【摘要】 用满江红[Azolla imbricata（Roxb）Nakai]和蕨状满江红[Azolla filiculoides Lam.]研究了固氮酶催化的 C₂H₂还原和放 H₂,光合吸收 CO₂以及在封闭系统中同时测定了 C₂H₂还原、光合作用和呼吸作用。结果如下:1.固氮酶催化的 C₂H₂还原基本需光。满江红的光饱和点大约在10,000勒克司。气相中C₂H₂分压为10%时,C₂H₂还原已达饱和。1%CO 已抑制 C₂H₂还原,同时有 H₂的释放。2.测定了 A.imbricata 和 A.filiculoides 的 C₂H₂还原活性随叶片年龄的变化。这两种满江红的顶端活性是极微的,随着叶片年龄的增长,活性明显提高,接着出现一个活性高峰的“平台”,然后随叶片衰老而活性下降。这种活性梯度由于形态上的差异,A.imbricata 比 A.fili-culoides 的更陡。3.A.imbricata 固氮酶催化的放 H₂,在氩气中未能检出,但在氩中含15%C₂H₂和2%CO 时可以测到。在后一种气相中还测定了放 H₂随叶片年龄的变化。这些结果说明存在着一种吸氢酶。4.A.imbricata 和 A.filiculoides 在空气中的光合 CO₂补偿点在30ppm 左右。5.用 A.imbricata 同时测定光合作用、呼吸作用和 C₂H₂还原,证明固氮酶活性直接依赖于光合作用捕获的光能,而不是直接依赖于 CO₂固定。更多还原

【Abstract】 Azolla imbricata and Azolla filiculoides were studied in regard to:the nitrogenase- catalyzed reactions of C₂H₂ reduction and H₂ production,employing gas chroma- tography;and photosynthetic CO₂ uptake as well as simultaneous determinations of C₂H₂ reduction,photosynthesis and respiration in a closed system.Photosynthetic CO₂ uptake and respiratory CO₂ production were determined using an infrared gas analyzer.These studies have indicated the following 1.Nitrogenase-catalyzed C₂H₂ reduction is largely light dependent.About 10,000 lux were required for saturation in A imbricata.A concentration of 10% C₂H₂ in the gas phase is saturating for C₂H₂ reduction and 1% CO inhibits C₂H₂ reduction with concomitant H₂ production.2.A determination of C₂H₂ reduction activity as a function of leaf age established a develop mental gradient in both A.imbricata and A.filiculaides.In both species activity is negligible in the apex,increases markedly in progressively older leaves,plateaus,and decreases as leaves senesce.The developmental gradient of activity is much steeper in A.imbricata than in A. filiculoieds due to differences in their gross morphology.3.Nitrogenase-catalyzed H₂ production in A.imbricata was not detectable under Ar but was appreciable under Ar containing 15% C₂H₂ and 2% CO.H₂ production was also determined under the latter gas phase as a function of leaf.These studies implicate the occurrence of an uptake hydrogenase.4.The photosynthetic compensation points in air are approxi- mately 30 ppm CO₂ for A.imbricata and A.filiculoides.5.Simultaneous measurements of photosynthesis,respiration and C₂H₂ reduction in A.imbricata demonstrated the im- mediate dependence of nitrogenase on photosynthetically captured radiation for energy but an indirect dependence on CO₂ fixation.更多还原