We examined the patterns of pigment change during leaf senescence in woody plants at Harvard Forest, in Central Massachusetts. Seventy percent (62/89) of woody species anatomically examined accumulated anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in vacuoles of palisade parenchyma cells. Yellow coloration was due to the un-masking of xanthophyll pigments in senescing chloroplasts. In nine yellow- and nine red-senescing species: (1) anthocyanins were not detectable in mature leaves, and were synthesized de novo in senescence in red–senescing species, with less than 20 µg cm-2 of chlorophyll remaining; (2) xanthophyll concentrations declined in relationship to chlorophyll to the same extent in all species; (3) maximum photosystem II quantum yields of leaves collected prior to dawn were similar among all species; (4) the timing and order of leaf senescence among the 18 species was remarkably similar from year to year; (5) Red-leaved species had significantly greater mass/area, reduced % total nitrogen at maturity and in senescence, and lower chlorophyll a/b ratios during senescence. Anthocyanin production was reduced by shading but not affected by reduced red:far-red, and anthocyanic leaves did not increase leaf temperatures in two species. These results suggest a protective function of anthocyanins during senescence, allowing more nitrogen resorption back into woody tissues.

Key words: anatomy, anthocyanins, leaves, nutrient resorption, senescence, xanthophylls