Correlations between Growth and Flowering in Chenopodium amaranticolor

Abstract

Vegetative plants of Chenopodium amaranticolor were induced to flower by exposure to 2, 6 or continuous short days (SDs) and the effect of such treatments on organogenesis at the apex of the main stem followed by means of dissections. The most outstanding responses to SD treatment were (I) an immediate elongation of the apex, (2) a stimulation of the rate of initiation of leaf primordia, and (3) a promotion of the rate of initiation of axillary bud primordia. In response to as few as 2 SDs, the rate of initiation of leaf primordia increased from 0.47 to a maximum of 3.70 per day and the rate of initiation of axillary bud primordia immediately increased from 0.47 to 1.35 per day. Precocious initiation of axillary bud primordia led to the formation of double ridges. The results indicate double ridges to be homologous with vegetative axillary buds; although they normally developed into reproductive tissues, they passed through a period of vegetative growth following minimal induction to flowering by exposure to 2 SDs. The rate and degree of flowering were highest in plants which received the longest period of SDs, but the differences in final flowering response were greater than the differences between the initial responses at the apices. The effect of SDs was thus not confined to an initial stimulation of organogenesis; a prolonged exposure to SDs must have enhanced the subsequent development of double ridges into flower primordia. The results are discussed in relation to previous findings and the general conclusion drawn that the initiation of double ridges is very widely accompanied by a stimulation of apical growth. It is suggested that inductive conditions remove a general growth inhibition and that the resultant stimulation of apical growth might lead to the initiation of double ridges.