P.W. Mokwala

Inhibition of Symbiotic Nitrogen Fixation by Dark Chilling in Soybean

Legume crops are an important source of protein, oil and secondary metabolites and they are also used as a natural nitrogen source in agriculture, particularly in Africa, because of presence of nitrogen-fixing bacteria in specialized organs called “nodules”. The symbiotic association between the plant and nitrogen-fixing bacteria in nodule formation has been the subject of intensive study but much less information is available on the mechanisms that cause the breakdown of symbiosis particularly during stress. Although the symptoms and progression of nodule senescence has been described, much remains to be discovered regarding the mechanisms that trigger the end of symbiosis and the genes and proteins that underpin nodule senescence (Puppo et al., 2005).