Carbohydrate metabolism in the developing and maturing wheat embryo in relation to its desiccation tolerance

Abstract

Embryos of wheat (Triticum aestivum L. cv. Sappo) were studied throughout their development and maturation to investigate the relationships among starch, sucrose and raffinose and the onset of desiccation tolerance. Starch accumulated in axes and scutella from about 20 d post anthesis (dpa) to reach a maximum at approximately 35 d. The starch content then declined to a very low value in late maturation. Extractable α-amylase activity increased in embryos throughout the period of starch deposition and showed a substantial rise coincident with starch breakdown. In early maturation (approximately 26 dpa) sucrose and raffinose appeared, and continued to increase. The rise in the amount of sucrose paralleled the accumulation of starch, but the major increase in raffinose approximated to the fall in starch content. Embryos were desiccation intolerant prior to the age when free sucrose and raffinose accumulated: the development of desiccation tolerance was associated with increasing raff inose : sucrose ratios. Possible metabolic and physiological relationships among starch, raffinose, sucrose and the onset of desiccation tolerance are discussed.