Abstract
Expansive plant growth during water deficit is common in temperate and extreme climates. Understanding how the turgor pressure, P, behaves during water deficit is essential for a better understanding of expansive growth rate, v. Here, validated biophysical equations together with dimensional analyses are used to simulate water deficit and determine the behavior of P and v. A dimensionless number, Π(pw), helps simplify the biophysical equations and interpret the results. The magnitude of Π(pw) increases as water deficit severity increases. Analyses reveal that both P and v decrease curvilinearly as Π(pw) increases. Simple mathematical relationships between P, v, and Π(pw), are derived, providing a clear and quantitative understanding of how P and v change as water deficits become more severe. Additionally, it is shown how the results of these analyses can be used to assess P and v of roots growing in water deficit.