Carbohydrate content and isozyme changes during fleshy tap root formation and thickening in Raphanus sativus.

摘要

Using two radish advanced inbred lines with different ratios of storage root to shoot as materials, several physiological changes, EST, SOD and amylase isozymes were investigated during the process of fleshy tap root formation and thickening. The results showed that sink activities of the two lines were nearly identical; carbohydrate contents declined until tap roots began to thicken; the activity of invertase was much higher than that of sucrose synthase (SuSy) in the beginning, then decreased rapidly. SuSy reached its maximum at 27 DAS and then declined. "NAURa-DY02", with a high ratio of storage root to shoot, had a lower content of sucrose than "NAURa-LHZ03", a line with low ratio of storage root to shoot. This might result in a high sucrose concentration gradient in line with high ratio of storage root to shoot, resulting in more nutrition being absorbed by the root for thickening and formation. It can be inferred that SuSy may play an important role in the development of sink activity through the regulating of sucrose content. Isozyme analysis showed that both EST and SOD isozymes varied in the leaves and roots. Amylase isozyme revealed two identical bands in the leaves and roots over the whole development stage, indicating that amylase isozyme may have no relationship with the thickening of radish fleshy tap root.