DO DETACHED ROOT-CAP CELLS INFLUENCE BACTERIA ASSOCIATED WITH MAIZE ROOTS

A model rhizosphere has been used which consisted of detached root-cap cells of maize in their surrounding root-cap mucilage on the surface of Noble agar. These cells were co-cultured for periods up to 32 d with eight different bacterial isolates from soil-grown roots and surrounding soil and two laboratory cultures. Cap cells were unaffected by the bacteria. There were five different type-specific responses of the bacteria in proximity to the cap cells. There were, strong growth inhibitory (Rhizobium sp. and Escherichia coli), strong stimulation (Pseudomonas fluorescens, laboratory strain), mixed weak inhibition or stimulation (Pseudomonas fluorescens, field isolate), early inhibition followed by strong stimulation then spore formation (Bacillus spp.), no effect (Streptomyces sp. and Cytophaga sp.). It is concluded that detached root-caps are actively involved in the establishment of characteristic rhizosphere bacterial microflora.