Sex‐Specific Dynamics of Surface Water Storage and Their Relationship With Drought Resistance in Dioecious <scp> <i>Spinacia oleracea</i> </scp>

ABSTRACT Plant surface water storage (PWS) greatly affects canopy rainfall interception and thus has a significant impact on water availability for plants under drought conditions. However, it remains unclear whether the responses of PWS characteristics of dioecious plants exhibit sexual dimorphism under drought stress and how these responses relate to plants' drought resistance. To this end, the impact of drought on the PWS characteristics, related leaf traits and biomass accumulation of Spinacia oleracea males and females was investigated. Under normal water conditions, PWS per unit total dry weight and per unit leaf area of females were 52.8% and 42.1% lower than those of males, respectively, indicating a potentially higher PWS efficiency of males. Under drought conditions, PWS per unit total dry weight and per unit leaf area in males decreased significantly by 24.9% and 62.7%, respectively, while those in females remained unchanged, implying greater sensitivity of males' PWS efficiency to drought. The PWS capacities of the stem, leaves and entire plant were similar between males and females under normal water conditions, but the males exhibited a greater reduction under drought. Female plants showed a 20.4% lower reduction in leaf dry weight and a stronger increase in leaf density under drought than males, reflecting stronger drought resistance in females. Analysis based on leaf hydraulic characteristics suggested that both sexes might enhance their foliar water uptake, as indicated by larger contact area of water drop on leaf surface due to improved leaf wettability (lower leaf contact angles) and better structural basis for foliar water absorption due to higher leaf succulence indexes under drought. However, females might benefit more from these adaptations due to their undiminished PWS efficiency. These results suggested that deriving greater benefits from foliar water uptake through maintaining stable rather than decreased PWS efficiency may be one of the reasons why female S. oleracea plants exhibit stronger drought resistance than the males.