Biophysical Equations and Pressure Probe Experiments to Determine Altered Growth Processes after Changes in Environment, Development, and Mutations.

Joseph K E Ortega

doi:10.3390/plants11030302

Abstract

Expansive growth is a culmination of many biological processes. It is fundamental to volume growth, development, morphogenesis, sensory responses, and environmental responses of plants, fungi, and algae. Expansive growth of walled cells and plant tissue can be accurately described by a set of three global biophysical equations that model the biophysical processes of water uptake, wall deformation, and turgor pressure. Importantly, these biophysical equations have been validated with the results of pressure probe experiments. Here, a systematic method (scheme) is presented that iterates between analyses with the biophysical equations and experiments conducted with the pressure probe. This iterative scheme is used to determine altered growth processes for four cases; two after changes in the environment, one after a change in development, and another after changes by mutation. It is shown that this iterative scheme can identify which biophysical processes are changed, the magnitude of the changes, and their contribution to the change in expansive growth rate. Dimensionless numbers are employed to determine the magnitude of the changes in the biophysical processes. The biological meaning and implication of the biophysical variables in the biophysical equations are discussed. Further, additional sets of global biophysical equations are presented and discussed.

Highlights

Volumetric growth rates of plants and fungi depend on the expansive growth rates of individual plant and fungal cells
Dimensional analysis was conducted on Equations (1)–(3) and dimensionless Π parameters were identified that could be used to determine the magnitude of each term in the dimensionless biophysical Equations (5)–(7)
Analyses using the biophysical equations and pressure probe experiments show that the elongation growth rate is terminated after the decrease in temperature from 23 to 8 ◦C because the turgor pressure decreases to the magnitude of the critical turgor pressure and eliminates the driving force for expansive growth

Summary

Introduction

Volumetric growth rates of plants and fungi depend on the expansive growth rates of individual plant and fungal cells (cells with walls). Biophysical equations describing the wall deformation rate (plastic and elastic deformation rates), net water uptake rate (water uptake rate minus transpiration rate), and rate of change of turgor pressure (that couples the biophysical processes of water uptake and wall deformation) have been previously derived and validated with experimental results from pressure probe experiments [1,2,3]. These biophysical equations have been referred to as the ‘augmented growth equations’.

Methods

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Discussion

Conclusion