Tag: plant water relation

DPD of cell A=5A=5 bars
DPD of cell B=5−5=0B=5−5=0 bars
DPD of cell C=10−4=6C=10−4=6 bars
DPD of cell D=8−3=5D=8−3=5 bars
As cell B has the lowest value of DPD, therefore water will move from cell B to cells A, C and D.

The phenomenon of breaking up of water into hydrogen and oxygen in the illuminated chloroplasts is called photolysis or photocatalytic splitting of water. It can be depicted as: $4H _{2} O \rightleftharpoons 4H^{+} + 4OH^{-}$
   $4OH^{-}\xrightarrow[Mn^{2} + ,Ca^{2} +, CI^{-}]{Oxygen \,\, evolving \,\, complex} 2H _{2}O + O _{2}\uparrow + 4e^- $

Water potential is the measure of the free energy of water which helps in the movement of water between any two systems. Water moves from the point where the water potential is greater to the point where the water potential is less. Addition of solutes decreases the water potential (becomes more negative). Temperature has no effect on water potential. The water potential of pure water is taken as zero. 

Water potential is generally most negative in mesophyll cell walls because water evaporates from the mesophyll cells into the air spaces in the leaf. If the air surrounding the leaf has less water vapor than the air in the intercellular spaces, water vapor will leave the leaf through stomata. Order of water to move through the plant from the soil to the air ( a process called transpiration).

• Water potential is the potential energy of water relative to pure water in a plant cell or tissue. This can be written as the sum of matrix potential (due to binding of water to cell and cytoplasm), the solute potential (due to concentration of dissolved solutes which by its effect on the entropy components reduces the water potential) and pressure potential (due to hydrostatic pressure, which by its effect on energy components increases the water potential).
  
• Ψw = Ψs + Ψp + Ψm
  
• So the correct answer is "All of these".
  

The liberation of $ O _{2}$ during photolysis of water involves the role of $ Mn^{2+},Ca^{2+}$ and $CI ^{-}$ ions.

Osmotic pressure of the cell sap of root hairs is usually higher than the osmotic pressure of the soil water. Therefore, the diffusion pressure deficit (DPD) and the suction pressure in the root hairs become higher and water form the cell wall enters into then through the plasma membrane by osmotic diffusion.