Seeds

Abstract

The new plant formed by sexual reproduction starts as an embryo within the developing seed, which arises from the ovule. When mature, the seed is the means by which the new individual is dispersed, though frequently the ovary wall or even extrafloral organs remain in close association to form a more complex dispersal unit as in grasses and cereals. The seed therefore occupies a critical position in the life history of the higher plant. The success with which the new individual is established—the time, the place, and the vigor of the young seedling—is largely determined by the physiological and biochemical features of the seed. Of key importance to this success are the seed’s responses to the environment and, on a biochemical level, its food reserves, which are available to sustain the young plant in the early stages of growth before it has become an independent, autotrophic organism, able to use light energy. Man also depends on these activities for almost all of his utilization of plants. Cultivation of most crop species depends on seed germination, though, of course, there are exceptions when propagation is carried out vegetatively. Moreover, seeds such as the cereals and legumes are themselves major food sources whose importance lies in the storage reserves of protein, starch, and oil laid down during development and maturation.