Roots do far more than drink from the dark soil
In vascular plants, roots anchor the body and pull water plus minerals upward so shoots can climb faster and taller. Most hide below ground, yet the same organs also store food, mint hormones, and, in mangroves, snorkel air through specialized pneumatophores when soil oxygen fails.
A root's first two jobs are holding the plant in place against wind and flowing water and soaking up water and dissolved minerals. Absorption happens through the outer skin cells and fine root hairs, and the xylem then carries the haul up to the shoot. How deep and wide a root system spreads decides which soil layers it can tap. Many roots also stockpile carbohydrates and water, as carrots and sweet potatoes do, and they manufacture hormones such as cytokinin, which tells the shoot how fast to grow depending on nutrient supply.
Botanists sort root systems into two broad types. A taproot, like the carrot's or dandelion's, is one dominant downward root that grows from the seedling's radicle and sprouts side branches; it suits deep anchorage and storage. A fibrous system, typical of grasses, wheat and rice, is a dense mat of similar-sized roots near the surface, often sprouting from the stem base, that binds soil and grabs surface nutrients quickly. Specialists abound: maize braces its stalk with prop roots, banyan aerial roots can thicken into extra trunks, and mangrove pneumatophores let roots breathe where waterlogged mud lacks oxygen.
Growth starts at the tip. A cap protects the dividing cells of the apical meristem, shedding slimy cells that lubricate the push through soil; behind it cells elongate, then root hairs form. Unusually among plant organs, roots arise internally, from an inner layer such as the pericycle, whereas branches and leaves develop from the outer cortex. In woody plants the vascular cambium adds new xylem every year, thickening the root, while cork cambium builds a protective bark whose suberin blocks water loss and pathogens.
Roots respond constantly to their surroundings. Gravity steers them downward through auxin signalling, they veer away from dry or poor soil, and research suggests they can tell their own roots from a neighbour's. A tree's roots typically spread to about three times the width of its branches, and over time they can crack foundations, break water pipes and heave pavements. Most species also partner with fungi to form mycorrhizae that boost nutrient uptake.
Source: Root
