Study Guide

Plant Biology In the Real World

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  • Health

    Harry Potter’s friend Neville Longbottom is smart to study Herbology, because plants are really useful: most of our medicines come from plants. At least until scientists figure out how to synthesize plant compounds in a lab. In the US, 40% of the medicines we use were originally found in plants; worldwide, where more cultures use traditional medicines, that number is 80%.

    Some plant parts have useful medicinal properties as soon as you pick them off the plant—the over-the-counter medicines, so to speak. If you get sunburned or burned from a hot stove, you can pick an aloe leaf and rub it on the burn for some instant relief. If you have bad breath or an upset stomach, you can grab a mint leaf and chew on that. Of course you buy aloe lotion in a bottle too, if you aren’t so keen on picking it off the plant.

    Other plants need a little more processing to release their medicinal properties, like medicines that need to be filled at a pharmacy. Taxol, an anti-cancer drug, was originally found in the bark of the yew tree (genus Taxus); now scientists can make it in a lab. The nasal decongestant pseudoephedrine, more commonly known as Sudafed, is modeled on the plants in the genus Ephedra. Interestingly enough, Ephedra plants were used by Mormons traveling west through the desert to make herbal tea because they didn’t want to drink caffeine. They didn’t know that it was full of ephedrine, which is a stimulant!

    Digoxin, a drug used for congestive heart failure or irregular heart rhythm, was isolated from the common foxglove, Digitalis purpurea. Concoctions of foxglove were used to treat heart problems as early as the 1700s. In addition to being useful for heart issues, foxglove makes beautiful flowers! Digitalis purpurea and other members of its genus produce cardioactive glycosides (a steroid molecule attached to a sugar molecule) in their leaves; these compounds slow heart rate and increase the amount of blood pumped in each beat. This improves circulation and improves the edema associated with congestive heart failure.

    Aspirin, one of the most popular drugs in use today, relieves fever and pain and owes its origins to a willow tree (Salix spp.). Many different cultures, including ancient Greeks and Native Americans, valued willow bark for its healing power. It took about a hundred years of experimentation, but finally in 1828, the active compound was isolated from willow bark. This isolated compound was called salicin, and is chemically related to salicylic acid. Salicylic acid became the new inexpensive treatment for many ailments, but chemists kept searching for another drug that was easier on the stomach. Salicylic acid is still used today for skin irritants such as acne, and its cousin acetylsalicylic acid was made into aspirin.

    A few more plant remedies you may have heard of include gingko, ginseng, and ginger. If your parents are getting old and blaming their occasional lapses of memory on their age, have them try some Gingko biloba pills for their memory. These pills contain extracts from ginkgo leaves, which may increase attention span in older people. Another plant starting with a G, Ginseng, has long been used as an energy booster in Chinese culture. Lately ginseng has been making its way into American products, such as Pepsi Max. Speaking of soda, everyone knows ginger ale is good for an upset stomach. The ginger we eat and use for medicinal purposes is the rhizome (part of the shoot system that grows underground) of the ginger plant, Zingiber officinale.

  • Pop Culture

    Art and Literature

    "Sublime nature" is a strong theme in Romantic era art and literature. Plants and the wilderness they create were particularly exalted during this period. 

    The Romantic era, in the late 18th century to mid 19th century, glorified nature and many Romantic books, poems, and artwork paid homage to sublime nature. The Romantic Movement, after all, was a response to the rationalization and institutionalized thinking that characterized the Industrial Revolution and the Age of Enlightenment. To Romantic thinkers, nature and its wildness represented freedom from the strict social and political norms of the day.

    One of the great Romantic painters, John Constable, painted many landscapes where trees played a large role. Though his paintings were not highly popular at the time, since they depicted an orderly natural setting as opposed to wild scenes, they show a respect and reverence for the local flora. The Cornfield, The Hay Wain, and Salisbury Cathedral from the Meadows all depict large, imposing trees that are integral pieces of the scene. In the Voyage of Life series, Thomas Cole portrays Childhood and Youth as places with lush vegetation, full of bliss and innocence. In Manhood and Old Age, the trees have died or disappeared; wilderness is supposed to be dangerous and untamed. Caspar David Friedrich presented many wild scenes in his landscape paintings, which he hoped would help provoke emotional responses to the natural world. Friedrich depicted not only beauty in his natural scenes, but barren trees and stumps, symbolizing death and the spiritual self.

    Impressionism in the 19th century also emphasized nature and all its lovely plants. Monet’s famous Haystacks series, have as their subjects, stacks of dried plant material. These haystacks were actually piles of harvested wheat covered by hay, which protected the wheat until it could be processed.

    If you look at one of Monet’s haystacks from a biological perspective, there is a lot more going on than meets the eye. That is not just a pile of wheat and hay; that is a pile of grasses. Grasses, being monocots, have shallow root systems, parallel veination and floral parts in multiples of threes. Some of the dried grasses in that haystack probably have seeds still attached to them. While the wheat sits in the field waiting to be processed, some of the seeds might start germinating. Or some seeds might even disperse. The descendants of the grasses that ended up in Monet’s haystacks might even still be alive today. 

    Of course, Monet also painted lots of gardens, and poppy fields, and tulips, and roses. And we all know that those showy flowers are just wheedling their way into pollinator’s good graces so they get their pollen transferred.

    Paul Cézanne, another Impressionist painter, featured lots of trees in his work. If only he had Shmoop to tell him that the trees in Jas de Bouffan lost their leaves because they went dormant for the winter. 

    Cézanne painted a series of still lifes focusing on colorful fruits. As we know, plants have duped us into eating the fruit and spitting out those precious seeds, dispersing plant genes all around the world.

    Visual artists aren’t the only ones who appreciate plants. Many writers draw their inspiration from plant form and function.
    In "Tintern Abbey," William Wordsworth notices the "orchard-tufts…with their unripe fruits" but you’ve got a one-up on Wordsworth. You know that ethylene hasn’t yet been released to ripen those fruits, and that they have triploid endosperms. Wordsworth exalts the woods and describes himself as a worshipper of nature. In the meadow and woods, plants are all around him, and he’s loving it.

    In his poem, "The Lime Bower my Prison," Samuel Taylor Coleridge is forced to stay behind while his friends go out on a hike. However, Coleridge finds solace in the beautiful greenery surrounding him. He notes a walnut tree, elms and ivy, and even observes a bee pollinating a flower. Coleridge got to see nature in action without even leaving his front door. Sometimes plants can surprise us; a tree may burst into flower overnight, or it suddenly becomes autumn when red, orange and yellow leaves fill up the streets and lawns.

    Look for leaves, seeds, buds, moss, and flowers in Percy Bysshe Shelley’s "Ode to the West Wind," even though the poem is really about the poet’s capacity to share his ideas throughout the world. Like the seeds and decaying leaves, the narrator hopes the wind will pick him up and spread his thoughts. Just as dispersing seeds of a plant may change the species composition of the ecological community the seeds reach, spreading new ideas may change the social or political atmosphere of the human community new ideas reach.
    Now that we’ve convinced ourselves that the Romantic poets really did love plant biology, let’s move on. Guess what? Modern poets love nature too! What a coincidence. Ted Hughes’ poem "Big Poppy" is all about one flower, and Seamus Heaney’s " Blackberry Picking" is (spoiler alert) about blackberries. This illustrates plants’ unique hold on us humans—they lure us in, and once we’re snared, they won’t let us go. Since humans rely on plants for food, fuel, medicines, and beauty, the least we can do is write a few poems about them.

  • Agriculture

    Farmers have been selectively breeding plants for thousands of years. Let’s look at the process of breeding and growing some of the plants we eat regularly (e.g. corn, bananas, potatoes) from a biological perspective.

    With all the uproar about genetically modified organisms, people tend to forget an important fact: humans have been modifying plant genomes for thousands of years. Just like dogs have been bred to look and behave differently from their wolf cousins, most of the plants we eat are very different from their wild relatives. Wild cucumbers are round and spiky, wild rice is black and gray, and the wild form of corn, teosinte, isn’t even edible. So how did we get to the point where we have big juicy fruits and vegetables, and nutritious grains that can be harvested and turned into wheat, corn and rice products?
    About 10,000 years ago, our ancestors started taming wild plants and created the first farming societies. Since then, various human societies have been refining wild plants to make them more delicious, more nutritious, or easier to harvest and process. Plant breeders have done this by exploiting natural variation in plants. Suppose you had some corn, but you wanted bigger corncobs. You might take the seeds from the plant that produced the biggest ear of corn and plant those seeds exclusively for the next year’s crop. The resulting corncobs should be bigger, on average, than the first crop. Then next year you would plant the seeds from the plants that produced the biggest corncobs, and so on, selecting the plants that produce the biggest corncobs each year. For this to succeed the variation has to be heritable, which means it is passed on through genes; luckily for us and the Neolithic farmers who domesticated corn this way, the variation is heritable.

    Humans have fiddled with lots of plants this way, though not necessarily always for size of corncobs. Some plants have come into being by mating two different species or strands. Bananas are a prime example of this, as are many orchid varieties. The bananas we eat actually have a triploid genome (3N), meaning they have three sets of each chromosome. They got that way through a cross between a diploid (2N) and a tetraploid (4N) banana species. The triploid genome makes bananas sterile, so they can only be propagated through cuttings.

    Speaking of bananas, remember how bananas are good at producing ethylene and helping other fruits ripen? In large agricultural productions, farmers and fruit distributors control ethylene so that they have ripe fruit when they want it. Some fruits, like apples, are stored in containers that have higher than normal carbon dioxide. The reason for this is that carbon dioxide inhibits ethylene production, keeping the fruits immature indefinitely. When it is time to take the fruits to market, the fruits can be moved to containers with increased ethylene to speed up the ripening process. Unfortunately, too much ethylene can overripen fruit. Don’t forget the importance of other hormones either: gibberellins make grapes big and juicy, and can induce flowering of long day plants.

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