Question

A spore of Spirogyra sp. after resting period is

• A. Haploid
• B. Diploid
• C. Aplanospore
• D. Zygospore

Answer 1

The correct option is A Haploid

Zygospore represents the only diploid stage in the lifecycle of spirogyra and it is yellowish brown ellipsoidal structure having diploid nucleus and covered by three layered wall : the outer exospore / exine, the middle mesospore / mesine, the innermost endospore / intine.

The zygospore due to the thick wall can withstand long period of dry and dessication. They are liberated after the destruction of mother cell or mother filament and they remain at the bottom of water body. With the coming of rainy season, the zygospores start to germinate. Before germination, the diploid nucleus divides meiotically and form four haploid nuclei. Out of which three degenerate and one remains at functional nucleus.

At the time of germination the exospore and mesospore rupture and the endospore along with functional nucleus comes out as single cell germinating tube, which immediately divides into two celled structure. The basal cell forms the rhizoidal cell and the upper cell by repeated division and growth develops into new spirogyra filament.