Pharmacognosy II: Introduction to Seeds

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Questions and Answers

What is the hilum in a seed?

The outer layer of the seed

The scar left by removal of seed from its funicle (correct)

The structure that transports nutrients

The area where the seed undergoes photosynthesis

What role does the micropyle serve in a seed?

It allows for nutrient absorption

It protects the seed from pests

It aids in water transport during germination (correct)

It stores energy for the seed

Why is the micropyle an important feature of the seed coat?

It prevents water loss

It serves as a passage for water during germination (correct)

It enhances seed color for attraction

It allows air exchange

What results from the removal of a seed from its funicle?

The creation of the hilum (A) Signup and view all the answers

Which statement best describes the seed coat's apex?

It is incomplete, leading to the formation of the micropyle (B) Signup and view all the answers

What is the primary transformation that occurs to ovules?

They transform into seeds (A) Signup and view all the answers

What happens to the ovary after the ovules transform?

It swells and enlarges to form the fruit (B) Signup and view all the answers

Which of the following best describes the relationship between seeds and fruit?

Fruit encloses the seeds that develop from ovules (B) Signup and view all the answers

Which of the following statements about seeds is true?

Seeds cannot develop without the ovary (D) Signup and view all the answers

What is the role of the ovary in seed formation?

It encloses and protects the developing seeds (D) Signup and view all the answers

What is the main function of the endosperm in a typical seed?

Provide nutrients to the embryo (A) Signup and view all the answers

Which part of the seed is developed from the fertilized egg ovum?

Embryo (A) Signup and view all the answers

Which structure originates from the nucellus?

Perisperm (A) Signup and view all the answers

What does the testa in a seed refer to?

The outer protective layer (B) Signup and view all the answers

Which of the following statements about the kernel is correct?

It encompasses all layers enclosed within the testa (C) Signup and view all the answers

What are cotyledons commonly known as in the context of plant development?

The first leaves (B) Signup and view all the answers

Which best describes fertilization in plants?

The fusion of the male nucleus with that of the egg (C) Signup and view all the answers

What is the primary function of the cotyledons during early seed development?

Storage of nutrients for the embryo (B) Signup and view all the answers

In the context of fertilization, what is the outcome of the fusion process?

Formation of a seed (B) Signup and view all the answers

Which of the following statements about embryos and cotyledons is true?

Cotyledons are the first leaves arising from the developing embryo. (C) Signup and view all the answers

What is the primary difference between exalbuminous and albuminous seeds?

Exalbuminous seeds do not have an endosperm. (D) Signup and view all the answers

Which seed type is associated with the presence of a well-developed perisperm?

Exalbuminous seeds (D) Signup and view all the answers

What structure in the seed is responsible for the seed's external appearance including the position of the radicle?

Testa (D) Signup and view all the answers

In which type of seeds does the endosperm develop?

Albuminous seeds (B) Signup and view all the answers

What is the role of the micropyle in seed anatomy?

It serves as an entry point for water during germination. (A) Signup and view all the answers

What is the primary distinction between exalbuminous seeds and albuminous seeds?

Exalbuminous seeds develop without the endosperm, while albuminous seeds rely on it for nutrition. (C) Signup and view all the answers

In the development of exalbuminous seeds, which part is typically absorbed during the process?

The nucellus (C) Signup and view all the answers

What is the characteristic feature of the zygote in exalbuminous seeds?

It develops rapidly and forms an embryo. (B) Signup and view all the answers

Which of the following seeds is an example of exalbuminous seeds?

Beans (C) Signup and view all the answers

In the context of seed development, what role does the testa play in exalbuminous seeds?

It protects the developing embryo from environmental damage. (D) Signup and view all the answers

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Study Notes

Course Information

Course Name: Pharmacognosy II
Course Code: PG303
University: Egyptian Chinese University
Faculty: Faculty of Pharmacy and Drug Technology

Course Grades

Periodical exam: 20 marks
Practical exam: 40 marks
Oral exam: 15 marks
Final exam: 75 marks

Week 1: Introduction to Seeds

Topics Covered: Seed structure, diagram showing parts of pea flower and pea pod; different examples of seeds like dandelions, chestnuts, etc.
Seed Definition: A seed is a plant part derived from a fertilized ovule. It is a mature fertilized ovule containing an embryo.
Ovule Transformation: Ovules transform into seeds.
Ovary Enlargement: The ovary swells and enlarges to form the fruit that encloses the seeds.
Parts of a Flower: Images displaying the stigma, ovary wall, ovule (with a focus on pea flower and pea pod)

Introduction to Seeds

Key facts about Seeds: A mature fertilized ovule with an embryo inside.

Structure of the Ovule

Key Parts of a Mature Ovule:
- Integuments: protective outer covering
- Testa: Protection of the seed
- Micropyle: Opening for pollen tube entrance.
- Nucellus: nutritive tissue, often contains perisperm
- Endosperm: nutritive tissue.
- Embryo sac/Megaspore: Contains the embryo.
- Embryo: the developing organism.
- Funicle: small stalk that attaches the ovule to the placenta.
- Chalaza: The basal part of the nucellus where the integuments attach

Structure of the Ovule (Continued)

Parts and their Roles: Each part has a specific function.

Pollination and Fertilization

Pollination Details: Pollen landing on the stigma of the flower starts the process. The pollen tube grows down in the style to the ovule.
Double Fertilization: One sperm fertilizes the egg cell, and the other sperm fuses with polar nuclei to form endosperm.
Seed Formation: The seed develops from the fertilized ovule, after pollination and fertilization. The embryo sac (inside the ovule) develops into embryo.

Function of Seeds

Key Functions of Seeds:
- Ensure continuation and distribution of the species.
- Facilitate transportation to new locations.

Fertilization and Development of Embryo

Fertilization Definition: The fusion of male and female nuclei.
Pollen Tube Entry: The pollen tube enters the ovule through the micropyle. Inside it enters the embryo sac.
Embryo Development: The embryo's formation causes changes in the ovule and ovary.
Seed Development: The ovule's swelling and development into a seed.
Testa Function: The testa protects the embryo from injury and drying during this process.

The Mature Ovule

Nucellus: Parenchymatous tissue
Chalaza: Basal part of the nucellus.
Funicle: Stalk attaching ovule to placenta.
Embryo Sac: Contains cells crucial for future development.

Raphe

Raphe formation: Fusion of the funicle with the integument.

Types of Ovules

Anatropous: Ovule flipped 180 degrees with the micropyle adjacent to the hilum and the chalaza at the distal end.
Orthotropous: Straight ovule, funicle runs in a straight line with micropyle, chalaza, and hilum in same straight line (no raphe).
Amphitropous: Ovule is bent so that micropyle and chalaza are on a line perpendicular to the funicle.
Campylotropous: Bent ovule with micropyle and chalaza close to each other.

External Appearance of a Seed

Markings: Hilum (scar) where seed was attached to funicle, Micropyle (opening), position of the radicle.
Testa: Seed coat.

Types of Seeds

Exalbuminous: Non-endospermic (e.g. beans)
Albuminous: Endospermic (e.g. grasses)
Perisperm: Perisperm is a nutritive tissue that arise from cells of the nucellus.

Types of Embryo

Orthotropous, Accumbent, Incumbent, Coiled

Types of Outgrowths

Arilus (from funicle/hilum), Arillode (from micropyle), Caruncle (from the tissue surrounding micropyle), Strophiole (local enlargement over position of raphe) , Wing (membranous), Tuft of hairs (sessile/stalked)

The Testa (Texture and Shape)

Membranous (Almond)
Leathery (Linseed)
Hard (Nutmeg)
Woody (Calabar bean)
Fleshy (Mangolia)
Longitudinally striated (Almond)
Smooth (Linseed)
Papillosed (Grain of paradise)
Pitted (Digitalis)
Reticulated (Poppy)
Hairy (Nux vomica)
Rugged (Cardamom)

Microscopical Characters

Testa: Layers (e.g., epidermis, sclerenchyma, nutritive)
Perisperm: Parenchyma cells with starch.
Endosperm: Parenchyma cells with starch, protein, and fixed oils.
Embryo
Cell Contents: Starch, protein, fixed oils

Reserved Food Materials

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

Types of Aleurone Grains

Simple: Amorphous protein mass surrounded by membrane (leguminous seeds).
Complex: Crystalline (e.g., crystalloid), Globose (e.g.,globoid) embedded in protein.

Ground and Globoids Substance

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Description

This quiz covers the fundamental concepts of seeds, including their structure, development from ovules, and examples from various plants like dandelions and chestnuts. Additionally, it explores the anatomy of flowers, focusing on parts involved in seed formation. Test your knowledge on these essential topics in Pharmacognosy.