Objective:To explore the effects of plant hormones on tomato root growth under aluminum stress,and to provide theoretical basis for enhancing the aluminum tolerance of tomato and breeding aluminum resistant tomato varieties.Methods:Cytokinin(6-BA),salicylic acid(SA),methyl jasmonate(MeJA),brassinolide(BL)and auxin analogues(NAA)were applied to explore the regulatory mechanisms of different plant hormones in tomato cultivars response to aluminum stress.Results:Cytokinin,salicylic acid and methyl jasmonate increased the sensitivity of tomato to aluminum stress,and increased the inhibitory effect of aluminum on root growth.Brassinolide had no significant effect on tomato root growth under aluminum stress.When exogenous NAA was applied,the lateral root development of tomato was promoted,but the growth inhibition of taproot and lateral root induced by aluminum was significantly aggravated,and the sensitivity of tomato to aluminum stress was increased.Exogenous application of auxin transport inhibitors(NPA and TIBA)also aggravated aluminium-induced root growth inhibition.Exogenous auxin synthesis inhibitor yucasin significantly alleviated the aluminium-induced root growth inhibition and decreased the sensitivity of tomato to aluminum toxicity stress.Using the auxin response reporter gene DR5:GUS transgenic tomato plants,it was found that aluminum stress promoted the accumulation of auxin cells in the meristem zone and the transition zone(between the meristem zone and the elongation zone)of root tips,and excessive auxin inhibited root elongation growth,while yucasin alleviated the root growth inhibition caused by aluminum stress by reducing the accumulation of auxin in root tips.Conclusion:The regulatory mechanism of tomato response to aluminum stress was analyzed through auxin synthesis pathway,and the application of auxin synthesis inhibitor yucasin alleviated aluminum stress in tomato,reduced the accumulation of aluminum ions and aluminum-induced reactive oxygen species(ROS)in tomato root tips,and reduced cell death.
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