Reduction In Relative Water Content Research Articles

Comparative analysis of salinity tolerance mechanisms in two maize genotypes: growth performance, ion regulation, and antioxidant responses.

This study investigates the differential responses of two maize genotypes, SC180 and SC168, to salt stress, aiming to elucidate the mechanisms underlying salinity tolerance and identify traits associated with improved stress resilience. Salinity stress, imposed by 150mM NaCl, adversely affected various growth parameters in both genotypes. SC180 exhibited a more pronounced reduction in shoot length (13.6%) and root length (13.6%) compared to SC168, which showed minimal reductions (3.0% and 2.3%, respectively). Additionally, dry weight losses in SC180's leaves, stems, and roots were significantly greater than those in SC168. Under salinity stress, both genotypes accumulated Na+ in all organs, with SC168 showing higher Na + concentrations. However, K+ levels decreased more significantly in SC180's leaves than in SC168's. The study also assessed physiological responses, noting that SC180 experienced a substantial reduction in relative water content (RWC) in leaves (22.7%), while SC168's RWC remained relatively stable (5.15%). Proline accumulation, a marker for osmotic adjustment, increased 2.3-fold in SC168 compared onefold in SC180. Oxidative stress indicators, such as electrolyte leakage and hydrogen peroxide levels, were elevated in both genotypes under salt stress, with SC180 showing higher increases (48.5% and 48.7%, respectively) than SC168 (35.25% and 22.0%). Moreover, antioxidant enzymes (APX, CAT, POD, SOD, GR) activities were significantly enhanced in SC168 under salinity stress, whereas SC180 showed no significant changes in these activities. Stress indices, used to quantify and compare salinity tolerance, consistently ranked SC168 as more tolerant (average rank = 1.08) compared to SC180 (average rank = 1.92). Correlation analyses further confirmed that SC168's superior tolerance was associated with better Na + regulation, maintenance of K+ levels, and a robust antioxidant defense system. In conclusion, SC168 demonstrated greater resilience to salinity stress, attributed to its efficient ion regulation, stable water status, enhanced osmotic adjustment, and strong antioxidant response. These findings provide valuable insights for breeding and developing salinity-tolerant maize varieties.

The jasmonate pathway and water loss in rice leaves induced by a stem-borer inhibit leaf-feeder growth.

Plant-mediated interactions between herbivores play an important role in regulating the composition of herbivore community. The fall armyworm (FAW), Spodoptera frugiperda, which has become one of the most serious pests on corn in China since it invaded in 2018, has been found feeding rice in the field. However, how FAW interacts with native rice insect pests remains largely unknown. Here, we investigated the interaction between FAW and a resident herbivore, striped stem borer (SSB, Chilo suppressalis) on rice. The infestation of rice leaf sheaths (LSs) by SSB larvae systemically enhanced the level of jasmonic acid (JA), abscisic acid (ABA), and trypsin proteinase inhibitors (TPIs), reduced relative water content (RWC) in leaf blades (LBs), and suppressed the growth of FAW larvae. In contrast, because FAW larvae infested LBs and did not affect defence responses in LSs, they did not influence the performance of SSB larvae. Using different mutants, together with bioassays and chemical analysis, we revealed that SSB-induced suppression of FAW larvae growth depended on both the SSB-activated JA pathway and RWC in LBs, whereas the ABA pathway activated by SSB larvae promoted the growth of FAW larvae by impeding water loss. These results provide new insights into mechanisms underlying plant-mediated interactions between herbivores.

Humic acid and grafting as sustainable agronomic practices for increased growth and secondary metabolism in cucumber subjected to salt stress

Salinity stress poses a significant treat to crop yields and product quality worldwide. Application of a humic acid bio stimulant and grafting onto tolerant rootstocks can both be considered sustainable agronomic practices that can effectively ameliorate the negative effects of salinity stress. This study aimed to assess the above mentioned ameliorative effects of both practices on cucumber plants subjected to saline environments. To attain this goal a factorial experiment was carried out in the form of a completely randomized design with three replications. The three factors considered were (a) three different salinity levels (0, 5, and 10 dS m−1 of NaCl), (b) foliar application of humic acid at three levels (0, 100, and 200 mg L−1), and (c) both grafted and ungrafted plants. Vegetative traits including plant height, fresh and dry weight and number of leaf exhibited a significant decrease under increasing salinity stress. However, the application of humic acid at both levels mitigated these effects compared to control plants. The reduction in relative water content (RWC) of the leaf caused by salinity, was compensated by the application of humic acid and grafting. Thus, the highest RWC (86.65%) was observed in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. Electrolyte leakage (EL) increased under salinity stress, but the application of humic acid and grafting improved this trait and the lowest amount of EL (26.95%) was in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. The highest amount of catalase (0.53 mmol H2O2 g−1 fw min−1) and peroxidase (12.290 mmol H2O2 g−1 fw min−1) enzymes were observed in the treatment of 10 dS m−1 of NaCl and 200 mg L−1 humic acid. The highest amount of total phenol (1.99 mg g−1 FW), total flavonoid (0.486 mg g−1 FW), total soluble carbohydrate (30.80 mg g−1 FW), soluble protein (34.56 mg g−1 FW), proline (3.86 µg g−1 FW) was in grafting plants with 0 dS m−1 of NaCl and 200 mg L−1 of humic acid. Phenolic acids and phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) enzymes increased with increasing salinity and humic acid levels. Contrary to humic acid, salt stress increased the sodium (Na+) and chlorine (Cl−) and decreased the amount of potassium (K+) and calcium (Ca2+) in the root and leaf of ungrafted cucumber. However, the application 200 mg L−1 humic acid appeared to mitigate these effects, thereby suggesting a potential role in moderating physiological processes and improving growth of cucumber plants subjected to salinity stress. According to the obtained results, spraying of humic acid (200 mg L−1) and the use of salt resistant rootstocks are recommended to increase tolerance to salt stress in cucumber. These results, for the first time, clearly demonstrated that fig leaf gourd a new highly salt-tolerant rootstock, enhances salt tolerance and improves yield and quality of grafted cucumber plants by reducing sodium transport to the shoot and increasing the amount of compatible osmolytes.

Supplemental Sodium Nitroprusside and Spermidine Regulate Water Balance and Chlorophyll Pigments to Improve Sunflower Yield under Terminal Drought.

Drought is an inevitable environmental stress that drastically hampers the growth, productivity, and quality of food crops. Exogenous sodium nitroprusside and spermidine have decisive functions in the growth enhancement of plants; nevertheless, their specific role in mediating stress responses to improve drought tolerance in sunflowers at the reproductive stage (terminal drought) remains largely unknown. In the present study, we explored the positive effects of sodium nitroprusside and spermidine on physiological responses to increase in sunflower yield during periods of terminal drought. Initially, various doses (50, 100, 150, 200, 400 μM) for each sodium nitroprusside or spermidine were foliar sprayed to improve water content, chlorophylls, and biomass accumulation in sunflower seedlings under control (100% FC) and drought (60% FC) conditions. Optimized rates (100 μM for sodium nitroprusside) and (100 μM for spermidine) were further tested alone and in combination to assess drought tolerance potential and their ultimate impact on yield under drought stress. Drought exposure caused a marked reduction in relative water content (26%) and chlorophyll a (31%) and b (35%) contents; however, sodium nitroprusside and spermidine at 100 μM significantly improved the growth of sunflower (13%). Furthermore, combined use of sodium nitroprusside and spermidine at 100 + 100 μM markedly improved the achenes per head (16%), 1000-achene weight (14%), and ultimately grain (28%) and oil (21%) yields of sunflowers under drought stress. A strong association was found between the 1000-achene weight and the achene yield of sunflower. Hence, combined sodium nitroprusside and spermidine upregulate water balance and chlorophyll contents to increase sunflower yield under terminal drought.

Selenium treatment alters the accumulation of osmolytes in arsenic-stressed rice (Oryza sativa L.).

Arsenic (As), one of the major pollutants in the soil, is an important environmental concern as its consumption can cause adverse health symptoms in living organisms. Its contamination of rice grown over As-contaminated areas is a serious concern in South Asian countries. Selenium (Se) has been reported to influence various osmolytes under metal stress in plants. The present study reports the role of Se in mitigating As stress in rice by modulating osmolyte metabolism. Rice plants grown in As-amended soil (2.5-10mgkg-1) in pots were treated with sodium selenate (0.5-1.0mg Se kg-1 soil) in glass house conditions and leaf samples were collected at 60 and 90days after sowing (DAS). As-treated rice leaves displayed a reduction in relative water content (RWC) and dry weight than control with a maximum reduction of 1.68- and 2.47-fold in RWC and 1.95- and 1.69-fold in dry weight in As10 treatment at 60 and 90 DAS, respectively. Free amino acids (1.38-2.26-fold), proline (3.88-3.93-fold), glycine betaine (GB) (1.27-1.72-fold), choline (1.67-3.1-fold), total soluble sugars (1.29-1.61-fold), and reducing sugars (1.67-2.19-fold) increased in As-treated rice leaves as compared to control at both stages. As stress increased the γ-aminobutyric acid (GABA), putrescine content, and glutamate decarboxylase activity whereas diamine oxidase and polyamine oxidase activities declined by 1.69-1.88-fold and 1.52-1.86-fold, respectively. Se alone or in combination with As improved plant growth, RWC, GB, choline, putrescine, and sugars; lowered proline and GABA; and showed a reverse trend of enzyme activities related to their metabolism than respective As treatments. As stress resulted in a higher accumulation of osmolytes to combat its stress which was further modulated by the Se application. Hence, the current investigation suggested the role of osmoprotectants in Se-induced amelioration of As toxicity in rice plants.

Evaluation of Morpho-Physiological Traits of Oat (Avena sativa L.) under Drought Stress

The increase in intensity and frequency of drought due to global climate change has increased the urgency of developing crop cultivars suitable for dry environments. Drought tolerance is a complex trait that involves numerous physiological, biochemical, and morphological responses. A better understanding of those mechanisms is critical to develop drought tolerant cultivars. In this study, we aimed to understand the morphophysiological changes at the shoot and root levels in response to drought stress of ten oat genotypes with diverse root morphological characteristics. Twenty-one-day old plants were subjected to drought stress in a greenhouse by withholding water for two weeks. Several characteristics including chlorophyll content, relative water content (RWC), stomatal conductance, stomata number, shoot dry weight (SDW), root dry weight (RDW), root-to-shoot biomass ratio (RSR), root length, root area, and root volume were measured on well-watered, and drought-stressed plants. Grain yield was evaluated by continuing the drought treatment with a drying and rewatering cycle every 15 days until physiological maturity. The water regime had a significant impact on all traits evaluated. A significant interaction between genotype and water treatment was observed for RWC, chlorophyll content, stomatal conductance, stomata number, and grain yield but not for root traits, suggesting that the root system of all genotypes responded similarly to drought stress. Hayden, the cultivar with the lowest reduction in grain yield from the drought treatment, was among the genotypes with the lowest reduction in RWC and chlorophyll content but with a sharp decrease in stomata number, thus indicating that regulating the plant water status and maintaining the photosynthesis level are important for oat plants to maintain grain yield under drought stress. The size of the root system was not correlated with grain yield under drought, but the RWC and grain yield were significantly correlated under drought, thus suggesting that maintaining the RWC is an important characteristic for oat plants to maintain yield under drought stress.

Osmotic regulators in cowpea beans plants under water deficiency.

Cowpea is a leguminous plant belonging to the fabaceae family cultivated in the North and Northeast regions of Brazil, with productive potential. Among the abiotic factors, water deficiency is one of the main environmental limitations that influence agricultural production in the world. The objective of this work was to study the relative water content and osmoregulators of cowpea plants subjected to water stress. The experiment was carried out in a greenhouse at the Universidade Federal Rural da Amazônia (UFRA, Belém, PA), cowpea plants BR-17 Gurguéia Vigna unguiculata (L.) Walp were used. The experimental design was completely randomized (DIC) in a 2 × 2 factorial scheme, two water conditions (control and water deficit) and two times of stress (four and six days of water suspension), with 7 replications, totaling 28 experimental units. The water deficit affected plants, causing a reduction in relative water content (69.98%), starch (12.84% in leaves and 23.48% in roots) and carbohydrates (84.34%), and an increase in glycine-betaine, sucrose (114.11% in leaves and 18.71% in roots) and proline (358.86%) at time 2. The relative water content was negatively affected by water conditions, with a decrease in relation to the interaction of the aerial part and the root system. Therefore, greater metabolic responses were noted in plants that were subjected to stress treatment at time 2 (6 days).

Physiological and biochemical responses of rice to polyethylene glycol

Effects of water deficit induced by polyethylene glycol (PEG-6000) on rice grown in half strength Hoagland solution was studied in the present investigation. Impacts of different water stress (10, 20 and 30% PEG) on some physiological and biochemical characteristics were determined in this investigation. Results showed that water stress significantly affected most physiological and biochemical characteristics. The increasing water stress declined the root and shoot length and fresh and dry weights of root and shoot. An increase in water stress also resulted in reduction of relative water content, leaf pigments and protein content. Upon dehydration, an incline in reducing and total sugar and proline content were evident in the root and shoot of rice. Water-deficit stress resulted in higher superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities but as the severity of the water stress increased, the SOD activity decreased. These crucial characteristics would be expected to be utilized as screening techniques for water stress tolerance to the future development of new variety. Bangladesh J. Bot. 52(4): 897-905, 2023 (December)

Physiological and Transcriptome Analysis of the Effects of Exogenous Strigolactones on Drought Responses of Pepper Seedlings.

Drought stress significantly restricts the growth, yield, and quality of peppers. Strigolactone (SL), a relatively new plant hormone, has shown promise in alleviating drought-related symptoms in pepper plants. However, there is limited knowledge on how SL affects the gene expression in peppers when exposed to drought stress (DS) after the foliar application of SL. To explore this, we conducted a thorough physiological and transcriptome analysis investigation to uncover the mechanisms through which SL mitigates the effects of DS on pepper seedlings. DS inhibited the growth of pepper seedlings, altered antioxidant enzyme activity, reduced relative water content (RWC), and caused oxidative damage. On the contrary, the application of SL significantly enhanced RWC, promoted root morphology, and increased leaf pigment content. SL also protected pepper seedlings from drought-induced oxidative damage by reducing MDA and H2O2 levels and maintaining POD, CAT, and SOD activity. Moreover, transcriptomic analysis revealed that differentially expressed genes were enriched in ribosomes, ABC transporters, phenylpropanoid biosynthesis, and Auxin/MAPK signaling pathways in DS and DS + SL treatment. Furthermore, the results of qRT-PCR showed the up-regulation of AGR7, ABI5, BRI1, and PDR4 and down-regulation of SAPK6, NTF4, PYL6, and GPX4 in SL treatment compared with drought-only treatment. In particular, the key gene for SL signal transduction, SMXL6, was down-regulated under drought. These results elucidate the molecular aspects underlying SL-mediated plant DS tolerance, and provide pivotal strategies for effectively achieving pepper drought resilience.

Morpho-Anatomical, Physiological and Biochemical Adjustments in Response to Heat and Drought Co-Stress in Winter Barley.

This study aimed to investigate the combined effect of high temperatures 10 °C above the optimum and water withholding during microgametogenesis on vegetative processes and determine the response of winter barley genotypes with contrasting tolerance. For this purpose, two barley varieties were analyzed to compare the effect of heat and drought co-stress on their phenology, morpho-anatomy, physiological and biochemical responses and yield constituents. Genotypic variation was observed in response to heat and drought co-stress, which was attributed to differences in anatomy, ultrastructure and physiological and metabolic processes. The co-stress-induced reduction in relative water content, total soluble protein and carbohydrate contents, photosynthetic pigment contents and photosynthetic efficiency of the sensitive Spinner variety was significantly greater than the tolerant Lambada genotype. Based on these observations, it has been concluded that the heat-and-drought stress-tolerance of the Lambada variety is related to the lower initial chlorophyll content of the leaves, the relative resistance of photosynthetic pigments towards stress-triggered degradation, retained photosynthetic parameters and better-preserved leaf ultrastructure. Understanding the key factors underlying heat and drought co-stress tolerance in barley may enable breeders to create barley varieties with improved yield stability under a changing climate.

Investigating the phytotoxic potential of Carlina acaulis essential oil against the weed Bidens pilosa through a physiological and metabolomic approach

Essential oils (EOs) are widely studied as possible candidates for new eco-friendly herbicides for weed management due to their phytotoxicity. In this study we tested the phytotoxic potential of the EO obtained from the roots of Carlina acaulis L. (Apiaceae) against the weed Bidens pilosa L. This EO, containing 98% of the polyacetylene carlina oxide, showed strong phytotoxic effects on the plant metabolism, such as leaf necrosis, reduction of relative water content and total leaf area, and an increase in the dry weight/fresh weight ratio, suggesting a water status alteration. The EO also damaged the photosynthetic machinery, as evidenced by the significant reduction of the effective quantum yield of photosystem II (ΦII) and the maximum quantum yield of photosystem II (Fv/Fm). In addition, the non-photochemical quenching (ΦNPQ) significantly increased after spraying with C. acaulis EO. Damage to photosystem II was further demonstrated through the reduction of manganese and calcium concentrations, possibly due to an alteration in the correct functionality of the Mn4Ca cluster of the PSII. Metabolomics analysis revealed an accumulation of branched-chain amino acids, such as isoleucine and valine, which is commonly related to osmotic alterations under drought stress situations and a general reduction in sugar content (fructose, glucose, mannose, among others), suggesting reduction of the photosynthetic efficiency too. Overall, these findings suggest C. acaulis EO as a promising natural product with phytotoxic potential against weeds that deserves further investigation.

Root phenological and physiological response of maize (Zea mays L.) for adaptation under drought stress at vegetative and reproductive stages ​

Drought stress is known to negatively affect vegetative growth and biomass production, as well as the development of reproductive organs and yield characteristics in maize. The crop root systems are crucial for adaptability to various biotic and abiotic stresses, but studies addressing this are quite limited. The experiment was conducted simultaneously in both glasshouse and field condition during summer 2022 at TNAU, Coimbatore. The study was focussed to assess the root system architecture (RSA) of the drought tolerant and drought susceptible hybrids using PVC cylinders by imposing stress at V4 stage and root pulled out from the fieldby imposing stress at V14 stage. The results from the study showed that the significant variation was observed in both latter vegetative and mature root system under drought stress. Apart, the reduction in relative water content, SPAD values and increase of proline content were observed. The photosynthetic rate and gas exchange parameters were decreased upon exposure to drought stress. On considering, the hybrid N10-51 × DQL80 can accumulate osmolytes, maintaining tissue water potential and photosynthetic functionality for longer time when compared to other hybrids. This hybrid also exhibited the deep rooting ability with high yield under drought stress. Hence, it was identified as the drought tolerant hybrid and could be commercialized after testing their yield stability.

Foliar application of putrescine alleviates terminal drought stress by modulating water status, membrane stability, and yield- related traits in wheat (Triticum aestivum L.).

Drought stress is one of the major limitations to the growth and yield productivity of cereal crops. It severely impairs the early growing and grain -filling stages of wheat. Therefore, cost- effective and eco-friendly approaches for alleviating drought stress in cereal crops are in high demand. Polyamines, such as putrescine, have a significant effect on improving crop yield under drought- stress conditions. Therefore, the current study was executed with the aim of exploring the significance of putrescine in alleviating drought stress and improving yield- related traits in wheat. Two distinct wheat cultivars (Fakhar-e-Bhakkar and Anaj-2017) were treated with the foliar application of different concentrations (control, 0.5, 1.0, and 1.5 PPM) of putrescine (put) under two moisture conditions (well- watered and terminal drought stress). The results demonstrate that the imposition of terminal drought stress significantly reduces different physiological and yield- related traits of both wheat cultivars. The reduction of relative water content (RWC%), membrane stability index (MSI), leaf area, tillers per plant, biomass yield, number of spikelets per spike, 100-grain weight, grain yield per plant, and straw yield was greater in Anaj-2017 than in Fakhar-e-Bhakkar cultivar. The results further explain that the foliar application of increased concentrations of putrescine from 0.0 to 1.0 PPM gradually improved physiological and yield traits, whereas these traits declined with the application of putrescine at the highest dose (1.5 PPM). The exogenous application of 1.0 PPM putrescine improved the relative water content (19.76%), specific leaf area (41.47%), and leaf area ratio (35.84%) compared with the controlled treatment. A higher grain yield (28.0g plant-1) and 100-grain weight (3.8g) were obtained with the foliar application of 1.0 PPM putrescine compared with controlled treatments. The findings of this study confirm the protective role of putrescine against terminal drought stress. It is therefore recommended to use putrescine at a concentration of 1.0 PPM, which could help alleviate terminal drought stress and attain better wheat yield.

Alleviation of the adverse effects of NaCl stress on tomato seedlings (Solanum lycopersicum L.) by Trichoderma viride through the antioxidative defense system

BackgroundTrichoderma viride are well known for their biocontrol capabilities, but little is known about how they stimulate plant development and increase their resistance to salt stress. One of the main abiotic factors limiting crop development and yield is salt stress. Therefore, the purpose of this work was to ascertain how NaCl effects on T. viride growth as well as on the seedlings morphological and physio-biochemical parameters of tomato (Solanum lycopersicum L.) under plate culture conditions. Additionally, a pot experiment was conducted to determine how T. viride affected the development characteristics of tomato plants subjected to various salt concentrations (50 and 100 mM NaCl). T. viride's contribution to tomato seedling stress tolerance was also closely examined.ResultsResults showed that 100 mM NaCl decreased the colony diameter of T. viride by 13.4% compared to the control. Under plate and greenhouse conditions, tomato seedlings exposed to salt exposure exhibited an overall decline in growth. Also, a reduction in relative water content (RWC) and protein contents occurred under salt stress. At the same time, increases were found in proline, total phenolics, flavonoids, H2O2 content, malondialdehyde, likewise the activities of peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), and ascorbate peroxidase (APX) enzymes. Even though, with T. viride application, the salt negative effects on both morphological and physio-biochemical parameters were mitigated to a greater extent. T. viride increased proline and total antioxidant capacity (TAC) in tomato seedlings at 100 mM NaCl by an average of 20.66 and 43.82% compared to their comparable control. T. viride increased the activities of CAT, PPO, and APX enzymes by 74.6, 58.48, and 61.61% at 50 mM NaCl compared to non-saline control seedlings. As well, T. viride decreased MDA and H2O2 contents by an average of 14 and 24.8% in tomato seedlings at 50 mM NaCl compared to their comparable control. Also, under 100 mM NaCl, the T. viride-treated tomato seedlings showed increased total phenolics (17.85%) and flavonoids (33.17%) compared to non- treated one.ConclusionHence, our research sheds new insight on the pathways by which T. viride can boost tomato seedling tolerance to salt stress at morphological and physio-biochemical levels by activating both enzymatic and non-enzymatic antioxidant defense systems.

Ecklonia maxima-derivate seaweed extract supply as mitigation strategy to alleviate drought stress in chicory plants

Extreme climatic conditions have a severe repercussion on agriculture and on food availability. Ecological means to overcome drought are important to improve agroecosystems sustainability and resilience. The use of an Ecklonia maxima-derivate seaweed extract (SwE) as a tool to mitigate drought constrain in chicory plants grown in greenhouse was evaluated. Plants were cultivated in plastic pots filled with peat and subjected to drought stress by retaining moisture range at 90–100% of water holding capacity (WHC) [well-watered (WW)], 60–70% WHC [moderate drought stress (MDS)] or 30–40% WHC [severe drought stress (SDS)]. Drought stress decreased plant growth traits and yield. However, in plants supplied with SwE, head fresh mass was 7.6% higher than control. Water constrain reduced relative water content (RWC), whereas, SwE improved RWC when plants were exposed to drought. Moreover, water use efficiency (WUE) increased as drought intensity increased and plants exposed to drought significantly improved WUE when supplied with SwE. Drought stress intensity linearly reduced nitrogen use efficiency (NUE) in plants exposed to MDS and SDS, compared with WW plants. SwE application enhanced NUE by 7.7% compared with control plants. Exposing chicory plants to drought stress resulted in a significantly higher N and Mg concentration compared to WW plants. Conversely, drought reduced P and K in leaf tissues. SwE supply increased P, K, Ca and Mg content, whereas reduced N. Chlorophyll was reduced by drought, while SwE supply increased its concentration. Sugars increased as drought stress intensity increased. Water constrain enhanced malondialdehyde, especially in SwE non-treated plants. Drought stress improved proline and total polyphenols in plants supplied with SwE. Biostimulated plants grown under WW or MDS conditions showed higher ascorbic acid level than those exposed to SDS and non-biostimulated. The study proved that SwE application is a useful practice to mitigate drought in chicory plants, safeguarding yield and quality features.

Osmo‐protectants improve cotton yield by alleviating moisture stress under semi‐arid conditions

AbstractIn north‐western India, short‐term droughts due to insufficient rainfall or irrigation canal closures are common. To quantify seed cotton yield (SCY) loss under moisture deficit and evaluate the efficacy of foliar‐applied osmo‐protectants (OPs), a 2‐year field experiment was conducted with three moisture regimes (M1: well watered, M2: rainfed after single post‐sowing irrigation [POSI], and M3: rainfed after two POSIs) in main plots and eight OPs (S1: control, S2: four sprays of 2% urea at weekly intervals, S3: four sprays of 2% KNO3 at weekly intervals, S4: single spray of 500 mg kg−1 thio urea [TU], S5: single spray of 50 mg kg−1 salicylic acid [SA], S6: single spray of 100 mg kg−1 glycine betaine [GB], S7: single spray of 100 mg kg−1 SA, and S8: three sprays of 1% pink pigmented facultative methylobacteria at 10 days interval) in sub‐plots of a split plot design. Moisture stress induced a reduction of relative water content (RWC) and consequently decreased SCY by 17% and 32.9% under M3 (2821 kg ha−1) and M2 (2291 kg ha−1), respectively, compared to M1 (3418 kg ha−1). Except for TU, all tested OPs improved SCY by 6.3%–23.7% in comparison to the nontreated control. Application of SA and GB enhanced photosynthesis, improved stomatal conductance, and maintained higher RWC. Application of SA at 100 mg kg−1 resulted in an additional income of US$458 ha−1 and was the most economical treatment for countering short‐term drought.

Effect of drought on aquaporin expression in grafted and ungrafted grapevine cultivars

Drought stress severely affects growth, development and productivity in most agricultural crops. Since ancient times, rootstocks have been used to enable crop cultivation in unsuitable soil conditions. In the present study, three factors were evaluated: 1) cultivar: Vitis vinifera L. cv. ‘Horozkarası’ (drought-tolerant) and cv. ‘Kabarcık’ (drought-sensitive) were used; 2) rootstock: each cultivar was self-rooted and grafted onto ‘Rupestris du Lot’ rootstock; 3) drought stress: half of each cultivar/rootstock combination underwent drought stress and the other half was irrigated at field capacity for seven days. In order to estimate the responses of the cultivars, relative water content, proline content and aquaporin isoform expression levels (VvPIP2;1, VvPIP2;2, VvTIP1;1, and VvTIP2;1) were quantified. The results revealed that drought stress caused more reduction in relative water content (RWC) in ‘Kabarcık’ cultivar (drought-sensitive) than in ‘Horozkarası’ cultivar (drought-tolerant). Proline content increased in both cultivars in response to drought stress but to a relatively greater extent in the grafted ‘Kabarcık’ cultivar. Considering expression levels of genes, VvPIP2;1, VvPIP2;2, and VvTIP2;1 were downregulated whilst VvTIP1;1 was upregulated in the leaf. Both ‘Horozkarası’ and ‘Kabarcık’ cultivars showed similar trends in terms of their responses to drought stress. Grafting significantly increased the proline content in both cultivars exposed to drought stress. The rootstock conferred better drought protection to ‘Kabarcık’ cultivar than to ‘Horozkarası’ cultivar.

24‐Epibrassinolide promotes activation of physiological compensation mechanisms in response to drought stress and rehydration and improves yield in soybean

AbstractDrought stress is the main limiting factor for the yield of soybean crop in the world. Alternatives to minimize the impacts of water deficit on plants involve the application of plant bioregulators, among which Brassinosteroids stand out. In this study, nodulated soybean plants were used to investigate the ability of the 24‐epibrassinolide (EBR) bioregulator to reduce the damage caused to physiological mechanisms, growth and yield, after application in the vegetative stage of soybean plants, subjected to drought stress and rehydration. Application of EBR in plants subjected to drought stress promoted better performance in the rates of transpiration, photosynthesis and instantaneous water use efficiency compared to plants without EBR. The lowest reductions in relative water content and leaf water potential were recorded in stressed soybean plants treated with EBR. Plants under drought stress treated with EBR showed increase in the effective photochemical efficiency of PSII. In addition, soybean plants that received EBR application showed lower oxidative damage to cell membranes. The positive effect of EBR remained after soybean rehydration. Plants treated with EBR showed better recovery with greater plant height, leaf area, lower number of aborted grains, in addition to an increase in stem (37.2%), root (62.8%), leaf (51.8%) dry matter and 1000 seed weight (33%) compared to plants without EBR. This information suggests that EBR not only mitigated the deleterious effect of drought stress but also improved plant growth and yield post‐stress.

Structural breakdown and phytotoxic assessments of PE degradation through acid hydrolysis, starch addition and Pseudomonas aeruginosa bioremediation

Vast amounts of plastic waste are causing serious environmental issues and urge to develop of new remediation methods. The aim of the study is to determine the role of inorganic (nitric acid), organic (starch addition), and biological (Pseudomonas aeruginosa) soil amendments on the degradation of Polyethylene (PE) and phytotoxic assessment for the growth of lettuce plant. The PE-degrading bacteria were isolated from the plastic-contaminated soil. The strain was identified as Pseudomonas aeruginosa (OP007126) and showed the highest degradation percentage for PE. PE was pre-treated with nitric acid as well as starch and incubated in the soil, whereas P. aeruginosa was also inoculated in PE-contaminated soils. Different combinations were also tested. FTIR analysis and weight reduction showed that though nitric acid was efficient in degradation, the combined application of starch and bacteria also showed effective degradation of PE. Phytotoxicity was assessed using morphological, physiological, and biochemical parameters of plant. Untreated PE significantly affected plants' physiology, resulting in a 45% reduction in leaf chlorophyll and a 40% reduction in relative water content. It also had adverse effects on the biochemical parameters of lettuce. Bacterial inoculation and starch treatment mitigated the harmful impact of stress and improved plants' growth as well as physiological and biochemical parameters; however, the nitric treatment proved phytotoxic. The observed results revealed that bacteria and starch could be effectively used for the degradation of pre-treated PE.

Differential Physiological Traits, Ion Homeostasis and Cane Yield of Sub-Tropical Sugarcane Varieties in Response to Long-Term Salinity Stress

Sugarcane grown under a wide range of agro-climatic conditions accounts for ~80% of the sugar production worldwide. Since sugarcane productivity is severely affected by abiotic stresses and hence, an experiment was conducted for two consecutive years during 2020 and 2021 on popular sub-tropical sugarcane varieties. The experiment was laid out in two-factorial RBD consisting of nine sugarcane genotypes (Co 98014, Co 0118, Co 0238, Co 05011, Co 06034, Co 09022, Co 12029, Co 15023 and Co 15027) and salinity treatments (Control, ECiw ~ 4, 8 and 12 dS m−1) in 5 replications. Two budded setts were planted in pots and irrigated with saline water of respective levels till formative phase and observed the build-up in electrical conductivity of soil extract (ECse) from 0.48 (control) to 2.99, 4.81 and 7.08; while further saline irrigation increased the ECse values to 4.48, 6.24 and 9.33 dS m−1 in treatments ECiw ~ 4, 8 and 12 dS m−1, respectively. Increase in soil EC decreased plant survival by 24.1, 47.0 and 79.6% under continued irrigation of ECiw ~ 4, 8, 12 dS m−1 with respect to control. Continued saline irrigation caused significant reduction in growth, which was associated with reduction in relative water content (RWC) and gas exchange traits. RWC decreased by 4.91 to 21.9%, chlorophyll content by 8.46 to 32.75%, photosynthetic rate (Pn) by 16.85 to 91.44%, stomatal conductance by 14.96 to 84.25%, transpiration rate by 14.13% to 89.8% and chlorophyll fluorescence by 5.33 to 42.67% from ECiw ~ 4 to 12 dS m−1, respectively. Significant variations in Na+ and K+ ion content was observed under elevated saline condition in roots, leaves and juice extract of genotypes. Na+/K+ ratio, an important trait for screening salinity tolerance, increased in all genotypes as compared to control, the increase was predominant in susceptible varieties. Single cane weight (SCW) was drastically affected by saline irrigation, with a reduction of 36.4, 68.5 and 83.5% at ECiw ~ 4, 8 and 12 dS m−1, respectively as compared to control, with similar declining trend in juice quality. Based on our results, Co 0238, Co 0118 and Co 98014 were tolerant to salinity stress by maintaining higher Pn, lower leaf Na+/K+ ratio, higher SCW and higher juice sucrose content.