SEED DORMANCY IN MEDITERRANEAN SENECIO-VULGARIS L

Fresh seed derived from a Mediterranean population of non-radiate Senecio vulgaris L. showed strong innate dormancy over a wide temperature range. In contrast, fresh seed of British S. vulgaris exhibited > 80% germination at 20-degrees-C. Dormancy in Mediterranean seed was overcome by: prolonged storage at 15-degrees-C and above; a short stratification treatment (2 wk at 4-degrees-C); prolonged leaching with water; treatment with gibberellic acid (GA3) alone (and with kinetin); and to a lesser extent, by wounding (i.e. removal of a small portion of the fruit and seed coat). A petroleum ether extract from fresh Mediterranean seed strongly inhibited the germination of previously non-dormant seed (of British origin). This implies that dormancy may be caused by an inhibitor present in the embryo or seed coat which might act by preventing the synthesis or liberation of gibberellins required for germination. The innate dormancy exhibited by seed of non-radiate Mediterranean S. vulgaris, enables the species to adopt a winter annual life cycle which is typical of Mediterranean ephemerals.