川黄柏和凹叶厚朴树皮及韧皮部季节变化

川黄柏和凹叶厚朴是两种重要的中药材．树皮由外向内为周皮、皮层、初生韧皮部的纤维束和次生韧皮部．它们的筛管分子具有复筛板或单筛板，Ｐ—蛋白质和筛管淀粉．伴胞为与筛管分子等长的一列或单个细胞．筛管寿命在川黄柏中最长为１年，在凹叶厚朴中则不超过８个月．形成层活动时间在川黄柏中是３月中下旬到１１月中旬，在凹叶厚朴中是３月中下旬到１１月下旬．两种树的木质部或韧皮部在３月中旬已开始分化，木质部和韧皮部分化停止时间在川黄柏中分别是１１月中旬和１２月下旬；在凹叶厚朴中分别是９月下旬和１１月下旬．在冬季均有部分分化的筛管分子，凹叶厚朴中部分分化的筛管分子于秋季形成，翌年３月中旬成熟，同年９～１０月瓦解，川黄柏枝条冬季平均保留１７０．２μｍ的具功能韧皮部区；而凹叶厚朴在径向仅保留数列细胞宽的具功能韧皮部区越冬．

Bark Structure And Seasonal Variations of Phloem in Phellodendron chinense And Magnolia biloba

Phellodendron chinense and Magnolia biloba are two species of important trees for chinese.Traditional pharmaceutical from external to internal parts,the bark structure of both species includes peridenn,cortex,fibre bundies of primary phloem and secondary phloem.Their sieve tube members are of compound or simple sieve plates,and they all contain P_protein and sieve tube starch.Companiou cells arrange in a row or single cell aslong as the sieve tube member.The longevity of sieve tube in Phellodendron chinense lasts 12 months,While in Magnolia biloba 8 months at the most obvious diviscon of cambia in both species begins in mid to late March,but ends in mid November in Phellodendron chinense and in late November in Magnolia biloba.The differentiation of xylem and phoem of both species begins in mid March,but ends in mid November and late December in Phellodendron chinense,and in late September and late November in Magnolia biloba.In winter,there are partially differentiated sieve elemenes in phloem of b