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Arrangement of Tissues in Stems

Tissue distribution in Monocotyledonous and Dicotyledonous plants

  • Vascular bundles are the main support tissues in plants.
  • In monocotyledonous stem they are scattered all over the stem.
  • while in dicotyledonous stem they are found in a ring or rings.
  • In monocots the xylem and phloem alternate around with pith in the centre.
  • In dicots of the xylem forms a star in the centre - there is no pith.
  • Phloem is found in between the arms of xylem.
  • Dicotyledonous plants have cambium which brings about secondary growth resulting in thickening of the stem and root hence providing support.
  • Secondary xylem becomes wood, providing more support to the plant.

Role of support tissues in young and old plant

Plants are held upright by strengthening tissues ;

  • parenchyma,
  • collenchyma,
  • sclerenchyma
  •  xylem tissue.
  • Parenchyma and collenchyma are the main support tissues in young plants.


  • They are found below the epidermis.
  • They form the bulk of packing tissue within the plant between other tissues .
  • They are tightly packed and turgid they provide support.


  • Their cell walls have additional cellulose deposited in the corners.
  • This provides them with extra mechanical strength.

Sclerenchyma –

  • Their cells are dead due to large deposits of lignin on the primary cell wall.
  • The lignified wall is thick and inner lumen is small, hence provide support.
  • Sclerenchyma fibres are arranged in elongated and in longitudinal sheets giving extra support.
  • They are found in mature plants.

Xylem –

  • Has two types of specialised cells.
  • Vessels and tracheids.
  • Vessels are thick-walled tubes with lignin deposited in them.
  • They give support and strength to the plant.
  • Tracheids are spindle-shaped cells arranged with ends overlapping.
  • Their walls are lignified.
  • They help to support and strengthen the plant.

Plants with weak stems obtain their support in the following ways.

  • Some use thorn or spines to adhere to other plants or objects.
  • Some have twinning stems which grow around objects which they come into contact with.
  • Others use tendrils for support.
  • Tendrils are parts of a stem or leaf that have become modified for twinning around objects when they gain support.
  •  In passion fruit and pumpkin, parts of lateral branches are modified to form tendrils.
  • In the morning glory, the leaf is modified into a tendril.