Effects of propyl gallate on photosystem II efficiency in Dunaliella bardawil under high illumination as investigated by chlorophyll fluorescence measurements

Abstract

Effects of n-propyl gallate, a plastid terminal oxidase inhibitor involved in chlororespiration, on photosystem II efficiency in Dunaliella bardawil under low or high illumination was investigated. Rapid chlorophyll a fluorescence transients were recorded and analyzed according to JIP-test, which can quantify the photosystem II performance. The fluorescence transients O-J-I-P drastically decreased and almost reached a plateau when low light-grown cells were exposed for 96 h to 1, 2 and 4 mM n-propyl gallate. Very similar reductions in the efficiency of quantum yield of primary photochemistry (Φpo), the quantum yield for electron transport (ΦEo) and the inferred water-splitting complex activity (Fv/Fo) were found in the same inhibitor concentrations. However, no statistically significant change in fluorescence intensity and photosystem II efficiency was found when algal cells were exposed to the inhibitor concentrations up to 2 mM under high light intensity. The results indicated that inhibitory effects of n-propyl gallate on photosystem II electron flow in D. bardawil cells are dependent on environmental conditions. It is also demonstrated that n-propyl gallate is a multi-target inhibitor of growth kinetics as well as photosynthesis. In addition, we found that the donor side of photosystem II acts as main target place of the inhibitor. © 2015, Brazilian Society of Plant Physiology.