Flower initiation in relation to maturity in crop plants. II. Internode lengthening in relation to grazing in oat varieties

Abstract

Experience has shown that certain oat varieties recover better than others after grazing. Sowings at, Melbourne in autumn 1958 and 1959 confirm that the varieties with superior recovery usually commence internode lengthening later than those with poor recox7ery. Poor recovery is due to damage of the main shoot caused by grazing after internode lengthening has begun. Factors which affect the time of internode lengthening include flower initiation and the time of sowing. In sowings between May and November (late autumn to late spring) elongation begins at or soon after initiation. It therefore occurs earlier in the early-maturing varieties (which initiate earlier) than in later ones. In sowings between December and April, some varieties, especially within the late maturity group, begin internode elongation before initiation. This reaction can be produced experimentally by high temperatures, especially when combined with photoperiods below 15 hr. In the selection of varieties for grazing, the factors to be considered are: (a) the length of growing season; (b) the time at which, and period over which, grazing is required; (c) the extent to which recovery after grazing is important. If a high total yield from a number of grazings is required, a variety with delayed internode lengthening should be chosen, the particular one selected being from a maturity group suited to the local growing season. However, if early grazing is required, a variety with rapid internode lengthening d l probably prove to be a better choice even though grazing may be at the expense of subsequent recovery.