THE ROOT-SYSTEM ARCHITECTURE AND DEVELOPMENT OF SENECIO-VULGARIS IN ELEVATED CO2 AND DROUGHT

1. The impact of elevated CO2 and drought on the architecture and development of root systems of Senecio vulgaris was examined and implications for water and nutrient uptake discussed. Plants were grown in miniature rhizotrons to non-destructively monitor the development of roots in situ at both an elevated (700-mu-mol mol-1) and ambient (350-mu-mol mol-1) atmospheric CO2 concentration and a high or a low supply of water. 2. CO2 and water had a significant impact on the way that S. vulgaris root systems filled the soil matrix. Elevated CO2 resulted in more branched, longer root systems that foraged through larger volumes of soil. Under elevated CO2 and a low water supply, root systems had branching and foraging patterns and root length similar to those grown under ambient CO2 with a high water supply. 3. Overall, water had a more pronounced impact on the growth rate of S. vulgaris roots than did CO2. The density of rooting remained unchanged across all treatments. Thus, under elevated CO2 the intensity of foraging S. vulgaris root systems might be unchanged while the extent of foraging by these root systems, as indicated by the horizontal spread of roots, may be increased.