EVERYDAY SCIENCE

Detailed explanation-1: -Sexual reproduction (Auxospore formation) Gamete formation: In some spp of Pinnularia, two cells. from common parent or different parents envelope in a common mucilaginous sheath. The nuclei of both cells divide by meiosis to form four nuclei. Three nuclei disintegrate.

Detailed explanation-2: -Each diatom species constructs a uniquely structured cell wall called a frustule, consisting of valves and girdle bands (1, 2) composed of organic material and silica, which is often ornately and intricately shaped with fine features on the nanometer scale.

Detailed explanation-3: -The diatoms possess a diplontic life cycle consisting of a long period (up to several years) during which diploid cells divide mitotically and a brief period (a few days) during which sexual reproduction takes place. Gametes fuse to form a zygote, which inflates to generate an auxospore.

Detailed explanation-4: -A specialized spore called Auxospore is formed in both the groups. During cell division, those cells become reduced in size, are able to regain their normal size through the formation of auxospore, so it is a “restorative process” rather than multiplication.