Responses of Enzyme Activities in Carbon Metabolism to Chilling Stress in Rice with Different Chilling Tolerance

Two cultivars of rice (Oryza sativa L.), Xiangnuo 1 (chilling-tolerant) and IR50 (chilling-sensitive), were used to study the responses of enzyme activities of carbon assimilation and metabolism to chilling stress. Seedlings of rice were transferred into growth chambers for 5 days at 8℃ as chilling treatment, or at 28℃ as control. The results showed that the activities of RuBPCase, RuBPOase, and FBPase as well as carbonation/oxygenation ratio were less influenced in the chilling-tolerant cultivar, Xiangnuo 1, while those in the chilling-sensitive cultivar, IR50 were decreased under chilling stress. The activities of SPS and SS in both cultivars were increased under chilling stress. Higher levels of SPS and SS activity were maintained in the chilling-tolerant cultivar than in the chilling-sensitive cultivar. Moreover, the changed tendency in the levels of total soluble sugars, sucrose and fructose were similar to those of SS and SPS. The results indicated that the changes in enzyme activities of carbon assimilation and metabolism were in consistence with the differential tolerance to chilling in two cultivars.