Consider statements about vitamins: 1. Vitamin A deficiency causes night blindness. 2. Vitamin B1 deficiency causes beriberi. 3. Vitamin C is essential for blood clotting. Which are correct? MCQ with Answer and Explanation

Explanation:
Nitrogen fixation, the conversion of atmospheric N2 to ammonia, is performed by certain bacteria and cyanobacteria (blue-green algae). Denitrification is the process where denitrifying bacteria convert nitrates in the soil back into nitrogen gas (N2), returning it to the atmosphere. Ammonification is the decomposition of organic nitrogen into ammonia by microbes; nitrification converts ammonia to nitrate. Thus, statements 1 and 2 are correct.

Explanation:
Stem bears leaves and reproductive structures. It is positively phototropic (grows towards light). Leaves are the main photosynthetic organs. Roots grow downward.

Explanation:
In aquatic plants like Hydrilla, the rate of photosynthesis can be estimated by counting the number of oxygen bubbles released per minute under light. Manometry measures pressure changes, respirometry respiration, spectrophotometry light absorbance.