Chapter 23, Problem 2A

Summary Introduction

To analyze:

The correct term to complete the sentence.

Introduction :

The sporophytic and gametophytic stages are the two stages of fern life cycle. The sporophyte plants are diploid while the gametophyte plants are haploid. This phenomenon of life cycle is considered as alternation of generations. In the very first stage, the spores are formed and germinate to grow into small heart-shaped plant that are the gametophytes. Both the egg and sperm cells are formed in the gametophyte and fertilize it. Once the fertilization is over, the adult fern will start growing. In the second stage of life cycle, the fertilized gametophytes look like a mossy growth.This will be developed to young fronds rising out of the moss.

Explanation of Solution

The prothallamus is the gametophyte of the fern. They develop after the germination of spores. They consist of chloroplasts, hence, involve in photosynthesis. The prothalli sometimes grow into archegonia and antherdia, it is a flagellated sperm that require water to reach archegonia. While a thread-like structure of cellsthat is observed in the early stage of mosses life cycle is considered as protonema.

Conclusion

The prothallamus is a gametophyte of a fern not protonema.