女贞和白蜡树的树皮结构及次生韧皮部发育的季节变化

BARK STRUCTURE AND SEASONAL VARIATIONS OF SECONDARY PHLOEM DEVELOPMENT IN LIGUSTRUM LUCIDUM AND FRAXINUS CHINENSIS

摘要:

女贞（ＬｉｇｕｓｔｒｕｍｂｕｃｉｄｕｍＡｉｔ）和白蜡树（ＦｒａｘｉｎｕｓｃｈｉｎｅｎｓｉｓＲｏｘｂ）是白蜡虫的两种主要寄主树。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．它们的筛管分子具复筛板或单筛板，具Ｐ－蛋白质和筛管淀粉。伴胞为与筛管分等长的一列或单个细胞。筛管寿命在女贞中最长为一年，在白蜡树中则不超过８个月．形成层活动时间在女贞中是３月中下旬到１１月中旬，在白蜡树中是３月中下旬到１１月下旬．两种树木的木质部和韧皮部在３月中旬已开始分化，木质部和韧皮部分化停止的时间在女贞中分别是１１月中旬和１２月下旬；在白蜡树中分别是９月下旬和１１月下旬．两种树木在冬季都有部分分化的筛管分子，白蜡树中的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。女贞枝条冬季平均保留１７０．２μｍ的具功能韧皮部区；而白蜡树在径向仅保留数列细胞宽的具功能韧皮都区越冬．

Abstract:

Ligustrum lucidum and Fraxinus chinensis are two species of the major host trees for wax insect (Ericerus pela). From external to internal pets, the bark structure of both species includes periderm, cortex, fibre bundles of primary phloem and secondary phloem. Their sieve tube members eaist with compound or simple sieve plates, and they all contain P-protein and sieve tube scorch. Companion cells arranse in a row or single cell as long as the sieve tube member. The longevity of sieve tube in Ligustrum lucidum lasts 12 months, while in Fraxinus chinensis 8 months at the most. Obvious division of cambia in both species begins in mid to late March, but euds in mid November in Ligustrum lucidum and in late Novembe in Fraxinus chinensis. The differentiation of xylem and phloem of both species begins in mid March,but ends in mid November and late December in Lingustrum lucidum, and in late September and late November in Fraxinus chinensis. In winter, there are partially differentiated sieve elements in phloem of both species. Thais partinlly differentiated sieve elements in Fraxinus chinensis appear in autumn, mature in mid March of next year, and collapse during September and October. In branches of Ligustrum lucidum there is a overwintering and functional zone with average thickness of 170. 2μm in phloem, while the zone in Fraxinus Chinensis only several cell rows thick.