Fluorescence of Chlorophyll <i>a</i> for Discovering Inhibitors of Photosynthesis in Plant Extracts

Abstract

Aims: Twelve crude extracts were prepared from different parts of Pluchea sagittalis , Cecropia palmata and Brachiaria brizantha , and their effect on the light reaction of photosynthesis. Study Design: Use of fluorescence of ChL a (Chlorophyll a ) to detect inhibitors of photosynthesis in plant extracts. Place and Duration of Study: Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Departamento de Ciências Exatas e da Terra, Universidade Federal de Sao Paulo (UNIFESP), between July 2015 and January 2016. Methodology: The samples had their effect on the light reaction of photosynthesis studied by Chlorophyll a (Chl a ) fluorescence transient by the use of chloroplasts isolated from spinach leaves. As negative controls we used the same amounts of DMSO that have been employed to solubilize the samples, and as positive control we have used 10 μM of the commercial herbicide DCMU (Diuron). Results: The extracts inhibited the photosynthesis, and their inhibition sites were located in the range of electron flow from OEC complex and between P 680 to Q A of PS II, and inhibited the photosystem II (PS II) by inducing the appearance of the transient bands K and J. Conclusion: Our results suggest an indicative that the photochemical apparatus probably is failing at the donor and acceptor sides of PSII, causing damage to electron transport during the photosynthesis phenomenon.