Difference Between Homospory and Heterospory

The key difference between homospory and heterospory is that homospory is the production of spores of the same size and same type, while heterospory is the production of spores of two different sizes and different sexes.

Plants produce sexual and asexual spores in order to reproduce sexually and asexually, respectively. Homospory and heterospory are two phenomena of spore production. Homospory refers to the production of morphologically identical spores. In contrast, heterospory refers to the production of dimorphic spores of two sizes and two sexes. Bryophytes and the majority of pteridophytes produce only one kind of spores, while some ferns and all seed plants produce dimorphic spores. It is believed that the heterosporous condition in vascular plants is evolved from the homosporous condition.

CONTENTS

1. Overview and Key Difference
2. What is Homospory
3. What is Heterospory
4. Similarities Between Homospory and Heterospory
5. Side by Side Comparison – Homospory vs Heterospory in Tabular Form
6. Summary

What is Homospory?

Homospory is the production of similar size, shape and type of spores. In other words, homospory refers to the production of asexual spores of the same kind.  These spores are uniform in size. They are asexual spores. They are neither microspores nor megaspores.

Homospory is a character of nearly all bryophytes and most pteridophytes (lower vascular plants). Therefore, most fern families are homosporous. In most pteridophytes, these spores germinate and produce bisexual gametophytes. However, in some species, these spores produce male or female gametophytes. In bryophytes, these spores produce unisexual gametophytes. Homosporous plants are gametophyte dominant and monosporangiate.

What is Heterospory?

Heterospory is the production of spores of two different sizes and sexes (dimorphic spores). Generally, these two different types of spores are known as microspores and megaspores. Microspores are male spores, while megaspores are female spores. They are produced from two different sporangia: microsporangia and megasporangia.

Microsporophylls are the leaf-like structures that bear microsporangia, while megasporophylls are the leaf-like structures that bear megasporangia. Microspores are small and numerous. Megaspores are large and fewer. Microspores germinate and produce male gametophytes. Megaspores germinate and produce female gametophytes. Heterospore production is a character of some pteridophytes and all seed plants. Heterosporous plants are sporophyte dominant and multisporangiate.

What are the Similarities Between Homospory and Heterospory?

• Homospory and heterospory are two phenomena seen in plants during spore production.
• Heterosporous condition in vascular plants evolved from the homosporous condition.

What is the Difference Between Homospory and Heterospory?

Homospory is the production of spores of only one type which are morphologically identical. Heterospory is the production of two different types of spores that are morphologically dissimilar. So, this is the key difference between homospory and heterospory. Moreover, the bryophytes and most pteridophytes are homosporous plants, while some pteridophytes and all seed plants are heterosporous plants. Besides, in homosporous plants, gametophytes are dominant, while in heterosporous plants, sporophytes are dominant. Thus, this is another significant difference between homospory and heterospory. Also, homosporous plants are monosporangiate, while heterosporous plants are multisporangiate.

The below infographic lists more differences between homospory and heterospory in tabular form for side by side comparison.

Summary – Homospory vs Heterospory

Homospory is the production of a single kind of spores which are neither microspores nor megaspores. Heterospory is the production of two different kinds of spores which are microspores and megaspores. Thus, this is the key difference between homospory and heterospory. Homospores are uniform in size and shape, while heterospores are different in size, shape and sex. Bryophytes and the majority of pteridophytes produce homspores, while some pteridophytes and all seed plants produce heterospores.

Reference:

1. “Homosporous Life Histories.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available here.
2. “Heterospory.” ScienceDirect Topics, Available here.

Image Courtesy:

1. “Sporic meiosis” By Sporic meiosis.png: Original uploader was Menchi at en. Wikipedia.Derivative work: Rehua (talk) – This file was derived from Sporic meiosis.png: (CC BY-SA 3.0) via Commons Wikimedia
2. “Loblolly male flowers” By Pinethicket at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia