CARBOHYDRATE-METABOLISM IN THE DEVELOPING AND MATURING WHEAT EMBRYO IN RELATION TO ITS DESICCATION TOLERANCE

Embryos of wheat (Triticum aestivum L, cv, Sappo) were studied through out their development and maturation to investigate the relationships among starch, sucrose and raffinose and the onset of desiccation toler ance, Starch accumulated in axes and scutella from about 20 d post ant hesis (dpa) to reach a maximum at approximately 35 d, The starch conte nt then declined to a very low value in late maturation, Extractable a lpha-amylase activity increased in embryos throughout the period of st arch deposition and showed a substantial rise coincident with starch b reakdown, In early maturation (approximately 26 dpa) sucrose and raffi nose appeared, and continued to increase, The rise in the amount of su crose paralleled the accumulation of starch, but the major increase in raffinose approximated to the fall in starch content, Embryos were de siccation intolerant prior to the age when free sucrose and raffinose accumulated: the development of dediccation tolerance was associated w ith increasing raffinose:sucrose ratios, Possible metabolic and physio logical relationships among starch, raffinose, sucrose and the onset o f desiccation tolerance are discussed.