Relationship between stem sap flow of Corylus heterophylla × Corylus avellane and environmental factors and photosynthetic parameters

Abstract:【Objective】In recent years, Ping’Ou hybrid hazelnut has become a new tree species devel-oped in Xinjiang area. The introduction and cultivation of Ping’Ou hybrid hazelnut have started in vari-ous parts of the south and north of Xinjiang. It has good ecological adaptability and good fruit quality according to the experimental observations. Therefore, it has great potential to be a new generation of economic tree species in Xinjiang. Due to the short cultivation time and the lack of production technolo-gy suitable for Xinjiang’s natural conditions, proper irrigation methods need to study. In the Hazelnut Demonstration Garden in Qapqal county, Yili, Xinjiang, the stem sap flow of 8 years of Ping’Ou hybrid hazelnut were monitored for one year. Determination of the influence of meteorological and photosyn-thetic factors on sap flow in different growth periods of Ping’Ou hybrid hazelnuts were carried ou to provide a theoretical basis for the scientific irrigation of hazelnut in arid areas.【Methods】Continuous measurement of the stem flow rate of Ping’Ou hybrid hazelnut was carried out in the full fruit developing pe-riod using the wrapped stem sap flow meter. A HOBO microclimate near the test site was installed to mea-sure solar radiation (PAR), air temperature (Ta), air relative humidity (RH), and wind speed (W). The photo-synthetic parameters of each plant's leaves were measured under sunny weather and natural light conditions  using the CIRAS-2 portable photosynthesis measuring system produced by the British company PP-Systems.The relationship between the characteristics of hazelnut stem sap flow and the changes of weather and photo-synthesis in different growth periods was also explored in the study.【Results】The stem sap flow rate var-ied greatly with day and night during the fruit developing period. During the day, the changing curve of sap flow rate was an“inverted U”shape, and there was only a very small sap flow during the night. The daily cumulative amount of stem sap flow was different in the different growing periods. The daily cu-mulative amount of stem sap flow was higher (2.57 L·d^-1) during the nutshell hardening period , it was lower(1.65 L·d^-1) during the fruit setting period. The leaf temperature during the whole fruit developing period was the main influencing factor in the diurnal changes of photosynthesis. The net photosynthetic rate had an impact on stem sap flow during young fruit fast-growing period, nutshell hardening period, and kernel development period. The transpiration rate has an effect on it during the fruit setting period, nutshell hardening period and the nut maturity. Among meteorological factors, solar radiation and atmo-spheric temperature are the main influencing factors on it during fruit developing period. Air humidity is the main influencing factor on it during the young fruit fast-growing period and nutshell hardening period. regression models of hazel trees in different breeding periods, the multiple regressions between the stem sap flow and meteorological factors and photosynthetic parameters were significant during the growing season.【Conclusion】The nutshell hardening period of the hazelnut trees is July in Yili, Xinji-ang when the trees grow vigorously. The stem flow rate is affected by environmental factors such as so-lar radiation, water vapor pressure difference, photosynthesis, etc. The orchard transpiration would con-sume a lot of water, and irrigation should be in operation in time during this period.