Embryology of Early Abortion Due to Limited Maternal Resources in Pisum sativum L.

In most flowering plants, many embryos are aborted early intheir development due to limited maternal resources. The kin-conflictinterpretation of plant embryology predicts these abortionsshould be under maternal control. In a study of the abortionprocess in Pisum sativum, we found the first visible indicationof abortion was formation of a weak hypostase. Callose was locallydeposited around the chalazal endosperm haustorium, and ligninalong the outer cell walls of the remnant nucellar tissue. Thenucellus was compressed by proliferating adjacent inner integumentalcells. The endosperm haustorium's cytoplasm was forced backinto the embryo sac cavity. With suppression of haustorial activitythe endosperm nuclei gradually enlarged followed by enlargementof the embryo and suspensor nuclei. Finally, nuclei and cytoplasm throughout the endosperm and embryolost stainability and broke down. Four successive stages wererecognized in seed abortion. In seeds developing to maturity,no hypostase was developed and the haustorium continued to digestboth the remnant nucellus and the proliferated inner integumentalcells. These observations are consistent with the kin-conflicthypothesis. Pisum sativum, garden pea, ovule abortion, histology, hypostase, kin-conflict hypothesis