What is water potential ?

Explanation

### Step-by-Step Solution:

1. **Definition of Water Potential**:
Water potential is defined as the energy required per quantity of water to transport an infinite quantity of water. It is a measure of the potential energy of water in a system compared to pure water, which is assigned a water potential of zero.

**Hint**: Remember that water potential is related to energy and is measured in pressure units (usually megapascals, MPa).

2. **Direction of Water Flow**:
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