Terminal heat stress leads to sizeable yield loss in late-sown wheat in tropical environments. Several synthetic compounds are known to counteract plant stress emanating from abiotic factors. A field experiment was conducted in Sabour (eastern India) during 2013–2016 to investigate the field efficacy of two synthetic compounds, calcium chloride (CaCl2) and arginine, for improving grain yield of two contrasting wheat cultivars (DBW 14 and K 307) facing terminal heat stress. For this, foliar spray of 18.0 mM CaCl2 at booting (CCB) or anthesis (CCA), 9.0 mM CaCl2 at both booting and anthesis (CCB+A), 2.5 mM arginine at booting (ARGB) or anthesis (ARGA) and 1.25 mM arginine at both booting and anthesis (ARGB+A) treatments along with no-spray and water-spray treatments were evaluated in late-sown wheat. The highest grain yield was recorded in treatment CCB+A, followed by CCA and ARGB+A. However, the effect of these compounds was marginal on grain yield when applied only at the booting stage. Grains/ear and thousand-grain weight were found to be the critical determinants for yield in late-sown wheat. During the anthesis to grain filling period, flag-leaf chlorophyll degradation and increase in relative permeability in no-spray treatment were 34–36% and 29–52%, respectively, but these values were reduced considerably in CCB+A treatment followed CCA. Thus, foliar spray of 9.0 mM CaCl2 both at booting and anthesis stages may be recommended for alleviating the negative impacts of terminal heat stress in late-sown wheat and improving its productivity (>13%).

中文翻译：

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叶面喷施氯化钙和精氨酸对晚播小麦（Triticum aestivum L.）终末热应激的缓解作用

终末热应激导致热带环境中晚播小麦的大量产量损失。已知几种合成化合物可以抵消由非生物因素引起的植物压力。2013 年至 2016 年期间，在萨布尔（印度东部）进行了一项现场实验，以研究两种合成化合物氯化钙（CaCl2) 和精氨酸，用于提高面临终端热应激的两种不同小麦品种（DBW 14 和 K 307）的籽粒产量。为此，叶面喷洒 18.0 mM CaCl2在启动时（CC乙) 或花期 (CC一种), 9.0 毫米氯化钙2在引导和开花（CCB+A), 2.5 mM 精氨酸在启动时 (ARG乙) 或花期 (ARG一种) 和 1.25 mM 精氨酸在启动和开花时 (ARGB+A) 处理以及不喷洒和水喷洒处理在晚播小麦中进行了评估。最高的粮食产量记录在处理CCB+A, 其次是 CC一种和 ARGB+A. 然而，当仅在孕穗期施用时，这些化合物对籽粒产量的影响很小。发现粒/穗和千粒重是晚播小麦产量的关键决定因素。在开花至灌浆期，未喷施处理的旗叶叶绿素降解和相对渗透率增加分别为 34-36% 和 29-52%，但在 CC 处理中这些值显着降低B+A治疗后CC一种. 因此，叶面喷洒 9.0 mM CaCl2可建议在孕穗期和开花期都使用，以减轻晚播小麦终端热应激的负面影响并提高其生产力（>13%）。