Study On The Photosynthetic And Tree Water Transportation Characteristics Of Prunus Armeniaca L. In Turpan Basin

In this study,we measured the photosynthetic fluorescence indicators,xylem sap flow rate and stem diameter of prunus armeniaca cv.‘Suletan’and prunus armeniaca cv.‘Xiaobaixing’in Turpan Basin,and simultaneously monitoring of the meteorological factors of the orchard.In order to provide a theoretical basis for high efficient and water saving cultivation of early ripening prunus armeniaca L.in arid areas,we analyzed the changes of the leaf photosynthetic fluorescence indicators,sap flow rate and stem diameter changes on daily and seasonal scales,as well as the response characteristics to environmental factors,so as to clarify the photosynthetic response mechanism of prunus armeniaca L.to the unique climate of the Turpan basin,and to discuss the relationships between trunk water movement pattern of prunus armeniaca L.and environmental factors.The main findings are as follows:（1）The annual average temperature of the apricot orchard in Toksun County,Turpan was14.03℃,the lowest temperature was-21℃,the highest temperature was 44℃,the annual temperature difference was 65℃;The annual average relative humidity was 52.08%,the highest relative humidity was79.02%and the lowest relative humidity was 26.64%;In July the monthly average light intensity was the highest,reaching 56894.92 Lux,and in December it showed its lowest point,only 736.43 Lux.;The annual cumulative rainfall was 9.7 mm,and the total number of rainy days was 17 d;The maximum precipitation occurred in August,reaching 1.42 mm;The number of windy days in a year reached 143 days,the annual average wind speed was 6.21 m/s,and the wind direction was mainly northwest wind.（2）The diurnal changes of P_n of the two varieties showed a"double peak"curve;the photosynthetic"noon break"was caused by non-stomatal limiting factors.In July,the values of C_qp,Φ_PSⅡ,F_m,F_v/F_m,F_v/F_o of the two varieties were the lowest,while the values of C_NPQ and F_owere the highest,and they were significantly different from the measured values in other months（P<0.01）.The P_n of the two varieties was positively correlated with G_s,T_r,Ins _WUE,PAR,and negatively correlated with C_i,L_s,and the correlation coefficients of P_n with C_i,G_s,PAR were the highest.（3）With the increase of PAR,the P_n,G_s and T_r of the two varieties increased to varying degrees,Ins _WUE first increased and then decreased,while C_i decreased significantly;P_nmax,LCP,and the AQY of prunus armeniaca cv.‘Suletan’was 7.57%,24.94%,50.00%higher than that of prunus armeniaca cv.‘Xiaobaixing’respectively.（4）The sap flow rate showed a’broad peak’curve,with being higher in days and lower at nights;Average unit time sap flow and the average daily sap flow were the highest in July,which were 0.469 L/h and 11.27 L/d respectively;The start-up time of the sap flow on a sunny day was 1h earlier than that on a cloudy day;The start-up time of the sap flow in summer was around7:30～8:00,which is 1 h earlier than that of spring and autumn,with a long duration and large flow amount for per unit time;The sap flow rate was significantly positively correlated with T_a,VPD and SR（P<0.05）,and was significantly negatively correlated with RH（P<0.05）.（5）The diurnal changes of the stem diameter of prunus armeniaca L.was close to a"U"-shaped curve,reaching the daily maximum stem diameter around 6:00～8:00 in the morning,and decreasing to the daily minimum around 17:00～20:00 in the afternoon;MDS was higher,when the soil water content was low than that when the soil water content was high;When the soil water content was low,DG showed negative growth trend;MDS was positively correlated with T_a,SR and VPD,and negatively correlated with RH;DG was positively correlated with RH and negatively correlated with other environmental factors.To sum up,grown under the high temperature and strong light conditions in the Turpan Basin,prunus armeniaca L.release excess energy in the form of heat dissipation to adapt to the strong light environment,and increase its transpiration rate to reduce the leaf temperature,so as to adapt to the high temperature environment.In summer,sap flow,transpiration water consumption and stem diameter shrinkage all increase,Therefore,during summer days,the irrigation frequency should be appropriately increased,and the irrigation time should be chosen before sunrise or after sunset in order to avoid evaporation and loss of irrigation water.