Non-structural Carbohydrates Of Quercus Mongolica Under Drought Stress

In this study,seedlings of Quercus Mongolica were treated with alternating shading and light.Quercus mongolica with different contents of non-structural carbohydrates was cultured.On this basis,PEG-6000 simulated drought stress test was carried out.Three water gradients（CK,T1 with mild drought stress and T2 with severe drought stress）were set to analyze the seedling growth characteristics,photosynthetic characteristics,water potential,carbon allocation in each organ,proline,and photosynthetic characteristics of Quercus mongolica seedlings with different non-structural carbohydrate content under different drought stress.To explore the role of non-structural carbohydrate content in response to drought stress of Quercus mongolica,the aim was to provide scientific basis for revealing the drought resistance mechanism of Quercus mongolica.The main results are as follows:1.Quercus mongolica seedlings with different content of NSC showed different growth responses to drought stress.The seedling height of Gz T1 and Zg T1 was 95.23%and 96.60%of that of Gz CK and Zg CK respectively.The diameter Gz T1 and Zg T1 are 89.42%and 93.10%of Gz CK and Zg CK respectively.However,Zg T2 and Gz T2 showed no obvious growth in either seedling height diameter.At the end of stress,the specific leaf area of Gz T1was 113.18%of THAT of Gz CK,113.17%of that of Gz T2 and 102.74%of that of Zg CK,respectively（p<0.01）.2.Quercus mongolica seedlings with different content of NSC showed different changes of water potential during drought stress.The water potential of leaf and stem of Quercus mongolica decreased obviously under drought stress.At the end of drought,leaf water potential of Gz T1,Zg T1,Gz T2 and Zg T2 treatments decreased by 1.17 MPa,1.39 MPa,1.80MPa and 1.61 MPa respectively,and Zg T1 treatment was 12.8%higher than Gz T1 treatment,Zg T2 treatment was 9.13%higher than Gz T2 treatment.The difference was significant （p<0.01）.Stem water potential in Gz T1,Zg T1,Gz T2 and Zg T2 treatments decreased by 1.99MPa,1.68 MPa,2.07 MPa and 1.80 MPa,respectively,and Zg T1 treatment was 17.1%higher than Gz T1 treatment,and Zg T2 treatment was 14.8%higher than Gz T2 treatment.The difference was significant（p<0.01）.In the whole process of drought stress,Zg treatment was always higher than Gz treatment,T1 treatment was significantly higher than T2 treatment,the difference was significant（p<0.01）.3.Quercus mongolica seedlings with different content of NSC showed different physiological responses to drought stress.During the drought stress,chlorophyll a,b and total chlorophyll contents of Quercus mongolica decreased under Gz T1,Gz T2,Zg T1 and Zg T2 treatments.The decrease of Gz was significantly higher than that of Zg（p<0.01）.In terms of chlorophyll fluorescence,the maximum fluorescence（Fm）and the maximum fluorescence under light（Fm’）showed a decreasing trend.Fv/Fm and Fv’/Fm’in Gz T1 and Gz T2 treatments gradually decreased,Fv/Fm and Fv’/Fm’in Zg T1 treatment increased first and then decreased with the stress time,while the actual photochemical efficiency（Fv/Fm）and actual photochemical efficiency（Fv’/Fm’）in Zg T2 treatment did not change significantly during the stress.The net photosynthetic rate,stomatal conductance and transpiration rate of all treatments decreased under drought stress.CO₂increased under time stress.Drought stress affected the distribution of NSC in Quercus mongolica seedlings.During the drought stress,the soluble sugar content in leaves under Gz T1,Gz T2,Zg T1 and Zg T2 treatments increased first and then decreased,while the soluble sugar content in stems of Gz T1 and Zg T1 showed an increasing trend.Under the treatment of Gz T2 and Zg T2,the soluble sugar content in the stem increased first and then decreased;the starch content in the leaves and stems of Gz T1,Gz T2,Zg T1 and Zg T2 decreased;the soluble sugar content in the roots of Gz T1 and Zg T1increased first and then decreased.Under the treatment of Gz T2 and Zg T2,the soluble sugar content in root decreased,the starch content in root of Gz T1 increased first and then decreased,the starch content in root of Zg T1 increased,and both Gz T2 and Zg T2 remained unchanged first and then decreased.The proline content of Gz T1 was 157.14%of that of Gz CK,Gz T2 was 144.54%of that of Gz CK,and Zg T1 was 149.42%of that of Zg CK.,the proline content of Zg T2 was 132.93%of that of Zg CK,the difference was significant（p<0.01）.The proline content of Gz treatment was higher than that of Zg treatment.In conclusion,drought stress affected the growth,water potential,photosynthetic parameters,fluorescence parameters,chlorophyll content,proline content,NSC and its component content.The resistance of high NSC content Quercus mongolica seedlings to drought stress was higher than low NSC content Quercus mongolica seedlings...