Question

the uptake of useable nitrogen forms by plants is called
assimilation.
respiration.
transpiration.
nitrogen fixation.
rewatch submit

Explanation:

• Assimilation: In the nitrogen cycle, plants take up nitrate ions ($NO_3^-$) or ammonium ions ($NH_4^+$) from the soil. This process of incorporating these usable nitrogen - containing compounds into plant biomass (such as amino acids, proteins, etc.) is called assimilation.
• Respiration: Respiration is a metabolic process in which cells break down organic molecules (such as glucose) to release energy in the form of ATP. It is not related to nitrogen uptake. The general equation for aerobic respiration is \(C_6H_{12}O_6+6O_2

ightarrow6CO_2 + 6H_2O+\text{Energy}\).

• Transpiration: Transpiration is the loss of water vapor from plant leaves (mainly through stomata). It helps in the upward movement of water in plants and cooling of the plant. It has no connection with nitrogen uptake.
• Nitrogen fixation: Nitrogen fixation is the process of converting atmospheric nitrogen (\(N_2\)) into ammonia (\(NH_3\)) by nitrogen - fixing bacteria (such as Rhizobium in root nodules of legumes). This is the first step in making atmospheric nitrogen available for plants, but it is not the uptake of usable nitrogen forms by plants.

Answer:

assimilation.