Question

Osmotic potential and pressure potential of three cells a,b,c are located in different parts of an actively transpiring plant is

Cell	O.P(MPa)	P.P(MPa)
a	-0.87	0.44
b	-0.92	0.34
c	-0.68	0.27

Which ones are root hairs , root corticals and mesophyll cells respectively?
A) a,b,c
B) a,c,b
C) c,a,b
D) b,c,a

Answer 1

Hint: Osmotic pressure can be considered as the pressure that would be necessary to prevent osmosis from diffusing water through a barrier.The pressure potential is dependent on mechanical pressure and is an essential component of the total potential for water within plant cells.

Complete answer:
Since the intracellular environment is different from the extracellular environment, osmotic pressure is a very significant factor in biology. It can allow water to migrate into or into our cells if the extracellular environment changes.

This idea has been taken advantage of by certain species, such as plants that use osmotic pressure to transfer water. But when there is too much or too little water in the extracellular environment relative to the inside of the cell, it may also endanger the health of the cells and organisms.

The potential for pressure rises as water enters a cell. It increases the total amount of water present within the cell as water moves through the cell wall and cell membrane, which exerts an external pressure that is opposed by the cell wall's structural rigidity. By producing this strain, the turgor can be maintained by the plant, enabling the plant to preserve its rigidity. Plants will lose structure and wilt without Turgor.

Typically, the pressure potential is positive in a plant cell. In plasmolyzed cells, the capacity for pressure is almost zero. When water is drawn into an open system such as a plant xylem vessel, negative pressure potential occurs. An significant adaptation of xylem is to withstand negative pressure potential (often referred to as tension). Using the pressure bomb, this stress can be calculated empirically.

The potential of water is determined by the sum of the osmotic potential and the potential of strain. More water travels to a lower water potential from a higher water potential. For three cells A, B and C, the measured water potential values are -0.43, -0.58 and -0.41. Water would then move from C to A to B. This suggests that root hair must be cell C, root cortex must be A and leaf mesophyll must be B.

Thus the correct answer is option (C) i.e, “c,a,b”

Note: Atmospheric water potential, on the other hand, is even more negative, with an average dry air value of -100 MPa, although this value depends on temperature and humidity. In order to produce a passive flow of water from the soil to the roots up the stem, to the leaves and then into the atmosphere, the root water potential must be more negative than the soil, and the stem water potential must be an intermediate value lower than the roots but higher than the leaf water potential.