Antioxidative response and photosynthetic performance of common fig (Ficus carica L.) leaves after short-term chilling stress

Abstract

Common fig (Ficus carica L.) is widely cultivated Mediterranean species. Such warm-climate species are adapted to elevated temperatures and are susceptible to chilling stress (0-12°C) [1]. However, occasional short chilling periods are common during growing season in temperature areas what can affect functionality of the plant [2]. The aim of this work was to investigate influence of short-term low temperature (chilling) on PSII photochemistry and antioxidative response in young, still developing leaves of common fig. Leaves were detached from the tree, acclimated at room temperature in dark for 12h and then exposed to low temperature (10°C) and low irradiation (50 µmolm-2s-1) for 4h. Dark adapted leaves were considered as the control. Photosynthetic performance was analyzed by measuring in vivo chlorophyll fluorescence increase (JIP test). The production of H2O2, lipid peroxidation (TBARS) and activity of antioxidative enzymes: superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and guaiacol peroxidase (GPOD) were measured as well. Maximum quantum yield of PSII (Fv/Fm) and overall photosynthetic performance (PItotal) decreased in leaves exposed to the chilling stress. Exposure to low temperature decreased absorption of light energy (ABS), trapping (TR0) of absorbed light energy and electron transport (ET0) further than primary acceptor (QA-) while energy dissipation (DI0) remained the same compared to the control. Moreover, reduction of the end electron acceptor (RE0) at photosystem I (PSI) also decreased after exposure to low temperature. The obstruction of photosynthetic electron transport flow is well documented reason for increased H2O2 production in leaves exposed to short-term chilling stress [1, 3]. In spite of increased H2O2 accumulation, the increase in TBARS level was not observed in the investigated leaves. Low temperatures inhibited activities of SOD and GPOD, while the CAT, APX and GR activities increased compared to the control. Our results suggest that antioxidative system was enough efficient to prevent the oxidative damage in biomembranes of fig leaves exposed to the chilling stress at 10°C.