湖北海棠实生树童区与成年区形态学和细胞学比较研究

MORPHOLOGICAL AND CYTOLOGICAL COMPARISON BETWEEN JUVENILE AND ADULT ZONE LEAVES OF MALUS HUPEHENSIS

通过将湖北海棠（Ｍａｌｕｓｈｕｐｅｈｅｎｓｉｓ）实生树不同发育区接穗嫁接到一年生本砧上，建立一个遗传背景一致、所处发育阶段不同的童期研究实验系统，并采用显微图像形态定量分析系统对湖北海棠实生树童区和成年区及其嫁接植株形态学和细胞学进行比较研究．结果表明，实生树从童区向成年区转变后，其叶片细胞核ＤＮＡ相对含量增加，细胞ＲＮＡ合成增强，细胞核增大，但细胞变小，叶片叶肉组织分化程度提高，叶面积增大，叶片增厚；取实生树童区和成年区枝条嫁接到一年生本砧上，成年区嫁接苗当年就具有开花能力，而童区嫁接苗仍保持童年特征，不具备开花能力，ＰＰ３３３不能诱导童区嫁接苗开花，童区嫁接苗分枝能力较强，叶形与实生树童区和同龄实生苗相似．成年区嫁接植株叶片细胞ＲＮＡ含量依然显著高于童区嫁接植株，尽管叶片细胞核ＤＮＡ含量和细胞核大小仍有增加趋势，但增加幅度显著减少，两者叶片叶肉组织均表现为阳性结构．

The scions taken from different spatial positions of the apomictic crabapple seedlings ( Malus hupehensis ) were grafted onto young stocks to produce the materials with genetic homogenity and different developmental stages. Morphological and cytological studies with by microspectrophotometric technique were carried out to inspect their quantitative changes between juvenile and adult zone leaves, and between the leaves of the grafted plants with scions in juvenile and adult zone of M. hupehensis . The results indicated that relative contents of DNA and RNA were increased significantly; nuclei remarkedly enlarged but cells decreased in size during the transition from juvenile (J) to adult(A) zone of the mature seedling. A histological investigation showed that adult zone leaves had much thicker palisade and spongy tissues, with longer cells than those in juvenile zone leaves.The adult zone leaves were significantly larger and thicker than juvenile zone leaves. The grafted plants with adult zone scions (A/S) were able to flower while the grafted plants with juvenile zone scions (J/S) could not flower even if growth inhibitor PP333 was used. J/S had stronger branching ablility and their leaf shape was similar to juvenile zone and young seedling. Grafting treatment remarkedly reduced and even eradicated the significant characteristic differences between juvenile and adult leaves mentioned above except RNA relative content and leaf shape. The internal leaf structures of J/S and A/S were very similar. The changes of DNA and RNA contents and their roles in the transition from juvenile to adult zone were discussed.