67. Which one of the following is NOT a characteristic feature of skotomorphogenicdevelopment?
(a) Apical hook
(b) Closed cotyledons
(c) Expanded leaves
(d) Long hypocotyls

What Is Skotomorphogenic Development in Plants?

Skotomorphogenesis is the growth and developmental pattern of seedlings in darkness, such as those germinating underground. This form of development helps the seedling efficiently reach light and then switch to photomorphogenesis.

Let’s analyze the key traits.

Correct Answer:

(c) Expanded leaves – This is NOT a characteristic of skotomorphogenesis.

Defining Characteristics of Skotomorphogenesis

When a seedling grows in the absence of light, it exhibits the following features:

• (a) Apical hook: A protective curvature at the shoot tip to shield the delicate apical meristem as it pushes through the soil.

• (b) Closed cotyledons: Cotyledons remain closed and unexpanded to reduce energy expenditure.

• (d) Long hypocotyls: The stem below the cotyledons elongates rapidly to help the seedling reach the soil surface and light.

These are all adaptive responses to darkness that increase the plant’s chance of survival upon emergence.

Why Expanded Leaves Don’t Fit

Expanded leaves are a hallmark of photomorphogenesis, the development that takes place in light. In darkness:

• Leaf expansion is suppressed.

• Energy is redirected toward vertical growth.

• Chloroplast development is halted (etioplasts form instead).

Thus, expanded leaves are not part of skotomorphogenic development.

Conclusion

Skotomorphogenic development is tailored for seedlings growing in the dark. Its features—such as apical hook, closed cotyledons, and elongated hypocotyls—maximize the chance of reaching light quickly. Expanded leaves, by contrast, are associated with light-driven development and are not observed in this process.