Answer :
Answer:
Explanation:
Sweet potato plants, like other vascular plants, transport carbohydrates synthesized in the leaves to the roots through a process known as translocation, which occurs in the phloem vessels. Here is a step-by-step explanation of how this process works:
1. **Photosynthesis in the Leaves**: Carbohydrates, primarily in the form of sucrose, are produced in the leaves during photosynthesis. These carbohydrates are referred to as "photoassimilates".
2. **Loading of Carbohydrates into the Phloem**: The sucrose is actively transported from the mesophyll cells of the leaves into the phloem sieve-tube elements. This process is facilitated by transporter proteins located in the cell membranes. This loading can be either symplastic (through plasmodesmata) or apoplastic (requiring active transport across cell membranes).
3. **Phloem Transport (Translocation)**: Once inside the phloem sieve tubes, the sucrose is transported through the plant via a mechanism known as pressure-flow hypothesis (or mass flow hypothesis). In this model:
- **Source Regions (Leaves)**: The high concentration of sucrose in the phloem creates a low water potential, causing water to enter the phloem from adjacent xylem vessels by osmosis.
- **Pressure Gradient**: The influx of water generates a positive pressure that pushes the sucrose solution (phloem sap) along the sieve tubes towards areas of lower pressure (sinks), such as roots, tubers, or growing tissues.
4. **Unloading of Carbohydrates at the Sink**: When the phloem sap reaches the roots (the sink), sucrose is actively or passively transported out of the sieve tubes into the root cells. Here, sucrose can be used for growth, storage, or converted into other forms of carbohydrates like starch.
5. **Recycling of Water**: The water that carried the sucrose to the roots exits the phloem and is either used by root cells or re-enters the xylem to be transported back up to the leaves, completing the cycle.
This process ensures that the sweet potato roots receive the necessary carbohydrates for their growth and development, supporting the formation of storage organs like the sweet potato tubers.
