Roots serve as the most fundamental organ to health of most plants. The root or radicle is the first plant part to appear from a seed. Roots act to anchor the plant and absorb water and nutrients for photosynthesis; these are called true roots. True roots are usually divided into two forms: fibrous and tap. Some plants have a mass of string-like, fibrous roots (e.g. grasses); others have a large, main taproot with smaller side roots (e.g. oaks, carrots). Sometimes roots “sprout” from the side of a stem, like in a vine; these are called adventitious roots. A plant with an underground stem will have adventitious roots.
Functions of roots
■ Absorption: Absorption of water and nutrients are one of the primary functions of roots. Roots absorb water through a passive, physical process. Water being released from leaves is linked to other water molecules in the plant like a chain. As the water is pulled out of the leaf into the atmosphere, the chain pulls new water molecules up through the stem and into the roots.
■ Anchorage: Roots also act to anchor the plant in the soil or on rock. Thus, roots act as the major supportive organ for all other organs.
■ Conduit: Roots (like stems and leaves) serve as the initial pipeline for water that is needed in the plant. Sugars (energy) are also transported down to the actively growing portions of the root.
■ Storage: Most roots store some quantity of sugars, water, or toxic chemicals (like leaves and stems), but some roots are quite large and fleshy storage organs (e.g. carrots).
■ Respiration: Some swamp or flooded plants produce roots or “knees” that grow up and out of the water, allowing the roots to exchange gases in this oxygen-free environment (e.g. bald cypress, mangrove)
■ Support: Specialized adventitious roots called prop, stilt, and buttress roots can be found on tropical trees that experience frequently flooding (e.g. mangrove).
■ Photosynthesis: In rare cases, plants have green, aerial roots that photosynthesize (e.g. orchids).