High irradiation and increased temperature induce different strategies for competent photosynthesis in young and mature fig leaves.

To achieve and maintain optimal and effective photosynthetic functioning under limiting or excess irradiation, acclimation of photosynthetic apparatus requires coordination of biochemical and physiological processes. Due to these processes, leaves usually display high ability to adjust to alteration of microclimate conditions. Photochemical and biochemical adaptations in young and mature leaves of common fig ( Ficus carica L.) in response to combination of high irradiation (~ 1300 μmol m − 2 s − 1 ) and increased temperature (~ 35 °C) at midday in the field were investigated. Therefore, photosynthetic performance, accumulation of Rubisco large subunit (LSU), activity of enzymatic antioxidants, and oxidative damage on membrane lipids in the morning and at midday were determined. Photosynthetic efficiency (Fv/Fm) in young leaves at midday significantly decreased going along with lower amount of accumulated Rubisco LSU. High irradiation and increased temperature caused significant increase of catalase and peroxidases activities in young leaves, leading to unchanged level of lipid peroxidation. Mature leaves decreased their total chlorophyll content at midday which was accompanied with steady photosynthetic efficiency, shown as constant maximum quantum efficiency and unchanged amount of Rubisco LSU. The level of lipid peroxidation increased in mature leaves, suggesting that increased activities of superoxide dismutase and catalase were not sufficient to prevent oxidative damage. Photoprotective strategies in young leaves enabled them to minimize oxidative damage due to competent antioxidative system and downregulated photosynthetic activity while mature leaves maintained their photosynthetic functionality although they did not have completely efficient antioxidative system. [ABSTRACT FROM AUTHOR]