Sieve tube is -

Options

A. Multicellular, vessel like structure
B. Provided with porous septa
C. The main conducting element for translocation of food
D. All of the above

Answer

**Step-by-Step Solution:**

1. **Definition of Sieve Tube:**
- A sieve tube is a type of plant cell that is part of the phloem tissue responsible for the transport of nutrients, particularly sugars, throughout the plant.

2. **Structure of Sieve Tube:**
- Sieve tubes are composed of elongated cells known as sieve tube elements. These cells are arranged end to end to form long tubes.

3. **Characteristics of Sieve Tube Elements:**
- Sieve tube elements are unique in that they are enucleated (lack a nucleus) at maturity. This allows for more efficient transport of substances.
- They have sieve plates at their ends, which are porous structures that facilitate the flow of sap between adjacent sieve tube elements.

4. **Function of Sieve Tube:**
- The primary function of sieve tubes is the translocation of organic nutrients, primarily sucrose, from the leaves (where they are produced during photosynthesis) to other parts of the plant, such as roots and fruits.

5. **Companion Cells:**
- Each sieve tube element is associated with companion cells, which are nucleated cells that help regulate the function of the sieve tube elements. Companion cells assist in loading and unloading the sugars into the sieve tubes.

6. **Conclusion:**
- In summary, the sieve tube is a crucial component of the phloem, functioning as the main conducting element for the translocation of food in plants.

**Final Answer:**
Sieve tube is the main conducting element for the translocation of food in plants, composed of sieve tube elements that are enucleated and associated with companion cells.

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