A novel method for characterisation and quantification of plant root exudates

A microcosm unit is described which readily allows manipulation of experimental conditions to enable the subsequent impact on root exudation release to be monitored with time. Festuca ovina and Plantago lanceolata seedlings were grown in this microcosm unit over a 34 day experimental period under conditions of high (3.75 mol m(-3) N) or low (1.25 mol m(-3) N) nitrate-nitrogen treatment. At the end of the experimental period the seedlings in the microcosms were labelled with [C-14]-CO2 and the fate of the label within the plant and its release by the roots monitored. Total organic carbon (TOC) content of the collected exudate material was measured throughout the experimental period as well as during the C-14-chase period and comparison of plant C budgets using these two measurements is discussed. Nitrogen treatment as found to have a greater effect on exudate release by F. ovina than by FI lanceolata seedlings as indicated by both the total organic carbon and C-14 results. The use and applications of the microcosm unit are discussed.