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The potential of employing multispectral data (400–1050 nm) for estimating leaf relative water content (RWC) and water content (WC) was investigated in chrysanthemum (Chrysanthemum morifolium L.). Detached leaves were exposed to desiccation (0–24 h). The abaxial leaf side showed a higher reflectance (0.1–0.2%) than the adaxial one in the visible spectrum (400–700 nm), whereas differences between leaf sides were minor in the near-infrared region (750–1050 nm). The overall reflectance of either leaf side increased in the course of desiccation. Leaf RWC and WC could not be accurately retrieved based on the whole reflectance range or eleven commonly-employed indices (R2 = 0.000–0.469). A convolutional neural network (CNN) predictive model was further developed. The input data were the multispectral images of either one (adaxial or abaxial) or both (adaxial and abaxial) leaf sides. These first underwent size enlargement and cropping and then a reduction in both size and wavelength band number. Pairs of convolutional-pooling layers, followed by a fully connected layer, were chosen as network architecture. The developed CNN model generated very accurate predictions of leaf RWC and WC (R2 = 0.852–0.964). The obtained protocol provides real-time, non-invasive and accurate determinations of leaf water status.

In a water shortage crisis, the landscape management of perennial ryegrass, a common lawn grass, is a major challenge. An organic material that can help to overcome this challenge is rice husk biochar (RHB). A pot experiment was carried out to evaluate whether RHB (0%, 5%, and 10% w/w ) can mitigate the adverse impacts of drought stress [100%, 50% and 25% of water holding capacity (WHC)] on the growth, physiological and biochemical attributes of perennial ryegrass. When soil was amended with RHB under drought stress, this improved soil physical and chemical properties as well as leaf nutrient content, and increased shoot and root dry weights by 36.27% and 31.36%, respectively compared to the no-biochar treatment. The highest increase in leaf nutrients was 64.77% for Mg 2+ and 25.45% for Fe 2+ . In addition, higher leaf relative water content and nutrient status in plants led to a higher production of chlorophyll (166.97%), and a decrease in the content of proline (−28.79%), hydrogen peroxide (−42.88%) and malondialdehyde (−14.13%). The use of RHB significantly improved visual quality by 30.53% and 50.13% at 50% and 25% WHC, respectively compared to the no-RHB treatment. The amendment of soil with RHB changed soil physico-chemical characteristics and increased nutrient uptake. As a result, shoot and root growth improved, chlorophyll content and photosynthetic efficiency were enhanced, and the drought tolerance of perennial ryegrass ultimately increased. Consequently, the application of RHB, especially at a higher concentration (10%), may be a potential strategy to mitigate drought stress.

Water scarcity is the major limiting factor for growth and yield in arid and semi-arid regions. Therefore, an experiment was conducted to investigate the effect of deficit irrigation on the yield, fruit quality and physiological responses of cucumber plants Cucumis sativus (L.) Kish F1 (i.e., a scion) either grafted or not grafted on the African horned cucumber rootstock under open field conditions. Irrigation treatments were 100, 80, and 60% of crop evapotranspiration (ETc). Results showed that plant growth and yield significantly decreased in response to deficit irrigation in both grafted and non-grafted plants. The fruit number and yield of grafted onto African horned cucumber rootstock were higher than those of non-grafted plants under deficit irrigation (60% ETc). Fruit firmness and vitamin C content significantly decreased with increasing water-deficit stress, while total soluble solid, phenolic compounds and antioxidant activity increased. Fruits of grafted plants had a significantly higher quality compared with non-grafted fruits under all irrigation regimes. Likewise, grafted plants showed significantly higher proline and leaf relative water content and lower electrolyte leakage compared with non-grafted plants under all irrigation regimes. These findings suggest that grafting cucumber onto drought-tolerant African horned cucumber rootstock could improve water-stress tolerance in cucumber.

Cadmium is one of the most carcinogenic and hazardous heavy metals on the earth for causes many serious diseases and disorders in the plant body. The presence of Cd in the soil is equally harmful to the production of rice crops and human beings. A pot experiment was conducted to analyze the consequences of cadmium-induced stress on the antioxidative defense system in rice plants. The assessment of antioxidative defense mechanism based on the cadmium-induced stress in the range of 100 to 300 ppm while the parameters, Chlorophyll Content Index (SPAD), nitrogen (%), relative water content (%), membrane stability index (%), proline content (μg.g-1), and catalase activity (nm H2O2 mg-1.min-1) were used. The highest reduction in the Chlorophyll Content Index (CCI), nitrogen (%), RWC (%), and MSI (%) was recorded at the highest concentrations of Cd Cl2 (300 ppm). However, at the same time, an increase in proline content (μg.g-1) and catalase activity (nm H2O2 mg-1.min-1) were also detected at all the intervals of the study. The activity of CCI, amino acid, and enzyme were presented in % increase/decrease over the control of Cd-induced stress in rice plants. The reduction (%) in CCI (SPAD) and RWC (%) was recorded maximum at 75 Days after transplanting (DAT), while nitrogen (%) and MSI (%) were recorded at 50 DAT. However, the increase (%) in proline and Catalase activity was maximum at 75 and 50 DAT.

Creeping bentgrass ( Agrostis stolonifera ) is a desirable turfgrass putting green species that is susceptible to drought stress. Planting drought-resistant creeping bentgrass will enhance the resilience of golf turf surfaces, lower required resource inputs, and reduce the environmental impact of golf courses. Creeping bentgrass cultivar performance data during drought stress are needed for informed selection of appropriate cultivars. We evaluated the drought performance of 19 cultivars of creeping bentgrass and found that newer creeping bentgrass cultivars such as Pure Distinction and others exhibited superior drought performance compared with older cultivars such as Penncross and L93 based on turf quality, photochemical yield, and leaf relative water content. The results of this work should be used to aid in the selection of drought-resistant creeping bentgrass cultivars for turfgrass practitioners.

This study was established to investigate the ability of the sunflower callus plant (Helianthus annuus L.) to tolerate salinity stress for two levels of NaCl (0 and 80 mM), three concentrations of IAA (0, 1.0, and 2.0 mg l-1), and BAP (0, 1.0, and 2.0 mg l-1) in lab conditions. Calli cultures were induced from the cotyledon of H. annuus L. cultured in an appropriate combination of growth regulators 2,4-D and kintein. The salinity results exhibited negative effects in most of the study indications, which can be revealed by a significant increase in sodium content (Na+), hydrogen peroxide (H2O2) and malondialdehde content (MDA). While, the decrease in the study indications such as fresh weight (FW), dry weights (DW), relative water content (RWC), potassium content (K+), sodium/ potassium ratio (Na+/K+), superoxide dismutase (SOD), and catalase (CAT) enzymes activity. The experiment revealed a positive effect for the exogenous growth regulators IAA and BAP in reducing the harmful effects of salinity stress on calli cultures. The nominated regulators succeeded in reducing the harmful effects of salinity stress, where the FW, DW, RFW, browning density (BI), RWC, K+, Na+/K+, SOD, and CAT  enzymes activity. However, the exogenous growth regulators reduced the negative effect for each of Na+, H2O2, and MDA under the salinity stress.

Alternate wetting and drying irrigation (AWDI) is a water-conserving strategy in rice fields. An experiment, conducted as a split-split plot design and based on a randomized complete block design with three repetitions, investigated the effect of intermittent irrigation and nitrogen on yield and water-use efficiency during 2017 and 2018 crop years in northern Iran. The irrigation intervals (flooding (I1), 7 days (I2), 14 days (I3)) were main factors, different levels of nitrogen fertilizer (50 kg/ha (N1), 75 kg/ha (N2), 100 kg/ha (N3)) were sub-factors, and cultivars (Gilaneh (C1) and Hashemi (C2)) were sub-sub-factors. Results showed that compared to flood irrigation, intermittent irrigation led to 16 to 43% and 13 to 43% water economization in 2017 and 2018, respectively, accompanied by a significant increase in water-use efficiency. By increasing the irrigation intervals, grain yield of the Gilaneh cultivar decreased significantly in all three fertilization levels. Compared to flood irrigation, total dry matter reduced significantly by increasing the irrigation interval. Maximum grain yield, total dry matter, and harvest index were achieved for the 100 kg/ha nitrogen fertilizer treatment in I1, I2, and I3 levels. Intermittent irrigation reduced leaf relative water content and increased leaf proline content in both cultivars. Leaf relative water content (R = 0.89**) showed the highest correlation coefficient with grain yield. The Hashemi cultivar showed higher leaf relative water content and leaf proline content and, while achieving 16.61% and 13.94% water conservation in the I2 treatment in 2017 and 2018, respectively, resulted in a yield equivalent to flood irrigation.

Guar is a drought- and salt-tolerant annual summer legume which could be a potential alternative crop in semiarid regions. The increased use of guar gum in oil industries has increased the global demand for guar. An experiment was carried out during 2 consecutive years to investigate the effect of plant density and nutrient application on yield and physiological characteristics of guar. A factorial experiment based on randomized complete block design with three replications was conducted during the 2017 and 2018 growing seasons. Studied factors included phosphorous (P1: 0, P2: 75 kg/ha, P3: 150 kg/ha, P4: 225 kg/ha) and folic acid application (F1: 0, F2: 4 kg/ha, F3: 8 kg/ha, F4: 12 kg/ha) and plant density (D1: 10 plants/m2 and D2: 20 plants/m2). Seed yield components, biological yield, protein value of seeds, leaf relative water content (RWC), guar percentage, and phosphorous-use efficiency (PUE) were measured. The highest biological yield (19058 kg/ha) and the highest seed yield (6129 kg/ha) were produced by the D1P4F4 and D2P4F4 treatments, respectively. Low plant density resulted in high biological yield, while high plant density resulted in high seed yield. The highest protein content (32.5%) was observed in D2P4F4. The highest RWC and gum percentage were produced in D2P4 and D2F4 treatments, respectively. An increase in P2O5 application rates up to 225 kg/ha significantly increased seed yield. The highest PUE (1.41 g/kg) was observed at a high plant density. Applying 225 kg/ha phosphorous fertilizer resulted in the highest PUE (1.5 g/kg). Therefore, increasing the application of phosphorous and folic acid could increase the yield and yield components of guar; a plant density of 20 plants/m2 could also increase the biological yield. The results of this study may also help to extend guar cultivation in other regions.

For generating different weather conditions during various phenological stages, experiments were conducted on two varieties of wheat (HD-2967 and HD-3086) sown on three different dates at the research farm of IARI, New Delhi during rabi 2015-16 and 2016-17. Soil temperature, soil moisture, leaf area index, biomass, chlorophyll content, radiation interceptions were measured during different crop growth stages. Number of days taken for each phenological stage was observed and thermal time for different phenological stages were calculated. Results showed that first sown crop had higher value of crop growth parameters and yield as compared to second and third sown crop.HD-3086 had higher value of LAI, biomass and yield than HD-2967. Grain yield had significant positive correlation with growing degree days during grain filling stage. Soil temperature measured at 2.21 PMat 5, 10, 15, 20 cm depth had 1-5°C lower value than the air temperature. Soil moisture measured at 0-15, 15-30, 30-45 and 45-60 cm depths had slightly higher soil moisture for HD-3086 as compared to corresponding value in HD-2967 during emergence, flowering and grain filling stages. Percentage relative water content in HD-2967 was found to be higher in first sown crop followed by second and third sown crop. However, in HD-3086, percentage relative water content was found to be higher in first sown crop followed by third and second sown crop. Grain yield had significant positive correlation with relative water content during different phenological stages. HD-3086hadhigherradiation use efficiency as compared to HD-2967 in all weather conditions.

Although primarily valued for their suitability for oceanographic applications and soil moisture estimation, microwave remote sensing observations are also sensitive to plant water content (M w). Since M w depends on both plant water status and biomass, these observations have the potential to be useful for a range of plant drought response studies. In this paper, we introduce the principles behind microwave remote sensing observations to illustrate how they are sensitive to plant water content and discuss the relationship between landscape-scale M w and common stand-scale metrics, including plant-scale relative water content, live fuel moisture content and leaf water potential. Lastly, we discuss how various sensor types can be leveraged for specific applications depending on the spatio-temporal resolution needed.