Plant Biology: Seeds and Ovules
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Questions and Answers

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?

  • 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?

  • 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?

    <p>It has a straight growth pattern.</p> Signup and view all the answers

    Which example illustrates a seed that has a raphe?

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

    What describes the physical arrangement of Colchicum seeds?

    <p>May be sessile or carried on a stalk</p> Signup and view all the answers

    Which characteristic is associated with Strophanthus seeds?

    <p>They may be carried on a stalk</p> Signup and view all the answers

    What term is used to describe the way some seeds are attached?

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

    Which of the following statements about Colchicum and Strophanthus is accurate?

    <p>Colchicum can be both sessile and stalked, while Strophanthus seeds are stalked</p> Signup and view all the answers

    What is a key difference between the seed arrangements of Colchicum and Strophanthus?

    <p>Colchicum seeds can be both sessile and stalked, while all Strophanthus seeds are only stalked</p> Signup and view all the answers

    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

    • 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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    Related Documents

    Lecture 1 Seeds, Pharmacognosy 2 (PG121) PDF

    Description

    Explore the fascinating world of seeds and their structures with this quiz. Learn about the different types of ovules and their specific characteristics, including the roles of various components like the nucellus and funicle. Test your knowledge on plant distribution and reproduction!

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