Journal of Experimental Botany Carbohydrate metabolism in the developing and maturing

Embryos of wheat {Triticum aestivum L. cv. Sappo) were studied throughout their development and mat-uration 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 max-imum at approximately 35 d. The starch content then declined to a very low value in late maturation. Extractable a-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 accumula-tion 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 increas-ing raffinose: sucrose ratios. Possible metabolic and physiological relationships among starch, raffinose, sucrose and the onset of desiccation tolerance are discussed. Key words: Wheat embryos, development, maturation, starch, raffinose, sucrose, desiccation tolerance