Architectural analysis of plant root systems

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Abstract
Summary: The techniques of architectural analysis were applied to the root systems of plants growing under field conditions, to determine their validity in this situation and to measure the extent and causes of plasticity and of interspecific differences in root architecture in co‐existing species. In a three‐year study of two species (Trifolium repensL. andPlantago lanceolataL.) on eleven different soils, large differences were found between species, soils and years; much of the variation in the root architecture ofT. repenscould be explained in terms of soil moisture concentration. On two woodland sites, the root architecture of five species was followed over a 15–month period, and at one a manipulative experiment involving irrigation and nitrogen and phosphorus addition was set up. There were large differences between species in root architecture and seasonal changes in some aspects (topology and exterior link length), which probably represent developmental patterns. Irrigation induced topological changes in one species (Galium aparineL.) which were consistent with the results of the three‐year study, but not apparently with an earlier model. In the case ofMercurialis perennisL., however, both irrigation and N and P addition brought about the predicted changes in root architecture, namely shorter interior links and lower topological index, though N had the opposite effect on exterior links. Interior link length differed widely between species, but showed little temporal variation, suggesting that it may be a valuable character for further studies. These results illustrate the validity and potential of architectural analysis for the study of root systems extracted from field soils.