The translocation of organic solutes in sieve tube members is supported by
(a) Mass flow involving a carrier and ATP
(b) Cytoplasmic streaming
(c) Root pressure and transpiration pull
(d) P-protein

Options

A. Mass flow involving a carrier and ATP
B. Cytoplasmic streaming
C. Root pressure and transpiration pull
D. P-protein

Answer

To solve the question regarding the translocation of organic solutes in sieve tube members, we need to analyze each option provided and determine which one correctly supports the process.

### Step-by-Step Solution:

1. **Understanding Translocation**: Translocation is the movement of organic solutes (like sugars) from the source (where they are produced, usually the leaves) to the sink (where they are used or stored, such as roots or fruits).

2. **Evaluating Option A**:
- **Mass flow involving a carrier and ATP**: This option refers to the mass flow hypothesis, which states that organic solutes are transported through the phloem (sieve tube members) via a pressure gradient. This process requires metabolic energy, primarily in the form of ATP, to facilitate the movement of solutes from source to sink.
- **Conclusion**: This option is a strong candidate as it directly relates to the mechanism of translocation.

3. **Evaluating Option B**:
- **Cytoplasmic streaming**: This refers to the movement of cytoplasm within cells, which can help distribute materials within individual cells but does not explain the translocation of solutes through the sieve tubes.
- **Conclusion**: This option is not correct for the translocation of organic solutes in sieve tube members.

4. **Evaluating Option C**:
- **Root pressure and transpiration pull**: These processes are related to the movement of water and minerals through the xylem, not the transport of organic solutes in the phloem.
- **Conclusion**: This option is also not correct for the translocation of organic solutes.

5. **Evaluating Option D**:
- **P-protein**: This is a type of protein found in the phloem that is involved in sealing damaged sieve tubes but does not facilitate the translocation of organic solutes.
- **Conclusion**: This option is not correct for the translocation of organic solutes.

6. **Final Conclusion**: After evaluating all the options, the only correct answer is **(a) Mass flow involving a carrier and ATP**. This aligns with the mass flow hypothesis, which accurately describes the translocation of organic solutes in sieve tube members.

### Final Answer:
**(a) Mass flow involving a carrier and ATP**