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biochem seeds

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 the food reserves it contains, which are available to sustain the young plant in the early stages of growth before it becomes an independent, autotrophic organism, able to use light energy. People also depend on these activities for almost all of their 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 those of 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.

Seeds

  • J. Derek Bewley
  • Michael Black

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 the food reserves it contains, which are available to sustain the young plant in the early stages of growth before it becomes an independent, autotrophic organism, able to use light energy. People also depend on these activities for almost all of their 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 those of 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.

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The cellular processes which have been studied most extensively in the germinating seed are respiration, enzyme and organelle activity and RNA and protein synthesis. This is not surprising for it is reasonable to expect that such fundamental aspects of cellular activity should play an important role in the preparation of seeds for germination; we will concentrate on these in this chapter. Other metabolic events (such as steroid biosynthesis, changes in alkaloid content) have also been studied but since at the present time these do not appear to be important for the initiation and control of germination they will be ignored. For the sake of continuity, biochemical events associated with both germination (radicle emergence) and subsequent growth will be considered together in this chapter although we will indicate which occur prior to visible germination and which are post-germination events. The reader should be careful to distinguish between these. Such a distinction does not always appear in the literature on seed physiology and workers and reviewers often refer loosely to germination when they are in fact considering seedling growth. The exclusively post-germination events in connection with food mobilization are discussed in Chapter 6.

Biochemistry of Germination and Growth

  • J. Derek Bewley
  • Michael Black

Abstract

The cellular processes which have been studied most extensively in the germinating seed are respiration, enzyme and organelle activity and RNA and protein synthesis. This is not surprising for it is reasonable to expect that such fundamental aspects of cellular activity should play an important role in the preparation of seeds for germination; we will concentrate on these in this chapter. Other metabolic events (such as steroid biosynthesis, changes in alkaloid content) have also been studied but since at the present time these do not appear to be important for the initiation and control of germination they will be ignored. For the sake of continuity, biochemical events associated with both germination (radicle emergence) and subsequent growth will be considered together in this chapter although we will indicate which occur prior to visible germination and which are post-germination events. The reader should be careful to distinguish between these. Such a distinction does not always appear in the literature on seed physiology and workers and reviewers often refer loosely to germination when they are in fact considering seedling growth. The exclusively post-germination events in connection with food mobilization are discussed in Chapter 6.

Keywords

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