Marine Biology(Plant Life in Salt Marshes)
Narrator
Listen to part of a lecture in a marine biology class.
Professor
Ok, today we are going to continue our discussion of plant life in coastal salt marshes
5 of North America. Salt marshes are among the least inviting environments for plants. The water is salty, there is little shade and the ocean tide comes in and out, constantly flooding the marsh, so the variety of plants found in salt marshes is limited, but there is a plant genus that thrives there, the Spartina. In fact, the Spartina genus is the dominant plant found in salt marshes. You can find one type of the Spartina, Saltmarsh Cordgrass, growing in low marsh areas. In higher marsh areas, you are likely to find a Spartina commonly called Salt-meadow Hay. So how is the Spartina able to survive in an envrionment that would kill most plants? well, it is because salt marsh grasses have found ways to adapt to the conditions there.
First of all, they are able to withstand highly saline conditions. One really interesting adaptation is the ability to reverse the process of osmosis. Typically, the process of osmosis works... Well, when water moves through the wall of a plant cell, it will move from the side containing water with the lowest amount of salt into the side containing the highest amount of salt. so imagine what would happen if a typical plant suddenly found itself in salt water, the water contained in the plant cells, that is water with very little salt would be drawn out toward the seawater, water with a lot of salt. So you can see the fresh water contained in the plant will be removed and the plant will quickly lose all its water and dehydrate. But what about the Spartinas, well, they allow a certain amount of salt to enter their cells, bringing the salt content of the water within the plant, to a slightly higher concentration than that of the surrounding seawater. So instead of fresh water moving out of the plant cells, salt from the seawater enters, reverse osmosis, and this actually strengthens the cells.
Another adaptation to the salty environment is the ability to excrete excess salt back to the environment. That’s why you might see a Spartina shimmering in the sunlight. What’s reflecting the light is not salt from seawater that has evaporated, although that’s a good guess. But it is actually the salt that came from within the plant. Pretty cool, eh? You can really impress your friends and family with that little ? the next time you are in a salt marsh.
But coping with salt is not the only challenge for plants in the salt marsh. Soil there is dense and very low in oxygen, so Spartinas have air tubes, air enters through tiny openings on the leaves, the tubes provide direct pipe line for oxygen, carrying it down the leaves through the stems and into the roots, where it is needed. If you pull up a Spartina, you might even notice some reddish mud on some of the roots, this is caused by oxygen reacting with iron sulfide in the soil, and it produces iron oxide or rust.
Now, although the Spartinas have adapted several chemical and physical mechanisms that allow them to thrive in salt water and to feed oxygen to their roots. There is yet another aspect of the harsh environment that they have to adapt to, the force of tides and occasional violent storms. Wind and water are constantly crashing into these plants. So as you might have guessed, they have developed a means of solidly anchoring themselves into the soil. How? They have tough sort of underground stems called rhizome, rhizomes from one plant grow through the muddy soil and interlock with those of other nearby plants, the plants form a kind of colony, a community that will thrive and perish together. Because alone as single plants, they cannot survive.
Of course the plants in these colonies also need tough resilient stems above the soil, stems that can bent a lot but not break as water constantly crashes into them. So in addtion to the interlocking underground rhizomes, they have yet another adaptation, and it is ... well, we are back to reverse osmosis again, by adjusting the osmotic pressure so that the cells are always fully inflated, the plant is able to withstand great pressure befor snapping, so Spartinas may look like simple marsh grass, but they are really a wonder of chemistry, physics and structural engineering that allows them to survive and even thrive in an evironment in which most plants will wilt7 and die within hours.
Recommended Reading：
Salt Marsh Life
Life in New Hampshire Salt Marshes
Dynamics of the Salt Marsh
TPO 19 Lecture 4
Art History(Cecilia Beaux)
Narrator：
Listen to part of a discussion in an art history class.
Professor：All right, let’s continue our discussion of portrait artists(portraitist) and portraiture. Who remembers any of the important points we made last time? Sandra?
Student：Well, artists have done portraits of people for centuries, of famous people and regular people, and most portraits convey the artists’ personal vision, like their feelings and insights about a person.
Professor：Great, that’s a crucial point, and I’d like to explore that a little today. A great example of that, that vision in portraiture, is Cecilia Beaux. Cecilia Beaux was born in 1854, and after learning to paint and studying with several important artists of the time, Beaux became known as one of the best portrait painters in the United States. She was very successful. She even had portraits of the wife and children of Theodore Roosevelt, while he was president. Some did not get much more prestige than that. Now, those portraits also reflect the kind of subjects that Beaux tended to use, which were mostly women and children. For example, in her first major work, her subjects were ..., the painting featured her sister and her nephew. Yes, Mark?
Student
Yeah, it just seems interesting. I was wondering if that was unusual to have a portrait artist who is a woman become so well-known and successful in the 19th century.
Professor
Great question. Yeah, she really stood out back in the 1800s. And today, she is still considered one of the greatest portrait painters of her time, male or female. In fact, she was the first full-time female instructor at the Pennsylvania Academy of the Fine Arts, and she was a full member of the National Academy of Design. These are pretty important institutions, so, yeah, she definitely made headway for women artists. Ok, so let’s look at one of her portraits now, this painting is called The Dreamer. It is one of my favorites. And I think it is especially characteristic of Beaux’s work. So what you see here is a portrait of a close friend of Cecilia Beaux. So tell me what’s the first thing that draws you to this painting? What catches your eye first.
Student
Well, for me, it is her face and hands, I think they are really expressive, and also, they make the woman seem very comtemplative, seems like she is thinking pretty seriously about something.
Student
Yeah, her eyes kind of draw you in. But what strikes me is the contrasting colors, the white dress and the dark background. It kind of reminds me of that painting we discussed a few weeks ago, by ...eh... John Singer Sargent. I think it was called MadameX?
Professor
I agree, good point. Yes, Beaux had high regard for Sargent’s work. And this is something, a technique you will find in both of their work. Ok, but the painting is called The Dreamer. What do you see is dreamlike about it?
Student
Well, the background behind the woman is pretty vague. Like, maybe there is no real context, like no definite surroundings, expecially compared to the woman herself, since she is so clear and well-defined.
Professor
Yes, the unclear background definitely contributes to that dreaminess. It is meant to show a sense of isolation I think. With the woman is deep in a daydream and not really aware of anything eale. This painting shows how insightful Cecilia Beaux was as a portrait artist. Besides her excellent technical skills, like her use of brush strokes and color to make an impression, both respectives come through. Her portraits reveal her own interpretation of her subject’s state of mind. This is what it is all about, not just likenesses
Now, the undefined background also shows how Cecilia Beaux was influenced by the French Impressionists, who believed, like Beaux, in a personal rather than conventional approach to their subject matter. Beaux used some impressionist techniques and share much of their phylosophy, but her style, it was all her own.
