Physiological and biochemical responses to salt stress of mycorrhized and/or nodulated clover seedlings (Trifolium alexandrinum L.)

Salt stress (0, 4, 6 and 8 g NaCl . L-1) effects on arbuscular mycorrhized and/or nodulated clover ( Trifolium alexandrinum L.) seedlings grown in greenhouse conditions under 75% field capacity were evaluated. The autochthonous mycorrhizal (AM) seedlings showed the best salt tolerance and biomass production improvement (+ 65%) for all the tested concentrations. AM root colonization was the highest (71%) and did not seem to be affected by salt doses. The double symbiosis ( mycorrhization and nodulation) was found to be less efficient than single inoculations and revealed some antagonism between the fungus and Rhizobium. Phosphate nutrition was improved, mainly in the cases of single mycorrhized plants; this nutritional effect seems to be the main mechanism involved in salt tolerance. The leaf protein content was also improved by both types of symbiosis. Proline accumulated especially in the doubly inoculated ( AM and Rhizobium) plants; meanwhile, sugars accumulated in the cases of single inoculations. However, the intensity of the salt stress showed a positive correlation with sugar accumulation for the plants which were only mycorrhized.