ESSENTIALITY OF BORON FOR SYMBIOTIC DINITROGEN FIXATION IN PEA (PISUM-SATIVUM) RHIZOBIUM NODULES

The effect of boron deficiency on symbiotic nitrogen fixation in pea ( Pisum sativum) was examined. The absence of boron in the culture mediu m resulted in a decrease of the number of nodules and an alteration of nodule development leading to an inhibition of nitrogenase activity. Examination of boron-deficient nodules showed dramatic changes in cell walls and in both peribacteroid and infection thread membranes, sugge sting a role for boron in the stability of these structures. These res ults indicate that boron is a requirement for normal nodule developmen t and functionality.