Study On The Regulation Of Jasmonic Acid On The Laticifer Differentiation Of Taraxacum Kok-saghyz Rodin

?Objective?In this study we discussed the induction of plant growth regulator Me JA on TKS laticifer differentiation,from which to ensure the optimum Me JA treatment concentration to promote the TKS laticifer differentiation.?Methods?The study selected one-month old,three-month old and four-month old TKS plants for materials,the Me JA concentrations were 0.25,0.50,1.00,2.00 and 5.00 mmol/L.The TKS sprayed distilled water with 2.2% ethanol was the control.In this researsh we studied the effects of different concentrations of Me JA on the agronomic traits,leaf chlorophyll content,root activity,endogenous hormone content,root PAL activity,root lignin content and root phloem bundle lap.?Results?(1)The one-month-old TKS were sprayed with 5 concentrations.The results showed that: Taproot length,taproot thickness and root shoot ratio were increased at these 5 concentrations.The synthesis of chlorophyll was enhanced,which was significantly higher than that of the control and the plant root activity was significantly enhanced too.The contents of endogenous ZR,IAA and Me JA in roots were significantly higher than those in the control.GA3 content was significantly increased at 1.00 mmol/L Me JA,the changes were not significant under other concentrations.The synthesis of ABA was promoted at low concentration,but inhibited in high concentrations.The content of 6-BA increased at 0.50 mmol/L Me JA and decreased at high concentration.These 5 concentrations of Me JA could induce PAL activity and reached the maximum at the concentration of 5.00 mmol/L Me JA.1.00 mmol/L Me JA promoted the increase of lignin metabolism,increased its content,while inhibited in high concentrations.The phloem bundles laps were significantly different from that of the control at 0.25,0.50 and 1.00 mmol/L Me JA,which were 29.4%,35.3% and 47.0% respectively,compared with the control.(2)The three-month-old TKS were sprayed with 5 concentrations.The results showed that: There were no significant changes in the leaf width and root thickness at these 5 concentrations of Me JA.The treatment of 5.00 mmol/L Me JA significantly increased the root shoot ratio compared with other treatments,While the taproot length was significantly decreased.The leaf length and leaf area increased when treated with 2.00 and 5.00 mmol/L.The contents of endogenous IAA,Me JA,ABA,GA3 and ZR in the roots increased under these 5 treatments,and the change of 6-BA content was not obvious.Root activity decreased after treated with all concentrations,but the difference between each treatments was not significant.The lower concentrations of Me JA could induce PAL activity,while the high concentrations of promoting effect were not significant.Lignin content did not change significantly at each concentration,and the phloem bundles laps decreased at 2.00 and 5.00 mmol/L Me JA,but there were no significant differences with the control.(3)The four-month-old TKS were sprayed with 5 concentrations.The results showed that: These 5 concentrations decreased chlorophyll biosynthesis,its contents reduced.The treatment of 0.25 mmol/L Me JA could promote the increase of root activity,but its activity were decreased under high concentrations.1.00 and 2.00 mmol/L Me JA could significantly enhance the PAL activity.These 5 concentrations promoted the lignin metabolism and increased its contents which increased along with the increase of spraying 5 concentrations.Me JA had no significant effect on the laticifer differentiation for the four-month-old TKS,and there were no significant differences in the phloem bundles laps of root between treatments and control.?Conclusions?In summary,the effects of different concentrations of Me JA on the TKS differentiation were studied in different developmental stages.It was found that the one-month-old materials were more sensitive to Me JA than that of three-month-old and four-month-old materials,and Me JA promoted the role of laticifer differentiation more significantly.The phloem bundles lap was significantly different from that of the control when treated with 1.00 mmol/L Me JA,which was 47.0% higher than that of the control.Therefore,it was considered that one-month-old TKS treated with 1.00 mmol/L Me JA was the optimum treatment concentration for the best time to promote the laticifer differentiation.At the same time,the taproot length,taproot thickness,chlorophyll content,root activity,root endogenous hormones(ZR,IAA,Me JA,GA3)contents,PAL activity and lignin content were all higer than the control.The increasing of PAL activity and lignin content were also beneficial to the enhancement of TKS resistance.