Minirhizotron, a new technique for plant root system research: its invention, development and application.

Root system is the dynamic interface of plant and soil, and of great significance to both of them. However, owing to the fact that it hides deep in the soil, the research on the root system is quite inconvenient, and lags behind that on plant aboveground part extensively and intensively. With the recognition of the significance of root in ecosystem and globe carbon balance, root research has become one of the hotspots internationally. With the invention and development of minirhizotron technique, root research technique has made a great progress. Minirhizotron has been a milestone in the development of root research techniques. Minirhizotron system is composed of transparent observation tube, viewing equipment and recording equipment. Mirror, scope and camera have been used as the viewing equipment successively, while recording equipment experiences the history of hand-drawing, traditional photo or tape and digital camera picture. With the development of the root image analysis systems, this technique has been greatly improved. It allows us to observe nondestructively the initiation, elongation and death of the root at an interval, obtain the information on root length, rooting density and depth, lateral root spread, branching characteristic, mycorhiza characteristic, fine root dynamics, root system lifecycle and root catabolism, etc., and understand the responses of root system to various stress. This technique would certainly find a wider use in agricultural, forestry and environmental sciences.