Functions of Supporting Tissues in Plants Roots

The root of a plant is subject to two forces:

• The pulling force on it due to the movements of the stem; and 

• The Crushing force due to the pressing effect of the dense oil medium on it.

   A dicotyledonous root has a wide cortex of turgid parenchyma. The xylem tissue forms a strong solid central cylinder. This arrangement of tissues helps to resist the pulling and crushing forces on root. In addition, dicotyledons also have an extensively branched root system which helps  to resist the pulling force on the roots. This type of root system and internal structure help to support the large spreading body form of dicotyledonous trees.

   A monocotyledonous root has a wide cortex and a large pith of turgid parenchyma. The xylem forms strengthening rods which are arranged in a ring around  the pith. This internal structure helps to resist the crushing force of the soil. Unlike dicotyledons, monocotyledons only have a shallow unbranched root system which cannot effectively resist pulling forced created by the movement of large stems. As a result, most monocotyledons are small herbaceous plants. Some monocotyledons with tall stems like the maize have prop roots which lessen the pulling forces on the ground roots.