Plant determined ineffective nodules in alfalfa (Medicago sativa): structural and biochemical comparisons

Publisher Website
Google Scholar
Abstract
Nodule structure, nodule enzymes of ammonia assimilation, nodule phosphoenolpyruvate carboxylase, nitrogenase-dependent acetylene reduction [N2 fixation assay] and soluble protein were studied in 4 plant-determined ineffective genotypes and in 1 effective genotype of alfalfa (M. sativa L.) grown in a glasshouse. Ineffective nodules that formed on genotypes MnAg(In) and MnSa(In) were similar to effective nodules in early development. These nodules had smaller bacteroids and senesced much more rapidly than effective nodules. In contrast, nodules that formed on ineffective genotypes MnNC-3226(In) and MnNC-3811(In) were tumor-like and had few infection threads and bacteroids [Rhizobium meliloti], and host cells were filled with starch. Nodules from plant-determined ineffective genotypes had reduced glutamine synthetase, glutamate synthase, phosphoenolpyruvate carboxylase and nodule soluble protein when compared with effective nodules. There were differences between genotypes for all biochemical parameters assayed.