Variations Of Phenolic Acids In Soil Of Apple Orchards And The Effect Of Phloridzin On The Acid Cycle

The experiment was conducted from2009—2012in root system lab, the Shandong keylab of fruit biology, Shandong Agriculture University. The composition and contents ofphenolic acids in the soil of replanted and no-replanted apple orchards around Loess Plateau,including Linyi, Pinglu, Baishui, Luochuan and Yintai, were analyzed. On the basis of furtherresearch of phlorizin, which is a characteristic phenolic acid of malus plants, experimentswere conducted to study the effects of phloridzin on the Tricarboxylic Acid Cycle （TCA） ofroots of Malus hupehensis Rehd. which were apple common stocks.The results showed that the composition and contents of phenolic acids in apple orchardwith replant diseases were different significantly among regions and soil thickness. Thecontents of phenolic acids decreased slowly over time. Phlorizin, pyrogallic acid andchlorogenic acid are main phenolic acids in replant soils.The mechanisms were discussed so as to provide a basis for further study on the cause ofapple replant disease. We selected phloridzin of4mM and KMnO₄of1mM in thepretreatment. Malus hupehensis Rehd. were planted in pot and were treated with phloridzin of4mM （T1）, phloridzin of4mM adding KMnO₄of1mM meanwhile （T2）. The content ofphloridzin in the soil and respiratory rate of roots were determined. Activities of enzymesrelated to TCA which include citrate synthase （CS）, aconitase, isocitrate dehydrogenase（ICDH）, α-ketoglutarate dehydrogenase （α-KGDH）, succinate thiokinase （SCS）, succinatedehydrogenase （SDH）, malic dehydrogenase （MDH）, fumarase （FUM） and pyruvatedehydrogenase （PDH） were also assayed. Treatments with T1inhibited the respiratory rate ofroots of Malus hupehensis Rehd., decreased obviously enzyme activities for the most partincluding CS, aconitase, ICDH, SCS, SDH, FUM, MDH only except for α-KGDH and PDHthat their enzymes activities were improving. However, treatments with T2had a criticaldifference from T1, it significantly enhanced the activities of CS, aconitase and MDH evenover the control level, increased obviously the activity of SCS being close to the control level,and to some degree improved the activities of ICDH, SDH and FUM. Besides, the activitiesof α-KGDH and PDH of T2treatments were assayed to be a lower level than T1yet over thecontrol level. Furthermore, the content of phloridzin in soil of T2was less than T1. Theresults showed that phloridzin at high concentration of4mM could inhibit the respiratory rateand the enzyme activities （7of9） related to TCA of roots of Malus hupehensis Rehd. with the treatments time following. The treatment of1mM KMnO₄can ease the above-mentionedadverse impact. If a proper concentration of KMnO₄could be applied to the horticulturalpractice, the degradation of phenolics of autotoxicity would be likely possible so as to relievethe specific apple replant disease.