# DBT JRF 2022 — Question 74

Exam: DBT JRF 2022 · Section: B · Topic: Plant Biology › Photoreceptors - Cryptochromes · Difficulty: Medium

## Question

Cryptochromes control photomorphogenesis in response to:

## Options

- **A.** Red light
- **B.** Far-red light
- **C.** Infra-red light
- **D.** Blue and UV-A light

## Answer

Option D

## Explanation

Cryptochromes: photoreceptors and their light absorption: Cryptochromes are plant (and animal) photoreceptors that absorb: • Blue light (400–500 nm), particularly around 450 nm • UV-A light (~315–400 nm) Plant cryptochrome functions: • CRY1 and CRY2 in Arabidopsis: - Inhibit hypocotyl elongation in blue light (photomorphogenesis) - Promote flowering (circadian clock interaction) - Regulate anthocyanin accumulation - Entrain circadian rhythms Distinction from other photoreceptors: • Phytochromes: absorb red (660 nm) and far-red (730 nm) light. • Phototropins: absorb blue/UV-A, regulate phototropism and stomatal opening. • UVR8: absorbs UV-B light. Cryptochromes contain FAD (flavin adenine dinucleotide) as a chromophore. Answer: Cryptochromes absorb blue light (400–500 nm) and UV-A; regulate photomorphogenesis and circadian rhythms.

Source: https://mypyqbuddy.com/questions/cryptochromes-control-photomorphogenesis-in-response-to-6a104cd5920734408bc0c759