Abstract

FERNANDEZ-LUQUENO, Fabián  and  ESPINOSA-VICTORIA, David. Biochemistry, Physiology and Morphology of Nodule Senescence: a Critical Review. Terra Latinoam [online]. 2008, vol.26, n.2, pp.133-144. ISSN 2395-8030.

The nodule is a new organ which results from the highly specific interaction between rhizobia and legume roots and stems. The nodule fixes atmospheric nitrogen during a specific period of the symbiosis lifetime. Then, this activity decreases leading to nodule lysis and death. Nodule senescence is a cluster of physiological, biochemical and morphological alterations induced by natural aging and stress conditions. Nodules are classified in terms of their development as determinate or indeterminate, and they exhibit different patterns of senescence. In soybean, alfalfa, common bean, and pea nodules different compounds have been identified which are involved in the senescence process, such as proteases, types of reactive oxygen, nitrogenase, leghaemoglobin, plant growth promoters, polyamines, phytoalexins, and vitamins. Cellular organelles such as mitochondria, chloroplasts, cell membrane, Golgi apparatus, and nuclei undergo important alterations during nodule senescence. Delay of nodule senescence could increase the nitrogen fixing period, which might have beneficial agronomic and environmental implications. Little is known about the mechanisms involved in nodule senescence. Genetic manipulation might be used to reduce the expression of genes which encode the synthesis of compounds that degrade the nodule structure or to trigger the nodule defense mechanisms against antagonistic metabolites.

Keywords : nitrogen fixation; rhizobia; polyamines; symbiosis; stress.

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