Parts of a Seed and Their Functions: Diagram, Structure, and Functions
Seeds are the foundation of new plant growth. They lie dormant until they receive the right conditions to germinate, such as adequate sunlight, water, and soil. In this article, we will discuss the 3 parts of a seed and show simple parts and their functions. We will also cover monocot and dicot seeds, provide learning tips, and include a short quiz at the end. Read this article to learn and understand about seeds easily.
Overview of Seed Structure
What are the parts of seeds? In general, every seed contains three major components:
Seed Coat
Endosperm
Embryo
These 3 main parts of a seed and their functions work together to ensure successful seed germination and the development of a healthy plant. Let us explore each one in detail.
Seed Coat: The Protective Shield
The seed coat is the tough outer layer that safeguards the inner components of the seed from damage, extreme temperatures, and parasites. It has two layers:
Testa: The thick outer layer which shields the seed from physical harm and prevents excessive water loss.
Tegmen: The thinner inner layer, which also helps protect the developing embryo.
Two important structures visible on some seed coats are:
Micropyle: A tiny opening through which the seed absorbs water and minerals necessary for germination.
Hilum: The scar left behind where the seed was once attached to the fruit (similar to a ‘navel’ in humans).
A strong seed coat helps prevent germination under unfavourable conditions, allowing the seed to survive until the environment is suitable.
Endosperm: The Nutrient Storehouse
The endosperm lies just beneath the seed coat in many seeds. It is a rich source of nutrition that supports the embryo until it can produce leaves and begin photosynthesis. Key points include:
Nutritional Content: Primarily composed of starch, carbohydrates, and proteins.
Role in Different Seeds:
In cereals like corn, the endosperm is a large portion of the seed.
In seeds such as beans, the endosperm is used up during embryonic development, so it is usually absent in the mature seed.
Coconuts contain liquid endosperm (the coconut water) as well as solid endosperm (the white coconut flesh).
The endosperm ensures the young embryo can remain viable until it sprouts.
Embryo: The Future Plant
The embryo is the heart of the seed. It is diploid (containing two sets of chromosomes) and develops from a fertilised egg cell. All the cells required to form a new plant are present here. The embryo has several parts:
Epicotyl: This tiny shoot will eventually develop into the plant’s shoot system (stems and leaves).
Hypocotyl: The region connecting the radicle and the cotyledons; sometimes referred to as the part that forms the primary root in certain germination types.
Radicle: The first embryonic root to appear during germination. It anchors the plant in the soil and starts absorbing water and nutrients.
Cotyledons: Also called “seed leaves”, they store food (starch and proteins) and may also appear above the ground during germination to aid in early photosynthesis.
Monocot and Dicot Seeds
Seeds can be broadly grouped into two types:
Monocotyledonous (Monocot) Seeds
Contain a single cotyledon (e.g., rice, wheat, maize).
Often, they have a large endosperm that provides nourishment to the embryo.
Dicotyledonous (Dicot) Seeds
Contain two cotyledons (e.g., bean, tomato, pea).
The cotyledons are typically fleshy and may store nutrients instead of an endosperm.
Learning the difference between monocot and dicot seeds further enriches your understanding of parts of a seed and their functions.
Practice Quiz with Answers
Test your understanding with this quick quiz:
Which part of the seed stores food for the developing embryo?
A. Seed Coat
B. Endosperm
C. Hilum
D. Micropyle
Which of the following is the first structure to emerge during germination?
A. Epicotyl
B. Radicle
C. Cotyledon
D. Hilum
Which layer of the seed coat is thick and protective?
A. Tegmen
B. Testa
C. Micropyle
D. Epicotyl
What are the parts of seeds?
A. Seed Coat, Endosperm, and Embryo
B. Testa, Tegmen, and Micropyle
C. Epicotyl, Radicle, and Cotyledons
D. Monocot and Dicot
Answers:
B
B
B
A
Related Topics
FAQs on Parts of a Seed Explained: Structure, Types and Diagram
1. Why are seeds important for plants?
Seeds play a central role in sexual reproduction. They contain the embryo that can grow into a new plant, ensuring the survival and spread of the species.
2. Why do seeds have a micropyle (tiny hole)?
This opening allows the seed to absorb water, oxygen, and essential nutrients. It also enables the radicle to emerge during germination.
3. Does every seed have an endosperm?
No. Certain seeds, such as beans, use up their endosperm during the embryo’s development. In these cases, the nutrients are stored directly in the cotyledons.
4. How do monocot seeds differ from dicot seeds?
Monocot seeds have a single cotyledon and often retain a prominent endosperm. Dicot seeds have two cotyledons, which may store nutrients in place of the endosperm.
5. How can you tell if a seed is ready to germinate?
When conditions such as temperature, moisture, and oxygen level are suitable, the seed absorbs water through the micropyle, triggering the radicle to break through the seed coat.
