Biology Seed Structure and Function Quiz

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Questions and Answers

What structure surrounds the embryo in a seed?

  • Testa
  • Endosperm (correct)
  • Seed coat
  • Cotyledon

What are cotyledons?

  • The first leaves of the developing embryo (correct)
  • The main stem of the plant
  • The roots of the plant
  • The male reproductive cells

The testa is the innermost layer of a seed.

False (B)

What is the primary function of the endosperm in a seed?

<p>To provide nourishment to the developing embryo.</p> Signup and view all the answers

Fertilization involves the fusion of the male nucleus with the female nucleus.

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

What is fertilization?

<p>The fusion of the male nucleus with that of the egg.</p> Signup and view all the answers

The seed is composed of the embryo and the ________.

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

Match the following seed components with their descriptions:

<p>Embryo = The developing plant within the seed Endosperm = Nourishing tissue surrounding the embryo Testa = Protective outer layer of the seed Cotyledon = First leaves that emerge from a germinating seed</p> Signup and view all the answers

The ____ are the first leaves of the developing embryo.

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

Match the following terms with their descriptions:

<p>Embryo = A developing plant that arises from fertilization Cotyledon = The first leaves of a seedling Fertilization = The process of nucleus fusion Male nucleus = The reproductive cell from the male parent</p> Signup and view all the answers

What is formed from the union of one sperm with the egg cell?

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

The endosperm is formed from the union of a sperm with the egg cell.

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

What is the first part to emerge from the developing seed?

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

In double fertilization, one sperm fertilizes the egg cell to form the embryo, while the other sperm fuses with ______ nuclei to form the endosperm.

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

What is the primary function of the seed coat?

<p>To protect the kernel tissues (D)</p> Signup and view all the answers

The term 'Orthoplocous' refers to a type of seed coat.

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

What are the two primary types of embryo mentioned?

<p>Radical bents and Cotyledons</p> Signup and view all the answers

A seed is formed of one or two seed _____ that protect the kernel.

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

What is the primary structure of simple aleurone grains?

<p>Amorphous mass of protein enveloped by a protein membrane (B)</p> Signup and view all the answers

All aleurone grains consist of a crystalloid structure.

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

What is the characteristic of aleurone grains found in leguminous seeds?

<p>Simple structure with an amorphous mass of protein</p> Signup and view all the answers

Aleurone grains can be either simple in structure or consist of __________.

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

Match the following structures with their descriptions:

<p>Simple aleurone grains = Amorphous mass of protein Crystalloid aleurone grains = Crystalline structure</p> Signup and view all the answers

What does the raphe connect in a seed?

<p>The hilum to the chalaza (B)</p> Signup and view all the answers

The raphe is located at the top of the seed near the flower.

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

What is the role of the raphe in a seed?

<p>It connects the hilum to the chalaza.</p> Signup and view all the answers

The raphe is a line running from the _____ to the chalaza.

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

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Flashcards

Radicle

The first part of a plant embryo to emerge from the seed.

Double Fertilization

The process where one sperm fertilizes the egg cell to form a diploid (2n) embryo and another sperm fertilizes the central nuclei to form a triploid (3n) endosperm.

Endosperm

The nutritive tissue in a seed that provides food for the developing embryo.

Egg cell

The female gamete that is fertilized by a sperm to form the embryo.

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Fertilization

The process of a pollen grain reaching the ovule and fertilizing the egg cell.

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Cotyledons

The first leaves of the developing plant embryo.

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Zygote

The fertilized egg cell that develops into the plant embryo.

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Embryonic development

The process involving many steps from fertilization to the formation of a mature embryo.

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What is the Raphe?

The stalk connecting the seed to the ovary wall, running from the hilum to the chalaza.

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What is the endosperm's function?

Endosperm is the nutritive tissue inside the seed that nourishes the developing embryo. It's like a food supply for the baby plant.

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What are endospermic seeds?

Seeds with endosperm present at maturity. The embryo uses this tissue as nourishment during germination.

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What are non-endospermic seeds?

Seeds where the endosperm is fully consumed by the embryo before seed maturation. The embryo has all the food it needs within itself.

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What is an embryo?

The embryo is the developing baby plant within the seed, destined to grow into a new plant.

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Testa

The outer protective layer of the seed, often hard and tough.

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Endosperm development

The initial stage of development where the endosperm nucleus rapidly divides to form the food-rich endosperm tissue.

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Embryo

The developing plant within the seed, containing all the necessary parts for future growth.

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Seed structure

The structure formed when the embryo and endosperm are enclosed within the protective testa.

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What are simple aleurone grains?

Aleurone grains in some seeds, like those of legumes, are simple. They consist of a protein mass enveloped in a protein membrane.

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What is a crystalloid in aleurone grains?

Aleurone grains in some seeds are complex and contain a structure called a crystalloid. This structure consists of proteins and is found within the aleurone grain.

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What are aleurone grains?

Aleurone grains are specialized cells found in seeds, particularly in the outermost layer of the endosperm.

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What is the function of aleurone grains?

Aleurone grains play a crucial role in germination. When a seed sprouts, they release enzymes that break down the stored food reserves, providing nourishment for the growing embryo.

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What else is found in complex aleurone grains besides a crystalloid?

In addition to a crystalloid, complex aleurone grains also contain a globoid, which is composed of calcium and phosphorus compounds.

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What is the Radicle?

The first part of a plant embryo to emerge from the seed, usually growing downward and developing into the root system.

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What are seed coats?

The protective outer layers of a seed, often containing one or two cotyledons (seed leaves).

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What is a bent radicle?

The bending of the radicle during seed germination, ensuring the root grows downwards for anchoring and water absorption.

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What are cotyledons?

The first leaves of a developing plant embryo, often containing stored food reserves for the young seedling.

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What is the difference between monocots and dicots?

Describes the number of cotyledons (seed leaves) present within a seed. Monocots have one, and dicots have two.

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Study Notes

Course Information

  • Course Title: Pharmacognosy II
  • Course Code: PG303
  • University: Egyptian Chinese University

Course Assessment

  • Periodic exam: 20 marks
  • Practical exam: 40 marks
  • Oral exam: 15 marks
  • Final exam: 75 marks

Week 1: Introduction to Seeds

  • Seeds are mature, fertilized ovules containing an embryo.
  • Ovules develop into seeds.
  • Pollination is the process of pollen landing on the stigma.
  • This leads to fertilization.
  • After fertilization, the ovary swells and develops into the fruit, which encloses the seed.
  • Images of various seeds were presented.

Introduction to Seeds (Definition)

  • Seeds are plant parts that develop from fertilized ovules.
  • They contain an embryo, which has the potential to develop into a new plant.

Parts of a Pea Flower & Pea Pod

  • Parts of a pea flower were labeled: stigma, ovary wall, ovule, fruit wall, and seed.
  • Components of a pea pod were labelled: stigma, ovary wall, ovule, fruit wall, and seed.

Pollination and Fertilization of a Flower

  • Pollination occurs when pollen lands on the stigma of a carpel.
  • A pollen tube grows down the style of the carpel to the ovary, carrying the sperm cells.
  • Fertilization involves the fusion of the sperm with the egg cell and the central cell.

Function of Seeds

  • Seeds ensure the continuation and distribution of plants.
  • Seeds facilitate transportation.

Structure of the Ovule

  • Integuments form the seed coat (testa) that protect the embryo.
  • Micropyle: opening for pollen tube entry.
  • Nucellus: tissue for nutrition.
  • Endosperm: nutritive tissue.
  • Embryo sac: contains the egg cell.
  • Chalaza: basal part of the nucellus.
  • Funicle: stalk that attaches the ovule to placenta.

Structure of the Ovule (continued)

  • Testa: protective seed coat.
  • Micropyle: a small opening for pollen tube entry.
  • Nucellus: tissue containing stored food.
  • Perisperm: nutritive tissue, sometimes developed from nucellus.
  • Endosperm: nutritive tissue, derived from fusion of sperm and central cell.
  • Embryo sac: contains egg cell and other cells.
  • Embryo: developed from fertilized egg cell.

After Fertilization of the Ovule

  • Integuments: develop into the seed coat (testa).
  • Nucellus: may develop into perisperm.
  • Endosperm: develops to provide nutrients for the developing embryo.

Types of Seeds (Based on Endosperm)

  • Exalbuminous seeds: do not have endosperm, the embryo develops rapidly, and nutrients are stored in cotyledons.
  • Albuminous seeds: have endosperm, the embryo remains small, and the nucellus develops into perisperm to store additional nutrients.

External Appearance of a Seed

  • Testa: seed coat (outer layer).
  • Hilum: scar where seed was attached to funicle.
  • Micropyle: small opening.
  • Position of radicle: location of the future root..

Types of Ovules

  • Atropous: straight.
  • Anatropous: inverted.
  • Amphitropous: partly bent.
  • Campylotropous: bent upon itself.
  • Raphe: line on ovule, formed by the fusion of funicle with the integument.

A Typical Seed

  • Testa: seed coat, originated from integument, protects the kernel.
  • Kernel: embryo and nutritive tissue –endosperm/perisperm, enclosed by testa.

Types of Embryos

  • Various classifications of embryos were reviewed and illustrated.

Types of Outgrowths

  • Arillus: from funicle/hilum; entire seed enveloping, e.g., Cardamom.
  • Arillode: from micropyle, covers part of seed, e.g., Nutmeg.
  • Caruncle: localized fleshy outgrowth from neighborhood of micropyle e.g., Ricinus.
  • Strophiole: local enlargement, e.g., Colchicum.
  • Wing: membranous extension, e.g., Strophanthus.
  • Tuft of hairs: on stem, Apocyanaceae family; awn-like hairs on stalk, Strophanthus genus.

Testa Types (Texture)

  • Membranous
  • Leathery
  • Hard
  • Woody
  • Fleshy

Testa Types (Shape)

  • Longitudinally striated
  • Smooth
  • Papillose
  • Pitted
  • Reticulate
  • Hairy
  • Rugged

Microscopical Characters

  • Testa and outgrowths, if present.
  • Perisperm: parenchyma cells containing starch.
  • Endosperm: containing starch, protein, or fixed oils
  • Embryo
  • Cell contents: Starch, protein, Fixed oils

The Testa:

  • Formed from one or two integuments.
  • Four basic layers: epidermis, hypodermis, sclerenchymatous layer, and nutritive/hyaline layer.
  • Pigment layer: contributes to the seed's color.

Reserved Food Material

  • Carbohydrates (Starch, cellulose, hemicellulose)
  • Fixed oils and proteins (aleurone grains).

Types of Aleurone Grains

  • Simple: Amorphous mass of protein enveloped in a protein membrane –e.g. legumes seeds.
  • Compound: Consist of crystalloid and globoid embedded within a protein matrix.

Ground Substance, Crystalloids, and Globoids

  • Ground substance: amorphous matrix surrounding the grains.
  • Crystalloids: proteinoid matter crystals.
  • Globoids: rounded or ovoid shape, insoluble in water.

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Pharmacognosy II PG303: Seed Structure and Morphology PDF

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