Metabolism of free sugars in relation to starch synthesis in the developing Sorghum vulgare grain [Gramineae, starch accumulation, in vivo 14C incorporation]
1980
Bhatia, I.S. | Gumber, S.C. | Singh, R. (Punjab Agricultural Univ., Ludhiana (India). Dept. of Biochemistry)
Accumulation of starch at expense of its free-sugar precursors was studied in the developing grains of the 'SL-44' variety of Sorghum vulgare Pers. The content of starch gradually increased with the maturation of the grain and this increase was relatively fast until 18 days after anthesis. The daily rate of starch accumulation was at a maximum 15 days after anthesis. The content of total free sugars, reducing sugars, non-reducing sugars other than sucrose, total and non-sucrosyl fructose, and glucose also increased reaching maximum values at 18 days after anthesis. Sucrose content gradually increased with a concomitant decrease in the activity of invertase, and sucrose was the major non-reducing sugar in the matured grains. Detached heads incubated in labelled sugars indicated that, compared to sucrose and fructose, ('14)C was more efficiently incorporated from glucose into grain starch, which was maximally synthesized at the mid-milky stage of grain development. Exogenous supply of NAD('+) plus ATP stimulated the in vivo incorporation of ('14)C from sucrose to starch. The decline in the rate of starch accumulation did not synchronise with that of protein synthesis
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