GED Science TestLife ScienceMedium
A farmer is cultivating a new variety of corn. He notices that when he exposes the plants to longer periods of darkness, they tend to flower earlier. This observation suggests that the flowering of this corn variety is regulated by:
- AGravitropism
- BThigmotropism
- CThermotropism
- DPhotoperiodism
Show answer & explanationAnswer & explanation
Correct answer: D. Photoperiodism
Photoperiodism is the physiological response of an organism to the length of day or night. The observation that longer periods of darkness (i.e., shorter days) affect flowering time directly indicates a photoperiodic response, common in many plants.
Why the other options are wrong
- A. Gravitropism is growth response to gravity, not light/dark cycles.
- B. Thigmotropism is growth response to touch or mechanical stimulation, not light/dark cycles.
- C. Thermotropism is growth response to temperature, not light/dark cycles.
Photoperiodism
Photoperiodism is the physiological response of plants and animals to the length of day or night. In plants, it often regulates flowering, dormancy, and leaf drop.
- Response to relative lengths of light and dark periods.
- Crucial for timing biological events like flowering.
- Plants are classified as short-day, long-day, or day-neutral.
- The length of the uninterrupted dark period is often critical.
Memory trick: Photo-period for plants, light for life's patterns!