Life Of A Plant (1949)

Here [Music] is a pea plant growing. We have speeded up the action by time-lapse photography so that we can see in a few seconds the growth that takes weeks in nature. [Music] In this film, we shall study the life cycle of the pea plant, a representative green flowering plant. The seed containing the beginning of a new plant and a supply of food starts germinating. The main root begins growing downward into the soil and the stem grows upward. [Music] A root grows in length only at its tip. As a root grows, it may change direction and pass around obstacles in its path. Soon branch roots begin developing. Water and minerals are moving from the soil through the roots into the stem. Besides connecting the plant with this source of raw materials, roots anchor the plant in the soil. While the roots are developing, the stem is also a life cycle in the growth of a living pea plant. We shall study some of the processes inside the plant that have made it possible. Here are four of the principal processes going on at once. To simplify our presentation, we will identify each action separately. The white dots represent dissolved minerals and water moving from the soil to all parts of the plant. The white ovals represent carbon dioxide gas from the air. Carbon dioxide is used by green parts of the plant in making sugar. In this process, oxygen is liberated. The black ovals represent substances mostly water escaping from the leaves and the black dots represent sugar and other foods made in the plant. The movement of raw materials is mostly in an upward direction from the soil while the movement of the manufactured foods is mainly downward through the plant. So we see that the top of the plant depends upon the roots for water and minerals and the roots depend upon the tops for manufactured sugars. Up through the stem go the water and minerals shown here again as white dots. These pass through tissues near the center of the stem. Food manufactured by the plant. The black dots passes through tissues near the outside of the stem. In this cross-section of a stem, we see again the tissue shown in white that conduct water and minerals from the roots and those shown in black that conduct manufactured foods to all parts of the plant. As cells between these two tissues multiply, these tissues increase in size. This causes growth in the diameter of the stem. Any green part of the plant can manufacture sugar. The green part of the plant in the presence of energy from sunlight uses carbon dioxide from the air and water from the soil in making sugar. This process is called photosynthesis. Since green leaves constitute most of the green part of the plant, most of the sugar is made in the leaves. All the cells of the plant may use this sugar in the making of other kinds of food. After the pea plant has been growing for about 40 days, it reaches the stage of growth when flowers begin forming. We shall show in animated drawings some of the actions taking place in the flower. Inside are a female part and several male parts. The large vertical part shown is the tip of the female organ called the pistol. Around this tip are the smaller male parts called stammans. At the end of each stamon is a pollen sack called the anther. Inside are pollen grains. When the anther matures, it splits open, freeing the pollen grains. Some of the pollen reaches the tip of the pistol. This is pollination. Once a pollen grain contacts the pistol, it begins germinating and producing a tube that grows through the pistol into one of its ovules. Here the union of sperm and egg occurs. This is fertilization. The fertilized egg in each ovule develops into an embryo plant. The mature ovule containing the embryo is a seed. So we have seen a flowering plant growing and have identified its principal parts. Six in all. Four of the six can be seen here. The seed, the roots, the stem and the leaves. The flower and the fruit containing the seeds develop at a later stage. We have seen how the leaves unfold as the plant develops and have learned that the green parts begin the work of manufacturing sugars. [Music] We have learned that by using these sugars all living cells of the plant can make their own food. [Music] We have seen too the work of flowers, the reproductive organ of plants and have learned that inside the flowers pollination takes place. Following growth of the pollen tubes, fertilization occurs. The fertilized egg grows into an embryo and the ovules become seeds. The pod or fruit of the pea plant develops from the pistol of the flower. Inside the growing pod are the developing seeds. [Music] Thus we have completed our study of the life cycle of a typical green flowering plant. What we have seen here is essentially the story of every flowering plant. And it is upon such flowering that we and many other animals depend for much of our food supply. The life cycle has involved several processes, but mainly those by which the plant absorbs raw materials from the soil and carbon dioxide from the air and manufactures food which nourishes the plant and makes possible its growth and reproduction. [Music]