Eco-physiological responses and symbiotic nitrogen fixation capacity of salt-exposed Hedysarum carnosum plants

Abstract

Nitrogen nutrition of Hedysarum carnosum, a pastoral legume common in Tunisian central and southern rangelands, largely depends on atmospheric nitrogen fixation. Yet, this process is greatly affected by environmental factors such as salinity. This study aimed to characterize the tolerance limits and the physiological responses of H. carnosum to salinity under symbiotic nitrogen fixation. Salt treatment was imposed by adding NaCl at different concentrations (0, 50, 100 and 200 mM) to the nutrient solution. Na + content generally increased in the plant organs with increasing salinity in the culture medium. Especially, an excess accumulation of this cation was observed in leaves. Despite the fact that Na + accumulation decreased plant growth, both nodulation and symbiotic nitrogen fixation capacity of H. carnosum appeared to be relatively salt-tolerant, owing to the plant capacity to maintain tissue hydration, control Na + accumulation in shoots, and to conserve nodule efficiency to fix N 2 . Taken together, our findings indicate that H. carnosum is a glycophyte that can tolerate moderate salinity (100 mM), suggesting its possible utilization (i) in the improvement of soil fertility and (ii) in saline pastures, where the survival of other fodder species is critical.

Green manure for soil salinity reclamation- A comprehensive review

“…For example, Hedysarum carnosum, a pastoral legume, was able to increase Na+ accumulation in the roots and maintain high symbiotic N2 fixation (SNF) efficiency and subsequent soil-N content under high salinity (100 mM NaCl), (Kouas et al, 2010). Application of organic amendments in the form of green manures and crop residues reduces pH and ESP of the alkali soils due to production of organic acids and increase in availability of Ca2+ that exchange with Na+ of clay complex leading to creation of favorable environment for microbial activity (Rao andPathak, 1996, Mahmoodabadi et al, 2013;Tejada & Benítez 2014, Vakeesan &Nishanthan, 2007.…”

Salt stress tolerance mechanisms and potential applications of legumes for sustainable reclamation of salt‐degraded soils

“…The advantage that N-fixing legumes have over N-non-fixing plants for reclaiming saline soils is that they not only have the potential to remove toxic ions but also to increase soil-N levels. For example, Hedysarum carnosum, a pastoral legume, was able to increase Na + accumulation in the roots and maintain high symbiotic N 2 fixation (SNF) efficiency and subsequent soil-N content under high salinity (100 mM NaCl), suggesting its potential utilization in the improvement of soil fertility under saline conditions (Kouas, Slatni, Ben Salah, & Abdelly, 2010). Also, tree legumes such as Acacia nilotica and Leucaena leucophela have been grown as fodder under saline conditions with slight reduction in SNF efficiency at 90 mM NaCl (Bruning & Rozema, 2013).…”