Regulation of the diosgenin expression in Trigonella foenum-graecum plants by different plant growth regulators

The effect of indole-3-acetic acid (10−4 and 10−5 M), gibberellic acid (10−4 and 10−5 M) and ethephon (50 ppm) as an ethylene releasing compound, on the diosgenin synthesis and/or accumulation process and their effects on the growth of Trigonella foenum-graecum plants were investigated. Treatment with 10−5 and 10−4 M gibberellic acid led to 43 and 19% increases, respectively, of diosgenin in 30-day-old whole plants. These increases might be associated with the action that this growth regulator has in stimulating plant growth and the biosynthetic pathway of this sapogenin. A smaller increase was obtained with the 10−5 M indole-3-acetic acid treatment (6%, in 30 day-old plants), probably due to a stimulation of the biosynthetic pathway, alone, since no effect on growth was observed. Treatment with 50 ppm ethephon increased the diosgenin levels observed in the leaves of 15- and 30-day-old plants, growth of the whole plant being substantially reduced at 30 days in comparison with the growth observed in control plants. These figures reflect a 77% increase in diosgenin levels in 15-day-old plants and a decrease of 68% in 30-day-old plants.