Studies on the Growth of the Barley Apex I. Interrelationships Between Primordium Formation, Apex Length, .and Spikelet Development

Abstract

A detailed study has been made of the morphology of the spring-barley apex from shortly after germination to shortly before heading. The effects of 8- and 24-hr light periods and three levels of soil-moisture tension were examined with reference to the total number of primordia initiated on the main stem, the length of the apex, and the rate of spikelet development. For the environmental conditions explored it was found that the initiation of double ridges occurred when the apex was a particular length (0.45 mm), and that the initiation of internode elongation, the appearance of stamen initials on the most advanced spikelet, and the cessation of primordia formation occurred concurrently.