SEED STRUCTURE AND GERMINATION IN DISCARIA-TOUMATOU (RHAMNACEAE)

The anatomy and morphology of the seed of Discaria toumatou (Rhamnacea e), a native scrubweed, is briefly described. The testa has a tightly packed palisade layer of macrosclereid cells and associated linea luci da, features typical of those found in other hard-seeded species. Dorm ancy is demonstrated in freshly harvested seed. Stratification at 5 de grees C significantly increased germination when seeds were returned t o 20 degrees C but reduced imbibition when compared with seeds incubat ed at 20 degrees C throughout. Lengthier periods of stratification res ulted in greater rates of germination upon removal to 20 degrees C. Tr eatment with acetone, 95% ethanol or concentrated sulphuric acid prove d most effective in rendering the seed permeable. Imbibed seed showed maximum germination (96%) after 8 weeks continuous stratification at 5 degrees C, had an estimated frost tolerance (LT(50)) of -12 degrees C and germinated best at temperatures around 22 degrees C These results are consistent with the interpretation that Discaria toumatou seed po ssesses double dormancy of the kind involving coat imposed dormancy (o f the water impermeable type) and embryo dormancy of the kind overcome by stratification (5 degrees C) of imbibed seed.