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Plants often encounter unfavorable environmental conditions because of their sessile lifestyle. These adverse factors greatly affect the geographic distribution of plants, as well as their growth and productivity. Drought stress is one of the premier limitations to global agricultural production due to the complexity of the water-limiting environment and changing climate. Plants have evolved a series of mechanisms at the morphological, physiological, biochemical, cellular, and molecular levels to overcome water deficit or drought stress conditions. The drought resistance of plants can be divided into four basic types-drought avoidance, drought tolerance, drought escape, and drought recovery. Various drought-related traits, including root traits, leaf traits, osmotic adjustment capabilities, water potential, ABA content, and stability of the cell membrane, have been used as indicators to evaluate the drought resistance of plants. In the last decade, scientists have investigated the genetic and molecular mechanisms of drought resistance to enhance the drought resistance of various crops, and significant progress has been made with regard to drought avoidance and drought tolerance. With increasing knowledge to comprehensively decipher the complicated mechanisms of drought resistance in model plants, it still remains an enormous challenge to develop water-saving and drought-resistant crops to cope with the water shortage and increasing demand for food production in the future.

Under climate change, extreme droughts will limit water availability for plants. However, the species-specific responses make it difficult to draw general conclusions. We hypothesized that changes in species’ abundance in response to extreme drought can be best explained by a set of water economic traits under ambient conditions in combination with the ability to adjust these traits towards higher drought resistance. We conducted a 4-year field experiment in temperate grasslands using rainout shelters with 30% and 50% rainfall reduction. We quantified the response as the change in species abundance between ambient conditions and the rainfall reduction. Abundance response to extreme drought was best explained by a combination of traits in ambient conditions and their functional adjustment, most likely reflecting plasticity. Smaller leaved species decreased less in abundance under drought. With increasing drought intensity, we observed a shift from drought tolerance, i.e., an increase in leaf dry matter content, to avoidance, i.e., a less negative turgor loss point (TLP) in ambient conditions and a constancy in TLP under drought. We stress the importance of using a multidimensional approach of variation in multiple traits and the importance of considering a range of drought intensities to improve predictions of species’ response to climate change.

• Hydraulic segmentation at the stem–leaf transition predicts higher hydraulic resistance in leaves than in stems. Vulnerability segmentation, however, predicts lower embolism resistance in leaves. Both mechanisms should theoretically favour runaway embolism in leaves to preserve expensive organs such as stems, and should be tested for any potential coordination. • We investigated the theoretical leaf-specific conductivity based on an anatomical approach to quantify the degree of hydraulic segmentation across 21 tropical rainforest tree species. Xylem resistance to embolism in stems (flow-centrifugation technique) and leaves (optical visualization method) was quantified to assess vulnerability segmentation. • We found a pervasive hydraulic segmentation across species, but with a strong variability in the degree of segmentation. Despite a clear continuum in the degree of vulnerability segmentation, eight species showed a positive vulnerability segmentation (leaves less resistant to embolism than stems), whereas the remaining species studied exhibited a negative or no vulnerability segmentation. • The degree of vulnerability segmentation was positively related to the degree of hydraulic segmentation, such that segmented species promote both mechanisms to hydraulically decouple leaf xylem from stem xylem. To what extent hydraulic and vulnerability segmentation determine drought resistance requires further integration of the leaf–stem transition at the whole-plant level, including both xylem and outer xylem tissue.

The increasing frequency of droughts worldwide, along with their substantial societal impacts, underscore the need for improved drought early warning and enhanced water supply security. While reservoir drought management strategies, including hedging theory and drought warning/limited water level (DWWL), have been extensively studied for their potential to alleviate water supply stress, effective control schemes remain lacking. This study proposes a framework to enhance reservoir drought resistance. The framework starts with the analytical derivation of the optimal hedging rule (HR) for reservoirs supplying multiple competing users, applicable to both real‐time and long‐term optimizations. DWWLs and their seasonal segmentation are then determined based on the optimal water supply process and multivariate time‐series clustering. By utilizing reservoir water level and meteorological drought indicator to monitor drought conditions and characterize reservoir effective storage, a real‐time operational strategy is ultimately proposed that integrates analytical HR with effective storage. We demonstrate the application in the Danjiangkou Reservoir in China, and the proposed operation is testified under both long‐term periods and extreme dry conditions. Results indicate that the analytical HR outperforms conventional rule curves in nearly every aspect, including water supply benefits, reliability, and refill rate. The DWWL proves crucial during extreme drought conditions; when water levels fall below DWWL, the HR considering DWWL restricts water supply earlier, thereby preventing the reservoir from dropping dramatically to critically low levels. This proposed framework is transferable to other water supply reservoirs, offering scientific support, operational relevance, and guidance for drought mitigation and response.

Although the antioxidant role of melatonin in stress mitigation is well established, its multifunctionality may support plant tolerance to drought through additional mechanisms. This study aimed to evaluate melatonin’s contribution to both antioxidant defence and methylglyoxal (MG) detoxification—a harmful compound that disrupts cellular balance under drought stress. The glyoxalase pathway, which is aided by glutathione, plays a pivotal role in MG detoxification. Therefore, we examined the impact of both endogenous and exogenous melatonin on this system. Two pepper genotypes differing in drought tolerance and endogenous melatonin levels were exposed to 12 days of drought following a 5 µM melatonin treatment. The drought-tolerant genotype, characterized by higher levels of endogenous melatonin, exhibited more efficient MG detoxification through increased glutathione and glyoxalase activities, reduced membrane damage and enhanced antioxidant capacity. Exogenous melatonin further mitigated the effects of drought by reducing MG accumulation and stimulating antioxidant and glyoxalase enzymes. Overall, both endogenous and applied melatonin enhances drought tolerance in pepper by activating antioxidant defences and the glyoxalase pathway.

Drought is one of the main abiotic stresses that seriously influences cotton production. Many indicators can be used to evaluate cotton drought tolerance, but the key indicators remain to be determined. The objective of this study was to identify effective cotton drought tolerance indicators from 19 indices, including morphology, photosynthesis, physiology, and yield-related indices, and to evaluate the yield potential of 104 cotton varieties under both normal and drought-stress field conditions. Combined with principal component analysis (PCA) and a regression analysis method, the results showed that the top five PCs among the 19, with eigenvalues > 1, contributed 65.52, 63.59, and 65.90% of the total variability during 2016 to 2018, respectively, which included plant height (PH), effective fruit branch number (EFBN), single boll weight (SBW), transpiration rate (Tr) and chlorophyll (Chl). Therefore, the indicator dimension decreased from 19 to 5. A comparison of the 19 indicators with the 5 identified indicators through PCA and a combined regression analysis found that the results of the final cluster of drought tolerance on 104 cotton varieties were basically consistent. The results indicated that these five traits could be used in combination to screen cotton varieties or lines for drought tolerance in cotton breeding programs, and Zhong R2016 and Xin lu zao 45 exhibited high drought tolerance and can be selected as superior parents for good yield performance under drought stress.

Summary Upland rice is a distinctive drought‐aerobic ecotype of cultivated rice highly resistant to drought stress. However, the genetic and genomic basis for the drought‐aerobic adaptation of upland rice remains largely unclear due to the lack of genomic resources. In this study, we identified 25 typical upland rice accessions and assembled a high‐quality genome of one of the typical upland rice varieties, IRAT109, comprising 384 Mb with a contig N50 of 19.6 Mb. Phylogenetic analysis revealed upland and lowland rice have distinct ecotype differentiation within the japonica subgroup. Comparative genomic analyses revealed that adaptive differentiation of lowland and upland rice is likely attributable to the natural variation of many genes in promoter regions, formation of specific genes in upland rice, and expansion of gene families. We revealed differentiated gene expression patterns in the leaves and roots of the two ecotypes and found that lignin synthesis mediated by the phenylpropane pathway plays an important role in the adaptive differentiation of upland and lowland rice. We identified 28 selective sweeps that occurred during domestication and validated that the qRT9 gene in selective regions can positively regulate drought resistance in rice. Eighty key genes closely associated with drought resistance were appraised for their appreciable potential in drought resistance breeding. Our study enhances the understanding of the adaptation of upland rice and provides a genome navigation map of drought resistance breeding, which will facilitate the breeding of drought‐resistant rice and the “blue revolution” in agriculture.

The resource and environmental challenges faced by rice production call for resource-saving and environment-friendly rice varieties. Water-saving and drought-resistance rice (WDR) is a new type of cultivated rice combining both high yield potential and acceptable grain quality as a current lowland paddy rice, as well as water-saving and drought resistance as a traditional upland rice. The lowland and upland rice are two ecotypes adapted to contrasting soil water status, originating mainly because of their differentiated drought resistance. Upland rice, domesticated in a water–limited environment and experiencing a bidirectional selection process, has better drought resistance and especially better drought avoidance. Though the potential tradeoff between drought resistance and productivity is very common in rice, the bidirectional selection could overcome this tradeoff and accumulate recombination genotypes. It is very important to choose elite parents on the basis of studies on the great genetic diversity of rice yield and drought resistance among the rice germplasm resources and adapt the bidirectional selection strategies to especially integrate drought avoidance, drought tolerance, high water use efficiency, and productivity in WDR breeding. The breeding history and genomic studies indicated that lowland paddy rice and upland rice hybridization breeding with suitable selection in different environments is an effective approach to improving complex traits such as yield potential and drought resistance. Meanwhile, molecular technology shows higher efficiency on value-added breeding such as transferring and pyramiding pest- and disease-resistant genes, which helps WDR obtain other green characters. Twenty-two WDR varieties were registered and distributed to farmers in recent years and could be planted in both irrigated and rainfed ecosystems, thus showing promising application prospects. The major crop management technology of WDR in lowland paddy fields with water-saving cultivation and in rainfed fields by dry seeding with aerobic cultivation were also discussed in this article.

Background Deep rooting is an important factor affecting rice drought resistance. However, few genes have been identified to control this trait in rice. Previously, we identified several candidate genes by QTL mapping of the ratio of deep rooting and gene expression analysis in rice. Results In the present work, we cloned one of these candidate genes, OsSAUR11 , which encodes a small auxin-up RNA (SAUR) protein. Overexpression of OsSAUR11 significantly enhanced the ratio of deep rooting of transgenic rice, but knockout of this gene did not significantly affect deep rooting. The expression of OsSAUR11 in rice root was induced by auxin and drought, and OsSAUR11-GFP was localized both in the plasma membrane and cell nucleus. Through an electrophoretic mobility shift assay and gene expression analysis in transgenic rice, we found that the transcription factor OsbZIP62 can bind to the promoter of OsSAUR11 and promote its expression. A luciferase complementary test showed that OsSAUR11 interacts with the protein phosphatase OsPP36. Additionally, expression of several auxin synthesis and transport genes (e.g., OsYUC5 and OsPIN2 ) were down-regulated in OsSAUR11 -overexpressing rice plants. Conclusions This study revealed a novel gene OsSAUR11 positively regulates deep rooting in rice, which provides an empirical basis for future improvement of rice root architecture and drought resistance.

Pennyroyal ( Mentha pulegium L.) is a valuable medicinal plant, renowned for its diverse biological and therapeutic effects, which are largely attributed to its wide range of secondary metabolites, such as terpenoids and phenolic compounds. Currently, water deficit, as a major growth-limiting factor for many medicinal plants, poses one of the most significant challenges in plant production. A factorial experiment, based on a completely randomized design (CRD) with three replications, was conducted to assess the effects of foliar application of 5-aminolevulinic acid (ALA) on the growth, physiological attributes, and biochemical responses of M. pulegium under a gradient of drought stress intensities. The experimental treatments comprised four levels of drought stress (100%, 75%, 50%, and 25% of field capacity) and four concentrations of 5-aminolevulinic acid (ALA) (0, 5, 10, and 15 µM). The accumulation of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), proline, glycine betaine, and total phenols, as well as the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) enzymes, were elevated in response to increasing drought intensity. A decline in relative water content, photosynthetic pigment levels, stomatal conductance, Rubisco enzyme activity, and photosynthetic rate with increasing stress levels resulted in reduced plant growth. Foliar application of ALA significantly mitigated the accumulation of hydrogen peroxide and lipid peroxidation (as measured by malondialdehyde content) in pennyroyal plants. This protective effect was mediated by an enhancement in the accumulation of antioxidant compounds, including total phenols and essential oils, coupled with increased activity of antioxidant enzymes such as catalase, peroxidase, and superoxide dismutase. Furthermore, ALA application, particularly at a concentration of 10 µM, alleviated the detrimental effects of water deficit on photosynthesis by enhancing photosynthetic pigment content, stomatal conductance, and Rubisco enzyme activity. The enhanced drought tolerance observed in pennyroyal following ALA application is primarily attributed to a significant boost in the plant’s antioxidant capacity. This enhanced capacity effectively protects the photosynthetic apparatus from oxidative damage. Consequently, the resultant improvement in photosynthetic efficiency supports better growth performance under drought stress conditions.