Chapter 23, Problem 6A

Summary Introduction

Introduction :

The conifers are heterosporous, they form two spores one develop into male and other into female gametophyte. The female cone has two ovules, each undergo meiosis in the megasporangium and form four megaspore. Three of them get disintegrated and the remaining megaspore undergo mitotic division and form female gametophyte. The male cone are the pollen grains undergo meiosis and form micropores as they have small reproductive scale. The pollen grain are transported to the female reproductive part through air or wind. If this pollen falls near the micropyle that is the opening of the ovule, it get trap in a sticky substance termed as pollen drop. Once the pollen drop get absorbed inside the ovule the pollens is pulled close to the micropyle and there the pollen grain continue to develop.

Answer to Problem 6A

Correct answer :

The correct answer is option (D) megaspore.

Explanation of Solution

Explanation/justification for the correct answer :

Option (D)megaspore. After the meiosis division of ovule it produces four megaspores. From these four megaspore three will disintegrate and the remaining one will form the female gametophyte. So, the correct answer is option (D).

Explanation for incorrect answer :

Option (A) prothallus. The prothallus stage is the gametophyte stage of fern during its life cycle. After the germination of spore it leads to the formation of young gametophyte that is prothallus.So, this is an incorrect option.

Option (B) fertilized egg. After the disintegration of three megaspore the remaining formed the female gametophyte that is the eggs inside the archegonia.So, this is an incorrect answer.

Option (D) microspore. Microspore is the male gametophyte that is the pollen grain.So, this is an incorrect answer.