Read Phytochrome and Germination
A focused NSEB read for the phytochrome and germination pattern. Learn the linked concept, then apply it in the source questions.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Phytochrome and Germination
Final light pulse determines Pfr state. Red and far-red light have photoreversible effects mediated by phytochrome. Alternating R/FR treatments show that the last light exposure largely determines whether seeds germinate: red promotes, far-red reverses. Therefore A and D are correct; the exact 1:4 duration ratio is not the governing principle.
Rank light colours by phytochrome response
For phytochrome-controlled germination, red light is most effective because it forms Pfr. Blue can support a smaller response, while yellow and green are weak because they are poorly absorbed in this system. Rank the measured germination rather than assuming every visible wavelength has equal effect: Red > Blue > Yellow > Green. Choose D.
Separate Pfr responses from darkness responses
The active Pfr state promotes photomorphogenesis: cotyledons open and green, seedlings respond to low red:far-red ratios through shade avoidance, and flowering can be photoperiodically regulated. Etiolation is the dark-state outcome, while hydrotropism and geotropism respond mainly to water and gravity. Select I, II and VI. Choose C.
OlympIQ exam lens
- ✓Final light pulse determines Pfr state
- ✓Red light most strongly promotes phytochrome-mediated germination in the source comparison.
- ✓Pfr regulates de-etiolation, shade avoidance and photoperiodic flowering.
Read the conditions in the stem carefully and use the stated model, labels, or assumptions before choosing an answer.
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