RELATIONSHIPS AMONG FLOWERS, FRUITS, AND SEEDS

Abstract

development of diverse reproductive structures has been one of the major factors in the evolution of the angiosperms (11, 78, 90). This diversity of reproductive structures, especially in flowers, is the primary means of identifying and classifying flowering plants. Systematists, ecologists, and evolutionary biologists have traditionally treated reproduction in flowering plants as constituted by three distinct phases, each associated with a large literature: flowers and pollination (21, 47, 68), fruits and seed dispersal (20, 43, 60, 88, 91), seed and seedling establishment (39, 42). Specialized studies that consider only one phase of reproduction are typical in the botanical literature. As an example of the viewpoint that justifies specialized studies, Cronquist (16, p. 79) says The 'morphological integration' which often permits students of vertebrates to reconstruct an entire animal from a few bones simply does not exist among the angiosperms. Another facet of this same situation is that higher plants, being non-motile and lacking a nervous system, do not have their structure so precisely prescribed by their environmental requirements as do the animals. This viewpoint that characters of flowering plants are not closely integrated in the whole plant is echoed in the writings of virtually all other systematic botanists and is found in current introductory biology textbooks. At the same time, field researchers in reproductive ecology are beginning to extend the scope of their studies into a broader context, blurring the edges of the three phases of reproduction. For example, in a study of the lily, Clintonia borealis, floral ecology is shown to have significant effects on both fruit set and seed size (25). Alpine biennial -and perennial gentians differ in aspects of their pollination ecology and