Identify the passive part of sugar transport process in plants

Options

A. Loading of sugars into companion cells
B. Mass flow through phloem
C. Unloading of sugars from phloem into storage cells
D. None

Answer

### Step-by-Step Solution:

1. **Understanding Sugar Transport in Plants**:
- Sugar transport in plants is known as translocation. It involves the movement of sugars (mainly sucrose) from the source (where they are produced, typically the leaves) to the sink (where they are utilized or stored).

2. **Identifying the Source and Sink**:
- The source is the part of the plant that produces sugar, primarily through photosynthesis in the leaves.
- The sink is the part of the plant that consumes or stores the sugar, such as roots, fruits, or other storage tissues.

3. **Processes Involved in Sugar Transport**:
- The transport of sugar involves several processes:
- **Loading of Sugar**: This is the process of moving sugar into the companion cells of the phloem. This process requires energy and is therefore active.
- **Mass Flow through Phloem**: Once the sugar is loaded into the phloem, it moves through the phloem tissue to the sink. This movement occurs due to a pressure gradient and does not require energy, making it a passive process.
- **Unloading of Sugar**: This is the process of moving sugar from the phloem into the storage cells. This process also requires energy and is therefore active.

4. **Identifying the Passive Part**:
- Among the processes mentioned, the **mass flow through the phloem** is the only passive part of sugar transport. It relies on the pressure differences created by the loading and unloading of sugar but does not require additional energy.

5. **Conclusion**:
- The passive part of the sugar transport process in plants is the **mass flow through phloem**.