Fine hairs populate the surface of the plant's roots. These hairs absorb water and the nutrients therein through tiny pores, which span each hair's surface.
Within the roots and stem of the plant are vascular tissues called xylem. Xylem tissues move the nutrient-enriched water up through the entire plant's body and distribute water to each cell residing in the plant's tissue.
The pressure that distributes water in the plant is maintained by the soil continuously replenishing its water cache. Pores in the soil allow water to flow from a greater volume of water in the soil to a lesser volume of water in the soil. As the plant's roots take up water from the soil, the absence of water allows for new water to refill the soil. Additionally, the plant's roots branch outward into newer soil in search of water as the plant grows.
Water Pressure
A plant's roots contain cells that are highly compacted with minerals. The surrounding soil contains a less dense concentration of minerals than the roots. The water volume differential between the rooted soil and the surrounding soil applies pressure on the roots of the plant.
Water pressure moves into the roots through the fine hairs on the root's surface, up through the xylem and into the plant cells. As water moves through the xylem, it takes on the form of a sticky substance referred to as sap. Sap contains all the mineral nutrients of the soil mixed with the water acquired through the plant's roots.
Transpiration
The final stage in the water cycle of a plant is called transpiration. Sap is distributed through the plant's stem, up through the branches and into the leaves by the continuous flow of water pressure. The nutrients in the sap spread out to the cells in the leaves through tiny veins. It is at the leaf of a plant where water is returned back into the environment. The plant's leaves release nearly all of their water (90 percent or more) into the air in the form of mist. The mist on the surface of the leaves is dried up by the sun.
Soil and Climate
As a rule of thumb, it generally takes longer for water to reach the roots of a plant in heavy soils, such as clay. Sand or soils containing high concentration of sand will typically allow an inch of water to descend a dozen inches into the ground. For deep-rooted plants in tough or hard soil, apply a few inches of water over the surface area of the garden. In colder climates, use less water.
