| Apple(Malus domestica)has a long history of cultivation.In recent years,the area and output of apples have grown rapidly,which is an advantageous industry for farmers to increase their income.Heat injury to apple leaves will cause a decline in yield and quality.therefore.Studying the response of apple leaves to high temperature adversity has very important theoretical and practical significance.In this experiment,different cultivars of apple leaves were taken as test materials,and the heat injury of apple leaves was investigated;through the method of simulating high temperature,the heat resistance thresholds of different apple varieties were determined and the changes of physiological and biochemical indexes were measured;Effects of different concentrations of salicylic acid on heat resistance were studied.The main research results were as follows:1.In 2019,the results of monitoring the temperature in the canopy of different orchards showed that the outer temperature of the canopy of different orchards was generally higher than the temperature in the inner part;The hot weather in the orchard occurs more in late June and July.The longest high temperature duration of the three apple orchards in Shunping Nanshennan county,Mancheng Dong zhaozhuang,and Quyang Zhaoyangzhuang is 6 hours,and the high temperature concentration of the three apple orchards is 11:00～17:00 and 10:00～16:00,11:00～16:00.2.The results of heat injury investigations on apple leaves in different orchards showed that the heat injury rate and heat injury index of Orin leaves were significantly higher than those of Fuji leaves;in the same orchard the heat injury investigations on the leaves of 6 different apple cultivars showed that Mid-Autumn King and Luli,The heat injury indexes of apple leaves were low,3.47 and 2.38,respectively,which indicated that ther were heat resistance,while the heat injury index of Shinano Red and Cameo are 8.65 and 7.80 respectively,and the heat resistance is weaker than other 4 cultivars..3.The heat injury rate and heat injury index of the 16 intermediate-stock Fuji trees were investigated.The results showed that the intermediate-stock Fuji trees of Huang 6,181,SH40 and M26 had strong heat resistance,while the M9 and MM106 showed weak heat resistance.4.In vitro tests have initially determined the heat resistance thresholds of Orin,Fuji and Gala leaves at 41℃,43℃,and 44℃ respectively.Simtaneously,the potted Orin and Gala apple trees were subjected to high temperature treatment to verify the threshold temperature of different varieties of apple leaves explored in the in vitro test.5.Under high temperature stress,the chlorophyll content of apple leaves showed a gradual decrease with longer of high temperature treatment,the net photosynthetic rate of leaves gradually decreased,the intercellular CO2 concentration gradually rised,stomatal conductance and transpiration rate increase and then decreased along with the high temperature treatment.Superoxide anion(O2-)production rate,malondialdehyde(MDA),proline(Pro)content and relative conductivity continue to increase;soluble protein content,superoxide dismutase(SOD),peroxidase(POD)activity increased first and then decreased.6.Under high temperature stress for 12 h,the heat injury rate and heat injury index of Fuji apple leaves treated with 150 μmol/L SA were reduced by 33.33%and 53.85%,respectively,compared with water treatment.Spraying different concentrations of exogenous salicylic acid(SA)delayed the degradation rate of chlorophyll content and inhibited the accumulation of superoxide anion(O2-)and malondialdehyde(MDA)and the increase of relative conductivity,improves the activity of SOD and POD antioxidant enzymes in leaves,and increases soluble protein and free proline(Pro)contents,which improved the heat resistance of the leaves,Spraying 150 μmol/L showed the most obvious effect. |
PDF Full Text Request