scholarly journals Drought response strategies and hydraulic traits contribute to mechanistic understanding of plant dry-down to hydraulic failure

2019 ◽  
Vol 39 (6) ◽  
pp. 910-924 ◽  
Author(s):  
Chris J Blackman ◽  
Danielle Creek ◽  
Chelsea Maier ◽  
Michael J Aspinwall ◽  
John E Drake ◽  
...  
Keyword(s):  
Drought Tolerance ◽  
Tree Mortality ◽  
Stomatal Closure ◽  
Safety Margin ◽  
Critical Levels ◽  
Response Strategies ◽  
Hydraulic Failure ◽  
Dry Down ◽  
Leaf Succulence ◽  
And Function

Abstract Drought-induced tree mortality alters forest structure and function, yet our ability to predict when and how different species die during drought remains limited. Here, we explore how stomatal control and drought tolerance traits influence the duration of drought stress leading to critical levels of hydraulic failure. We examined the growth and physiological responses of four woody plant species (three angiosperms and one conifer) representing a range of water-use and drought tolerance traits over the course of two controlled drought–recovery cycles followed by an extended dry-down. At the end of the final dry-down phase, we measured changes in biomass ratios and leaf carbohydrates. During the first and second drought phases, plants of all species closed their stomata in response to decreasing water potential, but only the conifer species avoided water potentials associated with xylem embolism as a result of early stomatal closure relative to thresholds of hydraulic dysfunction. The time it took plants to reach critical levels of water stress during the final dry-down was similar among the angiosperms (ranging from 39 to 57 days to stemP88) and longer in the conifer (156 days to stemP50). Plant dry-down time was influenced by a number of factors including species stomatal-hydraulic safety margin (gsP90 – stemP50), as well as leaf succulence and minimum stomatal conductance. Leaf carbohydrate reserves (starch) were not depleted at the end of the final dry-down in any species, irrespective of the duration of drought. These findings highlight the need to consider multiple structural and functional traits when predicting the timing of hydraulic failure in plants.

scholarly journals Carbon starvation during drought-induced tree mortality – are we chasing a myth?

2015 ◽  
Vol 2 ◽  
pp. e005 ◽  
Author(s):  
Henrik Hartmann
Keyword(s):  
Tree Mortality ◽  
Stomatal Closure ◽  
Carbon Starvation ◽  
Carbon Limitation ◽  
Functional Roles ◽  
C Storage ◽  
Hydraulic Failure ◽  
Lethal Level ◽  
Potential Link ◽  
C Assimilation

Drought-induced tree mortality has received much attention in the recent past. McDowell et al.’s (2008) hydraulic framework links tree hydraulics with carbon dynamics and proposes two non-exclusive mortality mechanisms: carbon starvation (CS) and hydraulic failure (HF). CS is often referred to as the (partial) depletion of non-structural carbohydrates (NSC) in response to stomatal closure, reduced C assimilation and sustained C storage dependency during longer droughts. HF describes a lethal level of xylem dysfunction from runaway embolism during severe droughts. While HF can be readily inferred from the percentage loss of conductivity in vascular tissues at the time of death, CS is much more difficult to assess.Starvation is usually defined as a lack of food leading to suffering or death. In plants photosynthetic sugars play many functional roles, not only as a source of catabolic energy. For example, sugars are important for osmotic regulation of cell pressure and recent studies suggest a potential link between xylem parenchyma sugars and embolism repair following drought. Hence, carbon limitation could have a direct impact on tree hydraulics and HF; however, empirical evidence for such a mechanism is still inconclusive.Although HF appears to be predominant during drought mortality, our limited understanding of the roles of NSC in hydraulic function precludes any premature refutation of CS as a mechanism in drought-induced tree mortality.

scholarly journals Adaptive plasticity in plant traits increases time to hydraulic failure under drought in a foundation tree

2020 ◽  
Author(s):  
A Challis ◽  
CJ Blackman ◽  
CW Ahrens ◽  
BE Medlyn ◽  
PD Rymer ◽  
...  
Keyword(s):  
Climate Change ◽  
Drought Tolerance ◽  
Water Deficit ◽  
Plant Traits ◽  
Stomatal Closure ◽  
Adaptive Plasticity ◽  
List Type ◽  
Environment Interaction ◽  
Forest Trees ◽  
Hydraulic Failure

SummaryThe viability of forest trees, in response to climate change-associated drought, will depend on their capacity to survive through genetic adaptation and phenotypic plasticity in drought tolerance traits. Genotypes with enhanced plasticity for drought tolerance (adaptive plasticity) will have a greater ability to persist and delay the onset of hydraulic failure.Corymbia calophylla populations from two contrasting climate-origins (warm-dry and cool-wet) were grown under well-watered and chronic soil water deficit treatments in large containers. Hydraulic and allometric traits were measured and then trees were dried-down to critical levels of drought stress.Significant plasticity was detected in the warm-dry population in response to water-deficit, with adjustments in drought tolerance traits that resulted in longer dry-down times from stomatal closure to 88% loss of stem hydraulic conductance (time to hydraulic failure, THF). Plasticity was limited in the cool-wet population, indicating a significant genotype-by-environment interaction in THF.Our findings contribute information on intraspecific variation in key drought tolerance traits and THF. It highlights the need to quantify adaptive capacity in populations of forest trees facing climate change-type drought to improve predictions of forest die-back. Corymbia calophylla may benefit from assisted gene migration by introducing adaptive warm-dry populations into vulnerable cool-wet population regions.

Prediction of temperate broadleaf tree species mortality in arid limestone habitats with stomatal safety margins

2019 ◽  
Vol 39 (8) ◽  
pp. 1428-1437 ◽  
Author(s):  
Zhicheng Chen ◽  
Shan Li ◽  
Junwei Luan ◽  
Yongtao Zhang ◽  
Shidan Zhu ◽  
...  
Keyword(s):  
Tree Species ◽  
Tree Mortality ◽  
Vascular System ◽  
Stomatal Closure ◽  
Survival Rates ◽  
Safety Margin ◽  
Xylem Embolism ◽  
Safety Margins ◽  
Broadleaf Tree ◽  
Embolism Resistance

Abstract A growing body of evidence highlights the occurrence of increased widespread tree mortality during climate change-associated severe droughts; however, in situ long-term drought experiments with multispecies communities for the prediction of tree mortality and exploration of related mechanisms are rather limited in natural environments. We conducted a 7-year afforestation trial with 20 drought-resistant broadleaf tree species in an arid limestone habitat in northern China, where the species displayed a broad range of survival rates. The stomatal and xylem hydraulic traits of all the species were measured. We found that species’ stomatal closure points were strongly related to their xylem embolism resistance and xylem minimum water potential but not to their survival rates. Hydraulic failure of the vascular system appeared to be the main cause of tree mortality, and the stomatal safety margin was a better predictor of tree mortality than the traditionally considered xylem embolism resistance and hydraulic safety margin. We recommend the stomatal safety margin as the indicator for predicting drought-induced tree mortality and for selecting tree species in future forest restorations in arid regions.

scholarly journals The sequence and thresholds of leaf hydraulic traits underlying grapevine varietal differences in drought tolerance

2020 ◽  
Vol 71 (14) ◽  
pp. 4333-4344 ◽  
Author(s):  
Silvina Dayer ◽  
José Carlos Herrera ◽  
Zhanwu Dai ◽  
Régis Burlett ◽  
Laurent J Lamarque ◽  
...  
Keyword(s):  
Drought Tolerance ◽  
Water Potential ◽  
Water Use ◽  
Safety Margin ◽  
Multiple Traits ◽  
Hydraulic Failure ◽  
Drought Tolerant ◽  
Leaf Level ◽  
Hydraulic Safety Margin

Abstract Adapting agriculture to climate change is driving the need for the selection and breeding of drought-tolerant crops. The aim of this study was to identify key drought tolerance traits and determine the sequence of their water potential thresholds across three grapevine cultivars with contrasting water use behaviors, Grenache, Syrah, and Semillon. We quantified differences in water use between cultivars and combined this with the determination of other leaf-level traits (e.g. leaf turgor loss point, π TLP), leaf vulnerability to embolism (P50), and the hydraulic safety margin (HSM P50). Semillon exhibited the highest maximum transpiration (Emax), and lowest sensitivity of canopy stomatal conductance (Gc) to vapor pressure deficit (VPD), followed by Syrah and Grenache. Increasing Emax was correlated with more negative water potential at which stomata close (Pgs90), π TLP, and P50, suggesting that increasing water use is associated with hydraulic traits allowing gas exchange under more negative water potentials. Nevertheless, all the cultivars closed their stomata prior to leaf embolism formation. Modeling simulations demonstrated that despite a narrower HSM, Grenache takes longer to reach thresholds of hydraulic failure due to its conservative water use. This study demonstrates that the relationships between leaf hydraulic traits are complex and interactive, stressing the importance of integrating multiple traits in characterizing drought tolerance.

Intraspecific variation in drought susceptibility in Eucalyptus globulus is linked to differences in leaf vulnerability

2019 ◽  
Vol 46 (3) ◽  
pp. 286 ◽  
Author(s):  
Christopher J. Lucani ◽  
Timothy J. Brodribb ◽  
Greg Jordan ◽  
Patrick J. Mitchell
Keyword(s):  
Drought Tolerance ◽  
Intraspecific Variation ◽  
Eucalyptus Globulus ◽  
Forest Tree ◽  
Species Variation ◽  
Important Species ◽  
Phenotypic Differences ◽  
Hydraulic Failure ◽  
Xylem Vulnerability ◽  
Alternative Approach

Understanding intraspecific variation in the vulnerability of the xylem to hydraulic failure during drought is critical in predicting the response of forest tree species to climate change. However, few studies have assessed intraspecific variation in this trait, and a likely limitation is the large number of measurements required to generate the standard ‘vulnerability curve’ used to assess hydraulic failure. Here we explore an alternative approach that requires fewer measurements, and assess within species variation in leaf xylem vulnerability in Eucalyptus globulus Labill., an ecologically and economically important species with known genetic variation in drought tolerance. Using this approach we demonstrate significant phenotypic differences and evidence of plasticity among two provenances with contrasting drought tolerance.

Physiological and morphological responses to water stress in Aegilops biuncialis and Triticum aestivum genotypes with differing tolerance to drought

2004 ◽  
Vol 31 (12) ◽  
pp. 1149 ◽  
Author(s):  
István Molnár ◽  
László Gáspár ◽  
Éva Sárvári ◽  
Sándor Dulai ◽  
Borbála Hoffmann ◽  
...  
Keyword(s):  
Growth Rate ◽  
Triticum Aestivum ◽  
Water Stress ◽  
Drought Tolerance ◽  
Osmotic Stress ◽  
Biomass Production ◽  
Water Loss ◽  
Stomatal Closure ◽  
Co2 Assimilation ◽  
Wheat Genotypes

The physiological and morphological responses to water stress induced by polyethylene glycol (PEG) or by withholding water were investigated in Aegilops biuncialis Vis. genotypes differing in the annual rainfall of their habitat (1050, 550 and 225 mm year–1) and in Triticum aestivum L. wheat genotypes differing in drought tolerance. A decrease in the osmotic pressure of the nutrient solution from –0.027 to –1.8 MPa resulted in significant water loss, a low degree of stomatal closure and a decrease in the intercellular CO2 concentration (Ci) in Aegilops genotypes originating from dry habitats, while in wheat genotypes high osmotic stress increased stomatal closure, resulting in a low level of water loss and high Ci. Nevertheless, under saturating light at normal atmospheric CO2 levels, the rate of CO2 assimilation was higher for the Aegilops accessions, under high osmotic stress, than for the wheat genotypes. Moreover, in the wheat genotypes CO2 assimilation exhibited less or no O2 sensitivity. These physiological responses were manifested in changes in the growth rate and biomass production, since Aegilops (Ae550, Ae225) genotypes retained a higher growth rate (especially in the roots), biomass production and yield formation after drought stress than wheat. These results indicate that Aegilops genotypes, originating from a dry habitat have better drought tolerance than wheat, making them good candidates for improving the drought tolerance of wheat through intergeneric crossing.

scholarly journals Drought Stress in Grain Legumes: Effects, Tolerance Mechanisms and Management

Agronomy ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2374
Author(s):  
Marium Khatun ◽  
Sumi Sarkar ◽  
Farzana Mustafa Era ◽  
A. K. M. Mominul Islam ◽  
Md. Parvez Anwar ◽  
...  
Keyword(s):  
Drought Stress ◽  
Drought Tolerance ◽  
Association Studies ◽  
Stomatal Closure ◽  
Grain Legumes ◽  
Grain Legume ◽  
Developmental Cycle ◽  
Genome Wide Association Studies ◽  
Tolerance Mechanisms ◽  
Drought Tolerant

Grain legumes are important sources of proteins, essential micronutrients and vitamins and for human nutrition. Climate change, including drought, is a severe threat to grain legume production throughout the world. In this review, the morpho-physiological, physio-biochemical and molecular levels of drought stress in legumes are described. Moreover, different tolerance mechanisms, such as the morphological, physio-biochemical and molecular mechanisms of legumes, are also reviewed. Moreover, various management approaches for mitigating the drought stress effects in grain legumes are assessed. Reduced leaf area, shoot and root growth, chlorophyll content, stomatal conductance, CO2 influx, nutrient uptake and translocation, and water-use efficiency (WUE) ultimately affect legume yields. The yield loss of grain legumes varies from species to species, even variety to variety within a species, depending upon the severity of drought stress and several other factors, such as phenology, soil textures and agro-climatic conditions. Closure of stomata leads to an increase in leaf temperature by reducing the transpiration rate, and, so, the legume plant faces another stress under drought stress. The biosynthesis of reactive oxygen species (ROS) is the most detrimental effect of drought stress. Legumes can adapt to the drought stress by changing their morphology, physiology and molecular mechanism. Improved root system architecture (RSA), reduced number and size of leaves, stress-induced phytohormone, stomatal closure, antioxidant defense system, solute accumulation (e.g., proline) and altered gene expression play a crucial role in drought tolerance. Several agronomic, breeding both conventional and molecular, biotechnological approaches are used as management practices for developing a drought-tolerant legume without affecting crop yield. Exogenous application of plant-growth regulators (PGRs), osmoprotectants and inoculation by Rhizobacteria and arbuscular mycorrhizal fungi promotes drought tolerance in legumes. Genome-wide association studies (GWASs), genomic selection (GS), marker-assisted selection (MAS), OMICS-based technology and CRISPR/Cas9 make the breeding work easy and save time in the developmental cycle to get resistant legumes. Several drought-resistant grain legumes, such as the chickpea, faba bean, common bean and pigeon pea, were developed by different institutions. Drought-tolerant transgenic legumes, for example, chickpeas, are developed by introgressing desired genes through breeding and biotechnological approaches. Several quantitative trait loci (QTLs), candidate genes occupying drought-tolerant traits, are identified from a variety of grain legumes, but not all are under proper implementation. Hence, more research should be conducted to improve the drought-tolerant traits of grain legumes for avoiding losses during drought.

scholarly journals miR2105 regulates ABA biosynthesis via OsbZIP86-OsNCED3 module to contribute to drought tolerance in rice

2021 ◽  
Author(s):  
Weiwei Gao ◽  
Mingkang Li ◽  
Songguang Yang ◽  
Chunzhi Gao ◽  
Yan Su ◽  
...  
Keyword(s):  
Drought Stress ◽  
Drought Tolerance ◽  
Transgenic Rice ◽  
Crucial Role ◽  
Agronomic Traits ◽  
Stomatal Closure ◽  
Plant Tolerance ◽  
Rice Plants ◽  
Transgenic Rice Plants ◽  
Aba Biosynthesis

AbstractInduced abscisic acid (ABA) biosynthesis plays an important role in plant tolerance to abiotic stresses, including drought, cold and salinity. However, regulation pathway of the ABA biosynthesis in response to stresses is unclear. Here, we identified a rice miRNA, osa-miR2105 (miR2105), which plays a crucial role in ABA biosynthesis under drought stress. Analysis of expression, transgenic rice and cleavage site showed that OsbZIP86 is a target gene of miR2105. Subcellular localization and luciferase activity assays showed that OsbZIP86 is a nuclear transcription factor. In vivo and in vitro analyses showed that OsbZIP86 directly binds to the promoter of OsNCED3, and interacts with OsSAPK10, resulting in enhanced-expression of OsNCED3. Transgenic rice plants with knock-down of miR2105 or overexpression of OsbZIP86 showed higher ABA content, more tolerance to drought, a lower rate of water loss, more stomatal closure than wild type rice ZH11 under drought stress. These rice plants showed no penalty with respect to agronomic traits under normal conditions. By contrast, transgenic rice plants with miR2105 overexpression, OsbZIP86 downregulation, or OsbZIP86 knockout displayed less tolerance to drought stress and other phenotypes. Collectively, our results show that a regulatory network of ‘miR2105-OsSAPK10/OsbZIP86-OsNCED3’ control ABA biosynthesis in response to drought stress.One-sentence summary‘miR2105-OsbZIP86-OsNCED3’ module plays crucial role in mediating ABA biosynthesis to contribute to drought tolerance with no penalty with respect to agronomic traits under normal conditions.

scholarly journals Dead or dying? Quantifying the point of no return from hydraulic failure in drought‐induced tree mortality

2019 ◽  
Vol 223 (4) ◽  
pp. 1834-1843 ◽  
Author(s):  
William M. Hammond ◽  
Kailiang Yu ◽  
Luke A. Wilson ◽  
Rodney E. Will ◽  
William R. L. Anderegg ◽  
...  
Keyword(s):  
Tree Mortality ◽  
Hydraulic Failure ◽  
Point Of No Return

scholarly journals Arabidopsis thaliana trehalose-6-phosphate phosphatase gene TPPI enhances drought tolerance by regulating stomatal apertures

2020 ◽  
Vol 71 (14) ◽  
pp. 4285-4297 ◽  
Author(s):  
Qingfang Lin ◽  
Song Wang ◽  
Yihang Dao ◽  
Jianyong Wang ◽  
Kai Wang
Keyword(s):  
Drought Stress ◽  
Drought Tolerance ◽  
Stomatal Closure ◽  
Primary Root ◽  
Stomatal Aperture ◽  
Wild Type ◽  
Trehalose Metabolism ◽  
Use Efficiency ◽  
Responsive Element ◽  
Primary Root Length

Abstract Transpiration occurs through stomata. The alteration of stomatal apertures in response to drought stress is an important process associated with water use efficiency (WUE). Trehalose-6-phosphate phosphatase (TPP) family genes have been reported to participate in adjustment of stomatal aperture. However, there have been no reports of the trehalose metabolism pathway genes improving WUE, and the upstream signalling pathway modulating these genes is not clear. Here, we demonstrate that a member of the TPP gene family, AtTPPI, confers drought resistance and improves WUE by decreasing stomatal apertures and improving root architecture. The reduced expression of AtTPPI caused a drought-sensitive phenotype, while its overexpression significantly increased drought tolerance. Abscisic acid (ABA)-induced stomatal closure experiments confirmed that AtTPPI mutation increased the stomatal aperture compared with that of wild-type plants; in contrast, overexpression plants had smaller stomatal apertures than those of wild-type plants. Moreover, AtTPPI mutation also caused stunted primary root length and compromised auxin transport, while overexpression plants had longer primary root lengths. Yeast one-hybrid assays showed that ABA-responsive element-binding factor1 (ABF1), ABF2, and ABF4 directly regulated AtTPPI expression. In summary, the way in which AtTPPI responds to drought stress suggests that AtTPPI-mediated stomatal regulation is an important mechanism to cope with drought stress and improve WUE.

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