In plants, most diffusible sugar from source to sink is

Options

A. Glucose
B. Sucrose
C. Starch
D. Fructose

Answer

To solve the question of which is the most diffusible sugar from source to sink in plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Plant Sugars**:
- Plants produce sugars primarily through photosynthesis. The main sugar produced is glucose, which is then converted into other forms for transport.

**Hint**: Remember that glucose is the primary product of photosynthesis.

2. **Conversion of Glucose**:
- After photosynthesis, glucose is often converted into sucrose, which is a disaccharide. Sucrose is the form in which sugars are commonly transported in plants.

**Hint**: Consider the forms of sugar that plants use for transport.

3. **Transport Mechanism**:
- Sugars are transported from the source (where they are produced) to the sink (where they are used or stored) through the phloem. This process involves living cells, specifically sieve tube elements and companion cells.

**Hint**: Think about the role of phloem in sugar transport.

4. **Active Transport**:
- The movement of sucrose into the phloem occurs through active transport, which requires energy. This is crucial for loading sugars into the sieve tubes.

**Hint**: Recall the difference between active and passive transport.

5. **Pressure Flow Hypothesis**:
- The most accepted mechanism for the translocation of sugars from source to sink is known as the Pressure Flow Hypothesis. This explains how sugars move through the phloem due to pressure differences created by the loading and unloading of sugars.

**Hint**: Familiarize yourself with the Pressure Flow Hypothesis and its significance in plant physiology.

6. **Conclusion**:
- While glucose is the initial product of photosynthesis, the most diffusible sugar that is transported from source to sink is sucrose. However, glucose is often considered in terms of its role in the overall process.

**Final Answer**: The most diffusible sugar from source to sink in plants is **sucrose**.

### Summary:
- The answer to the question is sucrose, as it is the primary sugar transported in plants from the source to the sink, despite glucose being the initial product of photosynthesis.