In the life cycle of a moss, the predominant gametophyte consists of two stages. After the protonema stage, what is the name of the second stage of the gametophyte?

Introduction / Context:

Mosses are non vascular plants whose life cycle is dominated by the gametophyte generation. The gametophyte itself develops in two distinct stages, which are often shown in diagrams and described in textbooks. Understanding these stages helps students grasp the alternation of generations and the structure of bryophytes. This question asks for the name of the second stage of the moss gametophyte that follows the protonema stage.

Given Data / Assumptions:

• The plant group is mosses, a type of bryophyte.
• The life cycle is dominated by the gametophyte generation.
• The question states that the gametophyte consists of two stages.
• We know the first stage is the protonema stage.
• We must identify the second stage that comes after protonema.

Concept / Approach:

When a moss spore germinates, it produces a filamentous, green, algal like structure called the protonema. This is the juvenile, first stage of the gametophyte. From the protonema, buds arise that develop into the second stage, which is the leafy gametophyte. This stage has upright stems with small leaf like structures and forms the familiar cushion or mat of moss that is visible to the naked eye. The leafy stage bears sex organs (antheridia and archegonia) and eventually gives rise to the sporophyte. Therefore, the correct answer is the leafy stage, not protonema or sporophyte.

Step-by-Step Solution:

Step 1: Recall that moss spores germinate to form the protonema, a thread like structure. Step 2: Remember that small buds develop on the protonema and grow into upright leafy shoots. Step 3: Recognise that these leafy shoots form the second stage of the gametophyte and are often what we see as moss plants. Step 4: Note that the sporophyte with capsule is a separate diploid generation and not a stage of the gametophyte. Step 5: Select leafy stage with upright shoots as the second stage of the moss gametophyte.

Verification / Alternative check:

Life cycle diagrams of mosses in botany textbooks label the stages as protonema and leafy gametophyte. The protonema is shown as a creeping green filament, while the leafy stage is illustrated as erect structures with leaf like appendages. These diagrams also indicate the development of sex organs on the leafy stage. The sporophyte is drawn as a stalk and capsule growing from the gametophyte, reinforcing that it is a different generation. This consistent description confirms that the second stage of the gametophyte is the leafy stage.

Why Other Options Are Wrong:

Option A, Agar like stage, is not a recognised term in moss life cycles. Option C, Chlorella like unicellular stage, is incorrect because moss gametophytes are multicellular and filamentous or leafy, not unicellular algae. Option D, Protonema stage only, refers to the first stage and does not describe the second stage asked for in the question. Option E, Sporophyte capsule stage, belongs to the diploid sporophyte generation, not to the gametophyte.

Common Pitfalls:

Students may sometimes remember only the protonema as the gametophyte and forget that the familiar leafy moss is also part of the same generation. Others may confuse the leafy stage with the sporophyte because both are visible on the moss cushion. To avoid confusion, learners should remember that protonema and leafy plant together make up the haploid gametophyte, while the sporophyte is the stalk and capsule that grows from the gametophyte and produces spores.

Final Answer:

The second stage of the moss gametophyte after the protonema is the leafy stage with upright shoots.