Understanding the physiological mechanisms that control drought tolerance in crop plants is vital for effective breeding. In this study, we characterized drought stress responses in four sorghum cultivars exhibiting differential levels of drought tolerance at pre- and post-anthesis. Greenhouse-grown plants were subjected to two types of drought treatment, water stress (WS) and desiccant-induced water stress (DA), timed to occur at pre- and post-anthesis. Multiple physiological measurements were then made revealing varying responses among the experimental cultivars. The pre- and post-flowering drought-tolerant cultivar P898012 showed a significantly higher net photosynthetic rate, higher transpiration rate, and greater stomatal conductance compared to the drought-susceptible cultivars at both pre- and post-anthesis. A significantly greater stomatal size was also detected in P898012, while the highest stomatal density was found in the drought-susceptible cultivar P721Q. Meanwhile, the two post-flowering drought-tolerant cultivars P898082 and B35 had a higher starch content and exhibited greater osmotic potential under post-anthesis water stress. Compared to WS and well-watered control plants, a greater increase in root biomass was observed in P898012 under DA at pre-anthesis. This finding suggests that plants invested more assimilates into the roots under severe DA at pre-anthesis. Overall, our results show good conformity between drought tolerance in sorghum and key physiological mechanisms of stomatal conductance, root growth patterns, and starch accumulation, all of which act as coping mechanisms during critical drought-sensitive growth stages.

中文翻译：

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花前和花后干旱条件下耐旱和易感高粱品种的生理形态、生化和解剖学特征

了解控制作物耐旱性的生理机制对于有效育种至关重要。在这项研究中，我们表征了在开花前和开花后表现出不同水平的耐旱性的四个高粱品种的干旱胁迫反应。温室种植的植物受到两种类型的干旱处理，水分胁迫 (WS) 和干燥剂诱导的水分胁迫 (DA)，定时发生在开花前和开花后。然后进行了多项生理测量，揭示了实验品种之间的不同反应。与耐旱品种相比，开花前和开花后耐旱品种 P898012 在花前和花后均表现出显着更高的净光合速率、更高的蒸腾速率和更大的气孔导度。在 P898012 中也检测到明显更大的气孔大小，而在易受干旱影响的品种 P721Q 中发现了最高的气孔密度。同时，两个开花后耐旱品种 P898082 和 B35 具有更高的淀粉含量，并在花后水分胁迫下表现出更大的渗透势。与 WS 和浇水充足的对照植物相比，在开花前在 DA 下观察到 P898012 的根生物量有更大的增加。这一发现表明，在开花前的严重 DA 下，植物将更多的同化物投入到根中。总体而言，我们的结果表明高粱的耐旱性与气孔导度、根生长模式和淀粉积累的关键生理机制之间具有良好的一致性，所有这些都在关键的干旱敏感生长阶段充当应对机制。