In order to determine the suitable grafting time and improve the survival rate of grafting, one-year-old branches of Walnut at different times were used as materials to study the periodicity of cambial activities and changes of stored starch with the method of coloration by safranin-hematoxylin and I2-KI. The results showed that: the cambial cell layers by 2-3 increased to 4-5 from mid-March to mid-April; the color of parenchyma cells stained by I2-KI gradually faded which indicated that starch content gradually decreased and the cambium entered into active phase; from mid-May to mid-June, the cell layers gradually increased from 6-7 to 11-12; the color of parenchyma cells disappeared which indicated that stored starch disappeared and the cambium entered into vigorous phase; from early July to mid-September,the cell layers gradually decreased from 9-10 to 5-6; the color of parenchyma cells gradually became darker; the starch content gradually increased; the activity of cambium became weaker; from mid-September to the end of September, the cell layers gradually increased from 5-6 to 8-9; the color of parenchyma cells gradually faded; the starch content gradually decreased; the activity of cambium strengthened; from late September to mid-November, the cell layers gradually decreased from 8-9 to 2-3; the color of parenchyma cells gradually became darker; the starch content gradually increased; and the activity of cambium became weaker.%为了确定核桃的适宜嫁接时期、提高嫁接成活率,以核桃1年生枝条为试材,采用番红-苏木精、I2-KI染色方法,对形成层活动周期及淀粉贮量的变化进行了研究.结果表明:3月中旬-4月中旬,形成层带细胞层数由2～3层增加到4～5层,经I2-KI染色的薄壁组织细胞颜色逐渐变浅,枝条中淀粉逐渐减少,形成层进入活动期;5月中旬-6月中旬,细胞层数由6～7层逐渐增加到11～12层,薄壁组织细胞未见蓝色出现,枝条中淀粉全部消失,形成层进入活动旺盛期;7月-9月中旬,细胞层数由9～10层逐渐减少到5～6层,薄壁组织细胞颜色逐渐变深,淀粉开始逐渐增多,形成层活动减弱;9月中旬-9月底,细胞层数由5～6层逐渐增加到8～9层,薄壁组织细胞颜色逐渐变浅,淀粉逐渐减少,形成层活动加强;9月底-11月中旬,细胞层数由8～9层逐渐减少到2～3层,枝条中薄壁组织细胞颜色逐渐变深,淀粉开始逐渐增多,形成层活动减弱.
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