Environmental and Experimental Botany 109 (2015) 80–88 Contents lists available at ScienceDirect Environmental and Experimental Botany jo ur nal home p ag e: www.elsevier.com/locate/envexpbot Correlation between reactive oxygen species production and photochemistry of photosystems I and II in Lemna gibba L. plants under salt stress Abdallah Oukarroum a,∗ , Filippo Bussotti b , Vasilij Goltsev c , Hazem M. Kalaji d a Department of Chemistry and Biochemistry, University of Quebec in Montreal, C.P. 8888, Succ. Centre-Ville, 8 Montreal, Quebec, Canada H3C 3P8 b Department of Agri-food Productions and Environmental Science, Section of Plant and Soil Science, Piazzale delle Cascine, Firenze, Italy c Department of Biophysics and Radiobiology, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia, Bulgaria d Department of Plant Physiology, Faculty of Agriculture and Biology, Warsaw Agricultural University SGGW, Nowoursynowska 159, 02-776 Warsaw, Poland a r t i c l e i n f o Article history: Received 14 April 2014 Received in revised form 16 July 2014 Accepted 14 August 2014 Available online 23 August 2014 Keywords: Lemna gibba Photosystem I Photosystem II Reactive oxygen species Salt stress a b s t r a c t Increased rate of reactive oxygen species (ROS) is a common plant response to various environmental stresses. In chloroplast thylakoids, the reaction centers of photosystems I and II are the major generation site of ROS. In the present study, the changes of chlorophyll a fluorescence parameters, P700 absorption change and ROS production (using the fluorescent probe 2,7-dichlorofluorescin diacetate) were inves- tigated in Lemna gibba plants exposed to salt stress (0–400 mM NaCl). Salt stress inhibited PSI and PSII activities and resulted in a decrease in overall activity of the electron transport chain while stimulating ROS production. When L. gibba plants were kept into dark condition, NaCl treatment did not showed any significant change in ROS formation compared to control. However, NaCl treatment in light condition induced a strong increase in ROS formation. The production of ROS at 400 mM NaCl was 2.6 and 10 fold higher compared to the control respectively after 6 h and 24 h treatment in light. Furthermore, the corre- lation between ROS production and the two photosystems (PSI and PSII) activities in L. gibba plants was analyzed. Our data confirmed the correlation between the ROS production and PSII and PSI activities. We showed that ROS production was highly correlated to maximal quantum yield of PSII (R 2 = 0.91) and effi- ciency with which a trapped exciton can move an electron into the electron transport chain (R 2 = 0.86). While the correlation coefficient (R 2 ) value ROS formation and I/I o 820 nm (measure of redox states of plastocyanin and P700) was 0.63. © 2014 Elsevier B.V. All rights reserved. Abbreviations: ϕPo, maximum quantum yield of primary photochemistry; o, efficiency with which a trapped exciton can move an electron into the electron transport chain; ϕRo, quantum yield with which electrons reduce the PSI end elec- tron acceptors; ıRo, efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end electron acceptors; ABS, absorption; Chl a, chlorophyll a; Fo (F20 s ) and FM, initial and maximum Chl a fluorescence; OJIP transient, fluorescence induction transient defined by the names of its intermedi- ate steps; PI total , performance index and the probability that an electron can move from the reduced intersystem electron acceptors to the PSI end electron acceptors; P700, the primary electron donor of photosystems I; PSII, photosystem II; Q A and QB, primary and secondary quinone electron acceptors of photosystem II, respectively; RC, reaction center; VI , relative variable Chl a fluorescence at the I-step; VJ , relative variable Chl a fluorescence at the J-step; Vt , relative variable Chl a fluorescence at time t. ∗ Corresponding author. Tel.: +1 514 987 3000; fax: +1 514 987 4054. E-mail addresses: Oukarroum.abdallah@uqam.ca, abdallah.oukarroum@gmail.com (A. Oukarroum). 1. Introduction Photosynthesis is considered as one of the most important metabolic processes in plants and its performance is greatly affected under stress conditions (Baker, 1991). However, in a chang- ing environment, plants were able to adapt their metabolism in order to cope with stress and maintain a steady-state balance between energy production and consumption (Asada, 2006; Suzuki et al., 2012). Abiotic or biotic plant stress causes generation of reactive oxy- gen species (ROS) (Møller and Sweetlove, 2012). Nevertheless, an increased rate of ROS is a common plant response to various environmental stresses (Bhattacharjee, 2005). It is important to state that ROS accumulation in plants during an environmental stress depends on the balance between ROS production and ROS scavenging (Mittler et al., 2004). Further, in freshwater ecosys- tems, plants actively scavenged ROS during normal growth through http://dx.doi.org/10.1016/j.envexpbot.2014.08.005 0098-8472/© 2014 Elsevier B.V. All rights reserved.