Selective fruit and seed maturation in Asphodelus albus Miller (Liliaceae).
The fruiting patterns of the rhizomatous perennial Asphodelus albus Miller (Liliaceae) were studied in five populations during 1989 and in one population over 3 years (1988-1990). Fruit/flower (Fr/Fl) ratio and seed/ovule (S/O) ratio varied markedly between populations. Although there were differences between years within the population studied over 3 years, these variations, although statistically signifcant, were less important than those between populations. Neither flowering phenology nor plant size influenced Fr/Fl or S/O ratios. Field experiments tested whether fruit and seed set were pollenor resource-limited. Hand-pollination had no effect on Fr/Fl or S/O ratios, but the reduction of resources by defoliation at the time of flowering decreased both relative components of fecundity. Manipulation of resources by hand-thinning flowers and tiny fruits had no demonstrable effect on these ratios, although brood size of individual fruits was significantly affected. It may be concluded that fruit maturation is resource-limited rather than pollen-limited. Most of the fruits aborted early in the fruiting season, and fruits with higher numbers of developing seeds had a lower probability of abortion than fruits with fewer seeds. Analyses of position effects revealed that the fruits in lower positions in the inflorescence matured preferentially. Furthermore, the two ovules in the same carpel tended either both to fail or both to develop into seeds. The plant's ability to selectively mature only high quality embryos may be limited.
Department of Biología Organismos y Sistemas, Unidad de Ecología, Universidad de Oviedo, E-33005, Oviedo, Spain.
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JR
Obeso
Asphodelus albus; Brood size; Fruit/flower ratio; Position effect; Seed/ovule ratio