During phloem loading, sugar is moved in the form of sucrose from mesophyll cell to phloem by –

Options

A. Passive transport
B. Active transport
C. Facilitated diffusion
D. Osmosis

Answer

### Step-by-Step Solution:

1. **Understanding Phloem**:
- Phloem is a type of vascular tissue in plants responsible for the transport of nutrients, particularly sugars (in the form of sucrose), from the leaves (where they are produced) to other parts of the plant.

2. **Components of Phloem**:
- Phloem is made up of specialized cells, including sieve tubes and companion cells. Sieve tubes are the main conduits for sugar transport, while companion cells assist in the loading and unloading of sugars.

3. **Phloem Loading Process**:
- During phloem loading, sucrose is moved from mesophyll cells (where photosynthesis occurs) into the phloem. This process primarily involves the companion cells that are closely associated with the sieve tubes.

4. **Mechanism of Transport**:
- The transport of sucrose from the mesophyll cells to the phloem occurs through a mechanism called **passive transport**, specifically **simple diffusion**. This process relies on the concentration gradient, where sucrose concentration is higher in the companion cells compared to the sieve tubes.

5. **Concentration Gradient**:
- The concentration gradient drives the movement of sucrose from an area of higher concentration (companion cells) to an area of lower concentration (sieve tubes). This movement does not require energy, which is characteristic of passive transport.

6. **Evaluating Options**:
- The options provided include:
- A) Passive transport
- B) Active transport
- C) Facilitated diffusion
- D) Osmosis
- Since the movement of sucrose occurs through simple diffusion without the involvement of energy, the correct answer is **A) Passive transport**.

### Final Answer:
During phloem loading, sugar is moved in the form of sucrose from mesophyll cells to phloem by **passive transport** (simple diffusion).

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