Anatomy and Histology of Roots and Root-Soil Boundary

Growing roots undergo many anatomical and morphological changes, which influence their activity and nutrient uptake processes. Therefore, it is often necessary to obtain structural information on the inner (anatomy and histology) and outer (morphology) parts of roots. This chapter gives an overview of methods to obtain information on anatomical and histological as well as morphological (root hairs and mycorrhiza) properties of roots. The methods applied for the study of root anatomy do not, generally, differ from methods used for the study of plant stems and leaves. Methods can thus be found in general laboratory books and manuals (Johansen 1940; Sass 1961; Jensen 1962; Purvis et al. 1964; O’Brien and McCully 1981; Neergaard 1997). Before a root specimen and a thin section of root-soil boundary can be investigated under a microscope it has to pass along a chain of processes which include sampling, killing and fixing, embedding, sectioning, and staining. Details of these processes depend on whether light microscopy (LM), transmission electron microscopy (TEM), or scanning electron microscopy (SEM) is to be used. For LM and TEM, histochemical or immunological tests may be applied additionally if the purpose is to demonstrate the presence of certain compounds in cells or tissues. SEM deviates from the other two mentioned with the exception of initial fixation steps and will be treated in a separate section. Squash techniques for chromosome studies, most often carried out on root tips, are also dealt with separately. Information on the anatomy of roots can be sought in books on plant anatomy (Esau 1965, 1977; Guttenberg 1968; Mauseth 1988; Fahn 1990) and root physiology (Luxovâ and Ciamporovâ 1989).