Lower Relative Water Content Research Articles

MicroRNA164 Affects Plant Responses to UV Radiation in Perennial Ryegrass.

Increasing the ultraviolet radiation (UV) level, particularly UV-B due to damage to the stratospheric ozone layer by human activities, has huge negative effects on plant and animal metabolism. As a widely grown cool-season forage grass and turfgrass in the world, perennial ryegrass (Lolium perenne) is UV-B-sensitive. To study the effects of miR164, a highly conserved microRNA in plants, on perennial ryegrass under UV stress, both OsmiR164a overexpression (OE164) and target mimicry (MIM164) transgenic perennial ryegrass plants were generated using agrobacterium-mediated transformation, and UV-B treatment (~600 μw cm-2) of 7 days was imposed. Morphological and physiological analysis showed that the miR164 gene affected perennial ryegrass UV tolerance negatively, demonstrated by the more scorching leaves, higher leaf electrolyte leakage, and lower relative water content in OE164 than the WT and MIM164 plants after UV stress. The increased UV sensitivity could be partially due to the reduction in antioxidative capacity and the accumulation of anthocyanins. This study indicated the potential of targeting miR164 and/or its targeted genes for the genetic manipulation of UV responses in forage grasses/turfgrasses; further research to reveal the molecular mechanism underlying how miR164 affects plant UV responses is needed.

Physiological and biochemical response analysis of Styrax tonkinensis seedlings to waterlogging stress

Climate change is increasing flooding in provinces of the south of the Yangtze River, posing challenges for promoting Styrax tonkinensis seedlings in these areas. To understand the physiological reasons for this species' intolerance to waterlogging, we observed biochemical parameters in one-year-old S. tonkinensis seedlings during two seasons. For 4 and 12 days in summer and winter experiments, respectively, we subjected seedlings to a pot-in-pot waterlogging treatment. Control groups were established at 0 h and 0 days. We examined indicators related to root vigor, reactive oxygen species (ROS), antioxidant enzymes, fermentative pathways, and more. The results displayed that decreased abscisic acid accumulation in roots inhibited water transport. Increased dehydrogenase and lactate dehydrogenase activity in roots promoted alcohol and lactate fermentation, causing toxic damage and reduced root vigor, impeding water absorption. In leaves, high ROS levels led to lipid peroxidation, exacerbating water loss from continuous transpiration. The high relative electric conductivity and low leaf relative water content indicated water loss, causing leaf wilting and shriveling. Conversely, winter seedlings, devoid of leaves, significantly reduced transpiration, and dormancy delayed root fermentation. With less ROS damage in roots, winter seedlings exhibited greater waterlogging tolerance. In summary, excessive water loss from leaves and inhibited vertical water transport contributed to low summer survival rates, while winter leafless dormancy and reduced ROS damage enhanced tolerance. Our findings provide insights for enhancing waterlogging resistance in S. tonkinensis amidst climate change challenges.

Morpho-physiological Alteration of Mangifera indica L. in Response to Sea Water Induced Salt Stress

Salinity is one of the biggest challenges in the southern part of Bangladesh, which is affecting the coastal ecosystem adversely. A pot experiment was conducted to find out the morpho-physiological changes in mango (Mangifera indica L.) seedlings in response to sea water induced salt stress at the Agroforestry and Environment research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU). The experiment was laid out in a Randomized Complete Block Design (RCBD) with five replications, where four treatments, viz 4, 8, 12 dS m-1 salinity level (prepared from sea water), and the tap water (control) were imposed. The results indicated that plant height of mango shortened with the higher level of salinity and the declining magnitude was 28.44% over control at maximum salinity level. Number of leaves per plant of mango were reduced by 27.51% at 12 dS m-1 salinity level compared to that tap water, and the size of mango leaf was also reduced for salinity. Both shoot and root biomass of mango seedlings were significantly reduced due to salinity. The Salt tolerance index in mango was 56.76 only at 12 dS m-1. In case of physiological parameters, the lowest relative water content (RWC) was found in 12 dS m-1, while water saturation deficit (WSD) and water uptake capacity (WUC) were found to be the lowest in control for this plant. Water saturation deficit and water uptake capacity were increased with the increment of salinity level. Total chlorophyll and carotenoid content of mango were decreased by 66.27% and 61.07%, respectively, at the highest salinity level. Proline content of mango increased by 73.07% at 12 dS m-1 salt level in comparison to that of seawater devoid control plants. Considering the overall results, it can be concluded that, although mango seedlings were significantly affected by high salinity (12 dS m-1), but can survive up to moderate salinity (8 dS m-1) at sapling stage.

TaWRKY31, a novel WRKY transcription factor in wheat, participates in regulation of plant drought stress tolerance

BackgroundWheat, a crucial food crop in China, is highly vulnerable to drought stress throughout its growth and development. WRKY transcription factors (TFs), being one of the largest families of TFs, play a vital role in responding to various abiotic stresses in plants.ResultsHere, we cloned and characterized the TF TaWRKY31 isolated from wheat. This TF, belonging to the WRKY II family, contains a WRKYGQK amino acid sequence and a C2H2-type zinc finger structure. TaWRKY31 exhibits tissue-specific expression and demonstrates responsiveness to abiotic stresses in wheat. TaWRKY31 protein is localized in the nucleus and can function as a TF with transcription activating activity at the N-terminus. Results showed that the wheat plants with silenced strains (BSMV:TaWRKY31-1as and BSMV:TaWRKY31-2as) exhibited poor growth status and low relative water content when subjected to drought treatment. Moreover, the levels of O2·−, H2O2, and malondialdehyde (MDA) in the BSMV:TaWRKY31-induced wheat plants increased, while the activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) decreased. Compared to control plants, BSMV:TaWRKY31-induced wheat plants exhibited lower expression levels of TaSOD (Fe), TaPOD, TaCAT, TaDREB1, TaP5CS, TaNCED1, TaSnRK2, TaPP2C, and TaPYL5.Under stress or drought treatment conditions, the overexpression of TaWRKY31 in Arabidopsis resulted in decreased levels of H2O2 and MDA, as well as reduced stomatal opening and water loss. Furthermore, an increase in resistance oxidase activity, germination rate, and root length in the TaWRKY31 transgenic Arabidopsis was observed. Lastly, overexpression of TaWRKY31 in Arabidopsis resulted in higher the expression levels of AtNCED3, AtABA2, AtSnRK2.2, AtABI1, AtABF3, AtP5CS1, AtSOD (Cu/Zn), AtPOD, AtCAT, AtRD29A, AtRD29B, and AtDREB2A than in control plants.ConclusionsOur findings indicate that TaWRKY31 enhances drought resistance in plants by promoting the scavenging of reactive oxygen species, reducing stomatal opening, and increasing the expression levels of stress-related genes.

MsCYP71 is a positive regulator for drought resistance in alfalfa

Cytochrome P450 (CYP450) family proteins play key roles in plant growth, development, stress responses, and other physiological processes. Here, we cloned the cytochrome P450 gene MsCYP71 in alfalfa and found that the expression of MsCYP71 was induced by drought stress. Silencing the MsCYP71 gene using virus-induced gene silencing technology significantly decreased the drought resistance of alfalfa, as indicated by their lower relative water content, net photosynthetic rate, and chlorophyll fluorescence maximum (Fm); further, the heterologous overexpression of MsCYP71 in tobacco significantly enhanced the drought resistance and Fm of transgenic tobacco. Furthermore, the expression of MsCYP71 across 45 alfalfa accessions under drought stress was investigated. A significant positive correlation between drought resistance and MsCYP71 expression was observed. The 45 alfalfa accessions were clustered into four groups, and drought resistance, Fm, and MsCYP71 were higher in group I than in the other groups, indicating that group I accessions can be used as candidate germplasm resources for the breeding of drought-resistant alfalfa varieties. Overall, our findings indicated that MsCYP71 is a positive regulator of drought resistance in alfalfa, and its expression can be used to evaluate the drought resistance of alfalfa.

Six tree species physiological responses to air pollution in Pulogadung Industrial Estate, East Jakarta, Indonesia and Universitas Indonesia Campus, Depok, Indonesia

<span>Air pollution is a global issue that has a harmful impact on living things and the environment. It is commonly recognized that bioremediation, including the use of tree plants, helps reduce air pollution. Tree plants can respond physically to air pollution. The value of the air pollution tolerance index (APTI) can be used to determine the physiological response. Based on APTI values, this study seeks to determine the tolerance levels and physiological response differences of six tree plant species (<em>Mangifera indica, Pterocarpus indicus</em>, <em>Cerbera odollam</em>, <em>Pometia pinnata</em>, <em>Syzygium myrtifolium</em>, and <em>Swietenia macrophylla</em>) in Pulogadung Industrial Estate, East Jakarta and Universitas Indonesia (UI) Campus, Depok. Environmental factors and APTI values with relative water content parameters, leaf extract pH, ascorbic acid content, and total chlorophyll content were measured in six kinds of tree plants at both research sites. The maximum APTI score in the Pulogadung Industrial Estate was 9.79 0.13, indicating that <em>Mangifera indica</em> plants are air pollution tolerant. Meanwhile, <em>Pterocarpus indicus </em>is classified as sensitive to air pollution, with the lowest APTI score of 6.59 0.18 at the UI Campus, Depok. The APTI test results revealed that tolerant species had high relative water content (RWC) values and ascorbic acid concentration, whereas sensitive species had low RWC values and poor total chlorophyll content.</span>

Oxygenation alleviates waterlogging-caused damages to cherry rootstocks

Waterlogging has occurred more frequently in recent years due to climate change, so it is a huge threat to crop yield and quality. Sweet cherry, a fruit tree with a high economic value, is sensitive to waterlogging stress. One of the most effective methods for enhancing the waterlogging tolerance of sweet cherries is to select waterlogging-tolerant rootstocks. However, the waterlogging tolerance of different cherry rootstocks, and the underlying mechanism remains uncharacterized. Thus, we first evaluated the waterlogging resistance of five sweet cherry rootstocks planted in China. The data showed that ‘Gisela 12’ and ‘Colt’ were the most waterlogging-sensitive and -tolerant among the five tested varieties, respectively. Oxygenation effectively alleviated the adverse impacts of waterlogging stress on cherry rootstocks. Moreover, we found that the waterlogging group had lower relative water content, Fv/Fm value, net photosynthetic rate, and higher antioxidant enzyme activities, whereas the oxygenated group performed better in all these parameters. RNA-Seq analysis revealed that numerous DEGs were involved in energy production, antioxidant metabolism, hormone metabolism pathways, and stress-related transcription factors. These findings will help provide management strategies to enhance the waterlogging tolerance of cherry rootstocks and thereby achieve higher yield and better quality of cherries.Graphical

Morpho-physiological and biochemical attributes as tools to screen tolerance and susceptible rice cultivars for drought stress

Present research work was aimed to observe possible changes in the metabolism of rice plants (Oryza sativa L.) through drought stress. Rice belongs to the family Poaceae. It is considered as a vital food crop across all the major countries worldwide. Rice is prone to be affected by drought stress. Therefore, developing the drought tolerant cultivars of cereal crops assumed considerable importance. This work was carried out with an objective to study the Screening of rice cultivars against water stress and compare biochemical characteristic among different drought tolerant and sensitive rice cultivars. A set of 25 cultivars of rice were screened against drought stress at vegetative stage through various morpho-physiological characters such as moisture, relative water content (RWC), membrane stability index(MSI), membrane injury(MI), seedling length and seedling weight. The RWC is a best criterion for plant water status. The osmotic adjustment is a influential mechanism of conserving cellular hydration under water stress and RWC expression also affects osmotic adjustment in this respect. Thus, it can be considered that the higher RWC having cv. GAR-13 and NWGR-16026 were tolerant and lower RWC having cv. NWGR-16009 and NWGR-16019 were susceptible. Hence, cv. GAR-13 & NWGR-16026 was used as tolerant and NWGR-16009 & NWGR-16019 were used as susceptible. On the basis of first experiment total four cultivars (Two tolerant NWGR-16026 & GAR-13, two susceptible NWGR-16009 & NWGR-16019) were selected for various biochemical analysis. The results indicated that total soluble sugars (TSS), glycine betaine and ascorbic acid content were found significantly higher in cultivar NWGR-16026. The proline content was found significantly higher in cultivar GAR-13. So, RWC and some biochemical parameters are best indicators for selection regarded as potentially useful for drought tolerant rice cultivars and targets for development through transgenic approaches.

Eco-Physiological Behavior of Five Tunisian Olive Tree Cultivars under Drought Stress

Tunisia is known to be a country with poor water resources, and water scarcity is evident in certain regions. In the long term, this situation could worsen, given the increased risk of drought. The olive tree (Olea europaea L.) is one of the plants best adapted to this climate, and numerous studies have been carried out to assess the effects of water stress. The aim of this work was to study and compare the ecophysiological behavior of a main Tunisian olive cultivar (Chetoui) and four rare Tunisian olive cultivars (Chemchali, Besbessi, Sayali and Jarboui) under drought stress and to identify the main parameters while comparing the tolerance of the cultivars studied to this abiotic stress. One-year-old olive trees grown in pots in a greenhouse were subjected to four drought treatments (i.e., 15, 30, 45 and 60 days of drought stress) in comparison with control trees. The evaluation of the response of the olives to this induced stress was based on five parameters: relative water content (RWC), stomatal resistance (SR), photosystem PSII, maximal photochemical efficiency (FV/FM), performance index on absorption basis (PI), measured by the handy PEA, and chlorophyll index, measured by SPAD. The relative water content (RWC) of the five cultivars decreased with increasing drought stress. Jarboui showed lower RWC values than Chemchali, especially under severe drought stress. This result was confirmed by changes in fluorescence characteristics. FV/FM, PI and SPAD index decreased during the development of drought stress. These observations are discussed in relation to the strategies developed by the cultivars to grow under drought stress. The Principal Component Analysis allowed the parameter with the strongest loading factor, which is FV/FM, to be highlighted and the cultivars most tolerant to drought stress to be distinguished. These cultivars, Besbessi and Sayali in the north of Tunisia and Chemchali in the south, can present a possible alternative to replace the local or foreign cultivars most cultivated in the country, which are characterized by high water needs.

Cyclopia subternata growth, yield, proline and relative water content in response to water deficit stress

Cyclopia, generally known as honeybush, and belonging to the Fabaceae family, originates from the Cape Floristic Region of the Eastern Cape and Western Cape provinces of South Africa. Currently, 6 honeybush species are commercially cultivated but, to date, there have been limited trials attempting to study their agronomic water demand. A pot trial was conducted where Cyclopia subternata plants were cultivated on different soil types (Stellenbosch granite, Stellenbosch shale and Stellenbosch clovelly) and subjected to three different water-deficit stress levels (well-watered, semi-stressed and stressed). Remarkably, irrigation treatments and soil types did not significantly affect the growth of the plants. However, the well-watered treatment consistently had higher yields compared to the other two treatments. The water-stressed (semi-stressed and stressed) treatments had lower relative water contents (RWC) with higher concentrations of proline, which signify water stress, compared to the control treatment. Higher proline and lower RWC contents found in this study are indications of water stress.

Transcriptome and anatomical studies reveal alterations in leaf thickness under long-term drought stress in tobacco

Drought is one of the foremost environmental factors that limit the growth of plants. Leaf thickness (LT) is an important quantitative trait in plant physiology. The experiment was carried out in a growth room and the plants were divided into two groups such as well-watered and drought-stressed. This work investigated leaf growth in terms of leaf surface growth and expansion rate, leaf stomata traits, LT, anticlinal growth, and leaf cell layers. The results showed that the leaf area and leaf surface expansion rate were decreased by drought stress (DS). Similarly, LT, anticlinal expansion rate, palisade and spongy tissue thickness, and their related expansion rates were also decreased at different days’ time points (DTP) of DS. However, a steady increase was observed in the aforementioned parameters after 12 DTP of DS. The stomatal density increased while stomata size decreased at 3 DTP and 12 DTP (low leaf water potential and relative leaf water content at these time points) and vice versa at 24 DTP compared with the well-watered plants indicating adaptations in these traits in response to DS, and thus the leaf water status played a role in the regulation of leaf stomata traits. The cell length decreased in the upper epidermis, palisade and spongy tissues by DS up to 12 DTP led to lower LT while an increase was observed after 12 DTP that resulted in higher LT. The increase in the LT was supported by the upregulation of starch and sucrose metabolism, glycerolipid metabolism, protein processing in endoplasmic reticulum pathways at 18 DTP along with the differentially expressed genes induced that were related to cell wall remodeling (cellulose, expansin, xyloglucans) and cell expansion (auxin response factors and aquaporin). The results explain the response of leaf thickness to drought stress and show alterations in LT and leaf stomatal traits. This study might serve as a valuable source of gene information for functional studies and provide a theoretical basis to understand leaf growth in terms of leaf anatomy and leaf stomatal traits under drought stress.

Evaluation of maize germplasm for physio-morphological traits against fall armyworm

The fall armyworm (FAW), scientific name Spodoptera frugiperda (J.E. Smith), poses a significant challenge to farmers and agricultural systems due to its ability to adapt, reproduce rapidly, and develop resistance to pesticides. Hence, it is essential to adopt effective and feasible approaches to managing FAW. The present research aimed at identifying the physio-morphological traits in 22 diverse maize genotypes that influence resistance to FAW. Among the tested ones, moderately resistant genotypes had the highest trichome density (CML 71, CML 67, and CML 335), minimum leaf area, and leaf width (DMRE 63, CML 71, and CML 67). Moderately resistant genotypes, viz., CML 67 (0.14 mm), CML 71 (0.14 mm), CML 561 (0.14 mm), and DMRE 63 (0.14 mm), exhibited significantly higher leaf toughness. Furthermore, the lowest relative water content was recorded in moderately resistant genotypes (DMRE 63, CML 71, and CML 67). The maximum cob length was observed in the moderately resistant genotype, CML 71 (18.56 cm), followed by CML 67 (18.26 cm), which was on par. Among moderately resistant genotypes, CML 71 had the greatest cob width of 4.97 cm, followed by CML 67 (4.88 cm), CML 561 (4.66 cm), CML 335 (4.66 cm), and DMRE 63 (4.62 cm), and these were statistically comparable. Of the genotypes evaluated, the moderately resistant genotypes CML 71, CML 67, and DMRE 63 registered significantly higher yields of 135.04 g/plant, 120.65 g/plant, and 117.92 g/plant, respectively. This information on physio-morphological traits is helpful in breeding programs focusing on maize resistance to FAW.

Plant water‐use strategies as mediators of herbivore drought response: Ecophysiology, host plant quality and functional traits

Abstract The response of herbivorous insects to plant drought stress can range from positive to negative, and it has been challenging to understand the causes of this variation. We tested whether plant trait values associated with aridity gradients might underlie this variation and how such effects vary between two insect feeding guilds. Here, we propose that plants trait values associated with adaptation to arid environments would result in positive effects of experimental drought on herbivores, with such plant species adaptively shifting resources away from resistance to maintain performance under stress. In contrast, plants with trait values associated with adaptation to mesic environments would result in negative effects of drought because such species lose vigour and thus decrease their host quality. We tested these predictions using experimental manipulations in 13 milkweed species (genus Asclepias) adapted to a wide range of environmental conditions and the herbivore performance of a specialist leaf‐chewer (monarch butterfly; Danaus plexippus) and sap‐feeder (oleander aphid; Aphis nerii). We exposed plants to physiologically calibrated species‐specific watering regimes to maximize (100%) or reduce (50%) stomatal conductance and then monitored herbivore performance. The effects of drought stress on herbivore survival ranged from strongly positive (50% increase) to strongly negative (80% decrease) among milkweed species, but these effects were inconsistent between the two herbivores. Plant trait values associated with adaptation to aridity were correlated with monarch survival in the predicted manner, such that milkweed species with high water‐use efficiency (WUE) and low relative water content (RWC) increased monarch survival under drought. In contrast, aphid survival was unrelated to arid‐adapted trait values. Drought‐induced changes in plant quality were negatively associated with both herbivore survivals. Specifically, milkweed species that increased cardenolides concentration under drought conditions decreased monarch and aphid survival. Synthesis. We demonstrated that the indirect effects of drought on herbivores varied tremendously among closely related plant species and between co‐occurring insect herbivores. We in turn present evidence that some of this variation is explained by plant traits associated with adaptation to arid versus mesic environments for leaf‐chewers but not sap‐feeders and that such effects are mediated by drought‐induced changes in chemical defences.

On the path from xylem hydraulic failure to downstream cell death.

Xylem hydraulic failure (HF) has been identified as a ubiquitous factor in triggering drought-induced tree mortality through the damage induced by the progressive dehydration of plant living cells. However, fundamental evidence of the mechanistic link connecting xylem HF to cell death has not been identified yet. The main aim of this study was to evaluate, at the leaf level, the relationship between loss of hydraulic function due to cavitation and cell death under drought conditions and discern how this relationship varied across species with contrasting resistances to cavitation. Drought was induced by withholding water from potted seedlings, and their leaves were sampled to measure their relative water content (RWC) and cell mortality. Vulnerability curves to cavitation at the leaf level were constructed for each species. An increment in cavitation events occurrence precedes the onset of cell mortality. A variation in cells tolerance to dehydration was observed along with the resistance to cavitation. Overall, our results indicate that the onset of cellular mortality occurs at lower RWC than the one for cavitation indicating the role of cavitation in triggering cellular death. They also evidenced a critical RWC for cellular death varying across species with different cavitation resistance.

Water Stress Identification of Winter Wheat Crop with State-of-the-Art AI Techniques and High-Resolution Thermal-RGB Imagery

Timely crop water stress detection can help precision irrigation management and minimize yield loss. A two-year study was conducted on non-invasive winter wheat water stress monitoring using state-of-the-art computer vision and thermal-RGB imagery inputs. Field treatment plots were irrigated using two irrigation systems (flood and sprinkler) at four rates (100, 75, 50, and 25% of crop evapotranspiration [ETc]). A total of 3200 images under different treatments were captured at critical growth stages, that is, 20, 35, 70, 95, and 108 days after sowing using a custom-developed thermal-RGB imaging system. Crop and soil response measurements of canopy temperature (Tc), relative water content (RWC), soil moisture content (SMC), and relative humidity (RH) were significantly affected by the irrigation treatments showing the lowest Tc (22.5 ± 2 °C), and highest RWC (90%) and SMC (25.7 ± 2.2%) for 100% ETc, and highest Tc (28 ± 3 °C), and lowest RWC (74%) and SMC (20.5 ± 3.1%) for 25% ETc. The RGB and thermal imagery were then used as inputs to feature-extraction-based deep learning models (AlexNet, GoogLeNet, Inception V3, MobileNet V2, ResNet50) while, RWC, SMC, Tc, and RH were the inputs to function-approximation models (Artificial Neural Network (ANN), Kernel Nearest Neighbor (KNN), Logistic Regression (LR), Support Vector Machine (SVM) and Long Short-Term Memory (DL-LSTM)) to classify stressed/non-stressed crops. Among the feature extraction-based models, ResNet50 outperformed other models showing a discriminant accuracy of 96.9% with RGB and 98.4% with thermal imagery inputs. Overall, classification accuracy was higher for thermal imagery compared to RGB imagery inputs. The DL-LSTM had the highest discriminant accuracy of 96.7% and less error among the function approximation-based models for classifying stress/non-stress. The study suggests that computer vision coupled with thermal-RGB imagery can be instrumental in high-throughput mitigation and management of crop water stress.

Shade tolerance response of legumes in terms of biomass accumulation, leaf photosynthesis, and chlorophyll pigment under reduced sunlight

AbstractLegumes have a distinct morpho‐physiological response to reduced sunlight, but their capacity to adapt to the levels of shading due to intercropping systems is not sufficiently understood. Such adaptation to shade—60% of full sun in terms of physiological attributes—was examined in cowpea (Vigna unguiculata Savi), lablab (Lablab purpureus Adans.), lima bean (Phaseolus lunatus), pigeonpea [Cajanus cajan (L.) Millsp.], and pole bean (Phaseolus vulgaris). Although the capacity of photosynthetic machinery decreased under shade, the capacity continued to exceed the actual rate of photosynthesis. Compared with those under full sun, leaves under shade were thinner (specific weight only 56% of that under full sun), larger (surface area greater by 54.7%), and recorded a 15% higher leaves/stem ratio (by weight) and a 25.6% higher leaves/total dry weight ratio. However, the concentration of chlorophyll pigments per unit weight and per unit surface area was significantly higher in leaves under shade. Water stress was probably higher for leaves under full sun given the higher canopy temperatures and lower relative water content. At final biomass harvest, across the species shading has reduced the biomass 32% in 2009 and 34.6% in 2010 over unshade. Biomass was greater in lima bean (413 g m−2), and pigeonpea (408 g m−2) then lowest in lablab (180 g m−2) and cowpea (216 g m−2). Of the five legumes tested, lablab and cowpea showed the greatest tolerance to shade and therefore are better suited to the low‐light environment of intercropping.

Seed priming upregulates antioxidant defense and glyoxalase systems to conferring simulated drought tolerance in wheat seedlings

This experiment was conducted to understand the protective effect of different priming agents [50 µM salicylic acid (SA), 4 mM ascorbic acid (AsA), and 2.5 mM NaCl] under simulated drought [15% (m/v) polyethylene glycol (PEG-6000)] in wheat. Drought caused higher proline accumulation, lower relative water content, chlorosis, and growth inhibition. Enhanced levels of the malondialdehyde and hydrogen peroxide were evident with higher reactive oxygen species (ROS) generation that disrupted the plant antioxidant defense system. The activities of antioxidant enzymes were also significantly declined under PEG-induced drought stress. Drought also increased methylglyoxal (MG) formation, which aggravated oxidative damage to the next folds. However, priming wheat seeds with SA, AsA and NaCl decreased ROS production by decreasing AsA, increasing glutathione content, and upregulating the antioxidant defense system. Additionally, increased activities of glyoxalase system enzymes (glyoxalase I and glyoxalase II) controlled the overproduction of MG in drought-stressed wheat seedlings. Indeed, seed priming helps to alleviate drought-induced oxidative damage by modulating the antioxidant defense system. However, AsA provided a better defense to plants against drought stress. Therefore, it can be concluded that priming wheat seeds with SA, AsA, and NaCl confers drought stress tolerance by upregulating antioxidant defense and glyoxalase systems, thus ensuring better seedling establishment.

Genome-wide identification of plasma-membrane intrinsic proteins in pumpkin and functional characterization of CmoPIP1-4 under salinity stress

Plasma membrane intrinsic proteins ( PIPs ) play a crucial role in the salinity and drought tolerance of plants. PIPs operate as vital water conduits for regulating water homeostasis during salt stress. Pumpkin is an important Cucurbitaceae crop, and no research on PIPs in pumpkin has been carried out. The current study, presents the first genome-wide characterization of the PIP gene family and functional characterization of CmoPIP1–4 with knockout mutants in pumpkin. According to their phylogeny, 21 CmoPIP genes have been identified and divided into 2 subgroups: CmoPIP1s and CmoPIP2s . Functional studies on their NPA motifs, ar/R filter, and Froger's positions predicted that these CmoPIP proteins would be substrate specific. The CmoPIP1s expression was found to be responsive to salt stress in leaves and roots. CmoPIP1–4 plays an important role in the salt stress tolerance of pumpkin, and the overexpression of CmoPIP1–4 confers salinity tolerance to yeast. However, hyper sensitivity to salt was observed in CmoPIP1–4 CRISPR plants phenotypically (weaker health, lower relative water contents and reduced photosynthetic activities), physiologically (higher Na + /K + ratios, malondialdehyde, ROS and membrane stability index, lower the contents of proline, glycine betaine and also decreased antioxidative enzyme activities), and molecularly (lower expression levels of salt-associated genes CmoSOS1 , CmoHKT1;1 , CmoNHX4 , and a lower expression levels antioxidative genes CmoSOD1/2, CmoPOD1/2 and CmoCAT1/2 ). This study highlights that CmoPIP1–4 is a key player in the stress-signaling pathway in pumpkin plants and could be valuable for developing stress-resistant cucurbit crops in the future. • Twenty-one plasma membrane intrinsic proteins ( PIPs ) were genome-wide characterized in Cucurbita moschata . • Salinity stress decreases the expression of most CmoPIPs . • Overexpression of CmoPIP1-4 conferred salt tolerance in yeast. • A salt-sensitive phenotype was observed after the CmoPIP1-4 knockout in pumpkin roots.

Interspecific differences in desiccation tolerance of selected Antarctic lichens: Analysis of photosystem II effectivity and quenching mechanisms

Lichens can survive and cope with unsufficient water supply resulting in low intrathalline relative water content. Under such conditions, photosynthesis is negatively affected by different degree of dehydration. In our study, fully hydrated samples of Xanthoria elegans, Umbilicaria decussata and Usnea aurantiaco-atra were light-acclimated and during following desiccation from a fully hydrated to dry state, steady-state chlorophyll fluorescence (FS), effective quantum yield of photochemical processes in PSII (ФPSII), and nonphotochemical quenching (qN) were measured in response to decreasing relative water content (RWC). The three experimental lichen species showed a high desiccation tolerance. The desiccation-induced decrease in ФPSII was found in X. elegans, U. decussata and U. aurantiaco-atra, at the RWC values below 30%. This is well comparable to the evidence reached in other Arctic / Antarctic lichen species. Interspecific differences in desiccation tolerance of these selected Antarctic lichens, based on the analysis of photosystem II effectivity and quenching mechanisms, were described and discussed.

NAC Transcription Factor TwNAC01 Positively Regulates Drought Stress Responses in Arabidopsis and Triticale.

The NAC transcription factors play important roles in regulating plant growth, development, and senescence, and responding to biotic and abiotic stressors in plants. A novel coding sequence (1,059 bp) was cloned from hexaploid triticale in this study. The putative protein (352 amino acids) encoded by this sequence was over 95% similar to the amino acid sequence of a NAC protein from Aegilops tauschii (XP020161331), and it formed a clade with Ae. tauschii, durum wheat, and barley. The putative protein contained a conserved nature actomyosin (NAM) domain (129 consecutive amino acids) between the 20th and 148th amino acids at the N-terminus and three transcription activation regions at the C-terminus. The novel gene was identified as a triticale NAC gene localized in the nucleus and designated as TwNAC01 (GenBank accession MG736919). The expression levels of TwNAC01 were the highest in roots, followed by leaves and stems when triticale lines were exposed to drought, polyethylene glycol 6,000 (PEG6000), NaCl, cold, methyl jasmonate (MeJA), and abscisic acid (ABA). Transgenic Arabidopsis thaliana overexpressing TwNAC01 had significantly lower leaf water loss rates and longer roots than wild-type (WT) A. thaliana. Virus-induced silencing of the TwNAC01 gene in triticale delayed root development and decreased length of primary root. Under drought stress, leaves of TwNAC01-silenced triticale had higher levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2), but lower relative water content (RWC), net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate than the leaves of the WT. Gene overexpression and silencing experiments suggested that TwNAC01 improves plant stress tolerance by increasing root length, regulating the water content of plant leaves by reducing MDA and H2O2 content, and adjusting respiration rate. The results suggest that TwNAC01 is a novel NAC transcription factor gene that can be exploited for triticale and cereal improvement.