UPSC Prelims 2002 Q100: Science & Technology – Biology
In a bisexual flower, if androecium and gynaecium mature at different times, the
phenomenon is known as
- (a) Dichogamy
- (b) Herkogamy
- (c) Heterogamy
- (d) Monogamy
Answer: (a) Dichogamy
Explanation
Androecium and gynaecium maturing at different times
| Term | Meaning |
|---|---|
| Dichogamy | Stamens and carpels mature at different times, which prevents self-pollination |
| Herkogamy | A physical barrier between anther and stigma |
| Heterogamy | Different kinds of gametes or flowers; not about timing |
| Monogamy | A mating system, not a floral term |
In a bisexual flower, when the androecium and gynaecium mature at different times, the phenomenon is called dichogamy. It is a device to avoid self-pollination, as in protandry (anthers first) and protogyny (stigma first).
Answer: (a) Dichogamy.
Why each option is right or wrong
- (a) CORRECT. Dichogamy is the difference in maturation time.
- (b) Incorrect. Herkogamy is a physical barrier, not a timing difference.
- (c) Incorrect. Heterogamy does not refer to maturation time.
- (d) Incorrect. Monogamy is not a floral term.
Key point
Self-pollination barriers: dichogamy (timing), herkogamy (position), self-incompatibility, unisexual flowers.
Remember
Dichogamy = stamens and carpels ripen at different times.
Common mistakes
- Choosing herkogamy, which is about position and not time.
- Mixing the terms with mating systems in animals.
- Not knowing protandry and protogyny.
Exam tip
Dicho = two; the two organs mature at two different times.
Sources
- NCERT Class XII Biology — Sexual Reproduction in Flowering Plants
- P. Maheshwari — An Introduction to the Embryology of Angiosperms (McGraw-Hill, 1950)