Differential contribution of avoidance and tolerance to dehydration resistance in populations of perennial ryegrass, Lolium perenne L.

Abstract

The mechanisms of a plant to resist water stress can be divided into 2 components: avoidance and tolerance. However, reliable methods for measuring these components have not been established. We qualitatively evaluated the avoidance and tolerance abilities of shoots in diploid and tetraploid populations of perennial ryegrass (Lolium perenne L.) by continuously measuring their water contents and mortality rates under severe dehydration stress. Plant age greatly influenced dehydration resistance. Younger (30 days old) plants showed lower resistance to dehydration stress than did older plants (60 days old) because of both their lower avoidance and tolerance abilities. The two populations showed contrasting patterns of response to dehydration stress. The tetraploid population (Condesa) had higher avoidance and lower tolerance than did the diploid population (Manhattan II), and different combinations of the 2 components resulted in similar degrees of resistance in the 2 populations. The results of experiments demonstrated the importance of distinction between avoidance and tolerance abilities for studies on plant water stress.