SEM observations in the back-scattered mode of the soil–root zone of Brassica napus (cv. Rafal) plants grown at a range of soil pH values

Abstract

In the study of the root–soil interface, scanning electron microscopy (SEM) in secondary emission mode and transmission electron microscopy are commonly used techniques. As these methods have some limitations, there is a need to explore other techniques which may be suitable for the observation of the root–soil zone. One of the most promising methods is the application of SEM in the back-scattered electron (BSE) emission mode. The root zone of plants of winter oilseed rape ( Brassica napus cv. Rafal) grown at a range of soil pH and soil phosphorus (P) concentrations was examined by SEM in BSE mode. The method for the preparation of transverse sections of the root–soil contact zone is presented. The BSE scanning images of the root–soil interface obtained allowed investigation of the flow paths of plant nutrients from the soil towards roots and their distribution in the roots. Concentration of aluminium in the cell walls of immature roots and at the soil–root interface was observed in the most acid soils. Potassium, calcium and phosphorus were found in differentiated roots associated with the external tissues of the central cylinder. The intimate contact of root surface with soil mineral particles could also be observed.