Effect of Trifluoroacetate, a Persistent Degradation Product of Fluorinated Hydrocarbons, on C3 and C4 Crop Plants

Abstract

TFA is a pollutant generated in the atmosphere by the degradation of hydrofluorocarbons (HFCs), as well as other anthropogenic sources such as teflon-cookware. The aim of this study was to quantify the physiological and biochemical basis of the inhibition of photosynthesis imposed by trifluoroacetate (TFA) in Phaseolus vulgaris and Zea mays, crop plants representing C3 and C4 photosynthesis respectively. Photosynthetic gas exchange and fast phase fluorescence kinetics were measured in parallel over a 12-day period in plants cultivated in a hydroponic system under strictly controlled conditions. Although initial stimulation of some photosynthetic parameters was observed at low TFA concentrations, marked inhibition occurred at higher concentrations. The inhibitory effect was reflected by chlorophyll a fluorescence and photosynthetic gas exchange derived parameters. Analysis of photosynthetic gas exchange revealed that besides constraints on mesophyll processes such as Rubisco activity and RuBP regeneration capaCity, stomatal limitation also increased with increasing TFA concentration, especially in P. vulgaris. Although the mechanism of inhibition was similar in both species, the C4 plants were affected more severely. In depth analysis of the fast phase fluorescence transients pointed at TFA-induced uncoupling of the oxygen evolving complex (OEC) and inhibition of electron transport beyond QA including constraints on ferredoxin- NADP+ oxidoreductase (FNR)-function.