BTH Regulates Monoterpenes Volatile In Lilium ’Siberia’ By Regulating The Content Of H₂O₂

Making people feel pleasure,as one of the most important ornamental characters of plants,plant aroma sometimes also causes anxiety or allergic reactions due to its strong smell.Lilium‘Siberia’possesses rich smell.Given priority to monoterpenes volatiles,this study aims to regulate monoterpenes volatiles of Lilium‘Siberia’by BTH treatment,to make it smells relatively moderate and mild,and to explore the possible regulation mechanism.The VOCs of lilium treated with BTH and H₂O₂ was determined by SPME-GCMS,and the key terpene synthesis enzyme gene were quantitatively analysed by q RT-PCR.Meanwhile,spectrophotometry was widely used to detect the enzyme activity of H₂O₂ metabolism enzyme of lilium as well as the content of endogenous H₂O₂.The results are as follows:1.BTH treatments delayed the aging of cut lilium:BTH treatments appropriately prolonged the vase life of lilium.Vase life of lilium reached 8 days with the BTH treatment of 350 mg/L,while the control group is about 6.75 days,which increased by about 1.25 days on average.BTH treatment decreased the trate of fresh weight change and value of water balance as well.2.BTH treatments significantly inhibited the release of lilium monoterpenes compounds:All concentrations of BTH treatments down-regulated total monoterpenes of lilium,with an inhibition rate from highest to lowest:350 mg/L>500 mg/L>50 mg/L BTH.The inhibition rate of 50 mg/L BTH to monoterpenes was 39.97%,the inhibition rate ofβ-myrcene and（Z）-β-ocimene was30.53%and 31.69%respectively,and the inhibition rate of linalool was 43.57%.The inhibition rates of monoterpenes at 350 mg/L were 59.89%,58%ofβ-myrcene,55.56%of（Z）-β-ocimene,and 61.53%of linalool.The monoterpene inhibition rate of 500 mg/L was 47.53%,the inhibition rate ofβ-myrcene was 41%,the inhibition rate of（Z）-β-ocimene was 40.27%,and the inhibition rate of linalool was 50.77%,which were also very significant.3.BTH could significantly down-regulate the expression of Li DXS gene:Li DXS,Li DXR and Li TPS,the three key enzymes genes in the metabolic pathway of monoterpenes in lily,were all decreased under BTH treatments,in which the expression of Li DXS decreased significantly,only20.4%of the control group.The other two were also on a downward trend.4.By inhibiting the enzyme activity of NOXs and SOD and activating the activity of APX and GPX,BTH significantly reduced the endogenous H₂O₂ content of lilium.5.H₂O₂ content had an important effect on the release of monoterpenoids from lily:Exogenous H₂O₂ induced the release of lilium terpenes,while DMTU inhibited the release of lily terpenes.6、H₂O₂ plays an important role in the biological process that BTH down-regulated the release of monoterpenoids in Lilium‘Siberia’.By defining regulatory relationship between BTH and monoterpene,BTH and H₂O₂ and H₂O₂and monoterpene,this study preliminarily established the BTH→H₂O₂→monoterpene biological control process,namely by inhibiting NOXs and SOD enzyme activity,and activate the APX and GPX enzyme activity,exogenous BTH consume a large amount of As A and GSH,and made H₂O₂ content significantly lower.Lowered H₂O₂ by changing the cell environment made the key enzymes of terpenoids synthesis decreased,and eventually led to Lilium’Siberia’released less terpenoids.To sum up,in this study,the optimal concentration of BTH treatment was screened.The significant inhibition of BTH on the release of monoterpenes volatiles in lilium was confirmed,and it was found that BTH treatments could down-regulate the expression of three key enzymes genes in terpene synthesis and affect the metabolism of endogenous H₂O₂ in lilium.The regulation mechanism of H₂O₂was further discussed.The results lay a foundation for perfecting the regulation theory of floral fragrances and promoting the practical application of floral modulators.