Question

Prothallial cells in pollen of Cycas are found to,be:
(A) One
(B) Two
(C) Three
(D) Four

Answer 1

Hint: Prothallial cells are produced by the first division of the microspore in a gymnosperm
The gymnosperms are heterosporous; they produce haploid microspores and megaspores.
In Cycas male cones and female cones are borne on different trees.

Complete answer:
1.Each male cone in Cycas is known as microsporophyll.
2.Each microsporophyll measures about 3-5 cm long and 12-13 mm wide.
3.Microsporophyll contains 3-6 microsporangia or the pollen sacs.
4.Microsporangium contains numerous microspore mother cells.
5.Each microspore mother cell forms numerous microspores of pollen grains by reduction division.
6.Microspore is the first cell of the male gametophyte.
7.Germination of the microspore begins within the microsporangium.
8.At first, the microspore nucleus cuts off a small persistent cell called a prothallial cell at one end and an antheridial cell at the other end.
9.Antheridial cell divides into a smaller generative cell and a large tube cell.

Hence, the correct answer is option (A)

Note: 1.Cycas is a gymnospermic plant.
2.All gymnosperms do not have the same number of prothallial cells.
3.Prothallial cells are considered to be the vestige of fern prothallus.