پاسخ فسفومونواسترازها به افزودن آهك در خاكهاي اسيدي با مديريت متفاوت

چكيده انگليسي :

AbstractPhosphomonoesterases are widely distributed in nature They play an important role inP mineralization in soils via breaking the phospho esteric bonds Acid phosphatase andalkaline phosphatase are two predominant soil phosphomonoesterases which both areinvolved in the mineralization of P and therefore contribute in providing inorganic P forplant growth and development The enzymes are sensitive to the environmental pH andhence thought to be sensitive to lime application Moreover it has been suggested thatthey respond to management practices as well as land use changes However ourunderstanding regarding the mechanism s by which calcium carbonate influence theactivity of acid and alkaline phosphatase is obscure The main objective of this studywas to perform a mechanistic approach to the effects of calcium carbonate applicationon acid and alkaline phosphatase activities total phosphomonoestaerase activity and theratio of acid to alkaline phosphatase activity under different management practices Forthis purpose we collected our soil samples from three acidic soils of forest anddeforested counterparts of three ecosystems including Lahijan 37 11 N 50 01 E Langroud 37 10 N 50 07 E and Gisum respectively 38 40 N 49 01 E and 38 40N 49 03 E forest standings in Gilan Province Northern Iran The effects of calciumcarbonate application were assessed under two time span including 7 and 73 daysfollowing incubating soils under optimum moisture and temperature Application ofcalcium carbonate resulted in pH increases while soil pH ranges were 0 2 to 0 5 unitlower under 73 days of incubation Both enzymes showed to be pH dependent so thatacid phosphatase activity was negatively associated with calcium carbonate induced pHincrease whereas alkaline phosphatase increased as pH enhanced due to calciumcarbonate application Comparing acid and alkaline phosphatase in terms of the rate ofresponse the acid phosphatase activity was much more responding Furthermore therate of response was increased when the samples incubated for 73 days compared to 7days Path analysis as an statistical approach was performed to discriminate direct andindirect effects of calcium carbonate on the enzyme activities The effects of Ca2 andCO32 are presumably the direct and that H or OH are thought to be the indirect effectsof calcium carbonate application on the enzyme activities The results indicated thatboth enzymes are more influenced by the indirect pH than direct effects of calciumcarbonate application In other word the enzymes are rather influenced by the inhibitoryeffects of either H or OH under increasing pH conditions This finding leads us toinvestigate the effects of calcium carbonate induced pH enhancement by an ED50approach and interestingly figured out that the rectangular hyperbolic models generallyfitted well to the data Better results were obtained when partial inhibition model model2 used compared to the complete inhibition model model 1 The model parameterswere not only influenced by the incubation time but also they showed to be sensitive tomanagement history of the soils Overall we conclude that lime applicationsignificantly influences the pH of the acid soils and the pH change is the main factorthat performs further effects on the activity of acid and alkaline phosphatases total soilphosphomonoestaerase activity and the ratio of acid to alkaline phosphatase activity Itappeases that both H and OH acts as inhibitors on the enzymes and the rate of theinhibitors can be successfully assessed in particular with the partial inhibition modelwith an ED50 approach based on the rectangular hyperbolic model We suggest furtherinvestigation on the effects of pH changes on the inhibitory effects of trace metals onthe soil enzymes when lime is applied as an amendment Key wordsphosphomoesterase history of land management lime ED50

خسروزاده قمي، ساجده

پاسخ فسفومونواسترازها به افزودن آهك در خاكهاي اسيدي با مديريت متفاوت

تاريخچه مديريتي خاك , كربنات كلسيم , ٍٍED50