THE DEVELOPMENT OF YIELD AND THE DISTRIBUTION AND ACCUMULATION OF PROTEIN IN SWEET POTATOES

In accordance with the development of yield,the growth process of the sweet potato plant could be divded into three phases; 60, 60-90 and 90-150 days after planting were defined as early,middle and late growth stages respectively.The fresh and dry weights of vines reached the maximum amount in the early stage and decreased from then on. The fresh and dry weights of tubers increased slowly during the early stage and speeded up in the middle and late atages. Total biological yield,which was greatly affected by tuber weight,increased relatively faster in the late growth stage. The ratio of fresh weight to dry weight and the percentage of starch in tuber increased relatively faster and reached peak value in the middle growth stage. The accumulated yield and the content of soluble sugar in tubers increased mainly in the late stage.For the whole growth season the protein contents in organs of the sweet potato plant were ranked as follows:leaf blade>root>leaf- stalk>stem>tuber. The protein contents of the various organs began to decrease 30 days after planting, with the development of plant growth the main flow of protein movement shifted from the aerial parts to underground parts (tubers). The accumulated yield of protein had a linear increase in the early growth stage, remained relatively stable in the middle stage and increased slowly again in the late stage. There was a very significant positive correlation between the accumulated protein amount of tubers and the dry matter ratio, as well as between it and the dry weight and fresh weight of tuber.