Sample 1Medium
A diagram shows a longitudinal section of a pistil after compatible pollination. A pollen tube has grown down the style, entered the ovule through the micropyle and is entering one of the two synergids at the micropylar end of the embryo sac. That synergid carries a finger-like cellular thickening at its micropylar tip, labelled X. What is X and what does it do?
- A
X is the filiform apparatus, which guides the entry of the pollen tube into the synergid
- B
X is the hilum, which joins the ovule to the funicle
- C
X is the chalaza, which marks the base of the ovule
- D
X is the germ pore, through which the pollen tube emerges
Show the answer
The answer is A.The synergids bear special cellular thickenings at the micropylar tip called the filiform apparatus. It guides the pollen tube into the synergid, where the two male gametes are released.
- B.
The hilum is the junction of the ovule body with the funicle, not a part of the synergid.
- C.
The chalaza lies at the end opposite the micropyle and is not on the synergid.
- D.
Germ pores are on the pollen grain wall, not on the synergid.
NCERT: Class 12 Biology, Chapter 1, 1.2
Sample 2NEET level
Assertion (A): Cleistogamous flowers produce assured seed-set even in the absence of pollinators. Reason (R): In cleistogamous flowers, which do not open at all, the anthers and stigma lie close to each other.
- A
Both A and R are true and R is the correct explanation of A
- B
Both A and R are true but R is not the correct explanation of A
- C
A is true but R is false
- D
A is false but R is true
Show the answer
The answer is A.Cleistogamous flowers never open, and their anthers and stigma lie close together. When the anthers dehisce, pollen falls directly on the stigma and self-pollination occurs, so seed-set is assured without pollinators; R therefore explains A.
- B.
R is exactly the reason seed-set is assured: pollen reaches the stigma inside the closed flower.
- C.
R is true: cleistogamous flowers do not open and their anthers and stigma are close together.
- D.
A is true: cleistogamy assures seed-set without any pollinator.
NCERT: Class 12 Biology, Chapter 1 (Sexual Reproduction in Flowering Plants), Pollination