What is protophloem?

Explanation

### Step-by-Step Solution:

1. **Definition of Protophloem**: Protophloem is the first form of phloem that develops in plants. It is part of the vascular tissue responsible for the transport of nutrients, particularly sugars, throughout the plant.

2. **Origin**: Protophloem develops from a type of meristematic tissue called procambium. The procambium is responsible for the formation of primary vascular tissues in plants.

3. **Cell Structure**: The cells that make up protophloem are typically narrow and have thin walls. This structure is adapted for the efficient transport of substances.

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