SAN 9789: A Seed Dormancy Releasing Chemical

Abstract

The ability of the herbicide SAN 9789 to release primary as well as different forms of secondary dormancy in lettuce seeds (Lactuca sativa cv. Grand Rapids) was examined. Primary-, thermo-, osmo-, and far-red-dormant seeds treated with 28 μg/ml SAN 9789 in the dark at 25°C, germinated to 88, 61, 52 and 31 % respectively. The promotion of dark germination in primary dormant seeds by SAN after increased periods of pre-imbibition in water was gradually decreased and after 4 days disappeared. Brief red light (R), given either before or after 4 days of incubation with SAN resulted in full induction of germination in all these dormant seed types. The dark germination time courses of the different dormant seed categories immersed in 28 μg/ml SAN at 25°C, follows the final germination level pattern: The germination of the primary dormant seeds is faster and that of the far-red-dormant seeds slower. In thermoand osmo-dormant seeds, germination rates have intermediate values. SAN-promoted germination in primary dormant seeds proceeds through structural modifications of the endosperm tissue facing the radicle tip.