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

Abstract

Article InfoLegumes 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% O 2 ), but the number of nodules decreases for high hypoxia (0.1% O 2 ) 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.

Exploring Legume-Rhizobia Symbiotic Models for Waterlogging Tolerance

“…Hypoxia-sensitive legumes, such as pea (Minchin and Pate, 1975), alfalfa (Arrese-Igor et al, 1993), and soybean (Sung, 1993) exhibit reduced nodule weight when grown under hypoxic conditions. Medicago truncatula nodulation shows a 45% decrease under 0.1 % O 2 but is not affected by 4.5% O 2 treatment, and the nodule fresh weight per plant is not dampened by 4 weeks of hypoxia (El Msehli et al, 2016). Two studies analyzing nodulation ratings of 21 species of annual pasture legumes and 13 species of perennial legumes (Nichols et al, 2008a,b) report that most legume, including waterlogging sensitive species such as Melilotus albus and Medicago sativa , showed effective nodulation after several weeks of inundation.…”