Changes in sugars during rice seed desiccation

The correlation between desiccation tolerance and soluble sugars was investigated in seeds of a number of rice cultivars belonging to the Asian rice Oryza sativa L. They were dried or ultradried to various low moisture content and then imbibed for germination testing. Few or no changes on germination percentage and vigor index were found in Indian rice seeds even after their moisture content fell to 3.5%, indicating that Indian rice exhibited a strong desiccation tolerance. On the contrary, Japonica rice seed germination percentage rapidly decreased, after their moisture content fell to 4.5%. The capacity for desiccation tolerance in Japonica (cv. Chunjiang 15) and Indian (cv. Zhongzu 1) developing seeds increased on 23–40 and 15–25 days after pollination, respectively. Though the level of monosaccharides declined, the content of sucrose has increased during desiccation. These results suggest that desiccation tolerance might be associated with the increase in seed viability and the changes in sugar level, and that raffinose could be capable of contributing to the desiccation tolerance to ultradrying. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 2, pp. 220–226. The text was submitted by the authors in English.