Dark respiration explains nocturnal stomatal conductance in rice regardless of drought and nutrient stress

Abstract

The ecological mechanism underlying nocturnal stomatal conductance (g_sn) in C₃ and C₄ plants remains elusive. In this study, we proposed a ‘coordinated leaf trait’ hypothesis to explain g_sn in rice plants. We conducted an open‐field experiment by applying drought, nutrient stress and the combined drought–nutrient stress. We found that g_sn was neither strongly reduced by drought nor consistently increased by nutrient stress. With the aforementioned multiple abiotic stressors considered as random effects, g_sn exhibited a strong positive correlation with dark respiration (R_n). Notably, g_sn primed early morning (5:00–7:00) photosynthesis through faster stomatal response time. This photosynthesis priming effect diminished after mid‐morning (9:00). Leaves were cooled by g_sn‐derived transpiration. However, our results clearly suggest that evaporative cooling did not reduce dark respiration cost. Our results indicate that g_sn is more closely related to carbon respiration and assimilation than water and nutrient availability, and that dark respiration can explain considerable variation of g_sn.