The impact of mycorrhizal inoculation on amelioration of the effects of haloxyfop-R methyl ester herbicide on sunflower

To study the effects of inoculation by arbuscular mycorrhizal fungus (Glomus intraradices) in ameliorating the effects of haloxyfop-R methyl ester herbicide (commercial name Gallant super) on biochemical activity and hormonal responses of sunflower (Helianthus annuus L., cv. Lakomka) a factorial experiment was conducted in a completely randomized design with 4 levels of herbicide concentration (0, 25, 50 and 75 ppm) in 3 replications. At 4 to 6 leaved stages, different concentrations of herbicide were sprayed on the aerial part of the plants. The effects of herbicide on colonization percentage, dry weight and other parameters of control and mycorrhizal treated plants were quite evident. Increased gibberellin content (60%) in inoculated plants, reduced amount of auxin in shoot of the control plants (48%) were observed by increasing herbicide concentration compared to the control. Furthermore, increased proline (1.5 and 2.7 fold), increased soluble sugars content (36.5% and 23.5%), reduced total proteins (29.2% and 40.1%) and reduced dry weight (61.3% and 76.0% in shoot and root respectively) were significant. More damage occurred by increased herbicide stress conditions and plants responded by raising the level of gibberrelins, proline and soluble sugars to cope the damages induced by haloxyfop-R methyl ester. Such adaptive responses were more pronounced and effective in inoculated plants by arbuscular mycorrhizal fungus G.intraradices. So, it seems that inoculation sunflower seedlings by G. intraradices can enhance their tolerance against deleterious effects of that herbicide.