碳酸氢根缓解高营养负荷下苦草(Vallisneria natans)胁迫的作用

Mitigtive effect of HCO_3^- -DIC on eutrophication stress on Vallisneria natans

富营养化湖泊沉水植物严重退化,可溶性无机碳DIC(Dissolved Inorganic Carbon)缺少是一个重要因素。本实验选择碳酸氢根形态DIC(HCO3--DIC)对苦草进行处理,设计了不同的HCO3--DIC添加量(0、10、20mg·L-1)和营养水平N、P(N0.96、1.92、2.88、3.84mg·L-1,NH4+-N:NO3--N=1:3,N:P=27)的交叉实验,研究不同营养水平下HCO3--DIC对苦草(Vallisneria natans)的生理生态影响。实验证明,苦草幼苗在生长过程中可以不断吸收水体中的DIC,经15d培养,培养液中DIC从16.91mg·L-1下降到6.27mg·L-1。21d的实验结果显示,相同营养条件下高质量浓度HCO3--DIC组苦草相对生长率RGR(Relative Growth Rate)高于其他组;无外加HCO3--DIC组过氧化物酶POD(peroxidase)活性随营养水平增加,从2.01U·mg-1增至4.03U·mg-1,相同营养水平下POD活性随HCO3--DIC增加而降低,说明水体营养水平的增高加剧了对苦草生长的胁迫,而HCO3--DIC大大减少和缓解了这种胁迫作用;中营养条件下,较低水平的HCO3--DIC质量浓度已经满足苦草叶绿素合成,而在重富营养时较高质量浓度的HCO3--DIC可以促进苦草叶绿素合成,缓解营养胁迫的黄化效应。研究揭示,水体HCO3--DIC增加可以缓解富营养化对沉水植物的胁迫作用。

Shortage of DIC （Dissolved Inorganic Carbon） is an important factor on the degradation of submersed plants in eutrophic lakes. Seedling growth experiment showed that Vallisneria natans could use DIC, the concentration of DIC decreased from 16.91 mg·L^-1 to 6.27 mg·L^-1 after 15 days＇ culture. In our 21 days＇ experiment, Vallisneria natans were used for Orthogonal experiment design of HCO3 and N, P, comprising three concentration of added HCO3-DIC （0, 10, 20mg·L^-1） and four separate nutrient loadings （0.96, 1.92, 2.88, 3.84 mg·L^-1 N, NH4^＋-N： NO3-N=I： 3, N： P=27）. During the 7 days＇ exchange water cycle, Relative Growth Rate （RGR） of Vallisneria natans was higher than the other groups with more HCO3-DIC under the same nutritional condition. Peroxidase （POD） activity increased from 2.01 U·mg^-1 to 4.03 U·mg^-1 as the nutrition increased without HCO3- DIC addition, and decreased with increased HCO3^- -DIC under same nutritional conditions. For the synthesis of chlorophyll, less HCO3^- -DIC was enough under lower nutritional conditions, however, more HCO3^- -DIC was needed under Hypertrophic conditions. Due to the mitigative effect of HCO3^- -DIC on eutrophication stress in Vallisneria natans, HCO3^- -DIC addition in the eutrophic lakes was beneficial to submersed plants restoration.