INFLUENCE OF DROUGHT AND FLOWERING ON GROWTH AND WATER RELATIONS OF PERENNIAL RYEGRASS POPULATIONS

Spring‐sown (vegetative) and autumn‐sown (flowering) swards of Lolium perenne cvs Melle, Aurora and their hybrid growing in 0.9 m deep bins of soil in the glasshouse were compared, a) as drought progressed from June to August 1986, and b) after cutting, fertilising and re‐watering. During drought, vegetative plants produced more herbage, had initially higher leaf extension rates, had longer and wider leaves, maintained more tillers, had lower mortality, adjusted osmotic potential more effectively and had stomata less sensitive to stress than did flowering plants. On re‐watering, previously stressed flowering plants regrew more slowly than the irrigated controls, whereas previously stressed vegetative plants regrew more rapidly than the controls. Aurora was the most drought‐resistant population, mainly because of low tiller death rates. The hybrid tended to have the lowest leaf water potentials and conductances and grew poorly during drought. Possible underlying physiological mechanisms are discussed. Copyright © 1990, Wiley Blackwell. All rights reserved