Biology XII Content
Tissue is a group of similar (e.g. parenchyma) or dissimilar (e.g. xylem and phloem) cells with similar functions or functions having the common origin. In the higher plants like angiosperms, on the basis of their division of labors, there’re basically following three types of tissues:
1) Epidermal Tissue: They are distributed on outer region. They are protective in nature. E.g. epidermis.
2) Ground Tissue: They are distributed in cortex and pith region. They help in food synthesis, storage and also provide the mechanical support. E.g. parenchyma, collenchyma, sclorenchyma.
3) Vascular Tissue: They are distributed in stellar region. They help in food synthesis and translocation. They also help in conduction of water and minerals. E.g. xylem and phloem.
Plant Tissues are generally classified as follows:
1) Meristematic Tissue: They have the high potential of cell division and do not have fixed shape and size. Such tissues are always living. They later on modify into permanent tissue. They are distributed in growing regions like root and shoot tips, buds etc.
2) Permanent Tissue: They lack the potential of the cell division but have definite shape and size. Such tissues can be dead or living. They carry out various functions. They are widely distributed in the regions like cortex, pith and stale. E.g. parenchyma, xylem etc.
3) Secretory Tissue: They are the tissues secreting like enzymes and hormones which are used by plants. They also produce some other products like resin, gums, latex, essential oils which are also commercially important. E.g. Latic ferrous and grandular tissues etc.