146. Skotomorphogenesis is characterized by:
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

Skotomorphogenesis: A Plant’s Growth Strategy in Darkness

Plants exhibit two distinct developmental patterns depending on the presence or absence of light: photomorphogenesis and skotomorphogenesis. While photomorphogenesis occurs in light, skotomorphogenesis governs growth in darkness and is essential during seedling emergence when a plant pushes through the soil before reaching sunlight.

Key Characteristics of Skotomorphogenesis

Skotomorphogenesis is specifically adapted for growth in the dark, allowing the seedling to prioritize reaching light sources. It involves:

• Elongated hypocotyl (the stem-like structure below the seed leaves): This helps the seedling grow rapidly upward toward light.

• Apical hook formation: Protects the delicate shoot tip as it pushes through the soil.

• Small and closed cotyledons: Cotyledons (seed leaves) remain undeveloped and folded, conserving energy until light is available.

Correct Answer:

A. Small and closed cotyledons and elongated hypocotyl

This is the hallmark of skotomorphogenesis. Once the seedling breaks the surface and is exposed to light, it transitions to photomorphogenesis, characterized by open cotyledons and halted hypocotyl elongation.

Why Other Options Are Incorrect

• B. Fully open cotyledons – This is a feature of photomorphogenesis, not skotomorphogenesis.

• C. Robust foliage and root growth – Also associated with photomorphogenic development under light.

• D. Early flowering resulting from short-day conditions – Refers to photoperiodism, not a trait of dark-grown seedlings.

Conclusion

Skotomorphogenesis enables seedlings to maximize vertical growth in search of light by promoting hypocotyl elongation and suppressing energy-expensive leaf expansion. Recognizing this pattern is key to understanding early plant developmental responses in dark conditions.