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Foliar colour as an indicator of foliar chlorophyll and nitrogen concentration and growth in Norway spruce seedlings

Abstract The usability of foliar colour as an indirect means of determining foliar chlorophyll (Chlo) and nitrogen (N) concentrations was tested with second year Norway spruce seedlings transplanted into potted sandy soil in a greenhouse. The seedlings received four different N-fertilization solutions (0, 2.5, 25 or 125 mg l−1 N) and were grown until budset. Foliar colour became lighter towards the end of the experiment, when it was darkest green in the two heaviest N treatments. The relations of Munsell hue, value and chroma to foliar Chlo were curvilinear and showed high coefficients of determination (R 2=0.78–0.81). The respective relations to foliar N concentration were similar but slightly less significant. Chlo was also closely related to N concentration (when N < 1.2%). Foliar colour failed to indicate any difference in seedling shoot or root growth. The results suggest that foliar colour can be used for assessing foliar Chlo and N concentrations in tree seedlings, provided that the effects of seedling and needle age, seasonal variation and nutrition are taken into account.