Friday, June 14, 2013

The Color Purple

I ask myself weird questions sometimes. In spring, I wonder why the early bloomers are mostly white. Now that summer has arrived, more of our flowers in the garden are purple...sort of.

Dick planted all these, so I don't know the names of many of them, but I always think of them as  "purple." Or I did until I started putting this blog post together. As I worked with the photos, suddenly I wasn't so confident about their color. Well, let's see what Google can find.

Purple is a range of hues of color occurring between red and blue. The Oxford English Dictionary describes it as a deep, rich shade between crimson and violet. In the traditional color wheel used by painters, violet and purple are both placed between red and blue. Purple occupies the space closer to red, between crimson and violet. Violet is closer to blue, and is usually less intense and bright than purple. While the two colors look similar, from the point of view of optics there are important differences. Violet is a spectral, or real color – it occupies its own place at the end of the spectrum of light, and it has its own wavelength (approximately 380–420 nm). It was one of the colors of the spectrum first identified by Isaac Newton in 1672, whereas purple is simply a combination of two colors, red and blue. There is no such thing as the "wavelength of purple light"; it only exists as a combination. Pure violet cannot be accurately reproduced by the Red-Green-Blue (RGB) color system, the method used to create colors on a television screen or computer display. It is approximated by mixing blue light at high intensity with less intense red light on a black screen. No wonder these flowers keep looking different on the computer!

Simply put, flowers are colorful for one main purpose, survival. Flowers are the reproductive systems of plants and are therefore responsible for assuring that the plants can survive from one generation to another. Their bright and varied colors help make reproduction and survival possible in several ways. One way is by attracting insects that carry pollen from one flower to another allowing the reproduction process to continue through the creation of fruits and fertile seeds. The color of flowers, such as the red in roses and yellow in marigolds, are found in pigments that are decided upon in the hereditary genome of the plant. Flower colors of red, pink, blue and purple come mainly from the pigments called anthocyanins, which are in the class of chemicals called flavanoids (what gives plants their color). One study says that purple flowers have more nectar.

But flowers may not "actually" change color, rather the "perception" may change. This can vary with people--men tend to see primary colors such as blue or green, women more distinctions such as turquoise or chartreuse. Perceptions among genders is actually related to differences in genetic eye anatomy. Perceptions may also vary with light conditions. Seeing flowers in the warm (reds) light of morning or late evening will give them a different appearance than in midday, or on a cloudy day compared to a sunny day, or under the green light of trees compared to the blue light of open sky. Since the color we see is actually the color of light reflected off the petal or plant surface, anything that can change this reflected light, will change our perception of the color.  
 Flowers which appear to have one color to humans in full spectrum light, may show different colors and patterns in ultraviolet light, which we can't see, but many pollinators can.
Some bee flowers tend to be yellow or blue, often with ultraviolet nectar guides and scent. Nectar, pollen, or both are offered as rewards in varying amounts. The sugar in the nectar tends to be sucrose-dominated. There are diverse types of bees, however. Honeybees, bumblebees, orchid bees, etc. are large groups that are quite distinctive in size, tongue length and behavior (some solitary, some colonial). Thus generalization about bees is difficult. Some plants can only be pollinated by bees because their anthers release pollen internally, and it must be shaken out by buzz pollination (also known as "sonication"). Bees are the only animals that perform this behavior. Bumblebees sonicate, but honeybees do not.

After all this "scientific" investigation, I think I've come up with the real answer. When I was a kid, I only got to have a box of 24 Crayola crayons. I know there are many shades and names for "purple," but they weren't in my crayon box, so I never learned them!

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