Reproduction in Algae

Reproduction in algae is of three main kinds: vegetative, asexual and sexual.
i) Vegetative Reproduction: It occurs by fission, fragmentation, budding, propagation, hormogonia, protonema, tubers, akinetes, bulbils etc

• Akinetes: thick walled non-motile bodies filled with concentrated food, modified vegetative cell
• Hormogonia: segments of filaments

ii) Asexual Reproduction: It takes place by the formation of various types of sporangia. The spore escape from the parent plant, undergo germination and give rise to new plants. All kinds of spores, which the exception of zoospores, are non motile. The common types of asexual spores, found in algae, include zoospores, aplanospores, autospores, hypnospores, exospores, endospores, carpospores, monospores, tetraspores and paraspores.

• Zoospores: flagellated, asexual reproductive bodies often with an eyespot.
• Synzoospore: multinucleate, multi-flagellate zoospore or compound zoospore.
• Aplanospore: non-motile thin walled zoospore formed by cleavage of protoplast within a cell.
• Hypnospore: thick walled aplanospore.
• Autospores: thin walled spores formed by parent cell division.
• Tetraspore: 1n, thin walled, non-motile spores formed after reduction division in 2n tetrasprangia.

iii) Sexual Reproduction: It is also known as gametic reproduction, since it involves the fusion between haploid gametes to form a diploid zygote.
Based on the form, size and behaviour of the fusing gametes, three major kinds of sexual reproduction can be recognised among algae, namely isogamy, anisogamy or heterogamy and oogamy

• Isogamy : equal-sized, motile gametes
• Anisogamy  or heterogamy-: motile gametes , almost equal-sized
• Oogamy : small motile male gamete, large non-motile female gamete

Isogamy is the most primitive type , and oogamy is the most advanced type.