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Abstract
Autumn coloration is a phenomenon that affects the green leaves of certain deciduous trees and shrubs by which they transform into a wide range of shades of colors. However, the perception of those phenomenological transactions is an important criterion for successful landscape design practices. This study deals with European cranberrybush (Viburnum opulus L.) phenology assessment at the scale of individual plants and describes our current understanding in terms of autumn coloration. To accomplish this objective, selected European cranberrybush was monitored, photographed and selected properties measured during peak time in autumn. The visually perceived colors of leaves in European cranberrybush have also been verified, using spectrophotometric (colorimetric) and chlophyll (SPAD number) measurements. The leaf senescence was visually revealed and 10 representative leave samples were ordered according to their appearance from green to deep red. The SPAD numbers of ordered leaves were found to be in the range from 31.40 (sample 1) to 8.38 (sample 10) which closely correlated with visual perceptions. The highest redness color value of a: 25.79 metric was found with sample 10, while all leaves showed only different shades of yellowness (+b values) rather than blueness (-b). The discolorations were also evident by hue angle (Hue, ho), which it continuously lowered from 1220 greenness-yellowness (sample 1) to 22.320 redness-yellowness in color circle (sample 10). However, a close relationship was found between SPAD and Lightness (L); SPAD and yellowness-blueness (b*) but an inverse relationship between SPAD and greenness-redness (a*) of leaves. The CIE tristimulus (XYZ) values show some variations and are not well consistent with SPAD.
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Abstract