Temperature affects germination, mesocotyl length and coleoptile length of oats genotypes

Abstract

Seedlings of 16 oats genotypes (Algerian, Amby, Bulban, Cluan, Culgoa, Echidna, MA5030, Minhafer, Moore, Mortlock, Panorama 5, Riel, Saia, Stout, West and 81Ab1063) were allowed to elongate in darkness at six constant temperatures (10, 15, 20, 25, 30 and 35¦C) to determine the effect of temperature on final mesocotyl and coleoptile length. The optimum temperature for maximum mesocotyl+coleoptile length (potential maximum sowing depth) was 15¦C. Potential sowing depth at 10 to 25¦C was always large (113 to 252 mm) but there was a decline with increase in temperature above 20¦C. The decline was due to reduced coleoptile length rather than reduced mesocotyl length. Temperaturexgenotype interactions were significant (P < 0.01) but all cultivars showed a similar general trend in response to temperature. Shoots, but not necessarily the primary roots, failed to emerge from the seeds of any genotype at a constant temperature of 35¦C. When the temperature was subsequently reduced to 20¦C, however, shoot emergence took place. Poor field emergence of early sowings may be related to such temporary cessation of the germination process at high temperatures. Reduced seedling elongation at high temperature may also be involved. The wide variation at 30¦C in germination percentage (8 to 100%) and seedling elongation (55 to 126 mm) suggested a genetic solution to the problem of poor emergence at moderately high soil temperatures. Germination and seedling elongation at 30¦C were postively correlated. There were no significant (P > 0.05) correlations between mature plant height or seed weight with mesocotyl length, coleoptile length or potential maximum sowing depth.