Size-dependent sex allocation in Cynoglossum officinale for different genotypes under uniform favourable conditions

Field observations showed that small plants often have lower female investm ent than large plants. Field-collected data do not elucidate, however, whet her this pattern is an inherent effect of size or if it is caused by poorer environmental quality of sites where small plants are growing and/or by ge notypic differences between small and large plants. Therefore, the relation ship between plant mass and flower and seed production was measured under f avourable conditions using full-sibs and clones of Cynoglossum officinale. The aim of this study is to determine if the pattern of size-dependent gend er was maintained if both small and large plants are grown under favourable conditions, and if this pattern is consistent among genotypes. Over all genotypes, smaller plants produced more flowers per unit plant mas s compared to large plants. On the other hand, seed production per unit pla nt mass did not significantly differ between plants of different sizes. As a result, the number of seeds per flower increased with increasing plant ma ss, large plants produced 1.5 times more seeds per flower compared to small plants. Thus small plants emphasize the male side, whereas large plants em phasize the female side of production. We conclude that, even under favoura ble environmental conditions, all genotypes examined maintain size-dependen t sex allocation(SDS). When analysed separately, we found no genetic variation in seed production among genotypes (full sibs and clones). In contrast, genotypes differed sig nificantly in flower production. Neither the number of seeds per gram plant mass nor per flower differed significantly among genotypes. In our experim ent no evidence was found for a negative genetic correlation between flower production per unit plant mass and seed production per unit plant mass.