ADP-glucose pyrophosphorylase (AGPase) activity in the developing grains of two contrasting wheat cultivars WH730 (thermo-tolerant) and UP2565 (thermo-sensitive) was determined in relation to their allosteric effectors and grain growth. The developing grains (35 days after anthesis) were excised from the middle portion of spikes of wheat genotypes subjected to high temperature, drought and their combination at booting, post-anthesis and booting+post-anthesis. The impact of stress treatments was studied by measuring starch content and yield attributes in relation to AGPase activity. AGPase, a key enzyme for starch synthesis, is allosterically activated by 3-phosphoglyceric acid (3-PGA) and inhibited by inorganic phosphate (Pi). Sensitivity of AGPase towards individual and combined high temperature and drought has not been adequately investigated, therefore the present study analyzed AGPase activity, its sensitivity to allosteric effectors under influence of high temperature, drought in order to elucidate the relationship of AGPase with starch accumulation and grain growth. Significant difference in behavior of the enzyme and its allosteric effectors were observed between the two cultivars under high temperature and/or drought. AGPase activity was substantially decreased by high temperature, drought and was found to be positively correlated with the 3-PGA, starch accumulation and yield attributes, while negatively correlated with Pi content. The results showed that effects of high temperature and drought were additive and more severe at booting+post-anthesis stage. Such studies might help in understanding the control mechanisms associated with the pathway of starch biosynthesis and thus provide chemical means to manipulate starch content vis-à-vis grain yield under heat and drought stress.

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Investigations were carried out on a salt tolerant (Manak, H77-216) and a comparatively salt sensitive (ICPL 88039) genotypes of pigeonpea (Cajanus cajan L. Millsp.) under NaCl, B and NaCl + B stress to examine the acclimatory response to H2O2, glutathione and H2O2 + glutathione through their effect on mineral nutrition, morpho-physiological parameters and antioxidant defense system. Both B and NaCl alone and their combinations had deleterious effect on dry biomass of plumule, enhanced relative stress injury (RSI), lipid peroxidation with concomitant increase in Na, Cl and B contents. However it did not bear any correlation with osmotic potential of plumule and K contents. Antioxidative enzymes like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX) and glutathione reductase (GR) also decreased with salt, B and salt + B treatments. However contents of H2O2 enhanced and that of ascorbate declined under aforementioned treatments. These injurious effects are partially alleviated by exogenous application of H2O2; glutathione (GSH) and H2O2 + GSH treatments. The role of H2O2 and GSH in the present study is suggestive of triggering multifunctional signal transduction in plant defense mechanisms to prevent cellular oxidation, membrane injury, lipid peroxidation and protein enzyme inactivation.

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The study was conducted on six barley varieties viz. BH 885, BH 946, BH 393, BH 902, DWRB 92 and DWRB 101 at CCS HAU, Hisar during 2020-21. The results revealed that maximum catalase activity (243.168 and 157.981umoles/g FW), peroxidase activity (22.33 and 35.03 units/g FW), superoxide activity (22.03 and 35.03 nmoles/g FW) and dehydrogenase activity (0.213 and 0.245 OD/g/ml) were estimated in the seeds primed with ZnO NPs @ 100ppm in cloth and polythene bag, respectively in variety DWRB 92. Among the varieties, DWRB 92 recorded highest catalase activity (217.168 umoles/g FW) in cloth bag while BH 393 recorded maximum catalase activity (232.961 umoles/g FW) in polythene bag. Minimum catalase activity was observed in DWRB 101(60.351 umoles/g FW) in cloth and BH 885 recorded least (121.418 umoles/g FW) in polythene bags. Maximum peroxidase activity (21.22 and 31.56 units/g FW) was estimated in BH 885 while minimum (12.71 and 22.54 units/g FW) in BH 946 in cloth and polythene bag, respectively. Maximum SOD activity (18.033 and 25.033 nmoles/g FW) was measured in DWRB 92 and minimum (12.712 and 22.537 nmoles/g FW) in BH 946 in cloth and polythene bag, respectively. Maximum DHA activity (0.170 and 0.206 OD/g/ml) was recorded in DWRB 101 and least in BH 946 (0.234 and 0.281 OD/g/ml) in cloth and polythene bag. It is concluded that among the various seed priming treatments, priming with ZnO NPs@100ppm at 25°C for 24 hours maintained higher enzyme activity. Barley seed quality can be maintained by storing the seeds at optimum moisture content (<8%) in polythene bags (>700gauge) with germination upto 94.61% as compare to cloth bags (85.89%).