Effect of salinity on growth, photosynthesis and mineral composition in leguminous plant Alhagi pseudoalhagi (Bieb.)

Leguminous plant Alhagi pseudoalhagi was subjected to 0 (control), 50, 100, and 200 mM NaCl treatments during a 30 d period to examine the mechanism o f tolerance to salinity. Plant dry weight, net CO2 assimilation rate, leaf stomatal conductance, intercellular CO2 concentration, and solute concentra tion in leaves, stems, and roots were determined. Total plant weight in the 50 mM treatment was 170% of that of the control after 10 d of treatment. T otal plant weight was lower in the 100 and 200 mM treatments than in the co ntrol. The leaf CO2 assimilation rate was approximately 150% of that of the control in the 50 mM treatment, but was not affected significantly by 100 mM of NaCl, while it was reduced to about 60% of that the control in the 20 0 mM treatment. Similarly stomatal conductance was consistent with the CO2 assimilation rate regardless of the treatments. Intercellular CO2 concentra tion was lower in the NaCl-treated plants than in the control. Changes in C O2 assimilation rate due to salinity stress could be mainly associated with stomatal conductance and the carboxylation activity. Although the leaf Na concentration increased to 900 mmol kg(-1) dry weight in the 200 mM treatm ent compared to 20 mmol kg(-1) in the control, the plants did not die and c ontinued to grow at such a high leaf Na+ concentration. Uptake and transpor tation rates of Na+, Ca2+, Mg2+, and K+, and the accumulation of N were pro moted by 50 mM NaCl. Na+ uptake rate continued to increase in response to e xternal NaCl concentration. However, the uptake and transportation rates of Ca2+, Mg2+, and K+ behaved differently under 100 and 200 mM salt stress. T he results suggest that A. pseudoalhagi is markedly tolerant to salinity du e mainly to its photosynthetic activity rather than to other physiological characteristics.