Anatomical Characteristics Of Vegetative Organs Of Four Species Of Malus Plants In Western Sichuan Plateau And Their Drought Resistance Strategy Evaluation

In this dissertation, we mainly focus on the wild Malus toringoides,Malus transitoria, Malus baccata, Malus hupehensis in Western Sichuan plateau. The 32 selected anatomical characteristics of vegetative organs in terms of xeromorphic indices were observed and measured with paraffin sectioning method and NaOCl method.The drought resistance of those plants were analyzed and evaluated by the methods of ANVOA, principal component analysis and membership function.And we preliminarily verified the differences of anatomy and response strategies of drought resistance.The results were showed as follows:(1). The anatomical structure of vegetative organs of four Malus were basically similar:The root was composed of periderm organization and vascular tissue, non-medullated. The stem was composed of periderm organization, cortex parenchyma, vascular tissue and pith; The leaf was typical bifacial leaf, thick cutical was attached to the epidermis cells, there were not stomata on the upper epidermis, while a dense stomata distribution was observed on the lower epidermis, in addition, the main vein had only one big collateral vascular bundle.(2). Four species of Malus plants had specialized structures occurred in their organizations.The width of xylem ray in root system increased ranging from 6 to 8 rows, resulting in increasing of the axial transport of water benefited from this structure. Furthermore, the sclerenchymatous cells of phelloderms, sclerenchymatous cells in perimedullary zones and the'pseudo parenchymal cells' around vessels also showed a specialized behaviors on increment of mechanical support for their self-weight. Also, the longitudinal ridges and mesophyll tissues existed in leaf stalks were the specialization of leaves for ensuring photosynthesis. Additionally, the spininess heave observed in air holes of Malus toringoides was specialized from cuticular membrane, reflecting specialization of leaves structures to control water desorption.(3). Fourteen indices including the thickness of xylem in root, the thickness of phloem in root, ratio of xylem in transverse section in root, the thickness of phellodem in root, the radius of pith in stem, ratio of xylem in transverse section in stem, ratio of phloem in transverse section in stem, the thickness of leaves and so on were selected as typical items for evaluation of drought resistance of four plants. The order of drought resistance capability of four species of Malus plant was presented as follow:Malus toringoides>Malus baccata>Malus transitoria>Malus hupehensis.(4). Kinds of countermeasures would be applied by plants to response adversity.Malus toringoides took the protective, tolerant and strong types of countermeasures with relative thicker cuticula, epidermic cells of leaves and well-developed conductive organization in root and stem. Malus transitoria possessed the economical, strong and resistant countermeasures, which indicated not only through dual-effect of air holes, also advanced piths in stem and strong phloem, to response drought stress; The main countermeasures of Malus baccata were a strong and antagonistic way, resulting from well-developed assimilating tissues, phloem in stalk and the vessels with long hole diameters, in order to respond drought setting; Malus hupehensis took the strong, economical and tolerant countermeasures using well-developed vascular bundles, small air holes, big piths in stems and advanced structures in root including phelloderm and phloem to reflect drought stress.