摘要
构树(Broussonetia papyrifera(L.)Vent.)虽属散孔材,但其形成层活动与大多数环孔材树种相似。从细胞形态看,4月5日仍处于休眠状态,4月15日芽虽未萌动,形成层带细胞却已呈活动状态,这时可看到两层左右新形成的未成熟木质部和未成熟韧皮部细胞。10天后芽逐步展开,新形成的木质部细胞达8-9层,韧皮部细胞达5层左右。4月26日前,未成熟的木质部细胞急剧增加,随即出现下降趋势;未成熟韧皮部细胞则一直到5月20日都持续缓慢地增加。木质部细胞分化成熟所需时间大约是韧皮部细胞的一半。构树休眠期形成层区域和韧皮部中的过氧化物酶同工酶的酶带最多,3月25日形成层细胞在形态上仍处于休眠状态时,形成层区域的过氧化物同工酶的Ⅱ组和Ⅲ组酶带中已各有一条酶带消失,随后其它组织中也发生一些变化,这些变化与体内IAA的水平及组织分化状态密切相关。
Five Broussonetia papyrifera (L. ) Vent. trees were selected in a natural stand located on the campus of Peking University,Beijing,China. The trees were ca. 5-6 years old,3-4 m tall,and had diameters of about 3 cm measured 1.2 m above ground level. They were samplied at monthly intervals between January 28 and March 25,then at ten-day intervals between March 25 and May 20,1991. On each occasion,one 3-year-old shoot was cut from the tree. Two blocks (about 1 cm ×1 cm) contained peridern,phloem,cambium and wood with more than one annual ring were cut from every shoot,fixed in FAA,and then were prepared for anatomical studies. And on each o-ccasion, 7 layers of tissues (from periderm to mature xylem)were scraped off from the shoots and 100 mg of separate tissues were randomly extracted in 0. 1 ml of 20% sucrose. The extracts were used for isoelectric-focusing in polyacrylamide gel slabs(85 mm×60 mm×1 mm). Benziding and odianisidine was used as substrate. After electrophoresis the gel slabs were placed in the substrate buffer until the isozyme bands were visible. Owing to the ring-porous structure of the wood of Broussonetia papyrifera, the cambial activity was comparable with that in the most ring-porous dicots. The cambium activity started about ten days before bud sprouting. On April 4,the dormant cambial zone consisted of ca. 4 cell layers. The trees did not sprout until April 16,but ca. 2 cell layers of immature xylem and phloem were formed concomitantly. Ten days later, 8-9 cell layers of xylem and ca. 5 cell layers of phloem were formed. The formation of immature phloem cells continued to increase slowly between April 4 and May 20, whereas that of immature xylem cells increased rapidly between April 4 and April 26,and then decreased between April 26 and May 20. It was suggested that differentiation of immature xylem into mature xylem lasted ca. 10 days,whereas that of immature phloem into mature one lasted ca. 20 days. There were totally 6 peroxidase isozyme bands in dormant cambial region and functional phloem. Variation of zymogram in cambial region occurred before cambial activity activated which is followed by more or less minor changes of bands in all other tissues. These indicated that several significant changes were related to the level of endogenous IAA and differentiation of vascular tissues.
基金
国家自然科学基金资助项目
关键词
构树
形成层
过氧化物酶
同功酶
Broussonetia papyrifera
Cambium
peroxidase isozyme
