Angiosperms

1. Angiosperms Chapter 25

2. Angiosperms • Means “seed within a vessel” or “enclosed seed” • Ovules are enclosed within an ovary • Flowering plants • Dominate the earth’s vegetation

3. Origin of Angiosperms • First angiosperm fossils from early Cretaceous period limited to microfossils such as pollen grains and bits of stem or leaf cuticle • Mid-Cretaceous period numerous macrofossils such as leaves, stems, flowers, fruits, seeds

4. Key Innovations of Angiosperms • Improved vascular system • Large, relatively thin-walled vessels, tracheids in xylem for more efficient water transport • Sieve-tube members associated with companion cells in phloem • Larger diameter sieve-tube members and larger sieve pores increased efficiency of sugar transport • Fruit • Aids in dispersal of seeds

5. Key Innovations of Angiosperms • Flower • Functions • Aids in pollination • Protects developing seeds • Disperses mature seeds • Thought to be modified branch whose leaves became sepals, petals, stamens, and carpels

6. Angiosperm Rise to Dominance • Angiosperms very abundant in fossil record of late Cretaceous period • Humans played role in plant distribution and evolution during Quaternary period • Protoagriculture • Did not sow seeds in geometric patterns and till the land • Used fire, pruning, selective harvesting, and sowing without cultivation

7. Angiosperm Rise to Dominance • “Root” crops cassava (Manihot esculenta) and taro (Colocasia esculenta) cultivated in southeastern Asia as early as 15,000 years ago • Earliest archeological evidence of seed agriculture goes back 11,000 years • Humans accidentally domesticated and favored evolution of weeds

8. Angiosperm Rise to Dominance • In exploration of new lands, humans brought along domesticated plants, companion weeds, and sometimes ornamentals • Weeds and ornamentals displaced native species from some areas • Only most stressful habitats, such as alpine tundra, are free, or almost free of introduced species

9. Seedling Hypothesis • Proposed by William Bond as explanation of angiosperm dominance • Theory predicts that gymnosperms will be outcompeted everywhere except where angiosperm seedling competition is reduced, as in cold-temperate regions with nutrient-poor soils

10. Seedling Hypothesis

11. Novel Features of Angiosperm Life Cycle • Gametophyte generation became reduced • Location of ovule becomes hidden • There are two fertilization events (double fertilization) • Dispersal of seed is improved by its enclosure within a fruit

12. Basal Angiosperm Groups • Shrub, Amborella • Shrubs, vines, or trees of star anise and its relatives • Aquatic, herbaceous water lilies

13. Remaining Angiosperm Groups • Magnoliids • Monocots • Eudicots

14. Basal Angiosperms • Shared traits • Elongated vessels with slanted perforation plates (or else no vessels) • Radially symmetrical flowers with several to many free carpels and stamens • Stamens with broad, short, petal-like, or poorly differentiated filaments • Carpels with short or missing styles but with elongated stigmatic region

15. Basal Angiosperms • Shared traits • Pollen with a single aperture • Seeds with small embryos but with a significant amount of endosperm

16. Basal Angiosperms • Amborella trichopoda • Only living species of lineage that was probably the first to diverge • Found only on New Caledonia • Lacks vessels in its wood • Dioecious • Flowers have vestigial structures that suggest they evolved from plants that produced both pollen and ovules in same flower

17. Basal Angiosperms • Water lilies • 70 aquatic, rhizomatous wetland herb species • Leaves and flowers float • Large flowers with numerous tepals (colored flower parts not differentiated into petals and sepals), stamens, and carpels • Many wild species in North American ponds and lakes • Common ornamentals in garden pools

18. Basal Angiosperms • Star anise group • 100 species of plants • Vines, shrubs, or trees mostly of warmer climates • Some have medicinal value • Star anise (Illicium verum) most economically important • Source for spice and anise oil • DNA suggests group is monophyletic

19. Core Angiosperm Groups • Three subclades • Magnoliids • Monocots • Eudicots • Two can be distinguished by single characters • Monocots • A single cotyledon • Eudicots • Three-apertured pollen

20. Core Angiosperm Groups • Magnoliids • Ranges from herbs to trees • Great variety of morphological, anatomical, biochemical, and cellular variety • Typically are tropical and warm-temperate • Many are woody plants with simple leaves and pinnate venation

21. Core Angiosperm Groups • Magnoliids • Important spices and fruits • Nutmeg, sassafras, avocado, bay laurel, black pepper, pawpaw • Medicinals and ornamentals • Peperomia, betel pepper, wild ginger, pipe vine

22. Core Angiosperm Groups • Monocots • Usual characteristics • Single cotyledon • Parallel-veined leaves • Flower parts in threes • Sieve-tube members with plastids containing protein crystals • Stems with scattered vascular bundles • Absence of secondary growth • Primary roots that abort early and are replaced by adventitious root system

23. Core Angiosperm Groups • Monocots • About 65,000 species • Includes economically and ecologically important plants such as grains • Relationships within monocots poorly known • Analysis suggests clade called Alismatales forms basal lineage • Monocot groups • Alismatales, showy flower group, nonshowy flower clade (commelinid)

24. Core Angiosperm Groups • Monocots • Alismatales • Includes plants such as Philodendron, calla lily, Anthurium, taro, aquatic plants such as Hydrilla and Elodea

25. Core Angiosperm Groups • Monocots • Remaining two large groups • Showy flower group (lily) • Nonshowy flower group (commelinid clade)

26. Core Angiosperm Groups • Monocots • Showy flower group • May or may not be a clade • Includes yams, lilies, irises, amaryllis, hyacinth, daffodil, tulip, agave, asparagus, onion, orchids

27. Core Angiosperm Groups • Monocots • Commelinids • Nonshowy flower clade • Palms comprise basal lineage of clade • Unbranched trunk • Terminal tuft of compound or dissected leaves • Fruits called drupes

28. Core Angiosperm Groups • Monocots • Examples • Coconut palm – yields edible endosperm, oil pressed from dried coconut meal (copra), cordage (coir) from outer husk • Phoenix dactylifera – dates • Copernicia - carnauba wax • Elaeis – cooking oil • Areca – betel nuts • Raffia – basketry material

29. Core Angiosperm Groups • Monocots • Wind-pollinated plants • Subclade • Includes bromeliads as one of its basal lineages • Other examples • Bamboo and other grasses • Cattails • Rushes • Tules

30. Core Angiosperm Groups • Monocots • Ginger group (subclade) – has showy, insect-pollinated flowers • Zingiber – ginger • Elettaria – cardamom • Curcuma – turmeric • Musa – banana • Canna – canna • Maranta – maranta • Strelitzia – bird-of-paradise • Heliconia – large tropical genus

31. Core Angiosperm Groups • Eudicots • Defined by pollen with three apertures • Other characteristics • Net-veined leaves • Flower parts in fours or fives • Embryos with two cotyledons • Sieve-tube members with plastids containing starch grains

32. Core Angiosperm Groups • Eudicots • Other characteristics • Stem vascular bundles arranged in a ring • Stamens with slender filaments • Includes economically and ecologically important plants such as • Blueberries, buckwheat, cacti, carrots, coffee, grapes, hemp, legumes, melons, poppies, potatoes, roses, sandalwood, stone fruits, strawberries, sunflowers, tea, teak, tomatoes, walnuts

33. Core Angiosperm Groups • Eudicots • Basal lineages • Ranunculales • Proteales • Major clades • Rosids • Asterids • Caryophyllids

34. Core Angiosperm Groups • Eudicots • Basal lineage • Ranunculales • About 3,500 species • Mainly herbs in temperate latitudes • Lobed leaves, numerous flower parts, superior ovary position, seeds with small embryos • Most species contain poisonous alkaloids • Examples: • Ranunculus (buttercups), Anemone, Aquilegia (columbine), Delphinium (larkspur), Berberis (barberry), Papaver somniferum (opium poppy)

35. Core Angiosperm Groups • Eudicots • Basal lineage • Proteales • Especially abundant in Africa and Australia • Northern Hemisphere sycamores are also members • Typically are trees or shrubs with highly reduced, wind-pollinated flowers • Often grown as ornamental shrubs • Examples • Banksia, Grevillea, Hakea, sycamore

36. Core Angiosperm Groups • Eudicots • Major clade • Caryophyllid • Includes ice plants, carpetweeds, cacti, pinks, amaranths • Plants important to humans include • Beta (sugar beet), Spinacea (spinach), Portulaca (pursland), Rheum (rhubarb), Fagopy-rum (buckwheat), Amaranthus (amaranth) • Landscape plants • Bougainvillea, Dianthus (temperate carnations), Limonium (sea lavenders), many succulents

37. Core Angiosperm Groups • Eudicots • Major clade • Rosid • Largest clade • Most familiar members are legumes • Includes • Legumes, spurges, tropical melastomes, Australian eucalypti, roses, mustards • Economically important products • Fruits, nuts, vegetables, ornamentals, timber trees, spices and flavorings, fibers, dyes, drugs

38. Core Angiosperm Groups • Eudicots • Major clade • Rosid • Botanical oddities in clade • Insectivorous Venus flytrap • Parasitic mistletoes • Giant Rafflesia flowers – measure 1 m across

39. Core Angiosperm Groups • Eudicots • Major clade • Asterid • Contains some of the most highly specialized core angiosperms • Heaths, tomatoes, potatoes, peppers and relatives, mints, carrot, parsley and relatives, sunflowers, daisies • No major global food plants in clade • Does contain components and flavors of regional diets

40. Core Angiosperm Groups • Eudicots • Major clade • Asterid • Does contain components and flavors of regional diets • Artichoke, basil, coffee, tea, elderberry, endive and chicory, lettuce, mint, olive, oregano, peppers, paprika, chilies, potato, safflower, sage, sesame, sunflower oil, sweet potato, thyme, tomato, tomatillo, tobacco

41. Plant Geography • Branch of plant biology that describes distribution of plants over surface of earth • Studies possible explanations for how, why, or when patterns of distribution occurred • Stimulated by voyages of exploration in 17th, 18th, and 19th centuries

42. Plant Geography • Botanists who contributed to information include • Carl von Willdenow, Alexander von Humboldt, Johannes Schouw, August Grisebach, Alphonse de Condolle, Oscar Drude, Alolf Engler, George Marsh Asa Gray, Charles Darwin

43. Plant Geography • Dozen or so families of flowering plants commonly found on every continent except Antarctica • Plant geographers divided world into more than 30 global units • Each unit characterized by its own endemic plants plus unique mixes of more cosmopolitan lineages

44. Plant Geography • Sometimes environmental conditions, isolation of a place, and genetic potential of plants growing in region create unique and bizarre vegetation • Examples • Flora and vegetation of alpine zones on tropical African mountains such as Mt. Kilimanjaro in Kenya • Desert of Baja California

45. Plant Geography • Plant biogeographers benefited greatly from phylogenetic analyses • Cladograms can be used to • Infer centers of origin • Identify long-distance dispersal events • Investigate process of domestication in any groups