, Hong; Bai, Kaixu; Gao, Wei

2014-10-01

405

On the temporal variation of leaf magnetic parameters: seasonal accumulation of leaf-deposited and leaf-encapsulated particles of a roadside tree crown.  

PubMed

Understanding the accumulation behaviour of atmospheric particles inside tree leaves is of great importance for the interpretation of biomagnetic monitoring results. In this study, we evaluated the temporal variation of the saturation isothermal remanent magnetisation (SIRM) of leaves of a roadside urban Platanus × acerifolia Willd. tree in Antwerp, Belgium. We hereby examined the seasonal development of the total leaf SIRM signal as well as the leaf-encapsulated fraction of the deposited dust, by washing the leaves before biomagnetic analysis. On average 38% of the leaf SIRM signal was exhibited by the leaf-encapsulated particles. Significant correlations were found between the SIRM and the cumulative daily average atmospheric PM10 and PM2.5 measurements. Moreover, a steady increase of the SIRM throughout the in-leaf season was observed endorsing the applicability of biomagnetic monitoring as a proxy for the time-integrated PM exposure of urban tree leaves. Strongest correlations were obtained for the SIRM of the leaf-encapsulated particles which confirms the dynamic nature of the leaf surface-accumulated particles. PMID:25000572

Hofman, Jelle; Wuyts, Karen; Van Wittenberghe, Shari; Samson, Roeland

2014-09-15

406

Pharmacognostical evaluation of Barringtonia acutangula leaf  

PubMed Central

Barringtonia acutangula (L.) Gaertn. (Family: Lecythidaceae) is an evergreen tree with simple, alternate leaves, long pendulous racemes, dark scarlet flowers, and ellipsoid to ovoid berries containing one ovoid black seed. The present study deals with a detailed pharmacognostical study on the leaf of the crude drug, B. acutangula. Morphoanatomy of the leaf was studied using light and confocal microscopy and World Health Organization (WHO) guidelines on quality control methods for medicinal plant materials. Literature reveals that the phytoconstituents like tanginol, barrinic acid, and barringenic acid are present in the wood and fruits of this plant. Our preliminary phytochemical studies of the powdered leaves revealed the presence of terpenes, flavanoids, carbohydrates, tannins, steroids, and glycosides. The physico-chemical, morphological, histological parameters, and High Performance-Thin Layer Chromatographic (HPTLC) profile presented in this paper may be proposed as parameters to establish the authenticity of B. acutangula and can possibly help to differentiate the drug from its other species and the pharmacognostic profile of the leaves presented here will assist in standardization viz., quality, purity, and sample identification. PMID:21897641

Padmavathi, Dharamaraj; Susheela, Lakshmi; Bharathi, Rajkishore Vijaya

2011-01-01

407

Leaf metallome preserved over 50 million years.  

PubMed

Large-scale Synchrotron Rapid Scanning X-ray Fluorescence (SRS-XRF) elemental mapping and X-ray absorption spectroscopy are applied here to fossil leaf material from the 50 Mya Green River Formation (USA) in order to improve our understanding of the chemistry of fossilized plant remains. SRS-XRF of fossilized animals has previously shown that bioaccumulated trace metals and sulfur compounds may be preserved in their original distributions and these elements can also act as biomarkers for specific biosynthetic pathways. Similar spatially resolved chemical data for fossilized plants is sparsely represented in the literature despite the multitude of other chemical studies performed. Here, synchrotron data from multiple specimens consistently show that fossil leaves possess chemical inventories consisting of organometallic and organosulfur compounds that: (1) map discretely within the fossils, (2) resolve fine scale biological structures, and (3) are distinct from embedding sedimentary matrices. Additionally, the chemical distributions in fossil leaves are directly comparable to those of extant leaves. This evidence strongly suggests that a significant fraction of the chemical inventory of the examined fossil leaf material is derived from the living organisms and that original bioaccumulated elements have been preserved in situ for 50 million years. Chemical information of this kind has so far been unknown for fossilized plants and could for the first time allow the metallome of extinct flora to be studied. PMID:24804302

Edwards, N P; Manning, P L; Bergmann, U; Larson, P L; van Dongen, B E; Sellers, W I; Webb, S M; Sokaras, D; Alonso-Mori, R; Ignatyev, K; Barden, H E; van Veelen, A; Anné, J; Egerton, V M; Wogelius, R A

2014-04-01

408

Protein changes during oat leaf senescence  

SciTech Connect

Protein changes during in situ and in vitro senescence of the first leaf of 8-day old seedlings of Avena sativa cv. Victory have been examined. Senescence was induced by placing either intact seedlings or by floating the apical 3 cm-long leaf segments on water, in dark at 27 C for 0 to 4 days. Total protein content and chlorophyll content declined steadily during senescence. Rate of amino acid uptake, studied with /sup 14/C-B-alanine, declined sharply. Rate of protein synthesis decreased during the first 24 h during in vitro, and 48 h during in situ senescence. Thereafter, the rate increased sharply. At the end of 4 days the rate of protein synthesis had again declined in case of in vitro senescence but remained high in case of in situ senescence. Large changes in protein patterns, as shown by 1-D and 2-D PAGE, also occurred during senescence. Major changes in the population of translatable mRNAs that occur during in situ and in vitro senescence will be compared and discussed.

Dhindsa, R.S.; Tsai, C.D.; Lalonde, L.

1986-04-01

409

Spectroscopic determination of leaf nutritional, morpholgical, and metabolic traits  

NASA Astrophysics Data System (ADS)

Terrestrial ecosystems, particularly forests, play an important role in the global carbon and water cycles. Remote sensing observations are invaluable to the study of vegetation patterning, ecosystem functioning, and dynamics. This research examined the relationships between leaf optical properties and important leaf structural, biochemical, and metabolic traits that describe the photosynthetic capacity, recalcitrance, and nutrient dynamics of plant canopies. This was done utilizing leaf-level reflectance spectroscopy in conjunction with traditional chemometric statistical techniques designed to handle high-dimensionality data, specifically partial least-squares regression (PLSR). A suite of leaf biochemical and morphological traits were estimated with high accuracy and precision using measurements of dried and ground leaf material with a portable spectroradiometer in conjunction with PLSR modeling. An important result from this study was that a single model could be developed to accurately estimate the variation in leaf traits, including nitrogen and carbon content, lignin, fiber and cellulose, isotopic nitrogen-15, and leaf mass per area, across species, growth environments, throughout the vertical profile of a canopy, and with leaf lifespan. A residual analysis of the model prediction errors showed no significant biases observed by tree species, canopy position, or leaf age. Fresh-leaf reflectance spectroscopy was used to identify the linkages between leaf photosynthetic metabolism and leaf optical properties within controlled and natural environments, and across diverse plant species. Two key parameters controlling photosynthetic rates - the maximum rates of RuBisCO carboxylation (Vcmax) and RuBP regeneration ( Jmax) --- were directly estimated using leaf spectra and concurrent gas-exchange measurements. The models for each variable captured the pronounced temperature sensitivity of plants, and integrated the significant variability in metabolism across species that is related to differences in leaf structure and biochemistry. The PLSR models displayed high accuracy in predictions using independent validation data. Models identified key spectral regions related to leaf biochemistry, including foliar nitrogen and pigments, as well as wavelengths related to the regulation of photosynthesis, dissipation of excess energy and chlorophyll fluorescence. In sum, this research provides a novel empirical basis for estimating parameters critical to the measurement of photosynthetic activity in plants.

Serbin, Shawn P.

410

Temperature response of whole-plant CO2 exchange rates of four upland cotton cultivars differing in leaf shape and leaf pubescence  

Microsoft Academic Search

It seems likely that CO2 exchange rates of cotton (Gossypium hirsutum L.) cultivars differing in leaf shape and leaf pubescence would respond differently to heat stress due to differences in boundary layer thickness. The objective of this study was to determine if CO2 exchange rates in commercially available cotton cultivars differing in leaf shape and leaf pubescence respond differently to

Craig W. Bednarz; Marc W. van Iersel

2001-01-01

411

Survey on Modeling and Visualization of Plant Leaf Color  

Microsoft Academic Search

Much work has been done on the morphologic modeling and visualization of leaves. Leaf is one of the most important organs of a plant, and so leaf color and texture are not only important external characteristics, but also expressions of the plant's intrinsic physiology and the growth state, since they have a close relationship with the physiological status. Growth, age,

Xiaomin Wang; Chunjiang Zhao; Shenglian Lu; Xinyu Guo

2009-01-01

412

Tamarindus indica L. leaf is a source of allelopathic substance  

Microsoft Academic Search

The allelopathic potential of the Tamarindus indica L. leaf was investigated through bioassay guided studies using several weed and edible crop species. Both radicle and hypocotyl growth of all the plant species tested was strongly inhibited by the tamarind leaf using a sandwich method. The growth of weed species was reduced more than that of edible crop species. Among the

Syeda Shahnaz Parvez; Mohammad Masud Parvez; Eiji Nishihara; Hiroshi Gemma; Yoshiharu Fujii

2003-01-01

413

The biochemical control of leaf expansion during drought  

Microsoft Academic Search

Over the past decade it has become clear that we cannot always explain the observed reduction in leaf expansion rates during drought by measuring the plant's water relations. This has led us to question the possibility of a role for the cell wall and its biochemical machinery in controlling the rate of leaf expansion during drought. However, if we are

Mark A. Bacon

1999-01-01

414

RESEARCH PAPER The dependence of leaf hydraulic conductance on  

E-print Network

of the leaf vascular system, extravascular tissues and stomates in an approxi- mately serial pathway. Leaf hydraulic conductance to liquid water (KL) on irradiance when measured with a high pressure flowmeter (HPFM). During HPFM measurements, water is perfused into leaves faster than it evaporates hence water infiltrates

Sack, Lawren

415

Rounded end multi-leaf penumbral measurements with radiochromic film.  

PubMed

Multi-leaf penumbral doses have been investigated for 6 MV x-rays and a Varian millennium multi-leaf collimator (MLC) using Gafchromic MD-55-2, radiochromic film and X-omat V radiographic film. An advantage of Gafchromic film for multi-leaf penumbral dose measurement is the relatively low energy dependence of the film. A comparison of penumbral dose measurements has also ascertained the effects of energy response on radiographic film in this region. Similar 80%/20% penumbral doses have been measured with both types of films. Thus there is a relatively low energy effect on penumbral dose measurements in film dosimetry. The 80%/20% dose penumbral distances for rounded leaf end multi-leafs for a 10 cm x 10 cm field at Dmax were found to be 4.6 mm and 4.3 mm for radiochromic and radiographic film respectively. This is compared to 2.6 mm and 2.6 mm for the leaf edge penumbra. Radiochromic film also measured leaf end/interleaf leakage doses in the penumbral region, which was shown to produce approximately 4% of maximum dose wave across the penumbral region with maximum doses delivered at the MLC leaf interfaces. PMID:14516111

Butson, Martin J; Yu, Peter K N; Cheung, Tsang

2003-09-01

416

Hands-On Whole Science: A Leaf Sampler.  

ERIC Educational Resources Information Center

Presents two elementary school activities to help students learn about autumn. The activities use autumn leaves to teach that each type of tree has its own distinctive type of leaf. One activity involves tracing, drawing, and writing about leaves; the other involves making a quilt using leaf designs. (SM)

Kepler, Lynne

1991-01-01

417

Leaf-cutting ants revisited: Towards rational management and control  

Microsoft Academic Search

Leaf-cutting ants, being the principal herbivores and ecosystem engineers in the Neotropics, have been considered to be a keystone species in natural ecosystems and agroecosystems, due to the direct and indirect effects of their plant defoliation activities. This review summarizes current concepts of the biological and ecological importance of leaf-cutting ants. The ants' pest status is briefly assessed from both

James Montoya-Lerma; Carolina Giraldo-Echeverri; Inge Armbrecht; Alejandro Farji-Brener; Zoraida Calle

2012-01-01

418

Leaf Trichome Formation and Plant Resistance to Herbivory  

Microsoft Academic Search

arkk¨ ainen Leaf trichomes contribute to plant resistance against herbivory. In several plant species, the trichome density of new leaves increases after herbivore damage. Here we review the genetic basis of trichome production and the functional and adap- tive significance of constitutive and induced trichome formation. We focus on leaf trichomes and their production in response to damage caused by

Peter Dalin; Jon Ågren; Christer Björkman; Piritta Huttunen; Katri Kärkkäinen

419

Generality of Leaf Trait Relationships: A Test across Six Biomes  

Microsoft Academic Search

Convergence in interspecific leaf trait relationships across diverse taxonomic groups and biomes would have important evolutionary and ecological implications. Such convergence has been hypothesized to result from trade-offs that limit the combination of plant traits for any species. Here we address this issue by testing for biome differences in the slope and intercept of interspecific relationships among leaf traits: longevity,

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

1999-01-01

420

Characterizing natural cellulose fibers from velvet leaf ( Abutilon theophrasti) stems  

Microsoft Academic Search

Velvet leaf (Abutilon theophrasti) that is currently considered a weed and an agricultural problem could be used as a source for high quality natural cellulose fibers. The fibers obtained from the velvet leaf stems are mainly composed of approximately 69% cellulose and 17% lignin. The single cells in the fiber have lengths of approximately 0.9mm, shorter than those in common

Narendra Reddy; Yiqi Yang

2008-01-01

421

Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought  

E-print Network

Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought Tolerance1[C shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell

Sack, Lawren

422

Elucidating the role of transport processes in leaf glucosinolate distribution.  

PubMed

In Arabidopsis (Arabidopsis thaliana), a strategy to defend its leaves against herbivores is to accumulate glucosinolates along the midrib and at the margin. Although it is generally assumed that glucosinolates are synthesized along the vasculature in an Arabidopsis leaf, thereby suggesting that the margin accumulation is established through transport, little is known about these transport processes. Here, we show through leaf apoplastic fluid analysis and glucosinolate feeding experiments that two glucosinolate transporters, GTR1 and GTR2, essential for long-distance transport of glucosinolates in Arabidopsis, also play key roles in glucosinolate allocation within a mature leaf by effectively importing apoplastically localized glucosinolates into appropriate cells. Detection of glucosinolates in root xylem sap unambiguously shows that this transport route is involved in root-to-shoot glucosinolate allocation. Detailed leaf dissections show that in the absence of GTR1 and GTR2 transport activity, glucosinolates accumulate predominantly in leaf margins and leaf tips. Furthermore, we show that glucosinolates accumulate in the leaf abaxial epidermis in a GTR-independent manner. Based on our results, we propose a model for how glucosinolates accumulate in the leaf margin and epidermis, which includes symplasmic movement through plasmodesmata, coupled with the activity of putative vacuolar glucosinolate importers in these peripheral cell layers. PMID:25209984

Madsen, Svend Roesen; Olsen, Carl Erik; Nour-Eldin, Hussam Hassan; Halkier, Barbara Ann

2014-11-01

423

Leaf choice by crustaceans in a mangrove forest in Queensland  

Microsoft Academic Search

The feeding behaviour of leaf eating crustaceans feeding on leaves shed by Avicennia marina, Bruguiera gymnorhiza and Rhizophora stylosa in the mangrove forest at Myora Springs, Queensland, Australia was studied between 1980 and 1984. Individual Sesarma erythrodactyla (carapace >9 mm long), one of the most abundant species of crabs in the forest, processed approximately half a leaf from any of

J. Camilleri

1989-01-01

424

Large seasonal swings in leaf area of Amazon rainforests  

E-print Network

Large seasonal swings in leaf area of Amazon rainforests Ranga B. Mynenia , Wenze Yanga Drive, Pasadena, CA 91109; hCalifornia State University at Monterey Bay and Ecosystem Science but not on the accompanying changes in leaf area that regulate vegetation­atmosphere ex- changes of energy, momentum, and mass

Myneni, Ranga B.

425

A photothermal model of leaf area index for greenhouse crops  

Microsoft Academic Search

Leaf area index (LAI) is an important variable for modelling canopy photosynthesis and crop water use. In many crop simulation models, prediction of LAI is very sensitive to errors in the value of parameter “specific leaf area” (SLA), which often relies on destructive measurements to determine. In this study, we present a model for predicting LAI of greenhouse crops based

R. Xu; J. Dai; W. Luo; X. Yin; Y. Li; X. Tai; L. Han; Y. Chen; L. Lin; G. Li; C. Zou; W. Du; M. Diao

2010-01-01

426

Plant Leaf Residue Decomposition, Nutrient Release and Soil Enzyme Activity  

Microsoft Academic Search

We studied the impact of plant leaf residue decompo sition and nutrient release of nitrogen and phosphorus of two weed species - Imperata cylindrica and Chromolaena odorata - and one native forest species - Phyllanthus discoideus - on soil enzyme activities in a pot experiment in the humid tropics of central Cameroon. We tested th e impact of plant leaf

Julia Dux; Lindsey Norgrove; Stefan Hauser; Barbara Wick; Ronald Kühne

427

arXiv:condmat/0208232 The Shape of the Edge of a Leaf  

E-print Network

biologists is that the curling shapes of plants are produced by detailed genetic instructions telling various separated by (dx;dy) are given by dr 2 = g xx dx 2 +2g xy dxdy+g yy dy 2 : (1) Embed the sheet in three

Texas at Austin. University of

428

Microscopic evaluation and physiochemical analysis of Dillenia indica leaf  

PubMed Central

Objective To study detail microscopic evaluation and physiochemical analysis of Dillenia indica (D. indica) leaf. Methods Fresh leaf sample and dried power of the leaf were studied macroscopically and microscopically. Preliminary phytochemical investigation of plant material was done. Other WHO recommended parameters for standardizations were also performed. Results The detail microscopy revealed the presence of anomocytic stomata, unicellular trichome, xylem fibres, calcium oxalate crystals, vascular bundles, etc. Leaf constants such as stomatal number, stomatal index, vein-islet number and veinlet termination numbers were also measured. Physiochemical parameters such as ash values, loss on drying, extractive values, percentage of foreign matters, swelling index, etc. were also determined. Preliminary phytochemical screening showed the presence of steroids, terpenoids, glycosides, fatty acids, flavonoids, phenolic compounds and carbohydrates. Conclusions The microscopic and physiochemical analysis of the D. indica leaf is useful in standardization for quality, purity and sample identification. PMID:23569789

Kumar, S; Kumar, V; Prakash, Om

2011-01-01

429

Temperature effect on leaf water deuterium enrichment and isotopic fractionation during leaf lipid biosynthesis: Results from controlled growth of C 3 and C 4 land plants  

Microsoft Academic Search

The hydrogen isotopic ratios (2H\\/1H) of land plant leaf water and the carbon-bound hydrogen of leaf wax lipids are valuable indicators for climatic, physiological, metabolic and geochemical studies. Temperature will exert a profound effect on the stable isotopic composition of leaf water and leaf lipids as it directly influences the isotopic equilibrium (IE) during leaf water evaporation and cellular water

Youping Zhou; Kliti Grice; Yoshito Chikaraishi; Hilary Stuart-Williams; Graham D. Farquhar; Naohiko Ohkouchi

2011-01-01

430

Systematics of smooth leaf margin Juniperus of the western hemisphere based on leaf essential oils and RAPD DNA fingerprinting  

Microsoft Academic Search

The composition of the leaf essential oils of 13 taxa of the smooth leaf margin Juniperus in sect. Sabina from the western hemisphere are reported and compared. In addition, DNA fingerprinting revealed similar patterns among these species. Based on these data, a new species, very similar to J. blancoi and J. scopulorum, is recognized from northern Mexico: Juniperus mucronata sp.

Robert P. Adams

2000-01-01

431

Leaf light reflectance, transmittance, absorptance, and optical and geometrical parameters for eleven plant genera with different leaf mesophyll arrangements.  

NASA Technical Reports Server (NTRS)

Review of research on radiation interactions within plant canopies and communities and interactions of various leaf structures (mesophyll arrangements) with electromagnetic radiation involved in the interpretation of data sensed from air or spacecraft. The hypothesis underlying the research reported is that leaf mesophyll arrangements influence spectral energy measurements of leaves.

Gausman, H. W.; Allen, W. A.; Wiegand, C. L.; Escobar, D. E.; Rodriguez, R. R.

1971-01-01

432

Leaf demography and growth responses to altered resource availability in woody plants of contrasting leaf habit in a subtropical savanna  

Microsoft Academic Search

Leaf demography and growth of six common, co-occurring woody plant species that varied in stature (tree vs. shrub) and leaf texture (sclerophyllous, coriaceous, malacophyllous) were examined in a subtropical savanna parkland in southern Texas, USA. We tested the hypotheses that, (a) leaves of plants with evergreen canopies would have longer life spans than those of deciduous species; (b) supplementation of

Jim A. Nelson; Paul W. Barnes; Steve Archer

2002-01-01

433

Allocating leaf nitrogen for the maximization of carbon gain: Leaf age as a control on the allocation program  

Microsoft Academic Search

Simulations using a biochemically-based model of leaf photosynthesis make it possible to predict the distribution of leaf nitrogen contents that maximizes photosynthetic carbon gain over the canopy of an entire plant. In general, the optimal nitrogen content increased with increasing daily photosynthetically active photon irradiance.

C. Field

1983-01-01

434

Spectral radiance estimates of leaf area and leaf phytomass of small grains and native vegetation  

NASA Technical Reports Server (NTRS)

Similarities and/or dissimilarities in radiance characteristics were studied among barley (Hordeum vulgare L.), oats (Avena fatua L.), spring and winter wheat (Triticum aestivum L.), and short-grass prairie vegetation. The site was a Williams loam soil (fine-loamy mixed, Typic Argiborolls) near Sidney, Montana. Radiances were measured with a truck-mounted radiometer. The radiometer was equipped with four wavelength bands: 0.45 to 0.52, 0.52 to 0.60, 0.63 to 0.69, and 0.76 to 0.90 micron. Airborne scanner measurements were made at an altitude of 600 m four times during the season under clear sky conditions. The airborne scanner was equipped with the same four bands as the truck-mounted radiometer plus the following: 1.00 to 1.30, 1.55 to 1.75, 2.08 to 2.35, and 10.4 to 12.5 microns. Comparisons using individual wave bands, the near IR/red, (0.76 to 0.90 micron)/(0.63 to 0.69 micron) ratio and the normalized difference vegetation index, ND = (IR - red)/(IR + red), showed that only during limited times during the growing season were some of the small grains distinguishable from one another and from native rangeland vegetation. There was a common relation for all small grains between leaf area index and green leaf phytomass and between leaf area index or green leaf phytomass and the IR/red ratio.

Aase, J. K.; Brown, B. S.; Millard, J. P.

1986-01-01

435

Predicting leaf traits of herbaceous species from their spectral characteristics  

PubMed Central

Trait predictions from leaf spectral properties are mainly applied to tree species, while herbaceous systems received little attention in this topic. Whether similar trait–spectrum relations can be derived for herbaceous plants that differ strongly in growing strategy and environmental constraints is therefore unknown. We used partial least squares regression to relate key traits to leaf spectra (reflectance, transmittance, and absorbance) for 35 herbaceous species, sampled from a wide range of environmental conditions. Specific Leaf Area and nutrient-related traits (N and P content) were poorly predicted from any spectrum, although N prediction improved when expressed on a per area basis (mg/m2 leaf surface) instead of mass basis (mg/g dry matter). Leaf dry matter content was moderately to good correlated with spectra. We explain our results by the range of environmental constraints encountered by herbaceous species; both N and P limitations as well as a range of light and water availabilities occurred. This weakened the relation between the measured response traits and the leaf constituents that are truly responsible for leaf spectral behavior. Indeed, N predictions improve considering solely upper or under canopy species. Therefore, trait predictions in herbaceous systems should focus on traits relating to dry matter content and the true, underlying drivers of spectral properties. PMID:24683454

Roelofsen, Hans D; van Bodegom, Peter M; Kooistra, Lammert; Witte, Jan-Philip M

2014-01-01

436

Spring Wheat Leaf Appearance and Temperature: Extending the Paradigm?  

PubMed Central

Extensive research shows temperature to be the primary environmental factor controlling the phyllochron, or rate of leaf appearance, of wheat (Triticum aestivum L.). Experimental results suggest that soil temperature at crown depth, rather than air temperature above the canopy, would better predict wheat leaf appearance rates. To test this hypothesis, leaf appearance in spring wheat (‘Nordic’) was measured in a 2?year field experiment (Nunn clay loam soil; fine, smectitic, mesic Aridic, Argiustoll) with three planting dates and two soil temperature treatments. One temperature treatment (denoted +3C) consisted of heating the soil at crown depth to 3 °C above the ambient soil temperature (denoted +0C). Main stem cumulative leaf number was measured at least weekly until flag leaf emergence. Leaf appearance was essentially linear with both air and soil growing degree?days (GDD), although there was a stronger linear relationship with soil GDD in the +0C plants than in +3C plants. A weak positive relationship between planting date and the phyllochron was observed. Unexpectedly, we found that heating the soil did not increase the rate of leaf appearance, as the paradigm would predict. To explain these results, we propose extending the paradigm in two ways. First, three processes are involved in leaf appearance: (1) cell division at the shoot apex forms the primordium; (2) cell division in the intercalary meristem forms the cells that then (3) expand to produce the leaf. Cell division is predominately controlled by temperature, but cell expansion is considerably more affected by factors other than temperature, explaining the influence of other factors on the phyllochron. Secondly, the vertical distribution of the two meristems and region of cell expansion occur over a significant distance, where temperature varies considerably, and temperature at a specific point (e.g. crown depth) does not account for the entire temperature regime under which leaves are developing. PMID:12714367

MCMASTER, GREGORY S.; WILHELM, W. W.; PALIC, D. B.; PORTER, JOHN R.; JAMIESON, P. D.

2003-01-01

437

Light ray tracing through a leaf cross section  

NASA Technical Reports Server (NTRS)

A light ray, incident at about 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's equations and Snell's law. The optical mediums of the leaf considered for ray tracing are air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A spectroreflectometer.

Kumar, R.; Silva, L.

1973-01-01

438

Light ray tracing through a leaf cross section  

NASA Technical Reports Server (NTRS)

A light ray, incident at about 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's equations and Snell's law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The ray is also drawn through the same leaf cross section with cell wall and air as the only optical mediums. The values of the reflection and transmission found from the ray tracing tests agree closely with the experimental results obtained using a Beckman Dk-2A Spectroreflector.

Kumar, R.; Silva, L. F.

1973-01-01

439

Leaf hydraulic conductance declines in coordination with photosynthesis, transpiration and leaf water status as soybean leaves age regardless of soil moisture.  

PubMed

Photosynthesis requires sufficient water transport through leaves for stomata to remain open as water transpires from the leaf, allowing CO2 to diffuse into the leaf. The leaf water needs of soybean change over time because of large microenvironment changes over their lifespan, as leaves mature in full sun at the top of the canopy and then become progressively shaded by younger leaves developing above. Leaf hydraulic conductance (K leaf), a measure of the leaf's water transport capacity, can often be linked to changes in microenvironment and transpiration demand. In this study, we tested the hypothesis that K leaf would decline in coordination with transpiration demand as soybean leaves matured and aged. Photosynthesis (A), stomatal conductance (g s) and leaf water potential (?leaf) were also measured at various leaf ages with both field- and chamber-grown soybeans to assess transpiration demand. K leaf was found to decrease as soybean leaves aged from maturity to shading to senescence, and this decrease was strongly correlated with midday A. Decreases in K leaf were further correlated with decreases in g s, although the relationship was not as strong as that with A. Separate experiments investigating the response of K leaf to drought demonstrated no acclimation of K leaf to drought conditions to protect against cavitation or loss of g s during drought and confirmed the effect of leaf age in K leaf observed in the field. These results suggest that the decline of leaf hydraulic conductance as leaves age keeps hydraulic supply in balance with demand without K leaf becoming limiting to transpiration water flux. PMID:25281701

Locke, Anna M; Ort, Donald R

2014-12-01

440

The oxygen isotope enrichment of leaf-exported assimilates--does it always reflect lamina leaf water enrichment?  

PubMed

The oxygen stable isotope composition of plant organic matter (OM) (particularly of wood and cellulose in the tree ring archive) is valuable in studies of plant-climate interaction, but there is a lack of information on the transfer of the isotope signal from the leaf to heterotrophic tissues. We studied the oxygen isotopic composition and its enrichment above source water of leaf water over diel courses in five tree species covering a broad range of life forms. We tracked the transfer of the isotopic signal to leaf water-soluble OM and further to phloem-transported OM. Observed leaf water evaporative enrichment was consistent with values predicted from mechanistic models taking into account nonsteady-state conditions. While leaf water-soluble OM showed the expected (18)O enrichment in all species, phloem sugars were less enriched than expected from leaf water enrichment in Scots pine (Pinus sylvestris), European larch (Larix decidua) and Alpine ash (Eucalyptus delegatensis). Oxygen atom exchange with nonenriched water during phloem loading and transport, as well as a significant contribution of assimilates from bark photosynthesis, can explain these phloem (18)O enrichment patterns. Our results indicate species-specific uncoupling between the leaf water and the OM oxygen isotope signal, which is important for the interpretation of tree ring data. PMID:23763637

Gessler, Arthur; Brandes, Elke; Keitel, Claudia; Boda, Sonja; Kayler, Zachary E; Granier, André; Barbour, Margaret; Farquhar, Graham D; Treydte, Kerstin

2013-10-01

441

The maize macrohairless1 locus specifically promotes leaf blade macrohair initiation and responds to factors regulating leaf identity.  

PubMed Central

The leaf surfaces of almost all plant species possess specialized epidermal cell types that form hairs or trichomes. Maize leaves produce three distinct types of hairs, the most prominent being the macrohairs that serve as a marker for adult leaf identity and may contribute to insect resistance. This report describes the maize macrohairless1 (mhl1) locus, which promotes macrohair initiation specifically in the leaf blade. Each of seven recessive mhl1 mutant alleles significantly reduces or eliminates macrohairs in the leaf blade. The mhl1 mutations block macrohair initiation rather than interfering with macrohair morphogenesis. Genetic mapping placed mhl1 within bin 4 on chromosome 9. A second independently segregating locus was found to partially suppress the mhl1 mutant phenotype in certain genetic backgrounds. Macrohair density was observed to increase during early adult vegetative development and then progressively decline, suggesting macrohair initiation frequency is affected by factors that act throughout shoot development. Genetic analyses demonstrated that mhl1 acts in the same pathway but downstream of factors that either promote or repress adult leaf identity. Thus, mhl1 plays a key role in integrating developmental programs that regulate leaf identity during shoot development with those that specify macrohair initiation within the leaf blade. PMID:15082562

Moose, Stephen P; Lauter, Nick; Carlson, Shawn R

2004-01-01

442

An outbreak of foxglove leaf poisoning.  

PubMed

Comfrey (Symphytum officinale) leaves resemble those of foxglove (Digitalis purpurea) when the plant is not in bloom and, therefore, cardiac glycoside poisoning may occur when people confuse foxglove with comfrey. We report an outbreak of foxglove leaf poisoning following the use of alleged "comfrey" herbal tea. Nine patients were involved and initially presented with nausea, vomiting, diarrhea and dizziness. Significant cardiotoxicity developed later among the 3 patients who also had mild hyperkalemia. Peak serum digoxin concentration measured by immunoassay was elevated in all patients and ranged from 4.4 ng/mL to 139.5 ng/mL. Patients with severe cardiotoxicity were treated with temporary cardiac pacing. Moreover, 40-80 mg of digoxin-specific antibody therapy was given without any effect. All patients recovered uneventfully. Our report highlights the potential risk of misidentification of herbs; in this case, D. purpurea was mistaken for S. officinale. Physicians should be aware that cardiac glycoside poisoning could arise from such misidentification. Public education about the toxicity of D. purpurea poisoning may reduce the risk of misidentification and subsequent poisoning. PMID:20171590

Lin, Chun-Chi; Yang, Chen-Chang; Phua, Dong-Haur; Deng, Jou-Fang; Lu, Li-Hua

2010-02-01

443

[Chemical constituents of leaf of Eucommia ulmoides].  

PubMed

Ten compounds were isolated from the leaf of Eucommia ulmoides by means of recrystallization and chromatographic techniques such as D-101 macroporous resin, MCI resin, ODS gel, Sephadex LH-20 and Rp-HPLC. Their structures were identified by NMR spectral analyses as kaempferide 3-O-beta-D-glucoside (1), quercetin-3-O-beta-D-glucoside (2), quercetin (3), quercetin-3-O-beta-D-xylosyl-(1-->2)-beta-D-galactoside (4), kaempferol-3-O-alpha-L-rhamnosyl-(1-->6)-beta-D-glucoside (5), (2S,3S)-taxifolin 3-O-beta-D-glucoside (6) ,4-hydroxy cinnamic acid (7), (+)-cycloolivil (8), pinoresinol beta-D-glucoside (9), squalene (10). Among them compounds 1,5-7,10 were isolated from the Eucommia genus for the first time. In the DPPH free radical scavenging assay, compound 2 exhibited significant activity (IC50 13.7 micromol x L(-1)), compared with vitamin C (IC50 59.9 micromol x L(-1)); compounds 1, 3 and 9 showed moderate activity (IC50 161,137, 214 micromol x L(-1)), compared with 2,6-di-tert-butyl-4-methylphenol (IC50 236 micromol x L(-1)); compound 4 and 6 showed weak activity (IC50 264, 299 micromol x L(-1)). PMID:25039180

Yang, Fang; Yue, Zheng-Gang; Wang, Xin; Zhang, Xiu-Peng; Chai, Jiang; Cui, Jiu-Cheng; Song, Xiao-Mei; Mei, Qi-Bing

2014-04-01

444

Cyclic electron transfer in plant leaf  

PubMed Central

The turnover of linear and cyclic electron flows has been determined in fragments of dark-adapted spinach leaf by measuring the kinetics of fluorescence yield and of the transmembrane electrical potential changes under saturating illumination. When Photosystem (PS) II is inhibited, a cyclic electron flow around PSI operates transiently at a rate close to the maximum turnover of photosynthesis. When PSII is active, the cyclic flow operates with a similar rate during the first seconds of illumination. The high efficiency of the cyclic pathway implies that the cyclic and the linear transfer chains are structurally isolated one from the other. We propose that the cyclic pathway operates within a supercomplex including one PSI, one cytochrome bf complex, one plastocyanin, and one ferredoxin. The cyclic process induces the synthesis of ATP needed for the activation of the Benson–Calvin cycle. A fraction of PSI (?50%), not included in the supercomplexes, participates in the linear pathway. The illumination would induce a dissociation of the supercomplexes that progressively increases the fraction of PSI involved in the linear pathway. PMID:12119384

Joliot, Pierre; Joliot, Anne

2002-01-01

445

Oak Leaf Roller and Springtime Defoliation of Live Oak Trees  

E-print Network

This publication explains how to minimize damage to live oak trees by the oak leaf roller and an associated caterpillar species, which occur throughout Texas but are most damaging in the Hill Country and South Texas....

Drees, Bastiaan M.

2004-03-26

446

Maximizing daily canopy photosynthesis with respect to the leaf nitrogen allocation pattern in the canopy  

Microsoft Academic Search

A model of daily canopy photosynthesis was constructed taking light and leaf nitrogen distribution in the canopy into consideration. It was applied to a canopy of Solidago altissima. Both irradiance and nitrogen concentration per unit leaf area decreased exponentially with increasing cumulative leaf area from the top of the canopy. The ph