Difference between Microspore and Pollen Grain

Microspores and pollen grains are different forms of a male gametophyte. While microspores are small haploid spores formed after meiotic division, pollen grains are formed from the microspores after mitotic division. Let us look at both structures before differentiating between them.

What are Microspores?

Seedless vascular plants show heterospory, where they produce microspores and megaspores. Microspores are small haploid spores that develop into male gametophytes, and the megaspores into female gametophytes. The microsporangium of a gametophyte bears diploid microsporocytes that undergo meiotic division to produce haploid microspores.

The microspores have three layers, the outer perispore, the middle exospore and the innermost endospore.

In seeded plants such as gymnosperms and angiosperms, the microspores divide mitotically to produce pollen grains.

What are Pollen Grains?

Pollen grains are a differentiated mass of microspores in seeded plants, such as gymnosperms and angiosperms. The pollen is made up of two cells, one vegetative and one reproductive cell. The vegetative cells make pollen tubes that form a way for the reproductive cell (the sperm) to fertilize with the ovule.

Pollen grains are produced in a variety of shapes, sizes and surfaces that make them characteristic of the species.

The pollen grains have two layers, the exine made up of sporopollenin, and an inner layer called intine made up of cellulose or hemicellulose.

Read: Pollen Grains

The points of differences between microspores and pollen grains are tabulated below.

Microspore

Pollen Grain

Definition

Microspores are small haploid structures that give rise to the male gametophyte.

Pollen grains are haploid cells that form the male reproductive gamete of the plant.

Occurrence

Microspores are found in both seedless and seed plants.

Pollen grains are found in seed plants only.

Type of Division

Microsporocytes undergo meiotic division to form microspores.

Microspores undergo mitotic division to form pollen grains.

Process of Formation

The process of formation of the microspores is known as microsporogenesis.

The process of formation of the pollen grains is known as microgametogenesis.

Nutrients

It contains fewer nutrients.

It contains more nutrients.

Cellular Nature

Unicellular

Multicellular

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Frequently Asked Questions

Are pollen grains and microspores the same?

No, they are not the same. Microspores are haploid structures that divide mitotically to form pollen grains.

What is the difference between pollen and pollen grain?

A pollen grain is a single haploid cell, whereas pollen is a mass of pollen grains.

What are the different types of pollen grains?

On the basis of aperture, pollen grains are divided into three families, colporate, colpate and porate. Some other pollens are inaperturate.

Why are pollen grains different in shapes and sizes?

Pollen grains are different in shapes and sizes to fulfil the requirement of pollination.

Which plant has the largest pollen grain?

The genus Zostera has the longest pollen grain ranging up to 2500 μm in size.

Which is the largest nucleus in pollen grain?

The vegetative cell is the largest cell in the pollen grain that forms the pollen tubes for pollination.

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