Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?

In woody dicots, the strip of cambium present between the primary xylem and phloem is the interfascicular cambium. The cells of the medullary rays adjoining the interfascicular cambium become meristematic and form the interfascicular cambium. This results in the formation of a continuous cambium ring. The activation of the cambium ring results in the cut off new cells. The secondary phloem is formed by the cells which are cut off towards the periphery cells. The secondary xylem is formed by the cells cut off towards the pith. The cambium being more active on the inner side, the amount of the secondary xylem produced is more than that of the secondary phloem. At some places the cambium forms the narrow band of parenchyma called the secondary medullary rays. These medullary rays pass through the secondary xylem and secondary phloem in the radial directions.

The secondary growth in plants:
i. Increases the girth of plants,
ii. Increases the amount of water and nutrients to support the growing number of leaves.
iii. Provides support to plants.

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Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or a dicot stem? Give reasons.

State the location and function of different types of meristems.

The transverse section of a plant material shows the following anatomical features:
(a) the vascular bundles are conjoint, scattered and surrounded by a sclerenchymatous bundle sheaths.
(b) phloem parenchyma is absent. What will you identify it as?

Draw illustrations to bring out anatomical difference between:
(a) Monocot root and dicot root
(b) Monocot stem and dicot stem

Anatomy of Flowering Plants

Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?