Severe Drought Stress Research Articles

Lipo-chitooligosaccharide and thuricin 17 act as plant growth promoters and alleviate drought stress in Arabidopsis thaliana.

Lipo-chito-oligosaccharide (LCO-from Bradyrhizobium japonicum) and thuricin 17 (Th17-from Bacillus thuringiensis) are bacterial signal compounds from the rhizosphere of soybean that have been shown to enhance plant growth in a range of legumes and non-legumes. In this study, an attempt to quantify phytohormones involved in the initial hours after exposure of Arabidopsis thaliana to these compounds was conducted using UPLC-ESI-MS/MS. A petri-plate assay was conducted to screen for drought stress tolerance to PEG 8000 infusion and plant growth was studied 21-days post-stress. Arabidopsis thaliana plants grown in trays with drought stress imposed by water withhold were used for free proline determination, elemental analysis, and untargeted proteomics using LC-MS/MS studies. At 24 h post-exposure to the signal compounds under optimal growth conditions, Arabidopsis thaliana rosettes varied in their responses to the two signals. While LCO-treated rosettes showed a decrease in total IAA, cytokinins, gibberellins, and jasmonic acid, increases in ABA and SA was very clear. Th17-treated rosettes, on the other hand, showed an increase in IAA and SA. Both treatments resulted in decreased JA levels. Under severe drought stress imposed by PEG 8000 infusion, LCO and Th17 treatments were found to significantly increase fresh and dry weight over drought-stressed control plates, indicating that the presence of the signaling compounds decreased the negative effects experienced by the plants. Free proline content increased in LCO- and Th17-treated plants after water-withhold drought stress. Elemental analysis showed a significant increase in carbon percentage at the lower concentration of Th17. Untargeted proteomics revealed changes in the levels of drought-specific ribosomal proteins, glutathione S-transferase, late embryogenesis proteins, vegetative storage proteins 1 and 2, thaumatin-like proteins, and those related to chloroplast and carbon metabolism. The roles of some of these significantly affected proteins detected under drought stress are discussed.

Drought affects both photosystems in Arabidopsis thaliana.

Drought is a major abiotic stress that impairs plant growth and development. Despite this, a comprehensive understanding of drought effects on the photosynthetic apparatus is lacking. In this work, we studied the consequences of 14-d drought treatment on Arabidopsis thaliana. We used biochemical and spectroscopic methods to examine photosynthetic membrane composition and functionality. Drought led to the disassembly of PSII supercomplexes and the degradation of PSII core. The light-harvesting complexes (LHCII) instead remain in the membrane but cannot act as an antenna for active PSII, thus representing a potential source of photodamage. This effect can also be observed during nonphotochemical quenching (NPQ) induction when even short pulses of saturating light can lead to photoinhibition. At a later stage, under severe drought stress, the PSI antenna size is also reduced and the PSI-LHCI supercomplexes disassemble. Surprisingly, although we did not observe changes in the PSI core protein content, the functionality of PSI is severely affected, suggesting the accumulation of nonfunctional PSI complexes. We conclude that drought affects both photosystems, although at a different stage, and that the operative quantum efficiency of PSII (ΦPSII ) is very sensitive to drought and can thus be used as a parameter for early detection of drought stress.

Cobalt enhanced the drought-stress tolerance of rice (Oryza sativa L.) by mitigating the oxidative damage and enhancing yield attributes

Water scarcity is one of the most important abiotic factors limiting rice growth and productivity. The application of nutrients affects various physiological and biochemical mechanisms to curtail water deficiency, but little is known about the ameliorative effects of cobalt (Co) on rice. Our study aimed to investigate the advantageous effects of soaking in Co at the optimum concentration (10 and 44.5 µM) on morpho-physiological traits and oxidative stress, during the vegetative and reproductive stages, also assessing yield attributes, in two rice varieties (Sakha 104, drought-sensitive, and Giza 178, drought-tolerant). Treatments included control (100% field capacity (FC)), moderate drought stress (75 % FC), and severe drought stress (50 % FC) either alone or in combination with Co. A water deficit and oxidative stress affected Giza 178 less than Sakha 104. Co application significantly enhanced the performance of two rice varieties under drought stress by increasing plant height, biomass, water content, tillering, leaf area, pigments (chlorophyll a, carotenoids, total chlorophyll), sugars (soluble sugars, and total carbohydrates), and Co content (shoot and root). Also, Co significantly increased the performance of the antioxidant system by elevating the concentration of total phenols, flavonoids, proline, and antioxidant enzymes (catalase, peroxidase, and polyphenol oxidase), while significantly decreasing chlorophyll b, malondialdehyde, and 2,2-diphenyl-1-picryl-hydrazyl. Yield attributes such as the number of tillers, panicle parameters (number, length, and weight), 100-grain weight, harvest index, and grain nutritive value (sugars, vitamin B, and Co contents) were significantly enhanced by Co in both varieties. However, the maximum performance was observed in Giza 178.

Drought stress-responsive abscisic acid and salicylic acid crosstalk with the phenylpropanoid pathway in soybean seeds.

Crosstalk between hormones and secondary metabolites regulates the interactions between plants and stress. However, little is known about the effects of hormone crosstalk on the concentration of flavonoids in seeds. In this study, we identified abscisic acid (ABA) as a negative regulator of flavonoid accumulation in soybean seeds under drought-stress conditions. Alterations in flavonoid accumulation at several intensities of water stress, followed by a recovery period, were measured during the soybean seed-filling stage. Low soil moisture (SM 10%) significantly decreased the total flavonoid content in seeds. The decline in flavonoid content was proportional to the severity of drought stress and was dependent on the activities of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS), two key phenylpropanoid pathway enzymes. The expression of phenylalanine ammonia-lyase 1 (GmPAL1), chalcone isomerase 1A (GmCHI1A), and chalcone synthase 8 (GmCHS8) was associated with phenolic and flavonoid accumulation in soybean seeds of plants subjected to drought stress. Interestingly, the expression levels of GmCHS8 were highly correlated with flavonoid levels under drought stress and water recovery conditions. Cinnamic acid, which is a biosynthesis precursor shared by both phenylpropanoid metabolism and salicylic acid (SA) biosynthesis, decreased under drought stress conditions. Notably, exogenous ABA suppressed the expression of GmPAL1, which encodes the first rate-limiting enzyme in the phenylpropanoid biosynthesis pathway and affects downstream products such as SA and flavonoids. In conclusion, drought stress altered the phenylpropanoid-derived compounds, at least with regard to flavonoid and SA accumulation in seeds, which was regulated by antagonistic interactions with ABA.

Rapid beech decline under recurrent drought stress: Individual neighborhood structure and soil properties matter

During the summer of 2022, an acute drought once more afflicted central and southern Europe. This marked the third episode (after 2015 and 2018) of severe aridity in large parts of Germany within the last decade, leading to increased soil water depletion. Consequently, from July 2022 onward, European beech trees (Fagus sylvatica L.) exhibited early withering and pronounced premature defoliation. Nevertheless, crown defoliation exhibited substantial variation among trees within the same forest stands, prompting questions regarding the causal factors. In our study, we scrutinized twelve mature drought-impacted, beech-dominated forest stands in northern Bavaria, arranged along a gradient of different nutrient regime levels (base-rich, intermediate, base-poor), with co-occurring vital (≤40% crown defoliation) and declining (≥60% crown defoliation) trees. Within each stand, we selected an equal number of vital and declining trees, culminating in a total of 332 target trees. Dendrochronological patterns were analyzed to identify a potential timing of growth separation between vitality classes. Moreover, we used a Bayesian modelling framework to discern whether disparities in tree vitality hinged on competition, structure, small-scale differences in plant-available water capacity, and spatial clustering of declining competitors. We further explored the factors influencing the magnitude of growth decline post-2018 and how these were modulated by the site's nutrient regime. Our study unveiled that (i) low competition with increased size diversity bolstered tree vitality; (ii) declining trees were spatially aggregated; (iii) vital and declining trees exhibited strikingly similar growth trajectories in the past, which underwent a drastic shift following 2018, indicating a potential for a rapid vitality decline under recurrent severe drought stress; (iv) plant-available water capacity emerged as a crucial determinant of vitality and growth subsequent to 2018; (v) growth decline was most pronounced at base-poor and intermediate sites. Our findings underscore the importance of accommodating small-scale differences in soil and stand characteristics and advocate for silvicultural guidance towards reduced stand densities in combination with a more heterogenous structure to mitigate beech dieback in drought-prone forest stands.

Multi-year nitrogen accumulation weakens the stabilizing effect of species asynchrony on drought resistance in a Tibetan alpine meadow

Although the impacts of exogenic nitrogen (N) enrichment and drought on grassland community productivity are well known, their interactive effects on community stability remain insufficiently understood. In this study, a seven-year N enrichment experiment was conducted in a Tibetan alpine meadow to examine the effects of N-altered species richness, species dominance, species asynchrony, and pre-drought biomass on community stability, resistance, and resilience during two natural drought stresses (the first severe drought stress in 2015, FDS, and the second light drought stress in 2019, SDS). Our results indicate that N enrichment did not alter species richness but significantly reduced species asynchrony and dominance. Community stability showed a significant correlation with species asynchrony and dominance while remaining independent of species richness. Drought resistance, which was positively associated with community stability, was primarily influenced by species asynchrony and pre-drought biomass, rather than species dominance. Remarkably, the slopes of resistance in relation to the aforementioned factors were steeper in SDS than in FDS, despite SDS being lighter than FDS, indicating a more sensitive response to drought resistance to long-term N accumulation. In contrast, resilience was unaffected by species richness but increased with the rate of N addition. During the FDS, drought resistance and community stability were primarily governed by species asynchrony, while during the SDS, pre-drought biomass overwhelmingly determined drought resistance, surpassing the role of species asynchrony. These findings demonstrate the opposite effects of multi-year N accumulation on species asynchrony and pre-drought biomass, both of which reduce drought resistance and community stability over time. Therefore, our results contribute to a deeper understanding of grassland community stability in the face of N enrichment and natural drought stresses, aiding in predictions of grassland responses to ongoing global environmental changes.

Effect of soil drought stress on leaf water status and photosynthetic apparatus in argan seedlings (Argania spinosa)

Argan tree growth and production are both affected by drought stress, which is recognized as a critical and serious environmental issue worldwide. This study aims to examine the effect of a multi-species consortium of arbuscular mycorrhizal fungi (AMF) “Rhizargan consortium”, on the leaf water status and photosynthesis in drought-stressed argan seedlings. The performances of Rhizargan consortium were compared to those of a single pure commercialized strain of Rhizophagus irregularis. Seedlings of two argan tree ecotypes were subjected to three water regimes: 30, 60, and 100% field capacity (FC). After twelve months of drought stress, mycorrhizal argan seedlings showed a significant increase in leaf water potential, stomatal conductance, and maximum efficiency of PSII (Fm/Fv) than those without mycorrhiza inoculation. Moreover, AMF inoculation led to significant leaf accumulation of chlorophyll and carotenoid upon drought imposition. Nonetheless, severe drought stress (30% FC) decreased these physiological/photochemical attributes as well as both frequency and intensity of mycorrhization, but to a lesser extent in the argan seedlings inoculated with “Rhizargan consortium”. This study contributes to advances in the knowledge of the indigenous Rhizargan consortium’s ability to induce drought tolerance in argan trees.

Type and duration of water stress influence host selection and colonization by exotic ambrosia beetles (Coleoptera: Curculionidae).

Fungus-farming ambrosia beetles in the tribe Xyleborini tunnel into plants and trees to establish chambers for cultivating their nutritional fungal mutualists and rearing offspring. Some xyleborine ambrosia beetles preferentially infest and perform better in living but weakened trees. Flood stress predisposes horticultural tree crops to infestation, but the impact of drought stress has not been well studied. Our objectives were to compare the effects of flood stress vs. drought stress on host selection and colonization by xyleborine ambrosia beetles and to assess the duration of flooding. Container-grown Cornus florida L. trees were flood stressed using a pot-in-pot system to submerge the roots in water while drought-stressed conditions were imposed by withholding irrigation and precipitation. When experimental trees were held under field conditions for 14 days, 7.5× more ambrosia beetles landed on stems of the flood-stressed than on the drought-stressed trees. During two additional experiments over 14 and 22 days, ambrosia beetles tunneled into the flood-stressed trees but not the drought-stressed or standard irrigation trees. By simultaneously deploying trees that were flood stressed for varying lengths of time, it was found that more tunnel entrances, and xyleborine adults and offspring were recovered from trees that were flooded for 1-16 days and 7-22 days than from trees that were flooded for 14-29 days and 28-43 days. These results indicate that acute and severe drought stress does not predispose C. florida to infestation, but flood stress and the duration of flooding influence ambrosia beetle host selection and colonization. Understanding the role of host quality on ambrosia beetle preference behavior will assist with predicting the risk of infestation of these opportunistic insects in horticultural tree crops.

Application of the OECT-Based In Vivo Biosensor Bioristor in Fruit Tree Monitoring to Improve Agricultural Sustainability

Water scarcity is a major concern in agriculture worldwide. Fruit trees are severely affected by water deprivation in terms of growth, fruit yield, and quality. Plant monitoring combined with efficient irrigation is pivotal to achieve good quality standards and improve agricultural sustainability. This study reports the use of in vivo sensing technology to monitor fruit tree species continuously, in real time and in vivo, through an Organic Electrochemical Transistor (OECT)-based biosensor called Bioristor. The sensor was applied to grapevines, apples, and kiwis, revealing its capability to trace the plant water status for the whole productive cycle. A correlation between the sensor response index (R) and environmental parameters such as air humidity and temperature were recorded for fruit species. The day/night oscillation of the ionic content in the transpiration stream varies during plant growth and fruit maturation and during severe drought stress. Bioristor promptly detected the occurrence of drought stress. The gate current (Igs) trend supports the reduction in the saturation of the system due to the lower water availability. The use of Bioristor-acquired indices can be used to improve precision irrigation techniques according to the real plant needs.

An Outlook on Processing Sweet Corn Production from the Last Three Decades (1990s–2010s)

Sweet corn (Zea mays L. var. rugosa or saccharate), consumed both fresh and processed (primarily canned or frozen), is a popular vegetable crop in the United States. Recent nationwide data have reported declining trends in sweet corn production, which poses serious challenges for the US processing sweet corn producers. Here, we evaluated a processing sweet corn dataset that represents nearly 3 decades (1992–2018) of commercial production in the Upper Midwest and the Pacific Northwest regions in an attempt to understand national trends in US processing sweet corn. The objectives of this study were to (a) quantify trends in processing sweet corn production (harvest area and total green ear mass production); (b) understand trends in planting date, plant population density, and hybrid lifespan; and (c) estimate interannual yield deviations in green ear mass yield. Our results reveal declining trends in sweet corn hectares, particularly in rainfed production systems of the Upper Midwest. For the past 3 decades of commercial sweet corn production, plant population density and planting dates used by vegetable processors have remained unchanged. Our analysis revealed a large range (1 to 20 years) in hybrid lifespan, which can be attributed to wide differences in hybrid yield stability across the diverse production environments in the United States. Rainfed production systems are becoming scarcer because sweet corn yields under rainfed conditions are particularly susceptible to severe weather, including heat and drought stress events. Future research is needed to understand sweet corn yields as a function of climatic and nonclimatic variables to stabilize the industry, particularly given predictions of a future with more frequent weather extremes.

Effects of Drought Stress on Non-Structural Carbohydrates in Different Organs of Cunninghamia lanceolata.

The Chinese fir Cunninghamia lanceolata (Lamb.) Hook. is an important timber conifer species in China. Much has been studied about Chinese fir, but the distribution of non-structural carbohydrates (NSCs) among different organs (needles, branch, stem, and roots) under drought stress remains poorly understood. In this study, we used one-year-old C. lanceolata plantlets to evaluate the effects of simulated drought under four water regimes, i.e., adequate water or control, light drought, moderate drought, and severe drought stress corresponding to 80%, 60%, 50%, and 40%, respectively of soil field maximum capacity on various NSCs in the needles, branch, stem and roots. The degree and duration of drought stress had significant effects on fructose, glucose, sucrose, soluble sugar, starch, and NSC content in various organs (p < 0.05). Fructose content increased in stem xylem, stem phloem, and leaves. Glucose and sucrose content declined in stem and branch xylem under light drought stress and moderate drought stress, and increased under severe drought stress conditions. Soluble sugars content declined, and starch content increased in leaf and branch phloem, but the latter could not compensate for soluble sugar consumption in the whole plant, and therefore, total NSCs decreased. Correlation analysis showed that a significant positive correlation existed in the soluble sugar content between leaves and roots, and between xylem and phloem in the stems and branches. Chinese fir appears to have different NSCs distribution strategies in response to drought stress, viz., allocating more soluble sugars to fine roots and increasing starch content in the needles, as well as ensuring osmosis to prevent xylem embolism. Our study may broaden the understanding of the various mechanisms that Chinese fir and other plants have to enhance their tolerance to drought stress.

Xylem function and leaf physiology in European beech saplings during and after moderate and severe drought stress

Abstract The extreme drought events in the last years caused high mortality amongst European beech (Fagus sylvatica L.) across Central Europe. Thus, knowledge of the response of beech to drought and its ability to recover its xylem and leaf functions after drought release is needed to better understand beech survival. In this study, changes in xylem function, leaf gas exchange, chlorophyll fluorescence and morphology of European beech saplings during drought and recovery phases were assessed. Beech saplings were exposed to three different watering intensities—well-watered (W), moderately drought stressed (M) and severely drought stressed (S) for 25 days, and then saplings were rewatered for 14 days. Reduced irrigation caused a drop in shoot water potential to −1.1 and −3.1 MPa in M and S saplings, respectively. Stomatal conductance in M and S saplings decreased to 15 and 5 per cent of that in W saplings, respectively, and it corresponded with a decrease in the photosynthesis rate and chlorophyll fluorescence parameters. Leaf water content and shoot functional xylem area were significantly affected by drought only in S saplings. Hence, these parameters could be used as sensitive indicators that distinguish plants at no risk of mortality from those at increasing risk under drought stress. In S saplings, some leaves also dried from the edges, leaving a green active central part. During the recovery phase, the leaf gas exchange and chlorophyll fluorescence parameters had recovered 4 days after rewatering in M saplings, whereas in S saplings, they were still lower after 2 weeks. Moreover, xylem function did not fully recover in S saplings till the end of the recovery phase. Hence, subsequent drought periods, even of lower intensity, could lead to tree mortality if tree functions have not fully recovered from the previous drought.

Evaluation of growth, yield and elements uptake of grafted tomatoes on several Solanaceous rootstocks exposed to deficit irrigation

A greenhouse experiment was carried out using seven Solanaceous species as rootstocks. Tomato plants were grafted on these rootstocks and after the healing and acclimatization period, were transferred to a soil-based greenhouse and exposed to three irrigation frequencies (3-day interval as control, 6-day and 9-day interval as moderate and severe drought stress) for four months. The results showed that shoot and root dry weight, daily dry matter production and yield were decreased with increasing irrigation intervals. At the same time, harvesting index was not affected by irrigation treatments in any of the grafting combinations. The concentration of N, Ca and Mg in leaf and root tissues were not influenced by irrigation intervals while P was increased in both leaf and root with increasing irrigation intervals and K was increased in leaf and decreased in root tissue. Leaf relative water content and electrolyte leakage were influenced by irrigation treatment. The applied rootstocks had a prominent effect on growth, yield, P and K concentration in leaf and root and reduction of leaf electrolyte leakage. Cherry tomato (Solanum lycopersicum var. cerasiforme) was superior to other rootstocks in terms of measured parameters, followed by Galapagus and Emperador. The positive role of these rootstocks in the mitigation of adverse effects of drought may be related to their vigorous root system. It is concluded that grafting as a healthy technique, since no chemical treatment is required, may increase the resistance of tomato plants against drought stress depending on the genotype of the rootstock.

Pengaruh pemberian kalsium terhadap perubahan karakter anatomi pelepah bibit kelapa sawit tercekam kekeringan

One of the environmental limiting factors on the growth and productivity of oil palm is drought stress. Various studies have shown that besides inhibiting the oil palm’s physiological and biochemical processes, severe drought stress also causes morphological changes in the form of oil palm frond fractures. However, research related to calcium’s role in increasing the oil palm seedling’s resistance exposed to drought stress is still limited. This research was conducted to determine the calcium effect and drought stress on the frond anatomical character changes of oil palm seedlings. The study was conducted using a complete randomized block design consisting of two treatments with three replications. The first treatment is drought stress level: field capacity, moderate, and severe drought stress. The second treatment is calcium dose: 0, 50, 100, and 150%. The results showed that drought stress at moderate and severe levels decreased the length and width of epidermal, hypodermis thickness, phloem, and xylem diameter of oil palm frond seedlings. Supplying Ca at 0.08 g increased the cohesiveness and structural strength of frond tissue by increasing the length and width of epidermal tissue and phloem diameter.

Biochemical and phenological characterization of diverse wheats and their association with drought tolerance genes

Drought is one of the most important wheat production limiting factor, and can lead to severe yield losses. This study was designed to examine the effect of drought stress on wheat physiology and morphology under three different field capacities (FC) viz. 80% (control), 50% (moderate) and 30% (severe drought stress) in a diverse collection of wheat germplasm including cultivars, landraces, synthetic hexaploid and their derivatives. Traits like grain weight, thousand grain weight and biomass were reduced by 38.23%, 18.91% and 26.47% respectively at 30% FC, whereas the reduction rate for these traits at 50% FC were 19.57%, 8.88% and 18.68%. In principal component analysis (PCA), the first two components PC1 and PC2 accounted for 58.63% of the total variation and separated the cultivars and landraces from synthetic-based germplasm. Landraces showed wide range of phenotypic variations at 30% FC compared to synthetic-based germplasm and improved cultivars. However, least reduction in grain weight was observed in improved cultivars which indicated the progress in developing drought resilient cultivars. Allelic variations of the drought-related genes including TaSnRK2.9-5A, TaLTPs-11, TaLTPs-12, TaSAP-7B-, TaPPH-13, Dreb-B1 and 1fehw3 were significantly associated with the phenological traits under drought stress in all 91 wheats including 40 landraces, 9 varieties, 34 synthetic hexaploids and 8 synthetic derivatives. The favorable haplotypes of 1fehw3, Dreb-B1, TaLTPs-11 and TaLTPs-12 increased grain weight, and biomass. Our results iterated the fact that landraces could be promising source to deploy drought adaptability in wheat breeding. The study further identified drought tolerant wheat genetic resources across various backgrounds and identified favourable haplotypes of water-saving genes which should be considered to develop drought tolerant varieties.

Physiological response and transcriptome analyses of leguminous Indigofera bungeana Walp. to drought stress.

Indigofera bungeana is a shrub with high quality protein that has been widely utilized for forage grass in the semi-arid regions of China. This study aimed to enrich the currently available knowledge and clarify the detailed drought stress regulatory mechanisms in I. bungeana, and provide a theoretical foundation for the cultivation and resistance breeding of forage crops. This study evaluates the response mechanism to drought stress by exploiting multiple parameters and transcriptomic analyses of a 1-year-old seedlings of I. bungeana in a pot experiment. Drought stress significantly caused physiological changes in I. bungeana. The antioxidant enzyme activities and osmoregulation substance content of I. bungeana showed an increase under drought. Moreover, 3,978 and 6,923 differentially expressed genes were approved by transcriptome in leaves and roots. The transcription factors, hormone signal transduction, carbohydrate metabolism of regulatory network were observed to have increased. In both tissues, genes related to plant hormone signaling transduction pathway might play a more pivotal role in drought tolerance. Transcription factors families like basic helix-loop-helix (bHLH), vian myeloblastosis viral oncogene homolog (MYB), basic leucine zipper (bZIP) and the metabolic pathway related-genes like serine/threonine-phosphatase 2C (PP2C), SNF1-related protein kinase 2 (SnRK2), indole-3-acetic acid (IAA), auxin (AUX28), small auxin up-regulated rna (SAUR), sucrose synthase (SUS), sucrosecarriers (SUC) were highlighted for future research about drought stress resistance in Indigofera bungeana. Our study posited I. bungeana mainly participate in various physiological and metabolic activities to response severe drought stress, by regulating the expression of the related genes in hormone signal transduction. These findings, which may be valuable for drought resistance breeding, and to clarify the drought stress regulatory mechanisms of I. bungeana and other plants.

Rapid drought-recovery of gas exchange in Caragana species adapted to low mean annual precipitation.

While variation in mean annual precipitation (MAP) of the native habitat of a species has been shown to determine the ability of a species to resist a hydraulic decrease during drought, it remains unknown whether these variations in MAP also influence the ability of a species to recover and survive drought. Leaf hydraulic and gas exchange recovery following drought and the underlying mechanisms of these responses in six Caragana species from habitats along a large precipitation gradient were investigated during rehydration in a common garden. The gas exchange of species from arid habitats recovered more rapidly during rehydration after mild, moderate and severe drought stress treatments than species from humid habitats. The recovery of gas exchange was not associated with foliar abscisic acid concentration, but tightly related to the recovery of leaf hydraulic conductance (Kleaf ). The recovery of Kleaf was associated with the loss of Kleaf during dehydration under mild and moderate drought stress, and to leaf xylem embolism formation under severe drought stress. Results pointed to the different ability to recover in gas exchange in six Caragana species post-drought is associated with the MAP of the species in its native habitat.

Influence of severe drought on mineral nutrient status in eastern white pine (Pinus strobus L)

The photochemical process of photosynthesis is significantly influenced by the availability of nutrients. The purpose of this research is to ascertain how photosynthetic pigment function is affected by nutrient elemental changes caused by severe drought stress. Using elemental analysis, we looked at the changes in mineral nutrient composition in eastern white pine (Pinus strobus L) seedlings 32 days after drought treatment. According to our findings, severe drought resulted in a significant and non-significant decrease in the contents of Chl “b and a”, respectively. The elemental composition of iron (Fe), zinc (Zn), magnesium (Mg), potassium (K), phosphorus (P) and nitrogen (N) was measured. After severe drought treatment, leaf nutrient status showed a significant decline in total N (control-1.57 ± 0.1; drought-0.65 ± 0.07), P (control-959.4 ± 17; drought-645 ± 46), Mg (control-1030.4 ± 33; drought-750.7 ± 76), and K (control-3062.5 ± 32; drought-1853.3 ± 198), with a non-significant decrease in leaf Fe (control-120.3 ± 20; drought-98.9 ± 28) and increase in leaf Zn (control-33.49 ± 2; drought-39.05 ± 4). A positive correlation was found between the content of Fe, P, Mg, K, and N in leaf Chl “b”, but only a positive correlation was found between the content of Zn in leaf Chl “a” during severe drought. During severe drought, nutrient reallocation has a significant impact on leaf chlorophyll levels, as evidenced by this correlation.

Different Responses to Water Deficit of Two Common Winter Wheat Varieties: Physiological and Biochemical Characteristics.

Since water scarcity is one of the main risks for the future of agriculture, studying the ability of different wheat genotypes to tolerate a water deficit is fundamental. This study examined the responses of two hybrid wheat varieties (Gizda and Fermer) with different drought resistance to moderate (3 days) and severe (7 days) drought stress, as well as their post-stress recovery to understand their underlying defense strategies and adaptive mechanisms in more detail. To this end, the dehydration-induced alterations in the electrolyte leakage, photosynthetic pigment content, membrane fluidity, energy interaction between pigment-protein complexes, primary photosynthetic reactions, photosynthetic and stress-induced proteins, and antioxidant responses were analyzed in order to unravel the different physiological and biochemical strategies of both wheat varieties. The results demonstrated that Gizda plants are more tolerant to severe dehydration compared to Fermer, as evidenced by the lower decrease in leaf water and pigment content, lower inhibition of photosystem II (PSII) photochemistry and dissipation of thermal energy, as well as lower dehydrins' content. Some of defense mechanisms by which Gizda variety can tolerate drought stress involve the maintenance of decreased chlorophyll content in leaves, increased fluidity of the thylakoid membranes causing structural alterations in the photosynthetic apparatus, as well as dehydration-induced accumulation of early light-induced proteins (ELIPs), an increased capacity for PSI cyclic electron transport and enhanced antioxidant enzyme activity (SOD and APX), thus alleviating oxidative damage. Furthermore, the leaf content of total phenols, flavonoids, and lipid-soluble antioxidant metabolites was higher in Gizda than in Fermer.

Influence of drought stress and mycorrhizal (Funneliformis mosseae) symbiosis on growth parameters, chlorophyll fluorescence, antioxidant activity, and essential oil composition of summer savory (Satureja hortensis L.) plants.

Drought stress unfavorably influences the growth and physiological traits of plants in the arid and semi-arid regions of the world. This study aimed to determine the effects of arbuscular mycorrhiza fungi (AMF; Funneliformis mosseae) inoculation on the physiological and biochemical responses of summer savory (Satureja hortensis L.) under different irrigation regimes. The first factor was different irrigation regimes, including no drought stress (100% field capacity; FC), moderate drought stress (60% FC), and severe drought stress (30% FC); the second factor included the plants without AMF (AMF0) and with AMF inoculation (AMF1). The results showed that better values, higher plant height, shoot mass (fresh and dry weight), relative water content (RWC), membrane stability index (MSI), photosynthesis pigments, Fv, Fm, Fv/Fm, and total soluble proteins were obtained in the plants inoculated with AMF. The highest values were obtained for plants with no drought stress, then the plants subjected to AMF1 under 60% FC, and the lowest ones for plants under 30% FC without AMF inoculation. Thus, these properties are reduced under moderate and severe drought stress. At the same time, the utmost activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and the highest malondialdehyde (MDA), H2O2, proline, and antioxidant activity (TAA) were achieved for 30% FC + AMF0. It was also found that AMF inoculation improved essential oil (EO) composition, also as EO obtained from plants under drought stress. Carvacrol (50.84-60.03%) was the dominant component in EO; γ-terpinene (19.03-27.33%), p-cymene, α-terpinene, and myrcene, were recognized as other important components in EO. The higher carvacrol and γ-terpinene contents were obtained from summer savory plants with AMF inoculation and the lowest for plants without AMF and under 30% FC. According to the present findings, using AMF inoculation could be a sustainable and eco-friendly approach to improve physiological and biochemical characteristics and the essential oil quality of summer savory plants under water shortage conditions.