Drought and exposure to high temperature at flowering strongly affect maize production. However, previous studies mostly focused on the effects of the stressors on kernel number. The impacts of drought and heat in isolation and combination at flowering on maize kernel filling and final kernel weight have received limited attention. Here we investigated the effects of three stressors (drought, heat, and drought plus heat) at flowering phase (from tasseling to seed setting completed) on maize kernel filling in field site plots covered with a rainout shelter and under laboratory conditions with kernel in vitro culture. In two experiments, the kernel weight of plants exposed to flowering stressors was significantly decreased relative to controls. In the field experiment, exposure to stressors decreased kernel weight by 5.0–8.3% for the basal kernel and 5.6–11.0% for the apical kernel. Accelerated leaf senescence and decreased rate of photosynthesis were observed in the field. Kernel weight was also reduced by 18.0–37.6% in the laboratory with kernel in vitro culture, suggesting that early stressors at flowering led to a sink (kernel) limit. Carbohydrate metabolism and starch biosynthesis were impaired by drought and heat individually and their combination. During the early kernel filling stage, the activities of sucrose invertase, sucrose synthase, ADP-Glc pyrophosphorylase, and starch synthase were decreased at 10 and 20 days after pollination (DAP) in the stress treatment. For both basal and apical kernels, the correlation analyses indicated the mean kernel filling rate correlated positively with zeatin riboside content at DAP 10 and indole-3-acetic acid content at DAP 20. This study provides useful information to support the development of drought- and heat-tolerant hybrids and effective management strategies to improve crop yields.

干旱和开花时暴露在高温下会严重影响玉米产量。然而，以前的研究主要集中在压力源对内核数量的影响上。干旱和高温单独和开花期对玉米籽粒灌浆和最终籽粒重量的影响受到的关注有限。在这里，我们研究了开花阶段（从雄蕊到结实）的三种压力因素（干旱、高温和干旱加高温）对覆盖有雨棚的田间地块中的玉米籽粒填充的影响，以及在体外籽粒的实验室条件下文化。在两个实验中，与对照相比，暴露于开花压力源的植物的籽粒重量显着降低。在田间试验中，暴露于压力源使基部籽粒的籽粒重量减少了 5.0-8.3%，顶端籽粒的重量减少了 5.6-11.0%。在田间观察到叶片衰老加速和光合作用速率降低。在实验室中使用体外颗粒也使颗粒重量减少了 18.0-37.6%文化，表明开花时的早期压力因素导致汇（核）限制。碳水化合物代谢和淀粉生物合成分别受到干旱和高温及其组合的影响。在灌浆早期，在胁迫处理下授粉后10天和20天，蔗糖转化酶、蔗糖合酶、ADP-Glc焦磷酸化酶和淀粉合酶的活性降低。对于基部和顶端的籽粒，相关分析表明，平均籽粒灌浆率与 DAP 10 时的玉米素核苷含量和 DAP 20 时的吲哚-3-乙酸含量呈正相关。这项研究为支持干旱和干旱的发展提供了有用的信息。耐热杂交种和提高作物产量的有效管理策略。