A high concentration of auxin in the root will stimulate growth. Auxin is a plant hormone that is responsible for promoting and regulating plant growth and development. When the concentration of auxin is high in the root, it causes the cells in the root to elongate, leading to the stimulation of growth. This process is important for the development and establishment of the root system, which is essential for water and nutrient uptake by the plant. Therefore, a high concentration of auxin in the root will lead to the stimulation of growth, rather than inhibition or reduction of water absorption.