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Heat spell during the reproductive growth of wheat is a serious threat to achieve food security. An experiment was conducted with the objectives (i) to explore the optimum dose of foliar selenium for alleviation of heat, (ii) to investigate the thermo-lability of reproductive stages of wheat, (iii) to enquire about the correlation of biochemical attributes with agronomic traits, and (iv) to determine the economic feasibility of foliar selenium for alleviation of adverse impacts of heat on wheat. The study was conducted over 2 years using a split treatment structure in a randomized complete block design. Treatments were comprised of H0(control), H1(heat imposition from spike to grain filling), and H2(heat imposition from flowering to grain filling). Foliar doses of selenium (Se), viz., Se0= water spray (control); Se25= 25 mg Se L−1; Se50= 50 mg Se L−1; Se75= 75 mg Se L−1and Se100= 100 mg Se L−1were maintained in sub plots. The longer heat spell proved more deleterious than the shorter one. More catalase, glycine betaine, water potential, turgor potential, grain filling rate, spikelets per spike, grains per spike, and grain yield were recorded with 75 mg Se L−1under “H0,” while remarkably higher responses of these attributes were observed with 100 mg Se L−1under “H1” and “H2.” Based on marginal analysis, applying “75 mg Se L−1” resulted in higher economic benefits under “H0” and “H1,” whereas 50 mg L−1was more economical to apply under “H2.” Moreover, strong associations of physiochemical attributes with agronomic traits were observed. Decisively, applying “75 mg Se L−1” on terminally heat-stressed wheat produced more benefits compared to other doses.

High temperature stress during reproductive stages of wheat is a leading constraint in achieving food security. The objectives of study were to investigate heat sensitivity of terminal stages of wheat, to optimize foliar selenium dose, to boost nonenzymatic antioxidants and to determine correlation of these nonenzymatic antioxidants with yield and quality attributes of wheat crop. The field experiment was conducted for two consecutive years at agronomic research area, University of Agriculture Faisalabad, Pakistan. It was laid out in a randomized complete block design under split arrangement, and treatments were replicated thrice. Main plot factor comprised of heat imposition treatments; H0= Control; H1= Heat from spike to grain filling; H2= Heat from flowering to grain filling while in subplots doses of foliar selenium were maintained; Se0= Control (water spray); Se25= 25 mg L−1; Se50= 50 mg L−1; Se75= 75 mg L−1and Se100= 100 mg L−1. Impact of H1was more damaging compared to H2and H0for all response variables. Higher levels of proline, phenolics and leaf selenium were recorded with foliar spray of selenium either at 75 or at 100 mg L−1under H0, whereas under H1and H2, significantly higher responses were observed with 100 mg L−1selenium for these traits. Increases in leaf chlorophyll and grain protein contents were statistically alike with 75 and 100 mg L−1selenium; while in case of 1000-grain weight, harvest index and grain yield three levels of foliar selenium (50, 75 and 100 mg L−1) performed equally well under all the three heat stress treatments. Moreover, strong positive and significant associations of proline, phenolics, leaf selenium and chlorophyll were measured with yield of wheat. Conclusively, more harmful impacts were recorded under H1compared to H2and H0; while 75 mg L−1Se proved more beneficial under H0and 100 mg L−1Se under H1and H2. Strong associations of biochemical and agronomic traits were observed.

The concurrence of heat stress of different spells at the cotton flowering stage accelerates phenology and declines the fiber quality of cotton. A two-year field trial was conducted to examine the effect of exogenous chitosan application in alleviating the effects of heat stress on seed cotton yield, quality, phenology, and glycine betaine synthesis. Three levels of heat treatments were assigned to the main plots. Five levels of foliar spray of chitosan, i.e., 0, 0.2, 0.4, 0.6, and 0.8 g L−1, were applied in each subplot during heat stress imposition. The treatment plan was comprised of H0(control, no heat stress), H1(heat stress at flowering for 4 days), and H2(heat stress at flowering for 8 days). Heat stress at flowering for 8 days resulted in a remarkable decrease in glycine betaine synthesis, phenological parameters, seed cotton yield, and quality attributes compared to the control. The effects of heat stress were more pronounced when the exposure time was 8 days compared to 4 days. Chitosan foliar application significantly improved glycine betaine, seed cotton yield, earliness of maturity, and fiber quality, decreasing malondialdehyde contents in heat-stressed cotton. In contrast, the premier dose (0.8 g L−1) of chitosan proved more efficient than lower doses. It is concluded that exogenous application of chitosan at 0.8 g L−1was beneficial to arbitrating heat stress effect owing to its positive effect on fiber quality and seed cotton yield (increased by 22% over control).

The coincidence of terminal heat stress and late grain filling stage is a major constraint in wheat. The objectives of this study were to determine the thermo-sensitivity of reproductive stages of wheat, optimize the application of exogenous selenium to wheat, and explore the correlation of biochemical and agronomic attributes of wheat under heat stress. A 3 × 5 factorial experiment was laid out in a randomized complete block design with split arrangement and replicated thrice. The main plots were comprised of 3 levels of heat stress, viz., H0= no heat stress; H1= heat from spike to grain filling; and H2= heat from flowering to grain filling, while subplots included 5 levels of foliar selenium, Se0= control (water spray); Se25= 25 mg L-1; Se50= 50 mg L-1; Se75= 75 mg L-1; and Se100= 100 mg L-1. More detrimental responses were observed under H1compared to H2. Under H0, the application of Se at 75 mg L-1and 100 mg L-1significantly increased superoxide dismutase, peroxidase, soluble proteins, and osmotic potential, while it reduced malondialdehyde compared to other doses of Se. Under H1and H2, Se treatment (100 mg L-1Se) resulted in a significant increase in the recorded biochemical attributes and a significant reduction in malondialdehyde. Similar and higher plant height, spike length, and grain yield were observed at 75 mg L-1Se and 100 mg L-1Se, compared to other doses. Our findings suggest that wheat spike initiation was more sensitive to heat stress than flowering. While the application of 75 mg L-1Se was beneficial to plants under ambient environmental conditions, its responses were more promising under heat stress. The recorded biochemical attributes were closely related to the agronomic traits of wheat.

High temperature during reproductive stages of cotton is a major constraint to achieve potential yield of cotton. The aim of the present study was to determine comparative thermo-sensitivity of squaring and flowering, to optimize exogenous selenium for heat-stressed cotton, and to explore correlation among physiochemical and morphological attributes. The experiment was conducted during 2013 and repeated during 2014. The experiment was laid out in randomized complete block design under split plot arrangement and replicated thrice. Treatments were comprised of heat stress (H0= no heat imposition; H1= heat imposition at squaring; and H2= heat imposition at flowering) in main plot and varying foliar selenium concentrations (Se0= water spray/control; Se50= 50; Se100= 100; and Se150= 150 mg L-1selenium) in split plot. Significantly, more antioxidants, chlorophyll contents, water relation attributes, seed cotton yield, and lesser hydrogen peroxide were recorded with 150 mg L-1foliar selenium compared with other concentrations under H0. While under H1and H2, statistically similar and significantly more antioxidants, chlorophyll contents, water relation attributes, seed cotton yield, and lesser hydrogen peroxide were observed for 100 and 150 mg L-1selenium compared with other selenium concentrations. Conclusively, H2proved more thermolabile compared with H1, and application of 150 mg L-1foliar selenium effectively alleviated adverse effects of heat. Moreover, we observed strong and significant associations of all physiochemical attributes with seed cotton yield.