EFFECT OF ACETONE ON THE INDUCTION AND BREAKAGE OF SECONDARY DORMANCYIN SEEDS OF CUCUMBER

The dark-germinating seeds of cucumber (Cucumis sativus L. cv. Saharan pur Long green) developed secondary dormancy when given two brief far- red light (FR) irradiations during a 4 d incubation in osmoticum at 20 -degrees-C. Acetone treatment of seeds was found not only to break FR- induced dormancy but also to prevent its development. The progressive effect of increasing the duration of treatment or the concentrations o f acetone, as well as an appreciable activity of the latter, irrespect ive of its application to dry or hydrated seeds, is consistent with th e Taylorson hypothesis of anaesthetic action at the membrane level. Co ntrary to the general consensus that it is only the cells of the embry o which respond to an active dormancy-breaking factor, termination of dormancy as well as prevention of its development by acetone in cucumb er seeds was accompanied by a striking change in the permeability of t he cell membranes of the perisperm-endosperm envelope enclosing the em bryo. This change in the permeability of the cell membranes brought ab out by acetone appeared to be permanent in nature as it was not affect ed by hydration or dehydration of the treated seeds.