the plant tissue types

        The main classes of undifferentiated cells differentiated from meristematic cells (analogous to animal stem cells) to form the tissue structures of roots, stems, leaves, flowers and reproductive structures.

        Xylem cells are elongated cells with thickened lignified secondary cell walls. Xylem cells are specialized for conducting water, and first appeared on the plants during their transition to land in the Silurian period, more than 425 million years (see Cooksonia). Possession of xylem vascular plants define Tracheophytes. xylem tracheids noted, elongated xylem cells, the simplest of which have continued to lignified cell walls of the primary and secondary wall thickening in the form of rings, earrings or reticular networks. More complex perforated tracheid bordered pits characterized as a valve called gymnosperms. Ferns and other Pteridophytes and gymnosperms only xylem tracheids, while angiosperms have xylem vessels. members of the ship are xylem cells aligned hollow end to end, without end walls that are assembled into long continuous tubes. The bryophytes lack true xylem cells, but their sporophytes have a water-conducting tissue known as the hydrometra which consists of elongated cells of simpler construction.

         Phloem is a tissue specialized for conduction of food in the superior driving plants.The food is a complex process that takes place on the ground with the help of special cells called phloem cells. These cells conduct inter-and intra-cellular fluid (food - protein and other essential elements required by plants for their metabolism) through the process of osmosis. This phenomenon is called as the ascent of sap. Phloem consists of two types of cells, the sieve tubes and companion cells intimately associated. The sieve tube elements lack nuclei and ribosomes, and their metabolism and function are regulated by the nucleated cells adjacent partner. sieve tubes are joined end to end with final drilling between the plates known as sieve plates, which allow the transport of photosynthates from the sieve elements. Companion cells, connected to the sieve tubes through plasmodesmata, is responsible for loading the phloem with sugars. The bryophytes lack phloem, but sporophytes mosses have a simple tissue with similar function known as the leptome.

        Plant cells are specialized cells epidermal parenchyma covering the outer surfaces of the leaves, stems and roots. The cells in the epidermis of aerial organs are derived from the superficial layer of cells known as the tunica (L1 and L2 layers) covering the shoot apex of plants , while the bark and vascular tissues came from his coat inner apex of the outbreak known as the corpus (L3 layer). The root epidermis originates from the layer of cells immediately below the cap.

       The epidermis of all aerial organs, but not the roots, is covered with a wax-based cuticle and cutin polyester. There are several types of cells can be present in the epidermis. Prominent among them are guard cells of stomata, glandular hairs and clothing or trichomes, and root hairs of the primary roots. Production in the epidermis of most plants, only guard cells have chloroplasts. The epidermal cells of the main stem are thought to plant cells only with the biochemical capacity to synthesize cutin