Effect of temperature on cold dehardening of Lolium perenne L. seedlings

Abstract

SUMMARYCold dehardening responses of seedlings of three cultivars of Lolium perenne L. (Premo, S.23 and Grasslands Ruanui) were studied in different temperature regimes following hardening at 2 °C. Seedlings of the three cultivars dehardened rapidly at 15 °C after partial hardening for 4 days, whereas there was a lag before dehardening occurred in seedlings of Premo and S.23 which were hardened for 28 days. At 10 °C dehardening did not occur in Premo and S.23 and occurred only slowly in Grasslands Ruanui. Alternating temperature regimes of 15 °C(day): 2 °C (night) gave increased levels of hardiness when the daily period of exposure to 15 °C was 8 h but only maintained the level of hardiness when it was extended to 16 h.A tentative scheme of threshold temperatures for hardening and dehardening is proposed.