The Growth of Plants (sound)

foreign although we commonly consider the animal kingdom as of Greater importance It is Well to remember that plants are the ultimate source of food for all forms of animal life like animals plants need proper food and sufficient air and water in order to live and thrive here we shall see the life story of a typical plant condensed into a few minutes beauty is the principal appeal of flowers beauty of color beauty of form beauty of fragrance also the flower has a most important and most interesting practical function it is the Forerunner of the seed and it is by means of seeds that the flowering plants reproduce themselves the seed of the pea plant germinates or starts to grow by sending a root downward into the soil and a stem upward into the air with the time speeded up we shall see the main or primary root branching and developing root hairs near the tips The Roots have two uses namely to Anchor and support the plant and to absorb water and other food from the soil the latter is accomplished mainly by the root hairs the stem pushes up through the soil in an arched or bent over position thus protecting its first young leaves the stem supports the leaves which need air and sunlight for their work oxygen of the air is used in breathing and carbon dioxide is used in making starch for food the stem of the pea plant not being very rigid depends upon its tendrils for support the leaves are the breathing organs and also the food factories the tendrils twine about the string and thus support the stem of the plant in the picture see them respond to the stimulus produced by the string the growth on the inner side of the curve of the tendril seems to be checked by the contact with the string and this causes it to twine around the support note how firmly the tendrils attach themselves to the support they twine around and around until there is not the least danger of being pulled loose the tendrils seem to seek a support and in this apparent search they seem to avoid each other note The Swinging of the top of the plant with the tendrils it seems as if under the control of a brain as are the voluntary acts of animals nothing gives us so good a notion of opening flowers as the motion picture with the time speeded up by time lapse photography these remarkable nodding movements are due to the change of the rate of growth on the various sides if one side grows faster for a time then the op then the opposite the stems lean away from the side growing most rapidly it should be remembered that the time is greatly speeded up in this close-up of the Pea Blossom the lateral or side petals are drawn apart exposing the boat-shaped Keel which is made up of two petals the Keel protects the essential parts of the flower the stamens and the pistol now let me open a wing inside is a projection here which fits into a Groove here in the queue the top or outer tip of the pistol is called the stigma the stalk of the stigma is called the style and the lower part of the pistol is the ovary in which the seeds develop the pistol may be called the female part of the flower the stamens are the male part of the flower it is in the pollen sacs or anthers of the stamens that the pollen grains develop bees in their quest for nectar out of which to make honey May brush the pollen grains from the stamens and carry them on their bodies to other flowers and thus bring about cross fertilization which is so important in the life history of most of our flowering plants the bee in seeking nectar from the Pea flower accidentally or incidentally gets the pollen grains on its body for the pollen grains are ripe and are being shed when the nectar is ready another view of a bee visiting a pea blossom she is probably attracted by the bright color and by the fragrance of the flower the bee's perception of color is probably not just like ours and her sense of smell is probably much more acute in visiting the next flower it is very probable that some of the pollen grains carried by the Bee will be brushed upon the stigma and thus fertilization will be brought about we could not photograph pollen tubes growing from the stigma down through the style for the style is opaque hence these germinating pollen grains were photographed in a clear solution and they were photographed through a microscope note how each pollen grain puts out a long tube which after many hours will reach the ovule in the pollen tube note the streaming of the protoplasm which is the living substance of the plant this is an unusual picture after the male cell has moved out of the pollen tube and has United with the egg cell in the ovule that is after the egg cell has been fertilized the ovule will develop into a seed here we see how our viewers become seeds the pollen grains which are carried to another flower and left upon the stigma will germinate and send tubes down through the style to the ovules or the beginnings of seeds in the ovary the pollen tube will penetrate an ovule and the male cell which came from the pollen grain will move out of the tip of the pollen tube and Unite with the egg cell and that Union is fertilization the egg cell after fertilization that is after it has United with the male cell which came from the pollen grain reveloped into a tiny plant or embryo within the seed after fertilization has occurred the flower Withers and the pods grow to accommodate the developing seeds Within the Pod continues to develop until the seeds are ripe the remains of the withered flower may be seen at the outer end The Ripe seeds are a resting stage in the life history of a plant after the seeds are ripe the pods burst open as shown here and the parts of the Pod curl up with such energy that the seeds are shot at considerable distance this scattering of the seeds far and wide is a distinct advantage in wild plants for in this way they establish themselves over greater areas the germination of this seed on top of a rock shows the lack of suitable conditions the proper requirements are sufficient moisture but not too much sufficient warmth but not too much and reasonably pulverized soil here we see the young Plant die on account of improper conditions contrasted with the last here is a seed germinating under ideal conditions note the root growing downward with secondary roots or branches growing out from the main or primary root note the root hairs which are always a short distance back from the root tips note the stem growing upward that is in a direction opposite to that taken by the root in this picture we have examined the life story of the Pea and have followed it from one generation to the next what we have seen here you yourselves May reproduce by actually growing these plants in a window box or garden let your teacher suggest other experiments in plant growth