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Plant Reproduction and Development Chapter 23 23:1 Asexual Reproduction in Plants Asexual reproduction: When an organism creates offspring that are IDENTICAL to itself. Only one parent is involved in asexual reproduction. There is NO SWAPPING of genetic material between TWO different parents. Plants can reproduce asexually There are 3 plant body parts that a plant can use for asexual reproduction: stems leaves roots Asexual Reproduction by Roots Many plants have roots that can grow into whole new plants. Each new plant has its own root system, stems and leaves. For instance: If you place a sweet potato into a glass of water: overtime the potato will develop new leaf shoots and roots The new plant grows through Mitosis There is no egg or sperm involved in this type of reproduction. There is no fertilization involved. There is no swapping of genetic information between two parents. Many plants: If cut down and the roots are left intact in the ground will grow new stems and leaves. A tuber: is an underground root or stem swollen with stored food Asexual reproduction by leaves Some plants can reproduce asexually from leaves. Some leaves, when removed from the main plant, will grow into an entire new plant. There is only one parent. The new plant looks just like the parent plants. Asexual reproduction by stems There are several ways that stems of flowering plants reproduce asexually. A runner: is a stem that grows along the ground or in the air and forms a new plant at its tip. (the new tip can be potted and becomes a whole new plant) Asexual reproduction by stems Some stems are underground: potatos and onions are both underground stems Bulbs: are short underground stems surrounded by fleshy leaves that contain stored food Everyday Applications: Gardeners and farmers use their knowledge about asexual plant reproduction in order to grow plants from cuttings or graftings. Cutting: a small section of plant stem that has been removed from a parent plant and planted to form a NEW PLANT Grafting: is a process of joining a stem of one plant to the stem of another plant. 23.2 Sexual Reproduction in Plants Flowers and Sexual Reproduction Parts of a flower: Sepal: often green, leaflike parts of a flower that protect the young flower while it is a bud Petals: are the brightly colored parts and scented parts of a flower. Used to attract insects. More Parts of a Flower Stamen: is the male reproductive organ of the flower. Usually 1 or more. Pollen grains are formed in the stamen. Flower Parts Pistil: is the female flower part. Usually only 1. Each pistil has a large round OVARY at its base. Flower Parts Inside the ovary are OVULES which are the “eggs” for the flower. Pollination and Fertilization Sexual reproduction: swapping of genetic information between two parents. In plants this occurs from POLLINATION. Pollination: is the transfer of pollen from the male part of a seed plant to the female part Pollination and Fertilization In flowering plants the design of the flower is important for pollination to occur. Many flowers are brightly colored. Many flowers are strongly perfumed. Some flowers produce nectar. Common Pollinators Pollinators Common Pollinators: Insects, moths, butterflies, birds, and the wind! CROSS POLLINATION is when pollen from the stamen of one flower is carried to the pistil of another flower on a different plant Cross Pollination Self Pollination Self pollination: Is when pollen moves from the stamen of one flower to the pistil of the same flower, or of another flower on the same plant How does pollination occur? 1. The pollen grain lands of the tip of the pistil. 2. The pollen grows a tube INTO the stalk of the ovary. 3. The tube reaches the ovule and the sperm passes into the ovule to fertilize the egg. 4. A new plant or embryo grows inside the ovule and becomes a seed. 23.3 Plant Development Seeds and Fruit Flowers change after fertilization occurs: -after fertilization the ovules have been fertilized by the sperm in the pollen -after fertilization the petals, stamens and stalk of the pistil wither and die Seeds and Fruits The ovules and the ovary begin to grow The ovules mature into seeds Seeds and Fruits A seed: is a plant part that contains a plant embryo The embryo of a plant has a new young plant and stored food. This is a result of the joining of the egg and sperm nuclei in the ovule Seeds and Fruit As the ovary matures it becomes a fruit. A fruit is an enlarged ovary that contains seeds. Anything you eat that has seeds is considered a fruit!!! These are ALL considered Fruit Seeds and Fruit One seed develops from every fertilized ovule in an ovary. MEANING: in a cherry there was only one ovule. In a peach there was only one ovule. In an apples there were around 5 ovules. Etc…. Plant Development from Seeds What happens to a fruit once they have ripened? -eaten by an animal and the fruit part is digested and the seed is passed in animal droppings after the animal has traveled along their daily activities. OR - More often the fruit stays on the tree and eventually pops open to drop the seed on the ground Plant Development from Seeds Larger seeds can be taken away by water. Plant Development from Seeds Some seeds are taken away by the wind. Plant Development from Seeds The wind disperses these tiny seeds from the dandelion. Plant Development from Seeds Burrs get stuck on the fur of an animal and will eventually fall off during the animals travels. The seed is surrounded by the hooks that get stuck on the animal fur. What happens next? If a seed lands on soil that has moisture and proper temperature, it may germinate. Germination: the first growth of a young plant from a seed. In many plants the main part of the seed is the source of food. It is available for the growth of the new plant. What happens next? In bean seeds the two halves of the bean are a food source for the growing plant. The stem that is coming out of the bean seed have leaves on them for photosynthesis. When the food supply from the two halves of the bean is used up they fall off the plant. Comparing Kinds of Reproduction Asexual Reproduction 1. 2. 3. 4. 5. One parent Uses Mitosis Produces adult plants in a short time Some plants don’t produce seeds so can’t reproduce sexually All plants from asexual reproduction are clones of the original plant Definition: A CLONE is a group of living things that come from one parent and are identical to the parent Comparing Kinds of Reproduction Sexual Reproduction 1. Two parents 2. Characteristics from both parents 3. No two plants will have the same combination of traits 4. A wide variety of traits in offspring 5. Seeds survive until the environment is right for the survival of the seed and ultimately the flower 6. The variety of traits allows the plants a better chance to survive if conditions change.