Sap Flow Characteristics of Kiwifruit Tree and Its Response to Environmental Factors

Abstract

【Objective】 To explore the variation characteristics of kiwifruit sap flow and its response to environmental factors. 【Method】 The thermal diffusion pin-type sap flow meter was used to monitor the sap flow law of kiwifruit trees in Guanzhong Plain, and the relationship between the sap flow of kiwifruit tree and environmental factors was analyzed. 【Result】 The daily-scale sap flow of kiwifruit tree showed a significant single-peak change during the whole growth period. The maximum value was 11.00 cm/h, which appeared in the fruit expansion period, and the minimum value was 0.18 cm/h, which appeared in the leaf expansion period. The peak value of hourly-scale sap flow rate in each growth period was: fruit expansion period > fruit maturity period > flowering and fruit setting period>shoot expansion period. The peak value of sap flow rate under different weather conditions was: sunny day>cloudy day > rainy day. The daily average sap flow rate of fruit tree was significantly positively correlated with air temperature, water vapor pressure deficit and net solar radiation, and the correlation coefficients were 0.842, 0.749 and 0.713, respectively. The results of path analysis showed that the net solar radiation had the greatest direct effect on the sap flow of kiwifruit tree, and the soil volumetric water content mainly affected the plant sap flow through the combined effect of net solar radiation, air temperature and soil temperature. There is an obvious time lag effect between meteorological factors and liquid flow rate. The time lag between liquid flow rate and solar net radiation is -30 min, the time lag between liquid flow rate and humidity is 60 min, and the time lag between liquid flow rate and air temperature and water vapor pressure deficit is 90 min. 【Conclusion】 The transpiration and water consumption of kiwifruit tree during fruit expansion period were the largest, so attention should be paid to the soil water status of kiwifruit tree during this period. In sunny weather, the sap flow of kiwifruit tree is the largest from 12:00 to 16:00, and the evaporation is also large, so irrigation should be avoided in this time to reduce the irrigation loss caused by transpiration.

Keywords

• kiwifruit tree
• sap flow
• environmental factors
• path analysis
• time delay