Question

a When in solution NaCl will dissociate into Na⁺ and Cl^- ions? What concentration would you need to add a NaCl solution at to observe the same rates of plasmolysis as with a 0.8M sucrose solution?

b If you placed your onion cells in a slightly acidic environment would you expect there to be any change in the pH of the cytosol due to the open water channels? Why?

c Why are changes in turgor pressure important with respect to gas exchange in the leafs of plants?

Answer 1

a. Water molecules are polar in nature. The oxygen atom is negative and hydrogen atoms are positive. When we mix NaCl to water, the Na⁺ ions are surrounded by the water by facing the oxygen atoms towards the Na⁺ ion. The Cl^- atoms are surrounded by the water molecules by facing the the hydrogen atoms towards the Cl^- ion. Thus Na⁺ and Cl^- ions are dissociated from NaCl.

The morality of any solution is depends upon the presence of solute particles in the solution. 0.4 M NaCl solution produces the same number of particles as the 0.8 M sucrose solution as a NaCl molecule dissociates into two particles (Na⁺ and Cl^-​​​​​​).

b. Yes, there may be slight difference in the pH of cytosol because H⁺ ions from external acidic environment may diffuse to the cytosol.

c. If the turgid pressure of the guard cells are increased then the stomata opens. When stomata opens the exchange of gases as well as water transpiration can take place.