Well-watered Plants Research Articles

O CO2 elevado induz a regulação negativa da fotossíntese e alivia o efeito do déficit hídrico em Ceiba pentandra (Malvaceae)

ABSTRACT The simultaneous effect of elevated CO2 concentration and drought on trees is still under investigation in the Amazon. We evaluated the effect of CO2 levels (400 and 800 ppm) and water regimes (50% and 100% soil field capacity) on photosynthetic traits, chlorophyll fluorescence, and total biomass accumulation in Ceiba pentandra. In well-watered plants, light-saturated photosynthesis (PN-sat) increased in plants exposed to elevated CO2, but both PN-sat and stomatal conductance decreased in response to water deficit. The maximum carboxylation rate of Rubisco declined under elevated CO2, which indicates down-regulation of photosynthesis at elevated CO2. The Fv/Fm ratio was not affected by treatments. Notwithstanding, total plant biomass and leaf area were reduced by 34-37% under water deficit, but they were not affected by CO2 levels. The PN-sat values measured in well-irrigated plants at ambient CO2 were similar to those observed in plants subjected to elevated CO2 and water deficit (p = 0.26). We concluded that the effect of water deficit on PN-sat was mitigated by elevated CO2. These results suggest that the increase of atmospheric CO2 concentrations associated to climate changes can at least partly offset the negative effect of drought in this multiuse and widely distributed species.

Ectomycorrhizal fungi with hydrophobic mycelia and rhizomorphs dominate in young pine trees surviving experimental drought stress

Mycorrhizal fungi can help plants to cope with drought, but research on the fungal communities that are more resistant to drought or alleviate drought stress of trees is still scarce. In this study, we investigated effects of drought on soil fungal communities and explored potential fungal traits related to drought resistance under greenhouse conditions. We manipulated water availability in pine seedlings belonging to three Spanish Pinus pinaster populations from geographical areas subjected to contrasting summer drought. A set of plant ecophysiological traits were quantified and soil fungi was quantified and profiled using ergosterol and Pacific Biosciences sequencing. Abundance of ectomycorrhizal (ECM) fungi in plants subjected to drought was lower than in well-watered plants. Most ECM taxa in plants surviving drought had long exploration types and were taxa typically forming rhizomorphs and hydrophobic mycelia. By contrast, ECM taxa in well-watered plants had wider range of distinct exploration types. No differences in fungal communities were found among P. pinaster populations. No associations between ECM fungi and plant ecophysiological traits were found, but significant interactions between drought treatments and belowground plant biomass were found for the relative abundances of ECM fungi, particularly ECM with long exploration types. Plants subjected to drought may benefit by associating to ECM taxa previously shown to transport water efficiently.

Deteriorating Harmful Effects of Drought in Cucumber by Spraying Glycinebetaine

In order to alleviate the shortage of irrigation water in dry regions, refining water use efficiency (WUE) is a key issue in sustainable productivity. Furthermore, glycinebetaine (GlyBet) is a vital osmoprotectant produced in crops for improving drought tolerance; however, little is known about its role in improving plant WUE under field conditions in non-accumulating plants such as cucumber. In order to elucidate the effectiveness of GlyBet concentrations (0, 2000, 4000, and 6000 mg/L) in mitigating the deleterious effects of drought (e.g., well-watered (1250 m3/fed), moderate drought (950 m3/fed), and severe drought (650 m3/fed)), field experiments were conducted at Elmia village, Dakahlia, Egypt in the 2020 and 2021 seasons on vegetative growth, some physiological attributes, as well as yield and quality. Drought considerably decreased vegetative growth, yield and its components, leaf relative water content, and photosynthetic pigment concentrations compared with well-watered plants while increasing electrolyte leakage. The most harmful causes were severe drought. However, exogenous spraying with GlyBet substantially boosted the mentioned attributes, but reduced electrolyte leakage within well-watering. Commonly 6000 mg/L contributed to the maximum growth and productivity, preserving cucumber plant water status above other concentrations or untreated plants. Under extreme drought, the application of 6000 mg/L GlyBet had a beneficial effect on moderating the damage of water deficit on cucumber plant growth and productivity. Overall, using GlyBet as a cost-effective and eco-friendly biostimulant six times (10, 20, 30, 40, 50, and 60 days from sowing) has the potential to mitigate drought damage while also increasing yield; however, more research is needed to determine the optimal rate and timing of application.

Functional physiological phenotyping and transcriptome analysis provide new insight into strawberry growth and water consumption.

Global warming is expected to increase agricultural water scarcity; thus, optimized irrigation schedules are important and timely for sustainable crop production. Deficit irrigation, which balances crop growth and water consumption, has been proposed, but the critical threshold is not easily quantified. Here, we conducted experiments on strawberry plants subjecting progressive drought following various water recovery treatments on the high-throughput physiological phenotyping system "Plantarray". The critical soil water contents (θcri), below which the plant transpiration significantly decreased, were calculated from the inflection point of the transpiration rate (Tr) - volumetric soil water content (VWC) curve fitted by a piecewise function. The physiological traits of water relations were compared between the well-watered plants (CK), plants subjecting the treatment of rewatering at the point of θcri following progressive drought (WR_θcri), and the plants subjecting the treatment of rewatering at severe drought following progressive drought (WR_SD). The results showed that midday Tr, daily transpiration (E), and biomass gain of the plants under WR_θcri treatment were equivalent to CK during the whole course of the experiment, but those under WR_SD treatment were significantly lower than CK during the water stress phase that could not recover even after rehydration. To explore the gene regulatory mechanisms, transcriptome analysis of the samples collected 12h before, 12h post and 36h post water recovery in the three treatments was conducted. GO and KEGG enrichment analyses for the differentially expressed genes indicated that genes involved in mineral absorption and flavonoid biosynthesis were among the most striking transcriptionally reversible genes under the WR_θcri treatment. Functional physiological phenotyping and transcriptome data provide new insight into a potential, quantitative, and balanceable water-saving strategy for strawberry irrigation and other agricultural crops.

Seedling-Stage Deficit Irrigation with Nitrogen Application in Three-Year Field Study Provides Guidance for Improving Maize Yield, Water and Nitrogen Use Efficiencies.

Deficit irrigation (DI) was acknowledged as an effective technique to improve water use efficiency (WUE) without significant yield reduction. In this study, a 3-year field experiment was conducted in Northeast China during 2017-2019 to investigate the combined effects of 3-week DI from 3-leaf stage and N fertilization on maize seedling growth and determine the resulting impacts on silking growth and yield formation, N use efficiency (NUE) and WUE. Results showed that seedling-stage DI decreased leaf area and photosynthesis, thus significantly limited shoot and root dry biomass for maize seedling, compared to well-watered (WW) plants. In 2017 and 2019, seedling-stage DI positively improved seedling growth with higher root: shoot ratio and enhanced drought tolerance, under higher initial soil water contents (SWC) with sufficient precipitation before DI. The DI-primed plants showed similar or better performances on reproductive growth, grain yield, WUE and NUE compared to WW plants, even experiencing heavy rainfall or drought stresses around the silking stage. However, the contrasting results were observed in 2018 with negative DI effects on seedling and silking growth and final yield, probably due to less rainfall and lower SWC before DI. In all 3 years, N fertilization had significant compensatory effects on limited seedling growth under DI, and its effect was much less in 2018 than other years due to adverse early climate. The principal component and correlation analysis revealed maize silking growth, grain yield, NUE and WUE were strongly related to the seedling growth as affected by water and N managements under various climatic conditions. In conclusion, a short-term and moderate DI regime-adopted at the seedling stage under higher initial SWC and coupled with an appropriate N fertilization-is beneficial to control redundant vegetative growth while optimizing root development, therefore effectively improving drought tolerance for maize plants and achieving higher grain yield, WUE and NUE.

Long noncoding RNA transcriptome analysis reveals novel lncRNAs in Morus alba 'Yu-711' response to drought stress.

Drought stress has been a key environmental factor affecting plant growth and development. The plant genome is capable of producing long noncoding RNAs (lncRNAs). To better understand white mulberry (Morus alba L.) drought response mechanism, we conducted a comparative transcriptome study comparing two treatments: drought-stressed (EG) and well-watered (CK) plants. A total of 674 differentially expressed lncRNAs (DElncRNAs) were identified. In addition, 782 differentially expressed messenger RNAs (DEmRNAs) were identified. We conducted Gene Ontology (GO) and KEGG enrichment analyses focusing on the differential lncRNAs cis-target genes. The target genes of the DElncRNAs were most significantly involved in the biosynthesis of secondary metabolites. Gene regulatory networks of the target genes involving DElncRNAs-mRNAs-DEmRNAs and DElncRNA-miRNA-DEmRNA were constructed. In the DElncRNAs-DEmRNAs network, 30 DEmRNAs involved in the biosynthesis of secondary metabolites are collocated with 46 DElncRNAs. The interaction between DElncRNAs and candidate genes was identified using LncTar. In summary, quantitative real-time polymerase chain reaction (qRT-PCR) validated nine candidate genes and seven target lncRNAs including those identified by LncTar. We predicted that the DElncRNAs-DEmRNAs might recruit microRNAs (miRNAs) to interact with gene regulatory networks under the drought stress response in mulberry. The findings will contribute to our understanding of the regulatory functions of lncRNAs under drought stress and will shed new light on the mulberry-drought stress interactions.

Common Bean Seeds Obtained by Plant Water Restriction Ameliorates Obesity-Associated Cardiovascular Risk and Insulin Resistance.

The inclusion of beans in the diet has been recommended for obesity control. However, its beneficial effect varies depending on agroclimatic factors acting during plant development. The antiobesogenic capacity of Dalia bean (DB) seeds obtained by water restriction (WR) during the vegetative or reproductive stage of plant growth (50/100 and 100/50% of soil moisture in vegetative/reproductive stage, respectively), during the whole cycle (50/50), and well-watered plants (100/100) was researched. After phytochemical characterization, harvested beans from each experimental unit were pooled among treatments, based on a multivariate canonical discriminant analysis considering concentration of non-digestible carbohydrates (total, soluble and insoluble dietary fiber and resistant starch), phenolic compounds (total phenols, flavonoids, anthocyanins and condensed tannins) and total saponins, which showed no differences among replicas of each treatment. Obesity was induced in rats (UAZ-2015-36851) with a high fat diet (HFD) for fourmonths. Afterwards, rats were fed with the HFD supplemented with 20% of cooked DB for threemonths. During treatment, 100/50 beans, improved blood triglycerides, cholesterol, and glucose, and alleviated early insulin resistance (IR) related to inhibition of lipase, α-amylase and -glucosidase activity. After sacrifice, a hypolipidemic capacity and atherogenic risk reduction was observed, especially from the 100/50 treatment, suggesting that intake of DB obtained from WR may prevent IR and dyslipidemia.

Drought-Induced Responses in Maize under Different Vapor Pressure Deficit Conditions.

Water stress in plants depends on the soil water level and the evaporative demand. In this study, the physiological, biochemical, and molecular response of maize were examined under three evaporative demand conditions (low—1.00 kPa, medium—2.2 kPa, and high—4.00 kPa Vapor pressure deficit (VPD)) at three different soil water content (SWC); well-watered, 45%, and 35% SWC. Plants grown at 35% SWC under high VPD had significant (p < 0.01) lower leaf weight, leaf area, and leaf number than low VPD. Plants under low, medium, and high VPD with drought stress (45% and 35% SWC) showed a 30 to 60% reduction in their leaf area compared to well-watered plants. Gas exchange parameters including photosynthesis, stomatal conductance, and water use efficiency exhibited significant differences (p < 0.01) between treatments, with the highest reduction occuring at 35% SWC and high VPD. Both drought and VPD significantly (p < 0.01) increased C4 enzyme levels and some transcription factors with increased stress levels. Transcription factors primarily related to Abssisic Acid (ABA) synthesis were upregulated under drought, which might be related to high ABA levels. In summary, severe drought levels coupled with high VPD had shown a significant decrease in plant development by modifying enzymes, ABA, and transcription factors.

Transpiration response of palmer amaranth (Amaranthus palmeri) to drying soil in greenhouse conditions

Palmer amaranth (Amaranthus palmeri S. Watson) is a troublesome weed that can result in substantial crop yield loss in irrigated and rainfed agricultural systems of the U.S. Great Plains. Knowledge of the transpiration response to soil drying is necessary to better understand the competitive nature of Palmer amaranth against crops in limiting soil moisture conditions. The objective was to quantify the soil matric potential at which the transpiration rate of Palmer amaranth starts to decline during soil drying conditions. A greenhouse experiment consisting of six replications of well-watered and stressed plants growing in columns of a packed silt loam soil on automated load cells was established in May 2021 in Manhattan, KS. Hourly transpiration rates were computed as the difference of two consecutive mass readings. Stomatal conductance was measured every other day on the topmost fully developed leaf using a leaf porometer. Soil matric potential was estimated using a measured soil water retention curve. The stomatal conductance of plants undergoing soil drying conditions started to decrease at a soil matric potential of -120 kPa and the plant-level transpiration rate started to decrease at -176 kPa. Palmer amaranth exhibited high (246 g h-1) day-time transpiration rates when soil water was available at low tension levels (10 to 33 kPa). In advanced stages of development, well-watered plants also exhibited nighttime transpiration that accounted for ~10% of the day-time transpiration total. Mean transpiration use efficiency of well-watered and stressed plants considering total dry biomass was similar (P = 0.247), with values of 10.9 and 11.6 g kg-1, respectively. Overall, this study substantiates the competitive nature of Palmer amaranth for soil water in sub-humid and semi-arid environments and highlights the importance of early control of Palmer amaranth to minimize competition for soil moisture.

Exogenous Nitric Oxide and Silicon Applications Alleviate Water Stress in Apricots.

Many plants confront several environmental stresses including heat, water stress, drought, salinity and high-metal concentrations that are crucial in defining plant productivity at different stages of their life cycle. Nitric oxide (NO) and Silicon (Si) are very effective molecules related in most of them and in varied biochemical events that have proven to be protective during cellular injury caused by some stress conditions like water stress. In the current work, we studied the effect of Si and NO alone and NO + Si interactive application on the response of plants exposed to water deficiency and well-watered plants for the Milord apricot variety. Water stress caused a reduce in chlorophyll content, dry and fresh weight, leaf area, stomatal conductivity, leaf relative water content and nutrient elements, while it caused an increase in leaf temperature, leaf proline, leaf malondialdehyde (MDA) content and membrane permeability. Si, NO and Si + NO combination treatments under water stress conditions significantly decreased the adverse effects of water stress on leaf temperature, leaf area, dry and fresh weight, stomata conductivity, relative water content, membrane permeability, L-proline and MDA content. The shoot dry weight, chlorophyll content, stomata conductivity and leaf relative water content in Si + NO treated apricot saplings increased by 59%, 55%, 12% and 8%, respectively. Combined treatment (Si + NO) was detected to be more effective than single applications (Si or NO) on some physiological, biochemical, morphological and nutritional properties of apricot under water stress conditions.

Shading Reduces Water Deficits in Strawberry (Fragaria X Ananassa) Plants during Vegetative Growth

ABSTRACT The strawberry (Fragaria × ananassa Duch.) is a commercially important crop with high water requirements, making strategies that mitigate the influence of water deficits on plant growth necessary. This study aimed to evaluate the effects of shading on the vegetative growth of strawberry cv. Sweet Ann under a water deficit. The treatments consisted of the combination of two levels of shading (light intensity reduced by 47% vs. non-shaded plants) and two levels of water availability (water deficit vs. well-watered plants). The water deficit reduced the leaf water potential from −1.52 to −2.21 MPa, and diminished stomatal conductance, net photosynthetic rate (from 9.13 to 2.5 µmol m−2 s−1), maximum quantum efficiency of PSII photochemistry (from 0.79 to 0.67), and biomass accumulation, but increased the electrolyte leakage. The shading allowed the water-deficient plants to maintain water potential (−1.58 MPa) and photosystem II efficiency (0.79) and to increase water use efficiency (from 14.80 to 86.90 µmol CO2/mmol H2O), net photosynthetic rate (from 2.40 to 9.40 µmol m−2 s−1) and biomass of leaves, crowns, and roots, as compared to the non-shaded plants without a water limitation. These results suggest, for the first time in strawberry, that a reduction in incident light intensity attenuates the effects of stomatic and non-stomatic limitations caused by a water deficit during vegetative growth in strawberry.

Integration of high-throughput phenotyping with anatomical traits of leaves to help understanding lettuce acclimation to a changing environment

Main conclusionThe combination of image-based phenotyping with in-depth anatomical analysis allows for a thorough investigation of plant physiological plasticity in acclimation, which is driven by environmental conditions and mediated by anatomical traits.Understanding the ability of plants to respond to fluctuations in environmental conditions is critical to addressing climate change and unlocking the agricultural potential of crops both indoor and in the field. Recent studies have revealed that the degree of eco-physiological acclimation depends on leaf anatomical traits, which show stress-induced alterations during organogenesis. Indeed, it is still a matter of debate whether plant anatomy is the bottleneck for optimal plant physiology or vice versa. Here, we cultivated ‘Salanova’ lettuces in a phenotyping chamber under two different vapor pressure deficits (VPDs; low, high) and watering levels (well-watered, low-watered); then, plants underwent short-term changes in VPD. We aimed to combine high-throughput phenotyping with leaf anatomical analysis to evaluate their capability in detecting the early stress signals in lettuces and to highlight the different degrees of plants’ eco-physiological acclimation to the change in VPD, as influenced by anatomical traits. The results demonstrate that well-watered plants under low VPD developed a morpho-anatomical structure in terms of mesophyll organization, stomatal and vein density, which more efficiently guided the acclimation to sudden changes in environmental conditions and which was not detected by image-based phenotyping alone. Therefore, we emphasized the need to complement high-throughput phenotyping with anatomical trait analysis to unveil crop acclimation mechanisms and predict possible physiological behaviors after sudden environmental fluctuations due to climate changes.

Silicon and Nitric Oxide Applications Allow Mitigation of Water Stress in Myrobalan 29C Rootstocks (Prunus cerasifera Ehrh.)

(1) Background: Silicon (Si) and nitric oxide (NO) have been proven to protect against cellular injury caused by stress conditions, mostly by salinity and water stress in agriculture. (2) Methods: The goal was to study the effect of soil applications of NO, Si, and their combination (Si+NO) on the response of Myrobalan 29C rootstocks (Prunus cerasifera Ehrh.) subjected to water stress and well-watered conditions. (3) Results: The results showed that water stress decreased growth parameters (i.e., leaf area, shoot dry weight, root fresh weight, shoot fresh weight, root dry weight, and relative shoot diameter), physio-biochemical parameters (i.e., chlorophyll and relative water content in leaves), and leaf and root minerals (i.e., P, Ca, Fe, and Zn in leaves and N, K, Ca, and Zn in roots), compared to well-watered plants. Under these conditions, all treatments mitigated the detrimental effects of water stress on Myrobalan 29C rootstocks, being the most effective the Si+NO treatment. (4) Conclusions: These findings briefly highlight that the combination of silicon and nitric oxide may provide greater tolerance to water stress in Myrobalan 29C rootstocks.

Leaf gas exchange and water relations of the woody desiccation-tolerant Paraboea rufescens during dehydration and rehydration.

Desiccation-tolerant (DT) plants can withstand dehydration to less than 0.1 g H2O g−1 dry weight. The mechanism for whole-plant recovery from severe dehydration is still not clear, especially for woody DT plants. In the present study, we evaluated the desiccation tolerance and mechanism of recovery for a potentially new woody resurrection plant Paraboea rufescens (Gesneriaceae). We monitored the leaf water status, leaf gas exchange, chlorophyll fluorescence and root pressure of potted P. rufescens during dehydration and rehydration, and we investigated the water content and chlorophyll fluorescence of P. rufescens leaves in the field during the dry season. After re-watering from a severely dehydrated state, leaf maximum quantum yield of photosystem II of P. rufescens quickly recovered to well-watered levels. Leaf water status and leaf hydraulic conductance quickly recovered to well-watered levels after re-watering, while leaf gas exchange traits also trended to recovery, but at a slower rate. The maximum root pressure in rehydrated P. rufescens was more than twice in well-watered plants. Our study identified P. rufescens as a new DT woody plant. The whole-plant recovery of P. rufescens from extreme dehydration is potentially associated with an increase of root pressure after rehydration. These findings provide insights into the mechanisms of recovery of DT plants from dehydration.

Biochar as a soil amendment in the tree establishment phase: What are the consequences for tree physiology, soil quality and carbon sequestration?

Trees play a pivotal role in the urban environment alleviating the negative impacts of urbanization, and for this reason, local governments have promoted strongly tree planting policies. However, poor soil quality and neglect tree maintenance (e.g., irrigation and fertilization) can seriously mine the plant health status during the tree establishment phase. The use of biochar to provide long-lasting C to the soil and, at the same time, improving soil properties (e.g., improved water holding capacity), soil enzymes activities and NPK concentrations, is a promising research field. Therefore, with a two-step experiment, the study aimed to assay the physiological responses of a commonly used urban tree species (Tilia × europaea L.) to 1.5 % (w/w) biochar amendment (B), and secondly, to assess the ability of trees, grown in biochar amended soil, to tolerate a period of drought. Biochar amendment increased P and K availability in the soil, resulting in higher P and K concentrations in B than control leaves, according to the leaf stage. This induced B trees, higher values in both total biomass than controls (+22 %) in well-watered plants. Moreover, the higher water availability in soil amended with biochar helped B trees to tolerate water stress, with better leaf photosynthetic performances and a faster recovery than stressed controls after the re-watering. This study highlights the dual function of the biochar, improving CO2 sequestration and soil properties, and at the same time, enhancing plant physiological responses to environmental constraints. The use of biochar at the tree planting, especially in an urban environment, is a feasible and environmentally sustainable strategy to improve the success during the tree establishment phase.

Drought-Induced Changes in The Flowering Capacity, Anthesis Quality and Seed Set in Rice (Oryza sativa L.).

Drought stress significantly reduces grain yield (GY) due to poor spikelet fertility and anthesis quality. Aim of this study was to understand the changes of flowering capacity, anthesis quality traits and seed set in the re-watered drought stressed modern high yielding drought susceptible rice cultivar, IR64 at heading (DSH) and booting (DSB) stages. The well-watered plants served as control of the experiment. Results obtained suggest that spikelet moisture content at above 80% was required to maintain optimum anthesis process in rice. Anthesis process in DSH plant was suspended when leaf relative water content (LRWC) dropped to below than 70%. Effects of drought stress on the spikelet moisture were irreversible as compared to the leaf rolling and LRWC. Hence, seed set was failed to occur at the upper rachis branches of the DSH plant. Anthesis process in the re-watered drought stress plants was resumed on the third day after re-watering with about 50% and 80% of anthers managed to dehisce in the DSH and DSB plants. Consequently, percentage of spikelet fertility and seed set in the DSH and DSB plants were increased towards the lower parts of the panicle. The GY, number of seeds, spikelet fertility, and harvest index however were significantly lower in the DSH plant (0.30 g, 13, 16.40% and 14.81) as compared to DSB plant (1.34 g, 57, 59.14% and 48.30), respectively. In addition, all interrelated traits involved in the flowering process of rice could be collectively termed as the anthesis quality traits due to their significant correlation with the grain yield and other yield components.

Genome-wide identification, in silico characterization and expression analysis of the RNA helicase gene family in chickpea (C. arietinum L.)

The RNA helicases are an important class of enzymes which are known to influence almost every aspect of RNA metabolism. The majority of RNA helicases belong to the SF2 (superfamily 2) superfamily, members of which are further categorized into three separate subfamilies i.e., the DEAD, DEAH and DExD/H-box subfamilies. In chickpea, these RNA helicases have not been characterized until now. A genome-wide analysis across the chickpea genome led to the identification of a total of 150 RNA helicase genes which included 50 DEAD, 33 DEAH and 67 DExD/H-box genes. These were distributed across all the eight chromosomes, with highest number on chromosome 4 (26) and least on chromosome 8 (8). Gene duplication analysis resulted in identification of 15 paralogous gene pairs with Ka/Ks values < 1, indicating towards the genes being under purifying selection during the course of evolution. The promoter regions of the RNA helicase genes were enriched in cis-acting elements like the light and ABA-responsive elements. The drought responsiveness of the genes was analysed by studying the expression profiles of few of these genes, in two different genotypes, the cultivated variety ICC 8261 (kabuli, C. arietinum) and the wild accession ILWC 292 (C. reticulatum), through qRT-PCR. These genotypes were selected based on their drought responsiveness in a field experiment, where it was observed that the percentage (%) reduction in relative water content (RWC) and membrane stability index (MSI) for the drought stressed plants after withholding water for 24 days, over the control or well-watered plants, was least for both the genotypes. The genes CaDEAD50 and CaDExD/H66 were identified as drought-responsive RNA helicase genes in chickpea. The protein encoded by the CaDExD/H66 gene shares a high degree of homology with one of the CLSY (CLASSY) proteins of A. thaliana. We hypothesize that this gene could possibly be involved in regulation of DNA methylation levels in chickpea by regulating siRNA production, in conjunction with other proteins like the Argonaute, RNA dependent RNA polymerases and Dicer-like proteins.

The arbuscular mycorrhizal fungus Rhizophagus clarus improves physiological tolerance to drought stress in soybean plants

Soybean (Glycine max L.) is an economically important crop, and is cultivated worldwide, although increasingly long periods of drought have reduced the productivity of this plant. Research has shown that inoculation with arbuscular mycorrhizal fungi (AMF) provides a potential alternative strategy for the mitigation of drought stress. In the present study, we measured the physiological and morphological performance of two soybean cultivars in symbiosis with Rhizophagus clarus that were subjected to drought stress (DS). The soybean cultivars Anta82 and Desafio were grown in pots inoculated with R. clarus. Drought stress was imposed at the V3 development stage and maintained for 7 days. A control group, with well-irrigated plants and no AMF, was established simultaneously in the greenhouse. The mycorrhizal colonization rate, and the physiological, morphological, and nutritional traits of the plants were recorded at days 3 and 7 after drought stress conditions were implemented. The Anta82 cultivar presented the highest percentage of AMF colonization, and N and K in the leaves, whereas the DS group of the Desafio cultivar had the highest water potential and water use efficiency, and the DS + AMF group had thermal dissipation that permitted higher values of Fv/Fm, A, and plant height. The results of the principal components analysis demonstrated that both cultivars inoculated with AMF performed similarly under DS to the well-watered plants. These findings indicate that AMF permitted the plant to reduce the impairment of growth and physiological traits caused by drought conditions.

Evaluation of the concentration-response relationship between film antitranspirant and yield of rapeseed (Brassica napus L.) under drought

Drought can cause large yield losses of rapeseed (Brassica napus L.), particularly during the flowering stage. Effective methods of crop management are required to improve the resistance to drought. Film antitranspirants (AT), as an effective method of crop management, can reduce water loss by forming a waterproof layer to block stomata mechanically. In our study, three pot experiments were conducted in the glasshouse at Harper Adams University in 2019–2020 to investigate the effect of two levels of irrigation - well-watered (WW) and water-stressed (WS); and AT at five concentrations - 0 (water), 0.25%, 0.5%, 0.75% and 1% at flowering stage on spring rapeseed. Results showed that water stress during the flowering stage depressed gas exchange significantly. Seed dry weight per plant reduced by an average of 70%, compared to WW control. Following AT application, stomatal conductance and photosynthesis rate were linearly associated with the concentration of AT for WW and WS plants in two of three experiments. With increasing AT concentrations, stomatal conductance was predicted to decrease ~1.4fold faster than photosynthesis rate. Some yield components showed an increase by AT application, however, the compensatory trade-off between pod number and seed number per pod accounted for the lack of a significant improvement in seed yield from AT-treated plants. Our results indicate that application of AT at flowering stage may be a potential method of mitigating the drought damage to rapeseed by blocking stomata, thereby sustaining seed yield. As AT-induced restrictions on leaf gas exchange are related to the concentrations, higher concentrations of film AT than those tested may be needed in future studies.

Response of two riparian woody plants to Phytophthora species and drought

Disease combined with drought poses an important threat to plant survival, often compromising success in the restoration of riparian forests. Thus, understanding how biotic and abiotic stressors may affect plant survival and growth performance can greatly increase the success of ecosystem management strategies. The purpose of this study was to understand how two plant species, often used together in restoration of riparian ecosystems but with different ecological preferences, would respond to infection by each of two Phytophthora species in Mediterranean-climate regions, in the absence or presence of a simulated drought. Saplings of the drought resistant species Frangula californica, and of the riparian species Alnus rhombifolia were each inoculated in a greenhouse experiment with one of two Phytophthora species and exposed to two watering regimes. Saplings were allocated to six treatments, combining three levels of pathogen inoculation (no inoculation, inoculation with Phytophthora cactorum and inoculation with Phytophthora crassamura), and two watering regimes (well-watered and drought). The response of A. rhombifolia and F. californica saplings was assessed through the observation of health metrics and morphological parameters. Results showed that both P. cactorum and P. crassamura are important pathogens of A. rhombifolia and F. californica. As expected, drought conditions were the main cause of decline and mortality in A. rhombifolia saplings, while water availability was a facilitator of P. cactorum infection in F. californica saplings. We observed two seemingly contrasting results in A. rhombifolia saplings: infection by Phytophthora spp. decreased survival in well-watered plants, while the opposite was recorded for saplings under drought conditions whose survival increased in Phytophthora-inoculated treatments. Saplings of F. californica were able to cope with drought conditions, even when infected by Phytophthora species and water availability increased root infection and decreased sapling survival. We conclude that the continued use of F. californica and A. rhombifolia in sites infested by Phytophthora species can be beneficial in restoration, if appropriate management actions are adopted. Such actions include avoiding the planting of F. californica saplings in areas subjected to water accumulation, and ensuring that A. rhombifolia is planted in areas where drought stress is minimal and where Phytophthora species are possibly absent. We also emphasize the importance of ensuring that plant stock used in revegetation projects is not infected by Phytophthora species, and that biotic and abiotic risks are assessed prior to restoration actions.