Effects of ovule and seed abortion on brood size and fruit costs in a leguminous shrub

CALVIÑO, ANA

ACTA BOTANICA BRASILICA

SOC BOTANICA BRASIL

Lugar: San Pablo; Año: 2013

0102-3306

For several plant species, brood size results from the abortion of ovules and seeds; however, these processes have been rarely studied together in wild plants. Seed abortion was found to depend on pollen quality and ovule or fruit position in some leguminous species studied, and the direct consequence for the mother plant was found to be an increase in fruit costs with decreasing seed:ovule ratio. However, because ovule abortion occurs earlier than seed abortion, it may reduce the biomass invested per unit seed (i.e., fruit costs) more efficiently. Here, the frequency of aborted ovules and seeds was analyzed in relation to pollination treatment (open- vs. hand cross-pollination) and ovule and fruit position within pods of the leguminous shrub Caesalpinia gilliesii. The influence of ovule and seed abortion on fruit costs was analyzed by comparing the pericarp mass per unit seed between fruits with different frequency of aborted ovules and seeds. Ovule abortion was similar between hand cross- and open-pollinated fruits, but was more frequent than seed abortion in one- and two-seeded fruits, and also in stylar positions and distal fruits. Hand cross-pollination reduced seed abortion but failed to increase seed:ovule ratio. In addition, fruits that aborted ovules were less costly than fruits that aborted seeds. From the mother plant perspective, these results indicate that ovule abortion is a more efficient mechanism than seed abortion in reducing fruit costs as fertilization opportunities decrease with position, and shows that brood size is significantly influenced by the fate of the ovule at the pre-zygotic stage.