How do diffusion and osmosis process help plant leaves remain firm?

Answer 1

As stated by another person, it doesn't only have to deal w/ the pores-- but this is to clarify the pore statement: The stomata is a pore on the under surface of the leaf-- this has gaurd cells that open and close due to turger pressure--- this will allow oxygen & water out of the cell and carbon dioxide into the cells of the leaf so that photosynthesis can occur. When the stomata closes, water will come up the shoot to the leaves, but the diffusion of the water into the cells of the leaves is what keeps them "firm".

Now, if the plant cells in the leaves don't have enough water, water will be transported up the shoot and diffuse into the cells that can still hold water-- when these cells are full, the leaves will stand up-- if they become too full, the cells will burst, causing it to die. These cells want to be at equilibrium- so the area around the cell is the same as the cell itself (same amount of water inside as outside-- but the amount of solute found will vary depending on the time of day)... if the cell has too much water, it will allow some water out via it's selectivity permeable membrain and vice versa...

Answer 2

By keeping the vacuoles full of water. If the plant gets dehydrated they droop.