Presentation on theme: "Flowering Plants (Angiosperms)"— Presentation transcript:
1 Flowering Plants (Angiosperms) Chapter 23Flowering Plants (Angiosperms)I. IntroductionA. General Characteristics of Flowering Plants1. Largest and most diverse division of plants2. More than 250,000 known species of flowering plants, called angiosperms3. Angiosperm defined• "seed in a vessel"4. Vessel is the carpel, a fertile, modified leaf (one of four flower parts)
2 B. Classification of Division Magnoliophyta 1. Two large classesa. Magnoliopsida (Dicots)b. Liliopsida (Monocots)2. Origin of Angiosperms (2 Views)a. Older view (German school)1) Angiosperms evolved from conifers2) Flowers similar in structure to strobili (cones) of conifersb. Contemporary view1) Angiosperms evolved independently from pteridosperms (seed ferns)2) Flower is a modified stem bearing modified leaves
3 II. Division Magnoliophyta—The Flowering Plants A. Characteristics1. Size• tiny duckweeds to large eucalyptus trees2. Mode of nutritiona. Majority of flowering plants photosynthesizeb. Some parasitic, e.g., dodders, mistletoesc. Some saprophytes, e.g., some orchids3. Reproductiona. Heterosporous• production of 2 different types of sexual spores, micro- and megasporesb. Female gametophyte wholly enclosed within sporophyte tissuec. Male gametophyte is germinated pollen grain
4 B. Development of Gametophytes 1. Megasporogenesisa. Ovule produces megaspore mother cellb. Megaspore mother cell produces megaspores (female spores) via meiosis2. Megagametogenesisa. Megaspore (divides mitotically three times forming 8 nuclei)b. Mature embryo sac contains 7 cells1) 3 antipodal cells2) 2 synergid cells3) 1 egg cell4) 1 central cell (binucleated)
5 3. Microsporogenesisa. Occurs in anther regions called pollen sacs (microsporangia)b. Microspore mother cells produce microspores (immature pollen grains) via meiosis4. Microgametogenesisa. Microspores differentiate into pollen grains1) Generative cell of microspore divides forming 2 sperm cells2) Occurs during pollen germinationb. Mature male gametophyte (germinating pollen grains) consists of 3 cells, 2 of which are nonflagellated sperm5. Pollen grainsa. Outer wall, exine, contains chemicals that interact with stigma of flowerb. Aperture(s) in wall involved in pollen tube formation
8 C. Pollination1. Defined• transfer of pollen grains from male (anther) to female (stigma) flower part2. Agents of pollinationa. Windb. Waterc. Insectsd. Birdse. Bats
9 D. Fertilization and Development of the Seed 1. Pollen tube formation2. Double fertilizationa. Sperm #1 and egg = zygote (2n) develops into embryob. Sperm #2 and polar nuclei (n + n) = endosperm nucleus (3n) forms endosperm tissue3. Integuments mature into the seed coat
11 E. Other Types of Megagametophyte Development 1. 30% of angiosperms exhibit variations in embryo sac formation2. Embryo sac may contain 4-16 nuclei3. Endosperm may be 5n, 9n or 15n4. Lily, endosperm is 5n
13 F. Apomixis and Parthenocarpy 1. Apomixis defined• embryo formation without fertilization taking place. A 2n cell in the ovule or surrounding the ovule can develop into an embryo which can develop into a whole plant. This resembles vegetative propagation.2. Parthenocarpy defined• fruits that develop from ovaries containing unfertilized eggs Examples are navel oranges, supermarket bananas, and varieties of figs and grapes.
14 G. Trends of Specialization and Classification in Flowering Plants 1. Features of a Primitive Flowering Planta. Simple leavesb. Flowers with numerous spirally arranged partsc. Flowers radially symmetrical and have both stamens and pistils2. Specializations and Modifications of Flowersa. Reduction in number of flower partsb. Fused flower parts (compound pistil)c. Monoecious where both male and female imperfect flowers occur on the same plant such as members of the pumpkin family (squashes and watermelons) and dioecious plants where male and female imperfect flowers occur on different plants such as willows.
18 III. Pollination Ecology A. Pollination Vectors1. Beesa. Nectar of flower their chief source of nourishmentb. Prefer blue and yellow flowersc. Honey guides• lines on flower petals that lead bees to the nectard. Ultraviolet patterns on flowers visible to bees2. Beetlesa. Flowers generally white or dull in colorb. Strong yeasty, spicy, or fruity odors
19 3. Fliesa. Flowers dull red or brownb. Foul odorsc. Flowers called "carrion flowers"4. Moths and Butterfliesa. White or yellow in colorb. Sweet fragrances5. Birdsa. Flowers bright red or yellow and large inflorescencesb. Produce copious quantities of nectar in long floral tubes6. Batsa. Generally tropical flowers that open at nightb. Large flowers or ball-like inflorescences
20 B. Orchid Flowers and Their Adaptations for Pollination 1. Pollen grains produced in little sacs called pollinia2. Pollinia either stick to the insect pollinator or are forcibly "slapped" on the insect by a trigger mechanism3. Petals modified to resemble female wasp or bee• male insects attempt to mate with flower and pick up pollinia in the process4. Other adaptations include underwater trapdoors and powerful narcotic fragrances
21 IV. Herbaria and Plant Preservation A. Herbarium definedlibrary of dried and pressed plants arranged in systematic collectionsB. Methods (or How to Preserve a Plant)1. Remove soil gently from roots2. Lay out plant on newspaper sheets3. Straighten out leaves and petals, if possible4. Note on newspaper where collected, date, and by whom5. Cover with another sheet of newspaper6. Place specimen between 2 sheets of blotter paper7. Place plants into a plant press and tighten straps8. Allow plants to dry for several days9. Remove plants from press, mount on heavy white paper (herbarium paper)10. Glue plants to paper11. Place label with collection information in bottom right-hand corner12. Specimens are then placed in large manila folders and stored in some systematic fashion