Article

Effect of salinity on root-nodule conductance to the oxygen diffusion in the Cicer arietinum Mesorhizobium ciceri symbiosis

Department of Biology, Faculté des Sciences de Tunis, Tunis-Ville, Tūnis, Tunisia
Journal of Plant Physiology (Impact Factor: 2.77). 09/2007; 164(8):1028-36. DOI: 10.1016/j.jplph.2006.05.016
Source: PubMed

ABSTRACT Nodule conductance to O2 diffusion has been involved as a major factor of the inhibition of N2 fixation by soil salinity that severely reduces the production of grain legumes. In order to determine the effect of this constraint on the nodule conductance, oxygen uptake by the nodulated roots of Cicer arietinum was measured by recording the concentration of O2 as a function of pO2 in a gas-tight incubator. After germination and inoculation with the strain Mesorhizobium ciceri UPMCa7, the varieties Amdoun 1 and INRAT 93-1 were hydroponically grown in a glasshouse on 1L glass bottles filled with nutrient solution containing 25 mM NaCl. Salinity induced a marked decrease in shoot (30% versus 14%), root (43% versus 20%), and nodule biomass (100% versus 43%) for Amdoun 1 relative to INRAT 93-1. Although salinity completely prevented nodule formation in the sensitive variety Amdoun 1, nodule number and biomass were higher in the first than in the second variety in the absence of salt. This effect was associated with a significantly higher O2 uptake by nodulated root (510 versus 255 micromol O2 plant(-1)h(-1)) and nodule conductance (20 versus 5 microm s(-1)) in Amdoun 1 than in INRAT 93-1. Salinity did not significantly change the nodule conductance and nodule permeability for INRAT 93-1. Thus, the salt tolerance of this variety appears to be associated with stability in nodule conductance and the capacity to form nodules under salt constraint.

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    • "Pre-sowing sodium chloride treatment significantly affected the seedlings as well as reduced the nodule number, their biomass and the nitrogenase activity at mature stage (Table 1). In this study, decline in nodule number and nodule fresh/dry biomass under salt stress is in confirmation with the reported findings (Ashraf and Bashir, 2003; Ltaief et al., 2007). Nodules of pea are noted to be differentially affected as compared with other vegetative parts as a consequence of salt stress (Cordovilla et al., 1999; Salah et al., 2009). "
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    • "Maximum salinity tolerance was achieved in Pusa-329 through mycorrhizal inoculation at 4 dS m -1 in the rooting medium, where complete amelioration of negative eff ects of salinity was observed and the shoot and root biomass were even greater than in the untreated controls. Th e results from this study agree with previous data (Rabie and Almadini 2005; Sannazzaro et al. 2006; Tufenkci et al. 2006; Sharifi et al. 2007). "
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    • "According to several authors, the inhibition of N 2 fixation under moderate salinity may be related to a decrease in bacteroid respiration (L'taief et al., 2006) and nodule leghemoglobin contents (Lopez et al., 2008). Indeed, salt stress increases cortical barrier to O 2 diffusion in the nodule, which enhances the activity of enzymes involved in anaerobic metabolism (Aydi et al., 2004). "
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