SELINA Solutions for Class 9 Biology Chapter 6 - Seeds: Structure and Germination
Chapter 6 - Seeds: Structure and Germination Exercise Ex. 1
1. Which one of the following plants parts is correctly matched with one of its stated characteristic?
(a) Mango seed ___________ aleurone layer
(b) Bean seed __________ endosperm
(c) Maize grain __________ coleoptile
(d) Wheat grain ___________ exalbuminous
2. Seeds sown very deep in the soil fail to germinate because they
(a) cannot exert enough force to push the soil upward.
(b) do not get enough sunlight.
(c) get too much water.
(d) do not get enough oxygen.
1. (c) Maize grain ______ coleoptile
2. (d) do not get enough oxygen
Are the following statements true (T) or false (F)?
(a) Some seeds have no cotyledons at all. (T/F)
(b) Maize grain is fruit and not a seed. (T/F)
(c) Seeds fallen in a flower-bed from the previous crop usually do not germinate until the next sowing season. (T/F)
(d) Oxygen is necessary for the germination of seeds. (T/F)
(a) F (False). Monocotyledonous seeds contain one cotyledon and dicotyledonous seeds contain two cotyledons.
(b) T (True)
(c) T (True)
(d) T (True)
Name the following :
(a) A monocotyledonous endospermic seed.
(b) A chemical used in experiments which absorbs oxygen.
(c) Part of the plumule above the embryonic axis of the seed.
(d) A plant which shows viviparous germination.
(e) The layer of endosperm of maize rich in protein.
(f) A seed with folded plumule leaves.
(b) Pyrogallic acid
(e) Aleurone layer
Fill in the blanks:
(a) In bean seeds, ________ grows faster and the seeds are brought _________ ground.
(b) _______ is a protective layer of radicle and ________ protects the rolled plumule.
(c) A seed is protected by ________ and __________ .
(d) Seeds absorb water through ________ which also helps in diffusion of respiratory gases.
(e) Rich, wheat and maize are rich in _________ food.
(a) plumule, above
(b) Coleorhiza, coleoptile
(c) seed coat, testa
Arrange the following set of terms in order, so as to be in logical sequence. Rewrite the correct order.
(a) Embryo, 1st male gamete, zygote, egg cell, micropyle.
(b) Zygote, embryo, seed, allogamy, fusion of gametes.
(c) Seed coat bursts, hypocotyls elongates, radicle grows downward, hypocotyls forms loop above the soil, epicotyls elongates.
(a) Micropyle, 1st male gamete, egg cell, zygote, embryo
(b) Allogamy, fusion of gametes, zygote, embryo, seed
(c) Seed coat bursts, radicle grows downward, hypocotyls form loop above the soil, epicotyls elongate
What is the difference between an embryo and a seed?
A seed is a mature ovule after fertilization. It contains a tiny living-plant called the embryo. The embryo within the seed remains in an inactive or dormant state, until it is exposed to favourable conditions, when it germinates.
Give any two examples each of endospermic (albuminous) seeds, and non-endospermic (exalbuminous) seeds.
Endospermic (albuminous) seeds: E.g. Castor, Maize, Poppy
Non-endospermic (exalbuminous) seeds: E.g. Bean, Gram, Pea
Germinated grams are considered highly nutritive. What is the reason for this belief?
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.
Why do we not use the terms maize fruit and maize seed? What do we say instead?
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.
What are the functions of the following in a seed?
(a) Seed coat
(a) Seed coat: It protects the delicate inner parts of the seed from injury and the attack of bacteria, fungi and insects.
(b) Micropyle: During germination, micropyle allows water to enter the seed through its pore.
(c) Cotyledons: They contain food for the embryo.
(d) Radicle: It forms the future root.
(e) Plumule: It forms the future shoot.
Suggest an experiment to prove that a suitable temperature is necessary for germination.
Aim: To prove that a suitable temperature is necessary for germination.
Apparatus: Two beakers, wet cotton wool, refrigerator
(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.
Sometimes the potatoes kept in a basket during the late rainy season start giving out small shoots. Would you call it germination? Give reason in support of your answer.
Yes, we call it germination because all the changes leading to the formation of a seedling collectively constitute germination. During germination, either the epicotyl or the hypocotyl elongates.
Give two differences in each of the following pairs:
(a) Epigeal germination and hypogeal germination
(b) Coleorhiza and coleoptile
(c) Bean seed and maize grain
(a) Epigeal germination and Hypogeal germination
1. Cotyledons are pushed above the ground
1. Cotyledons remain underground
2. Hypocotyl elongates
2. Epicotyl elongates
(b) Coleorhiza and Coleoptile
1. Protective sheath of radicle
1. Protective sheath of plumule
2. Present towards the pointed end of embryonic region
2. Present towards the upper broader side of the embryonic region
(c) Bean seed and Maize grain
1. Two cotyledons
1. One cotyledon
2. No endosperm
2. Large endosperm present
Differentiate between germination and vivipary.
When the embryo in the seed becomes activated and begins to grow into a new plant, then it is known as germination.
Vivipary is known as the germination of seed within the fruit, while it is still attached to the parent plant.
Justify the statement that the maize grain is a 'one seeded fruit'.
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.
What is the role played by the hypocotyl in epigeal germination?
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.
With regard to germination in bean seed, answer the following questions:
(a) State the function of the 'micropyle'.
(b) Name the part of the seed that grows into the seedling.
(c) Name the part of the seed that provides nutrition for the growing seedling.
(d) Draw a neat labelled diagram of the structure named above.
(a) The 'micropyle' serves two important functions:
- Allows absorption of water and makes it available to the embryo for germination.
- 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) Structure of embryo
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