Leaf fall occurs when

Options

A. Auxin content is more in lamina than in the stem
B. Auxin content is low in the lamina as compared to stem
C. Abscisic acid is formed
D. Morphactins are produced.

Answer

**Step-by-Step Solution:**

1. **Understanding Leaf Fall (Abscission):**
- Leaf fall, also known as abscission, is a natural process where leaves detach from the plant. This process is influenced by various factors, including plant hormones.

2. **Identifying Key Hormones:**
- The two main hormones involved in the process of leaf fall are auxin and abscisic acid (ABA).
- Auxin is a plant growth promoter found in young leaves and is produced in the petiole (the stalk that attaches the leaf to the stem).
- Abscisic acid is associated with stress responses and is produced in higher concentrations in dying plant tissues.

3. **Analyzing the Options:**
- **Option 1:** "Oxygen content is more in lamina than in the stem."
- This option is incorrect because oxygen levels do not directly influence leaf fall.

- **Option 2:** "Oxygen content is low in the laminas compared to stem."
- This option is also incorrect for the same reason as above; oxygen content is not the primary factor in leaf fall.

- **Option 3:** "Abscisic acid is formed."
- This option is misleading. While abscisic acid is involved, simply forming it does not lead to leaf fall; rather, it is the concentration of abscisic acid that matters.

- **Option 4:** "More pectins are produced."
- This option is incorrect because pectins are associated with cell wall structure and growth, not with leaf abscission.

4. **Correct Answer:**
- The correct answer is that leaf fall occurs when **auxin content is low in the lamina compared to the stem**. When the concentration of auxin decreases, it can lead to the death of the leaf tissue, prompting the leaf to fall.

**Final Answer:**
Leaf fall occurs when auxin content is low in the lamina compared to the stem.

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