Abstract:

The experiment of controlling irrigation on one-year-old seedlings and 18-year-old adult trees of Juglans regia `Xiluo 3' cultivated in pot and field respectively was conducted. Conclusions were as follows: 1) The stomatal exposure of the leaf, thickness ratio of palisade to mesophyll tissue, the thickness of leaf, the thickness of primary vein of trees increases with soil moisture, the stomatal density of lower epidermis and the density of epidermal cell decreases with soil moisture. 2) April, May and June are the key periods of water supplying, in this time the requirement of water is more than any other times for walnut tree. The requirement of water decreases gradually and the competence of drought tolerance improves continuously with the course of walnut growth. 3) The leaf water potential rises gradually from 8:00 to 14:00, then reaches the tiptop of a day, and it falls from 14:00 to 18:00.At the side of season, the water potential is continuously decreasing from May to October. 4) The content of chlorophyll of walnut leaves increases with the course of growth. The biggest increment is in April during one year. The content of chlorophyll increases with soil moisture, the biggest increment is 0.05 mg·dm^-2 . 5) In growing season, increasing soil moisture can promote the growth of the base diameter and height of young trees, and spring and autumn shoots of adult walnut tree, can raise the single fruit mass and the individual tree production, and decrease the fallen fruit. The increment of base diameter and tree height, and basal diameter and length of spring shoot of walnut are increased with soil moisture. 6) In arid and semiarid area of loess plateau, between April 1st and June 20th, maintaining 130～160 g·kg^-1 of the soil moisture can satisfy normal development of anatomic structure and growth of young tree. Between June 21st and October 31st, scarcely irrigation or no irrigation is good for the growth of spring shoot of walnut tree, the promotion of changing from growth to fruitage, and the realization of early fruiting and fertility and high quality.

Key words: Juglans regia, water of leaf, soil moisture, growth, yield