Flowering Plants And Their Parts (1966)

plants from the Amazon River special care when they're transplanted to botanical gardens like this in the tempered zone of North America. Leaving our display of South American plants, ladies and gentlemen, we come to still another display of exotic growth. Our collection of flowering plants from Australia. Sorry, but we've left out the kangaroos. Over there to the right, you see a few of the many trees and plants native to the Australian rainforest. Of the large variety of plants one finds in that area, no one can say for sure how many different kinds of plants there are. in areas which are there may be hundreds of different kinds in a botanical garden. Yet this is only a small sampling of plants found around the world. African section. We'll circle around to give you a better view of one of the green plants grow everywhere. Different kinds in different places. At least a quarter of a million kinds are known already. Yet plant explorers are constantly finding new ones, like this recently discovered barrel cactus. Each kind of green plant is different in some ways from every other kind, but are most of them alike in any way? In its simplest parts, this green plant, an aphalandra, is made up of a central column branched at the bottom and at the top. In other words, it has three main parts. Roots, stem, and leaves. In almost all green plants, the arrangement of roots, stems, and leaves is basically the same. Now, let's find out something about what the three parts do for the plant. We'll begin with the roots. Here are two radish plants growing in soil. This vessel contains water with dye dissolved in it. Watch. Now the roots of both plants are immersed in the dyed water. We leave them there for about 2 hours. 2 hours have passed and nothing seems to have happened. Or has it? Why does only one radish show traces of the dyed water inside? You will recall that this plant was lifted gently from the pot and the soil washed carefully from the roots. This one was pulled out and most of its roots were stripped off in the process. It did not take in any of the dyed water. The radish that took in dyed water must have done so because it still had all of its roots. Through a microscope, roots look like this. Simple round tubes through which water can flow. Growing out of each root are tiny root hairs. Water and substances dissolved in the water enter the plant through the thin walls of the root hairs and the root itself. As plants grow and roots develop, the roots penetrate the soil and anchor the plant. So in rough weather, the roots give the plant a foothold and keep the soil in which the plant is growing from being washed away. Now let's find out something about what stems do. This jewel weed will be convenient for that purpose because its stem is nearly transparent. We've seen that roots enable a plant to take in water and dissolve minerals. What happens to this solution after it enters the roots? We'll immerse the roots of the jewel weed in the same dyed water used with the radishes. The dyed water entering the roots moves upward through the stem. Then it is carried into the leaves. But how? When the stem of the jewel weed is cut open, we can see the pathways through which the dyed water moved. Through a microscope, the cross-section of a typical stem looks like this. It shows the open ends of many tiny tubes through which water can move. The tubes are arranged something like a cluster of soda straws that have been glued together. The stems of different kinds of plants differ in their details. But whether the plant is only 6 in high like the jewel weed or over 300 ft high like these California redwoods, the stems carry water and minerals to where they're used and provide a framework for the plant. What about plant leaves? Is there anything similar in the way the leaves are arranged on most plants? A close look at most any plant will show that the leaves are exposed to as much sunlight as possible. Even the leaves of a tree are spread out so that each leaf is at least partly in the light of the sun every sunny day. But why? One way to find out something about leaves and sunlight is to see if there's any difference between a part of the leaf that has been in the sun and a part that's been covered. Two pieces of cardboard will keep light from falling on part of this leaf. The time is 9:00 in the morning. We'll leave the plant, a geranium, here in the sun and continue the experiment in the afternoon. Meanwhile, here's something you'll need to know to understand the experiment. The white powder is corn starch, a form of food. The bottle contains iodine solution. Starch when it comes in contact with iodine turns blue black. Whether it's in powder form like pure corn starch or in a piece of bread, it reacts the same way. Now 8 hours later, we can continue the experiment with the geranium plant. No visible change has taken place in the leaf. But wait, the leaf is dipped in boiling water to soften the cells inside the leaf. Then the leaf is placed in hot alcohol. Within a few minutes, the hot alcohol has dissolved most of the green coloring out of the leaf. Still no visible effect of the sunlight. But watch what happens when we pour some iodine solution on the leaf. The leaf has starch in it but only where it was exposed to the sun. So the leaf has been manufacturing food with the help of sunlight. Where there was no sunlight, no food was made. We can see something of where this food making takes place by taking a closer look at the leaf. Inside the leaf is a system of veins through which water can move. When the under surface of a leaf is seen through a microscope, small openings called stomates are revealed. Through them, air can flow into and out of the leaf. Inside the leaf are tiny cells containing the substance that makes plants green. It is called chlorophyll. The chlorophyll traps the energy of sunlight. With this energy, the leaf is able to make food from the water and carbon dioxide from the air circulating inside the leaf. Now we know why leaves on a plant are arranged to catch sunlight. They use the sun's energy to manufacture food to keep the plant alive. So three main parts make up a plant. Roots, stems, and leaves. And each part is dependent on the others. The roots anchor the plant in the soil and take in water and dissolved minerals. The stem provides support for the plant and moves water and minerals to where they're used. The leaves containing chlorophyll use the energy of the sun to convert water and minerals from the soil and carbon dioxide from the air into food the plant needs to live. A watery solution of food passes out of the leaves to be used or stored for use in some other part of the plant. Unused substances, mainly water vapor and oxygen, pass out of the leaves through the stomates into the surrounding air. A remarkable process. But what have we left out? What we have left out is the flower. Actually, a group of specialized leaves that are able to produce seeds. Seeds when planted will usually grow into new plants exactly like the ones they came from, but not always. Among the billions of seeds nature produces each year, small changes may occur. Many small changes over long periods of time have produced new plants whose roots or stems or leaves are specially adapted for life in different environments. What adaptations might help a plant survive on the surface of a pond where the water level changes with the seasons? As an example, here are some water hyasins. Their roots float free of the bottom, a definite advantage for a plant living where the water level changes. The stems are designed to keep the leaves above water in the sun. They contain thousands of tiny air sacks that act like floats. These adaptations enable the water hyasin to survive in a wet environment. What adaptations might help a plant survive in a hot and dry desert? A plant with broad leaves, continuously evaporating water, would soon die here. But over long periods of time, an unusual plant like the sawara cactus evolved. Its enlarged stem is adapted for storing great quantities of water and for making food. In place of leaves, it has hard narrow spines. So, a plant like this loses very little water. Its flowers produce enough seeds to make the plant common in this part of the desert. A sawarro cactus seems unusual because it is specially adapted to life in an uncommon environment. But what about the plants that grow where you live in nearby woods, parks, or your backyard? Do most of them have typical roots, stems, leaves, and flowers? What kind of plants grow best where you live and why