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We examined effects of late-season heat stress (L-SHS) on chlorophyll (Chl) fluorescence parameters and yield of bread wheat as well as roles of phosphate bio-fertilizer (PB-F) and Zn and B to compensate for the likely effects of heat stress. Factors were planting date (21 November and 5 January to coincide with grain filling to L-SHS) as the main factor, no inoculation (control) and inoculation of the seeds with PB-F as the sub-factor, and foliar application of water (control), Zn, B, and Zn + B as 3 L ha -1 as sub-sub factor. Results revealed that L-SHS reduced maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, efficiency of PSII in the light-adapted state, and the grain yield. Moreover, L-SHS increased the nonphotochemical quenching. The PB-F mitigated the effects of L-SHS on Chl fluorescence, yield, and yield components. Among nutrients, the combined Zn + B was more effective in reducing the effects of L-SHS than that of Zn and B alone. Nevertheless, there was an interaction between foliar nutrients application and PB-F, suggesting that Zn application alone had a profound influence on improving Chl fluorescence parameters and increased yield in combination with PB-F.

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Effects of hormonal priming by cytokinin (CK), auxin, and gibberellin (GA) at 0, 25, 50, and 100 ppm of aged and nonaged seeds of bromegrass (Bromus inermis) on some physiological properties of seedlings were evaluated in a pot experiment. The seeds were subjected to accelerated aging to produce aged seeds. Percentage and rate of seedling emergence, seedling vigor, seedling-growth rate (SGR), seedling dry weight, chlorophyll and activity of catalase and peroxidase of seedling decreased following accelerated aging. Auxin priming improved emergence, vigor, SGR, root length, shoot, and seedling height. CK produced largest leaf area, whereas GA-primed seed had the highest concentration of chlorophyll in seedlings. Results suggested that physiological quality of bromegrass seed, especially aged seed, could be improved by hormonal priming. Auxin had the most positive effect on percent emergence, rate of emergence and SGR; CK and GA had positive effects on chlorophyll and leaf area. The three phytohormones in appropriate ratio in the priming solution improved aged seeds of bromegrass physiologically.