CBSE Class 11-science Answered

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• The first cork cambium is formed by the dedifferentiation of the outer part of the cortex.
• As the stem increases in girth, the epidermis and the cortex are replaced by another meristematic tissue called the cork cambium.
• It is also called phellogen.
• The cells of the phellogen are thin-walled, rectangular and narrow.
• The cork cambium is 2–3 layers thick.
• Cells of the cork cambium cuts off cells peripherally and towards the centre.
• Cells on the peripheral region form the cork cambium or phellem.
• The walls of cork cells have depositions of suberin because of which cork becomes impermeable to water.
• Cells on the inner region form the secondary cortex or phelloderm. The cells of this region are parenchymatous.
• The cork cambium (phellogen), cork (phellem) and secondary cortex (phelloderm) are collectively called periderm.
• The layers peripheral to phellogen die and slough off because of the pressure exerted by the activity of the cork cambium.
• All tissues exterior to the vascular cambium are collectively called bark.