Physical properties of starch granules of tobacco leaves during maturity stage

Although there are many studies concerning starch accumulation pattern of tobacco leaves during maturity stage (1, 2, 3, 4, 5), much less attention has been paid to physical properties of starch granules of tobacco leaves. Matheson et al. (6) reported in their study of starch changes in developing and senescing tobacco leaves, that the viscosities and iodine affinities of isolated starch granules increased with increasing age of the leaf, the β-amylosis limits of the whole starch and chain length of the amylopectins Were constant through the growth of the leaf and that the average granule size increased as the leaf matured and decreased as the starch conent decreased. One of the cl1aracteristics of maturity is to accumulated a large amount of starch after topping, but they used non topped f1ants, therefore the starch content was rather low. In our previous work (7) it has been demonstrated by using starch granules isolated rom tobacco leaves of topped plants, that the granule size and the ratio of amylopectin to amylose increased with the leaf maturity, a large alllount of calcium oxalate was found in the granules, and that the activity of starch synthetase bound with starch granules decreased with time after topping.