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ANCHORING ABILITY OF ROOTS
What do plant's roots do? They keep the plant from wandering away from where it was put. They take in nutrients from the soil to feed the plant. They take in water to keep the plant from drying up and dying.
What do plant roots do for us? How could they possibly do anything for us? What do they do for the environment--for our world? The roots of trees keep the tree from falling over if we put a swing on a branch. That's not very important, is it? Probably the most important thing that roots do for the environment, and for us, is that they hold soil in place.
Hillsides without plants on them are dangerous if there is heavy rain. Bare earth that slopes can get saturated (that means filled up) with water, and then it can slide or slump. Sometimes, a huge chunk of water-logged soil on the side of a hill will break off and slide down to the bottom of the hill. That's pretty bad if there are buildings in its way, or a highway. Sometimes, a bare, water-logged hillside will "slump," which means it will start to sag, and there will be a bulge at the bottom of the slump. If the slump gets even more heavy with water, it can break off and slide down to the bottom of the hill.
When you drive down the highway, you can look on the sides of the highway and see where the road-builders cut through a hill in order to make the road. If the hill they cut through is solid rock, you will see the exposed, cut rock. If the hill they cut through is earth, you will see plants on it. In warm climates, they often plant a succulent called "ice-plant," which grows really long, strong roots. The hill planted with ice-plant is not likely to slump or slide, because the roots hold it in place where it belongs. Further, the roots take in and use most of the water that falls on the plants. (Some of the water is taken in by the leaves, as well.) In cool climates, the road-builders often plant shrubs, or small trees, or both. They select plants that are known to have long, strong roots.
developments that are on or near a hillside are required to have either
plants or concrete retaining walls, to protect the houses and roads from
landslides. In most
In areas where there are no buildings or roads, a forest fire, or a logging operation can take away the trees and bushes, and the land will slump or slide when there is a heavy rain. A few years after the landslide (or slump), plants will grow there naturally, having been planted by the wind blowing seeds from other plants nearby, or by animals, either from their droppings or from picking up seeds on their fur and then dropping them.
The experiment we are going to do is to check the strength and size of some different kinds of roots. We don't want to be pulling up nice plants, so we will look for weeds that nobody wants. We'll pull up several different kinds of weeds; some from dry places and some from wet places. Weeds from dry places might be by a roadside or on a vacant lot where nobody is watering the area. Weeds from wet places could be from people's gardens where they water them, or, if there has recently been heavy rain, a low place on the ground may have weeds that are wet most of the time.
In order to get the roots of weeds in dry places, we may have to take a shovel and dig them, because if we just tug on them, the roots will probably break off and we wouldn't have anything to study. In any case, we want to gather our weeds carefully so that we do get the roots.
We will compare the roots of the different kinds of weeds, and decide which ones probably have the best holding power, or "anchorage." In addition, we want to find some of the same weeds growing in wet places as we find growing in dry places, and see if the roots are any different.Do you think roots need more, or less, strength if they are in a dry place than if they are in a wet place? Why?
Some kinds of plants have roots that grow from the main stalk (or trunk, if it's a tree) down to the soil, and then into the soil. Those are called "prop roots," because they prop up the tree or plant to keep it from falling over. Corn plants have prop roots. If we can, we will find some corn plants and take a look at these prop roots.
What other kinds of plants have prop roots? Trees that grow in swamps have them, because the very wet soil does not provide a firm enough foundation to hold up a large tree if it just had regular roots. Some of those trees are mangrove, banyan, and cypress. Unless we live near a swamp, we aren't likely to find those kinds of trees, but the library has photographs of them. We could break up into groups and look in the library for information about trees and other plants with prop roots.
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