Abstract
In order to know the ecological characteristics of sugar beet plant sown in summer in the warmer districts of Japan, we have traced the general growing behavior and the changes of root compositions during August in 1959 to May in 1960. The varieties used were DONYU No 2 and HONIKU No 400, and both of them were sown in two times. August 1 and 21. The measurements of various plant characters and root compositions were done every 10 or 15 days, using 20 plants sampled at random. Grossly speaking, the whole cycle of growing may be distinguished into following four periods, i.e. seedling period, vigorous growing period, root ripening period and regrowing period, as seen in Fig. 1 and 7. A transition from the 2nd to the 3rd period is induced by plant physiogical states and by environmental factors, and especially, sinking of mean air temperature below about 1O°C is considered as the most effective among the latters. The brix degree and sugar content in stored roots increase gradually reaching a peak in middle or late February and after then decrease with plant regrowing as seen in Fig. 2. Purity shown in Fig. 3, however, continues to rise more rapidly after initiation of regrowing, relating to more rapid decrease in soluble substances such as soluble nitrogen and raffinose than decrease in sugar (see Fig. 4 and 5). On the other hand, the stored root continues to increase in weight more rapidly again after March; accordingly, the heaviest available sugar is found in the later season around late April (see Fig. 6). From the facts mentioned above, we could conclude that the ideal harvesting time for sugar manufacturing is in a season later than February that has hitherto been considered as the best time.
