Seeds - Structure and Germination

A is False and R is True.

Reason — Fruit is the enlarged ripened ovary, not the ovule. After pollination and fertilization, the ovary of the pistil develops into the fruit. The ovary wall becomes the pericarp (fruit wall).

A is False and R is True.

Reason — Both monocotyledonous and dicotyledonous seeds can be exalbuminous. Vallisneria and Orchids are examples of monocotyledonous exalbuminous seeds while gram and pea are examples of dicotyledonous exalbuminous seeds.
Dicotyledonous seeds contain two cotyledons storing food material.

Both A and R are True.

Reason — The micropyle is a small opening in the ovule through which the pollen tube enters during fertilization. After fertilization, the micropyle remains as a tiny pore that allows the entry of water and oxygen, helping in the respiration of the growing embryo.

Both A and R are False.

Reason — The single cotyledon in a maize grain is called the scutellum, not hilum. It plays a role in the absorption of nutrients from the endosperm during germination.
Hilum and micropyle are not visible in maize grain.

A is True and R is False.

Reason — In hypogeal germination, the epicotyl elongates faster, causing the plumule to emerge while cotyledons stay underground.
In epigeal germination, it is the hypocotyl that elongates not the epicotyl, lifting the cotyledons above the soil.

(a) Difference between Monocotyledonous and Dicotyledonous seeds:

(b) Difference between Epicotyl and Hypocotyl:

(c) Difference between Epigeal and Hypogeal germination:

(d) Difference between Radicle and Plumule:

(e) Difference between Albuminous and Exalbuminous seeds:

(a) Seed coat — A seed coat protects the delicate inner parts of the seed from injury and from the attack of bacteria, fungi and insects. It also plays a crucial role in regulating seed dormancy. The seed coat prevents premature germination by providing a barrier that restricts water and gas exchange.

(b) Micropyle — It serves two functions:

1. When soaked in water, the seeds absorb water mainly through the micropyle and make it available to the embryo for germination.
2. It provides for the diffusion of respiratory gases for the growing embryo.

(c) Cotyledons — Cotyledons contain food for the embryo and protect it.

(d) Radicle — Radicle is the embryonic root of the plant. It grows downward into the soil and anchors the plant, absorbing water and nutrients from the ground. It develops into the primary root of the plant, which later gives rise to the entire root system.

(e) Plumule — Plumule is the embryonic shoot of the plant. It grows upwards and is responsible for the development of the above-ground parts of the plant, including stems, branches, and leaves.

Aim — To prove that a suitable temperature is necessary for germination.

Apparatus — Two beakers, wet cotton wool, refrigerator

Procedure —

(1) Take two beakers and label them as A and B.

(2) Place some gram seeds on wet cotton wool in each of the beakers.

(3) Keep beaker A at ordinary room temperature and beaker B in the refrigerator.

(4) In 1-2 days, the seeds in beaker A will germinate, showing the importance of a suitable temperature for germination. Seeds in beaker B may not show the signs of germination or may germinate after several days, though not to the extent as the seeds in beaker A.

Inference — Seeds require a suitable temperature for germination.

No, this is not called germination. It is an example of vegetative propagation. Germination is the process of formation of a seedling developed from the embryo. In this case, the potato tuber is a modified stem, and the small shoots (called sprouts or eyes) grow directly from it without involving seeds.

(a) Two differences between Coleorhiza and Coleoptile:

(b) Two differences between Bean seed and Maize grain:

(c) Two differences between Germination and vivipary:

A fruit is the enlarged ripened ovary in which the ovarian wall forms the fruit wall and encloses the seed. The fruit protects the seed and helps in seed dispersal. The maize grain is regarded as a 'one-seeded fruit' because the fruit wall and the seed coat are fused to form a protective layer. Such a fruit is called grain.

Germination of a seed which takes place above the ground is called epigeal germination. In epigeal germination, the hypocotyl grows forming a loop above the soil. It then straightens pushing the cotyledons above the ground.

(a) Diagram of a twig of viviparous plant showing its germination:

(b) Diagram of a seedling growing in soil:

Experimental set-up of three-bean seed experiment is shown in the diagram below:

The observations of the three-bean seed experiment are as follows:

1. The middle seed germinates. It gets both oxygen and water.
2. The top seed does not germinate at all. It gets only oxygen but no water.
3. The bottom seed does not germinate or stops germinating after the emergence of a small radicle. It gets water but very little oxygen (from the air dissolved in water).

Water, suitable temperature and air (oxygen) are necessary for germination.

1. Water — Water is necessary because:
   1. By absorbing water, the seed swells and consequently the seed coat ruptures allowing the elongating radicle to come out and form the root system.
   2. Water is essential for chemical reactions and enzyme action on stored food in cotyledons or endosperm, converting it into a diffusable (dissolved) form for the developing embryo.
2. Suitable temperature — A moderately warm temperature (25°C to 35°C) is usually favourable for germination which is also called optimum temperature. A very low temperature inhibits the growth of the embryo and a very high temperature destroys its delicate tissues.
3. Oxygen — Oxygen is needed for respiration that provides energy for the rapid cell division and cell growth during germination.

Maize grain → coleoptile

Reason — Protective sheath enclosing the plumule in monocots like maize is called coleoptile.

do not get enough oxygen & cannot exert enough force to push the soil upward.

Reason — Seeds sown very deep in the soil fail to germinate because of two main reasons:

1. No proper supply of oxygen (for respiration).
2. Insufficient pushing force in the embryonic parts (hypocotyl and epicotyl) to break through the upper layers of soil.

Ovary

Reason — After fertilization the ovary grows to form fruit.

Double coconut

Reason — Double coconut has largest seed.

Hilum

Reason — Hilum is the distinct whitish oval scar on the concave side of the seed which represents the spot where the ovule was attached to ovary wall.

Scutellum

Reason — The single cotyledon of a maize grain is called Scutellum.

Testa

Reason — Seed coat consists of outermost hard brownish layer known as testa and inner layer tegmen.

Radicle

Reason — Radicle develops to form root.

All of the above

Reason — Maize is monocot with fruit wall and seed coat fused together.

Hypogeal germination

Reason — When epicotyl elongates, the cotyledons remain underground. This type of germination is known as Hypogeal germination.

P — Hypogeal, Q — Epicotyl

Reason — In hypogeal germination, the cotyledons remain below the ground. The epicotyl elongates faster, pushing the plumule above the soil.

1. False
   Corrected statement — Plumule is the future shoot and radicle is the future root of the plant.
2. True
3. False
   Corrected statement — Endosperm in castor are a big store of food for the embryo.
4. True
5. False
   Corrected statement — Testa is the outermost layer of the seed.

1. In a dry seed, the embryo is in quiescent state.
2. Water is absorbed by the seed mainly through micropyle.
3. Very low temperature inhibits the growth of embryo.
4. Germination in Pea is hypogeal.
5. Coleoptile is a part found in the germinating maize.
6. Alkaline pyrogallic acid is used for absorbing oxygen during experiments on germination.

(a) Seed — A ripened ovule, which contains embryo and has capacity to develop into a new plant is called Seed.

(b) Fruits — Enlarged and ripened ovary is called Fruit.

(c) Grain — A fruit in which the fruit wall and the seed coat is fused to form a protective layer is called Grain.

(d) Dormancy — A period of rest when the embryo is inactive inside the seed, is called Dormancy.

(e) Germination — The process of formation of a seedling from embryo is called Germination.

Germinated grams are considered highly nutritive because the cotyledon of the seed absorbs food from the endosperm, making it nutritive. It is rich in starch and its outermost layer is rich in protein.

A fruit is a fertilised ovary and a seed is a fertilized matured ovule which contains an embryo or a growing plant. Maize grain is actually a fruit in which the fruit wall and the seed coat are fused together to form a protective layer. Therefore, we do not use the terms maize fruit and maize seed. Instead, we call such fruits as grains.

(a) It is a Bean seed that is dicotyledonous.

(b) The labelled guidelines are:

• 1 → Plumule
• 2 → Radicle
• 3 → Testa
• 4 → Cotyledons

(c) Radicle grows downward into the soil and anchors the plant, absorbing water and nutrients from the ground. It develops into the primary root of the plant, which later gives rise to the entire root system.

(d) Protein

(e) Epigeal germination

(a) The 'Micropyle' serves two important functions:

1. Allows absorption of water and makes it available to the embryo for germination.
2. Enables diffusion of respiratory gases for the growing embryo.

(b) The embryo of the seed grows into the seedling.

(c) The cotyledons of the seed provide nutrition for the growing seedling or the embryo.

(d) Below is the diagram of a mature bean seed:

(a) Viviparous germination

(b) Rhizophora and Sonneratia

(c) Hypocotyl

(a) Plumule develops into the shoot system.

(b) Tegmen is the thin inner layer of the seed coat.

(c) Epithelium separates the endosperm and embryonic region in the maize grain.

(d) Epicotyl elongates faster in hypogeal germination.

(e) Dormancy is the period of rest in a seed.

(a) Maize

(b) Pyrogallic acid

(c) Shoot

(d) Rhizophora

(e) Aleurone layer

(f) Bean

(a) In bean seeds, hypocotyl grows faster and the seeds are brought above ground.

(b) Coleorhiza is a protective layer of radicle and coleoptile protects the rolled plumule.

(c) A seed is protected by testa and tegmen.

(d) Seeds absorb water through micropyle which also helps in diffusion of respiratory gases.

(e) Rice, wheat and maize are rich in starch food.

(a) Micropyle, 1st male gamete, egg cell, zygote, embryo.

(b) Allogamy, fusion of gametes, zygote, embryo, seed.

(c) Testa, Tegmen, Cotyledons, Embryonic axis.

(a) Cereals, millets

(b) Poppy, custard apple

(c) Vallisneria, orchids

(d) Pea, Gram

(e) Rhizophora, Sonneratia

(a) Monocots, Dicots

(b) Albuminous, Exalbuminous

(c) Water, Suitable temperature, Oxygen

(d) Epigeal, Hypogeal

(e) Testa, Tegmen