ABSTRACT
To fully understand the physiological activity of plant roots, one must understand the physical and chemical properties of the rhizosphere immediately near the root surface. For the root this is the direct environment for physiological interaction with the bulk soil. The attributes of the rhizosphere are determined not only by the soil, but also by the biochemical and physiological activity of the root. The properties of the rhizosphere can vary in size, shape, and composition, even from root to root on the same plant. Root biologists have sought to explore the rhizosphere and understand plant-mediated rhizosphere activities by utilizing microsensors to probe this environment. These sensors have included various types of ion-selective microelectrodes, as well as polarographic electrochemical oxygen sensors to determine the concentration of important molecules within the rhizosphere. Advanced microsensor techniques now make it possible to measure dynamic flux of these molecules in real time with a relatively high degree of spatial and temporal resolution. This technique has been referred to as the microelectrode ion flux estimation (MIFE) technique, the vibrating probe (VP), and more recently the self-referencing microsensor (SRM) technique. The use of such microsensors and microsensor techniques to study the plant root and rhizosphere processes is discussed in this chapter.
