Data from: Manifold limits on seed production by individual flowering plants

Premise: Historically, angiosperm seed production has been considered to
be either pollen or resource limited. However, seed production involves
more than pollen and seed resources and typically involves multiple ovules
in multiple flowers. Therefore, various constraints may act
simultaneously. Methods: Proportional components of seed production were
assessed for rapid-cycling Brassica rapa plants on which 25, 50, 75 or
100% of flowers were hand outcrossed. Results: Fruit set increased in a
decelerating manner with the percentage of pollinated flowers. For all
treatments, only flowers pollinated early on plants produced fruit,
although the transition to complete fruiting failure was delayed on poorly
pollinated plants. Despite stigmas receiving abundant pollen, only 61% of
ovules in pollinated flowers were fertilized, on average. Fertilization
success varied within ovaries, with more fertilization of apical ovules in
flowers on plants with 75% of pollinated flowers, but more fertilization
of basal ovules with 25% pollination.  Per-flower fertilization
also varied positively with ovule number and the number of basal fruits,
and negatively with flower position. Almost all fertilized ovules
developed into seeds, so variation in seed set depended primarily on the
effects on ovule fertilization. Conclusions: Regardless of pollination
treatment, seed production by all plants was jointly limited by both
pollen and availability of seed resources, and possibly by ovule
infertility/receptivity. A simple model demonstrates that such
co-limitation can be adaptive if plants produce excess flowers.
Interacting effects of the proportion of pollinated flowers and anthesis
day on fruit set are consistent with hormonal mediation of resource
distribution among fruits.