Rapid Leaf Growth in Wheat and Its Links With Flowering

Abstract

Recent papers have proposed that rapid leaf growth in pasture grasses in spring is linked with the switch from vegetative to floral development. The paper examines this possible link in wheat using various photoperiodic treatments and isolines with different vernalisation requirements to induce floral initiation at several plant ages. The findings were as follows. (1) Induction of floral initiation by 3 long days at any plant age resulted in accelerated leaf expansion and relative growth rate of the whole plant. The effects were on shoots alone. (2) At equivalent plant age, when a winter isoline had no signs of double ridges, and so was apparently vegetative, and a spring isoline was clearly floral, whole-plant relative leaf expansion rates were not significantly different between isolines though tillering was much less in the spring line. (3) Photoperiodic treatments which were not sufficient to induce floral development irreversibly resulted in ephemeral increases in leaf expansion rate. These increases were followed by compensatory reductions. These data suggest that rapid leaf expansion and floral development are not linked, although both can be initiated by extended photoperiods rich in far-red radiation. The relevance of these findings to the selection of wheat genotypes with rapid early growth is discussed.