Give an account of the asexual reproduction by spores in algae.

Algae and their spores exhibit enormous diversity and they vary greatly in their level of specialisation. Asexual reproduction by spores and their types are described below:

(a) By Zoospores These are mobile flagellated spores. In which protoplasm of each vegetative cell undergoes repeated longitudinal division either into 2 or 4 rarely 8 or 16 daughter protoplast. The parent cell loses its flagella, before the onset of division.

After the last series of divisions, each daughter protoplast secretes a cell wall and neuromotor apparatus that develops two flagella, eyespots and contractile vacuoles.

Thus, each of the daughter cells formed resembles the parent cell in all aspects except the small size.

Formation of zoospores is very common under favourable conditions.

(b) By Aplanospores These are the non-motile spores. They are asexually formed with in a cell, in this protoplast withdraws itself from the parent wall, rounds up and develops into aplanospores which may either germinate directly or may divide to produce zoospores.

(c) By Hypnospores- In this, the protoplasm withdraws from the cell wall, rounds up and develop a thick wall under unfavourable condition. These resting spores are called hypnospores. They are red in colour due to the presence of hematochrome. e.g., Vaucheria, Ulothrix.

(d) Akinetes- These are special vegetative thick-walled cells present in the filaments which remain in a dormant state and return to germination under favourable conditions and can also withstand unfavourable conditions such as Spirogyra.

(e) Statospores- These are the thick-walled spores produced in diatoms.

(f) Neutral Spores- In some algae, the protoplast, of vegetative cells directly functions as spores called as neutral spores (e.g., Ectocarpus)