New experiences with writing toxins

Abstract

Wilting agents act chemically and physically on the host plant. The chemically active wilting toxins belong to various groups of substances and no relationship can be seen either to the systematic position of their causal agents or of their hosts. As physically active wilting agents, only glucosans are known. Every causal agent of a wilting disease probably forms several wilting toxins; and conversely a certain wilting toxin is only rarely characteristic for a certain causal agent, while as a rule it can be produced by several related causal agents. The action range of wilting toxins is wider than the host range of the causal agents. The wilting toxins can therefore act upon plants which the causal agents which formed them are unable to attack. Differing nutrition merely shifts the resistance of the host plant to the causal agent and not its resistance to the toxin. The chemically active wilting toxins damage their host by destroying the osmotic properties of the plasma boundary layer, or by inactivating the sulfhydryl groups, or by inactivating certain growing substances. They possess a specificity for certain tissue of the host plant. Their action threshold is generally at about 15 mg fresh weight.