Photosynthetic Efficiency Of Apple Leaves Under Water Storage Pit Irrigation

Apple is an important cash crop in North China.Leaf photosynthesis plays an important role in the growth and development of fruit trees,the quality of fruit and the yield of fruit.Photosynthesis is the sum of a series of complex metabolic reactions.Chlorophyll content in leaves,energy supply of soluble sugar and photosynthetic enzyme system have great influence on photosynthetic process of fruit trees.Therefore,it is necessary to study the effects of chlorophyll,soluble sugar and antioxidant dismutase on the leaf efficiency of fruit trees.Water storage pit irrigation has changed the distribution of soil water,and this characteristic of water distribution will inevitably affect the photosynthesis of fruit trees.In this paper,the apple trees treated with the dwarfing anvil of Gangfu No.2 for 6 years were used as experimental materials,and four treatments were established.Treatment T1 refers to local field irrigation quota,the irrigation time was determined according to soil moisture content（70%of field water holding capacity）and leaf physiology of fruit trees（leaf color and leaf visible change）,T2 and T3 were processed according to soil moisture content（60%of field capacity）and fruit leaf physiology（leaf color and leaf visual changes）to determine irrigation time,and irrigation water was set at 80%and 60%of T1,as compared to surface irrigation CK,the irrigation quota for treatment T1 is the same.By studying the response of water storage pit irrigation of apple trees under the condition of photosynthetic characteristics and physiological and biochemical indexes of leaf scale,further reveal photosynthetic characteristics of the apple tree under the condition of water storage pit irrigation,chlorophyll,carbohydrate content,antioxidant enzymes in photosynthesis to reflect the water storage pit irrigation,finally extract the great impact on the factors of fruit tree contribution by principal component analysis,analysis of its relationship with apple fruit yield,the main conclusions of this paper are as follows:1.Research on the variation of photosynthetic parameters in Fruit Tree leaves under water storage pit irrigation（1）The net photosynthetic rate of T1 and CK showed a double peak curve.The peak value of T1 was higher and later than that of CK in control group,and the duration of high net photosynthetic rate was longer.The net photosynthetic rate of T2 and T3 showed a single peak curve.The peak value of net photosynthetic rate in four treatments was T1>T2>T3 and CK.Water storage pit irrigation could still improve the net photosynthetic rate of fruit tree leaves on the premise of saving irrigation water,and the peak value of net photosynthetic rate of water storage pit irrigation was delayed compared with that of surface irrigation.From April to August,the stomatal conductance,intercellular CO₂concentration and transpiration rate of T1 were the highest.The peak stomatal conductance of T2 from August to October was the highest.The peak stomatal conductance duration of T1 was longest.After October,the decrease rang of stomatal conductance and transpiration rate of T1 was the lowest.leaves of T1can maintain large stomatal conductance under high temperature,which was beneficial to the entry of CO₂ in fruit tree leaves.（2）The Dynamic variations of photochemical quantum efficiency,photochemical quenching coefficient,electron transfer efficiency and PSII’s actual photochemical quantum efficiency of the four treatments showed:from May to middle of August,the parameters remained at a high level and declined rapidly after September.From May to September,the photochemical quantum efficiency,photochemical quenching coefficient,electron transfer efficiency and the actual photochemical quantum efficiency of PSII of T1 and T2 were higher than those of T3 and CK,T2 was even higher than T1 in July and August.T1and T2 was beneficial to increase the photosynthetic capacity of fruit trees,T2was beneficial to excite the maximum potential photochemical quantum efficiency of the leaves of fruit trees.The photochemical quantum efficiency,photochemical quenching coefficient,electron transfer efficiency and the actual photochemical quantum efficiency of PSII of T1 were the smallest after middle of September.T1 was beneficial to keep photosynthetic activity of fruit leaves after leaf senescence,and the activity of leaves decreased slightly,which enhanced the resistance ability of leaves to stress.The non-photochemical quenching coefficient of the four treatments first decreased and then increased,and after October,the leaf function lost,and the non-photochemical quenching coefficient decreased sharply.From May to June,the non-photochemical quenching coefficient of T1 was the lowest,and it’s light energy absorbed by leaves was more converted into photochemical reaction.From July to September,the light absorption of T1 and T2 was more used in photochemical reactions.After September,the non-photochemical quenching coefficient of T1 was less than that of T2,T1 irrigation quota had strong protection ability after leaf senescence.2.research on the changes of photosynthetic signal Indexes in leaves of Apple trees under water storage pit irrigation（1）The Dynamic variation of leaf water potential between different treatments showed that:It increased first and then decreased,and fluctuated greatly on middle of July.During the period from April to May,the leaf water potential of each treatment was T1>T2>T3>CK.Water storage pit irrigation can protect water content,which was beneficial to the growth of leaves in this period.After June,the leaf water potential of each treatment was T2>T1>T3>CK,T2 was more favorable to water absorption and utilization after the leaves are mature.（2）The Dynamic variation of leaf chlorophyll a,chlorophyll b and total chlorophyll content in different treatments was as follows:The chlorophyll content increased rapidly between April and July.After July,the chlorophyll content was stable at a higher level,but the chlorophyll content did not decrease significantly after July.From April to July,the results of chlorophyll a,chlorophyll b and chlorophyll content were as follows:T1 and CK>T2>T3.During this period,the amount of irrigation was very important to the synthesis of chlorophyll,and reducing the amount of irrigation will inhibit the synthesis of chlorophyll.After July,the contents of chlorophyll a,chlorophyll b and total chlorophyll in the treatment were:T1 and T2>CKandT3.Irrigation of T1 and T2 in water storage pit was beneficial to increase the content of chlorophyll.The chlorophyll of T2 was not affected by strong light.（3）Among the treatments,the activity of SOD showed a"W"pattern,in the late stage of leaf senescence,the protective mechanism of leaf was destroyed,and the activity of SOD enzyme decreased sharply.The activity of SOD enzyme in the treatment was T1 and T2<T3 and CK.Because of the low demand for SOD enzyme in water storage pit irrigation of T1、T2 and the high content of superoxide anion O^2-were used for electron transport in leaves and,photosynthetic ability of leaves was strong.In October,the activity of SOD was T1>T2>CK>T3,there was still a high protective mechanism in T1 leaves at late stage.（4）The fructose content decreased first and then stabilized at 0.4-0.5 mg/g,The content of sucrose decreased first and then increased.On August,there was a sudden rise and decrease,used to regulate leaf osmotic pressure;The contents of fructose and sucrose in the treatment were T3 and CK>T1 and T2,fructose and sucrose of the T1 and T2 was transformed into storage soluble sugar,which was used in fruit tree growth and fruit development.There was no significant difference in new accumulated growth between treatments before August.After August,the new slight growth rate of T2 was the fastest.After August,treatment T2 had the fastest growth rate and the largest accumulation of growth,T1 came second,irrigation of T1 and T2 in water storage pit was beneficial to the new growth of apple trees.3.research on changes of photosynthetic Index on Fruit yield under Irrigation in Water Storage PitThe rate of fruit growth was fast before mid September,and the fruit growth rate slowed down after mid September.The growth rate of the transverse length of the fruit was the same among the four treatments,the fruits longitudinal growth of T3 lower than the other three treatments.The single fruit weight and fruit yield of T1 were significantly better than the other three treatments,the mean value of fruit quantity was superfluous to the other three treatments,but there was no significant difference,There was no significant difference in fruit yield between T2 and CK.Water storage pit irrigation T1 can effectively increase the yield,T2 saved 20%irrigation amount and the yield did not decrease;The acidity of T1 and T2 was significantly lower than that of surface irrigation,The content of soluble solids in T1 fruit was the largest,and significantly superfluous T3 and CK,and there was no significant difference from T2.The photosynthetic ability of leaves of T1 and T2 was strong and the soluble sugar of fruit increased under the irrigation of water storage pit.Based on principal component analysis,T1 and T2 showed obvious advantages in photosynthetic capacity,the leaf water potential was large,the net photosynthetic rate,stomatal conductance and chlorophyll were higher than those in surface irrigation,the non-photochemical quenching coefficient and the activity of SOD had a strong ability to regulate,the final yield was significantly better than that of surface irrigation.The photosynthetic mechanism index of T2was lower than that of T1,but the reduction is smaller,and the amount of irrigation on T2 is 80 percent of that of CK,If the requirement of photosynthetic performance of leaves was reduced slightly,both water saving and photosynthetic performance can be realized.