Abstract
The chloroplastic electron transport chain (ETC) plays an important role in the process of photosynthesis in the chloroplasts. Plastoquinone (PQ) is able to function as an electron carrier between photosystem II and cyctochrom b6/f complex in the chloroplastic ETC. It is reported that PQs involved leaf occurs in other chloroplast compartments different from thylakoid membranes. Although PQ redox depends on the light conditions, the redox state of non-carrier PQ independents on the states of chloroplastic ETC. We redesigned high performance liquid chromatography-based methods of determination of photoactive PQ as functional light response quinones in intact leaves. The range of oxidized states was from 35.2% to 77.7% in total PQs, and photoactive PQs was 42.5%. In intact leaf, non-oxidized and non-reduced forms showed 22.3% and 35.2%, respectively. Kruk et al. determined photoactive PQ in Arabidopsis leaves, However, the oxidized PQ decreased from 77.7% to 64.5% in spinach leaf segments without methyl viologen (MV). Therefore, non-photoactive PQ was overestimated in Arabidopsis leaves, because Kruk method lacked electron flow via stromal reductants.
