A mixture of plant secretions, bacteria, and soil particles that surrounds the tip of plant roots. It contains complex polysaccharides called mucilages which are secreted by the root cap and help to lubricate passage of the growing root tip through the soil. However, the root tip also releases proteins, which help to protect the root tip from infection, and amino acids and sugars, which influence microbial activity in the rhizosphere, thereby helping to mobilize soil nutrients for uptake by the root. See also rhizosphere.