Aluminum Stress Affects Growth and Physiological Characteristics in Oil Tea

High concentration of aluminum ion (Al3+) in acidic soil often negatively affects plant growth. To deepen understanding of the mechanisms of physiological response to Aluminum (Al) toxicity, changes in physiology and cell ultrastructure of oil tea (Camellia oleifera ) were investigated under different Al levels. Oil tea plants were grown in pots filled with sand and treated with Al at 0, 0.5,1.25, 2.0, or 4.0 mM. Results showed that Al at 0.5-2.0 mM improved plant growth, whereas Al at 4.0 mM inhibited root growth and damaged cell ultrastructure. Net photosynthetic rate (P-n), stomatal conductance (g(s)), transpiration rate (T-r), and photochemical efficiency increased as Al concentration increased from 0 to 2.0 mM; however, all parameters mentioned previously decreased at 4.0 mM. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in leaves treated with 2.0 mM Al reached the maximum, which were 29%, 63%, and 28% higher than that of control. When Al was <= 2.0 mM, the content of soluble sugar and soluble protein increased with increasing Al concentration. These results may indicate that oil tea adapted to Al stress through osmotic adjustment and through increasing antioxidant enzyme system. In summary, Al at low concentration (0.5-2.0 mM) improved growth and physiological performance, whereas 4.0 mM negatively impacted performance of oil tea.