Chemotactic response of (a) A. chroococcum and (b) P. fluorescens towards VAM and non-VAM roots when kept at different distances from tomato seedlings at different soil matric potentials. Mean values±S.E.M. from five replicates are indicated. The assay time was 60 min. Ac: A. chroococcum, Pf: P. fluorescens.