ANIMAL PLANT SOIL SCIENCE E 3 1 PROPAGATING

ANIMAL, PLANT & SOIL SCIENCE E 3 -1 PROPAGATING PLANTS SEXUALLY

Interest Approach Bring to class several varieties of corn or soybeans. If plants are not available, use a seed catalog that contains color pictures of plant varieties. Ask students about the significance of variety. Ask if they can tell you how varieties are obtained? Ask how genetic variation in agricultural crops has impacted our world food resources? Show students a variety of bean seeds. What do the seeds have in common? What is different about them? How does germination unlock the “secret” within each seed?

Objectives 1 Explain sexual reproduction of plants and examine its importance in plant survival. 2 Examine the role of meiosis in the development of gametes. 3 Define pollination and investigate the different methods of pollination. 4 Describe the fertilization process in flowering plants and explain how seeds are formed. 5 Describe the process of seed germination and what conditions are necessary for germination to occur in a seed.

Terms anaphase anemophily cell chromosomes cotyledons cross-pollination cytokinesis diploid double fertilization embryo plant endosperm entomophily

Terms fertilization gametes germination haploid hybrid hydrophily incompatibility meiosis metaphase mitosis pollenizer pollination

Terms prophase scarification seed coat self-pollenization self-pollination sexual reproduction stratification telophase turgor zoophily zygote

What is sexual reproduction of plants and why is it important to plant survival? I. Sexual reproduction in plants involves the union of the male pollen with the female egg and results in the formation of a seed. Sexual reproduction enables a plant to produce new combinations of genetic information that may add to the vigor of the developing young plant.

What is sexual reproduction of plants and why is it important to plant survival? A. Most plants reproduce their own kind in nature through sexual reproduction that forms some type of seed. A seed is a living entity that serves as a bridge between generations of a plant.

What is sexual reproduction of plants and why is it important to plant survival? B. The recombining of genetic material in a species gives it the means to adapt to changes in the environment. Some of the changes may be beneficial and some may not. As conditions of the environment change over time, the beneficial changes in plant genetics will allow the plant species to survive. As plants continue to reproduce, they pass genes onto their offspring, which enables them to survive.

What is the role of meiosis in the development of gametes? II. A cell is the basic unit of life and consists of the cell membrane, cytoplasm, and the nucleus. A. Chromosomes are found in the nucleus; they carry genetic units, known as genes, that govern specific traits. Chromosomes are found in pairs in all cells except in the reproductive cells. Corn has 20 chromosomes or 10 pairs. Both members of the chromosome pair contain the same genes in the exact same location or loci on the chromosome. Therefore, for any one trait there exists a pair of genes responsible for its expression. The following lists the number of chromosomes that each plant contains: corn— 20, barley— 14, alfalfa— 32, potato— 48, cotton— 52, carrot— 18, garden pea— 20, lettuce— 18, and wheat— 42.

What is the role of meiosis in the development of gametes? B. Cells can reproduce by two main methods in multicellular organisms—mitosis and meiosis. 1. Mitosis is a type of asexual reproduction in which two new cells are created from the original cell. Each new cell has the same number of chromosomes as the parent cell and is genetically identical to the parent cell. Mitosis continues throughout an organism’s life. The following are the five phases in cell division, with the first four making up mitosis:

What is the role of meiosis in the development of gametes? a. Prophase: The nuclear membrane begins to break down, spindle fibers appear at each end of the cell, and chromosomes become visible as paired bundles. b. Metaphase: Spindle fibers attach to the chromosomes as they group together. c. Anaphase: The chromosomes divide and separate, moving to opposite ends of the cell. d. Telophase: New nuclear membranes form around the groups of chromosomes, the spindle fibers disappear, and the chromosomes uncoil. e. Cytokinesis: In this final phase, the organelles move to the new nuclei, and the cell completes division by forming a plate between the two new complete cells.

What is the role of meiosis in the development of gametes? 2. Meiosis is cell division that creates four new cells from the original parent cell resulting in four sex cells called gametes. Meiosis occurs in the flower (in angiosperms) to form the cells from which the pollen grains and the embryo sac (which contains the egg) develop.

What is the role of meiosis in the development of gametes? a. The four daughter cells have half a set of chromosomes. Also, meiosis results in a random assortment of parental genes. Therefore, each of the four cells is genetically different from each other and the parent cell. b. The steps of meiosis include: Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Interphase, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis. c. Sexual reproduction takes place when the gametes (sperm and egg cells), created by meiosis, unite and fertilization occurs. The offspring produced by sexual reproduction receives half of its genetic information from the female parent and the other half from the male parent. A zygote results from the fusion of gametes. Thus, a new plant is created by sexual reproduction.

What is pollination, and what are the different methods of pollination? III. The reproductive process begins with pollination. A. Pollination is the transfer of the male sperm carried in the pollen to the female part of the flower, the stigma. Some plants rely on wind and water to transfer the pollen to the stigma. Other plants depend on animals to help with pollination. Birds, insects, bats, and other animals are attracted to brightly colored or scented flowers.

What is pollination, and what are the different methods of pollination? 1. Pollination by wind is called anemophily. 2. Pollination by water is referred to as hydrophily. 3. When vertebrates including birds, bats, and other animals, pollinate flowers, the process is called zoophily. 4. The process of insects transferring pollen is called entomophily.

What is pollination, and what are the different methods of pollination? B. Pollination can be self-pollination, self-pollenization, and cross-pollination. 1. When the pollen of a plant pollinates a flower on the same plant without the influence of a pollinator, it is called self-pollination. Many plants have the ability to self pollinate, others do not. Some plants have genetic mechanisms that prevent their pollen from growing a pollen tube on a style of the same plant. This condition is called incompatibility. 2. When a plant is self-pollinated through the efforts of a pollinator, it is said to be self-pollenization. 3. When the pollen of a plant pollinates the flower on another plant of the same species, this is called crosspollination. Cross-pollination requires a pollinator and an external pollenizer. A pollenizer is the plant that provides the pollen.

What is pollination, and what are the different methods of pollination? C. Once the pollen lands on the stigma, it grows a thin pollen tube down the style to the ovary. The cell within the grain of pollen divides to form two sperm nuclei. The sperm cells or male gametes travel down the pollen tube to an ovule that holds the egg or the female gamete.

What is the fertilization process in flowering plants, and how are seeds formed? IV. Fertilization is the fusion of sperm with an egg. The egg and the sperm contain a single set of chromosomes and are said to be haploid. Fertilization unites the single set of chromosomes in the sperm nucleus with the single set of chromosomes in the egg nucleus. This enables the fertilized egg, or zygote, to have a complete pair of chromosomes. A cell with two sets of chromosomes is termed diploid.

What is the fertilization process in flowering plants, and how are seeds formed? A. In flowering plants fertilization is unlike that of any other living organism. This is because both sperm nuclei from the pollen grain are involved in fertilization, and this fertilization process of flowering plants is called double fertilization.

What is the fertilization process in flowering plants, and how are seeds formed? 1. The first fertilization occurs when one of the sperm fuses with the egg. In this process, the sperm carries genetic material from the male part of the flower. The egg contains genetic material from the female part of the flower. The resulting zygote contains genetic material from both the male and female parts of a flower. Through cellular division the zygote becomes the embryo or immature plant. 2. In the second fertilization, the other sperm nucleus fuses with two polar nuclei in the ovule. The combination of the three nuclei makes a triploid cell that multiplies by mitosis. It eventually develops into the endosperm, which is the food storage tissue in the seed.

What is the fertilization process in flowering plants, and how are seeds formed? B. Following fertilization, the ovule develops into a seed, which consists of a seed coat, an embryo plant, and stored food. 1. The seed coat is a protective shell surrounding the embryo and endosperm. It protects the seed from drying and from physical injury. The seed coat helps in determining when conditions for germination, or the beginning of growth, are right. 2. The embryo plant is a little plant that eventually grows and develops into the mature plant. It remains dormant within the seed. It has a stem, root, and one or two seed leaves called cotyledons. Monocot embryos have one seed leaf and dicot embryos have two seed leaves. 3. The endosperm is the food storage tissue in the seed, particularly in monocots. Dicots store the bulk of their food in the two cotyledons. The food storage is necessary for the young seedling until it is able to manufacture its own food.

What is the fertilization process in flowering plants, and how are seeds formed? C. The ovary ripens and becomes the fruit. Fruit serves the purpose of protecting the seeds from drying and also aids in seed dispersal. D. Both the male sperm and female egg contribute genetic information to the new embryo plant. The union of sperm and egg results in new combinations of genetic information. These combinations produce new traits that add to the vigor of the offspring. The offspring that results from the new combination of genes are known as a hybrid.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? V. Germination is the end of the period of dormancy for the embryo plant that occurs when favorable conditions are present for growth and development of the seedling plant. The seedling plant has a root system, and leaves to produce the food necessary for the young actively growing plant.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? A. This process by which an embryo plant inside the seed changes into a developing seedling is known as germination. Many important crops are grown from seed. For example, corn, soybeans, cotton, and vegetables are all started from seeds. Some plants produce seeds that germinate immediately, others produce seeds that remain dormant, perhaps for years, until conditions are optimal for growth and survival. Optimal conditions for germination include favorable moisture, temperature, oxygen, and sometimes light.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? 1. The first important step in germination is usually the absorption of water. Water enters the seed by diffusion. The moisture triggers several important processes. Water also causes the seed to expand creates pressure within the seed. This pressure, known as turgor, causes the rupturing of the tough seed coat. The primary root, or radicle, emerges through the ruptured seed coat.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? 2. Water stimulates the production of plant hormones that signal the seed to convert stored food to energy for the embryo plant. In addition, growth hormones are behind the growth of the radicle that begins absorbing water and nutrients for the embryo once outside the seed. 3. Seeds germinate at a wide range of temperatures. Some plants require very warm germination temperatures, and other plants must have cool temperatures. However, the optimum temperature range for most seeds is between 65°F and 80°F.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? 4. All seeds need oxygen to germinate. Oxygen is necessary for cellular respiration. It is important that the soil not be so wet that it restricts the availability of oxygen. Lack of oxygen may result in the death of the embryo plant within the seed. 5. Seeds of some plants need exposure to light before they will germinate. Seeds of other plants do not need light to germinate or germinate poorly when exposed to light.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? B. Two additional mechanisms affect germination in certain plant seeds. 1. The first is stratification, which is a required period of cold temperature. This is especially important for plants that produce fruit in the fall. If the seeds of these plants germinated immediately, they would die from the cold winter temperatures. These plants survive by producing seeds that remain dormant and will not germinate until the warmer spring temperatures.

What is the process of seed germination, and what conditions are necessary for germination to occur in a seed? 2. The second mechanism is scarification, which causes the breakdown of the seed coat. The tough protective seed coat prevents diffusion of both water and oxygen into the seed. The seed coat must be broken before germination can begin. Plants have evolved many interesting methods to accomplish this task. The seed coat can be damaged or broken by the acid produced in an animal’s stomach; by soil microorganisms; by repeated freezing and thawing; by mechanical stress from the grinding in the gizzard of birds; and by being stepped upon, chewed etc.

REVIEW 1. What is sexual reproduction of plants and why is it important to plant survival? 2. What is the role of meiosis in the development of gametes? 3. What is pollination, and what are the different methods of pollination? 4. What is the fertilization process in flowering plants, and how are seeds formed? 5. What is the process of seed germination, and what conditions are necessary for germination to occur in a seed?