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BIO 1
Section 3 Dr. Pablo Delis Student Name 10/8/
Plants 3- Angiosperms: Flowers, Fruits, Seeds and Seedlings
In this lab, the student will learn about the structure and functions of flowers, fruits, seeds, and seedlings. Students should be able to identify major parts of a flower, write a floral formula, recognize types of fruits and be able to use a dichotomous key, relate fruit structure to floral structure, see how morphology of flowers is related to possible methods of pollination, see how morphology of fruits is related to possible methods of seed dispersal, and distinguish between monocot and dicot seed and seedling structures. The list of defined vocabulary terms is on the attached sheet. Only Angiosperms have flowers which they use as reproductive structures. They are the flowering plants and make up the Phylum Anthophyta, which is characterized by having seeds in a container. The container is the pistil which becomes the fruit. The fruit functions in the dispersal of seeds, each of which contains an embryo, or new plant. To learn about flower structure, students will get a Peruvian Lily, Alstroemeria , flower. The instructor will point out the structure found in the outline. Students will summarize observations by writing a floral formula. After the student learns the structures, he will get another kind of flower and go through the outline identifying structures on his own and write a floral formula for the Yucca.
Floral appendages occur in successive groups or whorls. Many kinds of flowers have a perianth of two kinds of parts, which differ in location and appearance. The calyx is composed of sepals, the outer group, and are usually green. The corolla is composed of petals, the inner group, and is usually not green. The androecium is composed of one or more stamens, each with a filament and anther. The filaments is the stalk like lower portion and the anther contains the pollen sacs filled with pollen grains. Each pollen grain produces two sperm cells. The gynoecium has three parts, the stigma, the style, and the ovary. The stigma is the receptive tip of a pistil, on which pollen germinate to form pollen tubes, which carry sperm cells to the ovule. The style is the narrow region between the stigma and ovary. The ovary is a hollow structure with one or more cavities called locules. It becomes the pericarp, or fruit wall, after fertilization and contains one or more ovules, which become the seeds after fertilization. Each ovule contains a single microscopic egg cell which would be fertilized by one of the two sperm cells in the pollen tube that enters the ovule. Categories of symmetry refer to the perianth. Bilateral symmetry mens one plane of symmetry while radial symmetry means three or more planes of symmetry. Bisexual, or perfect, flowers contain both androecium and gynoecium. Hermaphroditic species bear only perfect flowers. Unisexual, or imperfect, flowers contain either androecium or gynoecium. Monoecious species are species in which each plant produces both staminate and pistillate flowers, such as corn. Dioecious species are species in which each plant produces either staminate or pistillate flowers. Polygamous species are species in which the plants have some combination of unisexual and bisexual flowers. Floral tubes appear when one or more whorls of floral appendages are basally
dichotomous key to some common fruit types. The student is to use the key to identify the types of fruits provided in the lab. The lab then focuses on seed structure. A seed is a mature ovule with an embryo. The seeds of some kinds of plants also contain endosperm, a food tissue for the growth of the embryo, and an outer protective covering called a seed coat. The first type of seed that will be examined is a bean seed. The student is to look at both a dry and previously soaked bean seed. He is to observe and identify the hilum, an elliptical scar along the concave edge where the seed was once attached to the pod or ovary, and he micropyle, a tiny opening where the pollen entered the ovule. After that, the student is to dry and squeeze the seed. A drop of water should exude through the micropyle. Then, the student should peel the seed coat away from the embryo and split the seed into two halves, which are cotyledons, or "seed leaves." flowering plants can be classified as monocots or dicots depending on whether they have one or two cotyledons. Next, the student should locate the axis of the embryo. This consists of a long hypocotyl, which is the transition between the shoot apex at the upper end and the radicle, or root apex, at the lower end. The shoot apex will form the shoot (leafy stem) of the plant while the radicle will form the root system. The student should also locate these structures in a peanut. The seed coat surrounds the seed and protects the embryo. The seed coat is often modified to control water entry or to facilitate dispersal of the seed by air, water, or animals. The next type of seed the student will examine are soaked corn grains. First, the student should peel off the tough, skin-like covering. This is a combination of the pericarp (ovary wall) plus the seed coat. Then the student should observe the embryo on one side of the grain. The remainder of the grain consists of
endosperm. Next, the student should cut the grain in half lengthwise with a razor blade, right down the middles of the embryo and observe the single cotyledon, the shoot apex, and the root apex. The student is then instructed to stain the cut surface with iodine to test for starch. Then the student should observe soaked, cut grains that have been treated with tetrazolium chloride solution. Tetrazolium is a dye used to test for active respiration. When the tissue is active, it will reduce tetrazolium turning the colorless dye pink. The final part of the lab is an optional part on seedlings. The student should observe the bean and corn seedlings and compare the seedlings and complete the provided table which contains: cotyledon number; cotyledons: above or below ground; hypocotyl: long or short; epicotyl: long or short; and first leaves above cotyledons: alternate or opposite.
