Investigations on the auxins in tomato crown-gall tissue

Abstract

Galls were induced to form on the stems of tomato plants by inoculation with Agrobacterium tumefaciens . Free ether-soluble auxins in the galls and in normal tomato stem tissue were extracted and the acidic and neutral fractions of the extracts were examined by paper chromato­graphy. Evidence for the presence of 3-indolylacetie acid ( IAA ), 3-indole-carboxylic acid ( ICA ) and 3-indolyl-acetonitrile ( IAN ) was found in both the crown-gall and normal stem tissue extracts. This evidence was based on R f values, chromogenic reactions, bioassay results and in the case of ICA on fluorescence in ultra-violet light. Further confirmation of the presence of IAN was obtained by its conversion to IAA by alkaline hydrolysis. The auxins in the gall extracts were the same as those in the normal stem extracts, but were present in greater amounts. The amount of free IAA in the crown-gall tissue was estimated to be 8 to 12 μg/kg. A transient IAA -like colour reaction with Ehrlich reagent was observed in the IAA position on chromatograms containing gall or normal stem tissue extracts. The position of the spot corresponded closely with that of IAA in all solvents investigated. It was concluded that the reaction was not due to IAA but to a compound with properties which enable it to be readily mistaken for IAA on chromatograms treated with Ehrlich reagent. Areas were present on chromatograms of both normal stem and gall tissue extracts which corresponded with the ‘inhibitor β ’ of Bennet-Clark & Kefford (1953). Unknown water-soluble growth promoting substances insoluble in ether were found to be present in the aqueous fluids expressed from both tissues.