Photorespiration Performance Of Ear Oganss In Different Drought Resistance Wheats Under Water Deficit

Drought is one of the main factors that restrict the high and stable yield of wheat in China North areas. Studies have shown that spike bracts have significant physiological and biochemical advantage under drought stress. Photosynthesis and photorespiration are two opposite metabolic processes. Photosynthesis fixed CO2, photorespiration release CO2. In the light,O2 competed with CO2 to ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) at the same catalytic site. Studying the characteristics of photorespiration of wheat ear, and physiological significance of photorespiration in high temperature, high light conditions is expected to provide reference for wheat breeding work. In this study, hydroponic experiment is carried out to study the response to drought stress of wheat seedling leaves photorespiration rate by selecting the rainfed variety Xinong 928 and plain variety Shaan 229, and measuring photorespiration rate(Pr) and key enzymes activity of leaves in trefoil stage. Analyzing the effect of photorespiration inhibitors NaHSO3 on dry matter accumulation of wheat.Pot experiment selected the dryland cultivar xinong 928 and plain variety shaan 229, measuring flag leaf and ear Pr,finding the effect of water deficit on the diurnal variation of flag leave and ear Pr in wheat. The main results were listed as follow:1. Pr and Glycolate Oxidase(GO) activity all declined at 24 h after 20% PEG stress. Xinong 928 had larger fall. GO enzyme activity falled by 50.24%(P<0.01) in Xinong 928, while Shaan 229 falled by 32.51%. Spraying NaHSO3 to the wheat seedling leaves could inhibit the activity of GO and photorespiration, and increase leaf net photosynthetic rat(Pn), whiling spraying NaHSO3 in the long-term resulted wheat dry weight declined, Glutamine Synthetase(GS) enzyme activity decreased. It affected adversely the growth of wheat. Photorespiration was beneficial to the progress of photosynthesis.2. Flag leaf Pn declined with grouting process. shaan showed more serious effect of water deficit on flag leaf Pn at 24 DAA. The Pn of ear organs firstly increased and then decreased, reaching to the maximum at 6 DAA. At 24 DAA, both Xinong 928 and shaan229 did not decrease significantly under water deficit. It didn’t affected the growth of wheat adversely. Water deficit had a smaller influence on ear Pn.3. Ear organs and flag leaves Pr firstly increased and then decreased, reaching to the maximum at 12-18 DAA. Both of their Pr are higher than the control group, and ear organs rised more than flag leaves, the flag leaves Pr increased about 33.5%, the ear organs Pr increased by 50.2%(p<0.01). It indicated that wheat’s Pr increased under water deficit, and the drought-resistance varieties Xinong 928 were higher than the water-sensitive varieties Shaan 229.4. The photorespiration of ear organs and flag leave firstly increased and then decreased, reaching to the maximum at 12:00. The flag leave and ear Pr increased under water deficit, and the drought-resistance varieties Xinong 928 were higher than the water-sensitive varieties Shaan 229. The flag leaves Pr increased about 10:00, the ear organs Pr moved to 14:00.5. Xinong 928 GO activity rised more than Shaan 229, particularly in glume, GO activity increase by 117.8%(P<0.01), in Xinong 928 at 12 DAA respectively, while Shaan 229 rise to 95.6%. Under deficit, it affects the growth of wheat adversely. It indicates photorespiration is beneficial to the progress of photosynthesis.ear organs GS activity is activity higher than flag leave GO activity. at 12 DAA Xinong 928 rise to 5.71%(P<0.05),while Shaan 229 decreased. It indicates that GS was related to drought resistance, and the drought-resistance of ear organ was higher than flag leaf.6. Under water deficit, the weight of grains per ear declined by 30.00% and 39.2%(P<0.01) in Xinong 928 and Shaan 229, whiling spraying NaHSO3 in the long-term resulted the yield of wheat declined. It affected the growth of wheat adversely. It indicated photorespiration played an important role in the growth of wheat. Photorespiration is indispensable to plant normal growth and metabolic pathway, especially played an important role under water stress.