Vegetation wetness significantly alters the plant microclimate, thereby influencing plant functionality, growth, and yield. Prolonged wetness periods can exacerbate the risk of attack of various plant diseases. Maximum water storage capacity is a crucial parameter for modeling wetness duration, as it sets the upper limit for free water available for evaporation. This study aimed to achieve three main goals: (i) to investigate the maximum water storage capacity of distinct sunflower organs (leaves, stems, and capitula) and their constituent phytoelements, (ii) to establish relationships between maximum water storage and visible morphological characteristics, and (iii) to assess the impact of maximum water storage on phytoelement wetness duration. Morphological and micrometeorological measurements were conducted within a sunflower field plot. Maximum water storage capacity was determined in the laboratory using phytoelements collected from the field. For the capitula and its constituent phytoelements, this capacity was monitored throughout their development. Phytoelement size and orientation were quantified and correlated with their water storage capacity. The influence of phytoelement maximum water storage on wetness duration was investigated through simulation. Notably, we found that the maximum water storage capacity in leaf axils exceeded those in leaf lamina by 43 times. During the flowering and grain-filling stages, capitula exhibited greater water storage, primarily attributed to the contribution from the capitulum front. The area of leaves, stems, and capitula during the flowering stage had a greater impact on their maximum water storage capacity than their orientation. Simulation results revealed that certain phytoelements (e.g., leaf axils and capitulum disk) could remain wet for up to 20 h after most of the canopy, mainly leaves and stems, had dried. This study underscores the importance of examining variability in maximum water storage capacity and its impact on wetness duration within a sunflower canopy at the phytoelement level.

中文翻译：

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揭示向日葵器官最大储水量的空间和时间变化：对湿润持续时间的影响


植被湿度显着改变植物小气候，从而影响植物功能、生长和产量。长时间的潮湿会加剧各种植物病害的发病风险。最大储水容量是模拟湿润持续时间的关键参数，因为它设定了可蒸发的自由水的上限。本研究旨在实现三个主要目标：（i）研究不同向日葵器官（叶、茎和头状花序）的最大储水能力及其组成植物元素，（ii）建立最大储水量与可见形态特征之间的关系，以及 (iii) 评估最大水储存量对植物元素湿润持续时间的影响。在向日葵田块内进行了形态学和微气象学测量。最大储水能力是在实验室中使用从田间收集的植物元素确定的。对于头状花序及其组成的植物元素，这种能力在其整个发育过程中受到监测。植物元素的大小和方向被量化并与其储水能力相关。通过模拟研究了植物元素最大储水量对湿润持续时间的影响。值得注意的是，我们发现叶腋的最大储水能力是叶叶片的43倍。在开花和灌浆阶段，头状花序表现出更大的储水量，这主要归因于头状花序前部的贡献。开花期叶、茎和头状花序的面积对其最大储水能力的影响大于其方向的影响。模拟结果表明某些植物元素（例如在大部分冠层（主要是叶子和茎）干燥后，（叶腋和头状花序盘）可以保持湿润长达 20 小时。这项研究强调了在植物元素水平上检查最大储水能力的变异性及其对向日葵冠层湿润持续时间的影响的重要性。