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Questions and Answers
What characteristic defines a raphe in seeds?
What characteristic defines a raphe in seeds?
- It is only present in curved seeds.
- It extends the whole length of the seed. (correct)
- It is found only in fruits.
- It is unique to only one type of seed.
What describes an atropous or orthotropous ovule?
What describes an atropous or orthotropous ovule?
- The ovule is curved.
- The growth of the ovule is uniform and straight. (correct)
- The ovule is twisted through an angle of 180º.
- The ovule bears multiple curves.
What is the unique feature of an amphitropous ovule?
What is the unique feature of an amphitropous ovule?
- It is characterized by a series of bends.
- It is rotated through an angle of 90º on its stalk. (correct)
- It does not form a stalk.
- It is formed in a spiral shape.
Which of the following statements is true regarding the growth pattern of an atropous ovule?
Which of the following statements is true regarding the growth pattern of an atropous ovule?
Which example illustrates a seed that has a raphe?
Which example illustrates a seed that has a raphe?
What describes the physical arrangement of Colchicum seeds?
What describes the physical arrangement of Colchicum seeds?
Which characteristic is associated with Strophanthus seeds?
Which characteristic is associated with Strophanthus seeds?
What term is used to describe the way some seeds are attached?
What term is used to describe the way some seeds are attached?
Which of the following statements about Colchicum and Strophanthus is accurate?
Which of the following statements about Colchicum and Strophanthus is accurate?
What is a key difference between the seed arrangements of Colchicum and Strophanthus?
What is a key difference between the seed arrangements of Colchicum and Strophanthus?
Flashcards
Orthotropous ovule
Orthotropous ovule
A type of ovule where the micropyle, chalazal end and funicle lie in a straight line.
Amphitropous ovule
Amphitropous ovule
An ovule that is curved at 90 degrees, with the micropyle and funicle close to each other.
Raphe
Raphe
A ridge formed along the length of the seed, often containing the micropyle and chalaza.
Atropous ovule
Atropous ovule
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Micropyle
Micropyle
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Awn
Awn
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Stalk (seed)
Stalk (seed)
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Colchicum
Colchicum
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Strophanthus
Strophanthus
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Sessile or stalked awn
Sessile or stalked awn
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Study Notes
Seeds
- Seeds are integumented, fertilized ovules
- They are specialized for plant distribution and continuation
Structure of Ovule
- A mature ovule contains parenchymatous tissue called nucellus
- The nucellus is surrounded by integuments
- The nucellus has a narrow opening called micropyle
- The base of the nucellus expands into a swelling called the chalaza
- The ovule is attached to the placenta by a stalk called funicle
- The funicle may fuse with the integument to form a raphe
- Vascular bundles travel through the funicle from the placenta to the chalaza
Types of Ovules
- Anatropous: The most common type, where the ovule is inverted. The raphe extends the full length of the seed
- Orthotropous (Atropous): The ovule is straight, with the micropyle at the opposite end to the chalaza
- Amphitropous: The ovule is rotated 90 degrees on its stalk
- Campylotropous: One side of the nucellus grows rapidly, while the other side's development is stunted.
- Other ovule types: These exist, but are not described in the provided information
Seed Structure
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Seeds consist of three parts:
- Seed coat (Testa)
- Stored food tissues (endosperm, perisperm)
- Embryo, which contains one to two cotyledons
Storage of Food in Seeds
- Seeds store reserve food for germination
- Reserve food is usually stored in endosperm or perisperm (or both)
- Examples of reserve food materials are carbohydrates, fats, and proteins
Forms of Embryo
- Shapes of the embryo vary based on their location inside the seed; there are "bent" "curved" and "straight" examples
- Accumbent - radicle bent against the cotyledons
- Incumbent - radicle bent against the surface of one of the cotyledons
- Orthotropous - radicle incorporated between the cotyledons
Seed Coat Structure
- Seed coats can have layers with varying properties:
- Epidermis
- Hypodermis (Can be parenchymatous or collenchymatous)
- Sclerenchymatous Layer
- Nutrient Layer
- Pigment Layer
Kernel
- The kernel is the seed without the testa
- The kernel may contain embryo, endosperm, and perisperm
- Perisperm: If present, composed primarily of thin walled parenchyma
- Endosperm: Composed of cellulosic walls surrounding reserve food materials, sometimes highly thickened
- Cotyledons: Thin cellulocic walls containing reserve food like starch/oil/aleurone
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