The Effects of Irrigation Techniques on Diurnal Variation of Photosynthetic Characteristics of Walnut Tree

Photosynthetic characteristics of walnut tree under different irrigation techniques were measured using LI-6400portable photosynthesis system and the correlations between net photosynthetic rate and influence factors of walnut trees were analyzed.The results showed that:①Diurnal variations of net photosynthetic rate,stomatal conductance and water use efficiency were all double-peak curves;Diurnal variations of transpiration rate and air temperature were single peak curves;Diurnal variations of air relative humidity and intercellular CO2concentration wereUcurves.②The net photosynthetic rate was positively correlated with air temperature,transpiration rate and stomatal conductance while the net photosynthetic rate was negatively correlated with air relative humidity,intercellular CO2concentration;the net photosynthetic rate of walnut tree was mainly influenced by stomatal conductance and intercellular CO2concentration,followed by the transpiration rate and relative humidity.③Compared with the surface irrigation, micro-irrigation treatment could improve water use efficiency of walnut,especially irrigation technique with 3tubes.So,irrigation technique with 3tubes is the optimal choice of supplying water for walnut tree.