ABSTRACT: To investigate the influence of HCO₃^- alkalinity on calcification in thalli of the genus Chara, we studied the effects of increased light level and additional HCO₃^- on calcification rate in C. vulgaris at various hours (30 min, 8 h, 12 h, 12.5 h, 20 h and 24 h after treatment) in a 24 h experiment (12 h light:12 h dark). We identified a significant Pearson’s correlation between exogenous dissolved inorganic carbon (DIC) concentrations and the utilization of DIC (µmol C g^-1 fresh weight). Plotting the daily rhythm of DIC utilization produced negative quadratic curves. Furthermore, calcification rate (µmol Ca h^-1 g^-1) was linearly related to DIC utilization rate (DIC_uptake; µmol C h^-1 g ^-1), indicating that the calcification rate is dependent on DIC_uptake. However, ratios of calcification to the utilization of DIC were decreased at high light intensity and increased with HCO₃^- addition, which was mainly ascribed to changes in the ratio of calcification to photosynthesis. Chlorophyll fluorescence results provided direct evidence for the promotion of photosynthesis in Chara thalli by both high light and DIC addition and their positive influence on maximum relative electron transport rate. These results suggest that calcification in calcareous C. vulgaris is mainly restrained by HCO₃^- alkalinity, which could explain the correlation between calcification of Chara thalli and alkalinity of water bodies in the field.

中文翻译：

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HCO3-碱度对寻常型甜菜钙化和溶解性无机碳利用的意义

摘要：探讨HCO的影响₃ ^-在菌体属上钙化碱度甜心，我们研究了增加的光水平的影响，并附加HCO ₃ ^-对钙化率普通小球藻在不同时间（30分钟，8小时，在24小时实验中（处理后12小时，12.5小时，20小时和24小时）（12小时光照：12小时黑暗）。我们确定了外源溶解无机碳（DIC）浓度与DIC（µmol C g ^-1新鲜重量）利用率之间的显着Pearson相关性。绘制DIC利用的每日节奏会产生负二次曲线。此外，钙化率（µmol Ca h ^-1 g ^-1）与DIC利用率（DIC_吸收； µmol C h ^{-1 -1} g ^-1）成线性关系，表明钙化率取决于DIC_吸收。然而，钙化DIC的利用率之比在高的光强度明显下降，并与增加的HCO ₃ ^-此外，这主要归因于在钙化的光合作用的比率的变化。叶绿素荧光结果提供了直接的证据，证明高光和DIC的添加都促进了Chara thalli的光合作用，并且它们对最大相对电子传输速率具有积极影响。这些结果表明钙化寻常型梭状芽胞杆菌中的钙化主要抑制由HCO ₃ ^-碱度，这可以解释的钙化之间的相关性甜心在现场菌体和水体的碱度。