The Studies On The Photosynthetic Characteristics Of Walnut In Field

Photosynthesis is the basis for crop yield. It's necessary to study the photosynthetic character of fruit trees in order to improve the yield and quality. In this experiment, the patterns of diurnal variation of net photosynthetic rates(Pn) of Hebei-walnut (Juglans hopeiensis Hu ) and English walnut (Juglans rcjia L. ) were documented in an open gas analysis system of model(Cl-301PS). The curve of seasonal variation and the main influence factors were also investigated, and the values of Pn of twenty varieties were measured. The main results were as follows:1 The curves of diurnal change of Pn of Hebei and English walnuts showed two peaks, there were obvious "midday rest".2 From April to October , double peaks appeeared in the curve of seasonal variation of Pn of hebei-walnut . With the first peak appearing in May, with the second peak appearing in August. However the curve of seasonal variation of Pn of English walnut showed single-peaked. With the peak occurring in May.3 The light compensation and light saturation points in hebei-walnut leaves were 10umol.m2.s-1, 1643umol.m2.s-1 respectively, the optimum temperature of Pn was 29℃.Moreover the light compensation and light saturation points in English walnut leaves were 20umol.m2.s-1, 1610umol.m2.s-1 respectively, the optimum temperature of Pn was 27℃.4 The diurnal variation of Pn in hebei-walnut was influenced by light intensity, leaf temperature and intercellular CO2 concentration.The diurnal variation of Pn in English walnut was influenced by: light intensity, leaf temperature, transpiration rate, stomatal conductance and intercellular CO2 concentration. The seasonal variation of Pn in hebei-walnut was affected by transpiration rate, chlorophyll content and activity and intercellular CO2 concentration.The seasonal variation of Pn in English walnut was affected by transpiration rate, chlorophyll content, leaf temperature and intercellular CO2 concentration.5 There were significant difference in varieties of Pn of walnut and seedlings of varieties of Pn of walnut, and positively correlation significantly were testisfied.6 From flowering to fruit maturity the Pn of leaves on the bearing shoots were higher than that on the growing shoots. After fruit maturity the Pn of leaves on the bearing shoots were lower than that on the growing shoots.