# DBT JRF 2022 — Question 71

Exam: DBT JRF 2022 · Section: B · Topic: Plant Biology › Photomorphogenesis & Skotomorphogenesis · Difficulty: Medium

## Question

Skotomorphogenesis is characterized by:

## Options

- **A.** Small and closed cotyledons and elongated hypocotyl
- **B.** Fully open cotyledons
- **C.** Robust foliage and root growth
- **D.** Early flowering resulting from short-day conditions

## Answer

Option A

## Explanation

Skotomorphogenesis (dark-grown seedling development): Skotomorphogenesis = developmental program activated in darkness (from Greek 'skotos' = dark): • Characteristics of etiolated (dark-grown) seedlings: - Elongated hypocotyl (to push through soil) - Small, unexpanded cotyledons - Apical hook (protects the shoot apical meristem) - Pale yellow (no chlorophyll synthesis) - Closed apical bud Regulation: • COP1 (constitutively photomorphogenic 1) is active in dark → ubiquitinates transcription factors (HY5) promoting photomorphogenesis → degradation → skotomorphogenesis proceeds. • Phytochromes in the Pr (inactive) form in dark. Distinction: • Photomorphogenesis: light-induced development (chlorophyll synthesis, leaf expansion, etc.). • Skotomorphogenesis is NOT the same as photoperiodism (response to day length for flowering). Answer: Skotomorphogenesis = dark-grown seedling phenotype (elongated hypocotyl, apical hook, etiolation).

Source: https://mypyqbuddy.com/questions/skotomorphogenesis-is-characterized-by-6a104cd5920734408bc0c756