Abstract
Water represents one of the limiting environmental factors having impact on all the processes in plants. Water stress is considered as the most significant cause of photosynthesis defects. Measuring fluorescence of chlorophyll a is one of the methods revealing defects in the photosynthetic aparatus. The examination has been carried out on the plants Cornus stolonifera Michx. ´KELSEYI´ cultivated in two different irrigation regimes (a regime with 40% substrate saturation and a controlling regime with 60% substrate saturation). We have used a fluorometer HANSATECH FMS 1 to measure modulated fluorescence of chlorophyll a. A three-week period of measurement was set between June and August during two years of experiments (2011 and 2012). The selected chlorophyll fluorescence parameters Fv /Fm - maximum quantum efficiency of PSII; ΦPSII - effective quantum yield of PSII; Rfd - chlorophyll fluorescence decrease ratio and NPQ - non-photochemical chlorophyll fluorescence quenching, proved to be insensitive to given water deficit. Cornus stolonifera Michx. ´KELSEY´ appears to be a woody plant capable of water efficiency.