Passive mineral absorption : It is the absorption which occurs without expenditure of energy. It occurs by following methods :
(A) Diffusion (B) Mass flow
(A) Diffusion : It is the movement of minerals down the concentration gradient .
Types of Diffusion : It is of Two types as :
(a) Passive Diffusion : It occurs either by dissolving of minerals in matrix cell membrane or through pores. It is a physical process which needs no energy. Water, 02, C02, etc. diffuse by passive diffusion. Sodium in Nitella is absorbed by passive diffusion.
(b) Facilitated diffusion : It occurs by special protein molecules.
(B) Mass flow : Large amount of water is absorbed daily by the plant. Along with the water minerals from soil are absorbed into roots. More the rate of transpiration, more would be water absorption and thus more minerals pass into the roots and then ascend upwards into stem.
