Plant Roots in the Soil
Most plants absorb water through their roots. Because the roots are in the soil, the soil acts as the medium that delivers water to the roots of the plant. If the soil is comprised of materials that allow it to hold water, the roots will absorb more water. If the soil is comprised of materials that drain water away quickly, the roots will absorb less water. The nutrients in the soil are also absorbed into the roots as the water absorbs.
Roots Absorb Water
Roots have tiny rootlet hairs that extend out from the roots and anchor into the soil. These root hairs are the way the plant absorbs water---not the large roots that make up the root ball of a plant. The large roots are mainly for anchoring the plant in the ground and giving it a solid foundation.
The root hairs absorb water and take it to the vascular rays, which are pathways to the center of the root. The center of the root is the stele. The veins of the root (the xylem) are in the stele. They are responsible for transporting the water and nutrients throughout the entire plant. Outside of the stele lies the cortex. The cortex is responsible for absorbing nutrients received from the soil.
Water Moves Through the Plant
As water moves up through the plant system through the stems and to the leaves, eventually the leaves release water through pores on the bottom of the leaves. This evaporation into the air is transpiration and a plant is continually doing this as it lives.
Epiphytes are plants that have a special root structure that allows them to attach themselves to surfaces that are not under the soil. Because of this, these plants get moisture from the atmosphere and not through their root systems.
Examples of epiphyte plants include mosses, some ferns, bromeliads and some orchids. Because these plants require high humidity levels for adequate moisture, they are native to tropical regions of the world. When water is scarce, these plants shrivel and become dry. When water returns, the plants revitalize and swell to receive the water from the air.