Abstract
Field observations showed that small plants often have lower female investment than
large plants. Field-collected data do not elucidate, however, whether 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 genotypic differences between small
and large plants. Therefore, the relationship between plant mass and flower and seed
production was measured under favourable conditions using fullsibs and clones of Cynoglossum officinale. The aim of this study is to determine if the pattern of size-dependent gender 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 mass compared
to large plants. On the other hand, seed production per unit plant mass did not significantly
differ between plants of different sizes. As a result, the number of seeds per flower
increased with increasing plant mass, large plants produced 1.5 times more seeds per
flower compared to small plants. Thus small plants emphasize the male side, whereas
large plants emphasize the female side of production. We conclude that, even under
favourable environmental conditions, all genotypes examined maintain size-dependent
sex allocation (SDS).
When analysed separately, we found no genetic variation in seed production among genotypes
(full sibs and clones). In contrast, genotypes differed significantly in flower production.
Neither the number of seeds per gram plant mass nor per flower differed significantly
among genotypes. In our experiment no evidence was found for a negative genetic correlation
between flower production per unit plant mass and seed production per unit plant mass.
Key words
Cynoglossum officinale
- flower and seed production - genetic variation - size-dependent sex allocation (SDS)
