An auxin-auxotrophic mutant of Nicotiana plumbaginifolia.

Auxin (indole-3-acetic acid) is considered to be an important signalling molecule in the regulation of plant growth and development but neither auxin synthesis nor its mode of action is clearly understood. To identify genes involved in these processes, mutations were sought that altered the auxin requirement of plant tissues for growth. For the first time mutant plants were obtained that carry a recessive mutation at a single nuclear locus (aux1) which results in an absolute requirement for exogenous auxin for normal growth. In the absence of auxin treatment, mutant plants undergo premature senescence and die.