Plant Reproduction Chapter 42 Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Rise of the Flowering Plants Virtually all our food is derived, directly or indirectly, from flowering plants. Also sources of medicine, clothing, and building materials. Much of early angiosperm evolution may have taken place in patches of drier or unfavorable habitat in the interior of Gondwanaland. Outcrossing may have been important in early success. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Evolution of the Flower Pollen matures within the anthers and is transported to the stigma of another flower. When pollen reaches the stigma, it germinates, and a pollen tube grows down, carrying sperm nuclei to the embryo sac. Seed matures within ripening fruit. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Evolution of the Flower Characteristics A complete flower has four whorls, while an incomplete flower lacks at least one. Calyx, composed of sepals, makes up outermost whorl. Petals collectively make up the corolla. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Evolution of the Flower Characteristics Male part: Stamens collectively compose androecium. Stamens made up of filament and anther. Female part: Gynoecium refers to the collection of female parts in a flower. Single or fused carpels also referred to as simple or compound pistils. Ovules produced in pistil’s swollen ovary. Style - Slender neck. Stigma - Pollen-receptive structure. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Evolution of the Flower Trends in Floral Specialization Separate floral parts have fused. Floral Parts have been lost or reduced. Resultant of natural selection and artificial breeding. Trends in Floral Symmetry Many flowers of advanced groups are bilaterally symmetrical. Often associated with advanced pollination systems. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Formation of Angiosperm Gametes Plant sexual life cycles are characterized by an alternation of generations. Diploid sporophyte gives rise to haploid gametophyte generation. Male gametophytes (microgametophytes) - Pollen grains Female gametophyte (megagametophyte) - Embryo sac Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Formation of Angiosperm Gametes Angiosperms have separate structures for reproduction . Similar to animals, except: Male and female structures usually occur together in the same individual flower. Angiosperm reproductive structures are not permanent parts of the adult individual. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Formation of Angiosperm Gametes Pollen Formation Each pollen sac contains specialized chambers enclosing microspore mother cells. Undergo meiosis to form four haploid microspores. Pollen grain shapes are specialized for specific flower species. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Formation of Angiosperm Gametes Embryo Sac Megaspore mother cell found within each ovule. Undergoes meiosis to produce four haploid megaspores. Usually only one survives and the other three are absorbed by the ovule. Remaining megaspore undergoes mitosis and produces eight haploid nuclei enclosed in an embryo sac. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Pollination - Pollen is placed on the stigma. Early seed plants pollinated passively. Pollination by Animals Bees - Initially locate food sources by odor, and then orient on a flower by its shape, color, and texture. May drive coevolution. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Pollination Other Insects Butterflies Moths Beetles Birds Many plants produce large amount of nectar to attract birds. Hummingbirds Red colors tend to attract birds, while carotenoids tend to attract insects because they are visible in the UV range. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Wind-Pollinated Angiosperms Pollination Other Animals Bats Rodents Monkeys Wind-Pollinated Angiosperms Typically have small, greenish, odorless flowers with reduced or absent corollas. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Two basic reasons for self-pollination. Ecologically advantageous as they do not need to be visited by animals, and thus do not have to expend energy producing attractants. Produces more uniform progeny than outcrossing. Well-adapted to particular habitats. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Factors Promoting Outcrossing Self-Pollination Factors Promoting Outcrossing Dioecious plants produce only ovules or only pollen on a single individual. Monoecious produce both on same plant. Dichogamous - Functional stamens and pistils present on same plant, but reach maturity at different times. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Self-Pollination Self-incompatibility results when pollen and stigma recognize each other as genetically related and pollen tube growth is blocked. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Fertilization Double Fertilization results in two key developments: Fertilization of the egg. Formation of endosperm. Pollen grains adhere to the stigma and grow a pollen tube that pierces the style. Grows until it reaches the ovule in the ovary. Tip of pollen tube bursts and releases two sperm cells. One fertilizes the egg cell forming a zygote. The other cell fuses with two polar nuclei located at the center of the embryo sac. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Vegetative Reproduction - New plants are cloned from adult parts. Asexual Reproduction Vegetative Reproduction - New plants are cloned from adult parts. Runners Rhizomes Suckers Adventitious Plantlets Apomixis - Embryos in seeds produced asexually from the parent plant. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Once established, plants live for highly variable periods of time. Life Span of Plants Once established, plants live for highly variable periods of time. Life span may or may not correlate with reproductive strategy. Woody plants which have extensive secondary growth, nearly always live longer than herbaceous plants, which have limited to no secondary growth. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Grow rapidly under favorable conditions. Life Span of Plants Annuals Annual plants grow, flower, and form fruits and seeds within one growing season, and then die when the process is complete. Grow rapidly under favorable conditions. Developing flowers or embryos use hormones signaling nutrient reallocation. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Biennial plants have life cycles that take two years to complete. Life Span of Plants Biennials Biennial plants have life cycles that take two years to complete. Photosynthate stored in underground storage organs during the first year. Flowering stems are produced during the second year. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Perennial plants grow year after year. Life Span of Plants Perennials Perennial plants grow year after year. Majority of vascular plants are perennial. Food is often stored in roots or underground stems which can become relatively large. Trees and shrubs generally flower repeatedly. Deciduous or Evergreen. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Life Span of Plants Organ Abscission Abscission - Shedding of leaves or petals. Dispense with nutrient sinks. Shaded leaves, petals Evergreens usually have complete change of leaves every two to seven years. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Life Span of Plants Abscission involves changes in abscission zone at the base of the petiole. Young leaves produce hormones that inhibit development of specialized layers of cells in the abscission zone. Cells become impregnated with suberin. Separation layer develops on the side of the leaf blade; cells of the separation layer divide, swell, and become gelatinous. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies