Abstract:The aim was to understand the function of endogenous ascorbic acid in rice (Oryza sativa) seeds. The homozygote transgenic lines GO-2 with the up-regulated GLDH (the key enzyme that catalyzes the final step of Asc biosynthesis in plants gene) and GI-2 with the down-regulated GLDH had been established from the cultivar ‘Zhonghua 11’ (ZH-11). The effect of endogenous ascorbic acid on seed germination and seedling growth of rice was studied among ZH-11, GO-2 and GI-2. The results showed that the germination rate of GO-2 was 6% and 60% higher than that of wild type (ZH-11), and GI-2, respectively. After treatment with 1 mmol L-1 exogenous ascorbic acid, the germination rate of GI-2 increased by 22%, but no significant effect was observed in that of GO-2 and the wild type (ZH-11). The root length, plant height, tiller number and fresh weight of seedling in GO-2 were higher than those in ZH-11 or GI-2. The expression of GLDH gene in GO-2 leaves was higher than that in ZH-11 or GI-2, too. So, these indicate ascorbic acid plays an important role in maintaining seed vigor and improving germination and seedling growth of rice.