Effect of ethrel,chlormequat chloride and paclobutrazol on growth and pyrethrins accumulation in <Emphasis Type="Italic">Chrysanthemum cinerariaefolium</Emphasis> Vis.

Pyrethrins and flower yield of pyrethrum (Chrysanthemum cinerariaefolium Viz.) plants were determined after application of ethrel, chlormequat chloride and paclobutrazol. Ethrel at 50, 100, 250 and 500 mg l^−l produced a significant positive effect on pyrethrins level, decreased plant height, while 50 and 100 mg l^−l significantly increased fresh and dry flower yield. Chlormequat chloride at 1000 and 2000 mg l^−l and paclobutrazol (80 and 160 mg l^−l) increased pyrethrins level, single flower weight and decreased plant height and flower yield. ¹⁴C-acetate incorporation studies further substantiated positive effect of growth retardants on pyrethrins biosynthesis. The effect of growth retardants on pyrethrins seems to be mediated through its effect on biosynthesis.