Effects Of Seed Dressing On Plant Chemical Defense Response Of Maize Seedlings

Plant defense is a common phenomenon in plants and it is the main way for plants to fight against the disadvantages.Plant defense is controlled by genetic factors,but under different environmental factors,it will produce different defense responses.Plants adapt to the environment by regulating the activity of defensive enzymes and the content of secondary metabolites in plants.In this paper,imidacloprid and tebuconazole are used to study the changes of defense system in maize seedlings(Liyu35,Shengrui 999 and Aoyu 21).CAT,POD and PPO defense enzyme activity and plant defense substances(p-hydroxybenzoic acid,caffeic acid,cinnamic acid,syringic acid,coumaric acid,salicylic acid,ferulic acid and vanillic acid)content are examined to study the influence of two kinds of seed dressing agent on corn defense system..Besides,the contents of defense genes in different varieties of maize were measured to analyze the changes of defense ability.It has practical significance for improving plant pest resistance ability by using seed dressing agent.The main results of this experiment are as follows:(1)Liyu35,Shengrui 999 or Aoyu 21 dressing with imidacloprid or tebuconazole,the activity of CAT was increased(They were increased 3.6,2.3 and 2.8 times by dressing with imidacloprid and increased2.4,3.2 and 2.3 times by seed dressing with tebuconazole on the eighth day).The changes of POD and PPO were relatively complex.The activity of POD about Liyu35 seed dressed with imidacloprid was increased62.6 %.The other groups’ activity was decreased.But the activity of POD was close to the control group on the eighteenth day.The activity of PPO about Aoyu21 seed dressed with imidacloprid was increased37.5%.Other groups of PPO activity were decreased,Among them,Shengrui999 was restrained greater extent by the two kinds of seed dressing agent.It was decreased with 33.3% by seed dressing imidacloprid on the twelfth day and decreased 26.3% by seed dressing with tebuconazole.(2)Five kinds of phenolic acids were detected,The contents of syringic acid and ferulic acid were reduced about Liyu35 seed dressed with Imidacloprid.They were reduced 10.31μg/g and 4.3μg/g on the eighth day.And the contents of caffeic acid and ferulic acid were reduced 3.39μg/g and 6.31μg/g for Liyu35 seed dressed with tebuconazole.The contents of all the five phenolic acids were increased after Shengrui999 seed dressing with imidacloprid.The contents of caffeic acid and ferulic acid were reduced after Shengrui999 seed dressing with tebuconazole one the eighth day.But they were close to the controlgroup on the tenth day.All the contents of phenolic acids were reduced after Aoyu21 seed dressing with imidacloprid.And syringic acid and ferulic acid were impact largest.They were reduced 2.64μg/g and 3.09μg/g on the eighteenth day.The contents of ferulaic acid was reduced only for Aoyu21 seed dressing with tebuconazole,and it can close to the control group soon.The other contents of phenolic acids were increased.(3)The expression of Bx1,Bx6 and PR-2a were decreased 3.89 times,3.67 times and 1.5 times after Liyu35 seed dressing with imidacloprid on the eighteenth day,the others were increased.The synthetic gene of DIMBOA and direct defense proteins were inhibited,but it was increased the synthetic gene of total phenol and indirect defense protein.The expression of Bx1,MPI,TPS and FPS were decreased 4.04 times2.09 times 1.15 times and 2.43 times after Liyu35 seed dressing with tebuconazole on the eighteenth day,the synthetic gene of DIMBOA,direct defense protein and indirect defense protein were inhibited,but the synthetic gene of total phenol was increased.All the kinds of genes were increased after Shengrui999 seed dressing with imidacloprid,and it can increase the synthetic gene of DIMBOA,Total phenol and indirect defense protein.The expression of PR-2a was decreased 3.01 times after Shengrui999 seed dressing with tebuconazole on the Fourteenth day.The synthetic gene of DIMBOA,total phenol,indirect defense protein were increased.The expression of PAL was decreased 3.48 times only after Aoyu21 seed dressing with imidacloprid,the synthetic gene of DIMBOA,direct and indirect defense proteins were increased.The expression of Bx6,TPS and FPS were decreased after Aoyu21 seed dressing with tebuconazole on the eighteenth day,the synthetic gene of DIMBOA and indirect defense protein were inhibited.