Growth of ‘Grasslands Nui’ ryegrass after water and high temperature stress

Abstract

In cortrolled-environment experiments, ‘Grasslands Nui’ ryegrass (Lolium perenne L.) was held at ^—900 kPa leaf water potential for 14 days at 30^°/25^°c(day/night) and growth recovery was measured 14 days after relief of water stress at 20^°/15^°c. One experiment was a comparison with a lower temperature (20^°/15^°c) during water stress; two experiments compared effects of clipping all leaf, one of these at a greater stress of —2100 kPa leaf potential. At 30^°c compared with 20^°c there were no marked treatment differences; weight of living leaf tissue was unchanged during water stress, and weight of stem-plus-root tissues increased and numbers of tillers were unchanged. New leaf growth over a 7-day period after relief of water stress showed no significant effect of the previous treatment. Mean rate of leaf growth over 14 days from relief of water stress was lower for the previous 30^°c treatment. In one experiment, where all leaf was clipped just before water stress, growth of stem-plus-root tissues during water stress was less; in another experiment where water stress was more severe, both treatments were similarly affected. New leaf growth over a 7-day period after relief of water stress was less for the clipped treatment. Mean rate of leaf growth over 14 days from relief of water stress was similar for the clipped treatment, but the increase in numbers of tillers was less. Soluble carbohydrate content in stem tissues of clipped plants was lower during water stress, but increased in control plants. After rewatering, there was a marked decrease in soluble carbohydrate content in stem tissues, and contents had not regained their previous levels 14 days later.