Effects Of Drought Stress On Photosynthetic Characteristics And Leaf Structure Of The Different Rootstocks Of The Hybrid ‘Shiranui Tangerine' Citrus

In this study,the grafted seedlings of 2 years old of the hybrid citrus‘Shiranui'were selected as the experimental materials,and a total of 5 species of citrus rootstocks were selected,including C.sinensis?Poncirus trifoliate?L.?Raf?C.tangerine Hort.ex Tanaka?C.sinensis×Poncirus trifoliate and C.erythrosa.Water supply was set as the percentage of soil water content in the maximum water holding capacity in the field,and 4 water supply treatments were set,respectively CK was the normal water supply.Light stress?LS?was58-60%of field water capacity.Moderate stress?MS?was 38-40%of the water capacity in the field.Severe stress?SS?was 18-20%of the field water capacity,and the effects of drought stress on leaf photosynthesis,physiological and biochemical changes and the changes of leaf tissue and anatomical features were studied.Combined with the above indexes,drought resistance of five citrus rootstocks was compared,and the following results were obtained.1.Drought resistance pot experiment was carried out on five citrus rootstocks.According to the comparison and analysis of each indicator,in the severe drought stress treatment for 20 days,C.erythrosa had the higher of the net photosynthetic rate than the other four rootstocks?C.tangerine Hort.ex Tanaka?Poncirus trifoliate?L.?Raf?C.sinensis×Poncirus trifoliate?C.sinensis?,respectively beyond 6.45%,11.06%,52.53%,53.46%.And the C.erythrosa had the higher of the intercellular CO₂ concentration than the other four rootstocks,respectively beyond 6.29%?10.49%?14.44%?39.43%.What's more,it had the higher of the transpiration rate than the other four kinds of rootstocks,respectively beyond 42.86%,53.97%,77.78%,80.95%.Meanwhile the stomata conductance of the five kinds of rootstocks were no difference.In addition,the Pn,Gs,Ci and Tr of C.erythrosa were the largest in any drought stress treatment environment,indicating that the photosynthesis of C.erythrosa was stronger than the other four rootstocks.2.At the 20th day of SS treatment,the leaves of five citrus rootstocks,including C.erythrosa?C.tangerine Hort.ex Tanaka?Poncirus trifoliate?L.?Raf?C.sinensis×Poncirus trifoliate?C.sinensis,had water content of 42.17%,42.03%,40.59%,40.03%and 39.03%,respectively.The stomatal density of leaves of C.erythrosa was as high as 887.17-888.65/cm² under CK.With the deepening of drought stress and the extension of stress time,the stomatal density gradually decreased,but its value remained at a large level.At this point,chlorophyll content of its the leaves was still higher at 2.04±0.17mg/g,indicating that its drought resistance was stronger than that of the other four rootstocks.Therefore,according to the comprehensive analysis of data,the drought-resistant order of the five rootstocks tested was:C.erythrosa>C.tangerine Hort.ex Tanaka>Poncirus trifoliate?L.?Raf>C.sinensis×Poncirus trifoliate>C.sinensis.3.With the deepening of drought stress and the passage of time,the leaf cells of the five rootstocks of‘Shiranui'had undergone relatively serious plasma wall separation.In addition,the chloroplast structure was damaged to different degrees,in the 5 kinds of rootstocks of the hybrid citrus‘Shiranui',the performance of the C.sinensis was the most obvious.4.With the increase of drought stress degree and time,the net photosynthetic rate,transpiration rate,stomatal conductance,intercellular carbon dioxide concentration and other photosynthetic indexes of leaves of the five rootstocks of the hybrid citrus‘Shiranui'all showed a downward trend.The change of chlorophyll content showed a downward trend.Meanwhile,the activity of SOD,CAT and POD of the leaves had increased in the previous time and decreased in the last time.