ACCLIMATION OF PEDUNCULATE OAK SEEDLINGS TO DIFFERENT LIGHT CONDITIONS IN THE FIRST MONTHS AFTER GERMINATION

Abstract

The first months are the most sensitive phase of oak seedling development. Light conditions have an important role in this sense, both from the physiological and management viewpoint. We investigated the response of pedunculate oak seedlings to three growth light intensities (100, 550 and 2000 μmol cm−2s−1) during development of the first and second growth flush. The low and high light intensities of PAR are supposed to mimic the effects of solar radiation under extreme natural conditions (closed canopy and open field). The response of seedlings to different light intensities was evaluated by determining the photochemical activity of photosystem II, leaf chlorophyll concentration and epidermal flavonoid accumulation for both growth flushes. At the end of the experiment (after 4.5 months) the effects of different treatments on growth parameters were also determined. We showed here that oak seedlings responded to varying light intensities by modifying their physiological and morphological traits of successive growth flushes. At medium light, seedlings had the highest PSII photochemical activity in the 2nd flush. High light induced very low photochemical efficiency of photosystem II in both growth flushes indicating the development of high non-photochemical quenching of chlorophyll fluorescence as part of photoprotective mechanism. In accordance with high photosynthetic yield at ML, the investment of photosynthates in growth, especially biomass allocation towards root system was confirmed. ML was optimal for seedling development in the first months. The results may contribute to a better understanding of oak seedling development and acclimation and could have importance for oak natural regeneration.