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Questions and Answers
What is the first part of the seed that emerges during germination?
What is the first part of the seed that emerges during germination?
In hypogeal germination, which part of the seed grows first?
In hypogeal germination, which part of the seed grows first?
What is the role of endosperm in monocot seeds?
What is the role of endosperm in monocot seeds?
What happens to the cotyledons during hypogeal germination?
What happens to the cotyledons during hypogeal germination?
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Which of the following statements about dicot seeds is true?
Which of the following statements about dicot seeds is true?
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What type of respiration do seeds switch to once oxygen becomes available?
What type of respiration do seeds switch to once oxygen becomes available?
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Which of the following seeds typically exhibit hypogeal germination?
Which of the following seeds typically exhibit hypogeal germination?
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What is the initial step in the seed germination process?
What is the initial step in the seed germination process?
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Which environmental factor is NOT required for seed germination?
Which environmental factor is NOT required for seed germination?
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During epigeal germination, which part of the seed pushes the cotyledons out of the soil?
During epigeal germination, which part of the seed pushes the cotyledons out of the soil?
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What facilitates the absorption of water and nutrients for the young plant after germination?
What facilitates the absorption of water and nutrients for the young plant after germination?
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During the process of imbibition, what happens to the seed?
During the process of imbibition, what happens to the seed?
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What is produced during seed metabolism, aiding growth and cellular activities?
What is produced during seed metabolism, aiding growth and cellular activities?
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What is the primary purpose of seed dormancy?
What is the primary purpose of seed dormancy?
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In which stage of seed germination does respiration initiate?
In which stage of seed germination does respiration initiate?
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Which component protects the radicle in monocot seeds?
Which component protects the radicle in monocot seeds?
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Which type of seeds have persistent endosperm during embryo development?
Which type of seeds have persistent endosperm during embryo development?
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What characterizes a monocotyledon seed?
What characterizes a monocotyledon seed?
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Which part of the dicotyledon seed serves as the attachment site to the ovary wall?
Which part of the dicotyledon seed serves as the attachment site to the ovary wall?
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What is the function of the aleurone layer in monocot seeds?
What is the function of the aleurone layer in monocot seeds?
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What is true about non-endospermic seeds?
What is true about non-endospermic seeds?
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Which component of the seed is responsible for water absorption?
Which component of the seed is responsible for water absorption?
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What describes the structure of dicot seeds?
What describes the structure of dicot seeds?
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Which of the following is a characteristic of the radicle in a seed?
Which of the following is a characteristic of the radicle in a seed?
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Which layer of fruit is considered the outermost?
Which layer of fruit is considered the outermost?
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What is a defining characteristic of simple fruits?
What is a defining characteristic of simple fruits?
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Which fruit type develops from several ovaries in multiple flowers?
Which fruit type develops from several ovaries in multiple flowers?
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An example of an aggregate fruit is:
An example of an aggregate fruit is:
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In which type of fruit is the edible part primarily tissue other than ovary tissue?
In which type of fruit is the edible part primarily tissue other than ovary tissue?
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What role do cotyledons play in the early life of a plant?
What role do cotyledons play in the early life of a plant?
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Seed dormancy is best described as which of the following?
Seed dormancy is best described as which of the following?
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Which of the following is NOT a cause of seed dormancy?
Which of the following is NOT a cause of seed dormancy?
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Which of the following is a benefit of seed dormancy for plants?
Which of the following is a benefit of seed dormancy for plants?
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How does seed dormancy help in environmental conditions?
How does seed dormancy help in environmental conditions?
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What is one way that seed dormancy acts as a survival mechanism?
What is one way that seed dormancy acts as a survival mechanism?
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What triggers the process allowing a dormant seed to germinate?
What triggers the process allowing a dormant seed to germinate?
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What kind of plants typically show epigeal germination?
What kind of plants typically show epigeal germination?
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What is the role of scarification in seed dormancy?
What is the role of scarification in seed dormancy?
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Which method of overcoming seed coat dormancy involves soaking seeds in acid?
Which method of overcoming seed coat dormancy involves soaking seeds in acid?
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What is required for successful refrigerated stratification of seeds?
What is required for successful refrigerated stratification of seeds?
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What defines a parthenocarpic fruit?
What defines a parthenocarpic fruit?
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What happens to the ovary wall during the process of fruit development?
What happens to the ovary wall during the process of fruit development?
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Which of the following is NOT a method for overcoming seed dormancy?
Which of the following is NOT a method for overcoming seed dormancy?
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What is the primary function of a fruit in relation to seeds?
What is the primary function of a fruit in relation to seeds?
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What is a common characteristic of giberellins acid (GAs) related to seed dormancy?
What is a common characteristic of giberellins acid (GAs) related to seed dormancy?
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Study Notes
Seed and Fruit Development
- This chapter covers the structure, germination, dormancy, and development of seeds and fruits.
Learning Objectives
- Students will be able to recognize seed structure.
- Students will be able to explain seed germination.
- Students will be able to explain seed dormancy.
- Students will be able to describe fruit development.
Seed Structure
- Flowering plants produce seeds in various shapes, sizes, and colors.
- A seed is a small embryonic plant enclosed in a seed coat, usually with stored food.
- Seeds develop from fertilized ovules.
- Generally, a seed has three parts:
- Seed coat: The outermost covering of a seed, developing from the integuments of the ovule. It usually has a hard, leathery outer layer (testa) and a thin, papery inner layer (tegmen). The seed coat protects the seed from environmental factors like sunlight, water, and parasites. Its hardness prevents germination under unsuitable conditions.
- Endosperm: A triploid nutritive tissue providing stored food for the developing embryo. It forms from the fusion of a haploid male gamete with a diploid central cell within the embryo sac.
- Embryo: Consists of an embryonal axis with a radicle (the lower end, developing into the root system) and a plumule (the upper end, developing into the shoot system). Additionally, it typically includes cotyledons (embryonic seed leaves).
Seed Cotyledons
- Cotyledons are embryonic seed leaves.
- They store food for the growing embryo.
- Seeds with one cotyledon are monocotyledonous (e.g., maize, wheat).
- Seeds with two cotyledons are dicotyledonous (e.g., beans, gram).
Embryo Morphology (Dicots)
- The seedling consists of a plumule and a radicle.
- The region between the radicle and the point of attachment of the cotyledons is the hypocotyl.
- The region between the plumule and the point of attachment of the cotyledons is the epicotyl.
Seed Germination
- The process where a dormant embryo becomes active, grows out of the seed coat, and develops into a seedling.
- Factors influencing germination include moisture/water (imbibition), air (oxygen), suitable temperature, and light or darkness requirements, depending on the seed.
- Stages of Germination: imbibition, activation of enzymes, respiration, growth of the embryo, and emergence of the seedling.
- Stored food within the seed is broken down via hydrolytic enzymes which provides nutrients.
- The radicle grows downwards to form the primary root.
- The epicotyl grows in and the plumule develops into the stem and leaves.
Seed Germination Types
- Hypogeal germination: The hypocotyl grows first, pushing the plumule (shoot) above ground. The cotyledons remain in the soil, avoiding desiccation. Typical of monocots.
- Epigeal germination: The hypocotyl grows first, pushing the cotyledons above ground. The cotyledons eventually become green, enabling photosynthesis. Typical of dicots.
Seed Dormancy
- A state where seeds are prevented from germinating even under favorable environmental conditions.
- Causes of seed dormancy include:
- Hard seed coat: prevents entry of water and oxygen, thus inhibiting growth. Methods of overcoming this include mechanical, heat, or acid scarification.
- Immature embryo(Rudimentary embry): Embryo needs to develop further.
- Excessive salts: high concentration of solutes inhibiting germination.
- Light sensitivity: positive (needs light) or negative (needs dark).
- Chilling requirement for germination
- Inhibitors such as ABA inhibiting germination via metabolic changes.
Fruit Development
- Fruit develops from the mature, ripened ovary after fertilization.
- It contains one or more seeds.
- Fruit develops as the ovary wall (pericarp) thickens after fertilization.
- The three layers of the pericarp are:
- Exocarp
- Mesocarp
- Endocarp
- Fruits can be simple, aggregate, or multiple depending on the flower structure.
- Types of fruits including:
- Simple
- Aggregate
- Multiple
- Accessory
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Description
Test your knowledge on the fascinating process of seed germination. This quiz covers key topics such as hypogeal and epigeal germination, the role of cotyledons, and the importance of environmental factors. Perfect for students studying plant biology.
