Physiological Basis Of Jasmonic Acids In Malus Baccata Borkh.in Responding To The Stress Of Suboptimal Root-zone Temperature

According to the traits of air temperature warming rapidly but soil temperature lagging relatively in early growing season in Shenyang area,this study simulated the suboptimal root-zone temperature?ST?,combined with the treatments of girdling the trunk?GT?,removing the leaves?RT?,and the application of exogenous methyl jasmonate?MeJA?,calcium reagent and calcium inhibitors?EGTA and Nifedipine?,to study the responding characteristics of AOS,JMT,JAR1 key enzyme activities and AOS,JMT,JAR1gene expression of jasmonates synthesis,JA content and antioxidant capacity in Malus baccata Borkh.,to discuss the role of jasmonate in the process of information transmission between roots and leaves,and the interaction between extracellular calcium pool and jasmonates synthesis under suboptimal root-zone temperature.The main results are as follows:1.Under the suboptimal root-zone temperature,in 0-12 h of treatment,the changing trend of roots JA content in the GT was similar to that of ST,however,the roots JA content in GT was similar to CK and significantly lower than that of ST at 2h,and then the JA content increased and was slightly under the ST all the time.At 12h,roots JA content of GT was markedly higher than that of CK,but slightly lower than that of ST.RT treatment altered the changing trend of roots JA contend remarkably under suboptimal root-zone temperature,which of JA content slightly changed in the early 6 h of treatment and was significantly lower than that of ST.Under suboptimal root-zone temperature,leaves JA content of GT was obviously higher than that of ST all along.In conclusion,both GT and RT had the markable influence on roots JA content under suboptimal root-zone temperature.2.Under the suboptimal root-zone temperature,the AOS-activities of roots in GT and RT significantly decreased in the early 4 h,and then the activities of AOS were obviously higher than that of ST.Both GT and RT significantly inhibited roots JMT activities in 0-12 h.Compared with ST,the JAR1 activity of roots in GT significantly increased in the early 12 h,while the JAR1 activity of roots in RT significantly increased in the early 6 h.In GT,the activities of AOS and JAR1 of leaves significantly ascended,but the JMT activity descended.GT and RT significantly up-regulated the expressions of AOS of roots 6 h later.The expression of JMT gene of roots in GT and RT were significantly lower than that in ST all through the experiment except at the 24 h.The JAR1 gene expression of roots in GT was significantly up-regulated all through the experiment except the 6 h,which in RT was significantly up-regulated at the 2 h and the 24 h.3.Under the suboptimal root-zone temperature,the JA contents in JT and CT rose to some extent,which in CaCl₂treatment was significantly higher than that in MeJA treatment 6 h later.However,calcium inhibitor treatments reduced JA contents in roots to a certain extent.Under the suboptimal root-zone temperature,MeJA and CaCl₂treatments significantly increased the activities of AOS in roots.JMT activities in MeJA and CaCl₂treatments significantly increased in 2 h,and then the activities of JMT in those treatments were similar to that in ST,which were significantly higher in 24 h later than that in ST.Compared with ST,the activity of JAR1 in MeJA treatment was significantly increased,which of activity in CaCl₂treatment was similar to that in ST.The activities of AOS,JMT and JAR1 were inhibited to some extent by calcium inhibitor treatments.It is suggested that extracellular calcium pool was involved in the response of jasmonate synthesis in roots under the suboptimal root-zone temperature.4.Compared with the treatment of suboptimal root-zone temperature?ST?,MeJA and CaCl₂treatments significantly enhanced the activities of SOD and POD,however,the SOD and POD activities in calcium inhibitors treatments were similar to that in ST most of time.The CAT activities in MeJA and CaCl₂treatments strengthened in 0-12 h,and then closed to ST,while calcium inhibitors significantly suppressed CAT activities.Moreover,MDA contents in MeJA and CaCl₂treatments dramatically descended during the treatment of suboptimal root-zone temperature,which were dramatically ascended by calcium inhibitors.