Embryology of early abortion due to limited maternal resources in Pisum sativum L

In most flowering plants, many embryos are aborted early in their development due to limited maternal resources. The kin-conflict interpretation of plant embryology predicts these abortions should be under maternal control. In a study of the abortion process in Pisum sativum, we found the first visible indication of abortion was formation of a weak hypostase. Callose was locally deposited around the chalazal endosperm haustorium, and lignin along the outer cell walls of the remnant nucellar tissue. The nucellus was compressed by proliferating adjacent inner integumental cells. The endosperm haustorium's cytoplasm was forced back into the embryo sac cavity. With suppression of haustorial activity the endosperm nuclei gradually enlarged followed by enlargement of the embryo and suspensor nuclei. Finally, nuclei and cytoplasm throughout the endosperm and embryo lost stainability and broke down. Four successive stages were recognized in seed abortion. In seeds developing to maturity, no hypostase was developed and the haustorium continued to digest both the remnant nucellus and the proliferated inner integumental cells. These observations are consistent with the kin-conflict hypothesis.