Understanding Cells in a Mature Pollen Grain

A pollen grain represents the male gametophyte in seed plants. The structure and composition of a pollen grain change as it matures. In flowering plants (angiosperms), the pollen grain undergoes mitotic divisions to form the cells present in a mature state, typically before or at the time of pollination.

A mature pollen grain is generally a two-celled structure. These two cells are:

• Vegetative Cell (or Tube Cell): This is the larger of the two cells. It has a large, irregularly shaped nucleus and abundant cytoplasm. The vegetative cell is responsible for forming the pollen tube, which grows down through the style towards the ovule after pollination.
• Generative Cell: This is the smaller cell. It is often spindle-shaped and floats in the cytoplasm of the vegetative cell. The generative cell undergoes further mitotic division (either before or after pollination, depending on the plant species) to produce two male gametes (sperm cells).

Let's look at the given options based on this understanding of a mature pollen grain:

• Option 1: Central cell and generative cell - The central cell is part of the female gametophyte (embryo sac), not the pollen grain. So, this option is incorrect.
• Option 2: Antipodal cell and vegetative cell - Antipodal cells are also part of the female gametophyte (embryo sac). So, this option is incorrect.
• Option 3: Vegetative cell and generative cell - As discussed, a mature pollen grain contains a vegetative cell and a generative cell. This option correctly identifies the two main cells.
• Option 4: Filiform cell and micropylar cell - Filiform apparatus is associated with synergids in the embryo sac (female gametophyte). There is no "micropylar cell" as a component of the pollen grain; the micropyle is an opening in the ovule. So, this option is incorrect.

Therefore, the cells present in the mature pollen grains are the vegetative cell and the generative cell.

Revision Table: Cells of Male and Female Gametophytes

Additional Information on Pollen Grain Development

The development of the male gametophyte from the microspore involves mitosis. Initially, a microspore mother cell undergoes meiosis to produce four haploid microspores. Each microspore then develops into a pollen grain.

This development includes:

• The microspore undergoes an unequal mitotic division to form a larger vegetative cell and a smaller generative cell.
• At this two-celled stage, the pollen grain is typically shed in many plant species (e.g., wheat, rice). This is the mature pollen grain referred to in the question.
• In some plants (e.g., peas, members of Leguminosae and Solanaceae), the generative cell divides further by mitosis before pollen is shed, forming two male gametes. In such cases, the pollen grain is three-celled at the time of shedding (one vegetative cell and two male gametes). However, the question asks about the cells present in a 'mature' pollen grain, and the two-celled stage is considered mature for most plants at the time of pollination. The generative cell's division into two male gametes can also occur after pollination while the pollen tube is growing.

Understanding the structure of the mature pollen grain is fundamental to understanding plant reproduction, particularly pollination and fertilization in angiosperms.