Abstract
This study examined how the root temperature affects water uptake and transpiration of rice plants (Oryza sativa L.). Over a range of root temperature, TR from 35 to 13 oC, transpiration ET and the leaf water potential ΨL gradually decreased with decreasing TR. Below a critical root temperature 13 oC, ET and ΨL abruptly decreased with decreasing TR, which is due to an abrupt decrease in hydraulic conductance of plants. The bulk stomatal conductance of whole plants under experimental conditions was expressed as a unique function of only ΨL. Using the experimental result, we constructed a model for water uptake and transpiration of rice plants, which consists of the energy balance equation for plant leaves and the water transport equation by the root. We also found the possibility that the reduction in the activity of aquaporins causes a decrease in hydraulic conductance of plants at low root temperatures.
