Growth adaptability of Norway maple (Acer platanoides L.) to urban environment

Adaptability of <italic>Acer platanoides</italic> L. to deteriorating urban conditions was assessed through qualitative parameters describing crown destruction, assimilation organs efficiency, chlorophyll <italic>a</italic> content, and content of alochtonous elements in leaves. The adaptability assessment was based on comparison between study trees growing in an environmentally loaded town area and control trees in a historical rural park, both localities in Slovakia (Central Europe). The results of visual assessments performed in 2015 and 2016 showed higher crown and leaf quality ( <italic>Qns</italic> ) for the individuals growing in the rural park ( <italic>Qns</italic> ₂₀₁₅ = 0.44, <italic>Qns</italic> ₂₀₁₆ = 0.43) compared to the individuals in urban conditions ( <italic>Qns</italic> ₂₀₁₅ = 1.44, <italic>Qns</italic> ₂₀₁₆ = 1.56). The values of chlorophyll <italic>a</italic> content index ( <italic>CCI</italic> ) were higher in the trees growing in the rural park ( <italic>CCI</italic> = 25.914) than in the urban environment ( <italic>CCI</italic> = 16.290). The performance of assimilation organs was evaluated through the maximum fluorescence yield ( <italic>Fv/Fm</italic> ) and electron transport rate ( <italic>ETR</italic> ) at both sites. During the years 2015 and 2016, there were measured higher values in the rural park ( <italic>Fv/Fm</italic> ₂₀₁₅ = 0.828, <italic>Fv/Fm</italic> ₂₀₁₆ = 0.820) than in the town ( <italic>Fv/Fm</italic> ₂₀₁₅ = 0.823, <italic>Fv/Fm</italic> ₂₀₁₆ = 0.772). Higher <italic>ETR</italic> values were measured on trees in the urban area ( <italic>ETR</italic> ₂₀₁₅ = 47.345, <italic>ETR</italic> ₂₀₁₆ = 65.284) and lower in the park area ( <italic>ETR</italic> ₂₀₁₅ = 36.832, <italic>ETR</italic> ₂₀₁₆ = 59.495). The urban locality demonstrated higher contents of Cu, Zn, Fe, Pb, Na and Ca elements in tree leaves compared to the rural park. The adaptability index ( <italic>Ia</italic> ) values indicate an average adaptability of the Norway maple to the urban environment ( <italic>Ia</italic> ₂₀₁₅ = 1.93, <italic>Ia</italic> ₂₀₁₆ = 2.13) in comparison with a good adaptability in the rural park ( <italic>Ia</italic> = 0.8–1.6).