Nature's Crayons

I promise this is the last post on plant pigments!  It's a short one, too.  I just want to take advantage of the last of the glorious fall colors. 

The first thing I noticed at the outdoor classroom this week is that the pond has turned brown.  The brown color is from tannins in the oak leaves that have fallen into the pond.  Our pond water has basically turned into oak tea.  The mosquitofish in the water don't seem to mind.  They are a very tolerant species.  High concentrations of tannins in water can alter the water chemistry, changing the types of organisms that can live in the water.  If we had fragile aquarium fish in our pond, we would want to change the water, but our organisms (fish and snails) are adapted to a wide variety of water conditions, including tannins.

Tannins from oak and maple leaves have turned the water brown.

The next thing I noticed at the classroom was leaves of every plant color you can think of.  See if you can name the pigments in the leaves from our classroom.  Here's a reminder of the plant pigments:

• Chlorophyll = green
• Tannins = brown
• Carotene = orange
• Xanthophyll = yellow
• Anthocyanins = red and purple

Xanthophyll in a maple leaf.

Tannins in a maple leaf.

Chlorophyll in magnolia leaves, xanthophyll in the leaf petioles.

Anthocyanins in sourwood leaves.

Chlorophyll and anthocyanins in oak leaf hydrangea leaves.

Anthocyanins, carotene and xanthophyll.

Anthocyanins, carotene and xanthophyll.

These pictures are just the tip of the iceberg.  When you walk through the outdoor classroom this week, see how many differently-colored leaves you can find.  Bring your fall Crayons if you like, and draw what you see.