My friends at Birches have been making keen observations about many of the different trees that surround their school. They noticed that the trees around campus hold leaves with a considerable variety of identifiable features. A couple weeks ago, friends selected an assortment of leaves and decided to categorize them based on size and features, such as leaf outline shape. They also made leaf drawings and wrote highly creative stories about each leaf they chose. On a nature walk, friends noted that many of the trees' bark have quite different textures, and that some trees keep their thick bark covering while others have thin bark that is peeled away. Theories about why certain species undergo seasonal shedding is a topic we will likely return to at another time this winter.
We decided to collect leaves from 5-8 of these different tree species and to use a field guide to make tree species identifications. Since we have been talking about seasons and the weather changes that come with fall, friends were interested in making predictions about the leaf colors that they expect to see and in discussing why some leaves change color during autumn time.
Our friends wondered what makes certain leaves turn from green to bright warm colors in the fall, and why some tree leaves turn brown, while others turn yellow or red and orange. We decided to test what color we would find if we closely analyzed the green leaves that we had collected.
Using paper chromatography, we carefully rubbed leaf pigments onto a piece of special filter paper in a thin dark green line. Then we submerged the paper strip into a small glass flask with a tiny volume of ethanol (solvent). When our paper began to soak up the liquid, friends noticed that the green pigments began crawling up the strip as it was carried by the solvent. We were pleasantly surprised to see that, on some of our leaf rubbings, we were able to see other colors appear! Over the autumn, friends plan to observe the trees from which they collected their leaves, and to see if the color predictions we made based on the chromatography experiment come true.