Question

With reference to reproduction in flowering plants, which one of the following is incorrect?

• A. Endosperm develops into seed
• B. Ovary develops into fruit
• C. Ploidy of PEN is 3n
• D. Syngamy is the fusion of male and female gamete
• A. Heart-shaped
• B. Globular
• C. Proembryo
• D. Epiblast
• A. Free-nuclear endosperm
• B. Synergids
• C. Antipodal cells
• D. Scutellum
• A. Emasculation
• B. Triple fusion
• C. Syngamy
• D. Bagging
• A. 38
• B. 57
• C. 19
• D. 76

Answer 1

The Correct Option is A

In the process of fertilization in angiosperms, the pollen tube releases male gametes into the ovule where two fusion events take place: syngamy (fusion of male and female gametes) and triple fusion (fusion of the second male gamete with the two polar nuclei, forming the triploid endosperm nucleus).
Step 1: Analyzing the options.
- Endosperm develops into seed (Option 1): This statement is incorrect. The endosperm develops into the nutritive tissue that nourishes the developing embryo, not into the seed itself. The seed consists of the embryo, seed coat, and endosperm (nutritive tissue).
- Ovary develops into fruit (Option 2): This is correct. After fertilization, the ovary develops into a fruit that encloses the seeds.
- Ploidy of PEN is 3n (Option 3): This is correct. The ploidy of the primary endosperm nucleus (PEN) is triploid (3n), as it is formed by the fusion of one male gamete with the two polar nuclei.
- Syngamy is the fusion of male and female gametes (Option 4): This is correct. Syngamy refers to the fusion of the male and female gametes, resulting in the formation of a diploid zygote.
Step 2: Conclusion.
The statement that endosperm develops into seed is incorrect. Endosperm develops into nutritive tissue, not the seed itself.
Final Answer: \[ \boxed{\text{The correct answer is (1) Endosperm develops into seed.}} \]

Answer 2

In dicotyledon plants, the development of the embryo occurs through a series of stages. The correct stages of embryo development include:
Step 1: Analyzing the options.
- Heart-shaped (Option 1): This is a stage of embryo development in dicotyledon plants. It follows the globular stage and refers to the shape the embryo takes as it begins to form cotyledons.
- Globular (Option 2): This is another correct stage. The globular stage is when the embryo starts to differentiate into the structure of the cotyledons and the stem axis.
- Proembryo (Option 3): This stage is also correct. The proembryo is the very early stage after fertilization, where initial divisions occur and the embryo begins to form.
- Epiblast (Option 4): This is incorrect. The epiblast is not a recognized stage of embryo development in dicotyledons; it refers to an earlier, non-embryonic structure found in some plants.
Step 2: Conclusion.
The epiblast is not a stage of the growing embryo in dicotyledon plants.
Final Answer: \[ \boxed{\text{The correct answer is (4) Epiblast.}} \]

Answer 3

Coconut water is the liquid endosperm found in the coconut during the early stages of its development. It is a highly nutritious liquid that is mostly composed of free-nuclear endosperm.
Step 1: Analyzing the options.
- Free-nuclear endosperm (Option 1): This is correct. Coconut water is composed of free-nuclear endosperm, which forms in the coconut's interior as the embryo develops. It is a source of nutrients, sugars, and other beneficial compounds.
- Synergids (Option 2): Synergids are cells present in the ovule that help facilitate the fertilization process by guiding the pollen tube, not related to coconut water.
- Antipodal cells (Option 3): Antipodal cells are located in the ovule and are involved in the development of the embryo sac, not in coconut water formation.
- Scutellum (Option 4): The scutellum is a structure found in monocotyledon seeds, specifically in grass seeds like corn. It is involved in nutrient absorption, but not in coconut water.
Step 2: Conclusion.
Coconut water is made up of free-nuclear endosperm and is a highly nutritious liquid.
Final Answer: \[ \boxed{\text{The correct answer is (1) Free-nuclear endosperm.}} \]

Answer 4

The formation of the diploid zygote is a critical event in fertilization. In angiosperms, two main fusion events take place: syngamy and triple fusion.
Step 1: Analyzing the options.
- Emasculation (Option 1): Emasculation is the removal of male reproductive parts (anthers) from a flower to prevent self-pollination, and it is unrelated to the formation of the diploid zygote.
- Triple fusion (Option 2): Triple fusion is the process where one male gamete fuses with two polar nuclei to form a triploid endosperm nucleus. While important for seed development, it does not result in the formation of the diploid zygote.
- Syngamy (Option 3): Syngamy is the fusion of the male gamete (sperm) with the female gamete (egg) to form a diploid zygote. This is the direct cause of the formation of the diploid zygote.
- Bagging (Option 4): Bagging refers to the process of covering flowers to ensure controlled pollination and is not directly related to zygote formation.
Step 2: Conclusion.
The diploid zygote is formed as a result of syngamy, the fusion of the male and female gametes.
Final Answer: \[ \boxed{\text{The correct answer is (3) Syngamy.}} \]

Answer 5

In sexually reproducing organisms, the zygote is formed when two haploid cells (male and female gametes) fuse. The number of chromosomes in the zygote is the sum of the chromosomes from both gametes.
Step 1: Understanding the terms.
- The zygote is diploid (2n), meaning it has two sets of chromosomes, one from each parent.
- The haploid (n) gametes, such as eggs or sperm, each contain half the number of chromosomes compared to the diploid zygote.
Step 2: Solving the problem.
If the zygote has 38 chromosomes, it is diploid. This means each haploid gamete (egg or sperm) contributes half the chromosomes: \[ \text{Number of chromosomes in egg} = \frac{38}{2} = 19 \] Step 3: Conclusion.
The number of chromosomes in the haploid egg cell is 19.
Final Answer: \[ \boxed{\text{The correct answer is (3) 19.}} \]