Effects Of NaCl And Na₂CO₃ Stresses On Enzymes Activities Related To Citrate Metabolism In Puccinellia Tenuiflora

Puccinellia tenuiflora (Griseb. ) Scribn. et Merr. is a topical alkali-tolerant plantgrowing in Songnen Plain located in the North-east area of China where the soil is excessivealkalization. Some researchers found Puccinellia tenuiflora specially accumulated citrate inthe shoot under alkaline (Na₂CO₃) treatment after several h. Hence the alkali-tolerant plantPuccinellia tenuiflora was selected as material, and citric acid accumulation and metabolismunder alkali-stress in it were investigated.We analyzed four enzymes activities associated with citrate metabolism of P. tenuiflorashoot and root under salt (NaCl: 0-500mM/L Na⁺) and alkaline (Na2CO3: 0-500mM/L Na+)respectively: citrate synthase (CS, EC 4.1.3.7),NADP-isocitrate dehydrogenase(NADP-ICDH, EC1.1.1.42), phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31)and malate dehydrogenase (MDH, EC 1.1.1.37). Results indicated salt affected organic acidmetabolism negligibly, either in the shoot or root of P.tenuiflora ( high stress intensityinduced ICDH and PEPCase in root to lose activities). Alkaline induced CS and PEPCaseactivities in the shoot of P.tenuiflora improved, especially citrate synthase activity enhanceddistinctly;in opposite NADP-ICDH activity declined. As to MDH, it was unaffected oraltered negligibly. Under low alkali-stress intensities, CS and PEPCase activities in the rootwere as the same as in the shoot, whereas when it reached some extent, stress induced theroot to damage to low acitivity.as stress intentsity went on, acitivity of ICDH in the rootdrasticly declined following some up-grade at the beginning, MDH was not affected.Results demonstrated alkaline improved CS and PEPCase activities and suppressedICDH activity in P. tenuiflora shoot coincided with citrate content rise in P. tenuiflora shoot,indicating alkaline induced citrate accumulation in the shoot is relevant with CS, PEPCaseactivities increase and ICDH activity decrease in the shoot. Adjustments to CS, ICDH andPEPCase activities are the biochemical basis of citrate accumulation in the shoot of P.tenuiflora under alkaline (Na₂CO₃) treatment...