THE CONTROL BY PHYTOCHROME OF NITRATE REDUCTASE IN THE CURD OF LIGHT-GROWN CAULIFLOWER

Abstract— The activity of nitrate reductase from the curd of light-grown cauliflower ( Brassica oleracea (L) var botrytis (DC) 'St. Hilary') is modulated by nitrate and by light. Using broad-band sources of equal photosynthetically active radiation but with different proportions of red and far-red light, a linear relationship between nitrate reductase activity and ψ(Estimated phytochrome photoequilibrium) was obtained. This relationship, apparent after 8 h incubation, was maintained and little altered after 48 h incubation. The linearity was apparent between ψE 0.26 and ψE 0.69; ψE 0.26 being no more effective than a dark control. Far-red reversibility confirmed the involvement of phytochrome. Brief pulses of red light were also used to establish a range of phytochrome photoequilibria within the tissue. Again a linear relationship between ψ and nitrate reductase activity was obtained with a threshold for the response at ψ 0.3. With both monochromatic and broad-band sources it was seen that neither photon fluence rate nor duration of exposure affected the final activity of the enzyme and that phytochrome was acting solely through ψ (or [Pfr] since phytochrome is stable in this tissue) to bring about these responses.     

REGULATION OF NITRATE REDUCTASE ACTIVITY IN RICE

The properties of NR from rice varieties Yuanfengzao and Jingyin 127 are the same in molecular weight of native enzyme and subunit, optimum pH, K_m value for substrates NO_3~- and NADH, stability in vitro and immunological characteristics. The decay rate in vitro of the activity of the partially purified NR from Yuanfengzao is 20％ lower than that from Jingyin 127. The results from antiserum titration and rocket immunoelectrophoresis indicated that the amount of NR in Yuanfengzao is about 1.5 times more than that in Jingyin 127. Further study on in vivo incorporation of ~3H-labeled amino acids into NR revealed that the rate of NR synthesis in Yuanfengzao is obviously higher than that in Jingyin 127. In vitro translation of mRNA showed that the products of NR-mRNA per unit of total mRNA of Yuanfengzao is much more than that of Jingyin 127. It is concluded that, therefore, NR activity in rice is regulated through NR synthesis and NR-inhibitory protein(s) system, the former is further controlled at the lev     

离子色谱法同时测定叶菜中的硝酸盐和亚硝酸盐

采用抑制型离子色谱法同时测定叶菜中的硝酸盐和亚硝酸盐的含量。色谱柱为Ionpac AS11柱，流动相为21mmol/L NaOH溶液，检测器为电导检测器（CD），流动相流速为1.0mL/min。该方法简便、快捷，准确度和灵敏度高，NO2^-和NO3^-的回收率分别为97％－105％和95％－104％，相对标准偏差RSD＜5．0％。同时考察了样品浸提时间对结果的影响。     

PHYTOCHROME AND EFFECTS OF SHADING ON GROWTH OF WOODLAND PLANTS

qrowth of Circaea lutetiaim plants was studied in various locations in or near a mixed deciduous woodland. Morphological changes resulting from increased shading included increases in leaf area ratio, specific leaf area and specific water content. Parallel measurements with a spectroradi-ometer confirmed that shading involved a reduction in both light fluence rate and light quality (e.g. red/far-red ratio). Phytochrome P_fr/P status was also studied by spectrophotometric measurements on Avena seedling test material and by biological (Lactuca seed germination) assay. Attempts were made to demonstrate phytochrome controlled changes in plant morphology under controlled environment, using both end-of-day far-red treatment and far-red enrichment of the main light period. Effects of natural shading were most clearly simulated by varying light fluence rate while maintaining a constant but high red/far-red ratio     

NO3^—,NO2^—同时测定的研究进展

综述了近年来农业、环境科学和食品科学中NO_3~-、NO_2~-同时测定方法的研究进展。     

BLUE LIGHT RESPONSES IN NITRATE REDUCTASE MUTANTS OF NEUROSPORA CRASSA

Abstract— The role of nitrate reductase in the blue light responses of photosuppression and phase shifting of circadian conidiation was studied in Neurospora crassa. The photoresponses, as assayed in three nitrate reductase mutants (nit-1,nit–2 and nit-3), showed no significant differences as compared to the responses in a strain which could utilize nitrate. In addition, the responses occur on a medium which (i) represses nitrate reductase activity due to the presence of ammonium ion and arginine or (ii) results in the production of an inactive enzyme due to the presence of tungsten. Nitrate reductase appears to be of no or secondary importance as a photoreceptor in the responses studied.     

镉还原法测定血清NO稳定代谢产物NO3-/NO2-

建立了血清NO的间接测定方法。采用正交设计法[L9(3^4)]观察不同还原剂及其用量,原时间和温度对NO3^-还原率的影响。最佳还原条件为400mg镀铜镉粒室温还原120min,还原率达97%以上。方法简便易行,不需昂贵设备,准确度较高,适合一般实验室用于各种生物医学实验中NO的间接测定。     

PHOTOACTIVATION OF NITRATE REDUCTASE FROM NEUROSPORA CRASSA

Abstract— The photoactivation of nitrate reductase from Neurospora crassa was studied in partially purified extracts. The inactive enzyme [inactivated by reduction in the presence of potassium cyanide] could be reactivated by chemical oxidation with ferricyanide or by irradiation with blue light. The enzyme contains a short electron transfer chain consisting of flavin adenine dinucleotide, cytochrome b ₅₅₇ and molybdenum which normally transfers electrons from reduced pyridine nucleotide to nitrate. This overall activity, which was negligible in the inactive enzyme, was restored to approximately 70% of the ferricyanide control by irradiation. However, nitrate reduction using reduced methylviologen as reducing power, which was also negligible in the inactive enzyme, was photoactivated to 100%. The diaphorase activity of the enzyme mediated by the flavin adenine dinucleotide, which was fully active in the inactivated enzyme, was inhibited approximately 30% by the irradiation treatment. The action spectrum for photoactivation showed that a flavin was the photoreceptor chromophore. Photoactivation occurs only in the presence of oxygen.     

INTERACTIONS OF COBALT(II) TETRASULFOPHTHALOCYANINE WITH NITRITE IN THE PRESENCE OF NITRATE AND PERCHLORATE IONS

Abstract

Spectroscopic changes observed on addition of nitrite to solutions of cobalt(II) tetra-sulfophthalocyanine ([Co(II)TSPc]^4-) in the presence of N^? ₃ or ClO^? ₄ are reported. There is spectroscopic evidence for the oxidation of [Co(II)TSPc]^4- to a [Co(III)TSPc]^3- species in the presence of nitrite ions. Equilibrium and kinetic studies for the interaction between [Co(II)TSPc]^4- and NO^? ₂ are reported. The rate was found to be first order in both [Co(II)TSPc]^4- and NO^? ₂. The rate constant for the forward reaction, k _f=1.6 × 10^?4 dm³mol^?1s^?1 was determined at 20°C for the interaction between nitrite ions and [Co(II)TSPc]^4- in the presence of NO₃ ^? or ClO₄ ^? ions.     

PHYTOCHROME INTERMEDIATES IN VIVO-I. EFFECTS OF TEMPERATURE, LIGHT INTENSITY, WAVELENGTH AND OXYGEN ON INTERMEDIATE ACCUMULATION

Abstract— Accumulation of weakly absorbing phytochrome intermediates has been demonstrated in Pisum epicotyl tissue under conditions of pigment cycling using a quasi-continuous measuring spectrophotometer. An action spectrum shows 690–700 nm to be the most efficient wavelength range in this process. Difference spectra for the decay of intermediates maintained by 690 nm light show that, if the experiment is done at 0°C, only P_fr is formed. At – 11°C, intermediates decaying to P_r can also be observed. At – 20°C, P_r is produced as well as a pigment with peak absorption at 710nm. Kinetic analysis of intermediate decay at – 11°C reveals that at least two intermediates are maintained by 690 nm light. The level of intermediate maintained by incandescent light at 0°C was 25% higher in air than in nitrogen.     

叔胺中的取代基团对其促进烯类聚合活性的影响

<正> 过硫酸盐和水溶性脂肪胺可以组成引发体系用于烯类聚合反应。脂肪胺的促进聚合活性随其结构不同而异。为了研究清楚脂肪胺促进聚合活性与结构的关系,本文合成了几种甲基取代的脂肪叔胺,分别与过硫酸盐组成引发体系用于烯类聚合反应。研究结果表明,甲基取代基团的效果较好。     

PHOTOSYNTHETIC NITRITE REDUCTION BY DITHIOERYTHRITOL AND THE EFFECT OF NITRITE ON ELECTRON TRANSPORT IN ISOLATED CHLOROPLASTS

Abstract. Photosynthetic reduction of nitrite to ammonia with type C chloroplasts from the heterocont alga Bumilleriopsis filiformis was investigated using 3,6-diaminodurene/ascorbate and 3,6-diaminodurene/dithioerythritol (DAD/DTE) as electron donor couple. Rates approach 6–10 μmol NO^-₂ reduced/mg chlorophyll/h and are steady for up to 30 min. The presence of oxygen or NADP⁺ only slightly diminished the rates of nitrite reduction obtained with DAD/DTE. Illuminated chloroplasts reduce oxygen in the presence of DAD/DTE at 135 μmol/mg chlorophyll/h without acceptor supplied. Photosynthetic oxygen uptake by this system in the presence of ferredoxin and NO^-₂, however, is inhibited to 42% by nitrite reductase with concurrent nitrite reduction. NO^-₃ and NO^-₂ have no effect on photosystem I-mediated NADP⁺ reduction, NO^-₂ (10 m M ) inhibits ferricyanide-mediated oxygen evolution to 72%. Also photosystem II reactions assayed e.g. with silicomolybdate are inhibited significantly by NO^-₂ (1 m M ), but only slightly by NO^-₃. Nitrite reductase is inhibited by p -chloromercuribenzoate ( p CMB), and this inhibition is prevented by DTE. Results suggest that photosynthetic nitrite reduction can cope with low concentrations of either compound, provided relevant thiol groups are protected.     

EFFECTS OF N-PHENYLIMIDE S-23142 AND N-METHYL MESOPORPHYRIN IX ON THE SYNTHESIS OF THE PHYTOCHROME CHROMOPHORE IN PEA EMBRYONIC AXES

Abstract Treatment of imbibed embryonic axes taken from seeds of Pisum sativum with N-phenylimide S-23142, a herbicide that has been suggested to inhibit protoporphyrin synthesis, or with N -methyl mesoporphyrin IX, an inhibitor of the iron chelatase for heme, resulted in a significant decrease in the amount of spectrophotometrically detectable phytochromc in the axes in both cases. However, the amount of immunochemically detectable phytochrome was not affected by either treatment. If S-23142 inhibits the synthesis of protoporphyrin IX in pea, it appears that the conversion of protoporphyrinogen IX to protoporphyrin IX is involved in the biosynthesis of the phytochrome chromophore. The conversion of protoporphyrin IX to heme (Fe-protoporpbyrin) also appears to be a step in the biosynthesis of the chromophore, since N -methyl mesoporphyrin IX prevented the synthesis of spectrophotometrically detectable phytochrome but did not affect the magnesium chelatase activity required for the synthesis of chlorophyll in pea embryonic axes. The results suggest that protoporphyrinogen IX, protoporphyrin IX and heme are intermediates in the biogenesis of the phytochromc chromophore. The pathway to phytochromobilin might become fixed after protoporphyrin IX, being directed toward the Fe branch for heme rather than to the Mg branch for chlorophyll.     

双流路互不干扰流动注射在线同时测定水中硝酸盐氮和亚硝酸盐氮

将镀铜镉柱应用于流动注射(FIA)实现了水中硝酸盐氮和亚硝酸盐氮的同时测定。在磷酸介质中,亚硝酸盐与磺胺重氮化,再与N-(1-萘基)-乙二胺盐酸盐偶合,形成玫瑰红色的偶氮染料,在540nm的波长处检测。硝酸盐被镉柱在线还原为亚硝酸盐后同法测定。硝酸盐和亚硝酸盐的测定范围分别为0.1～35mg/L、0～1200μg/L,检出限分别为45.6μg/L和4.8μg/L,RSD均低于1.05%(n=11),测定频率为10样/小时。实际水样中硝酸盐和亚硝酸盐的测定取得了满意的效果,加标回收率均在89.2%～109.0%之间,该仪器适合于现场即时监测。     

THE EFFECT OF LEVULINIC ACID ON THE LIGHT INDUCED DEVELOPMENT OF PHOTOSYSTEM I AND II ACTIVITIES IN GREENING MAIZE LEAVES*

Photosystem I and Photosystem II activities were measured in chloroplasts isolated after 0–20 h illumination from etiolated maize leaves in which chlorophyll synthesis was specifically inhibited by levulinic acid. In control leaves not treated with levulinic acid, Photosystem I activity/chlorophyll developed rapidly during the first 2h in light, then fell off, and reached a constant level after 6h of illumination. In levulinic acid treated leaves, in which chlorophyll accumulation was inhibited up to 60%, a similar initial rise in Photosystem I activity was observed. However, the decrease in activity was much slower and continued for at least 20 h. The development of Photosystem I activity calculated on a leaf fresh weight basis was similar for control leaves or leaves treated with levulinic acid. This indicates that development of Photosystem I activity may not be related to chlorophyll accumulation during greening. Photosystem II activity/chlorophyll in leaves treated with or without levulinic acid increased similarly during the first 6h and then remained constant. Activity of Photosystem II per leaf fresh weight increased linearly, after the first h, for 20 h in the control leaves; in levulinic acid treated leaves this development was reduced by about 60%. Thus, development of Photosystem II activity can be related to chlorophyll accumulation. SDS gel electrophoresis of plastid membranes from control leaves illuminated for 12 h showed the presence of chlorophyll-protein complex I as well as Chl-protein 11; in the case of levulinic acid treated leaves only Chl-protein complex I was detectable, while Chl-protein complex II was markedly reduced.     

EFFECT OF PHYTOCHROME ON THE BIOSYNTHESIS OF ACYCLIC AND CYCLIC CAROTENOIDS IN HIGHER PLANTS

Radish plants were grown in the presence of three different herbicides that interfere with the formation of the normal range of cyclic carotenoids, leading to an accumulation of acyclic biosynthetic intermediates, mainly phytoene (SAN 6706 and amitrole) and zeta-carotene (3852). Plants were then irradiated by four different light programs in order to gain more insight into the first steps of carotenoid biosynthesis and their control by light and phytochrome. In all cases, herbicide-treated and control, carotenoid biosynthesis was greatly enhanced by red light consistent with an effect of phytochrome on the early steps of the pathway. However, similar enhancement was also obtained after treatment with far-red light. Indeed with SAN 6706-treated plants synthesis of phytoene was stimulated to a much greater extent by far-red light given alone, than by red light. The involvement of phytochrome in the regulation of carotenoid biosynthesis appears not to be as simple as previously supposed.     

LETTUCE SEED GERMINATION: EFFECTS OF HIGH TEMPERATURE AND OF REPEATED FAR-RED TREATMENT IN RELATION TO PHYTOCHROME

Abstract— At 37°C the active form of phytochrome in lettuce seed cannot function to promote subsequent germination. This effect of high temperature is distinct from thermal acceleration of dark reversion from the active form of phytochrome to the inactive form, and may be due to reversible denaturation of phytochrome.
Repeated brief irradiations with far-red light inhibit subsequent germination in the whole seed, whereas a similar irradiation regime results in a strong enhancement of the development of growth potential (ability to expand against an externally-imposed osmotic restraint) in the excised axial portion of the seed. A possible explanation for these two opposing results, in volving two different pigment systems with effective loci in different parts of the seed, is suggested.     

紫外检测-离子色谱法测定食品中的硝酸盐和亚硝酸盐

利用紫外检测－离子色谱法测定食品中的亚硝酸盐和硝酸盐，NO2－N、NO3^-－N的检出限分别为4和10μg/L；标准曲线方程分别为：A＝43.194c-0.0332(r=0.9998)和A=38.534c-0.3132(r=0.9997)。NO2^-－N和NO3^-－N的回收率分别为89％和92％。该方法适用于测定肉制品、奶粉、蔬菜中的硝酸盐和亚硝酸盐。     

IRREVERSIBLE PHOTO IN ACTIVATION OF NITRATE REDUCTASE DURING THE FLAVIN-SENSITIZED PHOTOCHEMICAL ASSAY OF ITS CATALYTIC ACTIVITY

Abstract— The classic photochemical system in which flavin and EDTA act as photosensitizer and electron donor, respectively, has been employed for assaying in vitro the catalytic activity of Ankistrodesmus braunii nitrate reductase. When the photochemical assay is performed under air, but not in anaerobiosis, a considerable decay in the nitrite photoproduction rate is observed after 10–15 min. which is accompanied by a decrease of reduced methyl viologen-nitrate reductase activity. The first enzyme activity, i.e. diaphorase is photoinactivated even more quickly and does not present any initial lag phase. Some oxygen species (superoxide and/or hydrogen peroxide) are probably involved in the photoinactivating mechanism, which appears to be non-specific and irreversible.
The use of flavin/EDTA photosystems is therefore, very practical for the in vitro assay of nitrate reductase activity, although anaerobic conditions are required for optimum results. Since inactivation of the terminal activity is, however, relatively slow, anaerobiosis would not be required for assay times shorter than 10 min.