ABSTRACT
The morphology of a plant root system is a function of its genetics and the environment in which it grows (Smucker, 1993; Aiken and Smucker, 1996). Morphology is also affected by interaction with soil microorganisms, e.g., arbuscular mycorrhizal fungi (Hooker et al., 1992). Both individual plant roots and whole root systems can and do show substantial variation within the potential range of their characteristics. Soil physical factors, particularly temperature, aeration, water potential, and mechanical impedance, are frequently the cause of limits to the expression of genetic potential. The morphology of the root system can thus be regarded as representing the integrated effects of three factors. This chapter first reviews those root properties that are most likely to be influenced by soil physical conditions and then describes methods that can be used in the field or laboratory to describe particular attributes of root systems. It illustrates some of the uses to which particular methods have been put and some of the limitations of their use. Bohm (1979) has given a more complete description of methods for measuring roots, and Atkinson (1981) has reviewed those methods relevant to tree crops. The impact of soil biological and chemical factors, and of the growth of the aerial parts of the plant, on root growth have been reviewed in general terms by Russell (1977).
