A mature sieve element possesses a peripheral cytoplasm and a large (A)____ but lacks a (B)_____

Answer

To answer the question regarding the characteristics of a mature sieve element, we can break it down step by step:

### Step-by-Step Solution:

1. **Understanding Sieve Elements**:
- Sieve elements are specialized cells found in the phloem tissue of flowering plants. Their primary function is to transport food (mainly sugars) throughout the plant.

2. **Identifying the Components of Sieve Elements**:
- A mature sieve element is characterized by having a **peripheral cytoplasm**. This means that the cytoplasm is located around the edges of the cell, rather than being distributed throughout the cell.

3. **Identifying the Vacuole**:
- In addition to the peripheral cytoplasm, a mature sieve element contains a **large central vacuole**. The vacuole is a storage organelle that holds various substances, including nutrients and waste products.

4. **Identifying the Missing Component**:
- Importantly, mature sieve elements **lack a nucleus**. This is a key feature that distinguishes them from many other cell types. Instead of having their own nucleus, sieve elements rely on the companion cells, which are adjacent to them, to regulate their functions through cytoplasmic connections known as plasmodesmata.

5. **Filling in the Blanks**:
- Based on the above understanding, we can fill in the blanks:
- (A) **Vacuole**
- (B) **Nucleus**

### Final Answer:
A mature sieve element possesses a peripheral cytoplasm and a large (A) **vacuole** but lacks a (B) **nucleus**.

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