Assignment #1: Designing a plant to live in the Arctic.

Allow me to whine a bit more about the Evil Teletubby.  She tried to tell me that working in groups was fun and therefore she strongly suggested I choose a group for this project.  Okay, so I'm not really a group-oriented person, but I have no problem working in a group and I could have done it...if only she hadn't said something.  That just brought out the contrariness in me and I was determined to go it alone, which I did.  And I got stuck with the Arctic--I would have loved the rainforest or water or the plains, but no, I got the Arctic.  Still, it was a pleasant challenge, and anyway I got most of my ideas from the video she showed us in class, called The Sexual Lives of Plants or something like that.  It's quite good, actually.

I wish you could see the wonderful pictures I drew for this. I only boast about them because I am definitely not a drawer--I know a lot of people say that but I really mean it.  A stylized stick figure I've dubbed "Muscle Man" is about the limit of my artistry.  Granted, this assignment only called for leaves and flowers, but I had to use perspective and hard stuff like that. And it turned out very well, I think.  Perhaps when I get a scanner...they'll be at the top of the list, right after my drool-worthy pictures of a young Jerry Orbach.

Grade: 100% (...oh forget it, anything I say here will be horribly smug)

Glacialis sinus
Arctic Folding Plant

Glacialis sinus, or the Arctic folding plant (Fig. 1), is a small monocot flower commonly found in the tundra of the Northern Hemisphere, including northern Canada, western Alaska, northern Asia and Russia, and the coast of Greenland (there is no tundra in the Southern Hemisphere because no dry land lies in the proper latitudes). The Arctic folding plant is approximately four inches tall with a white flower, thin-bladed leaves, and a thin covering of protective hairs. It is an annual plant that germinates, grows quickly, flowers, sets seed, and dies during the brief tundra growing season. Its common name is the result of an unusual reproductive characteristic of the plant. The Latin name comes from the words glacialis, meaning "icy", and sinus, meaning "fold"; the mountain-top-growing Alpinis sinus, or mountain folding plant, though its name and appearance are similar, is merely an example of convergent evolution and is not actually related to Glacialis sinus.

The tundra is a cold environment with little precipitation and little vegetation most of the year. Its growing season is only about sixty days long, during the summer when the sun shines for twenty-four or nearly twenty-four hours a day. The rest of the year, sunlight can dwindle down to less than an hour a day. A layer of permafrost--permanently frozen soil--rests a few inches under the topsoil, preventing adequate water absorption. As a result, during the summer the top few inches of soil are swampy and poorly drained with few nutrients that are essential to plant growth, such as nitrogen, phosphorus, and potassium. The tundra is also very windy. During the growing season, many other plants such as mosses, lichens, grasses, sedges, and dwarf trees bloom and compete for resources such as nitrogen and other nutrients, available water, and access to sunlight. Although there are comparatively few different species of plants in the tundra, there are a great many individual plants. Swarms of insects buzz across the tundra during the summer, to be eaten by the seasonal flocks of birds. Large animals like caribou migrate into the tundra to graze while some smaller ground animals like lemmings, weasels, foxes, snowshoe hares, and snowy owls live in the tundra all year long. The tundra is a delicate environment that is easily disturbed by humans, who can do irreparable damage merely by hiking through it, collecting a few plants, or, most dangerously, drilling for oil.

The Arctic folding plant is designed to withstand the many disadvantages of the tundra. Its leaves and petals are specially shaped to take advantage of the sunlight without losing too much water, and it is covered with a thin layer of hair to insulate the plant against the cold and to help reduce the wind. Its C4 photosynthesis pathway makes the most efficient use of the sunlight while its root system is able to gather water and nutrients without putting the plant in danger of drowning. Once all these growing resources have been put to use in creating a seed-filled fruit, the plant dies but continues to protect its offspring through the winter with its remains. In the summer, the seeds quickly disperse and begin growing to start the process all over.

The white petals of the folding plant are shaped like parabolas to reflect sunlight into the center of the flower, where the stamens and pistil lie (Fig. 2). This focused warmth, as well as the large amount of pollen available from the many stamens, attracts insects such as flies (Fig. 3) which need the pollen for food and warmth from sunlight in order to fly (Kearns and Inouye 1993). Both items are hard to find in the chilly tundra, and many flies might not survive if not for the flower centers they can land on for "refueling." These insects crawl over the center of the flower, transferring pollen from other plants onto the pistil, and picking up pollen to take to other flowers. The new pollen sticks to the stigma of the pistil where a pollen tube grows down the style and into the ovary, transferring the sperm to the ovules. After fertilization, the ovary swells with the multiple seeds and becomes the fruit (Fig. 4), with the shriveled stigma and style usually still attached at the top. Having completed its one-year life cycle, the plant's stem begins to whither and shrink and the fruit slowly sinks or falls to the ground. The leaves of the plant fold around the thick-walled fruit to offer more protection against the fierce winter to come (Fig. 4c), giving the plant its common name. The fruit generally stays in the same area as its parent plant all winter, having no adult plant to compete with for resources in the future; however, on occasion, high winds and curious animals have been known to transport the generally inedible folding plant fruit long distances. When the sun begins to shine longer and longer in the sky again and the tundra summer has begun, the seeds swell with water uptake and burst out of the fruit, showering themselves over a radius of up to two feet. Like most plants, the Arctic folding plant is capable of asexual reproduction from leaf or stem cuttings, but this method is rarely employed in nature; plants that do not grow quickly from the start of the summer will usually not have enough energy to reproduce by the season's end, and the lack of nutrients in the soil makes it difficult to support large populations in small areas. Asexual reproduction of the Arctic folding plant, specifically leaf cuttings rooted in standing water, is the method preferred by botanists and other plant scientists when studying Glacialis sinus specimens in the laboratory; as one might deduce from the earlier description, the folding plant's fruit requires a long, very cold period before the seeds become viable, which is inconvenient and time-consuming in a research situation.

Although the partially-melted tundra of the summer is boggy with standing water, its cold winds strip moisture from the creatures they blow across, and the folding plant's leaves must work to conserve as much water as possible. The plant's stomata not only let gases such as carbon dioxide and water vapor in for use in photosynthesis, but they also let gases out as waste products. In an environment with poor drainage and drying winds, such water loss can be deadly to a plant, so the leaves of the folding plant have fewer stomata on the upper surface than on the lower, and the stomata remain closed at night to reduce transpiration. The leaves are also narrow and covered with a thin layer of hair that slows the wind across them (Fig. 5, 7). The folding plant uses C4 photosynthesis to make more efficient use of the limited amount of sunlight available to it (Fig.6). In C4 photosynthesis, the plant transforms carbon dioxide into a three-carbon molecule, then a four-carbon, using the enzyme PEP carboxylase. This four-carbon molecule is then transferred from the mesophyll cells into the bundle-sheath cells, where it's split into a three-carbon molecule that goes back to the mesophyll and a carbon dioxide molecule that continues on to the Calvin Cycle. This method of photosynthesis reduces the need for the enzyme Rubisco, which occasionally screws up and adds an oxygen to RuBP instead of a carbon, resulting in useless carbon dioxide molecules and the wasteful process of photorespiration. In the Arctic, the folding plant can't afford to waste its precious resources on mistakes. The thin, hairy leaves also tend to make the folding plant unappetizing to the herds of caribou and other large animals that migrate to the Arctic to graze, especially with so many other more appealing choices available at this time of year.

The stem of the plant (Fig. 8) is fairly short; there are too few resources for many plants over a foot tall to grow here. It is also flexible, allowing the plant to bend in the fierce wind without breaking, and it performs some photosynthesis. It supports the flower and the leaves, holding them up so they can receive sunlight, be pollinated, and produce food for the plant. The stem is also covered with protective hairs to reduce water loss and help insulate the plant. As a monocot, the plant's vascular bundles are scattered throughout the cortex with the phloem on the outside and the xylem inside (Fig. 9). The vascular bundles transport food and water up from the fibrous root system, which gathers the nutrients such as nitrogen, phosphorus, and potassium from the soil with tiny root hairs (Fig. 10, 11). The roots have their own xylem and phloem, located in a ring inside the stele of the root. The roots of almost all tundra plants must be fibrous; not only would a taprooted plant most likely drown in the poorly-draining soil, it also would not be able to reach very far beneath the surface before it encountered the always-frozen layer of permafrost.

The C4 pathway of the Arctic folding plant's photosynthesis helps it to make efficient use of Arctic sunlight while its narrow, hairy leaves and stem reduce water loss and insulate the plant in the face of the driving wind. The specially colored and shaped petals of the flower focus the sunlight and attract pollinators, and once a fruit has grown, the plant uses its dying leaves to protect it during the long winter. Its fibrous root system draws water and nutrients from the swampy soil without drowning the plant, and a quick dispersal of the seeds the next year allows the plant to grow and flower quickly. The Arctic folding plant, or Glacialis sinus, is very well suited to the harsh, unforgiving environment of the tundra.

References

Berg, L. R. 1997. Introductory Botany: Plants, People, and the Environment. pp. 452, Saunders College Publishing, Orlando

Kearns, C. and D. Inouye. Apr 1993. Pistil-packing flies. Natural History Magazine: 34

University of Toronto at Scarborough. Lecture 44: world biomes. [Online] Available http:citd.scar.utoronto.ca/BGYB50/lec44.htm, April 19, 1999