Pollen: ovule ratio and its relation with other reproductive traits in some Passiflora species (Passifloraceae)

AMELA GARCÍA, M. T.; MIGUEZ, M. B.; GOTTSBERGER, G.

ANALES DEL JARDíN BOTáNICO DE MADRID

CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS

Lugar: Madrid; Año: 2014 vol. 71

0211-1322

The pollen/ovule (P/O) ratio has been used as predictor of the reproductivesystem of angiosperms (lowest P/O values correspond to obligateautogamous species while the highest correlate with obligate xenogamous species) but it does not keep for all the taxa. The relation of P/O index with pollen and stigma size, flower diameter, pollen vitality,stigmatic area/pollen-bearing area of the pollinators ratio (SA/PBA), taxonomy and breeding system was analyzed in four Passiflora species with different degree of compatibility, pollination system and taxonomic placement. P/O of the self-compatible species (with shorter anthesis, scarce pollinator visits or minor longevity) was lower than P/O of the self-incompatible ones. The P/O values of the outcrossers could be related with the highly efficient pollination performed by the frequently visitingXylocopa species; these bees transport Passiflora pollen in a usually monospecific mass on the thorax, resembling grouped pollen dispersal. All the taxa exhibited pollen with unimodal size and high vitality, except for P. misera, in which pollen size was bimodal, with similar quantities of grains in both classes, the large being more vital than the small ones. Correlations of P/O were positive with flower size, negative with stigma area/pollen-bearing area of the pollinator, null with stigma area and not significant with pollen size. The P/O ratio did not reflect taxonomic affinities;this index and the breeding system were more related with pollinatortype, anthesis, flower size and SA/PBA than with pollen grain or stigma size.