Lab 9: Take-Home Exercise on Flowers and Fruits

Transcription

1 BIOL 153L General Biology II Lab Black Hills State University Lab 9: Take-Home Exercise on Flowers and Fruits In this take-home lab, you will use information from your textbook, a Supplement PDF (Suppl.) prepared by your instructors, and online videos. Before starting, you are strongly encouraged to read Textbook pp , Lab 8 handout pp , and Suppl. pp Although you will not submit this handout for a grade, you will be given a 15-point quiz on the information at the beginning of the next lab be sure to work through all the questions! We recommend that you complete this lab in the order in which it is written. FLOWERS: As introduced in Lab 8, the term 'flower' refers to sexual reproductive structures of angiosperms. Parts of a simple flower were introduced in Lab 8 but in reality, flowers are highly variable in shape, size, and arrangement and sometimes a 'large flower' is many small flowers! The goal today is to learn principles of flower structure and anatomy and then apply this knowledge to a broad diversity of angiosperm species. In addition to using your textbook and online videos, your instructors have prepared a Supplement PDF with photographs and drawings; throughout this exercise, you'll be referred to pages of this document (e.g., Suppl. 1 = Supplement page no. 1). Review from Lab 8: Recall from Lab 8 that flowers are in general composed of 4 whorls: sepals, petals, stamens (male), and pistil (female). Stamens are composed of anthers and filaments; pistils are composed of ovary, style, and stigma (see Textbook Chapter 19, pp & Lab 8 handout pp ). Flowers with all four whorls (sepals, petals, stamens, pistil) are called complete. Flowers missing 1 whorls are called incomplete (see Textbook Chapter 19, p. 463 & Lab 8 handout pp ). Flowers with both stamens and pistils are perfect (= bisexual and hermaphroditic). Flowers with either stamens or pistils but not both are imperfect (= unisexual) (see Textbook, Chapter 19, p. 463 & Lab 8 handout pp ). The calyx and corolla can attach above or below the ovary. If the ovary is above the flower parts, the plant has a superior ovary (aka epigynous). If the ovary is below the flower parts, the plant has an inferior ovary (aka hypogynous) (see Chapter 19, pp & Lab 8 handout pp ). Some new information about flowers: In flowers with radial symmetry (= regular or actinomorphic), components of a whorl are the same size and shape; any line drawn through the center will divide the flower into identical halves. In flowers with bilateral symmetry (= irregular or zygomorphic), one or more components of a whorl are different shapes; only one line will divide the flower into identical halves (Suppl. 2) (see Textbook Chapter 19, p. 465). Monoecious (latin, 'one house') species have separate male and female flowers on the same plant (i.e. male and female imperfect flowers). Dioecious ('two houses') species have male and female flowers on different plants. Hermaphroditic (aka bisexual) flowers have both male and female parts (Suppl. 3-4) (see Textbook Chapter 19, p. 463). Having reviewed the reviewed the information about flowers above and read pp in your textbook, please proceed to answer the following questions. 1

2 1. Examine the lily flower shown in the textbook (Fig. 19-6, p. 461). Identify the 4 whorls. Is the flower complete or incomplete? Does it have a superior or inferior ovary? 2. Examine image of Round-lobed Hepatica and read description (Textbook Fig. 19-4b, p. 459). No. of sepals = No. of petals = No. of stamens = No. of pistils = Radial or bilateral symmetry? 3. Examine image of Trillium erectum and read figure description (Textbook Fig. 19-3c, p. 459). No. of sepals = No. of petals = No. of stamens = No. of pistils = Monoecious, dioecious or hermaphroditic? 4. Examine image of Magnolia and read figure description (Textbook Fig. 20-5, p. 481). Identify the petals on Magnolia Identify the stamens on Magnolia Identify the styles on Magnolia 5. Examine image of Wintergreen and read figure description (Textbook Fig. 20-9a, p. 484). No. of petals = No. of stamens = No. of pistils = Radial or bilateral symmetry? Superior or inferior ovary? 2

3 6. Examine image of Chaparral Honeysuckle and read description (Textbook Fig. 20-9c, p. 484). Radial or bilateral symmetry? Superior or inferior ovary? 7. Examine image of oak flowers and read figure description (Textbook Fig , p. 463). Where are the male vs. female flowers on oak? How do you know this? Monoecious, dioecious or hermaphroditic? 8. Examine image of Holly flowers (Suppl. 5). Monoecious, dioecious or hermaphroditic? Where are the male and female parts? 9. Examine image of Squash flowers (Suppl. 6). Monoecious, dioecious or hermaphroditic? Where are the male and female parts? 10. Examine image of Corn flowers (Suppl. 7). Monoecious, dioecious or hermaphroditic? Where are the male and female parts? 11. Examine image of Christmas Cactus flower (Suppl. 8). Monoecious, dioecious or hermaphroditic? Is the Christmas Cactus flower haploid or diploid? Where are the male and female parts? 3

4 INFLORESCENCES: In addition to the variability in sizes and structures of flowers, there is variation in how flowers are arranged. Some flowers occur singly at the end of the stem and are thus called solitary. However, multiple flowers are often clustered together on a stem, and this is called an inflorescence. A pedicel is the stalk of an individual flower in an inflorescence. Many types of inflorescences occur in flowering plants but here we will introduce just a few of the simpler and most common types. Solitary: Spike: Raceme: Panicle: Umbel: Head (capitulum): A single flower attaches directly to the main stem. Multiple flowers attach directly to the main stem (no pedicel). Multiple flowers attach to the main stem by stalks (= pedicels). Multiple flowers attach to the main stem by several branches. Multiple flowers attach by their stalks (= pedicels) to one attachment point on the main stem. Multiple stalk-less small flowers cluster together densely to form a single flower-like structure. See your Textbook p. 461 for illustrations of these inflorescence types!!! Flowers such as dandelions and sunflowers have composite flowers each 'unit' on the head is an individual flower. Look at the dandelion images to understand the parts (Suppl. 9-10). Note that the anthers are fused and the style/stigma grows through the ring of fused anthers. The green leafy parts at the bottom of the flower head are not sepals they are bracts. Sepals are found at the base of individual flowers and is a modified feathery structure called the pappus. The corolla (petals) is fused at the base (see Textbook Chapter 20, Fig , p. 485). 1. Inspect images of dandelion (Suppl. 9-10). Locate the stigma, style, and ovary on the floret Locate the anther Locate the corolla (petals) and the sepals (aka pappus) Is the ovary superior or inferior? 2. Match the flowers shown in the PDF Supplement (Suppl ) to inflorescence type. Inflorescence types can be used more than once or not at all! (See Fig. 19-7, p. 461 for drawings that illustrate these inflorescence types.) Chokecherry Showy Milkweed Queen Anne s Lace Gumbo Lily Mullein Black-eyed Susan Solitary Spike Raceme Panicle Umbel Head 4

5 POLLINATION AND FERTILIZATION: In angiosperms, pollination is the transfer of pollen from an anther to a stigma. Sometimes the pollen is moved by an animal pollinator, other times it is moved by a non-living factor (e.g. wind). Fertilization occurs when gametes fuse to forma diploid zygote (see Lab 8 handout on page 9). Unlike animals, plants can t move to find a mate. However, they have evolved strategies to move their male gametophytes (aka pollen) that are very effective and often crazy! There is enormous variation in the size, shape, color, and odor of flowers (see Textbook, Chapter 20, pp ). Today you will watch Sexual Encounters of the Floral Kind, an award-winning video about plant sex; it was released by the BBC in Admittedly, it is a bit campy, but that adds to its appeal! Watch the video Sexual Encounters of the Floral Kind and answer questions below. Note that there are several versions of this video on YouTube! Make sure you watch the version that is 49:49 long and posted by Kim Parker it has the full video and highest image quality. Sexual Encounters video: 1. Wasps pollinate the Hammer Orchid of Australia. Explain how this happens. 2. How is grass pollen moved from an anther to a stigma? How does the feathery shape of grass stigmas help this process? 3. The video says it pays for flowers to 'advertise' to pollinators. What rewards do plants offer? 4. Nectar robbers 'cheat' they take the rewards offered by the plant but do not provide a service. Explain how this happens and give an example. 5

6 5. Some plants, such as ginger, intentionally use nectar to attract ants. Why would plants do this? (Hint, the ants are not pollinators; the preferred pollinators are birds.) 6. How does the water lily differ between its first and second day of life? Explain how this relates to pollination and maturation of female and male parts of the flower. 7. Besides insects, name three other groups of animals that pollinate plants. How do plants attract these 'alternative' pollinators? 8. Why do plants such as the corpse flower emit the scent of rotting flesh? 9. In the corpse flower, female flowers open first and attract blowflies; male flowers open several days later. Why is it an advantage not to have both male and female flowers open at the same time? 10. The Bucket Orchid captures male bees until it can stick something to the bee s body. What does it attach to the bee and why? 6

7 FRUITS: A fruit is the ripened ovary of a plant doesn t that sound appetizing? The seeds inside are the ripened ovules. Sometimes, accessory tissues will unite with the ovary as it matures. The primary functions of fruits are protecting seeds and aiding their dispersal. Animals may eat fleshy fruits and deposit seeds with feces fertilizer or hooked, almost velcro-like fruits may stick to fur and be carried unintentionally. Some fruits have cottony or winged extensions that carry them by the wind. There are many fruit types we will describe only a subset in today s lab. Please see the Textbook Chapter 20, pp , for further information about the structures and functions of fruits. Legume 1. Examine the diagram showing the development of a legume (pea/bean) fruit (Suppl. 14). a. Is this a cross-section or longitudinal section? b. Where are the ovules located? What is the relationship between ovules and seeds? c. What flower part does the pod represent? 2. Examine the legume flower (Suppl. 15). a. Identify the petals and sepals on the flower. b. Is this a superior or inferior ovary? Does the flower have radial or bilateral symmetry? 3. Examine the image of green beans (Suppl. 16). Cooks will almost always trim off the part labeled B. Sometimes, but not always, they will remove the part labeled A. What flower structures are these? (Compare Suppl. 16 to Suppl. 15) A = B = 7

8 Tomato As discussed in Lab 8, the ovary can be divided into multiple carpels. Locules are the spaces within the ovary where ovule/seeds occur; ovules/seeds attach to the placenta. (See image below.) 1. Examine the tomato flower and fruit images (Suppl. 17 & 18). a. Which image is a cross section and which is a longitudinal section? _ b. What are the leafy green structures at the top of the tomato? _ c. Identify the ovary and ovary wall. Is this a superior or inferior ovary? _ d. Identify the locules. How many locules are present in this fruit? _ Bell pepper 1. Examine the bell pepper fruit (Suppl. 19). a. Identify the locules. How many locules are present? _ b. Identify the placenta. (Interesting note this is nicknamed the membrane and is the hottest part on hot peppers.) Orange 1. Examine the orange fruit (Suppl. 20). a. Identify the ovary wall. What do we call this part of the orange? b. How many carpels are present in this orange? 8