Differences In Drought Tolerance Research Articles

Negative effects of water deficit on cocoa tree yield are partially mitigated by irrigation and potassium application

Yields of most tropical crops are strongly reduced by drought, but this may be partially mitigated by irrigation and potassium application. Understanding the mechanisms regulating these relationships is essential to select crop varieties reaching high yield under environmental stress. We conducted a 2-year field experiment (2020–2022) to investigate the effects of seasonal irrigation, potassium application and their interaction on cocoa reproduction and yield, using six genotypes in Côte d’Ivoire. Potassium application increased pod number and size, contributing significantly to annual yield, but this effect was conditional to soil water availability. Similarly, irrigation when combined with potassium application almost doubled yield from 1.5 to 3.0 kg/tree (2000 kg ha−1 yr−1 to 4000 kg ha−1 yr−1, respectively). This yield effect was mostly the result of positive effects of irrigation on pod number per tree and, to a lesser extent, due to its positive effects on bean number per pod and bean mass. Irrigation effects on pod number were associated with an increased number of cherelles whereas the larger pod number during the major harvest compared to the minor harvest was associated with lower cherelle wilt. We also found a more than two-fold genotypic difference in yield, with the genotypes CI02 and CI03 and to a lesser extent hybrid M having lower yields having lower yields than the genotype CI01. These genotypic yield differences were associated with differences in both cherelle wilt and initial cherelle production rates. The effects of withholding irrigation on yield were significantly dependent on the genotype, reflecting a potential genotypic difference in drought tolerance. The development of climate adaptive strategies for cocoa production requires integrating effects of irrigation, potassium application and cocoa genotype on yields. Future research should focus on unraveling the underlying genotypic and ecophysiological mechanisms of the results presented here, and identifying other potential approaches to enhance the resilience of cocoa to increasing water deficit under climate change.

Differential drought tolerance among dichondra (Dichondra repens) genotypes in relation to alterations in chlorophyll metabolism, osmotic adjustment, and accumulation of organic metabolites.

Dichondra (Dichondra repens) is an important ground cover plant for landscaping and establishment of green space, but adaptive mechanism of drought tolerance is not well understood in this species. This study was conducted to compare differential response to drought stress among three genotypes (Dr5, Duliujiang, and Dr29) based on integrated physiological, ultrastructural, and metabolic assays. Results showed that drought significantly inhibited photosynthesis, accelerated lipids peroxidation, and also disrupted water balance and cellular metabolism in dichondra plants. Dr5 showed better photochemical efficiency of photosystem II and water homeostasis, less oxidative damage, and more stable chlorophyll metabolism than Duliujinag or Dr29 in response to drought stress. In addition, Dr5 accumulated more amino acids, organic acids, and other metabolites, which was good for maintaining better antioxidant capacity, osmotic homeostasis, and energy metabolism under drought stress. Drought tolerance of Duliujiang was lower than Dr5, but better than Dr29, which could be positively correlated with accumulations of sucrose, maltitol, aconitic acid, isocitric acid, and shikimic acid due to critical roles of these metabolites in osmotic adjustment and metabolic homeostasis. Current findings provide insights into understanding of underlying mechanism of metabolic regulation in dichondra species. Dr5 could be used as an important drought-tolerant resource for cultivation and water-saving breeding.

Transcriptome analysis reveals regulatory mechanisms of different drought-tolerant Gleditsia sinensis seedlings under drought stress

BackgroundGleditsia sinensis is a significant tree species from both ecological and economic perspectives. However, its growth is hampered by temporary droughts during the seedling stage, thereby impeding the development of the G. sinensis industry. Drought stress and rehydration of semi-annual potted seedlings using an artificial simulated water control method. RNA sequencing (RNA-seq) analyses were conducted on leaves collected from highly resistant (HR) and highly susceptible (HS) seedling families at five different stages during the process of drought stress and rehydration to investigate their gene expression patterns.ResultsThe differentially expressed genes (DEGs) were predominantly enriched in pathways related to “chloroplast” (GO:0009507), “photosynthesis” (GO:0015979), “plant hormone signal transduction” (map04075), “flavonoid biosynthesis” (map00941), “stress response”, “response to reactive oxygen species (ROS)” (GO:0000302), “signal transduction” (GO:0007165) in G. sinensis HR and HS families exposed to mild and severe drought stress. Additionally, the pathways related to “plant hormone signal transduction” (map04075), and osmoregulation were also enriched. The difference in drought tolerance between the two families of G. sinensis may be associated with “transmembrane transporter activity” (GO:0022857), “stress response”, “hormones and signal transduction” (GO:0007165), “cutin, suberine and wax biosynthesis” (map00073), “ribosome” (map03010), “photosynthesis” (map00195), “sugar metabolism”, and others. An enrichment analysis of DEGs under severe drought stress suggests that the drought tolerance of both families may be related to “water-soluble vitamin metabolic process” (GO:0006767), “photosynthesis” (map00195), “plant hormone signal transduction” (map04075), “starch and sucrose metabolism” (map00500), and “galactose metabolism” (map00052). Osmoregulation-related genes such as delta-1-pyrroline-5-carboxylate synthase (P5CS), Amino acid permease (AAP), Amino acid permease 2 (AAP2) and Trehalose-phosphate synthase (TPS), as well as the antioxidant enzyme L-ascorbate peroxidase 6 (APX6), may be significant genes involved in drought tolerance in G. sinensis. Five genes were selected randomly to validate the RNA-seq results using quantitative real-time PCR (RT-qPCR) and they indicated that the transcriptome data were reliable.ConclusionsThe study presents information on the molecular regulation of the drought tolerance mechanism in G. sinensis and provides a reference for further research on the molecular mechanisms involved in drought tolerance breeding of G. sinensis.

Physiological responses and transcriptome analysis of soybean under gradual water deficit.

Soybean is an important food and oil crop widely cultivated globally. However, water deficit can seriously affect the yield and quality of soybeans. In order to ensure the stability and increase of soybean yield and improve agricultural water use efficiency (WUE), research on improving drought tolerance and the efficiency of water utilization of soybeans under drought stress has become particularly important. This study utilized the drought-tolerant variety Heinong 44 (HN44) and the drought-sensitive variety Suinong 14 (SN14) to analyze physiological responses and transcriptome changes during the gradual water deficit at the early seed-filling stage. The results indicated that under drought conditions, HN44 had smaller stomata, higher stomatal density, and lower stomatal conductance (Gs) and transpiration rate as compared to SN14. Additionally, HN44 had a higher abscisic acid (ABA) content and faster changes in stomatal morphology and Gs to maintain a dynamic balance between net photosynthetic rate (Pn) and Gs. Additionally, drought-tolerant variety HN44 had high instantaneous WUE under water deficit. Further, HN44 retained a high level of superoxide dismutase (SOD) activity and proline content, mitigating malondialdehyde (MDA) accumulation and drought-induced damage. Comprehensive analysis of transcriptome data revealed that HN44 had fewer differentially expressed genes (DEGs) under light drought stress, reacting insensitivity to water deficit. At the initial stage of drought stress, both varieties had a large number of upregulated DEGs to cope with the drought stress. Under severe drought stress, HN44 had fewer downregulated genes enriched in the photosynthesis pathway than SN14, while it had more upregulated genes enriched in the ABA-mediated signaling and glutathione metabolism pathways than SN14. During gradual water deficit, HN44 demonstrated better drought-tolerant physiological characteristics and water use efficiency than SN14 through key DEGs such as GmbZIP4, LOC100810474, and LOC100819313 in the major pathways. Key transcription factors were screened and identified, providing further clarity on the molecular regulatory pathways responsible for the physiological differences in drought tolerance among these varieties. This study deepened the understanding of the drought resistance mechanisms in soybeans, providing valuable references for drought-resistant soybean breeding.

Surface paving more important than species in determining the physiology, growth and cooling effects of urban trees

Urban trees provide numerous ecosystem services including the mitigation of urban heat. However, this cooling effect is often restricted due to poor tree growth and health caused by harsh growing conditions. The aim of this study is to analyse the influence of surface paving on the physiology, growth and cooling benefits of street trees of three common species with contrasting drought tolerance (Aesculus hippocastanum, Tilia × europaea and Quercus palustris) in Gothenburg, Sweden. Tree structural parameters, leaf water potentials, gas exchange, leaf area density and chlorophyll content were measured in three summertime periods in 2017 and 2018. Moreover, based on the measured data, the cooling effects of studied trees due to shading and transpiration were modelled.For all species, trees at highly paved sites were found to have significantly reduced growth, physiological performance and cooling effects compared to sites with a higher degree of permeable surfaces. This negative effect of surface paving was stronger than the effect of species, despite differences in drought tolerance and water use strategy between studied species. Based on the sensitivity of species to surface paving, we recommend Q. palustris and T. europaea for sites with good growing conditions due to their potential to maintain high water use and growth rates, and A. hippocastanum for highly paved sites where shading is not the primary ecosystem service sought. Our findings emphasise the importance of tree planting design in supporting urban tree growth and the continuous provision of ecosystem services, particularly in the context of the changing climate.

Functional phenotypic plasticity mediated by water stress and [CO2] explains differences in drought tolerance of two phylogenetically close conifers.

Forests are threatened globally by increased recurrence and intensity of hot droughts. Functionally close coexisting species may exhibit differences in drought vulnerability large enough to cause niche differentiation and affect forest dynamics. The effect of rising atmospheric [CO2], which could partly alleviate the negative effects of drought, may also differ between species. We analysed functional plasticity in seedlings of two taxonomically close pine species (Pinus pinaster Ait., Pinus pinea L.) under different [CO2] and water stress levels. The multidimensional functional trait variability was more influenced by water stress (preferentially xylem traits) and [CO2] (mostly leaf traits) than by differences between species. However, we observed differences between species in the strategies followed to coordinate their hydraulic and structural traits under stress. Leaf 13C discrimination decreased with water stress and increased under elevated [CO2]. Under water stress both species increased their sapwood area to leaf area ratios, tracheid density and xylem cavitation, whereas they reduced tracheid lumen area and xylem conductivity. Pinus pinea was more anisohydric than P. pinaster. Pinus pinaster produced larger conduits under well-watered conditions than P. pinea. Pinus pinea was more tolerant to water stress and more resistant to xylem cavitation under low water potentials. The higher xylem plasticity in P. pinea, particularly in tracheid lumen area, expressed a higher capacity of acclimation to water stress than P. pinaster. In contrast, P. pinaster coped with water stress comparatively more by increasing plasticity of leaf hydraulic traits. Despite the small differences observed in the functional response to water stress and drought tolerance between species, these interspecific differences agreed with ongoing substitution of P. pinaster by P. pinea in forests where both species co-occur. Increased [CO2] had little effect on the species-specific relative performance. Thus, a competitive advantage under moderate water stress of P. pinea compared with P. pinaster is expected to continue in the future.

MicroRNAs behave differently to drought stress in drought-tolerant and drought-sensitive grape genotypes

Drought is a major environmental factor limiting grapevine production and quality. However, the roles of miRNAs in different grape varieties at the post-transcriptional level during drought are largely unknown. In this study, we investigated the miRNA abundance in a drought-sensitive grapevine (Vitis vinifera L. cv. Cabernet Sauvignon) (CS) and a drought-tolerant grapevine (Berlandiari Ressiguier No.2 × Rupestris Martin) (110R) in response to drought using Illumina sequencing. A total of 488 known and 892 novel miRNAs belonging to 48 miRNA families were identified in CS and 110-R, respectively. Various accumulation trends of miRNAs observed in the differential drought tolerance of grapevine genotypes were further confirmed using stem-loop qRT-PCR. The target transcripts are predominantly associated with biological processes, cellular components, and molecular functions. Several significantly different drought-responsive miRNAs were examined by β-glucuronidase reporter gene activity driven by miRNA promoters in transgenic lines. The results showed drought-induced downregulation of VvmiR169d and VvmiR398a expression and upregulation of VvmiR156b expression. Moreover, we noted that VvmiR156b overexpression significantly decreased primary root length and increased lateral root numbers in Arabidopsis lines and observed a higher relative growth rate in grape calli under drought treatment. Therefore, genotype-dependent stress-responsive regulation of miRNA expression contributes to the differential drought tolerance of grapevines, and this finding provides mechanistic insight into the vital roles of miRNAs in drought-stress environments in grapevines.

Genetic variation for effects of drought stress on yield formation traits among commercial soybean [Glycine max (L.) Merr.] cultivars adapted to Ontario, Canada.

Drought stress significantly limits soybean [Glycine max (L.) Merr.] yields in Ontario, Canada. Many studies of genetic variation for drought tolerance compare commercial lines with exotic, unadapted germplasm. We hypothesized that even current commercial cultivars adapted to Ontario would differ significantly for traits related to drought tolerance. In a greenhouse experiment, we grew fifteen soybean cultivars in field soil amended with sand in 1-m rooting columns, which allowed for simulation of field-like soil water profiles and rooting depths. Two watering treatments were imposed from the first flower until maturity by daily restoration of soil water to either 100% (control), or 50% (drought stress) of the maximum soil water holding capacity. Throughout the experiment, we measured volumetric soil water content at different depths in the soil profile, but found no evidence at any developmental stage that the cultivars differed for their ability to extract soil water from different depths. Drought stress reduced seed yield by 51% on average. Similar to the effects of drought in the field, pod number was the yield component most affected, with effects on seeds per pod and single-seed weight being comparatively minor. There were significant cultivar × treatment interactions for seed yield, pod number, shoot dry matter, and water use. We identified two drought-sensitive (Saska and OAC Drayton) and three drought-tolerant (OAC Lakeview, OAC Champion, and PRO 2715R) cultivars based on their ratios of seed yield under drought stress to seed yield under control conditions (seed yield ratio, SYR). Regression and principal component analyses revealed that drought-tolerant (high-SYR) cultivars were consistently those that maintained relatively high values for water use, biomass accumulation and pod number under drought stress; high water use efficiency under drought stress was also associated with a high SYR. One of the cultivars, OAC Lakeview, displayed a distinct mode of drought tolerance, maintaining a very high fraction of its control pod number under drought stress. This study helps define the physiological basis of soybean cultivar differences in drought tolerance, and provides direction for soybean breeders to select traits that could improve yield under drought stress.

Key factors for differential drought tolerance in two contrasting wild materials of Artemisia wellbyi identified using comparative transcriptomics

BackgroundDrought is a significant condition that restricts vegetation growth on the Tibetan Plateau. Artemisia wellbyi is a unique semi-shrub-like herb in the family Compositae, which distributed in northern and northwest of Tibetan Plateau. It is a dominant species in the community that can well adapt to virous environment stress, such as drought and low temperature. Therefore, A. wellbyi. has a potential ecological value for soil and water conservation of drought areas. Understanding the molecular mechanisms of A. wellbyi. that defense drought stress can acquire the key genes for drought resistance breeding of A. wellbyi. and provide a theoretical basis for vegetation restoration of desertification area. However, they remain unclear. Thus, our study compared the transcriptomic characteristics of drought-tolerant “11” and drought-sensitive “6” material of A. wellbyi under drought stress.ResultsA total of 4875 upregulated and 4381 downregulated differentially expressed genes (DEGs) were induced by drought in the tolerant material; however, only 1931 upregulated and 4174 downregulated DEGs were induced by drought in the sensitive material. The photosynthesis and transcriptional regulation differed significantly with respect to the DEGs number and expression level. We found that CDPKs (calmodulin-like domain protein kinases), SOS3 (salt overly sensitive3), MAPKs (mitogen-activated protein kinase cascades), RLKs (receptor like kinase), and LRR-RLKs (repeat leucine-rich receptor kinase) were firstly involved in response to drought stress in drought tolerant A. wellbyi. Positive regulation of genes associated with the metabolism of ABA (abscisic acid), ET (ethylene), and IAA (indole acetic acid) could play a crucial role in the interaction with other transcriptional regulatory factors, such as MYBs (v-myb avian myeloblastosis viral oncogene homolog), AP2/EREBPs (APETALA2/ethylene-responsive element binding protein family), WRKYs, and bHLHs (basic helix-loop-helix family members) and receptor kinases, and regulate downstream genes for defense against drought stress. In addition, HSP70 (heat shock protein70) and MYB73 were considered as the hub genes because of their strong association with other DEGs.ConclusionsPositive transcriptional regulation and negative regulation of photosynthesis could be associated with better growth performance under drought stress in the drought-tolerant material. In addition, the degradation of sucrose and starch in the tolerant A. wellbyi to alleviate osmotic stress and balance excess ROS. These results highlight the candidate genes that are involved in enhancing the performance of drought-tolerant A. wellbyi and provide a theoretical basis for improving the performance of drought-resistant A. wellbyi.

Application of Morphological and Physiological Markers for Study of Drought Tolerance in Lilium Varieties

The shortage of water resources is an unfavourable factor that restricts the production of flowers. The use of drought-resistant morphological markers is of great significance to distinguish the drought resistance of flower varieties. In this paper, we study the difference in drought tolerance of seven common lily varieties in the flower market by morphological and physiological markers. The results showed that there were differences in leaf morphological indices and anatomical structures among the seven varieties. Drought reduced the chlorophyll content, inhibited the photosynthetic rate, and increased catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), malondialdehyde (MDA), proline, soluble sugar, and soluble protein. After rewatering, the activities of CAT, POD, and SOD of ‘Lyon’, ‘Royal Sunset’, and ‘Robina’ varieties decreased, which was opposite to the varieties of ‘Immaculate’, ‘Elena’, ‘Siberia’, and ‘Gelria’. According to the membership function value of physiological indices, the drought resistance of seven lily varieties from weak to strong was ‘Immaculate’, ‘Elena’, ‘Siberia’, ‘Gelria’, ‘Robina’, ‘Royal Sunset’, and ‘Lyon’. Drought resistance is related to the thickness of leaves, palisade tissue, sponge tissue, and specific leaf area. Lily leaf structure can be used as one of the indices to judge drought resistance.

Comparative transcriptomics reveals key genes contributing to the differences in drought tolerance among three cultivars of foxtail millet (Setaria italica)

Foxtail millet (Setaria italica L.) is an important food crop with strong drought stress tolerance. The response of foxtail millet to drought stress is a complex regulatory network. It is of great guiding significance for agricultural production to continuously explore candidate genes of foxtail millet drought resistance and reveal the molecular regulatory mechanism and metabolic pathway of foxtail millet drought tolerance. This study investigated three different cultivars of foxtail millet with different drought resistance. Drought stress reduced the water and chlorophyll content, and increased the Malondialdehyde (MDA) level and soluble protein of foxtail millet leaves. From strong to weak, the drought resistance order was Jigu39, Jingu21, and Longgu16. The transcriptome analysis of these three cultivars was carried out. 2954, 1531, and 2344 deferentially expressed genes under drought stress were identified in Jigu39, Jingu21, and Longgu16. The GO and KEGG pathway analysis identified DEGs significantly enriched in photosynthesis, chlorophyll metabolism, amino acid metabolism, and carbohydrate metabolism in all three cultivars. In addition, we identified 46 genes whose trends of transcription change were consistent with the drought resistance trends among three cultivars of foxtail millet. Among them, 32 genes were first identified related to drought response in foxtail millet, which was worth further research.

Drought tolerance differs between urban tree species but is not affected by the intensity of traffic pollution

Key MessageIn an urban area, resistance and resilience of stem diameter growth differ substantially between tree species. Traffic emissions are reflected in wood nitrogen isotopes, but do not affect drought tolerance.With increasing drought and heat, the benefits of urban trees such as shading and cooling become more important. Yet, it is necessary to identify tree species able to withstand such extreme climatic conditions. We studied the resistance and resilience of stem diameter growth of five deciduous tree species in an urban area in Southwest Germany to three exceptional drought periods (2003, 2011 and 2015) for differences between and within species, especially considering the intensity of traffic emissions (NOx). Analyses of the stable isotopic composition of carbon (δ13C) and oxygen (δ18O) as well as the intrinsic water-use efficiency (WUEi) in the tree rings were carried out. Further, we investigated the stable isotopic composition of nitrogen in the wood (δ15N) to assess its potential as an indicator of NOx emissions from traffic. Stem diameter growth in all species was strongly limited by low water availability in spring, as was also reflected in elevated δ13C and δ18O values in Acer platanoides and Tilia cordata, which were particularly sensitive to drought. In contrast, growth of Platanus × hispanica and Quercus robur was less affected by drought, and resistance of Carpinus betulus ranged in between. Across species, δ15N was higher in trees located closer to roads and exposed to higher NOx traffic emissions. Unexpectedly, these conditions did not significantly affect drought resistance/resilience. Our study demonstrates the potential and interpretative challenges of coupled dendroecological and isotope analyses. It also indicates clear species-specific differences in drought tolerance and thus helps to identify suitable urban tree species.

Population-level drought responses in northern oak fern (Gymnocarpium dryopteris)

Ferns serve as an invaluable indicator species for soil moisture and distribution patterns of other plant groups. Northern oak fern ( Gymnocarpium dryopteris), a common fern in the interior of British Columbia, Canada, has received little research attention despite its prevalent use in the forest resource sector as an indicator species for moisture. To understand the impact of water deficits on oak fern, we sampled in two different ecoregions in interior British Columbia and assessed acclimation to drought, by measuring the size and abundance of stomata in each region. We then subjected the ferns to a period of drought and recorded the response to stress by measuring the photosynthetic efficiency of the oak fern populations over time. Differences existed in the morphology of oak fern populations; ferns from the wetter ecoregion possessed more, larger stomata than those from the drier ecoregion. Oak ferns from both regional populations were significantly reliant on moisture present in the soil and air to maintain photosynthetic efficiency, and <20% of the population remained healthy after the 18-day drought period. The stress response of both oak fern populations followed a similar pattern; differences in stomate size and abundance did not result in differences in drought tolerance.

Tomato Defense against Whiteflies under Drought Stress: Non-Additive Effects and Cultivar-Specific Responses.

Two of the main causes of losses in tomato production are the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), and drought, which is becoming a central problem in agriculture due to global climate change. The separate effects of whitefly infestation and drought have been amply studied in many crop systems. However, less is known about their combined effects. To evaluate whether drought stress (DS) affects plant defense against whiteflies, we assessed the joint effects of whitefly infestation and DS on plant vegetative and reproductive performance in four tomato cultivars, and assessed the effects of DS on plant resistance and tolerance (compensatory ability) to whiteflies in a greenhouse experiment. Generally, we found negative effects of DS and whiteflies on plant performance, but the combined effects of DS and herbivory were not worse than those of either stress alone. In fact, plant performance under the combined effect of both stresses was usually similar to that in the presence of whiteflies without DS. Plants growing under DS had greater trichome density. However, plant resistance—as measured by whitefly population growth—decreased under DS in two cultivars and was unaffected in the other two. Compensatory ability decreased under DS in all but one cultivar. These cultivar-specific responses suggest genetic variation in resistance and tolerance to whiteflies and could be associated with differences in drought tolerance among cultivars. Our findings underscore the difficulty in predicting the combined effects of DS and herbivory and point to the need for a better understanding of the mechanisms underlying plant responses to both stresses at the molecular, cellular, and organismal levels.

Differential drought tolerance responses in short-grain aromatic rice germplasms from Koraput valley of Eastern Ghats of India

Differential drought tolerance responses in short-grain aromatic rice germplasms from Koraput valley of Eastern Ghats of India

Proteomic analysis reveals different responses to drought between the Cleome spinosa (C3) and Cleome gynandra (C4)

The global emergence of low water availability causes extensive damage to crops in many regions. Although the responses of plants to drought stress have been extensively investigated, molecular studies on plants with different carboxylation pathways are limited. Therefore, we aimed to identify quantitative differences in proteins functioning in differential drought tolerance of C3 (Cleome spinosa) and C4 (C. gynandra) species. Proteomic analysis functionally characterized 33 differentially accumulated proteins in C. spinosa and 15 proteins in C. gynandra leaves. The identified proteins were involved in multiple aspects of leaf metabolism such as photosynthesis, energy metabolism, protein metabolism, and stress defense. The up-regulated accumulation of RuBisCO proteins may have contributed to carboxylation in stressed C. spinosa, but RuBisCO activase proteins were severely down-regulated. Additionally, down-regulation of ferredoxin-nicotinamide adenine dinucleotide phosphate (NADP) reductase and oxygen-evolving enhancer proteins was only found in C. spinosa, which possibly related to the inhibition of electron flow. The up-regulation of enolase may contribute to the energy requirement in C. gynandra, while down-regulation of glycolytic enzymes, such as fructose-bisphosphate aldolase and triosephosphate isomerase, was found in C. spinosa suggesting the impaired energy metabolism under drought stress. The proteomic analysis suggests different adaptive strategies between C. spinosa and C. gynandra against drought stress.

Differences of drought tolerance of the main tree species in Dongling Mountain, Beijing, China as indicated by tree rings

Forests in Beijing exhibit vulnerability to increasing stress of extreme drought in recent years. To investigate the drought tolerance of different tree species, we chose three tree species (Larix principis-rupprechtii, Pinus tabuliformis, and Quercus wutaishanica) from the forest of Dongling Mountain in Beijing and used dendroecological method to analyze the relationship between radial growth and climate, as well as their resistance and resilience to extreme drought events. Our results showed that the radial growth of L. principis-rupprechtii and P. tabuliformis was significantly negatively correlated with monthly mean temperature from May to June, but that of Q. wutaishanica was significantly negatively correlated with monthly mean temperature only in May. The radial growth of L. principis-rupprechtii was significantly positively correlated with monthly mean precipitation in June, monthly mean relative humidity from May to June and August to September. The radial growth of P. tabuliformis was significantly positively correlated with monthly mean precipitation and monthly mean relative humidity from June to August. The radial growth of Q. wutaishanica was significantly positively correlated with monthly mean precipitation in February and May, and monthly mean relative humidity in May. The radial growth of all the three species was significantly positively correlated with monthly mean SPEI (standardized precipitation evapotranspiration index) from May to July. L. principis-rupprechtii was least drought tolerant, as indicated by the greatest growth reduction (46.6%-69.6%), lowest resistance (0.534, 0.304, 0.530) and resilience (0.686, 0.570, 0.753) during the three extreme drought events occurred in the 1994, 2001-2002, and 2007. In contrast, tree growth of Q. wutaishanica showed the highest drought resistance in 2007, whereas no significant differences were observed between other two species. Extreme drought events caused by continuous high temperature and reduced precipitation during the growing season accounted for the reduction in tree radial growth. The various physiological and ecological strategies of tree species were the possible reasons for the difference in drought tolerance. Our results could provide a basis for the selection of suitable afforestation tree species and the formulation of forest protection mea-sures to maintain forest ecosystem functions and services under the background of undergoing climate change.

Widely targeted metabolomics reveals the different metabolic changes in leaves and roots of two cotton varieties under drought stress

AbstractCotton yield is affected by drought stress. We performed widely targeted metabolomics to explore metabolic changes under drought stress in the roots and leaves of two cotton varieties differing in drought tolerance—XLZ8 as sensitive and G95079 as tolerant variety. A total of 537 metabolites were detected at different stages of drought stress. Abscisic acid (ABA) was significantly enriched in all stages of drought stress in both roots and leaves of XLZ8. Amino acids showed enrichment in leaves of G95079 in the early stage of drought stress. Flavonoids were significantly enriched in the leaves of the two varieties in the late stage of drought stress. In roots, nucleotides and their derivatives were highly enriched in XLZ8 in the late stage of drought stress. The biosynthetic pathways of kynurenine and polyamine and glycerophospholipid metabolism may play an important role in cotton drought tolerance by scavenging reactive oxygen species (ROS) and reconstructing cell membranes. Spraying appropriate concentrations of proline, kynurenine, S‐adenosylmethionine, glucose and 1‐oleoyl‐2‐hydroxy‐sn‐glycero‐3‐phosphocholine (lyso PC18:1) significantly increased the survival rate of cotton seedlings under drought stress. We speculated that ABA‐dependent and ABA‐independent metabolic changes may lead to differences in drought tolerance among cotton varieties.

Antioxidant responses are associated with differences in drought tolerance between maize and sorghum.

Drought is a major cause of decreased yield in crops worldwide. Sorghum (Sorghum bicolor) and maize (Zea mays) are two of the key crops in Africa serving as human food as well as livestock feed. For improved crop production, selection for drought resilient genotypes is imperative and the biological basis for drought tolerance ought to be fully understood to achieve such selection. Sorghum can tolerate drought better than maize and it is a key model for studying the physiological and biochemical mechanisms conferring drought tolerance. In this study, comparative analyses in terms of changes in growth, chlorophyll content, ROS content, lipid peroxidation level and the activity of antioxidant enzymes were investigated. Exposure to drought triggered ROS generation in both plant species. However, sorghum showed less cell damage under water deficit compared to maize. Furthermore, differences in antioxidant enzyme activity between maize and sorghum were identified. Our findings reveal differences in and association between the physiological and biochemical responses of maize and sorghum to drought, which may be relevant for breeding drought tolerant crops.

Multivariate Analysis of Morpho-Physiological Traits Reveals Differential Drought Tolerance Potential of Bread Wheat Genotypes at the Seedling Stage.

Drought is one of the foremost environmental stresses that can severely limit crop growth and productivity by disrupting various physiological processes. In this study, the drought tolerance potential of 127 diverse bread wheat genotypes was evaluated by imposing polyethylene glycol (PEG)-induced drought followed by multivariate analysis of several growth-related attributes. Results showed significant variations in the mean values of different morpho-physiological traits due to PEG-induced drought effects. Correlation analysis revealed that most of the studied traits were significantly correlated among them. The robust hierarchical co-clustering indicated that all the genotypes were clustered into four major groups, with cluster 4 (26 genotypes) being, in general, drought-tolerant followed by cluster 1 (19 genotypes) whereas, cluster 2 (55 genotypes) and 3 (27 genotypes) being drought-sensitive. Linear discriminant analysis (LDA) confirmed that around 90% of the genotypes were correctly assigned to clusters. Squared distance (D2) analysis indicated that the clusters differed significantly from each other. Principal component analysis (PCA) and genotype by trait biplot analysis showed that the first three components accounted for 71.6% of the total variation, with principal component (PC) 1 accounting for 35.4%, PC2 for 24.6% and PC3 for 11.6% of the total variation. Both PCA and LDA revealed that dry weights, tissue water content, cell membrane stability, leaf relative water content, root-shoot weight ratio and seedling vigor index played the most important discriminatory roles in explaining drought tolerance variations among 127 wheat genotypes. Our results conclude that the drought-tolerant and -sensitive wheat genotypes identified in this study would offer valuable genetic tools for further improvement of wheat productivity in arid and semi-arid regions during this time of unpredictable climate change.