Radmer R, Kok B, Ollinger O
Martin Marietta Laboratories, 1450 South Rolling Road, Baltimore, Maryland 21227.
Plant Physiol. 1978 Jun;61(6):915-7. doi: 10.1104/pp.61.6.915.
A mass spectrometer with a membrane inlet was used to monitor light-driven O(2) evolution, O(2) uptake, and CO(2) uptake in suspensions of algae (Scenedesmus obliquus). We observed the following. (a) The rate of O(2) uptake, which, in the presence of iodoacetamide, replaces the uptake of CO(2), showed a distinct plateau (V(max)) beyond approximately 30% O(2) and was half-maximal at approximately 8% O(2). We concluded that this light-driven O(2) uptake process, which does not involve carbon compounds, is saturated at lower O(2) concentrations than are photorespiration and glycolate formation. (b) In the absence of inhibitor, O(2) evolution was relatively unaffected by the presence or absence of CO(2). During the course of CO(2) depletion, electron flow to CO(2) was replaced by an equivalent flow to O(2). (c) There was a distinct delay between the cessation of CO(2) uptake and the increase in O(2) uptake. We ascribe this delay to the transient utilization of another electron acceptor-possibly bicarbonate or another bound form of CO(2).
使用带有膜进样口的质谱仪监测藻类（斜生栅藻）悬浮液中光驱动的氧气释放、氧气吸收和二氧化碳吸收。我们观察到以下情况。(a) 在碘乙酰胺存在的情况下，取代二氧化碳吸收的氧气吸收速率在约30%氧气以上呈现明显的平台期（V(max)），在约8%氧气时达到最大值的一半。我们得出结论，这个不涉及碳化合物的光驱动氧气吸收过程，在比光呼吸和乙醇酸形成更低的氧气浓度下就达到饱和。(b) 在没有抑制剂的情况下，二氧化碳的存在与否对氧气释放相对没有影响。在二氧化碳耗尽的过程中，流向二氧化碳的电子流被等量的流向氧气的电子流所取代。(c) 二氧化碳吸收停止和氧气吸收增加之间存在明显的延迟。我们将这种延迟归因于另一种电子受体（可能是碳酸氢盐或另一种结合形式的二氧化碳）的短暂利用。
