Photosynthetic efficiency of invasive species Amorpha fruticosa in Županja area (Croatia)

Amorpha fruticosa is invasive alien species deliberately introduced to Europe from North America, primarily to prevent soil erosion. It is often planted for decoration and for honey production. Due to its rapid growth and reproduction as well as its allelopatic activity that negatively affect nearby vegetation, uncontrolled expansion represents significant threat to native species. The aim of this study was to examine the influence of seasonal changes of environmental factors, such as temperature, light intensity or water availability on photosynthetic efficiency of A. fruticosa and accompanying woody species (Populus alba or Cornus sanguinea). Therefore, photosynthetic performance was analysed by measuring direct chlorophyll fluorescence twice during vegetation season, in May and July. A. fruticosa seedlings grows in the wide area of the city Županja (Croatia) in stands of varying size and age. For this investigation, three locations (sites) were chosen that were about same size and age. All results were compared to ones measured in May. Our results showed that overall photosynthetic performance (PItotal) of A. fruticosa increased in July while both, P. alba and C. sanguinea revealed decline of the same parameter. The PItotal parameter indicate the integral functional activity of photosystem II (PSII), photosystem I (PSI), and intersystem electron transport chain. In addition, the quantum yields (QY), namely maximum QY of primary photochemistry (TR0/ABS), QY of electron transport (ET0/ABS) and QY for reduction of end electron acceptors at the PSI acceptor side (RE0/ABS) as well as efficiency that an electron moves further than primary electron acceptor QA− (ET0/TR0) increased in A. fruticosa in July at all three sites. At the same time, both accompanying species did not follow increase of those parameters. Therefore, our results suggested that invasive species A. fruticosa follows seasonal variation of environmental factors better than native species.