EFFECT OF ARTIFICIAL LIGHT AT NIGHT (ALAN) IN URBAN CONDITIONS ON Taxus baccata L. LEAF MORPHOLOGY, PHOTOSYNTHETIC CAPACITY AND ASSIMILATORY PIGMENTS CONTENT

Light is one of the main factors that influences the greatest phenomenon of nature, namely photosynthesis. In modern society, excessive artificial light at night (ALAN) in the conditions of the urban environment can be considered as an external polluting factor as well. The purpose of this study carried out on Taxus baccata L. (1-year old leaves - PYL and the current year - CYL ones) grown as a hedge in urban conditions was to explore the effects of ALAN on leaves morphology, gas exchanges and associated indicators, as well as on assimilatoty pigments content. The results showed that: (1) The leaves length (LL)(mm) of CYL, as well as surface area (cm(2)) and leaf length to width ratio (LL/LW) were significantly lower under ALAN, than in normal (day/night cycle) light (NL). For PYL, no significant differences were noticed in the case of LL, while significantly lower values have been registered in the case of LW and leaf area to leaf fresh weight (AFWR); (2) Net photosynthesis (A) had significantly higher values during the springtime for PYL in NL as against ALAN, but opposite data have been noticed in June. The quantum yield (phi CO2), water use efficiency (WUE) as well as transpiration rate (T) and stomatal conductance (g(s)) proved to be affected by the light conditions. (3) The values for the content of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll (TC) and carotenoids (C) were generally as that known for plants in general, with a higher amount of Chl a for PYL-ALAN, as compared to those for CYL-ALAN, or CYL-NL. Further research should be applied by the scientific community to monitor the impact o f different light systems during the night and counteract the ALAN impact on plants and ecosystem.