Effect of sunlight on phenolic compounds accumulation in coniferous plants

The effect of light conditions on the accumulation of phenolic compounds was investigated in the needles of one-year and two-year old shoots, collected from perennial specimens of common yew (Taxus baccata L.), American arborvitae (Thuja occidentalis L.) and common juniper (Juniperus communis L.), growing in an urban garden. The content of total phenols and flavones was partially related to the light requirement or light tolerance of conifer tree. In Taxus needles, a shade-loving species, higher accumulation of phenolic metabolites was observed under shaded condition (in two-year old shoots) and was linked with the growth intensity in spring. In Thuja and particularly in Juniperus, the level of phenolics was related to the insolation intensity, probably so as a part of the adaptation mechanism.