Models for the Rheology and Statistical Strength of Uniformly Stressed Vegetative Tissue

Abstract

ABSTRACT THE first part of this paper is a literature review of the important features of plant vegetative tissue that relate to its rheological and strength properties. Several internal mechanisms by which an applied load is resisted are described, and two internal mechanisms of failure initiation are discussed. Second, a simple elastic me-chanics model is developed for the cellular structure under a uniform load, and results are obtained which give a qualitative relation between applied external stresses and strains, cell wall stresses, and cell turgidity. Third, a description of the statistical failure process in uniformly stressed samples is postulated, and a probabil-ity model is developed for the initiation of this failure process. The theoretical development leads to the use of the Weibull distribution to describe the yield strength of tissues exhibiting a sharp reduction in stress at yielding. Experimental data for apple and potato samples show the Weibull model to be adequate statistically. The Weibull model is a useful tool for predicting the amount of damaged tissue under a known applied stress.