A Model for Resin Flow

Abstract

Resins are plant exudates of economic importance composed of volatile and nonvolatile compounds, sometimes including gum, that are used by plants mostly as defense against invading pathogens. They are synthesized by epithelial cells surrounding intercellular spaces, called ducts, where they are stored under pressure. Despite the differences in the structure and distribution of resin ducts between gymnosperms and angiosperms, as well as in the mechanisms of resin loading, there are similarities in the importance of resin in both groups of plants. This chapter presents a model that applies the unsteady Stokes equation and describes resin flow in plants, considering resin viscosity, the structure of resin ducts, and a pressure-driven granulocrinous loading of resin through the duct wall. Resin flow is shown to increase towards the duct open end. Both flow and pressure within the duct depend on the loading of resin and on the duct specific resistance, which depends on the duct geometry, viscosity, and duct wall permeability to resin. The dynamics of flow within resin ducts seems physiologically advantageous for the defense role commonly attributed to resin and agrees with previous measurements and observations. Understanding how resin flow is affected by these physiological and morphological parameters might be useful not only to better understand the physiological role of resin but also improve and develop more efficient and sustainable tapping methods.