A quick determination of root resistance to water transport in paddy rice

Abstract

Hydraulic resistance in plants is one of the most important factors responsible for changes in leaf water potential that is an indicator of plant water stress. Although the hydraulic resistance to passive water transport (Rpa) is a robust index in paddy rice (Oryza sativa), measurement is both time-consuming and labour-intensive. Here, we describe on a quick method to measure hydraulic resistance to osmotic water transport (Ros) by measuring the xylem sap exudation rate and osmotic water potential. In a greenhouse experiment, Ros responded significantly to soil temperature, but under field conditions soil temperature varied considerably less than air temperature. In the field experiment, Ros of six rice cultivars at two growth stages was strongly positively correlated with Rpa. We conclude that measuring Ros could be used to evaluate root water transport capacity in paddy rice under conditions with adequate soil water.