Impact of Hypoxia on Nodulation and Growth of the Legume Plant Medicago truncatula in Symbiosis with Sinorhizobium meliloti

Abstract

Legumes form a symbiotic interaction with bacteria of the Rhizobiaceae family to develop nitrogen-fixing root nodules under nitrogen-limiting conditions. The present study aimed at analysing the impact of two- and four-week long periods of hypoxia on the nodulation and the growth of the legume plant Medicago truncatula (var Jemalong A17) in symbiosis with Sinorhizobium meliloti. Results showed that the nodulation was not affected by moderate hypoxia (4.5% O2), but the number of nodules decreases for high hypoxia (0.1% O2) and anoxia. The analysis of growth parameters (fresh and dry weight, leaf area and thickness, chlorophyll contents) and of various metabolite contents (total sugars, chlorophylls, inorganic nitrogen compounds) in the leaves, roots and nodules showed that nodulated Medicago truncatula tolerates periods of 4 weeks hypoxia and may be considered as a hypoxia-tolerant legume plant.