De invloed van auxine, tryptofaan en enige anorganische zouten op de infectie van Nicotiana glutinosa met tabaksmozaiekvirus

The number of necrotic spots arising on leaves of Nicotiana glutinosa after inoculation with tobacco mosaic virus was less than in controls without additives, if the water in which the leaves floated hadβ-indoleacetic acid (IAA),α-naphthylacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D) in correct concentrations, added 16 h before (IAA also after) inoculation. This reaction occurred always in weak light but not always in strong light. D-tryptophan, but not DL and L isomers, caused a similar effect in only half the tests. In vitro IAA did not inactivate the virus. IAA, NAA and 2,4-D all decreased the osmotic pressure of the leaf sap of plants in weak light. IAA also decreased the conductivity of the sap of floating leaves by exosmosis. Leaves of plants in strong light had higher osmotic pressure, but if both leaf types were floated on water, the difference in osmotic pressure disappeared. Yet water absorption seemed not to be directly related to the decrease in osmotic pressure with IAA.A mixture of Ca (NO ₃ ) ₂ , KNO ₃ and MgS0 ₄ increased osmotic pressure and number of necrotic spots, although less with IAA than without it. Ca <sup>2+</SUP>increased and K <sup>+</SUP>and Mg <sup>2+</SUP>decreased number of spots. Perhaps phosphate-buffer enhanced auxin production, so masking the influence of the applied IAA. Probably IAA stimulated synthesis of enzymes and specific nucleic acid, so using up compounds needed for virus synthesis