THE INFLUENCE OF SEED SIZE VARIATION ON SEED-GERMINATION AND SEEDLING VIGOR IN DIPLOID AND TETRAPLOID DACTYLIS-GLOMERATA L

this study the effects of seed size variation on germination and seedling vigour have been investigated within and between ploidy levels of diploid and related autotetraploid Dactylis glomerata. Rates of seed germination and seedling growth were compared in two contrasting environments using diploid and tetraploid seeds of equal and also different biomass. Within each ploidy level, seed biomass had no effect on either the overall percentage nor the rate of germination. In contrast, the comparison of seeds of equal biomass but differing in ploidy level showed that seeds from tetraploid plants germinated faster and to a higher percentage than those from diploid plants. With respect to seedling growth, heavier seeds from the tetraploid genotypes gave seedlings of significantly higher biomass than those from lighter tetraploid and diploid seeds throughout the 2 months of study. Interestingly, seeds of equal biomass but from different ploidy levels produced seedlings more similar than those from the extreme seed weight categories. These differences were maintained in two different environmental conditions. These results suggest that there is a complex interdependance of seed size and ploidy on seed germination and seedling growth but is not a simple consequence of differences in seed size between diploids and their related tetraploids. (C) 1995 Annals of Botany Company