A METHOD TO STUDY RHIZOSPHERE PROCESSES IN THIN SOIL LAYERS OF DIFFERENT PROXIMITY TO ROOTS

Under regulated climatic and nutritional conditions plants were pre-grown in vermiculite-filled PVC tubes closed with fine-meshed nylon cloth at the bottom. Nutrient and water supply was ensured via two wicks. When a root mat had developed the nylon cloth was removed. The plants were then transplanted to a soil column having a 53-mu-m-mesh nylon screen at 1-cm depth at which a new root mat developed and created a zone of depletion and/or accumulation of nutrients in the adjacent test soil column below the screen. At the termination of the experiment the test soil column was separated from the root mat, quickly frozen with liquid nitrogen and sliced into thin layers (0.2 mm) with a refrigerated microtome for analysis. Results from a study of phosphorus depletion near the root mat of rape plants showed good reproducibility (Coefficient of variance 3.5%). The technique enabled a constant pH to be maintained in the rhizosphere. The method opens up new possibilities for the detailed study of rhizosphere processes of plants at advanced stages of development under controlled nutrition.