11th Class Biology Anatomy of Flowering Plants

  • question_answer 62)
      Distinguish between the following. (a) Exarch and endarch condition of protoxylem                (b) Stele and vascular bundle                         (c) Protoxylem and metaxylem                                 (d) Interfascicular cambium and intra fascicular cambium (e) Open and closed vascular bundles                    (f) Stem hair and root hair


     (a) Exarch Protoxylem EndarchProtoxylem
    When the protoxylem is present towards the periphery and metaxylem towards centre in vascular bundle as it is found in roots. If the protoxylem is present towards the centre and metaxylem towards periphery in the vascular bundle as it is found in stem.
    (b) Stele Vascular Bundle
    Stele refers to conducting tissue or the central part of root or stem in plants. It comprises of vascular tissue, ground tissue and pith and limiting boundaries, i.e., endodermis and pericycle. Vascular bundle comprises of vascular/conducting tissues xylem and phloem. Some times cambium is also included as in dicots.
    (c) Protoxylem Metaxylem
    It is the first or earlier formed xylem. Matures before the growth and differentiation of plant organs. Protoxylem elements are smaller in diameter. Tyioses absent in protoxylem vessels. Fibres are absent. It is the later formed xylem. Matures after the growth and differentiation of plant organs. Metaxylemd elements are broader and greater in diameter. Tyioses are generally present. Fibres may be present.
    (d) Intra fascicular Cambium Inter fascicular Cambium
    Cambium present in between the primary xylem and primary phloem is called-intra fascicular cambium, as in dicot stems. The cambium present in between the two vascular bundles making the cambium continuous and forming a complete ring of cambium is called interfascicularconbium.          
    (e) Open Vascular Bundle Closed Vascular Bundle
    Cambium present in between the phloem tissue. Intra fascicular  cambium between the  present. Occur in the stems of nd gymnosperms. May be al or bicolateral. Xylem and not in direct contact with her due to cambial string. Intra fascicular cambium results in secondary growth. Cambial activity secondary phloem and secondary xylem that push primary phloem and primary xylem away from each other. Cambium is not present in between the xylem and phloem tissue. Intrafascicular cambium absent. Occur in leaves and monocot stems. May be collateral or concentric. Xylem and phloem are in direct contact due to back of cambial string. No such activity found. No such activity found.
    (f)Root Hair  Stem Hair
    Root hairs are unicellular It increase the surface area of root for absorption of water and minerals. Stem hairs are multicellular They are epidermal outgrowths known as trichomes. They help in preventing water loss due to transpiration.

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