NODULATION AND N-2-FIXATION BY CALLIANDRA-CALOTHYRSUS AND SESBANIA SESBAN GROWN AT DIFFERENT ROOT TEMPERATURES

Calliandra calothyrsus and Sesbania sesban were grown in controlled en vironment cabinets at range of controlled root and shoot temperatures. For C. calothyrsus nodulation was delayed until 13 days after inocula tion at 20 and 24 degrees C and no nodules formed at 40 degrees C. Nod ules formed most rapidly at 28 and 32 degrees C, and were visible by 1 0 days. S. sesban nodulated earlier than C. calothyrsus. Nodules were formed by 6 days after inoculation at 28-36 degrees C but at 20 degree s C were delayed until 10 days. Remarkably, nodulation still occurred at a root temperature of 40 degrees C. S. sesban was also grown at a r oot temperature of 32-28 degrees C (day-night) for 3 wk before being t ransferred to root temperatures of 22-18 degrees C, 32-28 degrees C, 3 6-32 degrees C and 40-36 degrees C (day-night). The maximum shoot dry mass occurred with day root temperatures of 32 and 36 degrees C. Shoot and nodule dry mass declined significantly at 40 degrees C, but nitro genase activity was still present 4 wk after transfer.