Studies On Sink Activity And Physiological Changes During The Development Of Taproot In Radish (Raphanus Sativus L.)

Radish (Raphanus sativus L.) is a very important vegetable in our life. It has abundant nutrition in its edible storage root. In this paper, four cultivars were employed to study the changes in source activity, sink activity, carbohydrate contents, protein contents as well as changes in taproot anatomy. The main purpose is finding the mechanism in the development and growth of storage root in the radish. The main results were as follows:(1) The results showed that three cultivars, 'Baiyuchun', 'Duanye 13' and 'Leafy radish', had a similar growth type. The growth of shoot was faster compared with storage root before 28 day after seedling emergence (DAS). During this growth stage, the root to shoot ratio was below 0.1. The root began to thicken and the dry weight of root strongly increased significantly after 28 DAS. The highest source activity was found at 21DAS in three varieties. However, the highest sink activities in 'Leay radish', which had a low ratio of root to shoot, and 'Duanye13', which had a high ratio of root to shoot, were estimated at 28 DAS, while the highest sink activity of 'Baiyuchun', which had a common ratio of root to shoot, was estimated at 35 DAS. During the whole development of storage root, source activity in 'Duanye 13' was lower than the others.(2) Changes in carbohydrates, including reduced sugar and soluble sugar sucrose, was similar in both radish cultivars 'Duanye 13' and 'Baiyuchun'. The contents of reduced sugar, soluble sugar, sucrose was lower in the storage root from 7 DAS to 14 DAS. With the growth of storage roots, the contents of reduced sugar and sucrose decreased gradually, After reached the highest levels, the contents of reduced sugar and sucrose decreased. Contents of reduced sugar, soluble sugar in the storage root of 'Duanye 13' radish was higher than those in 'Baiyuchun' after 21DAS. Only little starch was detected in both radish cultivars storage roots.(3) Proteins of four different radish cultivars were analyzed by SDS-PAGE. The results showed that not only the amount of soluble proteins changed, but also some proteins disappeared during the growth period. It was found that the contents in the leaves were higher than that in storage root during the root thickening. With the storage root growth, protein contents increased, and reached the highest level from 21 to 28 DAS both in roots and leaves, then decreased slowly in the storage roots. The intensities of protein bands in the leaves were stronger than those in storage root. The protein of approximately 14.4KD existed from 7 DAS to 21DAS, then it became...