Effect of constant and fluctuating temperature regimes and seed source on the coleoptile length of tall and semidwarf wheats

Abstract

Laboratory experiments were carried out to determine the effects of constant and fluctuating temperature regimes on the final coleoptile length of 8 wheat cultivars (Banks, Cook, Gatcher, Hartog, Kite, Oxley, Shortim and Spica) and the effect of environmental conditions during seed maturation (seed source) on the coleoptile length of 5 cultivars (Banks, Bass, Cook, Kite and Oxley). Mean coleoptile length decreased from 10.8 cm at 15�C to only 3.1 cm at 35�C, a reduction within this temperature range of 1 cm for every 2.6�C rise in temperature. This indicates that, in warm soil, shallow sowing is necessary for satisfactory wheat establishment. Fluctuating temperatures (� 5�C about the mean) further reduced coleoptile length. The temperature x cultivar interaction was significant, differences among cultivars in coleoptile length occurring more at low than at high temperatures. The mean coleoptile lengths of the 8 cultivars varied from 8.7 to 14.5 cm at 15�C, but only from 2.7 to 3.6 cm at 35�C. Tall wheat cultivars (Gatcher and Spica) generally had longer coleoptiles than the 6 semidwarf cultivars. Tall wheats also had near-maximum coleoptile length at a wider range of temperatures than semidwarfs. Different environmental conditions during seed maturation (glasshouse v. field) changed the ranking of cultivars with respect to coleoptile length. The coleoptiles of Cook and Oxley were significantly longer when seed was field-ripened rather than glasshouse ripened, while those of Banks, Bass and Kite were similar in length under both ripening environments.