By looking at a plant externally can you tell whether a plant is `C_(3) or C_(4)` ? Why and how?

Explanation

To determine whether a plant is a C3 or C4 type by looking at it externally, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding C3 and C4 Plants**:
- C3 plants use the Calvin cycle for photosynthesis, where carbon dioxide is fixed into a three-carbon compound (3-phosphoglycerate).
- C4 plants have a different mechanism where carbon dioxide is initially fixed into a four-carbon compound (oxaloacetate) before entering the Calvin cycle.

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