Safety Dissection tools are very sharp. Use appropriately and do not leave unattended in the presence of children.

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1 Plant Dissection Consider the lilies, how they grow: they labour not, neither do they spin. But I say to you, not even Solomon in all his glory was clothed like one of these. Luke 12:27 Introduction In today s experiment you will dissect a seed and a flower. The seed is able to lie dormant, often for years, until the conditions are right to support a young plant. Under the right environmental conditions, the seed will germinate into the root, stem and leaves which are important for plant growth in most plants. The flowers, fruits and seeds are part of the plant reproductive system. Learning Objectives: Dissection and Identification of key components of the seed Dissection and Identification of key components of the flower Materials Required: From Biology Kit Student Supplied Dissection tray and tools 3-4 dried beans (preferably lima beans or kidney beans Beaker white beans second best; ) Flowers 2 or 3 kinds * Text to refer to diagrams of seeds and flowers Ruler Dark and light paper or backgrounds for viewing Optional: Magnifying glass *Florists and stores will often donate browning or old flowers, which work fine for dissection. Best flowers to dissect include: Lily, tulip, alstroemeria (Peruvian lily), gladiolus. Avoid flowers having structures harder to discern: Daisy, aster, calla lily, rose, iris. Safety Dissection tools are very sharp. Use appropriately and do not leave unattended in the presence of children. Seeds The seed consists of three main parts: Seed coat, embryo, and endosperm. The endosperm, which nourishes the growing embryo may have one cotyledon (monocot) or two (dicot). You may or may not be able to see a more mature embryo in the lima bean. The plumule is the developing shoot from the epicotyl portion of the embryo, located between the cotyledons. The hypocotyl/radicle portion will appear as a comma. The radicle will emerge first to give rise to the root structure. The hypocotyl will emerge as the developing stem, carrying the plumule and developing leaves Catholic Initiatives in Math and Science, LLC All Rights Reserved 1

2 1. Prepare the Seeds: Place all but one of bean seeds in a beaker and cover with fresh room temperature water Cover the beaker and allow seeds to soak over night One dried bean will be reserved to compare to the soaked beans The next day, gently drain the water from beans, place on a paper towel on the dissection tray *Remove seed coat carefully it is easy to remove the embryo with the seed coat. 2. View outside seeds put all responses in Table 1: View the outside of each seed and describe the differences you see and feel Gently, remove the seed coat from the soaked bean and describe Compared to the inner portion, what do you observe about the durability of the seed coat? Try to remove the seed coat from the dried bean describe and compare Which was easier to remove? 3. View inside seeds put all responses in Table 1: Gently, pry apart the two halves of the soaked beans Choose the best specimen 1. Describe the endosperm How many are there? What are they called? Take the ruler and measure the length and width (in cm) and place measurements in Table 1 Observe and note any attachments to the embryo Observe and note any attachments to the seed coat 2. Describe the embryo Observe the shape of the plumule Locate and describe the epicotyl, hypocotyl and radicle How is the embryo attached to the endosperm? Take the ruler and measure the length and width (in cm) and place measurements in Table Catholic Initiatives in Math and Science, LLC All Rights Reserved 2

3 3. Describe the differences Pry apart the two halves of the dried bean Locate the plumule, epicotyl, hypocotyl and radicle Locate the endosperm Take the ruler and measure the length and width (in cm) and place measurements in Table 1 Describe the differences between the soaked and dried beans 4. Place the two halves of the soaked bean together: On which side of the bean is the embryo located? Is it on the rounded side of the bean? Is it near the hilum of the bean? 5. Continue on to the Flower Dissection Flowers The flower is the seed-factory of many plants. A flower contains both the female portion usually in the sheltered receptacle and a male portion along the outside. The female portion of a flower is called the Carpel which consists minimally of the following: Stigma (enlarged, sticky knob to capture pollen); a Style (a stalk that holds the stigma accessible to pollen, provides a pathway for the pollen to the ovary, allowing the ovary to remain sheltered in the stronger portion of the flower), and; Ovary (houses one or more ovules) The male portion is the Stamen which consists of the: Anther (houses microspores which develop into pollen), and; Filament (a stalk that hold the anther accessible to the elements which will disperse the pollen when mature. See figure below Catholic Initiatives in Math and Science, LLC All Rights Reserved 3

4 6. Observe the Outer, Posterior side of the Flowers Place observations in Table 2: Place the flowers side by side, with the posterior, or back-side showing Identify the following on each, noting number and color as appropriate: Bract (if available) Pedicel Receptacle Sepal Petals Next, detect structural differences between the flowers Monocots have flower parts in threes do any of the flowers have petals in threes? Eudicots have flower parts in fours or fives do any of the flowers have petals in fours or fives? How are sepals arranged? Are they simple leaf-like structures as shown above? Or, are they complex and multi-layered? Are they missing completely? What other structural differences do you detect? 7. Observe the Outer, Anterior side of the Flowers Place observations in Table 2: Turn the flowers over, with the anterior, or front-side showing Identify the following on each, noting number, color, state of maturity as appropriate: Carpel --Stigma --Style --Ovary Stamen --Filament --Anther Next, answer the following to detect color/structural differences between the flowers: How is the Stigma arranged in relation to the stamen? Above, below, or same level? To which structure(s) are the filaments attached? Describe the state of each Stigma: Sticky? Small and green? Filled with pollen? Describe the state of each Anther: Powdery? Small and green? Other? What other structural differences do you detect? Compare where the concentration of color occurs in each flower. Is the center around the ovule more deeply colored? Are there stripes leading from the petals to the center? Other combinations? Why may these colorations be important? * Now you will dissect the flowers carefully. As you do so, remove the parts and set them aside together in groups. Keep all the components of one flower together; keep petals with petals, stamen with stamen, etc Catholic Initiatives in Math and Science, LLC All Rights Reserved 4

5 8. Remove Petals, one Sepal Place responses in Table 2: Carefully, remove one sepal and set it aside: Are there color or structure differences? Remove all petals and group them together: Do the petals have different odors? Do coloration differences between flowers become clearer? What are the shapes of the 2 or 3 specimens round, heart-like, etc., Measure the length and width (in cm) and compare 9. Dissect the Stamen Place responses in Table 2: Gently, remove the stamen from each flower and group together Select the best stamen specimen from grouping and focus on those 2 or 3 Describe and compare the Anthers What are their shapes? Single-sided, Double-sided, or more complex? Color? Have they already released the pollen? If so, describe the appearance of the pollen. If possible, take a scalpel and open the anthers to describe the center. Describe and compare the Filaments Take the ruler and measure the length and width (in cm) Are there any notable differences between the filaments in the different flowers? 10. Dissect the Carpel Place responses in Table 2: Gently, remove the carpel from each flower and group together Select the best carpel specimen from grouping and focus on those 2 or 3 Describe and compare the Stigma What are their shapes? Single-sided, Double-sided, or more complex? Color? In what state of maturity are they? Have they become moist or sticky? Describe and compare the Style Is the style present? Measure and record the length and place in Table 2 Measure and record the width, just above the ovary. Describe and compare the Ovary Take the ruler and measure the length and width (in cm) Compare the sizes of the ovary in the specimens. Cut the Carpel: Very carefully, cut the carpel in half, long ways. Cut from the top of the stigma, through the style, and bisect the ovary. Pull the two halves apart 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 5

6 The ovary contains one or more hollow sections called Locules. Describe how many Locules you see within the ovary What do you observe within the locules? Do you observe the ovules located within the locules? Are the ovules mature? Is there only one ovule? Many ovules? What else do you observe upon dissection? 11. After completing the table, answer the questions in Data Analyses and Conclusions 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 6

7 Lab Report for: Step Table 1: Dissection of a Seed Student Observations (be specific; use botanical terms) Seed coat: Appearance; comparisons Endosperm: Measurements; #; what they are called; attachments to embryo; observations and descriptions Embryo: Measurements; description of plumule, radicle, hypocotyl; attachments to endosperm; other observations and descriptions Dry Seed vs. Soaked Seed: Describe the appearance and measurements of the dried seed vs. soaked seeds Embryo Placement: On which side of the seed will the radicle and hypocotyl emerge? Describe Catholic Initiatives in Math and Science, LLC All Rights Reserved 7

8 Table 2: Dissection of Flowers Step Flower 1 Flower 2 Flower 3 (optional) Posterior Flower: Bracet; Pedicel; Receptacle; Sepal; Petals Posterior Flower: Structural Differences Anterior Flower: Carpel; Stamen Anterior Flower: Structural Differences Petals/Sepal: Descriptions; Measurements; Differences Stamen: Anther: Observations; Differences Stamen: Filament: Observations; Differences Carpel: Stigma: Observations; Differences Carpel: Style: Observations; Differences Carpel: Ovary: Observations; Differences Data Analysis 1. Based on the structure and appearance of the seed coat, what function does it serve for the seed? That is, compare the structure with the function. 2. Where does the plant get its food once the seed has germinated? 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 8

9 3. Embryonic parts: What adult plant part(s) will the radicle become? What adult plant part(s) will the hypocotyl become? What adult plant part(s) will the plumule become?. 4. Name 3 characteristics observed in your flowers that help attract pollinators. 5. Based on your observations, how is the carpel able to capture and hold on to the small pollen grains blown on the wind from another plant? 6. Pollination and fertilization Describe where pollination and fertilization occur. What is pollination? What is fertilization? 7. Take one half of the dissected carpel and a fully an intact carpel stigma, style and ovary. If a pollen grain lands on the exterior of the stigma, describe how fertilization takes place on the interior of the ovary, several centimeters away. 8. Flowering plants undergo double fertilization. What is double fertilization? What do the results of double fertilization become? 2016 Catholic Initiatives in Math and Science, LLC All Rights Reserved 9