Leaf Relative Water Content Research Articles

Performance of Some Cotton (Gossypium hirsutum L.) Genotypes for Agronomical and Within-Boll Yield Characters

Evaluating the cultivars' performance is an important step in the cotton breeding process. Therefore, we tested the yield, fiber quality and within-boll yield components of genotypes, and associations among observed characters were estimated. Ten cotton genotypes inc., Bomba, Özbek 100, Ramses, May 455, Bir 949, Fiona, Şahin 2000, Sahra, Sasha and Eva, were planted in a Randomized Complete Block Design with four replications in 2022. The highest seed cotton yield was recorded in Sasha and Bomba genotypes. Ramses performed the higher ginning out-turn (47.70%) and favorable fiber fineness (4.62 mic.). Bir 949 (32.65 mm), Ramses (31.49 mm) and Sasha (31.31 mm) for fiber length; Sasha (35.18 g tex-1) and Sahra (34.08 g tex-1) for fiber strength exhibited desirable performances. The highest relative leaf water content (%) as a drought indicator was recorded in Ramses (67.79), Fiona (67.45), Şahin 2000 (65.25) and Bomba (65.11). The number of fibers per seed ranged from 10.82 thousand (Özbek 100) to 13.00 thousand (Bir 949). It was concluded that it seemed difficult to associate the seed cotton yield, fiber quality and relative leaf water content. Therefore, the genotypes in which all three traits are optimized should be emphasized.

Response of off-season strawberries (Fragaria sp.) production under the effects of paclobutrazol and drought stress

Strawberry (Fragaria sp.) is a fruit crop harvested seasonally with the peak season from August to November while the off-season harvest is January to June with limited harvest. The purpose of this study was to find the concentration of paclobutrazol and the level of drought stress for off-season strawberry production. This research conducted on April to July 2023. The experiment used a factorial Randomized Block Design consisting of 2 factors and 3 replications with 16 treatment combinations. The first factor was paclobutrazol consisting of four levels, namely P0 = control, P1 = 10,000 ppm, P2 = 20,000 ppm and P3 = 30,000 ppm and the second factor was the level of drought stress consisting of four levels i.e. C0 = 100% field capacity, C1 = 80% field capacity, C2 = 60% field capacity and C3 = 40% field capacity. The results showed that paclobutrazol accelerated flowering time, increased fruit set, leaf relative water content, root length, chlorophyll content, but decreased the number of fruits formed, harvested fruits, fruit diameter, harvested fruit weight, weight per fruit, root oven dry weight, percentage of fallen fruits and total soluble solids. Drought stress level increased leaf relative water content, root length, root oven dry weight, percentage of fallen fruit, percentage of fruit set, but decreased number of flowers formed, fruits harvested, weight of fruits harvested, weight per fruit, fruit diameter, total soluble solids, chlorophyll content and delayed flowering time.

Physiological Responses to Salt Stress at the Seedling Stage in Wild (Oryza rufipogon Griff.) and Cultivated (Oryza sativa L.) Rice

Domesticated rice Oryza sativa L. is a major staple food worldwide, and the cereal most sensitive to salinity. It originated from the wild ancestor Oryza rufipogon Griff., which was reported to possess superior salinity tolerance. Here, we examined the morpho-physiological responses to salinity stress (80 mM NaCl for 7 days) in seedlings of an O. rufipogon accession and two Italian O. sativa genotypes, Baldo (mildly tolerant) and Vialone Nano (sensitive). Under salt treatment, O. rufipogon showed the highest percentage of plants with no to moderate stress symptoms, displaying an unchanged shoot/root biomass ratio, the highest Na+ accumulation in roots, the lowest root and leaf Na+/K+ ratio, and highest leaf relative water content, leading to a better preservation of the plant architecture, ion homeostasis, and water status. Moreover, O. rufipogon preserved the overall leaf carbon to nitrogen balance and photosynthetic apparatus integrity. Conversely, Vialone Nano showed the lowest percentage of plants surviving after treatment, and displayed a higher reduction in the growth of shoots rather than roots, with leaves compromised in water and ionic balance, negatively affecting the photosynthetic performance (lowest performance index by JIP-test) and apparatus integrity. Baldo showed intermediate salt tolerance. Being O. rufipogon interfertile with O. sativa, it resulted a good candidate for pre-breeding towards salt-tolerant lines.

Water Deficit Diagnosis of Winter Wheat Based on Thermal Infrared Imaging

Field experiments were conducted to analyze the effectiveness of the crop stress index (CWSI) obtained by infrared thermal imaging to indicate crop water status, and to determine the appropriate CWSI threshold range for wheat at different growth stages. The results showed that the sensitivity of plant physiological parameters to soil water was different at different growth stages. The sensitivity of stomatal conductance (Gs) and transpiration rate (Tr) to soil water was higher than that of leaf relative water content (LRWC) and photosynthetic rate (Pn). The characteristics of plant physiology and biomass (yield) at each growth stage showed that the plant production would not suffer from drought stress as long as the soil water content (SWC) was maintained above 57.0% of the field water capacity (FWC) during the jointing stage, 63.0% of the FWC during the flowering stage and 60.0% of the FWC during the filling stage. Correlation analysis showed that the correlation of CWSI with Gs, Tr and Pn was lower than that with LRWC and SWC at the jointing stage. CWSI was extremely significantly negatively correlated with SWC and LRWC (p < 0.01), but significantly negatively correlated with Gs, Tr and Pn (p < 0.05). At the flowering stage, CWSI was extremely significantly negatively correlated with all physiological and soil parameters (p < 0.01). The regression analysis showed that the CWSI of winter wheat was correlated with biomass (grain yield) in a curvilinear relationship at each growth stage. When the CWSI increased to a certain extent, the biomass and yield showed a decreasing trend with the increase in CWSI. Comprehensive analysis of all indexes showed that CWSI can be used as a decision-making index to guide the water-saving irrigation of winter wheat, as long as the CWSI threshold of plants was maintained at 0.26–0.38 during the jointing stage, 0.27–0.32 during the flowering stage and 0.30–0.36 during the filling stage, which could not only avoid the adverse effects of water stress on crop production, but also achieve the purpose of water saving.

Poly-Glutamic Acid Promotes the Growth and the Accumulation of Main Medicinal Components in Salvia miltiorrhiza

Salvia miltiorrhiza Bunge is a traditional medicinal plant in China and poly-glutamic acid (PGA) is a valuable biopolymer. However, it is unclear whether PGA promotes growth and the accumulation of main medicinal components in S. miltiorrhiza. To elucidate this scientific question, the influences of PGA on the growth, physiological characteristics, and accumulation of main medicinal components in S. miltiorrhiza were explored through a pot experiment. The results revealed that PGA significantly promoted basal diameter, plant height, shoot and root biomass, as well as root volume, compared with control. PGA also increased SPAD value, net photosynthetic rate, actual and maximum photochemical efficiency of photosynthetic system II, photochemical quenching, and electronic transfer rate. Meanwhile, PGA increased transpiration rate, stomatal conductance, water use efficiency, leaf relative water content, and the contents of soluble protein, soluble sugar, and proline. Furthermore, PGA increased the activities of antioxidant enzymes and the contents of antioxidants. The above findings imply that PGA facilitated S. miltiorrhiza growth by enhancing photosynthetic performance, water metabolism, and antioxidant capacity. Additionally, PGA significantly improved the yield of rosmarinic acid, salvianolic acid B, dihydrotanshinone, cryptotanshinone, tanshinone I, and tanshinone ⅡA in roots by up-regulating the transcript levels of genes responsible for their biosynthesis. Our findings indicated that PGA promoted S. miltiorrhiza growth and the accumulation of main medicinal components in roots.

Drought tolerance in tough lovegrass (Eragrostis plana): Understanding mechanisms and competitive ability

AbstractEragrostis plana Nees is a perennial grass weed, native to South Africa and an invasive species of dry rangelands across Asia, Australia, and South America. We hypothesise that E. plana has evolved mechanisms of acclimation to drought conditions to a greater extent than bahiagrass (Paspalum notatum), an important native grass forage species of livestock rangelands of Brazil, leading to a competitive advantage. We measured morphological, physiological, and biochemical response traits in E. plana and P. notatum to water deficit and competition. Levels of drought tolerance in the two species were greatest at the tillering growth stage, driven by low levels of leaf relative water content in E. plana and early stomatal regulation to avoid water loss in P. notatum. The mechanisms used to dissipate energy excess under drought are associated with an efficient antioxidant system and the biosynthesis of compatible osmolytes (proline). Despite reductions in fitness, both species survived a series of drought cycles, where E. plana showed a competitive advantage over P. notatum. These results help to explain the invasion success of E. plana in rangelands and demonstrate its potential threat to native biodiversity, particularly under drought conditions.

Identification of major QTLs for drought tolerance in soybean, together with a novel candidate gene, GmUAA6.

Drought tolerance is a complex trait in soybean that is controlled by polygenetic quantitative trait loci (QTLs). In this study, wilting score, days-to-wilting, leaf relative water content, and leaf relative conductivity were used to identify QTLs associated with drought tolerance in recombinant inbred lines derived from a cross between a drought-sensitive variety, Lin, and a drought-tolerant variety, Meng. A total of 33 drought-tolerance QTLs were detected. Of these 17 were major QTLs. In addition, 15 were novel drought-tolerance QTLs. The most predominant QTL was on chromosome 11. This was detected in at least three environments. The overlapped mapping interval of the four measured traits was 0.2 cM in genetic distance (about 220 kb in physical length). Glyma.11g143500 (designated as GmUAA6), which encodes a UDP-N-acetylglucosamine transporter, was identified as the most likely candidate gene. The allele of GmUAA6 from Lin (GmUAA6Lin) was associated with improved soybean drought tolerance. Overexpression of GmUAA6Lin in Arabidopsis and soybean hairy roots enhanced drought tolerance. Furthermore, a 3-bp insertion/deletion (InDel) in the coding sequence of GmUAA6 explained up to 49.9% of the phenotypic variation in drought tolerance-related traits, suggesting that this InDel might be used in future marker-assisted selection of drought-tolerant lines in soybean breeding programs.

Grass pea (Lathyrus sativus) interesting panoply of mechanisms to cope with contrasting water stress conditions – a controlled study of sub populational differences in a worldwide collection of accessions

The grain legume Lathyrus sativus L. (grass pea) is of high economic importance for food and feed in Asian and African developing countries and is part of cultural heritage of marginal areas in the Mediterranean region. Its outstanding robustness under adverse environmental conditions, when compared with other legume species, raises particular interest under the current climate change scenario. The aim of this work was to study the range, extent and mechanisms underlying this species’ reported tolerance to water stress. To achieve this, a worldwide representative collection of 194 grass pea accessions was subjected to specific well-watered, water deficit and waterlogging conditions. These conditions were defined previously to elicit differential physiologic responses among the collection on 21 days old plants as continuously kept at 95% field capacity, at 5 days without irrigation reaching 55% field capacity, and at 14 days of partial submergence, respectively. The assessment encompassed a comprehensive set of 20 traits, including gas exchange, chlorophyll a fluorescence, leaf photosynthetic pigments, leaf water status and biomass partitioning. This detailed phenotypic analysis demonstrated that leaf relative water content and gas-exchange related traits are particularly useful to differentiate accessions’ response to water treatments. We discovered that accessions with light and large seeds mostly of Mediterranean and East European origins produce plants with high total dry biomass, a trait that is mostly genetically determined and less affected by the water treatment. On the other hand, it is mainly dark and small seeded accessions that show advantageous physiological responses to water deficit and/or waterlogging, according to pigment contents, root to shoot ratio and water use efficiency traits. This integrative screening also allowed the identification of accessions displaying contrasting levels of tolerance and susceptibility to each stress (five tolerant and five susceptible to each stress), plus one multi-tolerant (PI283546) and one multi-susceptible (PTLS1001) accession. A comprehensive and deep understanding of grass pea’s water stress tolerance mechanisms is the first step for a more efficient exploitation of this grain legume as a model crop for multiple abiotic stress resistance studies and opens doors for further progresses on crop breeding efforts towards securing food and feed supplies.

Conservation tillage and residue management practices in rice improves stress tolerance of succeeding vegetable pea by regulating physiological traits in Eastern Himalayas

The majority areas of valley lands in the Himalayan foothills remains fallow after the rice harvest. Recycling of plant biomass with conservation tillage may help in enhancing soil water availability, crop physiological function and productivity under moisture stress hill environments of this region. The present study focused on three tillage practices viz., no-till (NT), minimum tillage (MT) and conventional tillage (CT) and five nutrient management (NM) practices viz., 100 % NPK, 50 % NPK, 50 % NPK + in-situ residue retention (ISRR), 50 % NPK + weed biomass (WB) and 50 % NPK + green leaf manure (GLM) in rice and their residual effect on physio-biochemical properties, yield attributes and produce quality traits of succeeding pea varieties (Arkel and Prakash). Results revealed that total leaf chlorophyll content in vegetable pea varieties Arkel and Prakash was 12.0 and 11.5 % higher under no-till (NT) followed by 11.9 and 10.6 %, respectively under minimum tillage (MT) as compared to conventional tillage (CT) in rice. Similarly, application of 50 % NPK+ green leaf manure (GLM) and 50 % NPK+ weed biomass (WB) enhanced total leaf chlorophyll content in pea by 6.50–8.17 % and 3.93–5.48 % for pea varieties Arkel and Prakash, respectively. Photosynthetic rate and leaf dry weight were found 40.4 and 80.2 % higher under MT in Arkel whereas transpiration rate (E) and shoot dry matter were 33.1 and 19.3 % higher in Prakash under MT. Leaf water potential and root-to-shoot ratio were found 22.6 and 16.5 % higher in Prakash under MT and NT compared to CT respectively. Leaf temperature and stomatal conductance were 8.67 % lower and 9.8 % higher under MT in Prakash respectively as compared to CT, whereas 4.8 and 13.0 % higher under 50 % NPK +GLM and 50 % NPK+WB as compared 100 % NPK. Leaf cell viability was 22.5 and 20.1 % higher under MT whereas leaf MDA content was 29.9 and 28.3 % higher under MT in Arkel and Prakash respectively. Leaf relative water content was significantly higher to the tune of 25.7 and 22.4 % under NT compared to CT whereas leaf cell membrane integrity was 41.3 and 40.4 % higher under NT for Arkel and Prakash. Higher pod protein was noticed under MT along with 50 % NPK+GLM (13.1 %), whereas total soluble sugar was recorded highest under NT with 50 % NPK+GLM (21.1 %) in Prakash and MT with 50 % NPK+GLM (18.3 %) in Arkel. However, in both varieties, lower TSS was recorded under CT and with 50 % NPK (14.2 and 11.2 %) and the reducing sugar was maximum under the application of 50 % NPK+WB as compared to 100 % NPK alone. For both varieties of pea, green pod yield was recorded highest under MT (4.76 & 5.89 t/ha) as compared to CT (4.76 & 6.17 t/ha) and NT (4.76 & 5.55 t/ha). While 50 % NPK+WB has recorded significantly highest green pod yield of Arkel, 50 % NPK+ GLM has caused the highest yield of Prakash. PCA executed on physiological traits explained the total variability to the tune of 85.50 %, thereby extracting three PC's viz., PC 1 (62.63 %), 12.58 %) and 10.28 %, respectively. Thus, the adoption of MT in rice followed by NT in winter pea with the application of 50 % NPK+WB or 50 % NPK+GLM is promising for better physiological traits and subsequently favoring the grain yield of pea under stressful hill environments of Eastern Himalaya.

Transcriptome Analysis Reveals Drought-Responsive Pathways and Key Genes of Two Oat (Avena sativa) Varieties.

To cope with the yield loss caused by drought stress, new oat varieties with greater drought tolerance need to be selected. In this study, two oat varieties with different drought tolerances were selected for analysis of their phenotypes and physiological indices under moderate and severe soil drought stress. The results revealed significant differences in the degree of wilting, leaf relative water content (RWC), and SOD and CAT activity between the two oat genotypes under severe soil drought stress; moreover, the drought-tolerant variety exhibited a significant increase in the number of stomata and wax crystals on the surface of both the leaf and guard cells; additionally, the morphology of the guard cells was normal, and there was no significant disruption of the grana lamella membrane or the nuclear envelope. Furthermore, transcriptome analysis revealed that the expression of genes related to the biosynthesis of waxes and cell-wall components, as well as those of the WRKY family, significantly increased in the drought-tolerant variety. These findings suggest that several genes involved in the antioxidant pathway could improve drought tolerance in plants by regulating the increase/decrease in wax and cell-wall constituents and maintaining normal cellular water potential, as well as improving the ability of the antioxidant system to scavenge peroxides in oats.

Seed priming with selenium improves growth and yield of quinoa plants suffering drought

Drought stress is a worldwide threat to the productivity of crops, especially in arid and semi-arid zones of the world. In the present study, the effect of selenium (Se) seed priming on the yield of quinoa under normal and drought conditions was investigated. A pot trial was executed to enhance the drought tolerance in quinoa by Se seed priming (0, 3, 6, and 9 mg Se L−1). The plants were exposed to water stress at three different growth stages of quinoa, viz. multiple leaf, flowering, and seed filling. It was noticed that drought significantly affected the yield components of quinoa, however, Se priming improved the drought tolerance potential and yield of quinoa by maintaining the plant water status. Se priming significantly increased main panicle length (20.29%), main panicle weight (26.43%), and thousand grain weight (15.41%) as well as the gas exchange parameters (transpiration rate (29.74%), stomatal conductance (35.29%), and photosynthetic rate (28.79%), total phenolics (29.36%), leaf chlorophyll contents (35.97%), water relations (leaf relative water contents (14.55%), osmotic potential (10.32%), water potential (38.35%), and turgor potential (31.37%), and economic yield (35.99%) under drought stress. Moreover, Se priming markedly improved grain quality parameters i.e., phosphorus, potassium, and protein contents by 21.28%, 18.92%, and 15.04%, respectively. The principal component analysis connected the various study scales and showed the ability of physio-biochemical factors to describe yield fluctuations in response to Se seed priming under drought conditions. In conclusion, a drought at the seed-filling stage has a far more deleterious impact among other critical growth stages and seed priming with Se (6 mg L−1) was found more effective in alleviating the detrimental effects of drought on the grain yield of quinoa.

Effect of Pruning on Morpho-physiological Characters and Yield of Pumpkin (Cucurbita moschata)

The present study was carried out at the Instructional cum Research Farm, Department of Horticulture, Biswanath College of Agriculture, Assam Agricultural University, Biswanath Chariali with an aim to study the morpho-physiological characters and yield as influenced by pruning in pumpkin. Pumpkin is an important commercial vegetable crop of Assam which is cultivated mainly during rabi season.The treatments were: T1(Trimming of growing tip of the primary vine at 8th node stage), T2(Trimming of growing tip of the primary vine at 10th node stage), T3(Trimming of growing tip of the primary vine at 12th node stage), T4(Trimming of growing tip of the secondary vine at 6th node stage), T5(Trimming of growing tip of the secondary vine at 8th node stage), T6(Removal of all tertiary vines), T7(Retention of two tertiary vines) and T8(control without pruning). The study revealed that among the treatments, T4 recorded the highest primary vine length and inter-nodal length of primary vine at 60, 90 DAS and at 1st harvest. Number of primary vine was found to be highest under T5 whileT3 recorded maximum number of secondary vines, inter-nodal length of secondary vines, the highest total leaf chlorophyll content, relative leaf water content, leaf area index and maximum fruit yield. Therefore, trimming of growing tip of the primary vine at 12th node stage can be suggested for pumpkin to get maximum yield.

Effects of Decapitation, Water-Deficit Stress, and Pot Size on Morpho-Anatomy and Physiology of Pterocarpus indicus

The interacting effects of stem decapitation, water-deficit stress, and pot size on the growth, morpho-anatomical, and physiological traits of Pterocarpus indicus seedlings were analyzed in this study. Changes in root collar diameter (RCD), biomass allocation, number of leaflets (NL), mean leaf area, guard cell size, stomatal aperture size, phloem cap fiber (PCF) thickness, xylem vessel density (XVD), relative leaf water content (RWC), stomatal conductance (gsw), transpiration rate (E), fluorescence quantum yield, transpiration (E), photosynthesis (PN), and electron transport rate (ETR) of decapitated and undecapitated P. indicus seedlings in different pot sizes (small, medium, large) and watering regimes (every 2, 7, and 14 days) were analyzed. The decapitation × water-deficit stress × and pot size interaction did not affect growth and morpho-anatomical variables, but they did on most of the physiological traits. Decapitated seedlings watered every 14 days and planted in medium or large pots have lower gsw, PN, E, and RWC. While the RCD of large-potted and water-stressed (every 14 days) seedlings decreased, allocations to stem and fine roots increased. Moreover, the NL and PCF significantly decreased, while the ETR and XVD significantly increased in decapitated and water-stressed seedlings. Overall, the decapitation-watering interaction caused significant stress to P. indicus seedlings. Keywords: biomass allocations, decapitation, drought stress, multiple stress, xylem vessel density

Optimization of Low-Tech Protected Structure and Irrigation Regime for Cucumber Production under Hot Arid Regions of India.

Water scarcity and climate variability impede the realization of satisfactory vegetable yields in arid regions. It is imperative to delve into high-productivity and water-use-efficient protected cultivation systems for the sustained supply of vegetables in harsh arid climates. A strenuous effort was made to find suitable protected structures and levels of irrigation for greenhouse cucumber production in hot arid zones of India. In this endeavor, the effects of three low-tech passively ventilated protected structures, i.e., naturally ventilated polyhouse (NVP), insect-proof screenhouse (IPS) and shade screenhouse (SHS), as well as three levels of irrigation (100%, 80% and 60% of evapotranspiration, ET) were assessed for different morpho-physiological, yield and quality traits of the cucumber in a two-year study. Among the low-tech protected structures, NVP was found superior to IPS and SHS for cucumber performance, as evidenced by distinctly higher fruit yields (i.e., 31% and 121%, respectively) arising as a result of higher fruit number/plants and mean fruit weights under NVP. The fruit yield decreased in response to the degree of water shortage in deficit irrigation across all protected structures. However, the interaction effect of the protected structure and irrigation regime reveals that plants grown under moderate deficit (MD, 20% deficit) inside NVP could provide higher yields than those obtained under well-watered (WW, 100% of ET) conditions inside IPS or SHS. Plant growth indices such as vine length, node number/plant, and shoot dry mass were also measured higher under NVP. The greater performance of cucumber under NVP was attributed to a better plant physiological status (i.e., higher photosystem II efficiency, leaf relative water content and lower leaf water potential). The water deficit increased water productivity progressively with its severity; it remained higher in NVP, as reflected by 20% and 94% higher water productivity than those recorded in IPS and SHS, respectively, across different irrigation levels. With the exception of total soluble solids and fruit dry matter content (which were recorded higher), fruit quality parameters were reduced under water deficit conditions. The findings of this study emphasize the importance of considering suitable low-tech protected structures (i.e., NVP) and irrigation levels (i.e., normal rates for higher yields and moderate deficit (-20%) for satisfactory yields) for cucumber in hot arid regions. The results provide valuable insights for growers as well as researchers aiming to increase vegetable production under harsh climates and the water-limiting conditions of arid regions.

Rutin improves salt stress tolerance in Zea mays L. by modulating osmolytes accumulation and antioxidant capacity

Maize seedlings were grown hydroponically to study the effect of exogenous rutin (Rut) on changes in the stress parameters (thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), total chlorophyll), water status (leaf relative water content (RWC), osmolytes such as proline, total soluble sugar), and activities of the main antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD)) in seedlings under salt stress. After 21 days of growth, plants were applied with Rut as foliar spray pretreatments for 24 hours, and after that, seedlings were exposed to osmotic stress induced by 100 and 200 mM NaCI in the Hoagland’s Solution for 72 hours. Six treatments with three replicates were tested, including a control (basal nutrients without NaCl or Rut), 150 mM NaCl, 200 mM NaCI, Rut, Rut+150 mM NaCl, and Rut+200 mM NaCl. Plant leaves were harvested 25 days after treatments and assayed for the above analysis. Exogenous Rut significantly decreased TBARS and H2O2 contents in leaves of salt-stressed seedlings compared to salt stresses, enhanced the level of osmolytes, leaf RWC, activities of SOD, CAT, APX, and POD, and relative expression levels of SOD, CAT1, and APX1. Besides, the effects were more hopeful under 150 mM NaCl stress. As a result, findings from the study present reveal the effect of Rut on salt stress tolerance in maize seedlings under different osmotic stress. Here, it was clear that Rut played an active role in stress-alleviating. This application under salt stress can be useful in developing salt stress tolerance in crops for the agriculture sector.

The fungal endophyte Metarhizium anisopliae (MetA1) coordinates salt tolerance mechanisms of rice to enhance growth and yield

The implementation of salt stress mitigation strategies aided by microorganisms has the potential to improve crop growth and yield. The endophytic fungus Metarhizium anisopliae shows the ability to enhance plant growth and mitigate diverse forms of abiotic stress. We examined the functions of M. anisopliae isolate MetA1 (MA) in promoting salinity resistance by investigating several morphological, physiological, biochemical, and yield features in rice plants. In vitro evaluation demonstrated that rice seeds primed with MA enhanced the growth features of rice plants exposed to 4, 8, and 12 dS/m of salinity for 15 days in an agar medium. A pot experiment was carried out to evaluate the growth and development of MA-primed rice seeds after exposing them to similar levels of salinity. Results indicated MA priming in rice improved shoot and root biomass, photosynthetic pigment contents, leaf succulence, and leaf relative water content. It also significantly decreased Na+/K+ ratios in both shoots and roots and the levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide, while significantly increasing proline content in the leaves. The antioxidant enzymes catalase, glutathione S-transferase, ascorbate peroxidase, and peroxidase, as well as the non-enzymatic antioxidants phenol and flavonoids, were significantly enhanced in MA-colonized plants when compared with MA-unprimed plants under salt stress. The MA-mediated restriction of salt accumulation and improvement in physiological and biochemical mechanisms ultimately contributed to the yield improvement in salt-exposed rice plants. Our findings suggest the potential use of the MA seed priming strategy to improve salt tolerance in rice and perhaps in other crop plants.

Enhancing salinity tolerance in cucumber through Selenium biofortification and grafting

BackgroundSalinity stress is a major limiting factor for plant growth, particularly in arid and semi-arid environments. To mitigate the detrimental effects of salinity stress on vegetable production, selenium (Se) biofortification and grafting onto tolerant rootstocks have emerged as effective and sustainable cultivation practices. This study aimed to investigate the combined effects of Se biofortification and grafting onto tolerant rootstock on the yield of cucumber grown under salinity stress greenhouse conditions. The experiment followed a completely randomized factorial design with three factors: salinity level (0, 50, and 100 mM of NaCl), foliar Se application (0, 5, and 10 mg L-1 of sodium selenate) and grafting (grafted and non-grafted plants) using pumpkin (Cucurbita maxima) as the rootstock. Each treatment was triplicated.ResultsThe results of this study showed that Se biofortification and grafting significantly enhanced salinity tolerance in grafted cucumbers, leading to increased yield and growth. Moreover, under salinity stress conditions, Se-Biofortified plants exhibited increased leaf relative water content (RWC), proline, total soluble sugars, protein, phenol, flavonoids, and antioxidant enzymes. These findings indicate that Se contributes to the stabilization of cucumber cell membrane and the reduction of ion leakage by promoting the synthesis of protective compounds and enhancing antioxidant enzyme activity. Moreover, grafting onto pumpkin resulted in increased salinity tolerance of cucumber through reduced Na uptake and translocation to the scion.ConclusionIn conclusion, the results highlight the effectiveness of Se biofortification and grafting onto pumpkin in improving cucumber salinity tolerance. A sodium selenate concentration of 10 mg L-1 is suggested to enhance the salinity tolerance of grafted cucumbers. These findings provide valuable insights for the development of sustainable cultivation practices to mitigate the adverse impact of salinity stress on cucumber production in challenging environments.

Increasing cotton lint yield and water use efficiency for subsurface drip irrigation without mulching.

Planting without mulching can eliminate the residual film pollution caused by the long-term use of plastic film covers, but it will increase soil moisture evaporation and heat loss and severely reduce water use efficiency and cotton productivity in cotton (Gossypium hirsutum L.) fields in arid regions. It is unclear whether the advantages of subsurface drip irrigation and nighttime irrigation can be leveraged to reduce the amount of irrigation applied in fields, improve the soil and leaf hydrothermal environments, and increase the synchronicity of yield and water use efficiency (WUE). Therefore, in a two-year field experiment (2019-2020), cotton was grown under different irrigation treatments (I5, 3753 m3 ha-1; I4, 3477 m3 ha-1; I3, 3201 m3 ha-1; I2, 2925 m3 ha-1; and I1, 2649 m3 ha-1). The soil volumetric moisture content, soil temperature, leaf relative water content (RWC), daily changes in gas exchange parameters, lint yield, and WUE were evaluated. The results showed that reducing irrigation can reduce the soil volumetric moisture content (0-40cm soil layer), increase the soil temperature and soil temperature conductivity, and increase the leaf temperature, intercellular carbon dioxide concentration (Ci), and WUE; however, reducing irrigation is not conducive to increasing the leaf RWC, net photosynthetic rate (Pn), stomatal conductance (Gs), or transpiration rate (Tr). There was no significant difference in WUE between the I3 and I4 treatments from 8:00 to 20:00, but the lint yield in these treatments increased by 2.8-12.2% compared to that in the I5 treatment, with no significant difference between the I3 and I4 treatments. In addition, a related analysis revealed that the positive effects of the leaf hydrothermal environment on the Pn and soil temperature on the WUE occurs during the same period (10:00-16:00). Overall, an irrigation amount of 3201-3477 m3 ha-1 applied with a subsurface nighttime irrigation system without mulching can enhance the soil moisture content and soil temperature, maintain a high photosynthetic capacity, and increase the lint yield and WUE. These results revealed that the negative impacts of plastic film contamination in arid areas can be alleviated.

Composts of diverse green wastes improve the soil biological quality, but do not alleviate drought impact on lettuce (Lactuca sativa L.) growth

AbstractIntense soil cultivation and climate change have detrimental effects on soils. Solutions are needed to improve the biological quality and water holding capacity of agricultural soils. A greenhouse experiment was conducted to investigate the interactive effect of compost application and drought stress on a soil/plant system in order to determine the improvement of soil quality and plant growth and the alleviation of drought stress. Lettuce (Lactuca sativa L.) was grown under greenhouse conditions in a sandy soil with sufficient mineral fertilizer application to test the effect of five compost types (three made from municipal garden and park wastes with differing nutrient contents, one from municipal household waste, and one from farm plant residues) applied at 30 Mg ha−1 dry weight, with which we compared soil quality and plant growth to soil without compost application. Treatment pots were irrigated or subjected to drought conditions during the last 14 days of lettuce growth. Assays of potential N mineralization during 28 days, dehydrogenase and β‐glucosidase activities, and a phospholipid fatty acid (PLFA) analysis were performed to assess effects on soil biological quality. Gas exchange, leaf relative water content, biomass, nitrogen accumulation, and root tip growth of lettuce were measured to investigate compost and drought stress effects on lettuce physiology. All composts improved indices of soil biological quality significantly, except for fungal abundance, relative to soil without compost. The greatest increase was obtained from farm compost, which significantly increased potential nitrogen (N) mineralization and soil enzyme activities of β‐glucosidase and dehydrogenase by factors of 4, 2, and 43, respectively. Furthermore, soil with farm compost generally showed a higher abundance of soil microbial organisms compared with soil without compost, which could be related to its high cellulose and hemicellulose contents. The lowest abundance of microbial organisms was generally found in soil with garden and park waste compost with a medium nutrient content, which could be related to its low organic matter content. The beneficial effect of compost on soil biological quality did not lead to improved lettuce growth, which suggests that soil biological quality (ameliorated by compost application) is not important for a fast‐growing crop, such as lettuce, that is sufficiently fertilized. Drought stress reduced aboveground lettuce biomass, root tip growth, and the abundance of most soil microbial groups significantly, but compost in soil did not alleviate these negative effects. In conclusion, the farm compost made from grass–clover, straw, and vegetable residues is superior to garden and park waste and household waste composts in terms of beneficial effects on soil biological quality. Compost clearly improved soil biological quality, but did not influence lettuce's response to drought stress. The knowledge gained in this study is useful for producing tailor‐made compost with desired effects of improved soil biological quality.

Photosynthetic acclamatory response of Panicum antidotale Retz. populations to root zone desiccation stress

Abstract Growth of plants is severely reduced due to water stress by affecting photosynthesis including photosystem II (PSII) activity and electron transport. This study emphasised on comparative and priority targeted changes in PSII activity due to progressive drought in seven populations of Panicum antidotale (P. antidotale) collected from Cholistan Desert and non-Cholistan regions. Tillers of equal growth of seven populations of P. antidotale grown in plastic pots filled with soil were subjected progressive drought by withholding water irrigation for three weeks. Progressive drought reduced the soil moisture content, leaf relative water content, photosynthetic pigments and fresh and dry biomass of shoots in all seven populations. Populations from Dingarh Fort, Dingarh Grassland and Haiderwali had higher growth than those of other populations. Cholistani populations especially in Dingarh Grassland and Haiderwali had greater ability of osmotic adjustment as reflected by osmotic potential and greater accumulation of total soluble proteins. Maximum H2O2 under water stress was observed in populations from Muzaffargarh and Khanewal but these were intermediate in MDA content. Under water stress, populations from Muzaffargarh and Dingarh Fort had greater K+ accumulation in their leaves. During progressive drought, non-Cholistani populations showed complete leaf rolling after 23 days of drought, and these populations could not withstand with more water stress condition while Cholistani populations tolerated more water stress condition for 31 days. Moreover, progressive drought caused PSII damages after 19 days and it became severe after 23 days in non-Cholistani populations of P. antidotale than in Cholistani populations.