Every springtime, a stunning orange field of California poppies, Eschscholzia californica, is impossible to ignore. But now and then it is not unusual to encounter an individual poppy plant that seems to rebel by refusing to conform to the crowd. Instead of orange, it is pure white, or at least a paler hue of orange. What’s going on here? Is it a different kind of poppy, and if so, how did it manage to find its company among all the others?
The answer is a matter of simple genetics. Flowers, like other living things, are made up of units called cells. Cells contain the hereditary material, DNA for short, which contains the chemical blueprint needed to manufacture new cells. Every cell in the plant has the same DNA, including the ovules (the female cells) deep inside the flower, and the pollen grains (the male cells), located in the stigma of the flower or often in a different flower of the same type. A new flower begins when an ovule is fertilized by a pollen grain (produced by the stamen) that lands on the stigma (either by an insect pollinator, the wind or another mechanism), and a seed is formed. The seed potentially grows into the adult plant, according to the blueprint instructions encoded in the plant’s DNA.
But sometimes a mistake occurs in following the blueprint. Some mistakes can be fatal to the plant, or to any organism where the mistake occurs. But often they result in variations called genetic mutations. A genetic mutation is a change in the DNA blueprint that produces something different. Genetic variations are important for organisms to evolve, and are responsible for the evolution of all living things over time.
The orange color of poppies is due to a pigment, called a carotenoid, which the DNA of the plant is programmed to make. But if an error, or mutation, occurs that disables the function of the gene that controls the production of the carotenoid pigment, the plant is left to produce a flower without the orange pigment — in other words, the resulting flower is white!
That’s not all! Poppies contain two copies of the carotenoid gene, one from the female ovule and one from the male pollen nucleus. Those with two mutant copies are produce white flowers, and those with one normal and one mutant are yellow, or a lighter hue of orange.
Much of the credit for figuring this out goes to Jonathan Pollack, a professor of pathology at Stanford University, and to his son, Andrew Pollack, a student at Stanford. Andrew was exploring bioinformatics at the time as a computer science major, and we thought, ‘You know, I bet we could figure this out.’”
“The scientist does not study nature because it is useful. He studies it because he takes pleasure in it, and he takes pleasure in it because it is beautiful.”
– Henri Poincaré, Science and Method, 1908
Guided Tours of the Granada Native Garden are Available!
Are you interested in learning about some of the plants that are described in this Newsletter or in the archived issues? One or more staff of the GNG are routinely on duty at the Garden on Mondays and Tuesdays, roughly between 10:00 AM and 12:00 noon. But it isn’t hard to arrange a guided visit at other times. If you are interested in scheduling a visit, just email Jim at JIMatGNG@gmail.com . Or if you have any questions or inquiries, please email Jim at the same address! Directions to the Garden and information about volunteering there can be found by clicking one of the buttons at the top of the first page of this Newsletter.
Nice article on poppy color variations! I would love to visit the garden. Do you park in the apartment parking lot?
One can park across the street and J-walk over to the Garden, or one can park in the apartment lot if is only for a relatively short time, or one can drive around the fence and park in the Garden maintenance area, where I and my volunteers usually park.
Thanks Jim, I always enjoy your posts. Where I live now (mendocino county) we see blue-eyed grass with white flowers here and there. I imagine the science behind it is similar.