Q62. The observations of seed germination of various genotypes under different light conditions are given, where ✓ and X indicate germination and the lack of it, respectively.

Based on these observations, which of the following option(s) are CORRECT?

Option (C) is the correct answer: CRY1, PHY A, and PHY B proteins are required for blue, red, and far-red light perception, respectively.

Detailed Analysis of the Table
Wild-type seeds germinate under blue (✓), red (✓), and far-red (✓) light but fail in dark (X), showing light dependence mediated by specific photoreceptors. The cry1 mutant lacks response to blue (X) but responds to red (✓) and far-red (✓), indicating CRY1 specifically handles blue light. PhyA mutant responds to blue (✓) and red (✓) but not far-red (X), confirming PHY A for far-red. PhyB mutant shows response to blue (✓) but lacks red (X) and far-red (✓? partial via others), aligning PHY B with red. Vp1 mutant germinates across all lights (✓ including dark), suggesting VP1 enforces light requirement.​

Option Breakdown

A: All three light qualities—blue, red, and far-red—are required for seed germination.
Incorrect. Wild-type germinates under any single light (blue, red, or far-red), not needing all simultaneously.​

B: Any one of the three light qualities—blue, red, and far-red—is sufficient to induce seed germination.
Partially true for wild-type but fails for mutants; cry1 ignores blue, phyA ignores far-red, showing specificity, not sufficiency alone.​

C: The CRY1, PHY A, and PHY B proteins are required for blue, red, and far-red light perception.
Correct. Table phenotypes match: cry1 blocks blue, phyA blocks far-red, phyB blocks red; far-red via phyA, red via phyB.​

D: The VP1 protein is unlikely to be involved in light perception.
True but not best; VP1 (ABI3 ortholog) controls dormancy/light sensitivity downstream, as vp1 germinates in dark, but question focuses on perception.​

In seed germination light conditions for Arabidopsis mutants, photoreceptors like CRY1, PHY A, and PHY B dictate responses to blue, far-red, and red light, vital for CSIR NET life sciences prep. This table-based analysis reveals how mutants dissect light signaling pathways in photomorphogenesis.​

Photoreceptor Roles

CRY1 mediates blue light germination; its mutant fails blue (X) but responds to red/far-red. PHY A handles far-red via very low/ high irradiance responses; phyA mutant blocks far-red. PHY B drives red light low-fluence response; phyB mutant insensitive to red.​

Mutant Phenotypes

• Wild-type: Requires light (dark X), any quality suffices.

• cry1: Blue-specific defect.

• phyA: Far-red defect.

• phyB: Red defect.

• vp1: Light-independent (dark ✓).​

Exam Relevance

For CSIR NET, recognize C as correct: specific photoreceptors for each light quality. VP1 acts post-perception in ABA dormancy control.​