rodhår

Rodhår, also known as root hairs, are tubular extensions of epidermal cells on plant roots that markedly increase the surface area available for water and nutrient uptake. They typically arise in the maturation zone of the root and are most commonly found in many vascular plants, especially in dicots. Rodhår are usually single, slender cells that can range from tens of micrometres to a few millimetres in length, depending on species and environmental conditions.

Growth occurs by tip growth, driven by turgor pressure and targeted vesicle delivery, and depends on the cytoskeleton and cell wall remodeling. The initiation and differentiation of epidermal cells into hair-forming (trichoblast) cells versus non-hair cells are influenced by positional cues, hormonal signals such as auxin and ethylene, and a conserved set of regulatory genes, including RHD6 and members of the RSL family, which promote hair initiation and elongation.

Functionally, rodhår increase the absorptive capacity of roots by expanding contact with soil water and minerals, with particular importance for phosphate and nitrate uptake. They may also secrete mucilage to improve soil lubrication and influence the rhizosphere chemistry, aiding nutrient solubility and transport. The presence and characteristics of rodhår can affect plant growth and nutrient efficiency, especially in nutrient-poor soils; their length and density can respond to nutrient status, moisture, and soil texture.

Environmental factors strongly influence rodhår development. Adequate moisture supports growth, while drought can reduce length or density. Phosphorus deficiency often stimulates longer or more abundant root hairs. Rodhår are a common feature of the roots of many angiosperms, though patterning and prevalence can vary among species.

Rodhår is the Danish and Norwegian term for this structure; in English they are called root hairs. See also: root epidermis, tip growth, trichoblast.