Phytochrome-mediated germination control of Hygrophila auriculata seeds following dry storage augmented by temperature pulse, hormones, anaerobiosis or osmoticum imbibition

Abstract

A pulse of red light ( R) stimulates, and far-red light ( FR) inhibits germination of Hygrophila auriculata seeds with primary dormancy. These seeds lose their light requirement for germination after 4 months of dry storage in air. A secondary dormancy can then be induced by 5-day dark imbition in osmoticum in air (21% O 2). Red light will break this dormancy. Seeds stored in nitrogen gas (0% O 2) neither lose the light requirement, nor is a secondary dormancy imposed. However, FR stimulated some germination in osmoticum-induced dormant seeds is evident when such seeds are given a 1–6 hr 40°C pulse, gibberellin A 3 (GA 3), or ethylene treatments. These results suggest that changes of photosensitivity from a low fluence response to a very low fluence response may occur concurrently with the status of dormancy in seeds. The processes of dry after-ripening, the induction of secondary dormancy or of photosensitivity all require oxygen.