Solute Efflux From the Host at Plant-Microorganism Interfaces

Abstract

The exchange of solutes between a plant and invading microorganism involves transport across both plant and microorganism membranes separated by a common apoplast. An empirical analysis of the interrelationship between these two membrane transport steps is undertaken with emphasis on transfer of reduced carbon from host to microorganism. The analysis leads to the conclusion that solute efflux from the plant partner has the potential to exert significant control over net transport of solutes from the plant to microorganism. The nature of solute efflux from the plant partner was evaluated for examples of pathological, mycorrhizal and Rhizobium associations. Estimates of solute efflux across the perceived interfacial membrane of the plant were greater than those of non-infected tissues. The principal factors contributing to the enhanced solute efflux in the presence of a microorganism were considered to be elevation of solute concentrations in the plant cytoplasm and modification of membrane transport. Possible modes of action by the invading microorganism on these factors are examined with particular attention being paid to the modification of membrane transport.