Is salt stress tolerance in Casuarina glauca Sieb. ex Spreng. associated with its nitrogen-fixing root-nodule symbiosis? An analysis at the photosynthetic level

Influence of salt stress on inoculated Casuarina glauca seedlings

“…Our study shows that the process of N 2 -fixation, as a result of the interaction between C. glauca and Frankia strains CcI156 and CgIM4, is sharply affected by salt at 200 mM (Table 1). This reduction can be attributed to a reduction in nodules respiration (Delgado et al 1994;Dupont et al 2012) and a reduction in cytosolic protein production, specifically leghemoglobin, in the nodules (Serraj et al 1994) or/and reduction in photosynthetic activity (Batista-Santos et al 2015). The depressive effect of salt stress was also clarified and confirmed in Legumes by Bolanos et al (2006) who hypothesized the failure was due to bacteroid respiration and adequate leghemoglobin levels to keep a suitable oxygen environment for N 2 -fixation.…”

“…Reduction of N 2 -fixing activity in legumes (Delgado et al 1994) and non-leguminous plants (Batista-Santos et al 2015) are typical effects of salt stress. Our study shows that the process of N 2 -fixation, as a result of the interaction between C. glauca and Frankia strains CcI156 and CgIM4, is sharply affected by salt at 200 mM (Table 1).…”

Comparative Proteomic Analysis of Nodulated and Non-Nodulated Casuarina glauca Sieb. ex Spreng. Grown under Salinity Conditions Using Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS)

“…However, broad, interdisciplinary and integrate research to ascertain the contribution of symbiotic Frankia to the environmental plasticity of actinorhizal species has emerged only recently, mostly focusing on salt stress in Casuarinaceae, particularly in the model species Casuarina glauca Sieb. ex Spreng e.g., Santos et al, Ribeiro et al, Batista-Santos et al, Mansour et al, Ribeiro-Barros et al, Jorge et al, and Ngom et al [2][3][4][5][6][7][8][9]. C. glauca is a tropical tree widely used to prevent desertification and erosion, as well as to rehabilitate poor and degraded soils [1,10].…”

“…C. glauca is a tropical tree widely used to prevent desertification and erosion, as well as to rehabilitate poor and degraded soils [1,10]. Such capacity does not necessarily depend on the symbiosis with Frankia, although some strains may enhance stress tolerance [4][5][6]9,[11][12][13].…”

“…For that, we have examined the impact of increasing NaCl concentrations (200, 400 and 600 mM) on plant growth, mineral contents, water relations, photosynthesis-related parameters and non-structural sugars [4,12,13], membrane integrity and the control of oxidative stress [21], as well as the metabolome of nodules, roots and branchlets from nodulated and non-nodulated C. glauca plants [7,8,22]. According to Batista-Santos et al [4], the C. glauca ecotype used in these studies exhibits outstanding salt stress tolerance showing the first stress symptoms, i.e., phenotypic changes (chlorosis and necrosis of branchlets, reduction of stem diameter and biomass decrease in both KNO 3 + and NOD + groups; and swollen nodules with salt crystals at the surface in NOD + plants), and the impairment of photochemical (e.g., photosynthetic electron flow) and biochemical (e.g., activity of photosynthetic enzymes) parameters only at 600 mM NaCl. This has been associated with a remarkably low level of tissue dehydration combined with strong osmotic adjustments, features that are essential to maintain a potential gradient of water influx and to sustain metabolic activity [15].…”