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The Green Machine Understanding the Seed Plants (Gymnosperms) 22 The Green Machine Understanding the Seed Plants (Gymnosperms) 22 To the Instructor The gymnosperms are more obvious to students than the nonvascular and seedless vascular plants. A stroll across campus should yield several species of gymnosperms, from pine trees to junipers. In this chapter, attempt to anchor the gymnosperms to students’ existing schema of these plants by using meaningful and interesting examples. This chapter can easily be modified to teach along with other chapters on plant diversity. The instructor can pick and choose activities from these chapters to meet the needs of the students. Topics for Discussion 7 At the beginning of this lab, review the objectives to the chapter. If this chapter is taught with other plant diversity chapters, cover the objectives and material for the other chapters. 7 Discuss the classification and basic evolution of the gymnosperms. 7 Discuss the phyla of the gymnosperms included in this chapter, providing specific examples, natural history, uses, life history, and anatomical information. 7 Discuss and bring in local specimens or photographs of the plants discussed in this chapter. 7 Discuss the environmental, industrial, and medical importance of the gymnosperms. Total Estimated Completion Time: 3 hours, 30 minutes 1 EXERCISE 22.1 Phylum Cycadophyta Estimated Exercise 22.1 Completion Time: 30 minutes Procedure 1 Macroanatomy of Cycas Estimated Procedure 1 Completion Time: 15 minutes Materials ❏❏ Dissecting microscope ❏❏ Leaf, pollen cone, microsporophyll, megasporophyll, and a seed from a living or preserved specimen of cycad ❏❏ Colored pencils Procedure 2 Microanatomy of Cycas Estimated Procedure 2 Completion Time: 15 minutes Materials ❏❏ Compound microscope ❏❏ Transverse or cross section of a microsporangiate cone (Triarch Microslides #10-8C-D), transverse or cross section of a megasporangiate cone (Triarch Microslides #10-8E-EE), unfertilized ovule, and fertilized ovule from a living or preserved specimen of cycad ❏❏ Prepared slides of a typical cycad species such as Cycas revoluta (Triarch Microslides #10-2A-D) or Zamia pumila (Triarch Microslides #10-8A-H) ❏❏ Colored pencils Check Your Understanding 1.1 What is the major means of pollinating cycads? Thrips and beetles serve as insect pollinators in cycads. 1.2 Describe the dioecious nature of cycads. Cycads are dioecious (having separate sexes) and produce distinct male pollen cones and female seed cones. The male pollen cones usually are elongated, and the female seed cones are rounded and may contain dozens of large seeds. 1.3 Why should one not eat cycad seeds? Although they are a rich source of starch, cycads should not be consumed because they contain large amounts of carcinogenic and neurotoxic chemicals. Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 2 EXERCISE 22.2 Phylum Ginkgophyta Estimated Exercise 22.2 Completion Time: 30 minutes Procedure 1 Macroanatomy of Ginkgo biloba Estimated Procedure 1 Completion Time: 15 minutes Materials ❏❏ Dissecting microscope ❏❏ Fresh or preserved stems and leaves of Ginkgo biloba ❏❏ Colored pencils Procedure 2 Microanatomy of Ginkgo biloba Estimated Procedure 2 Completion Time: 15 minutes Materials ❏❏ Compound microscope ❏❏ Prepared slides of Ginkgo biloba: a transverse or cross section of a short branch (Triarch Microslides #10-4AAAA), a microsporangiate strobilus (Triarch Microslides #10-4C), a longitudinal section of an ovule (Triarch Microslides #10-4EF), a longitudinal section of a seed with the seed coat removed (Triarch Microslides #10-4K), and a section of the ovule ❏❏ Colored pencils Check Your Understanding 2.1 Why are female ginkgo trees considered undesirable in urban areas? Female ginkgo trees are called stink bomb trees because their fruit is extremely foul smelling. 2.2 Sketch and describe a ginkgo leaf. Sketches will vary, but the leaves of Ginkgo biloba do not possess a midrib (central vein) and have dichotomous (forked) venation. Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 3 EXERCISE 23.3 Phylum Coniferophyta Estimated Exercise 23.3 Completion Time: 2 hours, 30 minutes Procedure 1 Macroanatomy of Conifers Estimated Procedure 1 Completion Time: 20 minutes Materials ❏❏ Dissecting microscope or hand lens ❏❏ Specimens of select conifers, such as pine, bald cypress, cedar, spruce, juniper, arborvitae, fir, and other specimens provided by the instructor ❏❏ Colored pencils Procedure 2 Macroanatomy of Conifer Cones Estimated Procedure 2 Completion Time: 20 minutes Materials ❏❏ Dissecting microscope ❏❏ Colored pencils ❏❏ White paper ❏❏ Sterile microscope slides ❏❏ Dropper ❏❏ Water ❏❏ Coverslip ❏❏ Pollen cones (male/staminate) from select conifers ❏❏ Seed cones (female/ovulate) from select conifers ❏❏ Seeds from select conifers Answers to Procedural Questions 6 Drop a seed from Pinus sp. from above your head. Describe the action as it falls. It falls to the ground in a twirling, helicopter blade type motion. Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 4 Procedure 3 Microanatomy of Conifer Cones Estimated Procedure 3 Completion Time: 20 minutes Materials ❏❏ Compound microscope ❏❏ Microscope slides of longitudinal section through the tip of a microsporangiae cone of Pinus sp., pollen from Pinus sp., transverse and longitudinal sections of the seed cones of Pinus sp., and ovule of Pinus sp. ❏❏ Colored pencils Procedure 4 Conifer Seed Germination Estimated Procedure 4 Completion Time: 30 minutes Materials ❏❏ Pine seeds ❏❏ Pine seedlings ❏❏ Sand ❏❏ Sectioned potting container with drains ❏❏ Potting soil ❏❏ Small pot ❏❏ Pencil with eraser Procedure 5 Macroanatomy of Conifer Needles and Leaves Estimated Procedure 5 Completion Time: 10 minutes Materials ❏❏ Dissecting microscope ❏❏ Selected specimens of conifer needles and leaves ❏❏ Colored pencils Answers to Procedural Questions 3 If your conifer needle is fresh, smell your specimen. Describe the smell. What is responsible for the distinct smell? Conifers have an intense, sharp, fruity smell. The smell is described by many as a clean smell and is caused by terpines. Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 5 Procedure 6 Microanatomy of Conifer Needles and Leaves Estimated Procedure 6 Completion Time: 10 minutes Materials ❏❏ Compound microscope ❏❏ Prepared microscope slide of the transverse section of a needle from Pinus sp. ❏❏ Colored pencils Procedure 7 Microanatomy of Conifer Stems Estimated Procedure 7 Completion Time: 25 minutes Materials ❏❏ Compound microscope ❏❏ Prepared microscope slide of transverse section through the stem of a young conifer, transverse section through the stem of Pinus sp. (Triarch Microslides #10-6A-DM), radial longitudinal section through the phloem of Pinus sp., and radial longitudinal section through the xylem of Pinus sp. ❏❏ Colored pencils Procedure 8 Conifer Stem Aging Estimated Procedure 8 Completion Time: 15 minutes Materials ❏❏ Cross section of a tree trunk Answers to Procedural Questions 3 Determine the age of your specimen. Answers will vary depending on specimen. 4 Examine the annual rings. Was the tree exposed to any interesting conditions? How do you know, and when in the life of the tree did it occur? Answers will vary depending on specimen. Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 6 Check Your Understanding 3.1 Compare and contrast softwood and hardwood, and provide examples of each. The wood of conifers is considered softwood, and the wood of angiosperms is considered hardwood. Softwood is composed primarily of tracheids and rays (lateral conduction structures), whereas hardwoods have tracheids, rays, and vessel elements. Softwoods are relatively light and usually less dense than hardwoods, with the exceptions of balsa and basswood. Softwoods contain vertical resin canals that occur either naturally or as a result of injury. Generally, softwoods are easier to work with in the building and furniture industry. Softwoods also are used in the production of paper, medium density fiberboard (MDF), and the majority of plywood. Hardwood is used in fine furniture and flooring and typically is more expensive and durable than softwood. 3.2 What is the function of the cork cambium? The cork cambium found in gymnosperms and angiosperms is responsible for secondary growth that becomes the epidermis in roots and stems. 3.3 Compare and contrast springwood and summerwood. Springwood is lighter in color, with larger cells. Summerwood is darker in color, with smaller cells. In many species, the age of a tree can be determined by counting the summerwood bands. 3.4 What is the function of the heartwood? Heartwood is the darker inner xylem tissue, which serves primarily as a reservoir for gum, resin, and tannin. 3.5 Describe the location of the xylem and phloem in your specimen. Answers will vary, but xylem is found between the pith and cambium, and phloem is found between the cambium and cortex. 3.6 List several uses of softwood and hardwood. Softwood: paper, fiberboard, plywood Hardwood: flooring and fine furniture Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 7 Chapter 22 Review 1 Compare and contrast the seeds of gymnosperms and angiosperms. Gymnosperm and angiosperm seeds are distinctly different. The term gymnosperm literally means “naked seed leaf.” In these plants, the seeds are not enclosed in an ovule, and they mature on the surface of a cone scale, such as that of a pine cone. The nutritive material in
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