True Colors: Anthocyanins & Succulents
Let's face it. One of the reasons we love succulents so much is their color. They come in all sorts of colors and shapes, to fit moods, occasions, and styles. On this segment of Succulent Science Sunday, we will answer the question, what makes succulents colorful?
What causes color and why?
Anthocyanins. Anthocyanins are what make our succulents colorful!
Anthocyanin (etymology: Greek for "blue flower") is the colorful pigment found in plants. They make flowers orange, cherries red, and blueberries blue!
In more chemical terms, anthocyanins are the glucosides of anthocyanidins. Glucosides are glycosides of glucose (sugar). Glycosides are molecules that are derived from sugars (in this case, glucose is the sugar), and attach to a function group with a glycosidic bond. A glycosidic bond is when a sugar is attached via a covalent bond through carbon, nitrogen, sulfur, or oxygen, to another molecule which may be another carbohydrate. The anthocyanidin is basically an anthocyanin without the glucose (sugar). Different colors come from different kinds of anthocyanins. The R-groups in the generic anthocyanin below represent the variable that is different from the main molecular backbone. The R-groups are different depending on the particular anthocyanin.
In a study using the succulent Anacampseros rufescens (common names: rainbow sand rose, purple sand rose), scientists found that this South African succulent thrived in sunlight and died in shade (shade intolerant). At the highest level of sunlight, they found the highest anthocyanin concentrations, leading researchers to believe that anthocyanins act as photoprotection against too much sunlight. Sunlight is necessary for photosynthesis (see my post about photosynthesis), but too much photosynthesis can damage the plant. Similar to how melanin (dark pigment) in human skin can protect us from sun damage, plants produce more anthocyanins to protect them from over-photosynthesizing.
Above: Anacampseros rufescens
Yes. In fact, succulents can change color depending on the season, temperature, sunlight, and watering conditions, all variables that make up STRESS. I once bought a really nice purple pearl succulent with droopy leaves, a sign of underwatering. I took him home and wanted to pamper him, so I gave him lots of love and water. Imagine my surprise when the leaves perked right up like a sunburst and became 100% green. On a hunch, I googled "Can succulents change color?" and voila! Yes, they can. And it's completely normal. My advice: If you want that pretty, colorful plant at the shop, make sure you have plenty of sunlight to keep it that way, otherwise, expect a green plant in a week.
How can I keep my succulents colorful?
Stress = cold + sunlight + drought
Temperature: keep succulents a little colder (but above freezing!) than normal. This is hard to control, but winter can often do this.
Sunlight: give succulents tons of sun!
Water: keep your succulents dehydrated a little longer. A good watering will often make them revert back to boring old green and a nice juicy succulent can last a week or more without watering.
How the pH of the soil affects the color of Hydrangeas --> in a very organic science-y way. Post on pH and soil coming up in an upcoming post of Succulent Science Sunday!
Video via Youtube and ACS
Y.-C. Li, T.-C. Lin, C.E. Martin,
Leaf anthocyanin, photosynthetic light-use efficiency, and ecophysiology of the South African succulent Anacampseros rufescens (Anacampserotaceae), South African Journal of Botany, Volume 99, 2015, 122-128, http://www.sciencedirect.com/science/article/pii/S0254629915002604)