Art Of The Day
On This Day in 1842, this illustration was published in French satirical journal La Charivari.
Lithograph, 9 3/4 x7 3/4 in. (24.77 x19.69 cm)
Gift of Owen and Leone Elliott, 1967.169
The flaming maples and golden ginkgos near the UIMA office have finally lost most of their leaves, and our view is starting to more closely resemble this oil painting by Linn Culberston, instructor of graphic arts at Iowa State University in the early 20th century.
Rendered in muted mauves and misty greens, this painting feels like a wet autumn day. What determines the vibrancy of fall foliage? Chlorophyll is the key. This green pigment is found in the cyanobacteria and and chloroplasts of algae and plants. During the warm and sunny growing season, chlorophyll is constantly replaced in leaves. However, much like wallpaper and newsprint, chlorophyll eventually breaks down after prolonged exposure to sunlight. As plants begin to prepare for winter, leaves gradually receive less nutrients from the rest of the plant, and chlorophyll is not replaced as frequently - you can think of this process (called senescence) as a kind of plant hunger strike until lovely spring weather returns! Chlorophyll masks yellow xanthophylls and orange carotenoids. As chlorophyll’s presence wanes, these other pigments become much more visible.
What about the brilliant red of sugar maples and sumac leaves? Reds and purples are produced by anthocyanins. These pigments, unlike chlorophylls or xanthopylls, are not present in leaves during the growing season. Rather, anthocyanins are manufactured by sugars still trapped in the leaves after chlorophyll production has ceased.
Finally, as frost conquers the land, even these straggling pigments succumb to the cold, leaving only tannins, which cause leaves to appear brown.
Oil on canvas, 27 x 36 in. (68.58 x 91.44 cm)
University acquisition, X1968.86