Monday, 13 July 2020

Dehiscence - Class 12, Chap2, Lecture 7

Sexual Reproduction In Flowering Plants

Dehiscence:

Dehiscence is the process of rupturing of anther wall to release pollen grains. During the maturation of anther a lot of changes takes place in the walls of anther. The middle layer after giving its nutrients to the tapetum degenerate. The tapetum transfer these nutrients to the pollen sac and also convert them in special material called Ubisch body. when the microspore mother cell divide to form pollen grain at the same time tapetum release Ubisch body in microsporangia i.e., pollen sac and degenerate. The sterile cell which is present between two pollen sac also degenerate. Only the epidermis and endothecium remain intact . In the cells of endothecium alpha-cellulose deposition and callose band is present, but at some places these materials are absent which is known as stomium and these place become weak. Being hygroscopic in nature, when water dry up the wall of endothecium contract and become concave and incurved . Now due to this incurving process the weak stomium gets cracked and finally break-off causing the release of pollen grains.   

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