EFFECT OF ACETONE ON THE INDUCTION AND BREAKAGE OF SECONDARY DORMANCY IN SEEDS OF CUCUMBER

The dark-germinating seeds of cucumber (Cucumis sativus L. cv. Saharanpur 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 of acetone, as well as an appreciable activity of the latter, irrespective of its application to dry or hydrated seeds, is consistent with the Taylorson hypothesis of anaesthetic action at the membrane level. Contrary to the general consensus that it is only the cells of the embryo which respond to an active dormancy-breaking factor, termination of dormancy as well as prevention of its development by acetone in cucumber seeds was accompanied by a striking change in the permeability of the cell membranes of the perisperm-endosperm envelope enclosing the embryo. This change in the permeability of the cell membranes brought about by acetone appeared to be permanent in nature as it was not affected by hydration or dehydration of the treated seeds.