Evidence for Selective Embryo Abortion in Cryptantha flava

In each ovary of Cryptantha flava, three of the four ovules usually fail to develop, even though all of them may be fertilized. I tested the hypothesis that ovules with more-vigorous embryos selectively mature. Following fertilization but before ovule abortion, three arbitrarily selected ovules were destroyed in each of 1970 (experimental) flowers. The performance of offspring produced by these flowers was compared with the performance of offspring from control flowers in which any one of the four ovules could develop. In the control flowers, when one ovule was just larger than the others, the other three ovules were destroyed. The seeds resulting from both treatments were planted near their source plants at several locations in the field. Emergence, seedling survival, and seedling size were monitored through two growing seasons. Less emergence occurred in seeds produced by the experimental treatment than in control seeds, but seedling survival during the first year did not differ significantly. Overall survival from planting was greater for the controls in both years. Plant height and the number of leaves per plant did not differ between treatments for either year. For all measures of success, there were significant differences among sites and, for some, significant treatment-by-site interactions. The results are consistent with the selective maturation of higher-quality embryos, but alternative explanations are also given.