11: Roots

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The root system of a plant serves two primary functions: water absorption and anchorage. Roots with a higher surface area will be better adapted to absorbing water because they have more area to interact with the soil environment. Increased interaction with the soil environment can also contribute to increased anchorage, but there are always trade-offs. If roots become too fine, they will be easily broken and lose the anchorage function. Additionally, finer roots can also lose more water if the soil environment becomes dry. Alternatively, roots with more volume are able to store more water, starches, or other materials belowground. The balancing of these trade-offs with localized environments has resulted in a great diversity of root types and morphologies.

11.1: Primary Growth
All plant roots begin in primary growth, which is a lengthening of plant organs. Primary growth involves the root apical meristem, primary meristems, and primary tissues.
11.2: Secondary Growth
In secondary growth, primary tissues and residual meristematic tissues produce secondary meristems, which then produce secondary tissues. Whereas primary tissues allow for vertical growth, secondary tissues allow for lateral growth.
11.3: Root Systems
Plants tend to have either a netted root system (typical of monocots) or a taproot system (typical of eudicots). Some plants can also produce roots from stem tissue (adventitious roots) or for a specialized function (e.g. prop roots and pneumatophores).