Plant Biology: Flowers and Reproduction
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Questions and Answers

What does the carpel primarily consist of?

  • Stigma, anther, and ovule
  • Filament, stigma, and ovary
  • Style, ovary, and petal
  • Ovary, style, and stigma (correct)

    • What are flowers that contain only male or only female parts called?

  • Monoecious flowers
  • Perfect flowers
  • Dioecious flowers
  • Imperfect flowers (correct)

    • What is the process of transferring pollen from the anther to the stigma called?

  • Fertilization
  • Pollination (correct)
  • Self-fertilization
  • Germination

    • Which cell undergoes meiosis to form four haploid microspores?

    <p>Microspore mother cell</p> Signup and view all the answers

    What do animals receive in exchange for helping with pollination?

    <p>Nectar</p> Signup and view all the answers

    What is the end result of the generative cell division in pollen grains?

    <p>Two sperm cells are formed</p> Signup and view all the answers

    What occurs during self-pollination?

    <p>Pollen from the anther pollinates the stigma of the same flower</p> Signup and view all the answers

    What is the main advantage of asexual reproduction in stable environments?

    <p>It allows individuals to reproduce with lower energy investment.</p> Signup and view all the answers

    How many haploid megaspores are produced from one diploid megaspore mother cell?

    <p>Four</p> Signup and view all the answers

    Which of the following is NOT a form of vegetative reproduction?

    <p>Pollination</p> Signup and view all the answers

    In the alternation of generations in plants, which generation is diploid?

    <p>Sporophyte generation</p> Signup and view all the answers

    What develops from microspores in angiosperms?

    <p>Pollen grains</p> Signup and view all the answers

    Which part of the angiosperm flower is responsible for the production of male gametes?

    <p>Anther</p> Signup and view all the answers

    What type of plant structure is formed by underground horizontal stems?

    <p>Rhizomes</p> Signup and view all the answers

    Which of the following describes the female part of the flowering plant?

    <p>Carpel</p> Signup and view all the answers

    Which statement accurately distinguishes vegetative reproduction from sexual reproduction in angiosperms?

    <p>Vegetative reproduction involves cloning from parent plants.</p> Signup and view all the answers

    What is essential for seed germination to occur?

    <p>Favorable environmental conditions</p> Signup and view all the answers

    How are fleshy fruits primarily dispersed?

    <p>By birds and other vertebrates</p> Signup and view all the answers

    What is the first action a seed takes during germination?

    <p>Water absorption occurs</p> Signup and view all the answers

    Which of the following statements is true regarding plant hormones?

    <p>They regulate gene expression in plants.</p> Signup and view all the answers

    What emerges first from a germinating seed?

    <p>Coleoptile in monocots</p> Signup and view all the answers

    Which type of fruit is spread primarily through wind?

    <p>Dry fruit</p> Signup and view all the answers

    What aspect of plant growth and differentiation is influenced by environmental signals?

    <p>Meristematic tissue activity</p> Signup and view all the answers

    How can differentiated plant tissues respond to environmental cues?

    <p>They can express hidden genetic information.</p> Signup and view all the answers

    What is the term used for the ability of plants to stop growing when conditions are not favorable?

    <p>Dormancy</p> Signup and view all the answers

    Which type of tropism is responsible for the upward growth of stems?

    <p>Gravitropism</p> Signup and view all the answers

    In the study by Irwin and Strauss, what factor influenced the creation of the first population of wild radish flowers?

    <p>Color preferences of pollinators</p> Signup and view all the answers

    Which type of response is thigmotropism in plants?

    <p>Response to touch</p> Signup and view all the answers

    What usually triggers dormancy in temperate zone plants?

    <p>Low temperatures and freezing water</p> Signup and view all the answers

    What is essential for effective animal pollination?

    <p>A specific insect or animal must visit the same species of plants.</p> Signup and view all the answers

    What characterizes wind-pollinated angiosperms?

    <p>The flowers are small, green, and odorless.</p> Signup and view all the answers

    What occurs after pollen grains adhere to the stigma?

    <p>They form a pollen tube that grows through the style.</p> Signup and view all the answers

    What is the outcome of double fertilization?

    <p>One sperm fertilizes the egg and another forms endosperm.</p> Signup and view all the answers

    What typically happens to an embryo after fertilization?

    <p>The embryo enters a dormant state due to drying.</p> Signup and view all the answers

    What purpose does the seed coat serve?

    <p>It protects the dormant embryo and provides a food source.</p> Signup and view all the answers

    What is required for germination to occur?

    <p>Water and oxygen must reach the dormant embryo.</p> Signup and view all the answers

    During early embryo development, what structure has formed by the time dormancy is reached?

    <p>The cotyledons and apical meristems.</p> Signup and view all the answers

    Which of the following hormones is primarily responsible for phototropism in plants?

    <p>Auxin</p> Signup and view all the answers

    What is the primary effect of synthetic auxins like 2,4-D on plants?

    <p>Causing the plant to grow to death</p> Signup and view all the answers

    Which of the following is NOT one of the major kinds of hormones found in plants?

    <p>Glutamate</p> Signup and view all the answers

    What defines long-day plants in relation to flowering?

    <p>They flower when days become longer.</p> Signup and view all the answers

    Which type of plant requires shorter days for flowering to occur?

    <p>Short-day plants</p> Signup and view all the answers

    What aspect of plant growth does auxin predominantly influence?

    <p>Cell elongation on one side of the plant</p> Signup and view all the answers

    Which hormone is associated with inhibiting growth and promoting dormancy in plants?

    <p>Abscisic acid</p> Signup and view all the answers

    What did F.C. Steward successfully demonstrate regarding plant tissue?

    <p>Phloem tissue can regenerate entire plants.</p> Signup and view all the answers

    Study Notes

    Plant Reproduction and Growth

    • Angiosperms (flowering plants) can reproduce asexually or sexually.
    • Asexual reproduction is advantageous in stable environments and creates clones of the parent plant.
    • Vegetative reproduction is a type of asexual reproduction where new plants grow from parts of the parent.
    • Runners, rhizomes, suckers, and adventitious plantlets are forms of vegetative reproduction.
    • Runners are slender stems growing along the soil surface (strawberries).
    • Rhizomes are underground horizontal stems forming networks (irises, potatoes).
    • Suckers or sprouts arise from roots (cherries, apples).
    • Adventitious plantlets form from meristematic tissue in the leaf notches (Kalanchoë).

    Sexual Reproduction in Angiosperms

    • Sexual reproduction alternates between diploid sporophyte and haploid gametophyte generations.
    • The diploid sporophyte gives rise to a haploid gametophyte enclosed within sporophyte tissues.
    • Male gametophytes are pollen grains developing from microspores.
    • Female gametophytes are embryo sacs growing from megaspores.
    • Gametophytes are produced in specialized structures of the flower.

    Flower Structure

    • Most flowers have male and female parts.
    • Male parts are called stamens, with anthers at their tips.
    • Female parts are called carpels, consisting of an ovary, style, and stigma.
    • Imperfect flowers have only male or female parts.
    • Monoecious plants have imperfect male and female flowers on the same plant.

    Pollen Formation

    • Pollen sacs inside anthers contain microspore mother cells.
    • Meiosis turns microspore mother cells into four haploid microspores.
    • Mitosis transforms microspores into pollen grains containing a generative cell and a tube cell nucleus.
    • The tube cell nucleus produces the pollen tube.
    • The generative cell divides to produce two sperm cells.

    Egg Formation

    • Ovules within the ovary contain diploid megaspore mother cells.
    • Meiosis produces four haploid megaspores from megaspore mother cells.
    • A single megaspore undergoes repeated mitotic divisions for eight haploid nuclei.
    • These nuclei are precisely arranged within an embryo sac.

    Pollination

    • Pollination is the transfer of pollen from anther to stigma.
    • Self-pollination occurs when pollen from a flower pollinates the same flower.
    • Many angiosperms rely on animals (pollinators) for pollen transfer.
    • Pollinators are often rewarded with food (nectar).

    Wind Pollination

    • Pollen is passively dispersed by wind in some angiosperms.
    • Plants that rely on wind pollination tend to have small, green, odorless flowers.
    • Plants need to be close together for wind pollination to occur.

    Fertilization

    • Pollen grains stick to the stigma and sprout pollen tubes.
    • Pollen tubes extend through the style to ovules.
    • Two sperm cells are released in the embryo sac.
    • One sperm fertilizes the egg while the other fuses with polar nuclei to create endosperm.
    • This process of using two sperm cells is called double fertilization.

    Seed Formation

    • Embryo development occurs after fertilization via active cell division.
    • Embryos become dormant due to drying, often after apical meristems and cotyledons (seed leaves) have formed.

    Seeds

    • Outer ovule layer develops into seed coat.
    • Seed coat is impermeable and protects dormant embryo from the surroundings.
    • Seeds also contain food for early growth.
    • Germination is the resumption of metabolic activities.
    • Germination happens when water and oxygen reach the embryo.
    • Germination occurs under favorable conditions.

    Fruits

    • The flower ovary develops into a fruit during seed development.
    • Fruits come in different forms and ways.
    • Fleshy fruits are often dispersed by birds and other vertebrates.
    • Some fruits have mechanisms for dispersal via wind, attachment to mammals/birds, or water.

    Germination

    • Water absorption is the first step in germination.
    • Seed coat rupture starts aerobic respiration.
    • Roots emerge first, followed by stems and cotyledons in eudicots.
    • Monocots have coleoptiles emerging first.

    Plant Hormones

    • Plant development hinges on meristematic tissue activities interacting with the environment through hormones.
    • Differentiation is largely reversible in plants.
    • Certain differentiated plant cells can regain their potential to develop.
    • Plant hormones control gene expression.
    • Plant hormones originate in non-specialized tissues performing various roles.

    Phototropism

    • Phototropism involves plant growth towards light.
    • Early experiments on phototropism involved the Darwins.
    • Auxin is a plant hormone that controls phototropic responses.
    • Auxin's effects differ on opposite sides of plant in response to light.

    Synthetic Auxins

    • Synthetic auxins are used to kill weeds.
    • Synthetic auxins promote growth to the point of death, reducing ATP production.
    • 2,4-D is an example of a synthetic auxin that targets broadleaf eudicots.

    Photoperiodism

    • Photoperiodism is a mechanism for organisms to detect seasonal changes in light and dark.
    • Plant flowering responses differ based on day length.
    • Long-day plants flower in longer days.
    • Short-day plants flower in shorter days.
    • Day-neutral plants flower regardless of day length.

    Dormancy

    • Plants can stop growing when conditions are unfavorable.
    • This temporary state is called dormancy.
    • Dormancy is common in winter in temperate zones due to freezing temperatures and reduced water availability.

    Tropisms

    • Tropisms are directional and irreversible growth responses to external stimuli.
    • Phototropism is plant growth towards light.
    • Gravitropism causes stem upward and root downward growth.
    • Thigmotropism is the response of plants to touch.

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