What is the Difference Between Homospory and Heterospory?

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The main difference between homospory and heterospory lies in the type of spores produced by the plants.

Homospory refers to the production of identical spores in size and shape. This phenomenon is observed in Bryophytes and the majority of ferns. In homosporous plants, a single type of germ cell is produced, and these spores give rise to bisexual gametophytes that have both male and female reproductive structures. Since both male and female structures are present on the same gametophyte, homosporous plants commonly undergo self-fertilization. Gametophytes are the dominant generation in homosporous plants.

Heterospory refers to the production of two different types of spores, termed megaspores and microspores. This is a common feature in Pteridophytes and various seed plants. The larger spores, or megaspores, give rise to a female gametophyte, while the smaller microspores develop into a male gametophyte. In heterosporous plants, two different germ cells, namely megaspores and microspores, are produced. The presence of male and female parts on the same sporophyte makes the plant monoecious, while plants with male and female parts on different sporophytes are dioecious. Heterosporous plants typically exhibit cross-fertilization. Sporophytes are the dominant generation in heterosporous plants.

In summary:

  • Homospory produces identical spores.
  • Heterospory produces two different types of spores.
  • Homospory is observed in Bryophytes and ferns.
  • Heterospory is observed in Pteridophytes and seed plants.
  • In homosporous plants, a single type of germ cell is produced.
  • In heterosporous plants, two different germ cells are produced.
  • Homosporous plants commonly undergo self-fertilization.
  • Heterosporous plants typically exhibit cross-fertilization.

Comparative Table: Homospory vs Heterospory

Here is a table comparing the differences between homospory and heterospory:

Feature Homospory Heterospory
Type of Spores Produces only one type of spores Produces two different types of spores
Size of Spores All spores are the same size Spores are of two different sizes
Sex Differentiation Sex is differentiated only at the gametophytic stage Sex differentiation occurs even at the sporophytic phases
Gametophyte Depends on soil and environmental conditions for nutrition Gametophyte is attached to the sporophyte
Gametophyte Independent of external climatic conditions Gametophyte is dependent on external climatic conditions
Megaspores Many small megaspores One large megaspore
Seed Habit Does not result in the seed habit Results in the formation of seed habit
Nutrition Source Embryo gets nutrition from the independent green prothallus The new embryo gets sufficient nutrients from the sporophyte

Homospory is observed in Bryophytes and ferns, while heterospory is observed in Pteridophytes and seed plants. In homosporous plants, gametophytes are the dominant generation, whereas in heterosporous plants, sporophytes are the dominant generation.