Effects of Fluorine on the Growth of Broad Bean (Vicia faba L.) and Maize (Zea mays L.) and the Response of Microbial Community in Soils

Abstract

Fluorine (F) is widely distributed in soils and is not an essential element for the normal growth of a plant, but in higher concentrations, it is toxic. However, the environmental toxicity of F in soils is still controversial. A pot experiment of broad bean and maize under the exposure to F was performed to elucidate F phytotoxicity and the response of the microbial community in soils. Six different levels (0, 200, 400, 600, 800, and 1000 mg kg–1) of sodium fluoride were spiked into the soil. The results revealed that the height of stem and root decreased with increasing concentration of F. Germination rate and fresh weight showed no difference in different treatments. At the treatment of 1000 mg kg−1 F, the degradation rates of pigments were 30.6%, 42.9%, and 35.7% for chlorophyll a, chlorophyll b, and total chlorophylls compared with control, respectively. All treatments showed a higher level of F accumulation in root than that in stem and leaf, and stem had a minimum F accumulation. Proteobacteria was the dominant species in bacteria and the relative abundance of Proteobacteria declined significantly with F exposure. Moreover, the number of microbial species both in bacteria and fungus was reduced for the increase of F. In general, our results revealed that high concentrations of F inhibited the growth of broad bean and maize but without visual symptom. The effect of fluorine on broad bean and maize is clarified in the present study which is instructive for agricultural safety.