Iron-stress response in mixed and monocultures of soybean cultivars

Hawkeye (Fe-efficient) and PI-54619-5-1 (Fe-inefficient) soybeans (Glycine max [L.] Merr.) were grown in mixed and monoculture nutrient solutions to evaluate an inhibitory effect of PI-54619-5-1 on the uptake of Fe by Hawkeye. The ability of Hawkeye to take up Fe (Fe-stress response) was dependent on the degree of Fe stress (Fe deficiency) and was not the result of an inhibitory substance released by PI-54619-5-1 in mixed culture (Hawkeye + PI-54619-5-1). The degree of Fe stress in Hawkeye was dependent on the amount of Fe taken up by the plant. Hawkeye took up more Fe and developed less Fe stress in mixed than in monoculture because in mixed culture PI-54619-5-1 did not utilize Fe as efficiently as Hawkeye which allowed more Fe to be available per HA plant. Thus, Fe-stress response, rather than any inhibitory substances produced by PI-54619-5-1 plants, controls the uptake of Fe in Hawkeye soybean.