Über das Problem der Welkekrankheiten bei Pflanzen

Summary Lycomarasmin is a plasma poison produced byFusarium lycopersici Sacc., the pathogen of tomato wilt. In a dilution of 10^–2 and 10^–3 mol it causes a pathological wilting of tomato plants and usually disturbs their water balance; in a dilution of 10^–4 mol it only disturbs the latter.In the present paper, we develop the theory that in sufficient concentration lycomariasmin damages or destroys thesemipermeability of the plasma boundary layer.In a dilution of 10^–2 and 10^–3 mol of lycomarasmin the semipermeability of the plasma membranes iscompletely destroyed. Thus on the one hand the conditions for osmotic pressure disappear and irreversible pathological wilting appears, and on the other hand cellular fluid passes into the transpiration current of the cell-membrane and leads to a momentary excess humidity, particularly in the leaf-tissues, and thus also to a momentaryexcess transpiration.The water-deficit regularly observed in wilt-literature is therefore not the cause of pathological wilting but, just as the wilting itself, a consequence of the distruction of the semipermeability of the plasma boundary layer.In a dilution of 10^–4 mol lycomarasmin apparently only affects the permeability of the exterior plasma boundary layer forwater, but not for sugars etc. Therefore it only produces an excess of fluid in the leaf tissues and thus an excess transpiration, but no definite inactivation of the plasma membrane and therefore also no pathological wilt.