CHAPTER 17 Plants, Fungi, and the Colonization of Land Modules 17.1 – 17.3

Plants and Fungi—A Beneficial Partnership Mutually beneficial associations of plant roots and fungi are common These associations are called mycorrhizae They may have enabled plants to colonize land

Citrus growers face a dilemma They use chemicals to control disease-causing fungi But these also kill beneficial mycorrhizae

Plants are multicellular photosynthetic eukaryotes 17.1 What is a plant? Plants are multicellular photosynthetic eukaryotes They share many characteristics with green algae However, plants evolved unique features as they colonized land

PLANT LEAF performs photosynthesis CUTICLE reduces water loss; STOMATA allow gas exchange STEM supports plant (and may perform photosynthesis) ALGA Surrounding water supports the alga WHOLE ALGA performs photosynthesis; absorbs water, CO2, and minerals from the water ROOTS anchor plant; absorb water and minerals from the soil (aided by mycorrhizal fungi) HOLDFAST anchors the alga Figure 17.1A

Unlike algae, plants have vascular tissue It transports water and nutrients throughout the plant body It provides internal support Figure 17.1B

17.2 Plants evolved from green algae called charophyceans PLANT EVOLUTION AND DIVERSITY 17.2 Plants evolved from green algae called charophyceans Molecular studies indicate that green algae called charophyceans are the closest relatives of plants Figure 17.2A, B

Cooksonia was one of the earliest vascular land plants Sporangia Figure 17.2C

17.3 Plant diversity provides clues to the evolutionary history of the plant kingdom Two main lineages arose early from ancestral plants

Radiation of flowering plants CENOZOIC Gymnosperms (e.g., conifers) Angiosperms Seedless vascular plants (e.g., ferns, horsetails) Bryophytes (e.g., mosses) Radiation of flowering plants MESOZOIC Charophyceans (a group of green algae) First seed plants Early vascular plants PALEOZOIC Origin of plants Figure 17.3A

One lineage gave rise to bryophytes These are plants that lack vascular tissue Bryophytes include mosses, which grow in a low, spongy mat Figure 17.3B

Vascular plants are the other ancient lineage Ferns and seed plants were derived from early vascular plants and contain xylem and phloem well-developed roots rigid stems

Ferns are seedless plants whose flagellated sperm require moisture to reach the egg Figure 17.3C

A major step in plant evolution was the appearance of seed plants Gymnosperms Angiosperms These vascular plants have pollen grains for transporting sperm They also protect their embryos in seeds

Gymnosperms, such as pines, are called naked seed plants This is because their seeds do not develop inside a protective chamber The seeds of angiosperms, flowering plants, develop in ovaries within fruits

CHAPTER 17 Plants, Fungi, and the Colonization of Land Modules 17.4 – 17.14

17.4 Haploid and diploid generations alternate in plant life cycles ALTERNATION OF GENERATIONS AND PLANT LIFE CYCLES 17.4 Haploid and diploid generations alternate in plant life cycles The haploid gametophyte produces eggs and sperm by mitosis The eggs and sperm unite, and the zygote develops into the diploid sporophyte Meiosis in the sporophyte produces haploid spores, which grow into gametophytes

Gametophytes (male and female) n Gametes (sperm and eggs) n Mitosis Mitosis Spores n Gametes (sperm and eggs) n HAPLOID Meiosis Fertilization DIPLOID Zygote 2n Mitosis Sporophyte 2n Figure 17.4

17.5 Mosses have a dominant gametophyte Most of a mat of moss consists of gametophytes These produce eggs and swimming sperm The zygote stays on the gametophyte and develops into the less conspicuous sporophyte

Sporophytes (growing from gametophytes) 5 Mitosis and development Sperm (n) (released from their gametangium) Spores (n) 1 Gametangium containing the egg (n) (remains within gametophyte) Gametophytes (n) Egg HAPLOID Meiosis Fertilization DIPLOID Sporangium Stalk 2 4 Zygote (2n) Gametophyte (n) 3 Mitosis and development Sporophytes (growing from gametophytes) Figure 17.5

17.6 Ferns, like most plants, have a dominant sporophyte Ferns, like mosses, have swimming sperm The fern zygote remains on the small, inconspicuous gametophyte Here it develops into the sporophyte

5 1 HAPLOID DIPLOID 2 4 3 Sperm (n) Mitosis and development Spores (n) Gametophyte (n) (underside) Egg (n) HAPLOID Fertilization Meiosis Sporangia DIPLOID 2 4 Zygote (2n) 3 Mitosis and development New sporophyte growing out of gametophyte Sporophyte (2n) Figure 17.6

17.7 Seedless plants formed vast “coal forests” Ferns and other seedless plants once dominated ancient forests Their remains formed coal Figure 17.7

Gymnosperms that produce cones, the conifers, largely replaced the ancient forests of seedless plants These plants remain the dominant gymnosperms today

17.8 A pine tree is a sporophyte with tiny gametophytes in its cones Sporangia in male cones make spores that develop into male gametophytes These are the pollen grains Sporangia in female cones produce female gametophytes

4 5 HAPLOID DIPLOID 3 1 6 2 7 Female gametophyte (n) Haploid spore cells in ovule develop into female gametophyte, which makes egg. 5 Egg (n) Male gametophyte (pollen) grows tube to egg and makes and releases sperm. Sperm (n) Male gametophyte (pollen grain) HAPLOID MEIOSIS Fertilization DIPLOID Scale Sporangium (2n) Ovule Seed coat Zygote (2n) 3 Pollination Embryo (2n) HAPLOID Pollen grains (male gametophytes) (n) Integument 1 Female cone bears ovules. 6 Zygote develops into embryo, and ovule becomes seed. MEIOSIS Seed 2 Male cone produces spores by meiosis; spores develop into pollen grains 7 Seed falls to ground and germinates, and embryo grows into tree. Sporophyte Figure 17.8

17.9 The flower is the centerpiece of angiosperm reproduction Most plants are angiosperms The hallmarks of these plants are flowers Pollen grains Anther Stigma CARPEL Ovary STAMEN PETAL Ovule SEPAL Figure 17.9A, B

The angiosperm life cycle is similar to that of conifers 17.10 The angiosperm plant is a sporophyte with gametophytes in its flowers The angiosperm life cycle is similar to that of conifers But it is much more rapid In addition, angiosperm seeds are protected and dispersed in fruits, which develop from ovaries

2 Haploid spore in each ovule develops into female gametophyte, which produces egg. Egg (n) Stigma 3 Pollination and growth of pollen tube Pollen grain Ovule Pollen tube 1 Haploid spores in anthers develop into pollen grains: male gametophytes. Sperm Pollen (n) HAPLOID Meiosis Fertilization DIPLOID 4 Zygote (2n) Seed coat Food supply Seeds 7 Ovary Seed germinates, and embryo grows into plant. Ovule Embryo (2n) 5 Seed Sporophyte 6 Fruit Figure 17.10

17.11 The structure of a fruit reflects its function in seed dispersal Fruits are adaptations that disperse seeds Figure 17.11A-C

17.12 Connection: Agriculture is based almost entirely on angiosperms Gymnosperms supply most of our lumber and paper Angiosperms provide most of our food Fruits, vegetables, and grains Angiosperms also provide other important products Medications, fiber, perfumes

Angiosperms are a major source of food for animals 17.13 Interactions with animals have profoundly influenced angiosperm evolution Angiosperms are a major source of food for animals Animals also aid plants in pollination and seed dispersal Figure 17.13A-C

17.14 Connection: Plant diversity is a nonrenewable resource 20% of the tropical forests worldwide were destroyed in the last third of the 20th century The forests of North America have shrunk by almost 40% in the last 200 years Figure 17.14

Some plants in these forests can be used in medicinal ways More than 25% of prescription drugs are extracted from plants Table 17.14

CHAPTER 17 Plants, Fungi, and the Colonization of Land Modules 17.15 – 17.17

17.15 Fungi and plants moved onto land together Plants probably moved onto land along with mycorrhizal fungi These fungi help plants absorb water and nutrients They are mutualistic organisms

Other fungi are parasites predators decomposers of dead organisms Figure 17.15A-C

17.16 Fungi absorb food after digesting it outside their bodies Fungi are heterotrophic eukaryotes They digest their food externally and absorb the nutrients

A fungus usually consists of a mass of threadlike hyphae This forms a network called a mycelium Hypha Mycelium Figure 17.16A-B

Most fungi cannot move But they grow around and through their food very rapidly Figure 17.16C, D

17.17 Many fungi have three distinct phases in their life cycle Fungal spores germinate to form haploid hyphae

The dikaryotic mycelium forms a fruiting body, the mushroom In some fungi such as mushrooms, the fusion of hyphae results in a unique dikaryotic phase of their life cycle Each cell contains two haploid nuclei from different parents The dikaryotic mycelium forms a fruiting body, the mushroom This structure contains specialized cells in which the nuclei fuse These diploid cells then undergo meiosis, producing a new generation of spores

Fusion of haploid nuclei 2 Diploid nuclei 3 Spores released 1 Fruiting body (mushroom) Fusion of haploid nuclei Meiosis Haploid nucleus DIPLOID Spore HAPLOID DIKARYOTIC 4 Germination of spores and growth of mycelia 6 Growth of dikaryotic mycelium 5 Fusion of two hyphae of compatible mating types Figure 17.17

CHAPTER 17 Plants, Fungi, and the Colonization of Land Modules 17.18 – 17.20

17.18 Lichens consist of fungi living mutualistically with photosynthetic organisms Lichens are associations of algae or cyanobacteria with a network of fungal hyphae The fungus receives food in exchange for housing, water, and minerals Algal cell Fungal hyphae Figure 17.18A, B

Lichens survive in hostile environments They cover rocks and frozen tundra soil Figure 17.18C

17.19 Connection: Parasitic fungi harm plants and animals Parasitic fungi cause disease Dutch elm disease Corn smut Athlete’s foot Figure 17.19A-C

17.20 Connection: Fungi have an enormous ecological and practical impact Numerous fungi are beneficial Many are important in the decomposition of organic material and nutrient recycling

Fungi are also important as food Mushrooms are the fruiting bodies of subterranean fungi Yeasts (unicellular fungi) are essential for baking and beer and wine production Fungi are used to ripen certain cheeses Figure 17.20A

Some fungi produce antibiotics Penicillin was the first antibiotic to be discovered Staphylococcus aureus Penicillium Zone of inhibited growth Figure 17.20B

CHAPTER 17 Extra Photographs Part A

Mycorrhizae Figure 17.0x

Phloem and xylem in a Polypodium stem cross-section Figure 17.1x1

Phloem and xylem in a close-up of a Polypodium stem cross-section Figure 17.1x2

Chara Figure 17.2Bx

Sphagnum moss Figure 17.3x1

Sphagnum “leaf” light micrograph Figure 17.3x2

“Leafy” liverwort, Porella Figure 17.3x3

“Thalloid” liverwort, Pallavicinia lyellii Figure 17.3x4

Hornwort Figure 17.3x5

Lycophyte Figure 17.3x6

Horsetail Figure 17.3x7

CHAPTER 17 Extra Photographs Part B

Moss life cycle Figure 17.5x1

Moss sporangium (SEM) Figure 17.5x2

Mature fern Figure 17.6x1

Fern sorus Figure 17.6x2

Fern sporangium Figure 17.6x3

Mature fern sporangium Figure 17.6x4

Germinating fern spore Figure 17.6x5

Fern gametophyte Figure 17.6x6

Fern archegonia, a maidenhair fern Figure 17.6x7

Fern sporophytes emerging from gametophytes Figure 17.6x8

Fern spore Figure 17.6x9

Douglas fir Figure 17.7x

Frasier fir, Abies fraseri Figure 17.8x1

Male pine pollen cones Figure 17.8x2

CHAPTER 17 Extra Photographs Part C

Pollen cone, longitudinal section, light micrograph Figure 17.8x3

Pine pollen, light micrograph Figure 17.8x4a

Single pine pollen, light micrograph Figure 17.8x4b

Female pine cones Figure 17.8x5

Ovulate pine cone, longitudinal section, light micrograph Figure 17.8x6

Pine ovulate scale, light micrograph Figure 17.8x7a

Pine sporangium section with spores Figure 17.8x7b

Pine embryo Figure 17.8x8

Pollen grains, SEM Figure 17.10x

Winged seed from a white pine Figure 17.11x1

Seed dispersal Figure 17.11x2

Deforestation Figure 17.14x1

Slash and burn forest Figure 17.14x2

Pine farm Figure 17.14x3

Soil plate Figure 17.15x

Septate and nonseptate hyphae Figure 17.16Dx

CHAPTER 17 Extra Photographs Part D

Amanita Figure 17.16x1

Coprinus comatus, Shaggy Mane (Basidiomycota) Figure 17.16x2

Grevilles bolete Figure 17.16x3

Morel Figure 17.16x4

Stinkhorn, Mutinus ravenelii Figure 17.16x5

Trametes versicolor, Turkey Tail Figure 17.16x6

Tremella messenterica, Witch's Butter Figure 17.16x7

Pilobolus aiming its sporangia Figure 17.16x8

Aspergillus Figure 17.16x9

Mushroom gills and basidia Figure 17.17x1

Apothecium Figure 17.17x2

Mature asci Figure 17.17x3

Lichen anatomy, a section through foliose lichen shows the upper cortex, algal zone, medulla, lower cortex, and rhizines Figure 17.18x

Botrytis on strawberries Figure 17.19x

Moldy orange with Penicillium Figure 17.20x