Utilization of Exogenous Inorganic Carbon Species in Photosynthesis by Chlorella pyrenoidosa.
Utilization of Exogenous Inorganic Carbon Species in Photosynthesis by Chlorella pyrenoidosa.
复制标题
蛋白核小球藻光合作用中外源无机碳的利用。
作者：
B. Shelp;D. T. Canvin
使用三种实验技术（具有“人造叶”或“水”室的开放式气体分析系统和O（2）电极系统）测量碳同化作用，研究了蛋白核小球藻光合作用过程中利用的无机碳的性质。研究了光合作用与 pH 值和 CO(2) 浓度的函数关系。仅在高pH值下添加HCO(3)(-)时CO(2)浓度不足以满足光合作用的要求。在所有其他条件下，与高度可变的 K(m) (HCO(3) (-)) 相比，较低且恒定的 K(m) (CO(2)) 表明 CO(2) 是所利用的主要物种。在 pH 值高于 7.5 的限制 CO(2) 条件下观察到较高的光合作用速率，但 CO(2) 的水合速率与 HCO(3) (-) 支持光合作用刺激的观点不一致。在相同的 pH 范围内，在饱和 CO(2) 条件下观察到较低的光合作用速率。这些相互矛盾的变化似乎与 pH 值无关，而是与碳酸氢盐的一些尚未确定的作用有关。尽管在 CO(2) 饱和时，在后一种条件下观察到较低的最大光合作用速率，但在 CO(2) 被同化的条件下与 CO(2) 和 HCO(3) (-) 可以同化的条件下量子效率不同的观点没有获得支持。
The nature of the inorganic carbon utilized during photosynthesis by Chlorella pyrenoidosa was investigated using three experimental techniques (open gas analysis system with "artificial leaf" or "aqueous" chambers and O(2) electrode system) to measure carbon assimilation. Photosynthesis was studied as a function of pH and CO(2) concentration. The CO(2) concentration was inadequate to meet the requirements of photosynthesis only when HCO(3) (-) was added at high pH. Under all other conditions, the low and constant K(m) (CO(2)), in contrast to the highly variable K(m) (HCO(3) (-)), suggested that CO(2) was the major species utilized.Higher rates of photosynthesis were observed under limiting CO(2) conditions above pH 7.5 but rates of hydration of CO(2) were not consistent with the view that the stimulation in photosynthesis was supported by HCO(3) (-). In the same pH region lower rates of photosynthesis were observed under saturating CO(2) conditions. These conflicting changes seemed not to be related to pH but to some as yet undetermined effect of bicarbonate. No support was obtained for the view that the quantum efficiency was different under conditions where CO(2) was assimilated compared to conditions where CO(2) and HCO(3) (-) could be assimilated, although at saturating CO(2), lower maximal rates of photosynthesis were observed in the latter conditions.