(also rhizodermis), in plants, the primary surface layer of absorption tissue in the root. The epiblem develops near the growing point of the roots. Its cells form long thin growths, or root hairs (200–425 per sq mm), which significantly increase the absorption surface of the root and secure the plant in the soil by enveloping soil particles. Water and ions of mineral substances are absorbed by the mucoid pectic coating of the hairs. The root hairs elaborate acids that interact with substances in the substrate, and they accumulate ions in epiblem cells in quantities several times greater than the concentrations in the soil solution. The epiblem remains on the root tips for a short period of time; when it dies, it is replaced by secondary tissue—exodermis or periderm. The absorption function is transferred to a new section of the growing root, whose epiblem continues to ensure the inflow of water and other substances into the root of the plant.