PROTOZOA AND BACTERIA IN THE RHIZOSPHERE OF SINAPIS ALBA L., TRIFOLIUM REPENS L., AND LOLIUM PERENNE L.

Abstract

The largest differences between rhizosphere and unplanted soil populations of protozoa and bacteria were found during the early stages of flowering of both an annual (Sinapis alba L.) and a perennial plant (Trifolium repens L.). From an early stage in plant growth, the populations of flagellates and amoebae were significantly higher in the rhizosphere soil than in unplanted soil. The generic composition of the rhizosphere protozoan population was not different from that of unplanted soil, although the abundance of particular genera varied with the plant species and age. Ciliates were only found in low numbers in both rhizosphere and unplanted soils.Desiccation of soil planted with Lolium perenne L. initially caused a reduction in both protozoan and bacterial rhizosphere numbers. Subsequently both populations recovered with the flagellates and amoebae again more abundant in the rhizosphere than in unplanted soil. Desiccation did not greatly affect the protozoa in unplanted soil and encysted populations of amoebae and flagellates occurred when the soil was moist or dry.