SEARCH · PubMed Health

Results for “Droughts”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 73 records · Page 4Linked to original sources

PubMed2005

Mycorrhizal impact on drought stress tolerance of rose plants probed by chlorophyll a fluorescence, proline content and visual scoring.

Micropropagated rose plants (Rosa hybrida L., cv. New Dawn) were inoculated with the arbuscular mycorrhizal (AM) fungus Glomus intraradices (Schenk and Smith) and subjected to different drought regimens. The dual objectives of these experiments were to investigate the mechanism and the extent to which AM can prevent drought damages and whether physiological analyses reveal enhanced drought tolerance of an economically important plant such as the rose. In a long-term drought experiment with four different water regimens, visual scoring of wilt symptoms affirmed that AM in a selected host-symbiont combination increased plant performance. This effect was mostly expressed if moderate drought stress was constantly applied over a long period. In a short-term experiment in which severe drought stress was implemented and plants were allowed to recover after 4 or 9 days, no visual differences between mycorrhizal and non-mycorrhizal roses were observed. Therefore, the early physiological steps conferring drought tolerance were prone to investigation. Proline content in leaves proved to be an unsuitable marker for AM-induced drought tolerance, whereas analysis of chlorophyll a fluorescence using the JIP test (collecting stress-induced changes of the polyphasic O-J-I-P fluorescence kinetics in a non-destructive tissue screening) was more explanatory. Parameters derived from this test could describe the extent of foliar stress response and help to differentiate physiological mechanisms of stress tolerance. AM led to a more intense electron flow and a higher productive photosynthetic activity at several sites of the photosynthetic electron transport chain. A K step, known as a stress indicator of general character, appeared in the fluorescence transient only in drought-stressed non-mycorrhizal plants; conversely, the data elucidate a stabilising effect of AM on the oxygen-evolving complex at the donor site of photosystem (PS) II and at the electron-transport chain between PS II and PS I. If drought stress intensity was reduced by a prolonged and milder drying phase, these significant tolerance features were less pronounced or missing, indicating a possible threshold level for mycorrhizal tolerance induction.

Adaptation, Physiological↗

PubMedDate not supplied

Mapping QTLs associated with drought resistance in sorghum (Sorghum bicolor L. Moench).

Drought is a major abiotic stress factor limiting crop production. Identification of genetic factors involved in plant responses to drought stress will provide a solid foundation to improve drought resistance. Sorghum is well adapted to hot dry environments and regarded as a model for studying drought resistance among the grasses. Significant progress in genome mapping of this crop has also been made. In sorghum, rapid premature leaf death generally occurs when water is limited during the grain filling period. Premature leaf senescence, in turn, leads to charcoal rot, stalk lodging, and significant yield loss. More than 80% of commercial sorghum hybrids in the United States are grown under non-irrigated conditions and although most of them have pre-flowering drought resistance, many do not have any significant post-flowering drought resistance. Stay-green is one form of drought resistance mechanism, which gives sorghum resistance to premature senescence under soil moisture stress during the post-flowering period. Quantitative trait locus (QTL) studies with recombinant inbred lines (RILs) and near-isogenic lines (NILs) identified several genomic regions associated with resistance to pre-flowering and post-flowering drought stress. We have identified four genomic regions associated with the stay-green trait using a RIL population developed from B35 x Tx7000. These four major stay-green QTLs were consistently identified in all field trials and accounted for 53.5% of the phenotypic variance. We review the progress in mapping stay-green QTLs as a component of drought resistance in sorghum. The molecular genetic dissection of the QTLs affecting stay-green will provide further opportunities to elucidate the underlying physiological mechanisms involved in drought resistance in sorghum and other grasses.

Adaptation, Physiological↗

PubMed2005

Regional vegetation die-off in response to global-change-type drought.

Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a piñon) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions.

Climate↗

PubMed2006

Whole plant responses, key processes, and adaptation to drought stress: the case of rice.

Most high-yielding rice cultivars developed for irrigated conditions, including the widely grown lowland variety IR64, are highly susceptible to drought stress. This limits their adoption in rainfed rice environments where there is a risk of water shortage during the growing season. Mapping studies using lowland-by-upland rice populations have provided limited information about the genetic basis of variation in yield under drought. One approach to simultaneously improve and understand rice drought tolerance is to generate backcross populations, select superior lines in managed stress environments, and then evaluate which features of the selected lines differ from the recurrent parent. This approach was been taken with IR64, using a range of tolerant and susceptible cultivars as donor parents. Yields of the selected lines measured across 13 widely contracting water environments were generally greater than IR64, but genotype-by-environment effects were large. Traits expected to vary between IR64 and selected lines are plant height, because many donors were not semi-dwarf types, and maturity, because selection in a terminal stress environment is expected to favour earliness. In these experiments it was found that some lines that performed better under upland drought were indeed taller than IR64, but that shorter lines with good yield under drought could also be identified. In trials where drought stress developed in previously flooded (lowland) fields, height was not associated with performance. There was little change in maturity with selection. Other notable differences between IR64 and the selected backcross lines were in their responses to applied ABA and ethylene in greenhouse experiments at the vegetative stage and in leaf rolling observed under chronic upland stress in the field. These observations are consistent with the hypothesis that adaptive responses to drought can effectively allow for improved performance across a broad range of water environments. The results indicate that the yield of IR64 under drought can be significantly improved by backcrossing with selection under stress. In target environments where drought is infrequent but significant in certain years, improved IR64 with greater drought tolerance would be a valuable option for farmers.

Adaptation, Physiological↗

PubMed1995

Stomatal and mesophyll limitations of photosynthesis in black spruce seedlings during multiple cycles of drought.

Container-grown black spruce (Picea mariana (Mill.) B.S.P.) seedlings were planted in trays containing a sand and peat mixture, and placed in a climate-controlled greenhouse. One group of seedlings was kept well-watered, and another group was subjected to three cycles of drought. Gas exchange analysis showed that mesophyll photosynthetic function was largely unimpaired by drought. In contrast, stomatal conductance was sensitive to drought, although it became less sensitive with each drought cycle. Both stomatal and mesophyll conductances increased with time in control and drought-stressed seedlings, but mesophyll conductance increased with time more rapidly than did stomatal conductance. Limitation of photosynthetic rate was dominated by the mesophyll. In control seedlings, relative stomatal limitation increased from 6 to 16% by the end of the experiment. In drought-stressed seedlings, relative stomatal limitation of photosynthesis reached 40% during the first drought, but decreased to near control values immediately after rewatering. Because the third, most severe drought had only a minor effect on stomatal conductance, relative stomatal limitation of photosynthesis was similar to that in control seedlings by the end of the experiment. Inhibition of ontogenetic change during drought stress may be responsible for the apparent acclimation of mesophyll photosynthetic processes. We conclude that it would be more effective to select for high photosynthetic capacity than for reduced stomatal sensitivity when breeding for increased drought resistance in black spruce seedlings.

Journal Article↗

PubMed2001

Effects of drought stress and high density stem inoculations with Leptographium wingfieldii on hydraulic properties of young Scots pine trees.

We examined drought-induced changes in susceptibility of potted Scots pine (Pinus sylvestris L.) trees to a bark-beetle associated fungus (Leptographium wingfieldii Morelet, from the bark beetle Tomicus piniperda L.). Five-year-old field-grown trees were transplanted to 50-l pots and grown for 1 year before the treatments were applied. Trees in the drought treatment were subjected to several successive, 3-week-long drought cycles, with predawn water potential dropping below -2 MPa at peak drought intensity. The experimental drought cycles were more severe than the natural drought episodes usually recorded in Scots pine stands. Trees were then mass-inoculated with L. wingfieldii at a density close to the critical threshold density of inoculations (400 m(-2)) above which tree resistance is overcome. Inoculation of well-watered trees resulted in induced reaction zones around the inoculation points and very limited damage (resinosis) in the sapwood. Drought alone had no long-lasting consequences on tree water relations, except for a decrease in hydraulic conductance in the youngest segments of the main stem. However, the combination of mass-inoculation and drought stress after inoculation resulted in a dramatic loss of stem hydraulic conductivity that was paralleled by conspicuous damage to the sapwood (resinosis, drying and blue staining). There was a close correlation between amount of visible sapwood damage and loss of hydraulic conductivity. The intensity of induced reactions in the phloem was unaffected by drought stress. We conclude that tree defence against L. wingfieldii is decreased during severe drought stress, resulting in changes in the spread and action of the fungus in the sapwood but not in the phloem.

Animals↗

PubMed2002

Growth rate and survivorship of drought: CO2 effects on the presumed tradeoff in seedlings of five woody legumes.

Traits that promote rapid growth and seedling recruitment when water is plentiful may become a liability when seedlings encounter drought. We tested the hypothesis that CO2 enrichment reinforces any tradeoff between growth rate and drought tolerance by exaggerating interspecific differences in maximum relative growth rate (RGR) and survivorship of drought among seedlings of five woody legumes. We studied invasive species of grasslands that differ in distribution along a rainfall gradient. Survivorship of drought at ambient CO2 concentration ([CO2]) was negatively related to RGR in well-watered seedlings in one of two experiments, but the relationship was weak because interspecific differences in RGR were small. Contrary to our hypothesis, there was no significant relationship among well-watered seedlings between RGR at ambient [CO2] and either the relative or absolute increase in RGR at elevated [CO2]. As predicted, however, CO2 enrichment reinforced interspecific differences in survivorship of seedlings exposed to similar rates of soil water depletion. Doubling [CO2] improved seedling survivorship of the most drought-tolerant species throughout the period of soil water depletion, but did not consistently affect survivorship of more drought-sensitive species. Midday xylem pressure potentials of drought-treated seedlings were less negative at elevated [CO2] than at ambient [CO2], but no other measured trait was consistently correlated with improved survivorship at high [CO2]. Carbon dioxide enrichment may not reinforce species differences in RGR, but could exaggerate interspecific differences in drought tolerance. To the extent that seedling persistence in grasslands correlates with drought survivorship, our results indicate a positive effect of CO2 enrichment on recruitment of woody legumes that are currently tolerant of drought.

Acacia↗

PubMed2005

Wisdom from the drought: recommendations from a consultative conference.

OBJECTIVE: Drought is a serious and recurring problem for rural and remote Australia. This paper reports the proceedings of a consultative conference concerning the mental health effects of drought held at the Centre for Rural and Remote Mental Health, Orange, in December 2003. The conference objective was to record the collective experience of government and non-government agencies dealing with the effects of drought in rural areas and to collate information for the development of a mental health strategy for future drought. DESIGN: Participants were recruited in consultation with rural mental health organisations. Questions about mental health service strategies to minimise and respond to the mental health impact of the drought were posed to participants. Qualitative data were collected using a Nominal Group Technique. SETTING: The Centre for Rural and Remote Mental Health, Bloomfield Hospital, Orange, New South Wales. PARTICIPANTS: Twenty-three professionals participated, including representatives from New South Wales Health, Mental Health, and Agriculture; the Department of Community Services, and Rural Financial Counsellors. MAIN OUTCOME MEASURE: Qualitative analysis of participant responses. RESULTS: Three general strategies emerged as the most beneficial in minimising adverse mental health outcomes in times of drought: community-building and education about the physical, financial and mental health effects of drought; co-operation between and co-ordination of agencies in delivering mental health and other drought support; and continuity and planning of improved mental health services. CONCLUSIONS: Drought has a serious effect on the mental health of communities. It is important to plan a response beyond the end of the drought, bringing together different government and non-government agencies to build community capacity to address common mental health needs.

Congresses as Topic↗

PubMed2026

Repeated drought induces a reproducible DNA methylation response associated with gene expression in Quercus lobata.

UNLABELLED: Long-lived trees must continually adjust to environmental change and face sustained climatic shifts over their lifetimes. One increasingly important challenge is the rising frequency of drought caused by climate change. Environmentally responsive DNA methylation is widespread in plants, but whether it contributes to gene expression during environmental stress remains unclear, particularly in long-lived trees. Here, we integrated long read methylomes and transcriptomes from valley oak ( Quercus lobata ) seedlings exposed to repeated drought and well-watered treatments. Repeated drought induced a reproducible DNA methylation response that repeatedly targeted the same genomic regions despite turnover of individual methylated sites. These repeatedly targeted regions were transposable elements (TEs) located near genes. Genes adjacent to CHH-methylated TEs were enriched for core drought-response pathways, including abscisic acid signaling, osmotic adjustment and cell-wall remodeling, and remained transcriptionally activated under drought. However, higher CHH methylation levels were associated with progressively smaller transcriptional responses, suggesting that environmentally responsive DNA methylation influences how strongly drought- response genes are activated rather than simply switching them on or off. At the same time, greater CHH methylation was associated with continued repression of nearby TEs, suggesting that this response may simultaneously regulate gene activity while maintaining genome stability. Together, these findings identify a reproducible genome- regulatory response associated with repeated environmental stress in a long-lived tree. By repeatedly targeting the same genomic regions despite turnover of individual sites, this response provides a framework for how long-lived trees repeatedly adjust gene expression while maintaining genome stability during environmental change. SIGNIFICANCE STATEMENT: Plants cannot escape environmental change, and trees must repeatedly respond to stresses, such as drought, over lifetimes spanning decades to centuries. Yet little is known about the molecular mechanisms that make this remarkable resilience possible. Using a widespread California oak, we show that repeated drought repeatedly induced the same DNA methylation pattern in the same parts of the genome, even though the differentially methylated individual sites changed between drought events. This pattern was linked to how strongly drought-response genes were activated, suggesting that trees repeatedly deploy the same molecular program to respond to environmental stress. Our findings provide a new framework for understanding how long-lived organisms repeatedly adjust to changing climates.

Journal Article↗

PubMed2026

Scion-based drought stress memory affects potato response to water deficit.

A scion-based stress memory signal, which was derived from drought-primed potato plants, was transmitted to new potato plants generated through vegetative reproduction. This affected potato tuber yield. Drought is one of the most significant threats to agricultural productivity worldwide. The cultivated potato (Solanum tuberosum L.) is a crop species that is sensitive to drought stress. This study investigated the impact of scion-based drought stress memory on tuber yield, physiological parameters, gene expression, and DNA methylation in the vegetative progeny of grafted plants. The tuber progeny plants remembered the drought stress signal transmitted from the drought-primed scion. Significant changes were observed in the expression of genes, primarily those related to photosynthetic metabolic pathways, as well as those associated with chromatin remodeling, DNA repair, and the plant's response to abiotic stresses. The gene expression landscape corresponded with variability in chlorophyll fluorescence parameters. In the first and the second generation of vegetatively propagated plants, scion-based memory had a positive effect on tuber yield. This was achieved by buffering the decline in yield caused by drought, as compared to plants grown under control conditions. Whole-genome bisulfite sequencing analysis revealed no correlation between changes in DNA methylation and gene expression. Drought-induced alterations in DNA methylation were erased in the second progeny generation. We propose that there is a direct causal relationship between scion-based memory of drought stress and photosynthetic efficiency, as well as potato tuber productivity.

Solanum tuberosum↗

PubMed2002

Quantitative trait loci associated with traits determining grain and stover yield in pearl millet under terminal drought-stress conditions.

Drought stress during the reproductive stage is one of the most important environmental factors reducing the grain yield and yield stability of pearl millet. A QTL mapping approach has been used in this study to understand the genetic and physiological basis of drought tolerance in pearl millet and to provide a more-targeted approach to improving the drought tolerance and yield of this crop in water-limited environments. The aim was to identify specific genomic regions associated with the enhanced tolerance of pearl millet to drought stress during the flowering and grain-filling stages. Testcrosses of a set of mapping-population progenies, derived from a cross of two inbred pollinators that differed in their response to drought, were evaluated in a range of managed terminal drought-stress environments. A number of genomic regions were associated with drought tolerance in terms of both grain yield and its components. For example, a QTL associated with grain yield per se and for the drought tolerance of grain yield mapped on linkage group 2 and explained up to 23% of the phenotypic variation. Some of these QTLs were common across stress environments whereas others were specific to only a particular stress environment. All the QTLs that contributed to increased drought tolerance did so either through better than average maintenance (compared to non-stress environments) of harvest index, or harvest index and biomass productivity. It is concluded that there is considerable potential for marker-assisted backcross transfer of selected QTLs to the elite parent of the mapping population and for their general use in the improvement of pearl millet productivity in water-limited environments.

Journal Article↗

PubMed2004

El Niño droughts and their effects on tree species composition and diversity in tropical rain forests.

In this study I investigated the effects of the extreme, 1997/98 El Niño related drought on tree mortality and understorey light conditions of logged and unlogged tropical rain forest in the Indonesian province of East Kalimantan (Borneo). My objectives were to test (1) whether drought had a significant effect on tree mortality and understorey light conditions, (2) whether this effect was greater in logged than in undisturbed forest, (3) if the expected change in tree mortality and light conditions had an effect on Macaranga pioneer seedling and sapling densities, and (4) which (a)biotic factors influenced tree mortality during the drought. The 1997/1998 drought led to an additional tree mortality of 11.2, 18.1, and 22.7% in undisturbed, old logged and recently logged forest, respectively. Mortality was highest in logged forests, due to extremely high mortality of pioneer Macaranga trees (65.4%). Canopy openness was significantly higher during the drought than during the non-drought year (6.0, 8.6 and 10.4 vs 3.7, 3.8 and 3.7 in undisturbed, old logged and recently logged forest, respectively) and was positively correlated with the number of dead standing trees. The increase in light in the understorey was accompanied by a 30 to 300-fold increase in pioneer Macaranga seedling densities. Factors affecting tree mortality during drought were (1) tree species successional status, (2) tree size, and (3) tree location with respect to soil moisture. Tree density and basal area per surface unit had no influence on tree mortality during drought. The results of this study show that extreme droughts, such as those associated with El Niño events, can affect the tree species composition and diversity of tropical forests in two ways: (1) by disproportionate mortality of certain tree species groups and tree size classes, and (2) by changing the light environment in the forest understorey, thereby affecting the recruitment and growth conditions of small and immature trees.

Biodiversity↗

PubMed2006

Arbuscular mycorrhizal fungi enhance fruit growth and quality of chile ancho (Capsicum annuum L. cv San Luis) plants exposed to drought.

The effect of arbuscular mycorrhizal fungi (AMF) and drought on fruit quality was evaluated in chile ancho (Capsicum annuum L. cv San Luis). AMF treatments were (1) Glomus fasciculatum (AMFG), (2) a fungal species consortium from the forest "Los Tuxtla" in Mexico (AMFT), (3) a fungal species consortium from the Sonorian desert in Mexico (AMFD), and (4) a noninoculated control (NAMF). Plants were exposed to a 26-day drought cycle. Fruit quality was determined by measuring size (length, width, and pedicel length), color, chlorophyll, and carotenoid concentration. Under nondrought conditions, AMFG produced fruits that were 13% wider and 15% longer than the NAMF treatment. Under nondrought conditions, fruit fresh weight was 25% greater in the AMFG treatment compared to the NAMF. Under drought, fruits in the AMFT and AMFD treatments showed fresh weights similar to those in the NAMF treatment not subjected to drought. Fruits of the AMFG treatment subjected to drought showed the same color intensity and chlorophyll content as those of the nondroughted NAMF treatment and carotenoid content increased 1.4 times compared to that in the NAMF not exposed to drought. It is interesting to note that fruits in the AMFD treatment subjected to drought and the NAMF treatment not exposed to drought reached the same size. AMFD treatment increased the concentration of carotenes (1.4 times) under nondrought conditions and the concentration of xanthophylls (1.5 times) under drought when compared to the nondroughted NAMF treatment.

Capsicum↗

PubMed2004

Drought-induced responses of photosynthesis and antioxidant metabolism in higher plants.

Environmental stresses trigger a wide variety of plant responses, ranging from altered gene expression and cellular metabolism to changes in growth rates and crop yields. A plethora of plant reactions exist to circumvent the potentially harmful effects caused by a wide range of both abiotic and biotic stresses, including light, drought, salinity, high temperatures, and pathogen infections. Among the environmental stresses, drought stress is one of the most adverse factors of plant growth and productivity. Understanding the biochemical and molecular responses to drought is essential for a holistic perception of plant resistance mechanisms to water-limited conditions. Drought stress progressively decreases CO2 assimilation rates due to reduced stomatal conductance. Drought stress also induces reduction in the contents and activities of photosynthetic carbon reduction cycle enzymes, including the key enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase. The critical roles of proline and glycine-betaine, as well as the role of abscisic acid (ABA), under drought stress conditions have been actively researched to understand the tolerance of plants to dehydration. In addition, drought stress-induced generation of active oxygen species is well recognized at the cellular level and is tightly controlled at both the production and consumption levels in vivo, through increased antioxidative systems. Knowledge of sensing and signaling pathways, including ABA-mediated changes in response to drought stress, is essential to improve crop management. This review focuses on the ability and strategies of higher plants to respond and adapt to drought stress.

Abscisic Acid↗

PubMed2000

Drought disturbance from climate change: response of United States forests.

Predicted changes in climate have raised concerns about potential impacts on terrestrial forest ecosystem productivity, biogeochemical cycling, and the availability of water resources. This review summarizes characteristics of drought typical to the major forest regions of the United States, future drought projections, and important features of plant and forest community response to drought. Research needs and strategies for coping with future drought are also discussed. Notwithstanding uncertainties surrounding the magnitude and direction of future climate change, and the net impact on soil water availability to forests, a number of conclusions can be made regarding the sensitivity of forests to future drought. The primary response will be a reduction in net primary production and stand water use, which are driven by reductions in stomatal conductance. Mortality of small stature plants (i.e. seedlings and saplings) is a likely consequence of severe drought. In comparison, deep rooting and substantial reserves of carbohydrates and nutrients make mature trees less susceptible to water limitations caused by severe or prolonged drought. However, severe or prolonged drought may render even mature trees more susceptible to insects or disease. Drought-induced reductions in decomposition rates may cause a buildup of organic material on the forest floor, with ramifications for fire regimes and nutrient cycling. Although early model predictions of climate change impacts suggested extensive forest dieback and species migration, more recent analyses suggest that catastrophic dieback will be a local phenomenon, and changes in forest composition will be a relatively gradual process. Better climate predictions at regional scales, with a higher temporal resolution (months to days), coupled with carefully designed, field-based experiments that incorporate multiple driving variables (e.g. temperature and CO2), will advance our ability to predict the response of different forest regions to climate change.

Animals↗

PubMed1999

Enzymatic activity and gene expression under water stress of phospholipase D in two cultivars of Vigna unguiculata L. Walp. differing in drought tolerance.

Phospholipase D, a major lipid-degrading enzyme in plants, was studied in two cultivars of Vigna unguiculata L.Walp, differing in their tolerance to drought (cv. EPACE-1, drought-tolerant, and cv. 1183, drought-susceptible). Enzymatic activities, measured with 14C-PC as substrate, increased when plants were submitted to water stress, the increase being much higher in the drought-sensitive cultivar. A 2911 bp cDNA encoding a putative phospholipase D (VuPLD1) was isolated from a cDNA library prepared from V. unguiculata leaves. The deduced amino acid sequence (809 residues) shows 85.5% identity and 91.3% similarity to that of PLD from Ricinus communis. The expression of the VuPLD1 gene in the leaves is differently modulated by water deficit, depending on the intensity of stress and the tolerance or sensitivity of the plants. In the drought-susceptible V. unguiculata cv. 1183, it readily increased under water stress, reaching maximum values at mild water deficit (-1.5 MPa). In the drought-tolerant cv. EPACE-1, VuPLD1 mRNA remained low throughout the whole drought treatment. Dehydration of leaves led to a dramatic increase in transcript level in both cultivars. Changes in protein amounts semi-quantified by immunoblotting correlated well with variations in transcript steady-state level. Taken together, these results showed that phospholipase D in cowpea plants is essentially regulated at the transcriptional level, and that gene expression is strongly stimulated even by moderate water deficit in the drought-sensitive plant. On the contrary, the drought-tolerant plant presents a remarkable stability of PLD gene expression in conditions of water stress.

Amino Acid Sequence↗

PubMedDate not supplied

Monitoring large-scale changes in transcript abundance in drought- and salt-stressed barley.

Responses to drought and salinity in barley (Hordeum vulgare L. cv. Tokak) were monitored by microarray hybridization of 1463 DNA elements derived from cDNA libraries of 6 and 10 h drought-stressed plants. Functional identities indicated that many cDNAs in these libraries were associated with drought stress. About 38% of the transcripts were novel and functionally unknown. Hybridization experiments were analyzed for drought- and salinity-regulated sequences, with significant changes defined as a deviation from the control exceeding 2.5-fold. Responses of transcripts showed stress-dependent expression patterns and time courses. Nearly 15% of all transcripts were either up- or down-regulated under drought stress, while NaCl led to a change in 5% of the transcripts (24 h, 150 mM NaCl). Transcripts that showed significant up-regulation under drought stress are exemplified by jasmonate-responsive, metallothionein-like, late-embryogenesis-abundant (LEA) and ABA-responsive proteins. Most drastic down-regulation in a category was observed for photosynthesis-related functions. Up-regulation under both drought and salt stress was restricted to ESTs for metallothionein-like and LEA proteins, while increases in ubiquitin-related transcripts characterized salt stress. A number of functionally unknown transcripts from cDNA libraries of drought-stressed plants showed up-regulation by drought but down-regulation by salt stress, documenting how precisely transcript profiles report different growth conditions and environments.

Disasters↗

PubMed2006

Circumvention of over-excitation of PSII by maintaining electron transport rate in leaves of four cotton genotypes developed under long-term drought.

We investigated the patterns of response to a long-term drought in the field in cotton cultivars (genotypes) with known differences in their drought tolerance. Four cotton genotypes with varying physiological and morphological traits, suited to different cropping conditions, were grown in the field and subjected to a long-term moderate drought. In general, cotton leaves developed under drought had significantly higher area-based leaf nitrogen content (N (area)) than those under well irrigation. Droughted plants showed a lower light-saturated net photosynthetic rate (A (sat)) with lower stomatal conductance (g (s)) and intercellular CO (2) concentration (C (i)) than irrigated ones. Based on the responses of A (sat) to g (s) and C (i), there was no decreasing trend in A (sat) at a given g (s) and C (i) in droughted leaves, suggesting that the decline in A (sat) in field-grown cotton plants under a long-term drought can be attributed mainly to stomatal closure, but not to nonstomatal limitations. There was little evidence of an increase in thermal energy dissipation as indicated by the lack of a decrease in the photochemical efficiency of open PSII (F (v)'/F (m)') in droughted plants. On the basis of electron transport (ETR) and photochemical quenching (q (P)), however, we found evidence indicating that droughted cotton plants can circumvent the risk of excessive excitation energy in photosystem (PS) II by maintaining higher electron transport rates associated with higher N (area), even while photosynthetic rates were reduced by stomatal closure.

Biological Transport↗