Reduced Transpiration Rate Research Articles

Knock-out of SlDMR6-1 in tomato promotes a drought-avoidance strategy and increases tolerance to Late Blight

The DOWNY MILDEW RESISTANCE 6 (DMR6) protein is a 2-oxoglutarate (2OG) and Fe(II)-dependent oxygenase, involved in salicylic acid (SA) metabolism. SA is recognized as an abiotic stress-tolerance enhancer, and in tomato the inactivation of DMR6 was found increase its level and induce disease-resistance against several pathogens. By applying the CRISPR/Cas9 technique, we generated Sldmr6-1 tomato mutants and tested their tolerance to drought as well as to Late Blight. Wild-type tomato cultivar ‘San Marzano’ and its Sldmr6-1 mutants were subjected to water deprivation for 7 days. WT plants exhibited severe wilting, while T2Sldmr6-1 mutants showed turgid leaves and maintained higher Soil Relative Water Content. Eco-physiological measurements highlighted that Sldmr6-1 mutants adopted a water saving behavior reducing transpiration rate by decreasing stomatal conductance. Under drought stress the assimilation rate decreased as well, resulting in no alteration of the CO2 concentration in the sub-stomatal chamber and increasing the Water Use Efficiency. Furthermore, in Sldmr6-1 mutants the drought stress induced up-regulation of the anti-oxidant related genes SlAPX and SlGST as well as down-regulation of SlCYP707A2 gene, which is involved in ABA catabolism. At last we highlighted, for the first time in tomato, that Sldmr6-1 mutants exhibited a reduced susceptibility to Phytophthora infestans, the causal agent of Late Blight.

Synergistic effect of seaweed extract and boric acid and/or calcium chloride on productivity and physico-chemical properties of Valencia orange.

Many citrus species and cultivars are grown successfully in tropical and subtropical countries, as well as in arid and semi-arid regions with low levels of organic matter and low cation exchange, resulting in lower nutrient uptake by the plant. The essential nutrients needed for citrus flowering and fruit set are limited in winter due to a reduction in transpiration rate, negatively effecting vegetative growth, flowering, yield, and fruit quality. The present investigation was carried out to assess the nutritional status, fruit yield parameters, and fruit quality of Valencia orange trees after foliar spraying of seaweed extract (SW) combined with calcium chloride and boric acid and their combinations in the 2020/2021 and 2021/2022 seasons. The treatments were arranged in a split-plot design (three levels spraying seaweed extract × four levels spraying calcium chloride and boric acid and their combinations × four replicates × one tree/replicate). The results indicated that all of the characteristics measured, including leaf chlorophyll, leaf mineral contents, fruit yield parameters, fruit physical properties, and fruit chemical properties, were significantly affected by the foliar spraying of seaweed extract (SW) combined with calcium chloride and boric acid and their combinations. Although all treatments increased the productivity and the physical and chemical properties of Valencia orange fruits compared to the control, a treatment of 10 g/L SW combined with 0.5 g/L boric acid and 1 g/L calcium chloride produced superior results. This ratio of SW, boric acid, and calcium chloride is therefore recommended to enhance productivity and improve the physico-chemical properties of Valencia orange for greater fruit yield.

High-nitrogen fertilizer alleviated adverse effects of drought stress on the growth and photosynthetic characteristics of Hosta ‘Guacamole’

BackgroundSeveral plants are facing drought stress due to climate change in recent years. In this study, we aimed to explore the effect of varying watering frequency on the growth and photosynthetic characteristics of Hosta ‘Guacamole’. Moreover, we investigated the effect of high-nitrogen and -potassium fertilizers on alleviating the impacts of drought stress on the morphology, photosynthetic characteristics, chlorophyll fluorescence, fast chlorophyll a fluorescence transient, JIP-test parameters, and enzymatic and non-enzymatic scavenging system for reactive oxygen species (ROS) in this species.ResultsLeaf senescence, decreased chlorophyll contents, limited leaf area, and reduced photosynthetic characteristics and oxygen-evolving complex (OEC) activity were observed in Hosta ‘Guacamole’ under drought stress. However, high-nitrogen fertilizer (30-10-10) could efficiently alleviate and prevent the adverse effects of drought stress. High-nitrogen fertilizer significantly increased chlorophyll contents, which was higher by 106% than drought stress. Additionally, high-nitrogen fertilizer significantly improved net photosynthetic rate and water use efficiency, which were higher by 467% and 2900% than those under drought stress. It attributes that high-nitrogen fertilizer could reduce transpiration rate of leaf cells and stomatal opening size in drought stress. On the other hand, high-nitrogen fertilizer enhanced actual photochemical efficiency of PS II and photochemical quenching coefficient, and actual photochemical efficiency of PS II significantly higher by 177% than that under drought stress. Furthermore, high-nitrogen fertilizer significantly activated OEC and ascorbate peroxidase activities, and enhanced the performance of photosystem II and photosynthetic capacity compared with high-potassium fertilizers (15-10-30).ConclusionsHigh-nitrogen fertilizer (30-10-10) could efficiently alleviate the adverse effects of drought stress in Hosta ‘Guacamole’ via enhancing OEC activity and photosynthetic performance and stimulating enzymatic ROS scavenging system.

CfCHLM, from Cryptomeria fortunei, Promotes Chlorophyll Synthesis and Improves Tolerance to Abiotic Stresses in Transgenic Arabidopsis thaliana

Mg-protoporphyrin IX methyltransferase (CHLM) is essential for the synthesis of chlorophyll (chl). However, no CHLM gene has been reported in Chinese cedar (Cryptomeria fortunei). Here, we cloned the CHLM gene from C. fortunei, and the full-length CfCHLM sequence was 1609 bp, with a 1077 bp ORF region encoding a protein 358 amino acids long. A homologous comparison analysis showed that CfCHLM was highly evolutionarily conserved among different plant species. A phylogenetic tree was drawn using CHLM proteins from ten angiosperms and three gymnosperms, and CfCHLM was found to be most closely related to the TcCHLM protein of Chinese yew (Taxus chinensis). The CfCHLM is located in chloroplasts and does not exhibit self-activation. The expression of CfCHLM was highest in the needles and was downregulated under abiotic stress, i.e., cold, heat, drought, or salt stress. Under cold, heat, drought, and salt abiotic stresses, CfCHLM transgenic A. thaliana showed higher chl fluorescence parameters, elevated chl levels, increased net photosynthetic rate (Pn), and enhanced antioxidant enzyme activities. Conversely, it showed a lower stomatal conductance (Gs), a reduced transpiration rate (Tr), and decreased malondialdehyde (MDA) levels compared to the wild type (WT). In summary, the CfCHLM gene augments chloroplast function, photosynthetic capacity, and stress resistance in plants. This study provides a reference for future research on the growth and development of C. fortunei.

Screening cotton genotypes for their drought tolerance ability based on the expression level of dehydration-responsive element-binding protein and proline biosynthesis-related genes and morpho-physio-biochemical responses.

Drought stress adversely affects growth, development, productivity, and fiber quality of cotton (Gossypium hirsutum L). Breeding strategies to enhance drought tolerance require an improved knowledge of plant drought responses necessitating proper identification of drought-tolerant genotypes of crops, including cotton. The objective of this study was to classify the selected cotton genotypes for their drought tolerance ability based on morpho-physio-biochemical traits using Hierarchical Ward's cluster analysis. Five genotypes of cotton (Takfa 3, Takfa 6, Takfa 7, Takfa 84-4, and Takfa 86-5) were selected as plant materials, and were grown under well-watered (WW; 98 ± 2% field capacity) and water-deficit (WD; 50 ± 2% field capacity) conditions for 16days during the flower initiation stage. Data on morpho-physio-biochemical parameters and gene expression levels for these parameters were collected, and subsequently genotypes were classified either as a drought tolerant or drought susceptible one. Upregulation of GhPRP (proline-rich protein), GhP5CS (Δ1-pyrroline-5-carboxylate synthetase), and GhP5CR (Δ1-pyrroline-5-carboxylate reductase) in relation to free proline enrichment was observed in Takfa 3 genotype under WD condition. An accumulation of free proline, total soluble sugar, and potassium in plants under WD conditions was detected, which played a key role as major osmolytes controlling cellular osmotic potential. Magnesium and calcium concentrations were also enriched in leaves under WD conditions, functioning as essential elements and regulating photosynthetic abilities. Leaf greenness, net photosynthetic rate, stomatal conductance, and transpiration rate were also declined under WD conditions, leading to growth retardation, especially aboveground traits of Takfa 6, Takfa 7, Takfa 84-4, and Takfa 86-5 genotypes. An increase in leaf temperature (1.1 - 4.0°C) and crop water stress index (CWSI > 0.75) in relation to stomatal closure and reduced transpiration rate was recorded in cotton genotypes under WD conditions compared with WW conditions. Based on the increase of free proline, soluble sugar, leaf temperature, and CWSI, as well as the decrease of aboveground growth traits and physiological attributes, five genotypes were categorized into two cluster groups: drought tolerant (Takfa 3) and drought susceptible (Takfa 6, Takfa 7, Takfa 84-4, and Takfa 86-5). The identified drought-tolerant cotton genotype, namely, Takfa 3, may be grown in areas experiencing drought conditions. It is recommended to further validate the yield traits of Takfa 3 under rainfed field conditions in drought-prone environments.

In situ short-term responses of Amazonian understory plants to elevated CO2.

The response of plants to increasing atmospheric CO2 depends on the ecological context where the plants are found. Several experiments with elevated CO2 (eCO2) have been done worldwide, but the Amazonian forest understory has been neglected. As the central Amazon is limited by light and phosphorus, understanding how understory responds to eCO2 is important for foreseeing how the forest will function in the future. In the understory of a natural forest in the Central Amazon, we installed four open-top chambers as control replicates and another four under eCO2 (+250 ppm above ambient levels). Under eCO2, we observed increases in carbon assimilation rate (67%), maximum electron transport rate (19%), quantum yield (56%), and water use efficiency (78%). We also detected an increase in leaf area (51%) and stem diameter increment (65%). Central Amazon understory responded positively to eCO2 by increasing their ability to capture and use light and the extra primary productivity was allocated to supporting more leaf and conducting tissues. The increment in leaf area while maintaining transpiration rates suggests that the understory will increase its contribution to evapotranspiration. Therefore, this forest might be less resistant in the future to extreme drought, as no reduction in transpiration rates were detected.

Effects of elevation on growth, photosynthetic and Ni-accumulation responses in Bornmuellera emarginata (Brassicaeae)

Bornmuellera emarginata is a Balkan Ni-hyperaccumulator indicated as a promising candidate for agromining practices. Here, two elevation-contrasting accessions (250 m, Low Elevation plants LE, and at 1600 m, High Elevation plants, HE) were compared in terms of growth, photosynthetic activity, and Ni accumulation in controlled conditions to assess possible differences exploitable in practical applications. After two months of pot cultivation on garden and serpentine soil, plant biomass, gas exchanges and Ni concentrations were evaluated. A hydroponic trial with increasing NiSO4 concentration was performed to evaluate Ni tolerance and accumulation.Plants grown on serpentine soil showed reduced biomass as compared to those from garden soil, without any difference between LE and HE. In both accessions, growth in serpentine soil resulted in photochemical/biochemical limitations and reduction in stomatal conductance, especially in LE. HE showed low stomatal conductance in all the conditions, despite a greater stomatal density. Shoot Ni accumulation was higher in HE (∼1600 µg Ni g−1 d.w. and 1200 µg Ni g−1 d.w. in HE and LE respectively), thus resulting in a significantly higher metal content per plant in respect to LE (∼120 and ∼85 µg plant−1 in HE and LE respectively). In hydroponics, HE possessed higher Ni tolerance and accumulation in respect to LE.In conclusion underlying the higher shoot metal amount of HE, Ni tolerance seemed to play a pivotal role, overtaking possible negative effects of reduced transpiration rates compared to LE. Our results point to the opportunity of exploring and exploiting the variation in accumulation level among B. emarginata accessions for the implementation of environmental restoration and metal cropping practices.

The effects of increasing salinity levels on Sulla carnosa photosynthesis are mainly of stomatal nature

Sulla carnosa Desf. plants were subjected to 0, 100, 200, and 300 mM NaCl for 40 days. Leaf and stem growth as well as root and leaf water contents were not affected even at 300 mM NaCl, confirming the halophytic nature of this species. An accumulation of Na+ in roots and at a higher magnitude in leaves together with a decline in K+ concentrations suggest that Na+ involvement in osmotic adjustment as a cheap osmoticum. This typical halophytic response together with the reduced transpiration rate by stomata closure may explain the ability of S. carnosa to maintain its water status. Interestingly, the stomatal limitations of photosynthetic activity did not affect Fv/Fm, F0, and PSII energy distribution to photochemical process [Y(II)], regulated non-photochemical quenching [Y(NPQ)], and non- regulated non-photochemical quenching [Y(NO)], which suggests a high ability of this halophyte to cope with the energy expected to exceed the demand for its photosynthesis.

Effect of ethylene pretreatment on tomato plant responses to salt, drought, and waterlogging stress.

Salinity, drought, and waterlogging are common environmental stresses that negatively impact plant growth, development, and productivity. One of the responses to abiotic stresses is the production of the phytohormone ethylene, which induces different coping mechanisms that help plants resist or tolerate stress. In this study, we investigated if an ethylene pretreatment can aid plants in activating stress-coping responses prior to the onset of salt, drought, and waterlogging stress. Therefore, we measured real-time transpiration and CO2 assimilation rates and the impact on biomass during and after 3days of abiotic stress. Our results showed that an ethylene pretreatment of 1ppm for 4h did not significantly influence the negative effects of waterlogging stress, while plants were more sensitive to salt stress as reflected by enhanced water losses due to a higher transpiration rate. However, when exposed to drought stress, an ethylene pretreatment resulted in reduced transpiration rates, reducing water loss during drought stress. Overall, our findings indicate that pretreating tomato plants with ethylene can potentially regulate their responses during the forthcoming stress period, but optimization of the ethylene pre-treatment duration, timing, and dose is needed. Furthermore, it remains tested if the effect is related to the stress duration and severity and whether an ethylene pretreatment has a net positive or negative effect on plant vigor during stress recovery. Further investigations are needed to elucidate the mode of action of how ethylene priming impacts subsequent stress responses.

Ion uptake and distribution in sweet potato genotypes subjected to salt stress is not driven by transpiration

AbstractPotassium is taken up actively by the plant, whereas sodium is often either competing for the same uptake mechanisms or uptake and distribution are driven by the transpirational volume flow in the shoots of plants grown under salinity. Reducing transpiration rate is regarded as an adaptation mechanism to reduce leaf tissue salt load. In combination with a high K uptake, plants may be able to maintain growth and are, thus, seen as salt‐tolerant. Little is known about these mechanisms in sweet potato (Ipomoea batatas L.). Therefore, cuttings of two sweet potato genotypes contrasting in salinity tolerance (CIP 188002.1, tolerant; CIP 189151.8, sensitive) were subjected to 0 and 50 mM NaCl root zone salinity in a hydroponic system and grown under low (0.76 kPa) and high (2.27 kPa) vapour pressure deficit (VPD) to create differences in transpiration. After 18 days of initial hydroponic growth, NaCl was added for another 33 days. Cumulative plant water loss and total uptake of Na, K and Cl were determined for all plants and treatments. Transpirational water loss was twice as high under high VPD as compared to low VPD conditions, but genotypic Na and Cl accumulation remained almost the same. In contrast to plants subjected to salt stress under low VPD conditions, genotypes under high VPD conditions differed significantly in transpiration. However, in both genotypes transpirational water loss from individual leaves and Na or Cl accumulation were not correlated, under high VPD younger leaves of CIP 188002.1 (tolerant) accumulated more than twice as much potassium than in CIP 189151.8 (sensitive). The distribution of the three ions across leaf positions and within one leaf position between petiole and leaf blade differed strongly between the two genotypes. Tolerant CIP 188002.1 accumulated up to five times more sodium and potassium in the leaf petioles in the middle‐aged and young leaf positions than in the leaf blade, whereas in sensitive CIP 189151.8 neither ion was preferentially accumulated in the petioles. This was independent of salinity treatment and VPD conditions. In contrast, hyperaccumulation of Cl in petioles only occurred under high VPD conditions in the petioles of the tolerant genotype, but not under low VPD conditions, indicating a VPD sensitivity for Cl distribution in sweet potato. While we conclude that transpirational volume flow is not a main driving force for Na and Cl uptake and distribution within the plant, we discuss potential pathways leading to the hyperaccumulation of sodium and potassium in the leaf petioles of the tolerant genotype. We suggest studies on HKT transporter activities in the petioles as an object of further studies in sweet potato.

Toxicity, physiological, and morphological alterations of Indian camphorweed (Pluchea indica) in response to excess copper.

Indian camphorweed (Pluchea indica (L.) Less.) is used as herbal tea due to the presence of volatile aromatic oils and several phytochemical compounds. The aim of this study was to assess the impact of copper (Cu) contamination on the physiology and morphology of P. indica, and the health risks associated with its consumption as tea. The cuttings of P. indica were subjected to 0mM (control), 5mM (low Cu), and 20mM (excess Cu) of CuSO4 treatments for 1, 2, and 4weeks. Thereafter, Cu contamination as well as physiological and morphological parameters were assessed. Cu accumulation was higher in the root tissues of plants (25.8 folds higher as compared to the leaves) grown under 20mM CuSO4 for 4weeks. This increased Cu accumulation resulted in the inhibition of root length, root fresh weight, and root dry weight. Cu concentration was found maximum (1.36μgg-1 DW) in the leaf tissues under 20mM Cu exposure for 4weeks, with the highest target hazard quotient (THQ = 1.85), whereas Cu was not detected in control. Under exposure to 20mM Cu treatment for 4weeks, leaf greenness, maximum quantum yield of photosystem II, and photon yield of photosystem II diminished by 21.4%, 16.1%, and 22.4%, respectively, as compared to the control. Leaf temperature was increased by 2.5°C, and the crop stress index (CSI) exceeded 0.6 when exposed to 20mM Cu treatment for 2 and 4weeks; however, the control had a CSI below 0.5. This led to a reduced transpiration rate and stomatal conductance. In addition, the net photosynthetic rate was also found sensitive to Cu treatment, which resulted in decreased shoot and root growth. Based on the key results, it can be suggested that P. indica herbal tea derived from the foliage of plants grown under a 5mM Cu level (0.75μgg-1 DW) with a target hazard quotient below one aligns with the recommended dietary intake of Cu in leafy vegetables. The study recommends choosing cuttings from plants with a small canopy as plant material in the greenhouse microclimates to validate the growth performance in the Cu-contaminated soil and simulate the natural shrub architecture and life cycle.

Drip fertilization improve water and nitrogen use efficiency by optimizing root and shoot traits of winter wheat.

Proper irrigation and fertilization measures can not only improve water and fertilizer utilization efficiency, but also have important significance in ensuring agricultural environment security and sustainable development. A field experiment was conducted to determine the optimal drip fertilization measure of winter wheat and explain its mechanism by analyzing the physiological and ecological characteristics and utilization efficiency of water and nitrogen under different irrigation and fertilization methods. The plants were treated with three irrigation and fertilization methods: the traditional irrigation and fertilization method (CK), surface drip fertilization (I1) and underground drip fertilization (I2). The results demonstrated that different irrigation methods had various effects on population and physiological characteristics of wheat. The plant height, leaf area and tiller number of I1 were significantly higher than those of CK during the whole growth period. I2 decreased plant height, leaf area and tiller number at jointing stage, but at flowering stage, the leaf area of I2 t was significantly higher than that of CK. Different irrigation methods also affected the root distribution of wheat. At flowering stage, I1 had lower root biomass than CK in all soil layers. The upper root system of I2 was smaller, but the deep root system was larger compared with the control. I1 and I2 had lower total root weight and higher shoot biomass compared to CK, so their root-shoot ratio decreased significantly. I1 and I2 increased and instantaneous water use efficiency (IWUE) by increasing the photosynthetic rate (Pn) and reducing transpiration rate (Tr) at the flowering stage, while I2 had a similar Pn to I1, but reduced Tr, resulting in a higher IWUE than I1. Both I1 and I2 also increased root efficiency, root activity, and Fv/Fm of wheat at the late growth stage, promoting accumulated dry matter after flowering (ADM) and pre-flowering dry matter remobilization (DMR), leading to a significant increase in grain yield. In addition, I1 and I2 had significantly higher water productivity (WP), irrigation water productivity (IWP), nitrogen partial productivity (NPP) and nitrogen agronomic efficiency (NAE) than CK, especially I2 had the highest IWP, WP, NPP and NAE. These findings highlight the potential benefits of drip fertilization in promoting sustainable wheat production and elucidate the mechanism by which it promotes efficient use of water and fertilizer.

Influences of calcium silicate fertilization to physiological and bio-active responses of maize under drought and well-watered conditions

A pot experiment was conducted to investigate the effects of silicon (Si) on morpho-physiological and bio-chemical traits of maize under different irrigation regimes. Experimental treatments comprised of irrigations [60% and 100% of field capacity (FC)], treatments (0, 50, 100, 150, 200 mg kg−1 CaO4Si) and growing stages (GS) [7th (first) and 14th (second) days of water restriction]. 150 mg kg−1 Si increased the growth of maize by inducing transpiration rate (67.56%), water use efficiency (138.36%) and seedling length (19.83%) at first GS whilst enhanced carotenoids (10.95%), total phenolic compounds (45.04%) and decreased proline (7.87%) at the second GS of 60% treatment. In addition, 200 mg kg−1 Si elevated photosynthesis rate (40.54%), total antioxidant activity (12.69%) and decreased proline (52.77%) at the first GS while increased total anthocyanin content (14.99%) during the second GS of 60% application. Silicon had positive impacts on maize under full irrigation conditions too such that 150 mg kg−1 Si reduced transpiration rate (48.43%) and induced total antioxidant activity (39.95%) at first GS while 200 mg kg−1 Si increased water use efficiency by 144.30% at the second GS. In conclusion Si increased drought resistance due to increasing application doses, and on contrary of the literature, Si positively affected many characters at well-watered environment.

Silicon Uptake Mechanism and its Multidimensional Influences on Stress Mitigation in Rice (Oryza sativa L.)

Silicon (Si) is the second most abundant element in the earth crust constituting 27.7 per cent. The beneficial effects of Si includes mitigation of various forms of abiotic and biotic stresses. Rice (Oryza sativa), a typical Si accumulator, takes up Si actively in the form of silicic acid. There are three transporters involved in the uptake of Si viz, LSi1, LSi2 and LSi3. Influx transporter (LSi1) takes up silicic acid from soil solution and mediates its transport upto the exodermal layer of root system, followed by the efflux transporter (LSi2), which transports it across the aerenchyma. Further movement of Si to the aerial parts of the plant is mediated by another influx transporter, LSi6 and finally gets deposited as silica in the plant parts. Silicon present in soil solution as well as its deposition in plants helps in mitigating various stresses in rice. Si application during drought stress prevents compression of xylem vessels and thereby resulting in reduction of transpiration rate. Sufficient supply of Si stabilises the culms and serves to decrease the risk of lodging. Rice is sensitive to metal toxicities like Iron (Fe), Manganese (Mn) and Aluminium (Al). Si complexation with these metal ions decreases their translocation rate and reduces the toxic effects. Heavy metal toxicity due to accumulation of cadmium (Cd) and arsenic (As) can be alleviated through supplementation of Si. Si also ameliorates salt stress by decreasing Na uptake and its root-to-shoot translocation. Silicon deposition in plant parts provides a mechanical barrier against pathogens and pests. The plants supplied with Si produce phenolics and phytoalexins in response to fungal infection and cuticle-Si double layer act as a defence mechanism preventing pests. The key mechanisms of Si-mediated alleviation of stresses in rice include stimulation of antioxidants, complexation of toxic metal ions with Si, immobilization of toxic metal ions and compartmentation of metal ions within plants.

Exogenous Appliance of Nano-Zeolite and Nano-Silicon Elevate Solidago canadensis Invasive Plant Tolerance to Water Deficiency

Plant production, soil quality, and a sustainable environment depend on climate change. Drought is a multidimensional stressor that seriously affects plant production. The most sensitive plant to climate change is the invasive goldenrod (Solidago canadensis L.), which has potentially high-value materials that can be used to develop a novel approach to controlling its spread. This study aimed to evaluate the impact of different applications (NPK-chemical fertilizers (T1) as control, nano-silicon (T2), nano-NPK (T3), nano-zeolite-loaded nitrogen (T4), and mixed nano-silicon with nano-zeolite-loaded nitrogen (T5)) on plant growth, flowering, chemical composition, yield, essential oil (EO) productivity, and tolerance of water deficit under newreclaimed soil. The results show that T5 application enhanced morphological traits and photosynthetic parameters (photosynthetic rate, CO2 concentration, and water use efficiency while reducing transpiration rate) in goldenrod plants. Moreover, it promoted the plant nutrients uptake compared to the control. The highest total carbohydrate, flavonoid, and phenol contents, as well as a significant amount of the phytohormone indole-3-acetic acid (IAA), were obtained from the T5 application. Conversely, abscisic acid (ABA) and antioxidant enzymes of catalase (CAT) and superoxide dismutase (SOD) appeared with the highest amounts in control plants (T1).Th interaction effect of T5 and drought stress is indicated by increased EO productivity and therapeutic properties.Previous results provide a way to elevate drought stress resistance for the safety production of S. canadensis and improve their qualitative and quantitative trials as economical solutions to achieve an environmental approach to control their spread.

Enhancing Rubisco gene expression and metabolites accumulation for better plant growth in Ficus deltoidea under drought stress using hydrogen peroxide.

Growth improvement of the medicinal plant, Ficus deltoidea (Mas Cotek) under drought conditions is a vital issue in Malaysia since it is a slow-growing plant and disposed to leaf damage under the stresses of drought. Therefore, investigation was done to examine the outcomes of hydrogen peroxide (H2O2) application on Rubisco gene expression and metabolites accumulation of stressed F. deltoidea plants, and thereby to record the changes in leaf histology, photosynthesis, biochemical properties, and the growth of the plant. H2O2 at the rates of 0, 5, 10, 15, and 20 mM were foliar sprayed biweekly on the drought stressed plants using a hand sprayer. The application of 20 mM H2O2 amplified leaf number, tallness, stomatal conductance, and photosynthetic yield by 143, 24, 88, and 18%, respectively, over the control plant. A reduced transpiration rate and improved chlorophyll fluorescence were also noted in H2O2-treated plants. The treatment produced a greater amount of chlorophyll a, total phenols, total flavonoids, sugar content, and antioxidant activities by 1.61-, 1.30-, 1.98-, 1.92-, and 1.53-fold, respectively. Application of 15 mM H2O2 enhanced net photosynthetic rate and internal CO2 concentrations by 1.05- and 1.25-fold, respectively. Additionally, H2O2 treatments promoted stomatal closure, increased stomata size, the number of stomata, improved vein structure, and reduced the damage of the leaf margin and mesophyll cells of drought stressed plants. The application of H2O2 also accumulated significantly higher contents of sodium (Na+), calcium (Ca2+), potassium (K+), magnesium (Mg+), and iron (Fe2+) in stressed plants. Although the amount of Arsenic (As+) and Antimony (Sb3+) increased to some extent, the increases were not at a toxic level. The use of H2O2 enhanced the Rubisco gene expression to a greater level and the ratio of Rubisco expression increased up to 16-fold. Finally, thirteen (13) identified and five (5) unmatched volatile compounds with a quality score above 70% were identified by gas chromatography-mass spectrometry (GCMS). The GCMS analysis showed that the foliar application of H2O2 accumulates a higher percentage of volatile components in plants which helps to mitigate the negative effects of drought stress. It is concluded that under drought stressed conditions the F. deltoidea plants should be treated with 10–15 mM of H2O2 twice a week to improve leaf histology, photosynthesis, the level of Rubisco gene expression and volatile compounds accumulation, and plant growth and development.

Physiological and transcriptome analyses reveal the photosynthetic response to drought stress in drought-sensitive (Fengjiao) and drought-tolerant (Hanjiao) Zanthoxylum bungeanum cultivars.

As an important economical plant, Zanthoxylum bungeanum is widely cultivated in arid and semi-arid areas. The studies associated with photosynthesis under drought stress were widely carried out, but not yet in Z. bungeanum. Here, the photosynthesis of two Z. bungeanum cultivars (FJ, Z. bungeanum cv. “Fengjiao”; HJ, Z. bungeanum cv. “Hanjiao”) was analyzed under drought stress using physiological indicators and transcriptome data. Drought decreased stomatal aperture and stomatal conductance (Gsw), reduced transpiration rate (E) and sub-stomatal CO2 concentration (Ci), and lowered chlorophyll and carotenoid content, which reduced the net photosynthetic rate (Pn) of Z. bungeanum. The higher photosynthetic rate in HJ stemmed from its higher chlorophyll content, larger stomatal aperture and Gsw, and higher Ci. Weighted gene co-expression network analysis (WGCNA) identified several ABA signal transduction genes (PYL4, PYL9, and PYR1), LCH-encoding genes (LHCB4.3), and chlorophyll metabolism genes (CRD1, PORA, and CHLH). Additionally, seven transcription factor genes were identified as important factors regulating photosynthesis under drought conditions. In general, a photosynthetic response model under drought stress was built firstly in Z. bungeanum, and the key genes involved in photosynthesis under drought stress were identified. Therefore, the results in our research provide important information for photosynthesis under drought and provided key clues for future molecular breeding in Z. bungeanum.

Ethanol treatment enhances drought stress avoidance in cassava (Manihot esculenta Crantz).

External application of ethanol enhances tolerance to high salinity, drought, and heat stress in various plant species. However, the effects of ethanol application on increased drought tolerance in woody plants, such as the tropical crop "cassava," remain unknown. In the present study, we analyzed the morphological, physiological, and molecular responses of cassava plants subjected to ethanol pretreatment and subsequent drought stress treatment. Ethanol pretreatment induced a slight accumulation of abscisic acid (ABA) and stomatal closure, resulting in a reduced transpiration rate, higher water content in the leaves during drought stress treatment and the starch accumulation in leaves. Transcriptomic analysis revealed that ethanol pretreatment upregulated the expression of ABA signaling-related genes, such as PP2Cs and AITRs, andstress response and protein-folding-related genes, such as heat shock proteins (HSPs). In addition, the upregulation of drought-inducible genes during drought treatment was delayed in ethanol-pretreated plants compared with that in water-pretreated control plants. These results suggest that ethanol pretreatment induces stomatal closure through activation of the ABA signaling pathway, protein folding-related response by activating the HSP/chaperone network and the changes in sugar and starch metabolism, resulting in increased drought avoidance in plants.

Leaf water potential-dependent leaflet closure contributes to legume leaves cool down and drought avoidance under diurnal drought stress.

Efficient thermoregulation under diurnal drought stress protects leaves from photosystem damage and water supply-demand imbalance, yet the cool effect and drought avoidance by leaflet closure have not been well understood. We investigated the cool effect and the drought avoidance of leaflet closure in legume species that survived in the semi-arid region facing seasonal and diurnal drought stress. The results showed that leaflet closure effectively cooled down legume leaves through a reduction of projected leaflet area and the cosine of the angle of incidence (cos i). The leaflet closure was strongly dependent on leaf water potential (Ψleaf). In addition, by characterizing the sequence of key leaf drought response traits, we found leaflet closure occurred after stomatal closure and reduced transpiration rate but before hydraulic failure and turgor loss point (Ψtlp). The meta-analysis also showed that the leaflet closure and cos i decreased after the stomatal conductance declined but before midday. These results imply that Ψleaf-dependent leaflet closure as an alternative to transpiration for leaflet cooling down and as a protective drought avoidance strategy assisting sessile legume plants survival under drought stress.

Analysis of Physiological Status in Response to Water Deficit of Spelt (Triticum aestivum ssp. spelta) Cultivars in Reference to Common Wheat (Triticum aestivum ssp. vulgare)

Climate change, including decreasing rainfall, makes cultivating cereals more difficult. Drought stress reduces plant growth and most all yields. On the other hand, consumers’ interest in ancient wheat varieties, including spelt, is growing. The aim of this work is to compare the response to drought stress between spelt (Triticum aestivum ssp. spelta) and common wheat (Triticum aestivum ssp. vulgare). Six cultivars of spelt from different European countries and common wheat ‘Bogatka’ as a reference were chosen for research. The photosynthesis process, chlorophyll fluorescence, relative water content, and the content of free proline and anthocyanins in well-watered and drought-stressed plants were measured. It was shown that the spelt cultivars ‘Franckenkorn’ and ‘Badengold’ were much more resistant to water deficit than other cultivars and even common wheat. A slight reduction of CO2 assimilation (by 27%) and no reduction of transpiration rate, with simultaneous intensive proline (eighteen times fold increase) and anthocyanins accumulation (increase by 222%) along with a slight increase in lipid peroxidation level (1.9%) revealed in ‘Franckenkorn’ prove that this cultivar can cope with drought and can be effectively cultivated in areas with limited water abundance.