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« Adaxially placed palisade parenchyma is made up of elongated cells arranged, vertically, parallel to each other., , « Spongy parenchyma: oval or round and loosely arranged cells below the palisade, parenchyma., , « Vascular bundles are seen in the midrib and veins., , « The vascular bundles are surrounded by a layer of thick walled bundle sheath cells., , Isobilateral (Monocotyledonous) leaf :, , « Itis similar with Dorsiventral leaf in many respect except o Stomata are equally distributed on upper and lower epidermis., o Mesophyll cells are not differentiated into palisade and spongy., « Ingrasses, certain adaxial epidermal cells along the veins modified themselves into, large, empty, colourless cells called bulliform cells., « Causes rolling of leaves to reduce transpiration during water stress., , SECONDARY GROWTH :, , « Apart from primary growth the dicot plant exhidit amincrease in girth is called, secondary growth., « The tissues involved in secondary growth ere two lateral meristem:, o Vascular cambium., o Cork cambium., , Vascular cambium :, , « Cells of cambium present between primary xylem and primary phloem is the, intrafascicular cambium., , «The cells of medullary rays, ecjoinng these intrafascicular cambium become, meristematic and form the inverfascicular cambium., , « Intrafascicular cambium aiid interfascicular cambium joined to form complete, cambium ring., , « The cambial ring becomes active and begins to cut off new cells both toward inner side, and outer side., , « Cells produced toward pith mature into secondary xylem., , « Cells produced towards periphery mature into secondary phloem., , « Secondary xylem forms a compact mass, retaining primary xylem in the centre., , « Atsome places, the cambium forms a narrow band of parenchyma, which passes, through secondary xylem and phloem is said to be secondary medullary rays., , , , , , , , Spring wood and autumn wood :, , « In temperate region during spring season, cambium becomes more active and produces, a large number of xylary elements having vessels with wider cavities. The wood formed, in spring is called spring wood or early wood., , « Inwinter the cambium is less active and forms fewer xylary elements with narrow, vessels thus called autumn wood or late wood.