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Questions and Answers
What is the main purpose of the seed coat in a developing seed?
What is the main purpose of the seed coat in a developing seed?
Which part of a seed embryo develops into the embryonic root?
Which part of a seed embryo develops into the embryonic root?
From what part of the flower does an aggregate fruit form?
From what part of the flower does an aggregate fruit form?
Which type of fruit has a fleshy pericarp and is classified as a simple fruit?
Which type of fruit has a fleshy pericarp and is classified as a simple fruit?
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What is the main characteristic of apomixis as a mechanism of natural reproduction in plants?
What is the main characteristic of apomixis as a mechanism of natural reproduction in plants?
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Which type of plant completes its life cycle in one year?
Which type of plant completes its life cycle in one year?
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What sets polycarpic plants apart from monocarpic plants?
What sets polycarpic plants apart from monocarpic plants?
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What is the main function of the endosperm in a developing seed?
What is the main function of the endosperm in a developing seed?
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Which part of a seed embryo develops into the stem below the cotyledons?
Which part of a seed embryo develops into the stem below the cotyledons?
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From what part of the ovary do multiple fruits develop?
From what part of the ovary do multiple fruits develop?
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What is a characteristic feature of apomixis as a method of reproduction in plants?
What is a characteristic feature of apomixis as a method of reproduction in plants?
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What is a common feature between drupes and pomes as types of fruits?
What is a common feature between drupes and pomes as types of fruits?
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Which plant species exemplifies a monocarpic life cycle?
Which plant species exemplifies a monocarpic life cycle?
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Study Notes
Plant Reproduction
- Monocarpic plants flower once in their lifetime before dying, while polycarpic plants can flower multiple times throughout their life.
- Flower structures consist of four whorls:
- Calyx: Outermost, made of sepals, protecting the bud.
- Corolla: Second whorl of petals; petal count differs between monocots (3 or multiples) and dicots (4, 5, or multiples).
- Androecium: Contains male reproductive structures (stamens).
- Gynoecium: Innermost, holds female reproductive structures (carpels).
Reproductive Structures
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Carpel (female part):
- Ovary: Houses ovules, develops into fruit post-fertilization.
- Stigma: Receives pollen.
- Style: Connects stigma and ovary.
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Stamen (male part):
- Anther: Contains pollen grains.
- Filament: Supports the anther.
Types of Flowers
- Complete Flowers: Contain all four whorls.
- Perfect Flowers: Possess both male and female structures.
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Imperfect Flowers:
- Staminate: Only male parts.
- Carpellate: Only female parts.
- Monoecious Plants: Both male and female flowers on the same plant.
- Dioecious Plants: Male and female flowers on separate plants.
Gamete Production
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Male Gamete Production:
- In anthers, microsporocyte undergoes meiosis to form pollen tetrads.
- Microspores undergo mitosis, leading to a generative cell (produces two sperm) and a vegetative/tube cell (develops into a pollen tube).
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Female Gamete Production:
- In ovules, megasporocyte undergoes meiosis to yield four megaspores (three degenerate, one survives).
- The surviving megaspore divides, forming an 8-nucleate, 7-celled gametophyte (embryo sac) with synergids, egg, antipodal cells, and a central cell that leads to the endosperm.
Fertilization
- Involves the mechanical transfer of pollen from anther to stigma.
- Pollen grain forms a tube guided toward the embryo sac and enters through the micropyle.
- One pollen cell lags to produce two sperm cells; sperm lack flagella.
Pollination
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Cross-Pollination Mechanisms:
- Self-Pollination: No need for nectar production.
- Insect Pollination: Flower shapes suited to specific pollinators.
- Bat Pollination: Large, bright flowers visible at night.
- Bird Pollination: Sturdier plants with bright, odorless flowers.
- Wind Pollination: Flowers emerge before leaves, with pollen released.
- Water Pollination: Aquatic flowers utilizing water currents.
Seed Development
- Fertilization leads to the formation of a zygote, which divides into an embryo.
- Ovule develops into a seed; the seed coat forms for protection.
- Endosperm serves as a food reserve for the developing embryo.
- Seeds have various structures:
- Cotyledons: Leaves.
- Radicle: Roots.
- Hypocotyl: Stem segment below cotyledons.
- Epicotyl: Stem segment above cotyledons.
- Micropyle: Pore for gas exchange; Hilum: Scar from attachment to the ovary wall.
Seed Types
- Monocots: One cotyledon.
- Dicots: Two cotyledons.
Fruit Formation
- True Fruits: Develop from ovary walls post-fertilization.
- Accessory Fruits: Arise from non-ovary parts of the flower.
- Types include:
- Simple Fruits: From a single ovary.
- Aggregate Fruits: From clustered carpels.
- Multiple Fruits: From inflorescences.
- Examples of fruit types:
- Berries: Fleshy fruits with many seeds (e.g., blueberries, tomatoes).
- Drupes: Hard endocarp surrounding the seed (e.g., mangos).
- Pomes: Accessory fruits (e.g., apples).
- Achenes: Solid dry fruits that do not split (e.g., strawberries).### Fruit Overview
- Thickened walls of the ovary protect seeds, primarily serving for seed dispersal.
- True fruits develop from the ovary, while accessory or false fruits originate from other plant parts.
Fruit Structure
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Pericarp: Composed of three layers:
- Exocarp: Outer skin or covering.
- Mesocarp: Middle, often fleshy layer.
- Endocarp: Inner layer surrounding the seed.
Types of Fruit
- Simple Fruits: Derived from a single ovary.
- Aggregate Fruits: Form from multiple carpels that fuse together.
- Multiple Fruits: Develop from clusters of flowers (inflorescence).
- Accessory Fruits: Formed from parts other than the ovary.
Specific Fruit Types
- Berries: Simple fruits with fleshy innermost tissues and many seeds (e.g., blueberries, tomatoes).
- Drupes: Simple fruits featuring a hard endocarp (pit) surrounding the seed (e.g., mangos, olives).
- Pepos: Modified berries with a hard rind (e.g., cucumbers, watermelons).
- Hesperidium: Special berries with leathery rind and segmented interior (e.g., citrus fruits).
- Pomes: Accessory fruits from united carpels (e.g., apples, pears).
- Achenes: Dry fruits that do not split open, exemplified by strawberries, which themselves are accessory fruits with fleshy receptacles.
Reproduction in Angiosperms vs. Gymnosperms
- Angiosperms: Gametophytes are in flowers, double fertilization occurs, and ovary tissues form fruit. Animal pollination predominates.
- Gymnosperms: Gametophytes on separate cones, single fertilization leads to a naked seed, with wind pollination being most common.
Asexual Reproduction Mechanisms
- Apomixis: Asexual seed production without fertilization, originating from diploid ovule or ovary.
- Self-Propagation: Includes structures like stolons (e.g., strawberries), tubers (e.g., potatoes), and rhizomes (e.g., ginger).
Plant Life Spans
- Senescence: Aging process varying widely, from weeks to thousands of years.
- Types include:
- Annuals: Complete life cycle in one year.
- Biennials: Life cycle spans two years.
- Perennials: Live for multiple years.
- Monocarpic: Flower once and die soon after.
- Polycarpic: Flower multiple times throughout life.
Flower Structure
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Four Whorls:
- Calyx: Outermost whorl of sepals for bud protection.
- Corolla: Second whorl of petals, varying by monocots/dicots.
- Androecium: Third whorl containing male parts (stamens).
- Gynoecium: Innermost whorl with female parts (carpels).
Reproductive Structures
-
Carpel (Female):
- Ovary: Houses ovule, becomes fruit.
- Stigma: Pollen landing site.
- Style: Stalk connecting to ovary.
-
Stamen (Male):
- Anther: Contains pollen grains.
- Filament: Supports the anther.
Flower Types
- Complete Flower: Contains all four whorls.
- Perfect Flower: Both male and female structures present.
- Imperfect Flowers: Staminate (male only) or carpellate (female only).
Gamete Production in Angiosperms
- Male Gametes: Microsporogenesis leads to tetrads of microspores, where one turns into a pollen grain with sperm cells.
- Female Gametes: Megasporogenesis produces megaspores; the surviving one forms an 8-nucleate embryo sac with various cell types.
Fertilization and Pollination
- Fertilization requires pollen transfer to stigma, followed by pollen tube growth to the embryo sac.
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Cross-Pollination: Involves mechanisms like:
- Self-Pollination: Requires no nectar for pollinators.
- Insect Pollination: Flowers adapted to pollinators’ shapes.
- Animal Pollination: Such as bats and birds, with flowers designed for visibility and separation.
- Wind Pollination: Timing of flower release before leaf emergence to facilitate pollen dispersal.
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Description
Test your knowledge on the different types of fruits and their structures. Learn about simple fruits, aggregate fruits, and multiple fruits. Understand the components of a fruit including pericarp, exocarp, mesocarp, and endocarp.
