Effect Of NaHSO₃ On Some Physiological Characteristics Of Wheat

As a general phenomenon in green plants, the photorespiration was once regarded as a consuming process because of its effect of reducing photosynthesis. From 1960s, when the photorespiration was found in tobacco leaves, people paid great attention to look for an effective inhibitor to reduce the photorespiration in C₃ plants, hoping for a consuming reduction to increase photosynthesis, carbohydrate assimilation and yield. However, there were more and more reports showed that plant couldn't survive when the photorespiration was inhibited. These indicated that the photorespiration has some important functions in C₃ plants. We chose NaHSO3, which was studied and applied broadly in the recent years, as an inhibitor of photorespiration in our study. Under field condition, the effect of spraying NaHSO3 on photorespiration rate, photosynthesis rate, carbohydrate assimilation and nitrate reduction in flag leaves of wheat at reproductive stage and on protein content in kernel were studied. In light condition, the effect of NaHSO3 treatments on the GOA, nitrate reduction, protective enzymes activities and membrane lipid per-oxidation in wheat seedlings were also studied. We examined the ability of NaHSO3 as an inhibitor of photorespiration, and studied on the relationship between photorespiration, photosynthesis and carbohydrate assimilation. We also studied on the functions of photorespiration in the nitrogen metabolism and in the defending of damaging caused by photo-oxidation. The results show as follows: 1. Under field condition, the photorespiration rate varied in correspondence with the photosynthesis rate in flag leaves of wheat at reproductive stage. There existed a ratio between the two: the former was roughly 30% of the latter. And it was found that photorespiration rate varied with 1h of delay after photosynthesis rate. 2. Under field condition, the photorespiration rate was inhibited and the photosynthesis rate was increased in flag leaves of wheat at reproductive stage by spraying NaHSO₃, which might result in the increase of the carbohydrate assimilation and the yield of grain. 3. Under field condition, the NRA and the content of free amino acid and soluble protein were decreased, and the content of nitrate nitrogen was increased in flag leaves of wheat at reproductive stage by spraying NaHSO₃, which might result in the decrease of protein content in kernel. 4. In light condition, the GOA in green wheat seedlings was decreased and the light induction for the GOA in etiolated wheat seedlings was inhibited by spraying NaHSO₃. 5. In light condition, the NRA and the content of free amino acid and soluble protein were decreased, and the content of nitrate nitrogen was increased in green wheat seedlings treated by NaHSO3. The light induction for the NRA in etiolated wheat seedlings was inhibited. 6. In light condition, the activities of SOD, CAT, POD and APX in wheat seedlings were increased by spraying NaHSO3. And the generation rate of super-oxide anion, the content of MDA and the relative plasma-lemma permeability were also increased.