The Characteristics Of Sap Flow Of Hanfu Apple Trees And Its Response To Environmental Factors

"Hanfu " apple tree is widely cultivated in Northeast China because of its high cold resistance.The study on the law of transpiration and water consumption can provide a theoretical basis for the establishment of suitable irrigation system.Therefore,taking Hanfu apple trees in Shenyang area as the research object,the TDP,soil moisture measuring system,photosynthesis measuring system and automatic meteorological station were used in this study.The sap flow rate,soil moisture dynamics and photosynthesis from young fruit stage to deciduous stage were monitored continuously from May to October 2017 and from May to October 2018.The characteristics of sap flow in Hanfu apple trees and its relationship with environmental factors were analyzed.The relationship model between sap flow rate and main meteorological factors at different time scales was established,and the law of transpiration and water consumption of Hanfu apple trees was clarified,which was suitable for the establishment of a suitable model for water consumption of apple trees in northeast China.The main findings are as follows:(1)Under the typical weather conditions,the sap flow rate showed high in daytime and low in nighttime,there was a single and wide peak shape in sunny days,double peak or multi-peak shape in cloudy days and single peak or multi-peak in rainy days.The start-up time and peak time of sap flow were the earliest in June,the last in October,and fall-time was the last in July and August.The nighttime sap flow rate showed a stable change trend,it changed slowly from zero to sunrise,and remained high from sunset to the next day at zero.Nocturnal sap flow was higher in May,September and October than in June to August.The overall level of 2018 single-day sap flow was 1.5 times higher than that in 2017.The changes of the inter-monthly sap flow showed a tendency to decrease,and the sap flow was the highest in July,and low in May and October.The sap flow rate in the north is higher than in the south,but it is smaller than in the east and west.(2)The correlation between sap flow rate and solar radiation,atmospheric temperature,saturated vapor pressure difference,wind speed and air relative humidity was the greatest at instantaneous scale,but had little correlation with soil temperature.The maximum correlation between sap flow and solar radiation was found on a daily scale,the saturated vapor pressure,and the atmospheric temperature was the second,the negative correlation between sap flow rate and wind speed and relative humidity,and the least correlation between sap flow rate and relative humidity.There was a negative correlation between sap flow rate and wind speed at monthly scale,and the correlation between sap flow rate and solar radiation was the least and no significant correlation was found.(3)There was a negative correlation between intercellular carbon dioxide concentration and sap flow rate at 0.01 level,the correlation coefficient was 0.6.The change trend of stomatal conductance was consistent with the trend of sap flow rate.The change of stomatal conductance was always prior to the change of sap flow rate,and there were different degrees of time lag in the growth period.(4)There was a significant positive correlation between sap flow and 10 cm soil moisture content,and a significant positive correlation between sap discharge and leaf area index at 0.01 level.(5)The deviation between the water requirement of Hanfu apple tree calculated by water balance and that of sap flow method is small in Hanfu apple trees,so the sap flow method can be used for monitoring the water requirement rule of Hanfu apple trees and can accurately calculate the transpiration amount of the Hanfu apple trees.In conclusion,the sap flow of Hanfu apple trees in cold areas of Northeast China is susceptible to environmental factors,sensitive to soil temperature and soil moisture,and the factors affecting sap flow in different time scales are also different.The evapotranspiration was large from June to September,and the water requirement was higher in July and August in Hanfu orchard.The influence of environmental factors such as solar radiation and atmospheric temperature on fruit tree transpiration and orchard water requirement was higher,so we should pay attention to replenishing water in July and August in time.Irrigation time should avoid the most intense solar radiation period,choose before sunrise or after sunrise,to reduce the water loss caused by evaporation.