Regulation of the diosgenin expression in Trigonella foenum-graecum plantsby 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 compou nd, on the diosgenin synthesis and/or accumulation process and their effect s on the growth of Trigonella foenum-graecum plants were investigated. Trea tment 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 mi ght be associated with the action that this growth regulator has in stimula ting 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 p pm ethephon increased the diosgenin levels observed in the leaves of 15- an d 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. (C) 1999 Elsevier Science Ltd. All rights reserved.