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Plant Tissues and Anatomy — Biology STD 11 Science — Question

Maharashtra BoardEnglish MediumSTD 11 ScienceBiologyPlant Tissues and Anatomy5 Marks
Question
Explain how periderm is formed?
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Answer

Formation of periderm:
As the stem increase in diameter due to activity of vascular cambium, the outer cortical and epidermal layer get ruptured.
Thus, it becomes necessaiy to replace these cells by new cells.
  1. Phellogen (cork cambium) develops in extrastelar region (cortex region) of the stem.
  2. The outer cortical cells of cortex become meristematic and produce a layer of thin walled, rectangular cells. These cells cut off new cells on both sides.
  3. The cells produced on outer side develop phellem (cork), whereas on the inner side produce phelloderm (secondary cortex).
  4. The cork is impervious in nature and does not allow entry of water due to suberized walls. Secondary cortex is parenchymatous in nature.
  5. Phellogen, phellem and phelloderm constitute periderm.

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