土壤水分状况对核桃生长和发育的影响

Effect of Soil Moisture Condition on the Growth and Yield of Juglans regia

以1年生西洛3号核桃品种的实生苗和18年生高接大树为材料，进行盆栽和野外定量控水试验。结果表明：1）随土壤含水量增加，叶片的气孔开度、栅栏组织，叶肉组织比值、叶片厚度、主脉厚度增大，下表皮气孔密度、表皮细胞密度减小。2）核桃生长的关键需水时期是4、5、6月份。随着生长进程的推移，树体的需水程度逐渐降低，抗旱性能不断增强。3）核桃叶水势的日进程是8：00—14：00逐渐升高，到14：00达到最大；此后，14：00-18：00又逐渐下降。季节性变化特点是从5月份开始就逐渐下降，而且为不可逆的变化。4）在核桃生长期内，叶绿素含量随生长进程的更替而逐渐增加，尤以4月份增幅最大。在同一时期内，叶绿素含量随土壤含水量增大而增加，最大增量为0．05mg·dm^-2。5）水分调控对增加核桃幼树树干基径、树高生长量，成年树春梢与秋梢生长量和果实质量，提高核桃单株产量，降低核桃落果率均有明显的作用。随土壤含水量增加，树干基径、树高生长量均增加。春梢基径和春梢长度均随土壤含水量增大而增大。6）在黄土高原干旱地区，4月1日-6月20日保持130—160g·kg^-1的土壤含水量即可满足核桃叶片解剖结构正常发育和树体正常生长的需要；6月20日-10月31日少灌水或不灌水，有利于核桃春梢生长和促进营养生长向生殖生长转化，实现早实、丰产和优质。

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.