pH/$T$ duality - wall properties and time evolution of plant cells

Abstract

We examined the pH/$T$ (or $\mu$/$T$) duality of acidic pH and temperature ($T$) for the growth of grass shoots in order to determine the equation of state (EoS) for living plants. By considering non-meristematic growth as a dynamic series of 'state transitions' (STs) in the extending primary wall, we identified the critical (read: optimum) exponents for this phenomenon, which exhibit a singular behaviour at a critical temperature, critical pH and critical chemical potential ($\mu$) in the form of four power laws: $F(\tau)_\pi\propto|\tau|^{\beta-1}$, $F(\pi)_\tau\propto|\pi|^{1-\alpha}$, $G(\tau)_\mu\propto|\tau|^{-2-\alpha+2\beta}$ and $G(\mu)_\tau\propto|\mu|^{2-\alpha}$. The power-law exponents $\alpha$ and $\beta$ are numbers, which are independent of pH (or $\mu$) and $T$ that are known as critical exponents, while $\pi$ and $\tau$ represent a reduced pH and reduced temperature, respectively. Various 'scaling' predictions were obtained - a convexity relation $\alpha + \beta \ge 2$ for practical pH-based analysis and a $\beta \equiv 2$ identity in microscopic representation. In the presented scenario, the magnitude that is decisive is the chemical potential of H$^+$ ions (protons), enforcing subsequent STs and growth. The EoS span areas of the biological, physical, chemical and Earth sciences cross the borders with the language (adapted formalism) of phase transitions.