黄檀属两种树木形成层的活动周期和次生韧皮部的季节变化

PERIODICITY OF CAMBIUM ACTIVITY AND SEASONAL CHANGES OF THE SECONDARY PHLOEM IN TWO SPECIES OF DALBERGIA

观察了南岭黄檀（Ｄａｌｂｅｒｇｉａ ｂａｌａｎｓａｅ Ｐｒａｉｎ）主干、思茅黄檀（Ｄ．ｓｚｅｍ ａｏｅｎｓｉｓＰｒａｉｎ）枝条形成层活动的周期，次生韧皮部的季节变化和筛管寿命。结果表明：１．形成层均为叠生型。２． 南岭黄檀形成层于４ 月末开始分裂，１１月初停止活动。韧皮部于１１ 月初完成分化，木质部到１２月才完成分化。思茅黄檀形成层于４ 月中旬到１０ 月下旬活动，１１ 月下旬韧皮部和木质部都已完成分化。３． 具功能韧皮部区在秋季最宽，达４００—６００ μｍ ；２—４ 月最窄，仅为２００—３７０μｍ ，此时筛管分子仍具Ｐ－蛋白质，筛板孔开放。４． 南岭黄檀、思茅黄檀的筛管寿命分别为８—１２ 个月和９—１１ 个月。５． 形成层休眠时韧皮薄壁组织细胞中有淀粉与草酸钙结晶积累，形成层活动时量渐减少。

Periodicity of cambium activity, seasonal changes of the secondary phloem and longevity of sieve tube in main trunk of Dalbergia balansae Prain and in the twig of D.szemaoensis Prain were observed. The results are as follows: 1.All cambia fall under the category of storied type. 2.In D.balansae cambial activity begins in late April and ends in early November.Phloem differentiation is completed by early November.Xylem differentiation ceases in December.In D.szemaoensis cambial activity continues from mid April to late October. Phloem and xylem differentiation ceases by late November. 3.The width of functional phloem zone is maximal(400—600 μm)in autumn and minimal (200—370 μm) in February to April.In overwintering, functional sieve tube elements contain P protein, and the pores of sieve plate are open. It could be one of the reasons that these two species are promising host trees of Kerria yunnanensis during winter.4. The longevity of sieve tubes in D.balansae and D.szemaoensis last 8—12 months and 9—11 months respectively. 5. During dormancy of cambium, the parenchyma cells of the secondary phloem contain large quantities of starch grains and calcium oxalate crystals, which decrease as cambium becomes active and remain little or even non visualized in summer.