Inflorescence Initiation in Lolium Temulentum L. IV. Translocation of the Floral Stthiulus in Relation to that of Assimilates

Abstract

Translocation of labelled assimilates to the shoot apex and other parts of the plant was followed from an upper leaf held in long-day conditions, when lower leaves in short days were either present or removed. Similarly a comparison was made of the distribution of assimilates from an upper long-day leaf and a lower leaf held in short days. The presence of lower leaves did not reduce the movement of assimilates from the upper leaf to the shoot apex, and the lower leaf supplied only a small proportion of the assimilates reaching the shoot apex, although it supplied much to the roots. It is concluded that the previously established inhibitory effect of lower leaves in short days on inflorescence initiation in L. temulentum is unlikely to be due to their interference with translocation of the long-day stimulus to the shoot apex, or to their diluting it with assimilates, but rather to their production of a transmissible inhibitor of initiation.