Need for Water
Like all living things, plants need water to survive. Plants use water to maintain their shape, obtain energy through photosynthesis, collect dissolved nutrients from the soil, transfer small molecules throughout the plant, and cool off leaves in hot weather through evaporation. Because they need so much water, plants must have an efficient system to collect it.
Plants obtain water through the soil. The roots are the transportation system to get the water from the soil and to the parts of the plant where it is needed. The roots branch off into smaller and smaller roots, and the smallest roots are called root hairs. These root hairs absorb the water into the root system, which then transports the water to the rest of the plant.
Osmosis is the process by which the water is absorbed into the root system and also how it moves through the plant. If the roots are the transportation system, then osmosis is the transport. In simpler terms, the roots are like a highway,and osmosis is like a truck that carries the water over the highway. Plant cells have semi-permeable membranes which allow water through, but the water will only move through when the pressure on the other side of the membrane is less than the first side. The equalizing of this pressure is called osmosis.