Physiological effects induced by aluminium and fluoride stress in tall fescue (Festuca arundinacea Schreb)

Aluminium (Al) and fluoride (F) are phytotoxic elements that can inhibit plant growth and development. Al3+ and F- can react with each other to form complexes in the soil which will induce alteration of toxicity of single element. However, the mechanisms of plant response to aluminium fluoride induced toxicity are not very clear. In the present study, tall fescue (Festuca arundinacea Schreb) cultivar ‘Houndog 5′ was treated by 0, 0.4, 4, 20 mg·L−1 Al2(SO4)3 and 0, 0.5, 5 mg·L−1 NaF, respectively. After 25 days of treatment, leaf samples were collected for physiological evaluation. The results showed that several forms of Al-OH and Al-F complexes such as Al(OH)2+, AlOH2+, Al(OH)3, Al(OH)4-, Al2(OH)24+, Al3(OH)45+, AlF2+, AlF2+, AlF3 and AlF4- were formed in Al3+ and F- combined solution. The nutrient uptake including Al, P and K were improved by Al3+ and F-. Under Al3+ stress, the MDA (malondialdehyde) content and EL (electrolyte leakage) dramatically increased after high concentration of F- treatment, while relative low concentration of F induced decrease of MDA content and EL. On the contrary, chlorophyll content decreased significantly after high concentration of F treatment. The photosynthesis efficiency parameters, including φP0 (Fv/Fm), δR0 and PIABS, decreased remarkably after high concentration of Al and F treatment. However, L-band incresed after high concentration of Al3+ and F- treatment. The results of correlation analysis showed that MDA content and EL negatively correlated with other indexes, and Al-F complex significantly correlated with MDA, Pro and EL but negatively correlated with Chl and φP0. These results suggested that low concentration of F could alleviate the damage induced by Al stress in tall fescue, but high concentration of Al and F combined solution had negative effects on the growth and development of tall fescue.