Rabu, 10 Oktober 2012

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The Structure Of Leaf

The Structure Of Leaf

Leaft has several Function, such as a place for photosistesis, to absorb CO2 from environment, and to discharge excessive water. Leaf consist of some tissues, dermal tissue (epidermis), ground tissue (mesophyll), and vascular tissue.

  1. Dermal tissue Determal tissue of leaf is composed of a layer of compact cells. The cell walls are covered by cuticle (wax) and there are stomata (pores on leaf) between the cells, Stomata is formed by two guard cells derived from epidermal cells containing chloroplast. Stomata function as gas exchange organ. In aquatic plant, stomata is usually located on the upper surface of leaf, Whereas on land plants, it is located on the lower part of leaf.
  2. Mesophyll Mesophyll (ground tissue ) contains chloroplast (chlorophyll). Mesophyll is composed of two layers, upper layer in the from of palisade parenchyma and lower layer in the form of spongy parenchyma. The palisade parenchyma consists of narrow cells and contains a lot of chlorophyll. Spongy parenchyma (spongy tissue) consist of irregular rounded cells containing a lot of intercellular air spaces and few chloroplast. Spongy parenchyma is necessary in gas intake from environment through stomata.
  3. Vascullar Tissue (Vascullar Bundle) Vascular tissue of leaf froms a bundle called vein. Some veins from a pattern called leaf venation. There are two main types of leaf venation, pinnate-veined (palmate-veined) and parallel-veined.

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