Parental strategies of angiosperms

Abstract

This paper considers strategies for optimally deploying the parental investment that a plant makes during one reproductive session. The subdivision of a plant's reproductive effort into many flowers and fruits causes plants to show distinctive parental strategies. The distribution of gametes is far more complicated in plants than in animals. The following classes of strategies are discussed: Gender strategies control the relative contributions to fitness that result from maternal and parental investments. Cosexual, male and female morphs are distinguished by their average gender. A simple method for quantitatively estimating the functional gender of plants is used to distinguish three types of gender reactions to various circumstances, namely canalised, labile, and sequential gender responses. Relative maternal and paternal expenditures. Maternal costs may exceed paternal costs by a considerable amount in many species. Size-number compromises for seeds and pollen. The conflicting advantages of size and number have been actively investigated for seeds but not for pollen grains. Seed and pollen packaging — the relative numbers of polliniferous flowers and fruit. Hermaphroditism, andromonoecy, and gynomonoecy are compared as relative packaging strategies. The temporal control of maternal investment. Many factors influence the extent to which it is advantageous to control fruit numbers at the successive stages of flower determination, ovary development, and fruit maturation. Breeding patterns control the parentage of seeds, and include the frequencies and distributions of sexual versus asexual reproduction and of self- versus cross-fertilisation. Botanists have concentrated on selection for genetic recombination as a factor controlling breeding patterns, and other factors have been under-emphasised.