INFLUENCE OF ROOT TEMPERATURE ON THE EARLY GROWTH AND SYMBIOTIC NITROGEN FIXATION OF NODULATED LOTUS CORNICULATUS PLANTS

Abstract

Three birdsfoot trefoil (Lotus corniculatus L.) cultivars, inoculated with one of six Lotus rhizobia strains or dependent on ammonium nitrate, were grown in diSPo growth pouches under controlled environmental conditions at five root temperatures (9–30 C) for 35 days after nodule formation. When the plants were dependent on symbiotic nitrogen fixation, the highest dry weights and nitrogen yields per plant were obtained at 18 or 24 C depending on symbiotic combination. At 9 and 12 C, nitrogen fixation was depressed and the growth was poor. The dry weights of plants at 9 C were 19 to 45% of those at 24 C. At 30 C the growth and nitrogen fixation were generally depressed. At all root temperatures the growth of plants dependent on symbiotic nitrogen fixation was inferior to that of plants receiving combined nitrogen (NH4NO3). Significant interactions indicate that the nitrogen fixing ability of cultivars was dependent on both root temperature and the strain of Lotus rhizobia.