The Seed

You, of course, hate the seed when you are savouring your favourite watermelon. However, are you aware that without the seeds, you can’t get to eat and enjoy that fruit at all? Seeds are important for plants in more ways than you can actually imagine! In this chapter, we will look at the types of seed and study about their characteristics in more detail.

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What is the Seed?

A seed is a basic part of any plant. The ovules after fertilization, develop into seeds. A seed is made up of a seed coat and an embryo. The embryo is made up of a radicle, an embryonal axis and one (wheat, maize) or two cotyledons (gram and pea). A seed is found inside a fruit which converts into a new plant when we plant it. Hence, the seed is the most important part.

Let us now look at the different types of seeds and study their characteristics.

Types of Seeds

A Seed is primarily of two types. The two types are:

• Monocotyledonous Seed
• Dicotyledonous Seed

Let us now study about these types of seeds in brief.

Structure of a Monocotyledonous Seed

A Monocotyledonous seed, as the name suggests, has only one cotyledon. There is only one outer layering of the seed coat. A seed has the following parts:

• Seed Coat: In the seed of cereals such as maize, the seed coat is membranous and generally fused with the fruit wall, called Hull.
• Endosperm: The endosperm is bulky and stores food. Generally, monocotyledonous seeds are endospermic but some as in orchids are non-endospermic.
• Aleuron layer: The outer covering of endosperm separates the embryo by a proteinous layer called aleurone layer.
• Embryo: The embryo is small and situated in a groove at one end of the endosperm.
• Scutellum: This is one large and shield-shaped cotyledon.
• Embryonal axis: Plumule and radicle are the two ends.
• Coleoptile and coleorhiza: The plumule and radicle are enclosed in sheaths. They are coleoptile and coleorhiza.

Learn more about the Morphology of Flower here.

Structure of a Dicotyledonous Seed

Unlike monocotyledonous seed, a dicotyledonous seed, as the name suggests, has two cotyledons. It has the following parts:

• Seed coat: This is the outermost covering of a seed. The seed coat has two layers, the outer testa and the inner tegmen.
• Hilum: The hilum is a scar on the seed coat through which the developing seed was attached to the fruit.
• Micropyle: It is a small pore present above the hilum.
• Embryo: It consists of an embryonal axis and two cotyledons.
• Cotyledons: These are often fleshy and full of reserve food materials.
• Radicle and plumule: They are present at the two ends of the embryonal axis.
• Endosperm: In some seeds such as castor, the endosperm formed as a result of double fertilisation, is a food storing tissue. In plants such as bean, gram and pea, the endosperm is not present in the matured seed. They are known as non-endospermous.

Solved Question for You

Question: What are the types of mature seeds?

Solution: We know two types of mature seeds. These are:

• Non-albuminous – These seeds do not contain any residual endosperm to store the food. Example: pea, groundnut.
• Albuminous – These seeds consist of an endosperm to function as a storage for the food. Example: wheat, maize.

FAQ’s for You

Q.1 Which part of the seed is used to protect the seed?

Answer: There are three parts of a plant seed, namely seed coat, endosperm and embryo. Seed coat protects the seed from physical, mechanical, temperature-related and water damage. Cotyledon is an embryonic leaf present within the seed of a plant. Embryo consists of precursor tissues for different parts of plants.

Q.2 Which microorganism destroys the seed?

Answer: The most common microorganism that destroys the seed is fungi. If the moisture content of the seed is higher, it results in growth of fungus in seeds. Fungus can damage the seeds before it emerges from the soil. It causes seed rot.

Q.3 Which plant leaves are used to protect the seed from the insects?

Answer: Neem plant leaves are used to defense seeds against insects. It contains various compounds which act as insecticides. For example, one of the neem component, azadirachtin, interrupts metamorphosis of insect larvae. Another neem component, salannin, acts as insect repellent.

Q.4 The seed contains the future plant or embryo which develops into seedling under appropriate conditions.

Answer: Seeds contains embryo which develops into a seedling when grown under optimum conditions. The endosperm inside the seeds helps in the growth and development of the embryo. It has starch as stored nutrition which allows the rapid growth of embryo. It also stores oil.