explain the relationship of membrane semipermeability to plasmolysis?

Answer 1

If the membrane was not semipermeable and allowed movement of all molecules then the solutions separated by it would simply mix and there would be no osmosis.

Osmosis is based exactly on the fact that not all molecules can pass through the membrane and thus water has to move in order to try to equilibrate the solute concentrations.
Plasmolysis is a case of osmosis where the cells are exposed to a solution of higher solute concentration and water is leaving from the cell until it collapses.

You can check the link I sent you in the answer to your other question-it explains osmosis, tonicity, plasmolysis, deplasmolysis, etc.

Answer 2

man who cares. schools out for the summer. get outside or something.