The pore in the seed coat that facilitates entry of water and oxygen is the:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Micropyle
Explanation: The micropyle remains as a small pore in the seed coat. This facilitates entry of oxygen and water into the seed during germination.
Which of the following is true about "false fruits"?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: The thalamus contributes to fruit formation.
Explanation: In a few species such as apple, strawberry, cashew, etc., the thalamus also contributes to fruit formation. Such fruits are called false fruits.
Nucellar polyembryony involves the development of embryos from:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: The nucellar cells
Explanation: Nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos.
Consider the following statements regarding double fertilisation and post-fertilisation events in angiosperms:
1. Following triple fusion, the central cell becomes the Primary Endosperm Cell (PEC) and develops into the endosperm.
2. The embryo develops at the chalazal end of the embryo sac where the zygote is situated.
3. Endosperm development precedes embryo development as an adaptation to provide assured nutrition to the developing embryo.
4. In tender coconut, the water represents cellular endosperm, while the surrounding white kernel represents free-nuclear endosperm.
Which of the above statements are correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: I and III only
Explanation: Statement 1 is correct: The text states that the central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm. Statement 2 is incorrect: The embryo develops at the micropylar end of the embryo sac where the zygote is situated, not the chalazal end. Statement 3 is correct: Endosperm development precedes embryo development. Most zygotes divide only after a certain amount of endosperm is formed, which is an adaptation to provide assured nutrition. Statement 4 is incorrect: The coconut water from tender coconut is free-nuclear endosperm (made up of thousands of nuclei), and the surrounding white kernel is the cellular endosperm.
Consider the following statements regarding double fertilisation:
1. The pollen tube releases the two male gametes into the cytoplasm of the central cell.
2. Syngamy results in the formation of a diploid zygote.
3. The primary endosperm nucleus (PEN) is triploid and formed by triple fusion.
4. The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the embryo.
Which of the above statements are correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: 2 and 3 only
Explanation: Statement 1 is incorrect: The pollen tube releases the two male gametes into the cytoplasm of the synergid, not the central cell.
Statement 2 is correct: One of the male gametes moves towards the egg cell and fuses with its nucleus (syngamy) to form a diploid zygote.
Statement 3 is correct: The other male gamete fuses with the two polar nuclei to produce a triploid primary endosperm nucleus (PEN), a process called triple fusion.
Statement 4 is incorrect: The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm, while the zygote develops into the embryo.
Consider the following statements regarding endosperm and seed development:
1. Endosperm development precedes embryo development to provide assured nutrition.
2. Castor and coconut are examples of non-albuminous seeds where endosperm is completely consumed.
3. The white kernel in coconut represents cellular endosperm.
4. Perisperm is the residual persistent nucellus found in seeds like black pepper.
Which of the above statements are correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: 1, 3 and 4
Explanation: Statement 1 is correct: Most zygotes divide only after a certain amount of endosperm is formed to provide assured nutrition.
Statement 2 is incorrect: Castor and coconut are albuminous seeds because the endosperm persists. Pea and groundnut are non-albuminous.
Statement 3 is correct: In coconut, the water is free-nuclear endosperm and the surrounding white kernel is cellular endosperm.
Statement 4 is correct: In some seeds such as black pepper and beet, remnants of nucellus are persistent and are called perisperm.
Consider the following statements regarding the structure of the embryo:
1. The portion of the embryonal axis above the level of cotyledons is called the hypocotyl.
2. In the grass family, the single cotyledon is called the scutellum and is situated laterally.
3. The coleoptile is a hollow foliar structure enclosing the shoot apex and leaf primordia.
4. The radicle and root cap in monocots are enclosed in an undifferentiated sheath called the coleoptile.
Which of the above statements are correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: 2 and 3 only
Explanation: Statement 1 is incorrect: The portion of the embryonal axis above the level of cotyledons is the epicotyl. The portion below is the hypocotyl.
Statement 2 is correct: In the grass family, the cotyledon is called scutellum and is situated towards one side (lateral) of the embryonal axis.
Statement 3 is correct: The epicotyl has a shoot apex and leaf primordia enclosed in a hollow foliar structure called the coleoptile.
Statement 4 is incorrect: The radicle and root cap are enclosed in an undifferentiated sheath called the coleorrhiza, not coleoptile.
Consider the following statements regarding fruits and seeds:
1. The wall of the ovary develops into the pericarp of the fruit.
2. In false fruits like apple and strawberry, the thalamus contributes to fruit formation.
3. Parthenocarpic fruits, such as banana, develop without fertilisation and are generally seedless.
4. Seeds of pea and groundnut are albuminous as they retain endosperm at maturity.
Which of the above statements are correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: A
Answer: 1, 2 and 3
Explanation: Statement 1 is correct: The wall of the ovary develops into the wall of the fruit called pericarp.
Statement 2 is correct: In false fruits (e.g., apple, strawberry, cashew), the thalamus also contributes to fruit formation.
Statement 3 is correct: Parthenocarpic fruits develop without fertilisation and are seedless (e.g., banana).
Statement 4 is incorrect: Seeds of pea and groundnut are non-albuminous as the endosperm is completely consumed during embryo development.
Consider the following statements regarding post-fertilisation events:
1. The zygote develops into the embryo at the chalazal end of the embryo sac.
2. Most zygotes divide only after a certain amount of endosperm is formed.
3. As the seed matures, its water content is reduced to about 10-15 per cent by mass.
4. Apomixis is a form of sexual reproduction that mimics asexual reproduction.
Which of the above statements are correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: 2 and 3 only
Explanation: Statement 1 is incorrect: The embryo develops at the micropylar end of the embryo sac where the zygote is situated, not the chalazal end.
Statement 2 is correct: This is an adaptation to provide assured nutrition to the developing embryo.
Statement 3 is correct: Mature seeds are relatively dry, with 10-15 per cent moisture content, and metabolic activity slows down.
Statement 4 is incorrect: Apomixis is a form of asexual reproduction that mimics sexual reproduction, not the other way around.
Which of the following organic materials is known to be one of the most resistant, capable of withstanding high temperatures and strong acids, and makes up the exine of pollen grains?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Sporopollenin
Explanation: The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali.