Lecture Outline - Chapter 29

29.1. Characteristics of Plants (p. 566)

1. Plants in kingdom Plantae are multicellular eukaryotes with well-developed tissues. (Fig. 29.1)
2. Probably share common ancestor with green algae.
   • a. Both utilize chlorophylls a and b and carotenoid pigments during photosynthesis.
   • b. Both use starch as primary food storage.
   • c. Both cell walls contain cellulose; form cell plate during photosynthesis.
3. Plants contrast with aquatic green algae. (Table 29.1)
   • a. Plants live in wide variety of terrestrial habitats that provides more light, carbon dioxide, and oxygen.
   • b. Only plants protect reproductive cells and later the embryo within plant bodies.
   • c. Plants use roots to obtain water from substrata.
   • d. Plant leaves and stems conserve water with waxy coating.
   • e. Plant stomates open and close to admit gases and conserve water.
   • f. Plant's vascular system transports water and provides rigid skeleton.
4. Alternation of Generations
   • a. Two-generation life cycle alternates between:
     • i. Sporophyte is diploid generation; produces haploid spores by meiosis in structures called sporangia; spores are haploid and develop directly into gametophytes.
     • ii. Gametophyte is haploid generation; produces gametes (egg and sperm) that unite to form zygote (2N) that develops into sporophyte.
   • b. In plants, all plants have both generations, one being dominant over the other, lasts longer, is larger and more conspicuous.
   • c. Shift occurs from bryophytes to seedless vascular plants to seed plants, with gametophyte originally dominant in bryophytes but sporophyte dominant in seed plants.
   • d. Solution to problem of developing on dry land involves:
     • i. Production of heterospores: microspores and megaspores.
     • ii. Microspore develops into pollen grain called microgametophyte (male gametophyte) that produces sperm.
     • iii. Pollen grains are dispersed by wind or insects to female gametophyte, the megagametophyte.
     • iv. Seed plants thus protect water dependent gametophytes in water independent sporophyte.
     • v. Pollen grain replaces flagellated sperm dependent upon water medium.
     • vi. Ovule becomes seed protecting embryonic sporophyte and stored food.

1. Bryophytes are nonvascular; all other plants have vascular tissue sometime in life cycle.
2. Three separate divisions include: hornworts, liverworts, and mosses.
3. Lack true roots, stems, or leaves with vascular tissues; structures are only rootlike, stemlike, or leaflike.
4. Gametophyte is dominant generation.
   • a. Flagellated sperm swim in water in vicinity of egg.
   • b. Sporophyte develops from zygote and is attached to and derives nourishment from gametophyte.
5. Lack of water transport system restricts bryophytes to small and low lying profile.
6. Sexual reproduction requires external moisture; thus occupy wet environments only.
7. Liverworts Are Bryophytes
   • a. In division Hepatophyta with 10,000 species.
   • b. Marchantia has a flattened, lobed body known as a thallus, smooth on top and with rootlike rhizoids projecting down into soil.
   • c. Asexual reproduces by forming gemmae, groups of cells in gemmae cups on upper surface of thallus and which can start new plants.
   • d. Sexual reproduction involves umbrella-like gametophores that produce gametes.
8. Mosses Are Bryophytes
   • a. In division Bryophyta with 12,000 species.
   • b. Wide ranging from tropics to Antarctic to deserts to bogs.
   • c. Although need water to live, can store water or dry out until rainfall comes.
   • d. Can fragment and any part can produce leafy shoots.
   • e. Life Cycle of Moss (Fig. 29.4)
     • i. Gametophyte has two stages:
       - Alga-like protonema is branching filament of cells.
       - Upright leafy shoots grow from protonema after three days.
       - Rhizoids anchor shoots that bear antheridia and archegonia.
       - Male antheridia has outer sterile cells and inner cells that become swimming sperm.
       - Megagametophyte produces an egg within the archegonium.

       ii. Sporophyte grows from the gametophyte.

       - Consists of a foot, a stalk, and an upper capsule, or sporangium.

       - Where haploid spores are produced.

       - Dispersal of new organisms is achieved by windblown spores.
9. Importance: Rock Colonizers and Peat
   • a. Sphagnum is bog or peat moss.
     • i. Holds water in soil used in gardening.
     • ii. Dead dried peat used as fuel.

1. Vascular plants include ferns and allies, gymnosperms, and angiosperms.
2. Vascular tissues consists of:
   • a. Xylem: conducts water and minerals up from soil.
   • b. Phloem: transports organic nutrients from one part of plant to another.
3. Therefore they have true roots, stems, and leaves.
   • a. Roots absorb water.
   • b. Stem conducts water to leaves.
   • c. Xylem also provides structural support.
   • d. Leaves have waxy cuticle to hold in water; stomate openings can be regulated.
4. Sporophyte generation is dominant.
   • a. This generation has strong-walled vascular tissue to support the plant.
   • b. Is diploid, which can mask a faulty gene.
5. Seedless vascular plants include: whisk ferns, club mosses, horsetails, and ferns.
   • a. Dispersal is by windblown spores.
   • b. Large gametophyte is independent of sporophyte for nutrition, but . . .
   • c. Flagellated sperm from antheridia swim in external water to archegonia to fertilize egg.
   • d. Therefore terrestrial sporophyte cannot grow far from water dependent gametophyte.
   • e. Seedless vascular plants formed swamps of Carboniferous Period; compressed to form coal that is mined and burned today.
6. Psilophytes Are Whisk Ferns
   • a. In division Psilotophyta.
   • b. Example is Psilotum (Fig. 29.6)
   • c. Resemble extinct rhyniophytes.
     • i. Erect stem forks repeatedly.
     • ii. Sporangia located on some branches.
     • iii. Have vascular tissue in the stem but no true roots or leaves.
   • d. Similar to whisk brooms in appearance.
   • e. Modern species found in Arizona, Texas, Louisiana, Florida, Puerto Rico, and Hawaii.
7. Club Mosses Have Club-Shaped Strobili
   • a. In division Lycopodophyta with 1,000 species.
   • b. "Ground pines" are common in temperate woodlands; most club mosses in tropics and subtropics.
   • c. Branching rhizome sends up aerial stems less than 30 cm tall. (Fig. 29.7)
   • d. Sporangia form club on terminal clusters of leaves; called strobili.
   • e. Related Selaginella includes resurrection plant.
8. Horsetails Resemble Horses' Tails
   • a. In division Equisetophyta with 15 species all in genus Equisetum.
   • b. Rhizome produces aerial stem about 1.3 meters tall.
   • c. Whorls of side branches give appearance of green horse's tail.
   • d. Some form stroboli on regular stems; others form special stems for stroboli.
   • e. Silica in cell walls provide abrasive grit for use as scouring brushes to clean pots.
9. Ferns Are Leafy
   • a. In division Pteridophyta with 12,000 species.
   • b. Abundant in warm tropics but wide-ranging.
   • c. Species vary from mosslike to trees; highly diverse. (Fig. 29.9)
   • d. Curled-up young frond called "fiddlehead" unrolls as matures.
   • e. Life cycle of typical temperate fern: fern plant is dominant sporophyte generation; sporangia develop in sori on underside of fronds that are megaphylls secondarily subdivided into leaflets.
   • f. Uses of Ferns
     • i. Florists use them to decorate bouquets, fill in gardens.
     • ii. Used in tropics as termite-resistant building material.
     • iii. Used a medicines to stop bleeding, source of expectorant.
   • g. Adaptation of Ferns (p. 572)
     • i. Have true roots, stems, and leaves.
     • ii. Water-dependent gametophyte lacks vascular tissue.
     • iii. Flagellated sperm require outside water source to reach eggs in archegonia.
     • iv. Some spread to drier land by vegetative (asexual) reproduction.
     • v. Underground rhizomes grow horizontally; send up fiddleheads.

1. First of two major groups to disperse by seeds, an embryonic sporophyte with stored food in protective seed coat.
2. Disperses the generation best adapted to survival.
3. Seeds of gymnosperms are "naked," exposed on surface of scales within cones.
4. Four divisions (three considered here):
   • a. Cycads.
     • i. In division Cycadophyta with 100 species.
     • ii. Are cone-bearing, palmlike plants found in tropical and subtropical regions. (Fig. 29.11a)
     • iii. Mesozoic era is referred to as "Age of Cycads and Dinosaurs."
   • b. Ginkgo or maidenhair tree. (Fig. 29.11b)
     • i. In division Ginkgophyta with one known living species.
     • ii. Cultivated for ages in Asian ornamental and temple gardens.
     • iii. Survives in polluted areas but female trees are smelly.
   • c. Conifers are largest group of gymnosperms. (Fig. 29.11c)
     • i. Includes cone-bearing pine, cedar, spruce, fir, and redwood trees.
     • ii. Have needle-like leaves; well adapted to cold winters and high winds.
     • iii. Most are evergreen, keeping leaves throughout year.
5. Adaptations of Conifers
   • a. Success due to adaptations to land existence.
   • b. Well-developed roots and stems.
   • c. Tall trees that withstand temperature extremes and dryness.
   • d. External water for flagellated sperm is eliminated by having pollen grains transferred by wind and growth of pollen tube.
   • e. Cone protects megagametophyte and developing zygote.
   • f. Seed protects embryo, provides store of nutrients, and helps disperse species.
6. Importance of Conifers
   • a. Grow on large areas of earth's surface.
   • b. Provide most wood for building construction and production of paper.
   • c. Source of chemicals including resin extracts, etc.
   • d. Oldest trees may be bristlecone pines at over 4,500 years old; largest may be redwood trees in California at over 2,000 years and more than 90 m tall.
7. Conifer Life Cycle
   • a. Windblown pollen grains replace flagellated sperm.
   • b. Following fertilization, seed develops from ovule exposed on scale of seed cone.
   • c. Seeds are dispersed by wind.
8. Angiosperms are flowering plants in division Magnoliophyta with 235,000 species. (p. 578)
9. Angiosperms types include: hardwood trees including deciduous and broad-leaved evergreen trees, and herbaceous or nonwoody plants including grasses and garden plants.
10. Angiosperms provide food, clothing, medicines, and commercial products. (see Reading p. 576)
11. Angiosperms classification
    • i. Dicotyledons (or "dicots")
      - either woody or herbaceous.
      - flower parts in fours or fives.
      - leaves have veins in net pattern.
      - vascular bundles arranged in circle in stem.
      - two seed leaves, or cotyledons.
      - includes familiar buttercup, mustard, maple tree, cactus, pea, rose, etc.

      ii. Monocotyledons (or "monocots")

      - mostly herbaceous.

      - flower parts in threes.

      - leaves have parallel veins.

      - vascular bundles scattered in stem.

      - one seed leaf or cotyledon.

      - includes lily, palm, wheat, rice, corn (maize), and other agriculturally important grasses.
12. Unique Features of Angiosperms
    • a. Flowers attract animals for pollination.
    • b. Protect developing megagametophyte.
    • c. Produce seeds enclosed by fruit.
13. Flower Anatomy (Fig. 29.13)
    • a. Sepals are usually green, outermost structures that form whorl around petals.
    • b. Petals are usually colorful to attract insects for pollination.
    • c. Stamen
      • i. Composed of a filament and anther with two pollen sacs.
      • ii. In pollen sacs, microspores become pollen grains.
      • iii. Stamens usually grouped around pistil.
    • d. Pistil
      • i. Usually in center of flower.
      • ii. Stigma is enlarged sticky knob to collect pollen.
      • iii. Style is slender stalk.
      • iv. Ovary is enlarged base containing ovules where megaspore becomes egg-producing megagametophyte.
14. Life Cycle (p. 578)
    • a. Angiosperms produce heterospores that develop into pollen grain (microgametophyte) ad embryo sac (megagametophyte) while on sporophyte plant. (Fig. 29.13)
    • b. Unlike gymnosperms, flowers attract pollinators to carry pollen from flower to flower.
    • c. Flowers and pollinator have co-evolved; for example: blue, yellow, and ultraviolet colors are within range of bee sight and pattern may lead bee to nectar at flower base.
    • d. While bee collects nectar and pollen for food, pollen is also inadvertently carried to next flower.
    • e. Double fertilization occurs.
      • i. One sperm nucleus fertilizes egg nucleus to form a zygote which becomes embryo.
      • ii. Second sperm nucleus unites with two polar nuclei to form 3N endosperm, which becomes food for developing embryo and dicot seed leaves.
    • f. Megaspore becomes megagametophyte enclosed in ovule that become seed; unlike gymnosperms, seeds are covered by fruits derived from ovary and surrounding structures.
    • g. Fruits
      • i. Include: milkweed pods, peas and beans, tomatoes, oranges, watermelon, etc.
      • ii. Function to disperse seeds using wind, gravity, water, and animals to area suitable for germination.