Cereal grain biochemistry and related studies

Abstract

The greater part of this work describes the biochemical and morphological changes accompanying grain development in cereals. Attention is focussed on those aspects most likely to be involved in the regulation of grain yield and composition. Thus, since starch is the major component of grain yield much of the work is concerned with the developmental enzymology of carbohydrate synthesis. The composition, properties and structure of the developing starch granules and amyloplasts have also been described. Grain development is associated with a range of catabolic processes and a number of enzymes active in carbohydrate degradation has been identified. Although oxygen levels in the developing endosperm are unknown, recent work suggests that the mitochondria present are fully func- tional. It is possible that oxygen required for grain respiration is derived from pericarp photosynthesis. At the same time this tissue may fix carbon dioxide derived from endosperm respiratory processes. Thus, the pericarp may be involved in the overall control of endosperm metabolic activity. Studies of endosperm cell division indicate that this continues for more than half the developmental period, later divisions producing mainly aleurone cells. Hence, stimulation of endosperm cell division early in development will increase the yield of carbohydrate whereas at later stages it will increase the yield of protein. Further studies describe the pattern of mineral ion accumulation, the growth and nutrition of the develop - ing embryo and the morphological changes in the crease region through which nutrients move from the vascular tissue of the pericarp to the endosperm.A second group of papers is concerned with the control of a- amylase and polyphenol oxidase activity during cereal grain germination. Finally, there is a small group of papers describing research on the properties of photosynthesising tissues including marine algae.