115. Fusicoccin promotes cotyledon growth by promoting:
(1) cell division
(2)cell wall biosynthesis
(3) tonoplast acidification
(4) cell wall acidification

Detailed Explanation:

Question:
Fusicoccin promotes cotyledon growth by promoting:

✅ Correct Answer: (4) Cell wall acidification

What is Fusicoccin?

Fusicoccin is a phytotoxin produced by the fungus Fusicoccum amygdali. It has been shown to have various physiological effects on plant growth and development, particularly in promoting the growth of cotyledons.

How Does Fusicoccin Promote Cotyledon Growth?

Fusicoccin promotes cotyledon growth primarily by cell wall acidification, which enhances the expansion of plant cells. It activates H+-ATPase pumps on the cell membrane, which pump protons (H+) into the cell wall, lowering the pH and causing the cell wall to loosen and expand. This process makes it easier for the cells to increase in size and contribute to the overall growth of the cotyledon.

Here’s how this mechanism works:

1. Cell Wall Acidification: Fusicoccin activates the H+-ATPase pump, which increases the concentration of hydrogen ions (H+) in the cell wall.

2. Cell Expansion: The acidification of the cell wall makes it more flexible, allowing cells to expand more easily, leading to growth in the cotyledons.

3. Increased Growth: This process facilitates the enlargement of cells, which in turn leads to the growth of cotyledons in young plants.

Why Other Options Are Incorrect:

• (1) Cell division: Fusicoccin does not directly promote cell division but instead influences cell expansion by acidifying the cell wall.

• (2) Cell wall biosynthesis: While fusicoccin affects the cell wall, it specifically promotes acidification and loosening, not biosynthesis of the cell wall components.

• (3) Tonoplast acidification: Fusicoccin primarily affects the cell wall and plasma membrane, not the tonoplast (the membrane surrounding vacuoles). It does not significantly impact vacuole acidification in this context.

Conclusion:

Fusicoccin promotes cotyledon growth by cell wall acidification, which allows cells to expand and contributes to the overall development of the cotyledons in young plants.

✅ Correct Answer: (4) Cell wall acidification