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Home , Conifer, Cycad, Gnetophyta

The Green Machine Understanding the () 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 of gymnosperms, from to . 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 diversity. The instructor can pick and choose activities from these chapters to meet the needs of the students.

Topics for Discussion

77 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. 77 Discuss the classification and basic evolution of the gymnosperms. 77 Discuss the phyla of the gymnosperms included in this chapter, providing specific examples, natural history, uses, history, and anatomical information. 77 Discuss and bring in local specimens or photographs of the plants discussed in this chapter. 77 Discuss the environmental, industrial, and medical importance of the gymnosperms.

Total Estimated Completion Time: 3 hours, 30 minutes

1 Exercise 22.1 Cycadophyta Estimated Exercise 22.1 Completion Time: 30 minutes

Procedure 1 Macroanatomy of

Estimated Procedure 1 Completion Time: 15 minutes

Materials ❏❏ Dissecting microscope ❏❏ , cone, microsporophyll, megasporophyll, and a seed from a living or preserved specimen of ❏❏ 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 , and fertilized ovule from a living or preserved specimen of cycad ❏❏ Prepared slides of a typical cycad species such as (Triarch Microslides #10-2A-D) or pumila (Triarch Microslides #10-8A-H) ❏❏ Colored pencils

Check Your Understanding

1.1 What is the major means of pollinating ? and serve as in cycads.

1.2 Describe the dioecious nature of cycads. Cycads are dioecious (having separate ) 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 .

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 biloba

Estimated Procedure 1 Completion Time: 15 minutes

Materials ❏❏ Dissecting microscope ❏❏ Fresh or preserved stems and of ❏❏ 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 (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

Estimated Procedure 1 Completion Time: 20 minutes

Materials ❏❏ Dissecting microscope or hand lens ❏❏ Specimens of select conifers, such as pine, bald cypress, cedar, , , arborvitae, , and other specimens provided by the instructor ❏❏ Colored pencils

Procedure 2 Macroanatomy of 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

Estimated Procedure 4 Completion Time: 30 minutes

Materials ❏❏ Pine seeds ❏❏ Pine ❏❏ ❏❏ 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 of Pinus sp. ❏❏ Colored pencils

Procedure 8 Conifer Stem Aging

Estimated Procedure 8 Completion Time: 15 minutes

Materials ❏❏ Cross section of a 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 and hardwood, and provide examples of each. The of conifers is considered softwood, and the wood of angiosperms is considered hardwood. Softwood is composed primarily of and rays (lateral conduction structures), whereas hardwoods have tracheids, rays, and vessel elements. are relatively light and usually less dense than hardwoods, with the exceptions of balsa and basswood. Softwoods contain vertical 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 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. 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 gymnosperms accumulates prior to fertilization. In angiosperms, the nutritive material is stored only after fertilization. In angiosperms, occurs, producing an and a nutritive endosperm. The seeds of angiosperms are encased in a fruit. In both cases, the parental sporophyte generation provides nutrition to potential offspring, giving them a distinct advantage over seedless plants.

2 How have seed plants influenced the development of humans? Seed plants provide food for and humans. Neolithic human societies approximately 12,000 years ago used seed plants, such as wheat, figs, corn, and squash, and shaped their destinies through artificial selection.

3 What are the general characteristics of gymnosperms? The gymnosperms are generally characterized by lacking and fruits; the seed develops in association with a scale that exists on a cone.

4 List and give examples of each phylum of gymnosperms. Cycadophyta— palms Ginkgophyta—ginkgo trees — spp. Coniferophyta—pine trees and bald cypress

5 What are some unique characteristics and facts about Ginkgo biloba? The leaves of do not possess a midrib (central vein) and have dichotomous (forked) venation. The tree is (shedding leaves yearly), and the leaves turn bright yellow before abscission (shedding) in the fall. Ginkgo trees have two types of : short shoots, or spurs, appear knobby and feature clusters of leaves and immature . The leaves of slow-growing short shoots usually are unlobed or slightly bilobed. The leaves of fast-growing long shoots usually are deeply bilobed. Ginkgo trees are dioecious, having separate sexes. After ­fertilization, form and the integument develops into an extremely bad-smelling, fleshy seed coat.

6 What is unique about sp.? The Welwitschia is represented by one member, Welwitschia mirabilis, native to the extremely dry Namib and Mossamedes of southwestern . It is rather strange in appearance, possessing a long taproot along with a short stem that usually supports two permanent strap-like leaves. Welwitschia mirabilis may live for more than 1,000 years.

7 What characteristic do members of phylum Gnetophyta have in common with angiosperms? The gnetophytes are unique gymnosperms because their wood contains conducting cells, known as vessel elements, similar to the angiosperms, or flowering plants. In addition, gnetophytes such as angiosperms undergo double ­fertilization. It is thought that the gnetophytes perhaps are ancestral to the angiosperms.

8 Describe reproduction in 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. The of cycads are the largest living in the world and may possess more than 10,000 flagella. The scales surrounding the sometimes colorful seeds may be covered by feltlike hairs that can be highly irritating to the skin. Thrips and beetles serve as insect pollinators in cycads.

Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 8 9 Sketch and label a transverse section of a tree trunk. Sketches will vary, but refer to Fig. 22.56 (p. 369) of the lab manual. Make sure students include bark, heartwood, springwood, summerwood, vascular cambium, and pith.

10 Discuss the economic importance of conifers. Some conifer species are sources of , paper, wood alcohol, , and resin. Several species, such as juniper and yew, are ornamentals. In this regard, bonsai conifer plants are popular, along with spruce and fir Christmas trees. Oils from conifers are used in soaps and air fresheners. Humans eat some seeds, such as pine nuts. Some conifer products, such as taxol (a cancer treatment), are used in medicine.

11 Trace the life cycle of a pine tree. Sketches will vary. Most conifers, including pine, produce two distinct types of cones as a sporophyte, the micro­sporangiate pollen cone (male) and the ovulate seed cone (female). Pollen develops within the micro- sporangia of the pollen cone. In Microsporangiate the seed cone, the megasporangia (male) cone

produce eggs in the archegonia, Longitudinal forming the ovule. Pollen enters Young section through the mature seed cone and forms sporophyte (2n) Mature microsporangiate cone sperm cells ultimately delivered () sporophyte (2n)

to the waiting egg by means of Seed coat a . The egg is fertilized Embryo and forms a . The seed (2n) Ovulate cone closes and increases in size Megagametophyte (n) (female) as the seeds develop. cone

Fertilized egg (zygote) (2n) Meiosis MicrMicrosporophyllosporophyll

MicrMicrosporangiumosporangium Ovule with Fertilization FunctionalFunctional megasporocytemegasporocyte (2n)) Meiosis megaspormegasporee ((nn))

GerminatingGerminating pollen pollen graingrain (mature (matur malee male MicrMicrosporeospore )gameophyte) tetradtetrad ( n(n) ) Mature pollen grain (n) Sperm (n) Mature pollen grain (n) Sperm (n) (immature(immature malemale gametophyte)gametophyte)

Chapter 22 | The Green Machine: Understanding the Seed Plants (Gymnosperms) 9