Plant Senescence (Autumn Colors)

We think they are turning colors, but what is really happening is that the chlorophyll that makes them green begins to recede, whilst the leaf base develops a "cork layer" that closes its venous system and gradually disconnects it from the tree.  The color you see is the tree's natural leaf color, minus the chlorophyll that masks it during the growing season and helps to nourish the tree.  The saturated colors create a bittersweet mood for me, a confusion of excitement, anticipation and nostalgia.  They are so bright on a cloudy day next to gray Puget Sound that they enter your eyes like sunshine, and scatter light in dreary places.