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MERISTEMS AND GROWTH
HOW DO PLANTS GROW?
Plants grow from  localized areas called meristems.

meristem -  discrete regions or groups of cells that possess continued cell division for the 
                   life of the plant or that organ.

PLANTS EXHIBIT TWO TYPES OF GROWTH
1) Primary Growth - growth in length that gives rise to primary (herbaceous) tissues
                                called the primary plant body.

    2 Types of meristems give rise to primary growth
    a) apical meristem orapex- the growing points located at the tips of stems and roots.

    b) intercalary meristem - the growth region at the base of grass leaves that causes
                                            leaves to elongate.

2) Secondary Growth - growth in width or diameter that gives rise to secondary (woody or
                                    corky) tissues called the secondary plant body.
                                    Secondary growth is due to lateral meristems.

          lateral meristem - meristematic regions along the sides of stems and roots.

    2 Types of lateral meristems give rise to secondary growth
    a) vascular cambium orcambium - a sheet-like meristem between the bark and wood
         along the sides of woody stems and roots; it gives rise to secondary xylem
         (commonly called wood) on the inside and secondary phloem on the outside.

    b)  cork cambium or phellogen - gives rise to the periderm (commonly called bark).