Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Droughts”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed2006

Dissection of additive, epistatic effect and Q x E interaction of quantitative trait loci influencing stigma exsertion under water stress in rice.

Four flowering related traits, spikelet number per panicle (SNP), percentage of single exserted stigma (PSES), dual exserted stigma (PDES) and total exserted stigma (PES) of a RI population with 185 lines under water stress and non-stress conditions for 2 years, were investigated in a drought tolerance screening facility. ANOVA results showed high significance between years, lines, and water stress treatments, together with interactions among them in pairs. Highest phenotypic correlation was found between PSES and PES (r = 0.9752***), followed by PDES and PES (r = 0.7150***), and PSES and PDES (r = 0.5424***). Based on a linkage map of 203 SSR markers, six main effect QTLs were detected for SNP and three or four main effect QTLs were associated with PSES, PDES and PES under stress or non-stress conditions. There were one to nine pairs of epistatic QTLs influencing SNP and stigma exsertion. The contribution rates of additive and epistatic effects seemed to be in a low magnitude for most cases (0.76%-9.92%) while a few QTLs or QTL pairs explained more than 10% of total variance. Some main effect QTL and epistasis were commonly detected among PSES, PDES and PES, explaining the high positive correlation between them. Few QTLs were detected under both water stress and non-stress condition, implying that drought had severe impact on the genetic behaviors of both spikelet number and stigma exsertion.

Crops, Agricultural↗
PubMed2001

Productivity and carbon isotope discrimination in durum wheat organs under a Mediterranean climate.

For durum wheat, we promote the use of carbon isotope discrimination (delta) as an indirect selection criterion for transpiration efficiency and grain yield (GY), and we identify the most effective organ for characterising delta genotypic variation. A field experiment was conducted in the South of France on 144 accessions, with a drought period occurring from February to June. Harvest index (HI), GY and delta (delta L, flag leaf; delta A, awn, delta G grain) were measured. Significant positive genetic correlations were noted between delta and both GY and HI. A larger genotypic variation and a higher broad-sense heritability were noted for delta G compared to delta L and delta A. delta G correlated better with GY and HI than delta L and delta A, showing that delta G could provide a better assessment of genotypic behaviours under drought during grain filling. Moreover, the indirect selection based on delta G (even when evaluated with one replicate) appeared more efficient than the direct selection for grain yield. This result emphasised the potential value of grain carbon isotope discrimination as a criterion for grain yield improvement under stressed Mediterranean conditions.

Carbon Isotopes↗
PubMed2003

Comparative water relations of adult and juvenile tortoise beetles: differences among sympatric species.

Relative abundance of two sympatric tortoise beetles varies between drought and 'wet' years. Differing abilities to conserve water may influence beetle survival in changing environments. Cuticular permeability (CP), percentage of total body water (%TBW), rate of water loss and percentage of body lipid content were determined for five juvenile stages and female and male adults of two sympatric species of chrysomelid beetles, the golden tortoise beetle, Charidotella bicolor (F.) and the mottled tortoise beetle, Deloyala guttata (Olivier). There were significant differences in %TBW and lipid content among juvenile stages. Second instars had the greatest difference in CP (37.98 and 11.13 microgcm(-2)h(-1)mmHg(-1) for golden and mottled tortoise beetles, respectively). Mottled tortoise beetles had lower CP and greater %TBW compared with golden tortoise beetles, suggesting that they can conserve a greater amount of water and may tolerate drier environmental conditions. This study suggests that juvenile response to environmental water stress may differentially affect the survival of early instars and thus affect the relative abundance of adult beetles in the field. This is supported by the low relative abundance of golden tortoise beetle larvae in a drought year and the higher abundance in two 'wet' years.

Aging↗
PubMed2004

Climate effects on stream nitrate concentrations at 16 forested catchments in south central Ontario.

Increased nitrate (NO3) concentrations in streamwaters draining forested catchments are reportedly an early indicator of nitrogen (N) saturation. Nitrate concentrations in streams draining 16 forested catchments in south central Ontario were monitored over a 16-year period, during which time N bulk deposition was relatively constant (approximately 9 kg ha(-1) yr(-1)). Mean annual NO3 concentrations in streams were both highly variable among catchments and among years, although patterns of annual concentration were similar among many catchments. Coherence analysis identified two stream groupings. Shallow soils, moderate slopes, low NO3 concentration, and a large wetland component characterized the first group. The second group had primarily upland characteristics including deeper soils, steeper slopes, higher NO3 concentrations, and a much smaller wetland component. Patterns in NO3 concentration in wetland-influenced streams appeared to be related to summer drought and cumulative frost depth, whereas NO3 concentrations in upland-draining streams appeared to be related to both mean annual air temperature and summer drought. Because a number of different climate parameters as well as the physical character of the catchments apparently influence NO3 export, NO3 concentrations in streams are not a good indicator of N saturation in this region.

Climate↗
PubMed2004

Climate-induced episodic acidification of streams in central ontario.

In this study we have analyzed the hydrochemical effect of drought conditions during 311 hydrological episodes in nine headwater streams in central Ontario over the past 20 years. Acid Neutralization Capacity (ANC) was logarithmically correlated (p<0.05) to antecedent discharge in eight of the nine streams, with the largest decline in ANC occurring after low antecedent flow. In eight of the nine streams SO4(2-) was the most important driving mechanism of ANC decline, but dilution as well as organic acidity was important in several streams. No decrease in the SO4(2-) driven ANC decline was observed over the 20 year study period despite a approximately 40% reduction in SO4(2-) deposition. The strong correlation between ANC decline and low antecedent discharge demonstrates that episodic acidification during rain events is strongly associated with preceding drought conditions, especially in wetland-dominated catchments. The results have important implications for recoveryfrom acidification, especially in northern ecosystems where climate scenarios forecast that warmer and drier conditions will be more common.

Acid Rain↗
PubMed2001

Protein and lysine content, grain yield, and other technological traits in durum wheat under Mediterranean conditions.

A major problem for durum wheat production in the Mediterranean region is yield fluctuation. This fluctuation is a result of year-to-year variation in precipitation and heat stress during grain growth, which is typical of the Mediterranean climate. Both yield stability and good quality are needed in adapted durum wheat ideotypes. Ten durum wheat cultivars differing in drought resistance were grown during 1998, under both rainfed and irrigated conditions, at three sites in southern Spain. The main traits studied were protein and lysine content, grain yield, test weight, SDS sedimentation, semolina color, and grain vitreousness. Results show a high influence of site on all traits. Only test weight (TW), SDS sedimentation, grain vitreousness, and protein per kernel appeared to be determined also by cultivar effect. Vitreousness was positively correlated with TW (r = 0.48**) and semolina color (r = 0.46**). An inverse relationship was found between grain yield and protein content. Regression of cultivar mean values of protein content and grain yield showed a negative correlation (r = -0.72***), probably due to dilution of protein by non-nitrogen compounds and reduced starch accumulation in the grain under drought conditions. Lysine content was negatively associated with protein content (r = -0.86***), indicating the difficulty of a simultaneous breeding for both characteristics.

Climate↗
PubMed2000

Properties of herbage in relation to equine dysautonomia: biochemical composition and antioxidant and prooxidant actions.

To investigate the etiology of equine dysautonomia (ED), a degenerative polyneuropathy affecting grazing horses, the biochemical composition and antioxidant/prooxidant activities of aqueous extracts of plants collected from ED pastures were determined. Plants collected immediately after an outbreak of ED had reduced antioxidant and weak prooxidant activities when compared with control plants (plants collected from ED pastures out of ED season and control plants from ED pastures that were grown under favorable conditions). ED plants also had significantly increased concentrations of fructose and low molecular weight phenolic compounds, significantly more of one amino acid zone (probably valine), significantly less tartaric acid, and a nonsignificant decrease in ascorbic acid content when compared with control plants from ED pastures that were grown under favorable conditions. These findings suggest that ED plants may be under oxidative stress, possibly due to chilling, drought, or fungal colonization. However, experimental drought and chilling of plants did not reproduce the biochemical alterations identified in ED plants. It is possible that the altered biochemical content of ingested plants may contribute, directly or indirectly, to the development of ED in grazing horses.

Animal Feed↗
PubMed1997

Structural organization, expression and promoter activity of a cold-stress-inducible gene of potato (Solanum tuberosum L.)

Cold storage of potato tubers at 4 degrees C is associated with the accumulation of several cold-induced transcripts. By using a previously characterized cDNA (CI7) as probe, we isolated and sequenced the corresponding ci7 gene. The putative promoter of ci7 contains sequence elements that have been shown to mediate expression of stress-responsive genes of Arabidopsis thaliana. CI7 transcripts were differentially induced in response to cold, drought, high salt or exogenous ABA treatment in potato tubers and leaves. Whereas accumulation of CI7 transcript during cold storage occurred within days, induction of CI7 transcript in response to drought, ABA and salt occurred rapidly within few hours. In tubers, accumulation of CI7 protein in response to abiotic stresses and ABA was small when compared to transcript levels. In leaves, the CI7 protein was undetectable after all treatments tested. 3 kb of the 5'-flanking ci7 promoter region were fused to the GUS reporter gene and introduced into S. tuberosum plants. The analysis of tubers of independent transgenic lines did not reveal significant induction of enzymatic GUS activity in response to low temperature. When RNA gel blotting was used to analyze the level of induction of the GUS gene driven by the ci7 promoter, the heterologous GUS fusion was, however, strongly responsive to low temperature. Nuclear run-on transcription studies of the ci7 gene, in comparison with RNA gel blot analyses of the transgenic plants, indicated that most of the temperature-regulated expression of the ci7 gene in tubers may be accounted for by post-transcriptional control mechanisms.

Abscisic Acid↗
PubMed1997

Expression in anthers of two genes encoding Brassica oleracea transmembrane channel proteins.

Screening of an anther cDNA expression library resulted in the isolation of two almost identical cDNA clones, termed mipA and mipB, showing homology with sequences encoding transmembrane channel proteins from the MIP family. Both clones were expressed in several tissues, but not in pollen. MipA was preferentially expressed in the surrounding sporophytic tissues of stamens. Anthers subjected to drought were induced to accumulate even more mip transcripts, which was entirely due to higher mipA gene expression. On basis of isolation procedures, sequence homology and drought inducibility of mipA we conclude that the encoded proteins probably are constituents of the pollen coat and are aquaporins.

Amino Acid Sequence↗
PubMed1999

The HD-Zip gene ATHB6 in Arabidopsis is expressed in developing leaves, roots and carpels and up-regulated by water deficit conditions.

Homeodomain-leucine zipper (HD-Zip) proteins are transcription factors as yet found only in plants. We have characterized one HD-Zip gene, ATHB6, from Arabidopsis thaliana. ATHB6 was expressed constitutively in seedlings, but significantly up-regulated in seedlings subjected to water deficit, osmotic stress or exogenous treatment with abscisic acid (ABA), an induction being detectable within 30 min. The ATHB6 induction was impaired in the two ABA-insensitive mutants, abi1 and abi2, but unaffected in the abi3 mutation. The induction was ABA-dependent, since no increase in ATHB6 transcript was detected in the ABA-deficient mutant aba-3 subjected to drought treatment. These results suggest that ATHB6 may act downstream to both ABI1 and ABI2 in a signal transduction pathway mediating a drought stress response. A translational fusion of the ATHB6 promoter with the reporter gene GUS (ATHB6::GUS) in transgenic A. thaliana plants showed high-level expression in leaf primordia. Expression in developing cotyledons, leaves, roots and carpels was restricted to regions of cell division and/or differentiation. The expression in the cotyledons was detectable in the epidermis and high in the stomatal cells. In mature cotyledons and leaves the marker gene was expressed only in the vascular tissue. These expression data suggest ATHB6 to have a function related to cell division and/or differentiation in developing organs.

Abscisic Acid↗
PubMed2000

Abscisic acid biosynthesis in tomato: regulation of zeaxanthin epoxidase and 9-cis-epoxycarotenoid dioxygenase mRNAs by light/dark cycles, water stress and abscisic acid.

Two genes encoding enzymes in the abscisic acid (ABA) biosynthesis pathway, zeaxanthin epoxidase (ZEP) and 9-cis-epoxycarotenoid dioxygenase (NCED), have previously been cloned by transposon tagging in Nicotiana plumbaginifolia and maize respectively. We demonstrate that antisense down-regulation of the tomato gene LeZEP1 causes accumulation of zeaxanthin in leaves, suggesting that this gene also encodes ZEP. LeNCED1 is known to encode NCED from characterization of a null mutation (notabilis) in tomato. We have used LeZEP1 and LeNCED1 as probes to study gene expression in leaves and roots of whole plants given drought treatments, during light/dark cycles, and during dehydration of detached leaves. During drought stress, NCED mRNA increased in both leaves and roots, whereas ZEP mRNA increased in roots but not leaves. When detached leaves were dehydrated, NCED mRNA responded rapidly to small reductions in water content. Using a detached leaf system with ABA-deficient mutants and ABA feeding, we investigated the possibility that NCED mRNA is regulated by the end product of the pathway, ABA, but found no evidence that this is the case. We also describe strong diurnal expression patterns for both ZEP and NCED, with the two genes displaying distinctly different patterns. ZEP mRNA oscillated with a phase very similar to light-harvesting complex II (LHCII) mRNA, and oscillations continued in a 48 h dark period. NCED mRNA oscillated with a different phase and remained low during a 48 h dark period. Implications for regulation of water stress-induced ABA biosynthesis are discussed.

Abscisic Acid↗
PubMedDate not supplied

Chromosome regions and stress-related sequences involved in resistance to abiotic stress in Triticeae.

Drought, low temperature and salinity are the most important abiotic stress factors limiting crop productivity. A genomic map of major loci and QTLs affecting stress tolerance in Triticeae identified the crucial role of the group 5 chromosomes, where the highest concentration of QTLs and major loci controlling plant's adaptation to the environment (heading date, frost and salt tolerance) has been found. In addition, a conserved region with a major role in drought tolerance has been localized to the group 7 chromosomes. Extensive molecular biological studies have led to the cloning of many stress-related genes and responsive elements. The expression of some stress-related genes was shown to be linked to stress-tolerant QTLs, suggesting that these genes may represent the molecular basis of stress tolerance. The development of suitable genetic tools will allow the role of stress-related sequences and their relationship with stress-tolerant loci to be established in the near future.

Adaptation, Physiological↗
PubMed2002

Identification and mapping of a putative stress response regulator gene in barley.

Plants respond to environmental stress with a number of physiological and developmental changes. Water deficit is one of the major factors limiting plant growth and development and crop productivity. One response of plants to water deficit is accumulation of abscisic acid (ABA). An increase of ABA is responsible for the induction of many genes, presumably some of which contribute to drought tolerance. Analysis of gene expression in barley seedling shoots by differential display reverse transcriptase polymerase chain reaction (DDRT-PCR) led to the isolation of several drought-, cold- and ABA-induced partial cDNA fragments. Here we extensively characterize one of these cDNAs, designated DD6. First, a larger cDNA was extended from DD6 by 5'-RACE (rapid amplification of cDNA ends). Subsequently, the corresponding gene was isolated by screening a barley BAC library, and the sequences of the transcribed and flanking regions were determined. The deduced amino acid sequence has similarity to an Arabidopsis hypothetical protein and to a human and mouse DNA-binding protein. The corresponding gene, named Srg6 (stress-responsive gene), was mapped in a barley doubled haploid mapping population to chromosome 7H between markers ABC455 and salfp76, within a region that previously has been linked to osmotic adaptation in barley and other grass genomes.

Abscisic Acid↗
PubMed2004

Ozone exposures and implications for vegetation in rural areas of the central Appalachian Mountains, U.S.A.

The United States is making the transition from the 1979 1 hr maximum ozone standard to the newly adopted 8 hr ozone standard (3 yr average of the 4th highest maximum 8 hr ozone concentration). Consequently, we analyzed and compared ozone concentrations under both standards from a variety of monitoring sites throughout the central Appalachian region of Kentucky (KY), West Virginia (WV), and Virginia (VA). Data from 1988-1999 were used to determine how ozone exposure between the two metrics compared for remote sites. Most sites exceeded the 1 hr standard in 1988-1990 due to the 3 yr averaging and multiple high ozone concentrations that occurred over the region in 1988. All sites were in compliance with the 1 hr standard every year after 1991. It was much more common for the ozone exposure to exceed the 8 hr standard, particularly from 1997-1999. Many sites showed exceedences beginning in 1995; Big Meadows (VA) exceeded the 8 hr standard all years except 1994 and 1996. Response of vegetation to ozone in these areas was determined using the combination of W126 values (sigmoidally weighted exposure index), the number of hours that average concentrations > or = 0.10 ppm (N100), and the presence of moderate or more extreme droughts. In general, W126 and N100 values suggested that negative vegetation growth responses over most of the 12 yr would have been minimal for most sites, even for those exceeding ozone standards. Drought-induced stomatal closures would have overridden more extreme negative growth responses at all but the Big Meadows site in 1988.

Air Pollutants↗
PubMed2003

Repression of formate dehydrogenase in Solanum tuberosum increases steady-state levels of formate and accelerates the accumulation of proline in response to osmotic stress.

Formate dehydrogenase (FDH, EC 1.2.1.2.) is a soluble mitochondrial enzyme capable of oxidizing formate into CO2 in the presence of NAD+. It is abundant in non-green tissues and scarce in photosynthetic tissues. Under stress, FDH transcripts (and protein) accumulate in leaves, and leaf mitochondria acquire the ability to use formate as a respiratory substrate. In this paper, we describe the analysis of transgenic potato plants under-expressing FDH, obtained in order to understand the physiological function of FDH. Plants expressing low FDH activities were selected and the study was focused on a line (AS23) showing no detectable FDH activity. AS23 plants were morphologically indistinguishable from control plants, and grew normally under standard conditions. However, mitochondria isolated from AS23 tubers could not use formate as a respiratory substrate. Steady-state levels of formate were higher in AS23 leaves and tubers than in control plants. Tubers of untransformed plants oxidized 14C formate into 14CO2 but AS23 tubers accumulated it. In order to reveal a possible phenotype under stress conditions, control and AS23 plants were submitted to drought and cold. These treatments dramatically induced FDH transcripts in control plants but, whatever the growth conditions, no 1.4 kb FDH transcripts were detected in leaves of AS23 plants. Amongst various biochemical and molecular differences between stressed AS23 and control plants, the most striking was a dramatically faster accumulation of proline in the leaves of drought-stressed plants under-expressing FDH.

Amino Acids↗
PubMed2004

An expression analysis of a gene family encoding plasma membrane aquaporins in response to abiotic stresses in Arabidopsis thaliana.

Aquaporin belongs to a highly conserved group of membrane proteins called major intrinsic proteins that facilitate water transport across biological membranes. The genome of Arabidopsis encodes 35 aquaporin genes with 13 homologs in the plasma membrane intrinsic protein (PIP) subgroup. However, the function of each individual aquaporin isoform and the integrated function of plant aquaporins under various physiological conditions remain unclear. As a step toward understanding the aquaporin function in plants under various environmental stimuli, the expressions of a gene family encoding 13 PIPs in Arabidopsis thaliana under various abiotic stress conditions including drought, cold, and high salinity, or abscisic acid (ABA) treatment were investigated by a quantitative real-time reverse transcription-PCR analysis. Several PIP genes were predominantly expressed either in the roots or in the flowers. The expressions of both the highly expressed aquaporins including PIP1;1, PIP1;2, and PIP2;7 and the weakly expressed aquaporins such as PIP1;4, PIP2;1, PIP2;4, and PIP2;5 were modulated by external stimuli. The analyses of our data revealed that only the PIP2;5 was up-regulated by cold treatment, and most of the PIP genes were down-regulated by cold stress. Marked up- or down-regulation in PIP expression was observed by drought stress, whereas PIP genes were less-severely modulated by high salinity. The responsiveness of each aquaporin to ABA were different, implying that the regulation of aquaporin expression involves both ABA-dependent and ABA-independent signaling pathways. Together, our comprehensive expression profile of the 13 members of the PIP gene family provides novel basis to allocate the stress-related biological function to each PIP gene.

Abscisic Acid↗
PubMed2003

Regulation of phosphoenolpyruvate carboxylase in Pinus halepensis needles submitted to ozone and water stress.

Effects of ozone and/or drought stresses on phosphoenolpyruvate carboxylase (PEPc, EC 4.1.1.31) regulation in Pinus halepensis Mill. needles were assessed over 3 months in controlled conditions. Whereas moderated water stress applied to Aleppo pine had no effect on PEPc activity compared to the control, which was probably related to the high tolerance of this species to drought, ozone stress induced a dramatic increase of PEPc activity in pine needles. This stimulation of the anaplerotic pathway could provide substrates to repair processes, well known for being enhanced upon ozone exposure. The ozone-increased PEPc activity was related, to a certain extent, to an increase in protein and mRNA levels. The possible role of the stimulation of the phosphorylation status of the enzyme in the increased PEPc activity under ozone was also investigated. Following the demonstration of the existence of the phosphorylation site at the N terminal part of Aleppo pine PEPc, it was shown that, under ozone treatment, the light/dark PEPc activity ratio and the Ki (malate) for PEPc were increased. This strengthens the hypothesis of an ozone-related post-translational process, which could be part of an adaptation of the plants to prolonged stress. When ozone and water stress were applied in combination, the enhancement in PEPc activity was only related to changes in gene expression. This difference in PEPc regulation, compared to the effect of single stress, could be the consequence of the specific action of each stress on the enzyme. This study brings new insights into the regulation of PEPc in a C3 plant, Aleppo pine under these stresses. A different regulatory mechanism of PEPc is occurring according to the stress. The physiological implications of the increase in PEPc activity in response to ozone and/or water stress are discussed.

Journal Article↗
PubMed2003

Hydraulic adjustment in jack pine and black spruce seedlings under controlled cycles of dehydration and rehydration.

Drought adjustments were compared in black spruce (Picea mariana[Mill] B.S.P), and jack pine (Pinus banksiana[Lamb.]) by subjecting seedlings to five cycles of dehydration and rehydration. A computer-controlled root misting chamber system, supplied low (-1.5 MPa), moderate (-2.0 MPa), and severe (-2.5 MPa) dehydration, respectively, in cycles 1, 3 and 5. Although cell water relations failed to adjust to chronic dehydration, there was limited osmotic adjustment in black spruce (cycle 3), and water was re-allocated from the apoplast to the symplast in jack pine (cycles 1 and 3). Dehydration postponement was more important than dehydration tolerance. Jack pine was better able to postpone dehydration than black spruce. Specific conductivity, the hydraulic conductivity per unit stem cross-sectional area, was lower in jack pine and slower to decline during chronic dehydration. When specific conductivity was corrected for the greater leaf area in black spruce, the leaf-specific conductivity did not differ in the two species. There was no increase in needle leakage in jack pine and stomata in jack pine seedlings reopened fully after rehydration. Black spruce was more of a 'water spender', and less water stress (-2.0 MPa, cycle 3) was required to lower specific conductivity, compared to jack pine (-2.5 MPa, cycle 5). Leakage from needle membranes increased in black spruce, and stomata failed to reopen after rewatering (cycles 3 and 5). A greater needle area, smaller root system, and a higher specific conductivity lowered the water stress threshold for cavitation in black spruce, which is confined to moister sites in the boreal forest. Jack pine had a larger root system, smaller needle area and lower specific conductivity than black spruce. Because of these static features, jack pine is more drought tolerant and it is often found on sites that are too hot and dry for black spruce.

Journal Article↗