Antioxidative Response And Photosynthetic Regulatory Mechanisms In Common Fig Leaves After Short-Term Chilling Stress

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 degrees C). However, occasional short chilling periods are common during growing season in temperate areas that can affect functionality of the plant. The aim of this work was to investigate influence of short-term chilling stress on antioxidative response and PSII photochemistry in developing leaves of two common fig varieties: Zamorcica and Green matalon. Leaves were detached from the trees, acclimated at room temperature in dark for 16 hr and then exposed to low temperature (10 degrees C) at low irradiation (50 mu mol m(-2) s(-1)) for 4 hr. Dark adapted leaves were considered as the control. The damage to the membranes was determined as lipid peroxidation (thiobarbituric acid reactive substances) while the antioxidative response was evaluated by determining activities of the selected antioxidative enzymes. Photosynthetic performance was analysed by measuring in vivo chlorophyll a fluorescence (ChlF) increase. Relative accumulation of the main photosynthetic proteins (D1 and Rubisco LSU) was determined, as well. Due to efficient antioxidative activity, neither of investigated variety showed damage of the membrane lipids. Both varieties revealed functional antennae and its good connectivity to their reaction centres shown as negative L and K bands as well as stable D1 protein accumulation suggesting functional electron transport through photosystem II (PSII) and efficient primary photochemistry. Blocked electron flow further than Q(A) resulted in limitation of the Photosystem I (PSI) functionality in both varieties. Due to differential relative accumulation of D1 and Rubisco LSU proteins upon the chilling stress, Zamorcica revealed greater decrease of the main photosynthetic parameters derived from in vivo ChlF induction (PItotal, PIABS and phi(P0)) in comparison to Green matalon. In addition, increased specific energy fluxes through PSII in Zamorcica suggested its higher susceptibility to photoinhibition caused by chilling stress in comparison to Green matalon.