Question

The Osmotic theory of active water absorption was first given by
A. Kramer (1941)
B. Eaton (1948)
C. Atkins ( 1916)
D. Priestley

Answer 1

Hint: Active transport is the kind of transport in which substance moves against concentration gradient with the use of energy generally in the form of ATP.

Complete Answer:
- Active osmotic water absorption theory was first given by Akins and later it is given by Priestly. This theory explains the absorption of water by the roots from the soil.
- In these roots cells act as an osmotic pressure through which water moves up the soil with the help of xylem along with increasing DPD (DPD is diffusion pressure deficit which is the suction pressure causing water to be absorbed). If the solute concentration is high then water enters the cell with the help of endosmosis.
- To ensure endosmosis cells have to keep the solute concentration high for this purpose, cells absorb nutrients and minerals actively. This makes root cells more concentrated than the soil water. Thus water enters the root cells with the help of osmosis.
- Osmosis can take place until the concentration on both sides become equal. Thus the cell has to always keep the solute concentration high in order to keep the osmotic pressure difference between root cell and water. This will ensure the continuous absorption of water.

Additional information:
 There is another theory of water absorption called Non- osmotic water absorption, This theory was given by Thimann and Kramer. According to this theory water can be sometimes absorbed actively . This theory has very little evidence to prove.

Note: In osmotic theory of water absorption water is not absorbed actively but the energy is required to maintain the concentration difference between root cell and the soil water. Thus water absorption is indirectly an active process.