Which of the following statements is incorrect ?

Options

A. Companion cells help in maintaining pressure gradients in the sieve tubes .
B. Phloem parenchyma stores food material .
C. Bast fibres are generally absent in the primary phloem but re found in secondary phloem.
D. Phloem causes movement of organic substances and minerals only in the direction from leaves to stem and roots .

Answer

To solve the question "Which of the following statements is incorrect?", we will analyze each of the provided statements one by one.

### Step-by-Step Solution:

1. **Statement 1: Companion cells help in maintaining pressure gradient in the sieve tubes.**
- **Analysis:** This statement is correct. Companion cells are specialized parenchyma cells that assist in the function of sieve tubes, including maintaining the pressure gradient necessary for the transport of nutrients.

**Hint:** Remember the role of companion cells in phloem transport.

2. **Statement 2: Phloem parenchyma stores food material.**
- **Analysis:** This statement is also correct. Phloem parenchyma cells are involved in the storage of food materials, particularly carbohydrates.

**Hint:** Recall the functions of different types of parenchyma in plants.

3. **Statement 3: Vascular fibers are generally absent in primary phloem but are found in the secondary phloem.**
- **Analysis:** This statement is correct. Vascular fibers (or bast fibers) are indeed typically absent in primary phloem and are present in secondary phloem, providing structural support.

**Hint:** Think about the differences between primary and secondary growth in plants.

4. **Statement 4: Phloem causes movement of the organic substances and minerals only in the direction from the leaves to stem and root.**
- **Analysis:** This statement is incorrect. Phloem is responsible for transporting organic substances (mainly sugars) from the leaves to all parts of the plant, including storage organs, and can also transport substances in both upward and downward directions, not just from leaves to roots.

**Hint:** Consider the directionality of phloem transport and its role in the plant.

### Conclusion:
The incorrect statement among the options provided is **Statement 4**.

### Final Answer:
**Option 4** is the incorrect statement.