Plant growth regulators in thermodormancy and germination of fruits of Lactuca sativa L. cv. 'Grand Rapids'

The aim of this research project has been to investigate the hormonal control of germination in light sensitive lettuce seeds. We have used the classic lettuce seed variety, Grand Rapids which, given suitable moisture conditions, will readily germinate below a critical temperature and not above that temperature. This 'thermo-dormancy' is known to be overcome by red light, mediated through phytochrome, and by a number of exogenously applied chemicals. Little information was available in the literature regarding the endogenous hormonal levels in lettuce seeds. It was decided to examine the involvement of endogenous hormones. Principally we have examined the levels of indole acetic acid and abscisic acid during imbibition at 2