The Physiological And Biochemical Responses Of Upland Rice (Zhenghan-2) Calluses To Salt Stress

The calluses from the upland rice breed (zhenghan-2) was used to study the responses to salt stress and the calluses from the normal rice breed (Yujing-6) was used as control in this investigation. To better understand the physiological and biochemical responses and the possible regulating mechanism in the calluses of zhenghan-2 under salt stress, the relative membrane permeability, MDA content, relative cell variability, the accumulation and scavenging of ROS, and the respiration pathway under salt stress were determined. The results showed that the membrane damage in zheng-2 calluses was lower than that in Yujing-6 calluses. The relative membrane permeability in zhenghan-2 increased from 22% to 33%. But it increased in yujing-6 calluses from 27% to 48%. MDA content in zhenghan-2 under salt stress was also lower than that in yujing-6 calluses. These data demonstrated that zhenghan-2 has stronger salt tolerance than that of yujing-6. In the further study, we found that the antioxidant enzyme activities in zhenghan-2 calluses were dramatically enhanced compared to yujing-6 calluses under salt stress. The activity of APX, CAT and SOD was about 1.84, 1.6 and 3-fold of yujing-6 calluses. These results suggested that there was the high reductive level to resist the salt stress in zhenghan-2 calluses. Under salt stress, O₂^- content in zhenghan-2 calluses was higher than that in yujing-6 calluses which may be act as the signal molecular to stimulate the antioxidant enzyme activity including APX, CAT, SOD to scavenge the ROS and reduce the oxidative stress induced by salt stress. Compared to yujing-6 calluses, the higher contents of betaine (1.4-fold) and soluble sugars (1.2-fold) in zhenghan-2 calluses may regulate the osmotic stress induced by salt stress.Based on the results above, the calluses of zhenghan-2 has stronger resistance to salt stress than the calluses of yujing-6. The reason may be ascribed to the higher activity of antioxidant enzyme system and the accumulation of the osmotic substances.