Maharashtra Board Class 11 Agriculture Science and Technology Chapter 4 Seed PDF Download

Seed

4.1 Definition And Type

4.1.1 Definition

A fruit is defined as matured or ripened ovary which contains one or more ovules that develops into seed. Botanically seed is defined as matured (after fertilization) and ripened ovule which contains an embryo with food reserve and protective coat. As per seed technology science or agricultural point of view seed is any plant part which is used for raising or propagation or multiplication of new commercial crop. For example: True seed, tubers, suckers, bulbs, cuttings, sets, grafts, etc.

Teacher's Note

In India, farmers use many types of seeds to grow crops. A mango seed is a true seed, but a potato is also called a seed because we use it to grow new potato plants.

Exam Trick

Remember: A seed has an embryo (baby plant) inside it. But anything we plant to grow a new plant can be called a seed. So both true seeds and potatoes are "seeds" for farming.

Points to Remember

A seed is a ripened ovule after fertilization.
Seeds have an embryo, food, and a protective coat.
We can use many plant parts as seeds to grow new plants.
True seeds, tubers, and bulbs are all types of seeds used in farming.

4.1.2 Parts Of Seed

Structure Of Dicot Seed

Castor Seed:

Castor seed has two layers. The outer layer of seed coat is testa which is blackish and hard. The inner thin seed coat layer is tegmen. The spongy whitish outgrowth present at one end of seed and it is called caruncle. Caruncle absorbs water during germination. Hilum which is covered by caruncle and raphe which run from hilum on the seed coat.

There is a whitish flattened body called endosperm. It acts as food storage tissue. Seed embryo consists of radical, axis and plumule. There are two cotyledons which have prominent veins. It acts as food sucking organ.

Teacher's Note

Castor seeds are used to make castor oil in India. If you cut open a castor seed, you can see all these parts easily with a knife.

Exam Trick

Castor seed = two layers = testa + tegmen. The caruncle looks like a small bump on the seed. It drinks water first during germination.

Points to Remember

Testa is the hard outer layer of castor seed.
Tegmen is the thin inner layer below testa.
Caruncle is a whitish bump that absorbs water.
Endosperm stores food for the baby plant.
Cotyledons are the two food storage leaves.

Structure Of Monocot Seed

Maize Seed

Maize seed coat is membranous layer adherent to the grain and is fused with the wall of the fruit. Seed is somewhat flattened. It is broader at one end and pointed at other end. The flattened portion of the seed may be creamy white, yellow or dark red in colour with distinct deloid area. Note that scar is present at both ends of the seed. The scar present at the broader end of the seed is the position of attachment of style. The scar at the narrow end is hilum. Observe that ridge is present in the centre of the seed which is axis of the embryo by cutting the seed through the centre longitudinally and putting few drops of dilute iodine on it. Two distinct regions separated from each other by a layer. Separating layer is called epithelium which secrets enzymes.

The bigger region which takes violet black stain is called endosperm. It is rich in starch. The embryo consists of radical, plumule and a single shield shaped cotyledon called scutellum. Scutellum absorbs food material from endosperm during germination.

Note that radical is towards pointed end and is surrounded by a sheath called coleorhiza. The plumule which is at the end of the embryo is surrounded by sheath called coleoptile.

Teacher's Note

Maize is also called corn. You eat maize as popcorn. Inside each maize grain, there is a baby plant waiting to grow when you plant it in soil.

Exam Trick

Maize = one cotyledon = monocot. Scutellum is shield-shaped and sucks food from endosperm. Remember: Maize seed is flat like a coin!

Points to Remember

Maize seed is somewhat flattened and broader at one end.
Endosperm is the big region that stores starch.
Scutellum is the single cotyledon that looks like a shield.
Coleoptile protects the plumule.
Coleorhiza protects the radicle.

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