Effect of exogenous auxin on root morphology and secondary metabolism in Tagetes patula hairy root cultures

In this paper the effects of indole‐3‐acetic acid (IAA) on growth of Tagetes patula hairy root cultures and secondary product formation are presented. The biosynthesis of thiophenes, sulfurous compounds with nematicidal activity, was inhibited by IAA application, as was evident from a decrease of [35S] sulfur incorporation. The inhibition only occurred after the roots had developed numerous laterals as a result of auxin action. However, in roots cultured in the absence of IAA, there was no significant correlation between branching and thiophene accumulation. Therefore, development of lateral roots is not a sufficient condition for a low capacity to synthesize thiophenes. The highest rate of thiophene accumulation in the roots culture is at its maximum. Hence, growth and the production of thiophenes appear to be compatible in T. Patula hair roots.