PubMed · 11262790
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M Plachot. 2000. Fertilization.. https://doi.org/10.1093/humrep%2F15.suppl_4.19
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There is currently an intense interest in understanding how pollination and fertilization in flowering plants is controlled. This is because of the central and crucial importance of sexual reproduction in plant lifecycles. Plants have evolved many complex mechanisms to prevent self-fertilization, and it is thought that this may partially explain the great success of the angiosperms. The journey of discovery in determining the components and mechanisms involved in these processes has been ongoing for some time. Recent data have provided fresh insights into some aspects of what is involved in controlling pollen germination and pollen-tube growth, both in normal pollination and in self-incompatibility.
The flowers of most angiosperm species are hermaphroditic. Spatial separation of male and female organs within a flower (hercogamy) is a common character traditionally interpreted as an adaptation to reduce intrafloral self-fertilization, one potential cost of hermaphroditism. Another possible cost that may lead to selection for hercogamy is physical interference between male and female floral functions. Here, I present evidence demonstrating the role of a floral character in reducing female interference with male function. The bi-lobed stigma of the bush monkeyflower closes after receiving pollen, causing increased spatial separation of the anthers and stigma ('movement' hercogamy). Experimental manipulations show that flowers with closed stigmas export more than twice as much pollen to other flowers as those in which the stigma is prevented from closing. However, stigma closure only minimally reduces the potential for intrafloral self-pollination. This study provides the first experimental evidence that selection to reduce intrafloral male female interference can be a strong selective force and can drive the evolution of floral characters usually interpreted as mechanisms to reduce self-fertilization.
During seed development, coordinated developmental programs lead to the formation of the embryo, endosperm and seed coat. The maternal effects of the genes affected in the fertilisation-independent seed class of mutants play an important role in seed development. The plant Polycomb proteins MEDEA and FERTILIZATION-INDEPENDENT ENDOSPERM physically interact and form a complex, in a manner similar to that of their counterparts in animals. Maternal-effect phenotypes can result from regulation by genomic imprinting, a phenomenon of critical importance for both sexual and apomictic seed development.