XVI International Botanical Congess
Nitrogen fixation in soybean deceases during water deficits where as is a required cofactor for ureide degradation in leaves, and it was hypothesized that increased Mn+2 in leaves would alleviate ureide fixation. Supplying ureides through roots decreased N2 fixation in well watered plants, and soybean variety with demonstrated tolerance of ureides following exogenous ureide application than a variety sensitive to water deficits (KS4895). Nitrogen fixation in Jackson under moderate water deficits was 86% of the control in the absence or presence of soil-applied Mn+2. Nitrogen fixation in KS4895 under moderate water deficit was 26% of the control in the absence of soil-applied Mn+2 and 98% of the control in the presence of soil-applied Mn+2. Increased N2 shoot ureide concentration. It was concluded that ureide accumulation inhibits N2 fixation and that increased Mn+2 promotes ureide breakdown and prolongs N2 fixation under water deficits.