Studies on the Growth of the Barley Apex

Abstract

The processes of cell division and cell elongation were examined in the pith of the rachis of the barley inflorescence from the time double ridges first appeared until shortly before ear emergence for plants grown under continuous illumination. Estimates of the concentration of gibberellin-like substances in inflorescences were also made at three stages of development for barley plants grown under both continuous illumination and 8-hr light periods. The highest concentration of gibberellin-like substances coincided with the initiation of cell division in the pith region, while at the same time stamen initials first appeared and internode elongation in the inflorescence began. In the light of these findings tentative suggestions are made about the role of gibberellins in the growth of long-day plants.