Questions & explanations
1. In which type of endosperm development do free nuclear divisions occur first, followed by cell wall formation?
- A) Nuclear endosperm
- B) Cellular endosperm
- C) Helobial endosperm
- D) Ruminate endosperm
Answer: A) Nuclear endosperm
In nuclear endosperm, the primary endosperm nucleus undergoes repeated free nuclear divisions without cell wall formation, resulting in a multinucleate cytoplasm. Cell walls form later. Cellular endosperm involves immediate cell wall formation, while helobial is intermediate.
2. What is the significance of double fertilization in angiosperms?
- It ensures that endosperm develops only if fertilization occurs
- It produces a diploid zygote
- It prevents polyembryony
- It leads to the formation of a haploid endosperm
Answer: It ensures that endosperm develops only if fertilization occurs
Double fertilization links endosperm development to fertilization, preventing wasteful nutrient investment. The endosperm is triploid, not haploid, and the zygote is diploid, but the key significance is the coordination of endosperm formation with fertilization.
3. Dichogamy as an outbreeding device refers to:
- Male and female flowers on different plants
- Anthers and stigmas maturing at different times
- Physical separation of anthers and stigma in the same flower
- Inability of pollen to germinate on the stigma of the same flower
Answer: Anthers and stigmas maturing at different times
Dichogamy prevents self-pollination by ensuring that anthers and stigmas mature at different times. Unisexuality refers to separate male and female flowers, herkogamy is physical separation, and self-incompatibility is genetic inability.
4. Which of the following layers of a pollen grain is made of sporopollenin, one of the most resistant organic substances?
- A) Intine
- B) Exine
- C) Germ pore
- D) Tapetum
Answer: B) Exine
The exine is the outer layer of the pollen grain wall and is composed of sporopollenin, which is highly resistant to decay and protects the pollen during transport. The intine is the inner layer made of cellulose and pectin.
5. Megagametogenesis refers to the development of which structure?
- Male gametophyte
- Female gametophyte
- Embryo
- Endosperm
Answer: Female gametophyte
Megagametogenesis is the process of development of the female gametophyte (embryo sac) from the functional megaspore. The male gametophyte develops from microspores, embryo from zygote, and endosperm from triploid nucleus.
6. Which of the following is an example of a non-endospermic (exalbuminous) seed?
- A) Castor
- B) Maize
- C) Pea
- D) Coconut
Answer: C) Pea
Non-endospermic seeds, like pea, have cotyledons that absorb the endosperm during development, so the mature seed lacks endosperm. Castor, maize, and coconut are endospermic (albuminous) seeds with persistent endosperm.
7. During seed development, the integuments of the ovule develop into the:
- A) Endosperm
- B) Seed coat
- C) Pericarp
- D) Embryo
Answer: B) Seed coat
The integuments of the ovule undergo changes to form the seed coat, which protects the embryo. The endosperm develops from the primary endosperm nucleus, the pericarp from the ovary wall, and the embryo from the zygote.
8. The tapetum in the microsporangium is primarily responsible for:
- A) Providing mechanical support
- B) Nourishing developing pollen grains
- C) Protecting the anther from desiccation
- D) Facilitating dehiscence of the anther
Answer: B) Nourishing developing pollen grains
The tapetum is the innermost layer of the microsporangium wall and secretes nutrients and enzymes essential for the development and maturation of pollen grains. It also contributes to the formation of the pollen wall.
9. Which of the following conditions is most likely to reduce seed viability over time?
- A) Storage at low temperature and low humidity
- B) Storage at high temperature and high humidity
- C) Storage in airtight containers with desiccants
- D) Storage in liquid nitrogen
Answer: B) Storage at high temperature and high humidity
High temperature and high humidity accelerate metabolic activity and microbial growth, leading to rapid loss of seed viability. Low temperature, low humidity, desiccants, and cryopreservation help maintain viability.
10. Which part of the ovule connects it to the placenta?
- Hilum
- Funicle
- Chalaza
- Micropyle
Answer: Funicle
The funicle is the stalk that attaches the ovule to the placenta. The hilum is the point of attachment of the funicle to the ovule body, the chalaza is the basal part, and the micropyle is the opening at the apex.
11. In a monocot embryo, the structure that protects the radicle is called:
- A) Coleoptile
- B) Coleorhiza
- C) Scutellum
- D) Epicotyl
Answer: B) Coleorhiza
The coleorhiza is a sheath that covers and protects the radicle in monocot embryos. The coleoptile protects the plumule, the scutellum is the cotyledon, and the epicotyl is the part above the cotyledon attachment.
12. In which type of ovule is the micropyle, chalaza, and funicle in a straight line?
- Anatropous
- Orthotropous
- Campylotropous
- Amphitropous
Answer: Orthotropous
In orthotropous (atropous) ovules, the micropyle, chalaza, and funicle lie in a straight line. In anatropous, the ovule is inverted; in campylotropous, it is curved; in amphitropous, it is partially inverted.