Effects of alkalinity variations on photosynthetic activity and exopotysaccharides of <i>Chlorella pyrenoidosa</i>

Abstract

本文研究了不同重碳酸盐(HCO₃^-)碱度2.3mmol/L(ALK2.3)和12.4mmol/L(ALK12.4)条件对蛋白核小球藻光合活性、色素组成、丙二醛(MDA)含量与胞外多糖的影响.实验结果表明,碱度增加对蛋白核小球藻光合活性呈促进-抑制-促进效应,ALK2.3对光合活性影响的强度高于ALK12.4.碱度增加提高叶绿素b/叶绿素a(Chl.b/Chl.a)的值,降低类胡萝卜素/叶绿素(Caro/TChl)的值,并且ALK12.4条件下对藻细胞的作用程度强于ALK2.3.此外碱度增加刺激蛋白核小球藻胞外多糖分泌,ALK2.3在培养初期提高MDA含量,ALK12.4下细胞MDA含量显著降低.说明碱度增加会促进蛋白核小球藻光合活性,促进光合产物的积累与分泌.暗示胞外多糖的分泌可能是细胞适应高碱度的一种自我保护机制.;Effects of bicarbonate (HCO₃^-) alkalinity on the photosynthetic performance of Chlorella pyrenoidosa was investigated inpresent study. Photosynthetic activity, pigments, MDA and ultrastructure of Chlorella pyrenoidosa were measured for when they werecultured at two different alkalinities including 2.3mmol/L (ALK2.3) and 12.4mmol/L (ALK12.4), respectivily. At ALK2.3,photosynthetic activity was stimulated at the prophase of culture and then inhibited at the anaphase. At ALK12.4, it represented thesame phenomenon, but inhibition effects were weaker than those at ALK2.3. Ratios of Chl.b/Chl.a was increased, but Caro/T Chlratios was decreased at elevated alkalinities. The contents of MDA increased at ALK2.3 and decreased at ALK12.4. In addition,secretion of glycocalix-like layer was remarkably stimulated at elevated alkalinities. These results showed that elevated alkalinitiespromoted algae carbon assimilation and stimulated secretion of glycocalix-like layer. Carbohydrate could alleviate stresses at elevatedalkalinities. Secretion of glycocalix-like layer could decrease the synthesis of excess products of photosynthesis and relieve feedbackinhibition, which will increase the stress tolerance of C. pyenoidosa at elevated alkalinities.