ABSTRACT
Some recent advances in our understanding of the physiology and biochemistry of grain growth and maturation are described with particular reference to the control mechanisms that might be involved in pre-harvest sprouting. The factors controlling water supply and assimilate uptake are considered together with the mechanism whereby, during the later stages of grain filling, water loss from the interior of the caryopsis can take place without interrupting the supply of assimilate. Some of the morphological changes accompanying embryogenesis are described in relation to the surrounding tissues. The mechanisms involved in the supply of nutrients and water to the developing embryo remain largely unknown. Sucrose is the major sugar present in most developing cereal endosperms and its concentration is a function both of its rate of supply and of its rate of conversion to starch. It seems likely that, at least during the period of grain-filling, physiological events in the endosperm control sucrose levels and the rate of starch synthesis.
A study of the relationship between sucrose supply, grain water content and subsequent germination characteristics suggests that water potential of the grain may be a key factor in the control of pre-harvest sprouting.
