Study On Anatomical Characters And Garden Application Of Several Species In Rhododendron L.

Materials of this study are based on the leaves, midvein, leafstalk, petal, scale, calyx and pedicel of 20 species of Ericaceae. Scanning Electron Microscope(SEM) and light microscope(LM) are used to observe morphology and anatomy characteristics of the materials. Simultaneously, the phylogeny relationship among correlative traits and the significance of ecological adaptation are discussed and the present situations and prospects of application of Rhododendron L. as Landscape Plants are also analyzed. The main results are as follows:(1) From the analysis on the morphology and anatomy characteristics of the Rhododendron L., the division of subgenus and group of Rhododendron L. is thought to be reasonable. Min tianlu and Fang ruizheng's notion that devised Rhododendron L. into 8 subgenus is agreed on.(2) It is shown that the leaf and floral epidermal cells are usually irregular or polygonal inshape using (LM). The patterns of anticlinal walls are straight, arched or undulate. The stomatal apparatuses are anomocytic and are usually found on upper epidermis, not on lower epidermis. The types of stomata is irregular. The shape of epidermal cells in subgen. Tsutsusi and subgen.Hymenanthes are straight or arched,with undulate in subgen.Pentanthera .It is shown that foliar trichome usually found on the bottom of upper epidermis, not all over of other petal epidermis using(SEM). There are more closely stomata at the top of lower epidermis than the bottom of lower epidermis using(SEM). Leaf, calyx, pedicel, scale epidermal features are described and micromorphological types are distinguished here according to morphological characters such as scale, gland, foliar trichome , cells ornamentation and stomatal apparatus of leaf epidermis.(3) Scale, gland, foliar trichome and processes of leaf, calyx, pedicel, petal, scale of Rhododendron L. are quite similar to the leaf upper and lower epidermis of them respectively, from which it is suggested the pedicel would be the transition form between leaf. The stomatal apparatuses are usually found on abaxial, not adaxial at floral organs.(4) There are many crystal contained cell in the leaves, midvein and leafstalk of Rhododendron L.. The results of predecessor's systematic evolution and ecological adaptation :Aound hundle→Almost-amphicribral hundle→Collareral hundle ,is agreed on. The theories that subgen.Hymenanthesis the original of Rhododendron is agreed on. Midvein are quite similar to leafstalk. The cross-section and vascular bundle shape of pedicel are quite difference at each subgenus and species. all these characteristics had a very important reference significance for systematic evolution and ecological adaptation. Just from the analysis of quantity characteristics, the size of the petal cell had a positive correlation to the thickness of the leaf.(5)The lepidote subgen. Rhododendron, which has both scales and papillae on scale, pedicel and leaf epidermis, differs distinctly from the elepidote Rhododendron using(SEM);three types of leaf and scale epidermis are identified in subgen. Hymenanthes, whereas four in subgen. Tsutsusi;except for R. championae and R. henryi, the species of subgen. Azaleastrum show similar morphological characters, i.e., dense stomatal apparatuses surrounded by ringed or discontinuous striates; There are more layer cells in palisade tissue in subgen. Hymenanthes than in other subgen. R. molle of subgen. Pentanthera differs from the species of other subgenera on morphological characters such as foliar trichomes, dense stomatal apparatuses with asymmetrical outer stomatal rims surrounded by undulate-striates, and no gland; Finally, the relationships between the closely related species are also discussed on the basis of leaf, calyx, pedicel and scale epidermal features.(6) The anatomical characteristics similarity of R.mariesii,R.daiyunicum and R. farrerae could reflect the close genetic relationship of them,but midvein and leafstalk of morphology and anatomy characteristics in R.daiyunicum are all annular sickle amphicribral reniform bundle,with Fan-ray amphicribral reniform bundle in R. Mariesii.They can be differ from each other by these morphology and anatomy characteristics. So the theories that R.mariesii and R.daiyunicum are two respective species is agreed on. R.naamkwanense is Varieties of R.pulchroides respectively Close relative relationship of the two species could be confirmed by their Similarities and differences by which the two species can also be distinguished. Midvein of morphology and anatomy characteristics in R.naamkwanense is Almost-amphicribral reniform bundle,with Fan-ray amphicribral reniform bundle in R. pulchroides. The shape of the pith is big in R. naamkwanense,but small in R. pulchroides.(7) From morphology and anatomy characteristics of leaves, midvein, leafstalk, petal, calyx, bract and pedicel, it is showed that Rhododendron L. have the higher ability of extension and environmental adaptation. Each subgenus and species of plants have its particular structure characteristics to adapt environment, but there was difference in ways of expression.(8) Rhododendron L. is an famous tree species which called 'the king of flower and tree' because of its abundant species, forms of plant, diversity of colors of flower, various kinds of leaves. Rhododendron L. has widely landscape application forms such as ground planting line, pot culture.Its abundant species are frequently disposed and landscaped in countyard, parks, scenic spots.They also had certain resistance and adaptability to bad environment. They played an important role in greening, beautifying the environment and maintaining urban ecology balance, so they were a kind of landscaping plants that had wide development prospect.