Temporal Changes in the Leaf Pigments of Acer platanoides, Cornus florida, and Ulmus parvifolia Through the Growing Season from Budding to Senescence

Abstract:

The color of leaves change throughout the year, especially in the season of autumn as the plant manufactures different pigments and the amount of the pigments vary over time. To the human eye, chlorophyll, makes leaves look green or yellow, carotenoids make leaves look orange. Anthocyanins, make leaves look red. As the year goes on and the seasons change, leaves lose their chlorophyll and carotenoids however some of the carotenoids remain which give autumn leaves an orange-yellow color. Leaves lose chlorophyll all throughout their growing season but the loss increases heading into fall which is why the change in color is so rapid in autumn. Anthocyanins also contribute to the rapid change in color. Anthocyanins are only produced in the late summer or before the leaves begin to fall which is also when more chlorophyll is lost. The amount of different pigments left in the leaves result in the color that the leaves appear to the human eye. Depending on the amount of carotenoids and chlorophyll in the leaves, the anthocyanins with the other pigments create orange, brown, and red hues. For this project, three different tree species were chosen: a Dogwood tree, a Japanese Elm and a Maple tree. Every week from when the trees produced flowers in March through October, three leaves were taken from each tree and the pigments were analyzed using a Vernier SpectroVis Spectrometer. The absorption graphs are compared over time to see the differences in pigments throughout the year.