Could the fluoride-tolerant species Panicum maximum replace sensitive plants in fluoride biomonitoring?

Fluoride (F) is the most phytotoxic atmospheric pollutant. The use of plants for passive or active biomonitoring has been a common strategy to detect abnormal atmospheric F concentrations. Tree species are mostly used, although the high sensitivities of some, associated with costly processes of plant replacement, will increase cost outlays associated with F-biomonitoring processes. After a few days of exposure, F-sensitive species often die, and must be replaced in active biomonitoring stations. We therefore investigated the potential use of the grass Panicum maximum for atmospheric F biomonitoring. Although that grass shows fast accumulations of F in their leaves, no visual symptoms of intoxication were observed. Despite of their F-tolerance, plants showed reliable microscopic responses to F (epicuticular wax erosion, plasmolysis of bulliform cells, and damage associated with trichomes). Since microscopic evaluations are mandatory in F-biomonitoring projects, the use of grass species such as P. maximum that show F-tolerance, fast F-uptake and reliable microscopic responses, could represent an option for F biomonitoring that would decrease costs related to plant production and replacement in monitoring stations.

Automated summary

Fluoride is the most phytotoxic atmospheric pollutant and plants are commonly used for monitoring purposes. While tree species are often used, their high sensitivity and costly replacement processes can increase monitoring costs. This study found that Panicum maximum grass may be a suitable alternative for fluoride monitoring, as it shows fast fluoride uptake and reliable microscopic responses despite being fluoride-tolerant.