Unraveling space and time variability in maximum water storage among sunflower organs: Implications for wetness duration

Abstract

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 he capitulum front. The area of leaves, stems, and capitula during the flowering stage had a greater impact ontheir 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.