DPD in thermodynamic terminology is known as ................................

Explanation

**Step-by-Step Solution:**

1. **Understanding DPD**: DPD stands for Diffusion Pressure Deficit. It is a concept used in plant physiology to describe the difference between the diffusion pressure of water in the soil and that in the plant cells.

2. **Thermodynamic Terminology**: In thermodynamics, DPD is related to the concept of water potential. Water potential is a measure of the potential energy in water and is important for understanding the movement of water in plants.

3. **Water Potential**: Water potential (Ψ) is defined as the sum of solute potential (Ψs) and pressure potential (Ψp). Mathematically, it can be expressed as:
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