Studies On Anatomy Structure Characteristics Of Some Cycads And Adaptation Of Them And Enviroment

This study applies the method of comparative anatomy to study structure characteristics of vegetative organs of 4 species of Cycads distributed and introduced long-term in china and two species of Cycads introduced and cultivated from abroad. It could be probe into the properties distinction, evolutional relationship of every species, the relationship between them and the environment and provides some theoretical guidance for cultivation and field protection of Cycads.The experimental results as follows:(1) In general, the roots of Cycads have two types, they are normal root and storage root, and some species also have coralloid root. The normal root and the storage root have many kinds of structure types, such as big and small normal root and storage root of C.segmentifida, diarch norrmal root and triarch normal root of C.ferruginea, big and small storage root of C.siamensis and C.sp and old storage roots of C.sp. Secondly, pith-fibres are seen in pith of triarch normal root of C.ferruginea, which was not reported in the past study of Cycads. Phloem and pith of C.ferruginea contain crystal cells, but none or a few are discovered in theother species. Thirdly, septate stone cells are discovered in phloem of every type of root of C.siamensis and small storage root of C.segmentifida. In addition, sepate stone and non-sepate stone cells are discovered in cortex of big and small normal roots of C.segmentifida. It was never reported previously.(2) Stem of Cycads consists of periderm, cortex, vascular tissue and pith. Their common characteristics are that, protection tissue consists of death cells filled with suberization and lignification, and the leafbases surface of most species deposit a large number of lignification, stem of all species possess of abundant cortex, mucilage distribute in cortex and pith, different sizes and various vascular bundles distribute in cortex and one part is scattered, another take on the appearance of many rings shape in transverse section. Usually, vascular tissue has many growth rings. The width of every growth ring is different. Every ring is composed of inner xylem and outer phloem. In the four species, the thickness and the number of rings of vascular tissue have tendency of increasing from top to bottom other than C.ferruginea, whose vascular tissue of all three parts stem consists of two growth rings. Seeing from vertical variation, it is showed that, in these 4 species whose stem have intact three parts, the stem diameter of C.ferruginea increase sequentially from top to bottom, while the other three species is the mid stem >the bottom part > the top part. In the same tissue, from top to bottom, distribution trend of crystal cells and tannin cells are form absence to presence and from few to many. In addition, phelloderm of epidermid of C.ferruginea and C.siamensis consist of overall wallof stone cells being thicken, which was never reported before.(3) Leafstalk of Cycads plant generally has a lot of mucilage and vascular bundles. There is a phenomenon that some vascular bundles amalgamate each other in C.ferruginea, C.siamenswas and C.stangeria. One layer hypodermal is beneath the epidermis of leafstalk of C.ferruginea and two layers are beneath the epidermis of leafstalk of C.siamensis. The rest does not have hypodermal, but two layers net-like thickening are beneath the epidermis of leafstalk of C.segmentifida, C.debaoensis and C.sp and two layers neutral cells between thin-walled cells and thick-walled cells are beneath the epidermis of leafstalk of C.stangeria. Mechanical tissue exists in all investigated Cycads and the thickness of mechanical tissue is C.ferruginea > C.debaoensis > C.segmentifida> C.sp > C.siamensis > C.stangeria. Apart from C.stangeria, surrounding of vascular bundle of other 5 Cycads has vaginal structure which is composed of continuous one layer of medial thick-walled cells and encloses vascular bundle. And vaginal structure of C.debaoensis and C.siamensis contained crystal cells.(4) The thickness of pinna of these six Cycads is C.siamensis > C...