毛白杨形成层的活动周期及其POD同工酶的变化

PERIODICITY OF CAMBIUM ACTIVITY AND CHANGES OF PEROXIDASE ISOZYMES IN POPULUS TOMENTOSA CARR.

北京地区生长的毛白杨 (PopulustomentosaCarr .)在春季芽膨大前 ,形成层带已经进入了恢复活动期。在芽展开后一周形成层进入活动期 ,细胞开始分裂 ,细胞层数也有所增加 ,同时分化出未成熟的韧皮部细胞。未成熟韧皮部细胞的数量在形成层活动初期快速增长 ,随后是一个持续而缓慢的连续过程。木质部的产生比韧皮部要晚 3周 ,未成熟的木质部细胞层数在开始变化不大 ,5月底～ 6月底 ,增长速度明显高于初期 ,随后便急剧下降。成熟木质部细胞的出现比成熟的韧皮部细胞要晚约一个月。与其他研究结果不同 ,毛白杨在4月底到 6月底这段时间 ,形成层细胞层数迅速下降 ,未成熟韧皮部细胞也略有减少 ,而未成熟和成熟的木质部细胞则大量增加。木质部在 9月底停止分化 ,较韧皮部要晚约 2 0d。 9月底形成层进入休眠期后 ,形成层细胞层数基本保持不变 ,直到翌年春天恢复活动。毛白杨形成层区域的过氧化物酶 (POD)同工酶在形成层活动期其活性低、酶带少 ,而恢复活动期和休眠期其活性高且酶带多 ,组织化学反应还表明 ,不同时期POD在不同的细胞和组织中的活性不同。本文对POD同工酶在形成层活动周期中的变化与其组织分化的关系进行了讨论。

The cambium of Populus tomentosa Carr. trees planted in Beijing have entered resuming phase before bud swelling. However, initiation of cambial activity with cell proliferation and increase in immature phloem cells was about a week later than bud sprouting. In active phase, phloem differentiation got rapid before mid-April and then continued up to early September with a slow speed. On the contrary, the xylem production commenced in late April (three weeks after appearance of immature phloem cells) and increased fleetly during June before declining in August. Meanwhile, the appearance of mature xylem cells was about a month later than that of mature phloem cells. Different from results of other researches, the cell number of immature and mature xylem of Populus tomentosa Carr. increased rapidly between late April to late June as cambium and immature phloem declined. The cambial tissue entered dormant phase from late September and remained till the following spring. After electrophoresis, there were totally eight peroxidase isozyme bands in dormant cambial region. The number and deepness of bands in zymogram during cambial activity phase were lower than that in other phases. Especially, POI 1, POI 2, POII 1 and POII 2 in peroxidase isozyme bands probably had a mutual relation with activity of cambial cell and differentiation of xylem. The result of histochemical reaction also showed that distribution and activity of peroxidase in different type of tissues or cells had significant difference. These indicated that peroxidase isozyme in cambial region was related to the level of endogenous IAA and differentiation of vascular tissues.