Which of the following elements is immobile?

Solution (By Examveda Team)

Calcium is an immobile element among the given options.
The calcium ions do not move by mass flow but by a series of exchange reactions along negatively charged sites on the walls of the xylem vessels. Movement can be promoted by the presence of divalent cations and by the chelation of the calcium ion. There is considerable lateral leakage of calcium from the xylem.