Growth and physiological responses of Sporobolus robustus kunth seedlings to salt stress

ABSTRACT

Seedlings of S. robustus were exposed to increasing NaCl concentrations (0, 50, 100, 150, 200, 250, and 300 mM) for 50, 100, and 150 days, in greenhouse conditions. Total dry weight and salt tolerance index decreased gradually with increasing NaCl concentrations. The optimum growth of S. robustus (4.12 to 5.25 g · plant⁻¹) was obtained between 0 and 150 mM at 150 days after salt stress. Foliar chlorophyll a and total chlorophyll contents increased with NaCl concentration at 50 days after treatment. There was no significant effect of salinity on chlorophyll a, b and total chlorophyll contents at 100 and 150 days after treatment. Higher Na contents were found in the shoots as compared to the roots. The Na content increased, while K decreased with increasing NaCl concentrations, suggesting competitive inhibition between absorptions of Na and K as a consequence, the K/Na ratios in shoots and roots decreased with increasing salinity. The proline contents in S. robustus were more pronounced at 300 mM (2.02 µmol/g), 250 mM (2.64 µmol/g), and 200 mM NaCl concentrations (2.98 µmol/g) for 50, 100, and 150 days, respectively, as compared to the treatment without added NaCl. Overall, S. robustus could be considered as salt tolerant on the basis of their performance in biomass production, accumulation of Na, similar foliar chlorophyll a, chlorophyll b and total chlorophyll contents, and accumulation of proline with increasing salinity. The potential ability of S. robustus to accumulate significant amounts of Na makes this halophyte promising as a desalinization tool of salted soils.

KEYWORDS:

• Biomass production
• chlorophyll
• grass
• Na accumulation
• osmotic adjustment
• proline

Acknowledgments

The authors are grateful to Dr. Jacinta Kimiti (South Eastern Kenya University) for revising the text in English.