INFECTIVITY OF RHIZOBIUM-TRIFOLII INTO A MINUTE EXCISED ROOT OF WHITE CLOVER

The degree of root cell mass necessary for normal infection thread production and nodule formation by rhizobia was studied. Excised white clover root tissues of 5.0, 2.5 and 1.0 mm in length, obtained from two days seedlings, were cultured in the dark with Rhizobium trifolii 4S. A culture period of seven days was separated into an initial period of three days and a later period of four days. Culture media of liquid on agar (0.8%) were used including Fåhraeus inorganic medium and an organic medium containing vitamins, sucrose, and an extrinsic substance isolated from R. trifolii 4S cells (ES-6000). When ES-6000 was added in culture medium for the initial period and root segments had an apical meristem, infection threads and nodules were most numerous. © 1979 Martinus Nijhoff Publishers.