pH in pictures! Spatio-temporal monitoring of pH in the rhizosphere using planar optodes

Abstract

The soil is a complex, heterogeneous and dynamic environment, where various and essential biogeochemical processes take place for the functioning of plants and their ecosystems. The study of soil-roots interactions in the different soil horizons is crucial to understand the dynamics of nutriments and carbon as well as the role played by micro-organisms associated to the rhizosphere. These interactions take into account processes at tiny scales and temporal dynamics that cannot be reached easily in situ. We present here a method of measure of the soil pH in situ, a key parameter of the soil-roots-micro-organisms interactions through an imaging technique called planar optodes. These optical and chemical sensors allow to follow over time without invasion the soil pH and its spatialization at millimeter or infra scale. We present an application of this new tool to follow in situ rhizophere pH of cereals and legumes.