| Abstract: | A new plant cohort starts with the formation of zygotes at ovule fertilization. This paper presents an ecological study of the effects of resource limitation and pollen donor on the survivorship and size of plant embryos in maturing fruits of the common bean, Phaseolus vulgaris L. For naturally selfed flowers of domesticated and wild beans, embryos in basal ovular positions were more likely to abort or, if they survived, become lighter seeds than stylar embryos. Embryo survivorship was higher for the cultivar when maternal plants grew in larger pots. Early seed abortion in the cultivar was random with respect to ovular position. In late abortion basal embryos had a higher mortality than stylar ones. The basal embryos lacked gross genetic defects since they developed adult organs in embryo culture. In more outbred crosses with the cultivar the position effect in embryo survivorship and size disappeared. This difference among paternal parents implicates a genetic component to the observed position effects. The variation in mature seed size may affect adult characteristics since large seeds produced larger juvenile plants than small seeds. |
