CBSE Class 12-science Answered

The family Cyperaceae belong to the major group Angiosperms.

We know that for the production of 100 seeds, 100 female gametes and 100 male gametes are required. In cyperaceae family, one functional microspore is produced during single meiotic division. Likewise, one functional megaspore is produced during single meiotic division. Hence, 200 meiotic divisions in total are required to produce 100 seeds.

In Cyperaceae family, out of the 4 microspores and 4 megaspores produced in anther and carpel respectively from one meiotic division each, only one survives and the rest three degenerate. This is an abnormal behaviour shown by the members of the Cyperaceae family, which is against the n + n/4 division rule, where n represents the number of seeds. This rule helps to determine the number of meiotic divisions srequired to produce seeds in case of abnormal angiospermic plants.

In our example, for producing 100 seeds, the total number of meiotic divisions required are 100 + 100/4 = 125. But in the case of Cyperaceae family, instead of n + n/4, the rule becomes 2n and hence, 200 meiotic divisions are required to produce 100 seeds.