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There is evidence in the literature that drought avoidance/tolerance in many annual crop plants is associated with root system characteristics. However, investigations on the morphological traits associated with drought resistance of tree crops is very limited. Identification of such traits would be useful in screening genotypes for drought tolerance. To assess the impact of environmental conditions on plant behaviour requires a carefully defined test environment, a procedure for monitoring changes in the environment and the testing of the test environment for reliability. The filter paper procedure was modified, calibrated and adopted to monitor soil water potential in experimental pots. A multi-compartmental pot system was developed to a create discontinuous soil water distribution. Wax and coarse sand were used to create spatially variable soil water potentials in adjacent pot compartments and the effects were assessed using broad bean as the test plant. Wax affected root morphology but sand did not. The vertically segmented pot set-up proved to be effective for the assessment of genotypic differences in rooting patterns in response to heterogeneously distributed soil water. Genotypic variations in morphology and growth patterns of whole root systems in coconuts were studied under favourable soil moisture conditions. The root systems of coconut cultivars varied in size, growth, patterns and in individual characteristics. Differences were apparently related to the drought tolerance of cultivars. Differences were associated with important differences in patterns of dry matter partition. Three coconut cultivars were evaluated in relations to root system responses to dehydration in the surface soil.