Question

What is the ploidy of the following structures: gametophyte, seed, spore, sporophyte?

a. 1n, 1n, 2n, 2n$1n,1n,2n,2n$

b. 1n, 2n, 1n, 2n $1n,2n,1n,2n$

c. 2n, 1n, 2n, 1n $2n,1n,2n,1n$

d. 2n, 2n, 1n, 1n $2n,2n,1n,1n$

Short answer

The correct answer is option (b). 1n, 2n, 1n, 2n

$1n,2n,1n,2n$

Step-by-step solution

Introduction

The term "alternation of generations" refers to the lifecycle of plants that involves two types of plant bodies: gametophyte and sporophyte.

The haploid multicellular gametophyte alternates with the diploid multicellular sporophyte.

Reason for Incorrect options

Meiosis produces haploid cells, which are represented by 1n, while mitosis produces diploid cells.

A haploid structure is a gametophyte or spore, but a seed can never be haploid. Like a sporophyte, it is diploid.

Because a gametophyte and spore are always haploid in nature, and a sporophyte is always diploid, a 2n, 1n, 2n, 1nsituation is not possible.

Reason for the correct option

Meiosis, a process that reduces the number of chromosomes to half, produces haploid spores in a mature diploid sporophyte.

These haploid spores germinate, resulting in a haploid gametophyte. To make haploid gametes, the gametophyte goes through mitosis.

Reason for the correct option (Continuation)

A diploid zygote is created when two gametes unite and are fertilized. The zygote develops into a seed.

As a result, a seed grows into a diploid sporophyte under the diploid condition.

As a result, the ploidy of the gametophyte, seed, spores, and sporophyte are

1n, 2n, 1n and 2n respectively.