Food is transported by the vascular tissue phloem from a source to a sink. The source and sink may be reversed depending on the

Options

A. season
B. plant's needs
C. geographical distribution
D. both (1) and (2)

Answer

To solve the question regarding the transport of food by the vascular tissue phloem from a source to a sink, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Phloem Function**:
- Phloem is the vascular tissue responsible for transporting food (mainly in the form of sucrose) from the source (where it is produced) to the sink (where it is utilized or stored).

**Hint**: Remember that phloem is primarily involved in the transport of organic nutrients.

2. **Identifying Source and Sink**:
- The source is typically the green parts of the plant (like leaves) where photosynthesis occurs, producing food.
- The sink includes non-green parts (like fruits, seeds, or roots) where the food is consumed or stored.

**Hint**: Think about where photosynthesis occurs and where the plant uses or stores energy.

3. **Reversal of Source and Sink**:
- The roles of source and sink can change based on certain factors.
- For example, during the growing season, leaves are the source, but in spring, stored sugars in roots can be mobilized to support new growth, making roots the source and buds the sink.

**Hint**: Consider how seasonal changes affect plant growth and nutrient allocation.

4. **Factors Affecting Source and Sink Dynamics**:
- The source and sink can be reversed depending on:
- **Season**: Seasonal changes can influence which parts of the plant are actively producing or consuming food.
- **Plant Needs**: The physiological needs of the plant at different growth stages can also dictate which parts act as source or sink.

**Hint**: Reflect on how plants adapt to their environment and changing conditions.

5. **Conclusion**:
- Given the options provided in the question, the correct answer is that the source and sink may be reversed depending on both season and plant needs.

**Hint**: Look for options that encompass multiple factors affecting plant physiology.

### Final Answer:
The source and sink may be reversed depending on both season and plant needs (Option 4: Both 1 and 2).