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

The ecological mechanism underlying nocturnal stomatal conductance (g ) in C and C plants remains elusive. In this study, we proposed a 'coordinated leaf trait' hypothesis to explain g in rice plants. We conducted an open-field experiment by applying drought, nutrient stress and the combined drought-nutrient stress. We found that g was neither strongly reduced by drought nor consistently increased by nutrient stress. With the aforementioned multiple abiotic stressors considered as random effects, g exhibited a strong positive correlation with dark respiration (R ). Notably, g 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 -derived transpiration. However, our results clearly suggest that evaporative cooling did not reduce dark respiration cost. Our results indicate that g is more closely related to carbon respiration and assimilation than water and nutrient availability, and that dark respiration can explain considerable variation of g .