Multicellular organisms have specialised cells, tissues, organs and organ systems. A tissue is a group of cells positioned and designed to perform a particular function. An organ is a structure made up of a collection of tissues that carry out specialised functions. In plants, the root, stem and leaves are organs, whereas xylem and phloem are tissues.
1. Meristematic Tissues (Meristems)
Plant tissues are classified into two types: meristematic tissues and permanent tissues. The term 'meristem' is derived from the Greek word 'Meristos', which means divisible or having cell division activity. Meristematic tissues are groups of immature cells capable of cell division, found in zones where growth takes place – the apex of stem and root, leaf primordia, vascular cambium and cork cambium.
Features: living, thin-walled cells with dense cytoplasm, large nuclei and small vacuoles; they undergo mitotic division and do not store food.