Phytochrome et germination des semences de Rumex

The Rumex alpinus L. achenes show a special type of positive photosensitivity: several red light irradiations are necessary to induce optimal germination. The achenes deprived of their pericarp lose their photosensitivity and germinate readily in the dark. By spectrophotometry in vivo, the presence of the Pr form of phytochrome is revealed in these seeds. Short periods at extreme temperatures (30°C or 5°C) induce a good proportion of achenes to germinate. The gibberellins are inefficient on achene germination contrary to benzyladenine which exhibits some activity. A slight improvement of GA4 effects has been detected on scarified fruits.