Heat waves at the regional level could be devastating if they coincide with the sensitive growth stage of the crop. The sensitivity of wheat (Triticum aestivum L.) to heat stress is a major constraint limiting wheat production. Nevertheless, there are limited field studies where the impact of heat waves has been systematically studied and quantified. We phenotyped a mini panel of thirty diverse wheat genotypes under optimum and low planting densities. Staggered sowing was done to expose the late-sown genotypes to a higher temperature at the terminal growth stage. Heat wave occurred during March–April, 2022, resulting in late sown genotypes being exposed to a staggering 6.6 °C/4 °C higher day/night temperature during flowering and early grain filling stage, as compared to normal sown genotypes. Heat stress caused significant loss in biomass (34.46%), grains spike⁻¹ (22.34%), test weight (15.52%), and grain yield (28.67%) in late-sown genotypes as compared to normal-sown genotypes. Conversely, genotypes grown under low planting density showed substantial variations in growth parameters including plant height, tillering, thicker leaves, and canopy cover. Interestingly, genotypes with denser canopy and thicker leaves could avoid high day temperature-induced losses by maintaining lower canopy and spike temperatures, which eventually resulted in higher grains spike⁻¹. However, the impact of higher night temperature on biomass and seed weight was not affected by denser canopy and lower spike temperature. Hence, yield loss was majorly confined to high night temperature. The study suggests that higher night temperature could be a major determinant of yield under naturally occurring heat waves.

如果区域层面的热浪恰逢作物的敏感生长阶段，则可能具有毁灭性。小麦（ Triticum aestivum L.）对热胁迫的敏感性是限制小麦产量的主要制约因素。然而，系统研究和量化热浪影响的实地研究却很有限。我们在最佳和低种植密度下对三十种不同小麦基因型的迷你小组进行了表型分析。进行交错播种以使晚播基因型在生长末期暴露于较高温度。2022 年 3 月至 4 月期间发生了热浪，导致晚播基因型在开花和早期灌浆阶段的昼夜温度比正常播种的基因型高出惊人的 6.6 °C/4 °C。与正常播种的基因型相比，热应激导致晚播基因型的生物量（34.46％）、谷物峰值^{-1 （22.34％）、容重（15.52％）和谷物产量（28.67％）显着损失。}相反，在低种植密度下生长的基因型显示出生长参数的显着变化，包括株高、分蘖、较厚的叶子和冠层覆盖度。有趣的是，具有更密集的冠层和更厚的叶子的基因型可以通过维持较低的冠层和穗温度来避免高温引起的损失，这最终导致更高的谷物穗^-1。然而，较高的夜间温度对生物量和种子重量的影响并未受到较密的冠层和较低的穗温的影响。因此，产量损失主要限于夜间高温。研究表明，在自然发生的热浪下，较高的夜间温度可能是产量的主要决定因素。