Effects of Soil Alkalization on Osmotic Adjustment and Ion Balance in Sorghum (Sorghum Bicolor L.)

Abstract

Sorghum (Sorghum bicolor L.) was grown on an alkalinized plot for 90 days. Inorganic ions and compatible solutes were measured to investigate the physiological adaptations by which sorghum tolerates natural alkaline stress. Plant growth was clearly inhibited. The stress led to increased Na⁺ content in roots but had only a small effect on Na⁺ accumulation in leaves; K⁺ content in roots was lower than that in leaves and stems; and Na⁺ content and Na⁺/K⁺ ratio were much higher in roots than in leaves and stems. These suggest that maintaining a substantially higher osmotic potential in roots for greater uptake of water and restricting the spread of Na⁺ to shoots are physiological adaptations to alkalinity. Soluble sugar was the main osmolyte in roots, stems, and leaves; proline, amino acids, and oxalates contributed to osmotic regulation slightly, and it was noteworthy that K⁺ played a major role in osmotic regulation in leaves.

Keywords:

• growth
• natural alkaline stress
• osmotic adjustment
• Sorghum bicolor L.