Casting light upon the impact of salinity stress on growth and nitrogen fixation of Vicia faba supplemented with
Rhizobium has been traced in this work. How Ca2+
antagonizes Na+
toxicity and osmotic stress of NaCl was also targeted in
isosmotic combinations of NaCl and CaCl2
having various Na+:
Ca2+ ratios. Growth of Vicia faba (cultivar Giza 3) was studied
at two stages: germination and seedling. At both experiments, seeds or seedlings were exposed to successively increasing
salinity levels (0, 50, 100, 150, and 200 mM NaCl) as well as isosmotic combinations of NaCl and CaCl2
(
Na+:Ca2+ of 1:1,
1:5, 1:10, 1:15, 1:18, and 1: 20), equivalent to 150 mM NaCl. Inocula of the local nitrogen-fixing bacteria, Rhizobium leguminosarum
(OP715892) were supplemented at both stages. NaCl salinity exerted a negative impact on growth and metabolism
of Vicia faba; inhibition was proportional with increasing salinity level up to the highest level of 200 mM. Seed germination,
shoot and root lengths, fresh and dry weights, chlorophyll content, and nodules (number, weight, leghemoglobin, respiration,
and nitrogenase activity) were inhibited by salinity. Ca2+
substitution for Na+,
particularly at a Na/Ca ratio of 1:5, was
stimulatory to almost all parameters at both stages. Statistical correlations between salinity levels and Na/Ca combinations
proved one of the four levels (strong- or weak positive, strong- or weak negative) with most of the investigated parameters,
depending on the parameter.