Anthocyanin influence on water proton NMR relaxation times and water contents in leaves of evergreen woody plants during the winter

An investigation was made to determine the effect of anthocyanin in red-colored evergreen leaves during the mid-winter on water proton NMR relaxation times (T₁). Water contents, anthocyanincontents and histologic localization of red-coloration in mesophylls were determined by using both red-colored and green leaves from the same branches of Rhododendron, Viburnum and Mahonia, respectively. Although the decrease of water contents in the red-colored leaves in Mahonia was insignificant, decreases in the former two species were clearly observable. T₁ differences between red-colored and green leaves for the three species were insignificant. Increases of anthocyanin contents and histologic localization of red coloration in mesophylls for the red-colored leaves were more pronounced in Rhododendron and Viburnum than in Mahonia. These observations suggest that the pronounced increases of histologic localization of red-colored mesophyll cells and anthocyanin contents in red-colored leaves for the former two species contribute to maintenance of T₁ relaxation times in spite of the marked decrease of water contents in leaves. It is assumed that the increase of localization areas of red-colored parenchymatous cells in mesophylls is more effective than the total contents of anthocyanins in leaves towards the maintenance of the T₁ level in red-colored leaves, and this appears to be dependent on the vacuolar compartmentation of anthocyanin in mesophyll cells.