用毛地黄皂苷分离异形胞及其对光合和固氮的某些特性的影响

本文叙述一种从多变鱼腥藻(Anabaena variabilis)中分离异形胞的简易方法。这种新方法是用毛地黄皂苷和甘露醇的 TES 缓冲液处理藻丝,破碎营养细胞,并结合分级离心的方法获得异形胞。所分离异形胞的纯度,在显微镜下观察达到90%左右。当提供 ATP 和Na_2S_2O_4时,能够测到所分离异形胞的固氮活性,其最大速率是5.31毫微克分子 C_2H_2/10~6异形胞/小时,为整体藻丝活性的10%。这种比活性,在4小时内,甚至更长的时间内,保持不变。但是,在氢气下和照光条件下,分离的异形胞缺乏受光促进的固氮活性。分离的异形胞在77°K下波长为430nm 光激发的荧光光谱和完整藻丝的相比,它缺乏属于光合系统Ⅱ的685nm 和695nm 的荧光发射峰,而仅具有光合系统 I 的730nm 荧光发射峰。当提供 DCIP 和抗坏血酸时,被压碎的异形胞能够光还原甲基紫精,其活性为360消耗 O_2的微克分子/毫克叶绿素/小时。上述结果表明用毛地黄皂苷法分离的异形胞具有较完整的 DCIPH_2→MV 的 PSI 活性。     

SOME ASPECTS OF PHOTOSYNTHESIS IN CLADOPHORA GLOMERATA1

Photosynthetic rates in field-collected samples of Cladophora glomerata were measured using the oxygen electrode technique. Rates observed were three- to fourfold higher than literature values obtained with the light and dark bottle method. The discrepancy appears to be due to light-limiting conditions prevailing in the bottles. It was also found that photosynthesis in Cladophora does not saturate at low light intensities as reported by other workers.     

SOME REMARKS ON THE PHOTOSYNTHESIS OF GREEN PLANTS

1. It is suggested that in the assimilation process of green plants the reduction of the CO₂ takes place with the help of Fe⁺⁺ ions (present in the chloroplast) under the influence of light, which is absorbed by a sensitizing chlorophyll-CO₂-complex. 2. It seems that the chlorophyll has to fulfill two different functions depending on its situation in the chloroplast. The chlorophyll molecules on the surface of the lipoid phase (in contact with an aqueous phase containing Fe⁺⁺) combine with CO₂ to form a light absorbing chlorophyll-CO₂-complex and in this way take part in the reduction of the CO₂. The light energy is also absorbed by the greater portion of the chlorophyll, which is dissolved in the interior of the lipoid phase, and eventually handed over to the chlorophyll molecules on the surface. 3. The photosynthetic unit of Emerson and Arnold may be determined by the ratio: See PDF for Equation so that for every chlorophyll molecule on the surface there are about 500 molecules in the interior, which provide it with the necessary quanta.     

MODES OF REPRODUCTION IN RUGOSE CORALS

A consideration of reproduction among fossil compound and 'solitary' rugose corals leads to the conclusion that(1) compound corals belonging to the order Rugosa must have been dimorphic and alternated between an asexual generation and a sexual generation; and (2) 'solitary' forms of rugose corals, although dominantly sexually-reproducing, included some individuals in which evidence of a repressed asexual generation is present.
The presence of a sexually-reproducing generation among compound corals cannot be demonstrated by clear morphological evidence, but is deduced from the observation that this is the most likely explanation for the origin of the initial corallite ('protocorallite') of a compound corallum.
It is proposed to restrict the term 'solitary' to non-compound individual corallites in which asexual budding is not observed and which therefore are presumed to have reproduced sexually. Simple corallites in which budding is observable are referred to as 'simple budding' forms. Thus, several described species of non-colonial rugose corals include both solitary individuals and simple budding individuals, including 'Lonsdaleoides' nishikawai Hayasaka & Minato, Timania rainbowensis Rowett, and 'Clisaxophyllum' awa atetsuense Minato & Nakazawa.     

SPECTRAL CHANGE OF LIGHT WITH DEPTH IN SOME LAKES AND ITS SIGNIFICANCE TO THE PHOTOSYNTHESIS OF PHYTOPLANKTON

1. A linear relation was found between the relative light intensityat 5 in depth and the mean chlorophyll a content of the euphoticzone, when they were plotted on logarithmic scales. The intensitiesof underwater lights of different wave lengths were measuredby a photocell with various colored filters. It was recognizedthat with the increase in chlorophyll a content the proportionof blue light fraction became reduced and that of red lightincreased. A similar relation was also found in the sea.
2. Thephotosynthetic rate.light relation was investigated withthesuspension of cultured Chlorella and Tabellaria. At lowlightintensities, the photosynthetic rate for red light waslargerthan those for blue and green lights. The photosyntheticrateunder the mixed light of red and blue was equal to thesum ofthe rates in the individual lights, so far as the intensityof each light was low. But when the intensity of red light wassufficiently high, the addition of blue light brought no furtherincrease in photosynthesis.
3. The photosynthetic rate-depthrelations were investigated bythe surface and underwater exposuremethods. Good agreementswere found between the results obtainedby these two differentmethods. However, there are some discrepanciesbetween the resultsof in situ exposure experiments and thoseobtained by the twomethods.

(Received January 11, 1963; )     

OXIDATIVE ASSIMILATION IN RELATION TO PHOTOSYNTHESIS IN CHLORELLA

1. An oxidative assimilation of acetic add and glucose in darkness has been demonstrated in the green alga, Chlorella pyrenoidosa. From manometric experiments it has been shown that 1 mol (CH₂O) per mol acetic add and 5 mols (CH₂O) per mol glucose are produced. 2. The time required for complete utilization of a limited amount of acetic acid or glucose is not affected by illumination in the absence of carbon dioxide. 3. The time required for complete utilization of a limited amount of glucose is not affected by the simultaneous occurrence of photosynthesis. It must therefore be concluded that the accumulating product of photosynthesis cannot be glucose but must be some slowly respirable (storage) material. 4. Possible interrelationships between oxidative assimilation and photosynthesis may be further studied by following, in darkness and in light, the time course of oxidative assimilation of substrates which are possible intermediates in the two processes.