Friday, April 16, 2010

Plight of the Dandelion

"A weed is simply a plant that wants to grow where people want something else. In blaming nature, people mistake the culprit. Weeds are people's idea, not nature's." ~Anonymous

Imagine you were a cyanobacteria floating around in the sea billions of years ago. Eventually, you developed into algae. As an algae, you then slowly evolved into a marine plant.

Then, 475 million years ago, you evolved the capacity to live on land. That was a challenging transition to make. You had to overcome dessication and develop structural support against gravity (which is why you probably started out as a bryophyte, like moss). But hey, it was totally worth it. After all, the new frontier was so spacious! The sunlight was unfiltered by water and plankton, the atmopshere had an abundance of CO2, the soil was rich in mineral nutrients, and there were few herbivores and pathogens to threaten your new terrestrial lifestyle. This was prime real estate.

You eventually developed vascular tissue, seeds, and stomata for gas exchange with the environment. You even discovered a way to transport nutrients throughout your body without a pumping heart. Good for you! 140 million years ago, you finally developed into an angiosperm (flowering plant). (*1 : my notes from Dr. Bill Cohen, professor of BIO 152 at the University of Kentucky).

At last, you evolve into a Taraxacum officinale, a common dandelion...only then to be considered a weed and sprayed with pesticide. Your arduous journey has come to an end.

Ever wonder why dandelions are considered to be weeds to begin with? What is a weed? offers this definition: "a valueless plant growing wild, esp. one that grows on cultivated ground to the exclusion or injury of the desired crop." But dandelions actually have a lot of values, for humans as well as the ecosystem. Somehow they've gotten a bad reputation over the years, but there's probably a lot about this little flower that most people don't know.

Dandelions are all females. I know traditionally we don't consider plants to have gender, but it's true. Some plants have an ovary, some have sperm, and some plant types have both. Pollen is a type of plant sperm. Pollination (or fertilization) of plants is aided by wind, insects, animals, and water.

But dandelions are asexual. They reproduce through apomixis, meaning that seeds develop without fertilization. There are some asexual animals as well; mostly invertebrates, but also some reptiles. The whiptail lizard, for example, is a completely female species (though for animals it's referred to as parthenogenesis, instead of apomixis). (*2) This creates very limited variability within the species, meaning that all dandelions are genetic clones of the previous generations.

Dandelion, the name, originates from Old French, "dent-de-lion", meaning lion's tooth. The name comes from the jagged edges of the leaves of the plant, not from the flower. (*3)

The entire plant body of the dandelion is edible. "A serving of uncooked dandelion leaves contains 280 percent of an adult's daily requirement of beta carotene as well as more than half the requirement of vitamin C." (*4) And it's a "rich source of vitamins A, B, C, and D, as well as minerals such as iron, potassium, and zinc. It's leaves are often used to add flavor to salads, sandwiches, and teas. The roots can be found in some coffee substitutes, and the flowers are used to make certain wines." (*5)

Dandelions have also been used for medical remedies by Native Americans, Chinese, Europeans, and Middle Easterners. They are most commonly used for digestive aids and liver problems, but have also been used to treat skin conditions, heartburn, and upset stomach. (*4) In fact, the name Taraxacum officinale literally means "official remedy for disorders."

So the next time you see a dandelion disrupting the harmony of your perfectly manicured lawn, try to look past the weed and appreciate the wildflower.

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