SEXUAL REPRODUCTION IN FLOWERING PLANTS 2 MARKS QUESTIONS WITH ANSWERS
Before you begin, Read and revise notes here: SEXUAL REPRODUCTION IN FLOWERING PLANTS – Notes
1. Mention four wall layers of microsporangium.
Answer: A typical microsporangium is generally surrounded by four wall layers: the epidermis, endothecium, middle layers, and the tapetum.
2. Write a note on tapetum.
Answer: 1️⃣ The tapetum is the innermost wall layer of the microsporangium. 2️⃣It nourishes the developing pollen grains. 3️⃣Cells of the tapetum are highly specialized, possessing dense cytoplasm and generally having more than one nucleus.
3. Mention two differences between microsporogenesis and megasporogenesis.
Answer:
| Microsporogenesis | Megasporogenesis |
| 1. It is the process of the formation of microspores from a pollen mother cell (PMC) through meiosis. | 1. It is the process of the formation of megaspores from a megaspore mother cell (MMC) through meiosis. |
| 2. It results in the formation of a microspore tetrad, where the microspores eventually dissociate and develop into pollen grains. | 2. It results in the formation of four megaspores, out of which usually only one remains functional (developing into the embryo sac) while the other three degenerate. |
4. Complete the tabular column given below with respect to the male gametophyte of angiosperms.
| Cells of the male gametophyte | |
| Shape of nucleus of the cells |
Answer:
| Cells of the male gametophyte | Vegetative cell | Generative cell |
| Shape of nucleus of the cells | Large, irregularly shaped nucleus | Spindle-shaped / oval shaped |
5. Write the significance of sporopollenin.
Answer: 1️⃣Sporopollenin is one of the most resistant organic materials. 2️⃣It makes the exine (outer layer) of the pollen grain extremely hard. 3️⃣It allows the pollen to withstand high temperatures, strong acids, and alkalis, and ensures pollen grains are well-preserved as fossils.
6. What is filiform apparatus? What is its significance?
Answer: The filiform apparatus consists of special cellular thickenings located at the micropylar tip of the synergids. Its significance is that it plays an important role in guiding the pollen tubes into the synergid
7. Differentiate between chasmogamous and cleistogamous flowers.
Answer:
| Chasmogamous Flowers | Cleistogamous Flowers |
| Chasmogamous flowers have exposed anthers and stigma. | Cleistogamous flowers remain closed and the anthers and stigma lie close to each other. |
| Chasmogamous flowers are usually cross-pollinated. Cross pollination requires pollinators. | Cleistogamous flowers can only carry out self-pollination. |
| To promote cross-pollination, chasmogamous flowers often have attractive colored petals and nectar guides to attract and reward pollinators. | Cleistogamous flowers do not need pollinators or attractive floral parts or nectaries to reward pollinators. |
| In chasmogamous flowers, the seeds produced are genetically distinct. | Cleistogamous flowers produce assured seed sets even in the absence of pollinators. |
8. Cleistogamous flowers are invariably autogamous. Justify.
Answer: Cleistogamous flowers do not open at all. Because they remain closed, there is no chance of cross-pollen landing on the stigma, making them invariably autogamous (strictly self-pollinating).
9. Cleistogamous flowers produce assured seed set even in the absence of pollinators. Justify.
Answer: In cleistogamous flowers, the anthers and stigma lie very close to each other in a closed bud. When the anthers dehisce, pollen grains directly come in contact with the stigma to effect pollination, ensuring a seed set without the need for external pollinators.
10. What are cleistogamous flowers? Name a plant showing this.
Answer: Cleistogamous flowers are flowers that do not open at all. Examples of plants producing these flowers include Viola (common pansy), Oxalis, and Commelina.
11. Differentiate between geitonogamy and xenogamy.
Answer:
| Geitonogamy | Xenogamy |
| Geitonogamy is the transfer of pollen to the stigma of another flower of the same plant | Xenogamy is the transfer of pollen to the stigma of another flower of the different plant |
| It involves flowers of the same plant | It involves flowers of the different plants |
| Functionally cross-pollination but pollen grains are genetically identical | Cross-pollination and pollen grains are genetically different |
| Cannot occur in dioecious plants | Dioecious plants show xenogamy |
12. List the characteristic features of wind pollinated flowers.
Answer: Characteristics of Wind-pollinated Flowers:
- Produce light and non-sticky pollen grains.
- Possess well-exposed stamens.
- Have large, often-feathery stigmas to trap air-borne pollen.
- Usually have a single ovule in each ovary.
- Flowers are packed into inflorescences.
- Flowers are not very colourful.
- Do not produce nectar.
13. Mention any two floral rewards offered by insect pollinated flowers to their pollinators.
Answer: 1️⃣The usual floral rewards offered to insects are nectar and pollen grains. 2️⃣In some specific cases, the reward is providing a safe place to lay eggs (such as in Amorphophallus and Yucca).
14. “The flowering plants have evolved strategies to prevent self-pollination”. Justify by giving two reasons.
Answer: Continued self-pollination results in inbreeding depression. To discourage this, plants have evolved devices such as non-synchronization of pollen release and stigma receptivity, placing the anther and stigma at different positions (herkogamy), self-incompatibility, and the production of unisexual flowers.
15. Define: a) Emasculation b) Bagging
Answer: a) Emasculation: The removal of anthers from the flower bud of a bisexual female parent before the anther dehisces.
b) Bagging: The process of covering the emasculated flowers with a bag (generally made of butter paper) to prevent contamination of its stigma with unwanted pollen.
16. Define a) Syngamy b) Triple fusion.
Answer: a) Syngamy: The fusion of one male gamete with the nucleus of the egg cell to form a diploid cell called the zygote.
b) Triple fusion: The fusion of the second male gamete with the two polar nuclei located in the central cell of the embryo sac to produce a triploid primary endosperm nucleus (PEN).
17. Name the four stages in dicotyledonous embryo development.
Answer: Following zygote formation, the embryo passes through the proembryo stage, and subsequently develops into the globular, heart-shaped, and mature embryo stages.
18. Draw a neat labeled diagram of a typical dicotyledonous embryo.
Answer:
19. Distinguish between albuminous and non-albuminous seeds.
Answer:
| Albuminous Seeds | Non-Albuminous Seeds |
| Seeds that retain a part of the endosperm (albumen) at maturity. | Seeds that do not have endosperm at maturity and the food is stored in the cotyledons. |
| Food is stored in the endosperm. | Food is stored in the cotyledons. |
| Maize, wheat, castor, sunflower | Pea, gram, bean, groundnut |
| Usually one or two, often thin and membranous because endosperm is present. | Usually two, thick and fleshy as they store food. |
| Mostly monocot seeds | Mostly dicot seeds |
| Acts as a food reserve for the developing embryo. | Endosperm is absorbed during seed development. |
20. What is perisperm? Give an example.
Answer: Perisperm is the residual, persistent nucellus that occasionally remains in some mature seeds.
Examples: black pepper and beet.
21. Differentiate between false fruit and true fruit.
Answer:
| True Fruit | False Fruit |
| Develops from the ovary only | Develops from ovary and other floral parts |
| Tomato, guava, pea | Apple (from receptacle), strawberry (from receptacle and calyx) |
| Only ovary tissue forms the fruit | Other floral parts like receptacle, calyx contribute |
22. Why apple is called a false fruit? Which part(s) of the flower forms the fruit?
Answer: Apple is called a false fruit because the thalamus also contributes significantly to fruit formation. In the apple, both the ovary and the fleshy thalamus form the fruit.
23. What is parthenocarpy? Give an example.
Answer: Parthenocarpy is the phenomenon in which fruits develop without fertilisation. A common example of a parthenocarpic fruit is the banana.
24. Name the phenomenon of formation of seed without fertilization in angiosperms. Give an example of a plant which exhibits this phenomenon.
Answer: The special mechanism to produce seeds without fertilisation is called apomixis. Examples of plants exhibiting this include some species of Asteraceae and grasses.
25. Define polyembryony. Mention the plant which exhibits polyembryony.
Answer: Polyembryony is the occurrence of more than one embryo in a single seed. Plants exhibiting this phenomenon include many Citrus and Mango varieties.
26. How are parthenocarpic fruits produced by some plants and apomictic seeds by some others?
Answer: Parthenocarpic fruits are produced when the ovary develops into a seedless fruit without fertilisation occurring (this can also be artificially induced through growth hormones). Apomictic seeds are produced when a diploid egg cell is formed without reduction division and develops into an embryo without fertilisation, or when nucellar cells surrounding the embryo sac actively divide and develop into multiple embryos.
27. In the T.S. of an anther given below, identify “a” and “b” and mention their function.
Answer:
a: It is the Sporogenous tissue, and its function is to undergo meiotic divisions to form microspore tetrads.
b : It is the Tapetum, and its function is to nourish the developing pollen grains.
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