Effects of Gibberellin, Kinetin, Thiourea, and Photomorphogenic Radiation on Mitotic Activity in Dormant Lettuce Seed

Abstract

Lettuce seed germination can be stimulated, probably by distinct mechanisms, by any of the three widely studied morphogenic agents: gibberellin, kinetin, or red light (11). It has been shown that cellular expansion is both necessary and sufficient and that cell division is neither necessary nor sufficient for the initiation of lettuce seed germination (8). Thus it is now possible to study the effects of germinationstimulating agents on mitotic activity in embryos uncomplicated by germination and growth from expansion. In this paper, mitotic activity as it is affected by gibberellic acid (GA), kinetin, and light, as well as by thiourea, which also stimulates germination of lettuce seed (28), is studied.