Replication of chloroplast, mitochondrial and nuclear DNA during growth of unirradiated and UVB-irradiated Arabidopsis leaves

Replication of Arabidopsis nuclear, mitochondrial and chloroplast DNA (ncDNA, mtDNA, cpDNA) was assayed by measuring respective changes in copies per leaf, employing quantitative PCR (QPCR) analysis with genome-specific primer pairs. All three genomes showed parallel increases during growth of cotyledons and 5th leaves in planta, maintaining approximately 13 mtDNA copies and 280 cpDNA copies per haploid nuclear genome. Detached 5th leaves, which showed good growth and DNA replication on agar plates, were irradiated at (DNA-effective) UV-B fluences of 1.3-5.0 kJ m-2 and incubated under blue (photorepair-active) plus gold light or gold light only. Under blue light, replication of all genomes after all UV fluences was approximately as efficient as replication in unirradiated leaves. UV-irradiated leaves showed little growth under gold light only; 5 kJ m-2 stopped replication of all three genomes, 2.5 kJ m-2 stopped only cpDNA replication, and 1.3 kJ m-2 only delayed cpDNA replication. Immunoassays showed that 5 kJ m-2 induced about 1.2 cyclobutane pyrimidine dimers and 0.1 [6-4]photoproducts per kbp of bulk DNA, and that both photoproducts were completely removed during 2-3 days under blue light, suggesting efficient photorepair of at least ncDNA and cpDNA. The evidence for efficient photorepair of organellar DNA contrasts with previous studies of irradiated 5-day-old seedlings, and with the apparent absence of Arabidopsis photolyases bearing transit peptides.     

深圳福田无瓣海桑-海桑林能量的研究

在研究生物量、生产力的基础上,对深圳福田无瓣海桑-海桑林中2种红树植物海桑和无瓣海桑各组分的干重热值、林分能量现存量、年能量净固定量进行了研究．结果表明,各组分样品干重热值有一定的差异,树叶干重热值最高,纫根干重热值最低;海桑各组分样品干重热值比无瓣海桑相应组分稍高．林分能量现存量(1999年10月)为84774．72kJ·m^2,其中无瓣海桑种群能量现存量为54693．26kJ·m^-2,占林分总的64．54％,海桑种群能量现存量为30051．46kJ·m^-2,占林分总量的35．46％．林分凋落物的能量归还量(1999年)为24549．54kJ·m^-2·年^-1,其中无瓣海桑种群的能量归还量为17223．99kJ·m^-2·年^-1,占总林分的70．16％,海桑种群的能量归还量为7325．55kJ·m^-2·年^-1,占总林分的29．84％．林分能量净固定量为50391．4kJ·m^-2·年^-1,其中无瓣海桑种群和海桑种群的能量净固定量为分别为31778kJ·m^-2·年^-1和18613．4kJ·m^-2·年^-1．     

Enhanced transformation of human cells by UV-irradiated pSV2 plasmids.

Irradiating the plasmid pSV2-gpt with UV (254 nm) doses up to 200 J m-2 caused a dose-dependent increase in the yield of Gpt+ transformants when the plasmid was introduced into human cells by calcium phosphate coprecipitation. UV doses greater than 1 kJ m-2 were required to reduce the efficiency of transformation below that obtained with unirradiated DNA.     

多蒴灰藓对强紫外线照射的生理响应

将多蒴灰藓(Hypnum fertile)置于紫外辐射下照光3周,研究了紫外辐射对多蒴灰藓的损害及其生理响应。结果表明： 与对照(自然环境)相比,多蒴灰藓的叶绿素和类胡萝卜素含量均随紫外辐射时间的延长而减少,MDA含量却明显增加,SOD、POD和CAT活性也相应增加;增加紫外辐射量会引起多蒴灰藓的氧化胁迫,其能通过增加抗氧化酶的活性来减轻这种胁迫。     

香港山坡地草本、灌木群落的植物能量生产

利用收获法和植物热值分析,在研究香港桃金娘灌木群落、芒萁群落和鸭嘴草+野古草+金茅草地植物的生物量和净生产量的基础上,探讨群落各组分的干重热值以及植物能量现存量、净固定量和现存净增量.结果表明,芒萁具有较高的热值,而禾草植物的干重热值较低.草地、芒萁、灌木群落植物的能量现存量分别为18683、38436和65632kJ·m^-2;能量净固定量为13286、20354和18784kJ·m^-2·a^-1;能量现存净增量为3437、9626和6695kJ·m^-2·a^-1.与地带性植被南亚热带常绿阔叶林相比,草地、芒萁、灌木群落的能量现存量、能量净固定量和能量现存净增量都较低.刈割实验也表明,随着人类干扰活动强度加大,植物能量净固定量明显下降.     

Nitroblue tetrazolium test in patients with breast cancer undergoing mastectomy and radiotherapy

The reduction of nitrotetrazolium blue with stimulated and unstimulated granulocytes was performed in 40 patients with breast cancer. Blood was collected from peripheral vein before surgical intervention, during surgery from vein draining of tumor, two weeks after surgery and three months after surgery when radiotherapy was finished. In parallel experiments the NBT test was made in the peripheral blood of 20 healthy individuals. We have observed decreased reduction of nitrotetrazolium blue in stimulated granulocytes, which may indicate that granulocytes from these patients are unable for efficient stimulation. No evident effect concerning the advancement of disease and applied therapy could be found. The importance of determining the NBT test in cancer patients is briefly discussed.     

Granulocyte metabolism in workers at a coke-processing plant]

Acid phosphatase activity examinations and nitrotetrazolium blue reduction test after latex stimulation in peripheral blood neutrophils were performed in the group of 32 coking plant workers. Reference group consisted of 150 men not exposed to any toxic substances. Neutrophils of coking plant workers, comparing with the reference group, revealed decreased activity of acid phosphatase and impaired reduction of nitrotetrazolium blue after latex stimulation. The results suggest the possibility of toxic influence of coking plant environment on the lysosomal enzymes and oxygen-dependent metabolism of neutrophils what subsequently may diminish bactericidal powers.     

Study on Energy of Castanopsis eyrei Community in Wuyi Mountains

Based on the measurement of biomass and productivity, the caloric value of plant samples, the standing crop of energy, net energy production and energy conversing efficiency of Castanopsis eyrei community were determined. There were some differences in caloric values among the fractions of C. eyrei community being highest in that of bark and lowest in that of the microroots. The standing crop of energy in C. eyrei community was 780584.1 kJ ·m-2, in which the standing crop of energy accumulated in the aboveground biomass was 678913.8 kJ · m-2, accounting 86. 98% of the total; that of underground was 101670.3 kJ · m-2, i. e. 13.02%. Net energy production was 26856.2 kJ · m-2 · a-1 for this community in 1992. To the photosynthetic active radiation on the stand, the energy conversing efficiency was 1. 296%.     

亚热带季雨林植物罗伞气体交换对光质的反应

亚热带季雨林林下阴生植物罗伞(Ardisia quinquegona)叶片的气体交换速率(PN.μmol.m~(-2),s~(-1))随光强(PFD,μmol,m~(-2),s~(-1))增高而增大。在光强低于80μmol,m~(-2),s~(-1),PN=29.21PFD×10~(-3)+0.36。在光强150μmol,m~(-2),s~(-1)对出现气体交换的光饱和现象。在低光强下,气孔传导率(G,m mol,m~(-2),s~(-1)与光强(m mol,m~(-2),s~(-1)的关系为G=265.6 PFD+4.6。在低光强下。开阔地的阳生灌木桃金娘(Rhodmyrtus tomentosa)的气体交换速率和气孔传导率与光强关系曲线的直线部分斜率皆较罗伞的低,在红光上,罗伞叶片气体交换速率(μmol,m~(-2),s~(-1)与光强(μmol,m~(-2),s~(-1)的关系为PN=32.4 PFD×10~(-3)-0.04。气孔传导率(m mol,m~(-2),s~(-1)与光强(m mol,m~(-2),s~(-1)的关系为G=339.08 PFD+7.37。同时气体交换速率的饱和红光光强亦较白光的高。在蓝光光强低时,气体交换速率(μmol,m~(-2),s~(-1))与光强(μmol,m~(-2),s~(-1))的关系为PN=13.54 PFD×10~(-3)—0.17,而气孔传导率(m mol,m~(-2),s~(-1))与光强(mμmol,m~(-2),s~(-1))的关系为G=80.5 PFD+4.35。在低的蓝光下,体交换速率和气孔传导率与光强关系曲线的直线部分斜率显著较在白光和红光下的低。罗伞叶片气体交换对红光的反应敏感。     

Effects of FLONLIZER, ultraviolet sterilizer, on Legionella species inhabiting cooling tower water

Legionella pneumophila in sterile distilled water was not detected after ultraviolet irradiation by FLONLIZER, a new-type sterilizer, at a flow rate of 82.5 to 364.8 liters/hr. When irradiated by FLONLIZER at a flow rate of under 324.0 liters/hr, no viable cells of legionellae, other heterotrophic bacteria and bacterivorous protozoa were detected in the cooling tower water, which was found to contain L. pneumophila. No viable cells of L. pneumophila and L. bozemanii suspended in sterile distilled water were detected after the irradiation with UV-doses of over 6.16 X 10(3) micro W.sec/cm2. At the irradiation of low UV-doses under 1.06 X 10(4) micro W.sec/cm2, the viable count of legionellae recuperated by photoreactivation from UV-damage increased with the exposure time under a white fluorescent lamp. However, in the samples irradiated with UV-doses of over 3.52 X 10(4) micro W.sec/cm2, equal to the FLONLIZER, legionellae did not recuperate even after 18 hr illumination with a white fluorescent lamp. FLONLIZER is thus expected to act as a sterilizer which can control the legionellae inhabiting cooling tower systems placed in outdoor space.     

Selection of succinic dehydrogenase mutants of Neurospora crassa.

A method is described which permits the selection of mutants of Neurospora crassa that are deficient in succinic dehydrogenase activity. The method relies on the observation that succinic dehydrogenase-deficient strains fail to reduce the dye nitrotetrazolium blue when overlaid with the dye in the presence of succinate and phenazine methosulfate. Wild-type colonies reduced the dye and turned blue, whereas mutant colonies remained colorless. In this communication we present studies of a mutant, SDH-1, isolated by this method. The mutant had 18% of the succinic dehydrogenase activity of the parent strain used in the mutation experiments as determined from the ratio of Vmax activities obtained from Lineweaver-Burk plots. The SDH-1 mutant segregated in a Mendelian manner when back-crossed to its parent strain. Succinate oxidase activity in SDH-1 was low and was markedly inhibited by adenosine 5'-diphosphate. The succinate oxidase activity of the parent strain was high and was not affected by the presence of adenosine 5'-diphosphate.     

Effect of specimen size on work-of-fracture measurements

It has been suggested that work-of-fracture, which quantifies the ability of a material to resist fracture, is dependent on specimen size. This experiment compared work-of-fracture, calculated as energy per unit area, for different specimen sizes of Plexiglas, bovine tibial bone and aluminum. Three different geometrically similar cross sections were tested for each material for a total of 54 specimens. Work-of-fracture was measured by loading a notched beam (triangular cross section) in three-point bending at a constant deformation rate. The energy necessary to cause fracture was measured from a load-deformation curve. Specimen fracture area was determined using macrophotography. Atomic absorption spectrophotometry was used to determine weight percent calcium of bone specimens and quantitative light microscopy was used to determine fractional void area. Analysis of variance showed no effect of specimen size on work-of-fracture for aluminum or Plexiglas specimens (p greater than 0.05). A significant difference was found, however, between the large (area = 11.7 +/- 1.9 mm2) and small (area = 3.48 +/- 0.68 mm2) bone specimens and between the medium (area = 5.89 +/- 0.69 mm2) and small (area = 3.48 +/- 0.68 mm2) bone specimens. No correlation was found between work-of-fracture and either calcium content (r2 = 0.128) or fractional void area (r2 = 0.0713). The mean work-of-fracture values found are as follows: aluminum, 59.8 +/- 13.7 kJ m-2; Plexiglas, 0.620 +/- 0.074 kJ m-2; bone (area 5.89 +/- 0.69 mm2-11.7 +/- 1.9 mm2), 9.72 +/- 1.93 kJ m-2 and bone (area 3.48 +/- 0.68 mm2), 5.48 +/- 1.79 kJ m-2.     

Blue light and phytochrome-mediated stomatal opening in the npq1 and phot1 phot2 mutants of Arabidopsis

Recent studies have shown that blue light-specific stomatal opening is reversed by green light and that far-red light can be used to probe phytochrome-dependent stomatal movements. Here, blue-green reversibility and far-red light were used to probe the stomatal responses of the npq1 mutant and the phot1 phot2 double mutant of Arabidopsis. In plants grown at 50 micromol m-2 s-1, red light (photosynthetic)-mediated opening in isolated stomata from wild type (WT) and both mutants saturated at 100 micromol m-2 s-1. Higher fluence rates caused stomatal closing, most likely due to photo-inhibition. Blue light-specific opening, probed by adding blue light (10 micromol m-2 s-1) to a 100 micromol m-2 s-1 red background, was found in WT, but not in npq1 or phot1 phot2 double mutant stomata. Under 50 micromol m-2 s-1 red light, 10 micromol m-2 s-1 blue light opened stomata in both WT and npq1 mutant stomata but not in the phot1 phot2 double mutant. In npq1, blue light-stimulated opening was reversed by far-red but not green light, indicating that npq1 has a phytochrome-mediated response and lacks a blue light-specific response. Stomata of the phot1 phot2 double mutant opened in response to 20 to 50 micromol m-2 s-1 blue light. This opening was green light reversible and far-red light insensitive, indicating that stomata of the phot1 phot2 double mutant have a detectable blue light-specific response.     

Photoacclimation of Prochlorococcus sp. (Prochlorophyta) Strains Isolated from the North Atlantic and the Mediterranean Sea

Two Atlantic (SARG and NATL1) strains and one Mediterranean (MED) strain of Prochlorococcus sp., a recently discovered marine, free-living prochlorophyte, were grown over a range of "white" irradiances (lg) and under low blue light to examine their photoacclimation capacity. All three strains contained divinyl (DV) chlorophylls (Chl) a and b, both distinguishable from "normal" Chls by their red-shifted blue absorption maximum, a Chl c-like pigment at low concentration, zeaxanthin, and [alpha]-carotene. The presence of two phaeophytin b peaks in acidified extracts from both Atlantic strains grown at high lg suggests that these strains also had a normal Chl b-like pigment. In these strains, the total Chl b to DV-Chl a molar ratio decreased from about 1 at 7.5 [mu]mol quanta m-2 s-1 to 0.4 to 0.5 at 133 [mu]mol quanta m-2 s-1. In contrast, the MED strain always had a low DV-Chl b to DV-Chl a molar ratio, ranging between 0.13 at low lg and 0.08 at high lg. The discrepancies between the Atlantic and MED strains could result from differences either in the number of light-harvesting complexes (LHC) II per photosystem II or in the Chl b-binding capacity of the apoproteins constituting LHC II. Photosynthesis was saturated at approximately 5 fg C(fg Chl)-1 h-1 or 6 fg C cell-1 h-1, and growth was saturated at approximately 0.45 d-1 for both MED and SARG strains at 18[deg]C, but saturating irradiances differed between strains. Atlantic strains exhibited increased light-saturated rates and quantum yield for carbon fixation under blue light.     

Driving Forces for Bicarbonate Transport in the Cyanobacterium Synechococcus R-2 (PCC 7942)

Air-grown Synechococcus R-2 (PCC 7942) cultures grown in BG-11 medium are very alkaline (outside pH is 10.0) and use HCO3- as their inorganic carbon source. The cells showed a dependence on Na+ for photosynthesis, but low Na+ conditions (1 mol m-3) were sufficient to support saturating photosynthesis. The intracellular dissolved inorganic carbon in the light was greater than 20 mol m-3 in both low-Na+ conditions and in BG-11 medium containing the usual [Na+] (24 mol m-3, designated high-Na+ conditions). The electrochemical potential for HCO3- in the light was in excess of 25 kJ mol-1, even in high-Na+ conditions. The Na+-motive force was greater than -12 kJ mol-1 under both Na+ conditions. On thermodynamic grounds, an Na+-driven co-port process would need to have a stoichiometry of 2 or greater ([greater than or equal to]2Na+ in/HCO3-1 in), but we show that Na+ or K+ fluxes cannot be linked to HCO3- transport. Na+ and K+ fluxes were unaffected by the presence or absence of dissolved inorganic carbon. In low-Na+ conditions, Na+ fluxes are too low to support the observed net 14C-carbon fixation rate. Active transport of HCO3- hyperpolarizes (not depolarizes) the membrane potential.     

Analysis of guanase by agarose gel electrophoresis and activity staining

A method was developed to separate guanase by agarose gel electrophoresis and to detect its activity by staining of the bands with a mixture of the enzymes xanthine oxidase, catalase, and aldehyde dehydrogenase, the coenzyme NADP+, and a substrate of guanine, ethanol, phenazine methosulfate, nitrotetrazolium blue, and KCN in Tris-(hydroxymethyl)methylamine buffer (pH 8.0). Serum samples showed bands 1 (faster moving) and 2 corresponding to the positions of albumin and alpha 2-globulin, respectively, found by serum protein staining. The same bands were detected with guanase from human liver and kidney, although band 2 from the latter samples was not as distinct as that from the liver samples.     

Influence of high light and UV-B radiation on photosynthesis and D1 turnover in atrazine-tolerant and -sensitive cultivars of Brassica napus

An atrazine-tolerant mutant and an atrazine-sensitive cultivar of Brassica napus L. were grown under visible radiation (400 mumol m-2 s-1, photosynthetically active radiation, PAR) and then subjected to treatment conditions. These included short-term high PAR (1600 mumol m-2 s-1) which was given for 4 h either alone or in combination with an enhanced level of UV-BBE radiation (4.6 kJ m-2 h-1 biologically effective UV-B, 280-320 nm). Recovery from the radiation treatment was studied for 4 h under the light conditions for growth. Since it is known that the atrazine-tolerant mutant is susceptible to photoinhibition, one of the aims of the present study was to determine the effects of a supplemental, enhanced level of UV-B radiation with regard to the mutant. The results indicate an additive effect of UV-B radiation on Fv/Fm, photochemical yield and photosynthetic oxygen evolution during both exposure and recovery, and also a higher susceptibility of the mutant to photoinhibitory PAR conditions alone and in combination with UV-B, which may have implications in a changing environment. Both cultivars also showed a higher D1 turnover during the radiation stress than during recovery, as shown by immunoblotting and 35S-methionine incorporation measurements.     

Specificity and Photomorphogenic Nature of Ultraviolet-B-Induced Cotyledon Curling in Brassica napus L

Three general classes of photomorphogenic photoreceptors have been characterized in higher plants: phytochrome, a blue light/ultraviolet (UV)-A photoreceptor(s), and a UV-B sensory system(s). Although a great deal is known about phytochrome and the blue light/UV-A photoreceptor(s), little is known about UV-B detection processes. One reason for this is the lack of readily quantifiable morphogenic responses that are specifically induced by UV-B radiation. We have discovered a response to UV-B, upward curling of Brassica napus L. cotyledons, that may be useful for probing the mechanism of UV-B photoreception. The process was initially observed when B. napus seeds were germinated under visible light plus UV-B radiation, but did not occur under visible light alone or visible light plus UV-A. When 5-d-old seedlings grown in visible light were given relatively short exposures of UV-B (100 min of 5.5 [mu]mol m-2 s-1), the curling response was also observed. Development of curling was separated from the application of this UV-B pulse by a 14-h latent period. Pulses of red light, blue light, farred light, and UV-A (100 min of 5.5 [mu]mol m-2 s-1) did not induce curling, indicating UV-B specificity Additionally, these other spectral regions did not reverse or enhance the UV-B-triggered response. The degree of curling showed a log-linear dependence on UV-B fluence (6-40 mmol m-2) and reciprocity with respect to length of exposure and fluence rate. The data indicate that curling is photomorphogenic in nature and may be triggered by a single photoreceptor species.     

Effects of ultraviolet-B radiation on cotton (Gossypium hirsutum L.) morphology and anatomy

Cotton (Gossypium hirsutum L.) crop, cultivated between 40 degrees N and 40 degrees S, is currently experiencing 2-11 kJ m-2 d-1 of UV-B radiation. This is predicted to increase in the near future. An experiment was conducted to study the effect of enhanced UV-B radiation on vegetative and reproductive morphology and leaf anatomy of cotton in sunlit, controlled environment chambers. From emergence to harvest, cotton plants were exposed to 0, 8 or 16 kJ m-2 d-1 of UV-B in a square wave approach for 8 h from 0800 to 1600 h. Changes in plant height, internode and branch length, mainstem node number, leaf area, length and area of petals and bracts, and anther number per flower were recorded. Epidermal cell and stomatal density, stomatal index, leaf thickness, and epidermal, palisade and mesophyll tissue thickness were also measured. Initial chlorotic symptoms on leaves turned into necrotic patches on continued exposure to enhanced UV-B. Exposure to high UV-B reduced both vegetative and reproductive parameters and resulted in a smaller canopy indicating sensitivity of cotton to UV-B radiation. Enhanced UV-B radiation increased epicuticular wax content on adaxial leaf surfaces, and stomatal index on both adaxial and abaxial leaf surfaces. Leaf thickness was reduced following exposure to UV-B owing to a decrease in thickness of both the palisade and mesophyll tissue, while the epidermal thickness remained unchanged. The vegetative parameters studied were affected only by high levels of UV-B (16 kJ m-2 d-1), whereas the reproductive parameters were reduced at both ambient (8 kJ m-2 d-1) and high UV-B levels. The study shows that cotton plants are sensitive to UV-B at both the whole plant and anatomical level.     

Antiradical and antioxidant effect of arginine and its action on lipid peroxidation in hypoxia

Arginine (0.5 and 1 mu mol) decreased by 14-17% rates of superoxide anion formation in two systems: HADH-phenazine methosulfate and hydroxylamine autooxidation with nitrotetrazolium blue. These concentrations of arginine decreased by 40-50% formation of diene conjugates and Schiff bases in plasma when lipid peroxidation initiated by iron -ascorbate. Arginine administration before hypoxia decreased lipid peroxidation rate in plasma and liver microsomal membranes of rats.