Preliminary Study On The Source Of H₂O₂ In The Growth Of Adventitious Roots Of Cucumber Hypocotyls By Auxin

The plant roots act as anchoring plants,absorbing water and mineral elements from the soil,synthesizing cytokinins,alkaloids and amino acids.A large number of reports indicate that the development of plant roots is regulated by many factors,including auxin,abscisic acid,ethylene,polyamines,NO and H2O2and so on.Among them,the interaction of auxin and H2O2 in the development of plant roots has been studied extensively,and it is pointed out that auxin may participate in the growth and developmental regulation of plant roots by inducing the synthesis of H2O2.-However,there have been few reports on the origin of H2O2 production during auxin-induced adventitious root growth.So,this paper will be study the relation about adventitious roots,auxin and H2O2In this experiment,the hypocotyls of cucumber seedlings were combined with exogenous indolebutyric acid(1BA),auxin polar transport inhibitor triiodobenzoic acid(TIBA)and naphthyl phthalamic acid(NPA).Exogenous H2O2,H2O2 scavenger N,N-dimethylthiourea(DMTU)and catalase(CAT)treatment were studied under IBA-induced cucumber Changes in fluorescence of H2O2 during the formation of adventitious roots of embryonic axes,and changes in activity of polyamine oxidase,cell wall peroxidase,NADPH oxidase,and glycolate oxidase,were as follows:1.Indole butyric acid(IBA)significantly promoted the growth of adventitious roots of cucumber hypocotyls at low concentrations.The optimal concentration was 0.05?mol/L,but inhibited at high concentrations.The auxin polar transport inhibitors NPA and TIBA significantly inhibited the growth of adventitious roots.2.Low concentration of hydrogen peroxide(H2O2)promoted the growth of adventitious roots in cucumber hypocotyls.The optimum concentration was 0.01%,and it was inhibited at high concentrations.H2O2 scavenger DMTU and CAT all significantly inhibited the growth of adventitious roots.The inhibitory effect of DMTU was stronger than that of CAT3.The promotion of adventitious root formation by IB A can be inhibited to varying degrees by DMTU and CAT;the inhibitory effect of auxin polar transport inhibitors naphthyl phthalamic acid NPA and triiodobenzoic acid TIBA on adventitious root growth partially recovered by exogenous H2O2.4.When incubated with H2O2 specific fluorescence probe(DCFH-DA)in IBA,NPA and TIBA treatment groups,it was found that exogenous IBA-treated cucumber hypocotyls had near their root primordia.The stronger fluorescence of H2O2,the fluorescence of NPA and TIBA treatment group was weaker or even absent,while the enhancement effect of IBA treatment on the fluorescence of adventitious root H2O2 could be obviously eliminated by DMTU and CAT5.Polyamine oxidase(PAO)inhibitors aminoguanidine(AG),cell wall peroxidase(CWPOD)inhibitors salicylhydroxamic acid(SHAM),glycolate oxidase(GO)inhibitors alpha-hydroxybutyrate(HBA)and NADPH oxidase-DPI and APO strongly inhibit the growth of adventitious roots.6.After treatment with IBA,the activities of these four H2O2-derived enzymes showed significant differences.Compared with the control,after treatment with IBA,there was no significant change in PAO,even lower than the control;Wall peroxidase(CWPOD)and glycolate oxidase(GO)are strongly promoted by IBA;NADPH oxidase activity is inhibited by IBA treatment.The above results indicate that low concentration of H2O2 can promote the growth of adventitious roots in cucumber hypocotyls,showing similar properties with auxin;auxin promotes the growth of adventitious roots in cucumber hypocotyls and its induced H2O2 production is related,and this H2O2 production shows significant IBA dependence.Polyamine oxidase,cell wall peroxidase,NADPH oxidase,and glycolate oxidase may be involved in the occurrence of adventitious roots in cucumber hypocotyls,but induced cucumber in IBA.The addition of H2O2,which is produced during the regeneration of adventitious roots from hypocotyls,may be due to the action of glycolate oxidasein addition to cell wall peroxidase.