Reproduction In Plants (1958)

[Music] this is a story about plants it's a story that applies to all the many kinds of plants cultivated plants as well as wild plants of every type the story applies to green plants those with chlorophyll as well as to plants that have no chlorophyll the story is plant reproduction we'll find the simplest kinds of reproduction in the simplest plants these algae are among the simplest plants let's look at some algae under a microscope these are blue green algae each is a separate one- celled plant during reproduction the living protoplasm of the plant pinches together until two separate plants are formed we call this splitting fishing or cell division when these two plants are mature they too can reproduce Ed by fishing we call this kind of reproduction asexual reproduction is a sexual reproduction limited to simple one celled plants this kind of alga oogonium is made up of many cells forming long filaments or strands each plant has specialized cells for example the plants are anchored in place by hold fast cells cells are vegetative cells whose purpose is growth and food making some of the vegetative cells are converted into reproductive cells here several reproductive cells are developing ready to escape from the parent plant the entire living matter of the cell the protoplast empties escaping from the parent plant we call this new plant a oore watch as it escapes from the parent plant the zoospore moves to a different location where it may anchor itself in Time Each zoospore will grow to be identical with the parent plant we have seen two examples of asexual reproduction in a simple and in a more complex plant in each example there was only one parent reproduction was accomplished by the division of some of the living matter of the plant and each new plant grew into an identical offspring of the parent there is another way in which plants can reproduce here here in this ionium the same kind of alga we saw before we see what looks like a zoospore being formed but this is the beginning of an egg cell a female cell in another filament are special sperm producing cells which form tiny male or sperm cells these smaller sperm cells are released and travel toward the egg cell watch as the smaller SPM enters an opening in the filament to fuse with the egg cell this is fertilization the fusion or Union of one sperm cell and one egg cell the fertilized egg is called a zygote when ripe it breaks off from the parent plant eventually the zygote can germinate grow into a new plant the process we have seen is an example of sexual reproduction so plants reproduced by asexual or sexual reproduction asexual reproduction involves a division of protoplasm sexual reproduction involves a union of protoplasm we can learn more about plant reproduction from flowers flowers have many forms they may look like this or this or this yet in any flower we can identify the reproductive organs let's look at this Lily here are the stamans the organs that produce pollen grains which are tiny male plants here is the pistol the organ which produces tiny female plants removing the stamans we find that the pistol has a sticky surface at the top the stigma the stigma is supported on a long neck called the style above the ovary if we take an ovary and slice it open we discover several ovules the beginnings of seeds within each OVU is a tiny female plant at the top of the stamans are the anthers or pollen sacks supported on Long filaments ments in the anthers pollen is produced it comes off the anthers when touched pollen looks like very fine dust but under the microscope we see Tiny grains here are the pollen grains from the Holly Hawk the Nerium and the Primrose each pollen grain is a male plant when ripe pollen grains fall from the anthers onto the stigma and adhere to its sticky surface within the pistol the pollen grains begin to grow long extensions pollen tubes each tube carries two male protoplasts at its end the pollen tubes grow until one pollen tube penetrates an ovule and one male protoplast fertilizes the female protoplast in the ovule to form the zygon within the ovule the zygote grows into an embryo in time fertilized ovules May develop into seeds each containing the embryo of a new plant if we plant some seeds of the Lily and if conditions are favorable new lily plants will grow let's remember that these new plants are the result of sexual reproduction they are also an example of self pollination since the eggs were fertilized by pollen from the same flower but in certain flowers self-pollination is impossible in this Prim Rose for example the stamans are not tall enough to let pollen drop onto the stigma neither is self-pollination possible in such flowers that grow only stamans or flowers that produce only pistols how is pollination accomplished in cases like we remember that microscopic pollen like dust is very light and that the wind can carry it from flower to flower insects too when visiting flowers may carry pollen grains from the stamans of one flower to the sticky stigma of another flower and couldn't pollination be done artificially couldn't we transfer pollen from one flower to another breed our own plants yes by cross-pollination we can crossbreed plants of the same species cross-pollination a form of sexual reproduction can result in a great variety of the same species of plant here for instance are differences in size and color in patunas these characteristics are carried by the sexual cells and combined when flowers are cross-pollinated for example we might cross-pollinate the tall red petunia with the short white one in this case all the first Offspring are red and Tall since red and tall are dominant characteristics if two of these red and Tall offspring are cross-pollinated we get both red and white offspring so in sexual reproduction offspring are not always identical with the parents could we select the particular characteristics we want yes scientists have learned by selective breeding to create new varieties of plants selective breeding is used in growing many domestic plants these young men are cross-pollinating corn they carefully collect pollen from from one plant to fertilize the ovules of another plant once again we are seeing an example of sexual reproduction in a plant reproduction that depends upon stamans and pistols from the fertilized ovules seeds will grow seeds of corn the ear at the left is a hybrid corn the result of years of selective breeding not only better grains but better fruits can be produced however many fruits and nuts do not reproduce easily from seeds suppose we wanted to reproduce a smooth shelled Walnut instead of a rough shelled Walnut stems from a tree having the characteristics we want are grafted into the trunk of another walnut tree the grafted branches will grow and produce smooth shell walnuts identical to those of its parent many other plants reproduce similarly a bud or eye cut from a potato tuber and planted will grow a new potato plant we call this vegetative propagation a form of asexual reproduction in the same way other important food plants such as bananas can be reproduced by propagation by planting a part of the stem banana trees can be grown identical with the original parent plant plant breeders are constantly experimenting to develop new and better varieties of plants by using the principles of plant reproduction we have seen some of these principles asexual reproduction means the division of some of the protoplast in a single parent producing offspring that are always identical to the parent plant sexual reproduction means the combination of two different kinds of cells egg or female cells and sperm or male cells a combination of one egg cell and one sperm cell results in a fertilized egg that contains the embryo of a new plant if different varieties of the same species are cross-pollinated a combination of their characteristics will appear in The Offspring in sexual reproduction offspring are not always identical with parents we make use of this fact in selective breeding to create new varieties of plants and by vegetative propagation we can often ensure that our selection will continue to produce The Offspring we want learning these few basic ideas about plant reproduction helps our understanding of plant life and in turn of other living things [Music]