Effect of exogenous Ca on the physiology and growth indicators of pakchoi under foliar and root fluorine stress.

Abstract

Abstract Fluorine (F) is not an essential element for vegetation and excessive F can be phytotoxic to plant growth, which can cause fluorosis to human beings by ingesting F-contaminated plant. Although there have been some studies focusing on the toxicity of F to plants and propose that some substance which have calcium (Ca) as its principal component could be a retardant, atmospheric F contamination to vegetation and the role of the application of foliar Ca are scantly reported. This study deals with F exposure approaches of roots and leaves of pakchoi, together with the foliar application of Ca(NO3)2, and analyses some biochemical parameters to evaluate F toxicity under both exposure and the remedial effects of foliar Ca. The results showed that F concentration of pakchoi leaves (LF) was correlated with exogenous F level positively in both foliar and root exposure series, and F concentration of pakchoi roots (RF) was only changed under root exposure treatments. Ca supplement (0.5, 1 g/L) significantly decreased plant F concentration. Both exposure treatments caused lipid peroxidation in plants and exogenous Ca alleviated the toxity of Fto pakchoi. Meanwhile, chlorophyll-a concentration was decreased by foliar and root F, whereas chlorophyll-b concentration was only affected by foliar F, and chlorophyll-a concentration could be elevated by exogenous Ca but chlorophyll-b could not. It was concluded that both atmospheric and root F can impaire pakchoi growth and disturb photosynthesis, and foliar Ca showed a retarder effect to F toxicity of plants through alleviating chlorophyll decomposition, increasing protein content and alleviating oxidative damage.