Response of safflower (Carthamus tinctorius L.) growth and development to exogenous application of plant growth regulators

A field study was conducted over two growing seasons to evaluate the effects of foliar application of salicylic acid (SA) at 0, 0.1, 0.5 and 1 mM rates and paclobutrazol (PB) at 0, 50, 100 and 150 mg/l rates on the growth and development of safflower cv. Isfahan in Kerman, Iran. Both SA and PB increased leaf number, total biomass, head flower biomass, lateral branches, head flower number, seed number, seed yield, single seed weight and harvest index. The effect of SA was more pronounced at 0.1 mM and increased leaf number (19%), total biomass (44%), head flower biomass (58%), lateral branches (355%), head flower number (108%), seed number (72%), grain yield (83%) and harvest index (21%) compared with the controls. PB was more effective at 100 mg/l and increased leaf number (32%), total biomass (38%), head flower biomass (49%), lateral branches (380%), head flower number (66%), seeds number (48%) and grain yield (56%) compared with control. Moreover, none of the plant growth regulators (PGRs) affected seed oil and protein content.