Consider how lettuce or spinach placed in water becomes firm and crisp. use what you have learned about cell membranes to explain this observation.

The cell membranes of the plants and other organisms are semi - permeable. This means that they allow other substances to get in and out while ban others. In this item, placing lettuce or spinach in water, allow water to get into the cell through the process called pinocytosis or "cell drinking". This process makes the leaves crispy. 

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.