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 (A)</p> Signup and view all the answers

What do animals receive in exchange for helping with pollination?

<p>Nectar (B)</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 (D)</p> Signup and view all the answers

What occurs during self-pollination?

<p>Pollen from the anther pollinates the stigma of the same flower (D)</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. (C)</p> Signup and view all the answers

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

<p>Four (B)</p> Signup and view all the answers

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

<p>Pollination (B)</p> Signup and view all the answers

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

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

What develops from microspores in angiosperms?

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

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

<p>Anther (D)</p> Signup and view all the answers

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

<p>Rhizomes (C)</p> Signup and view all the answers

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

<p>Carpel (D)</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. (D)</p> Signup and view all the answers

What is essential for seed germination to occur?

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

How are fleshy fruits primarily dispersed?

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

What is the first action a seed takes during germination?

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

Which of the following statements is true regarding plant hormones?

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

What emerges first from a germinating seed?

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

Which type of fruit is spread primarily through wind?

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

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

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

How can differentiated plant tissues respond to environmental cues?

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

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

<p>Gravitropism (C)</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 (C)</p> Signup and view all the answers

Which type of response is thigmotropism in plants?

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

What usually triggers dormancy in temperate zone plants?

<p>Low temperatures and freezing water (C)</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. (D)</p> Signup and view all the answers

What characterizes wind-pollinated angiosperms?

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

What is the outcome of double fertilization?

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

What is required for germination to occur?

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

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

<p>Auxin (A)</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 (D)</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 (C)</p> Signup and view all the answers

What defines long-day plants in relation to flowering?

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

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

<p>Short-day plants (A)</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 (B)</p> Signup and view all the answers

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

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

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

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

Flashcards

Vegetative Reproduction

The process by which new individuals are created from parts of the parent plant, such as stems, roots, or leaves. It occurs without the involvement of seeds.

Runners

Slender stems that grow along the soil surface, creating new plants at their tips (e.g., strawberry plants).

Rhizomes

Underground horizontal stems that create a network, giving rise to new shoots (e.g., irises, potatoes).

Suckers

Sprouts produced by roots, giving rise to new plants (e.g., cherry, apple, raspberry plants).

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Adventitious Plantlets

Plantlets that arise from meristematic tissue on leaves, developing into new plants (e.g., Kalanchoë daigremontiana).

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Sexual Reproduction (in Plants)

The production of new individuals through the fusion of gametes (sex cells).

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Sporophyte Generation

The generation of a plant that produces spores (haploid cells responsible for producing gametes).

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Gametophyte Generation

The generation of a plant that produces gametes (sex cells).

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Ovary

The lower, rounded portion of the carpel containing ovules where the megaspores will be formed.

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Style

A long, slender stalk connecting the ovary to the stigma.

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Stigma

The sticky, receptive tip of the carpel, where pollen grains land and germinate.

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Imperfect Flower

Flowers that contain only male or only female reproductive parts.

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Monoecious

Plants that contain both male and female flowers on the same plant.

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Pollination

The process by which pollen grains are transferred from the anther to the stigma.

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Self-Pollination

When pollen from the same flower's anther pollinates its own stigma.

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Microspore Mother Cells

The specialized cells within the anther that produce pollen grains through meiosis and mitosis.

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Animal pollination

Pollination by animals, especially insects.

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Pollen tube growth

The process of the pollen tube growing from the stigma down to the ovary.

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Double fertilization

The process of two sperm cells fusing with the egg and the polar nuclei forming the embryo and endosperm.

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Seed embryo

The dormant embryo inside the seed.

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Seed germination

The resumption of metabolic activities in a dormant seed, leading to growth.

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Dormancy (in Plants)

A state of suspended growth or activity, typically occurring in plants during unfavorable conditions like winter.

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Tropisms

Directional and irreversible growth responses of plants to external stimuli.

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Phototropism

The growth of plants towards light, a vital tropism ensuring access to photosynthesis.

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Gravitropism

The growth of plants in response to gravity, causing stems to grow upward and roots downward.

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Thigmotropism

The response of plants to touch, causing them to grow around or cling to objects.

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What is seed germination?

When the seed experiences suitable circumstances, a process which begins with water absorption, breaks the seed coat, starts aerobic respiration, and results in root emergence. In eudicots, cotyledons rise from underground, along with the stem. In monocots, the coleoptile emerges from the ground.

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How does a plant develop after germination?

The interaction between the plant's meristematic tissues and environmental signals, controlled by hormones that affect growth and differentiation.

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Explain fruit formation and dispersal

Fruits differ in form and are dispersed by various methods, including animals, wind, water, or adhering to mammals or birds. Fleshy fruits are often dispersed by birds and animals.

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How are fruits formed?

The flower ovary, after seed formation, develops into a fruit. Fruits have diverse shapes and forms.

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What is reversibility of differentiation in plants?

The potential for plant cells to reverse differentiation, allowing them to express dormant genetic information when triggered by environmental signals, like hormones.

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What is the role of plant hormones in plant growth?

Plant hormones regulate the expression of particular plant genes, playing a crucial role in controlling plant growth and development.

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Auxin

A plant hormone that primarily controls cell elongation and differentiation, regulating growth patterns.

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Darwin's Phototropism Experiment

The Darwins observed that a substance controlled plant bending towards light. Later identified as auxin.

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How Auxin Controls Phototropism

Auxin causes cell elongation on the shaded side of a plant, resulting in bending towards the light source.

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Synthetic Auxin as Herbicides

Synthetic auxins are herbicides that kill plants by causing excessive growth, depleting their energy reserves.

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Photoperiodism

The response of organisms to seasonal changes in day and night length, particularly affecting flowering in plants.

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Long-Day Plants

Plants that flower when days become longer, typically in the summer.

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Short-Day Plants

Plants that flower when days become shorter, typically in the fall.

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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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