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1.
Field studies of respiration in stream insects are few in comparison with laboratory studies. To evaluate the influence of temperature and oxygen along altitudinal gradients we measured the respiration rate of fully acclimatized larval Trichoptera, Plecoptera and Ephemeroptera under similar field conditions in streams from 400 to 3800 m above sea level in tropical Ecuador. Mean active respiration rates of the animals at 3800 m were approximately half of those at 400 m. Trichoptera showed a slightly larger difference in respiration with altitude than Ephemeroptera. Comparative respiration measurements at 100 and 50% oxygen saturation indicated that highland animals reduced their oxygen uptake more than their counterparts in the lowland when oxygen availability decreased. The temperature response of respiration calculated between the insect assemblages at different altitudes showed a mean assemblage Q10−value of 1.50. Trichopteran larvae had a slightly stronger temperature response (Q10 of 1.68) than ephemeropterans (Q10 of 1.30). These community Q10-values are considerably lower than the mean value of 2.36 found in single species in the laboratory. The weak community-wide response of respiration to temperature in tropical streams is probably due to full acclimatization of the component species to stable and narrow temperature ranges. Adaptations to the low oxygen availability at high altitude probably consist of a suite of genetic physiological and behavioural features. 相似文献
2.
全球陆地生态系统光合作用与呼吸作用的温度敏感性 总被引:3,自引:0,他引:3
基于全球647套通量数据,定量分析了全球尺度下生态系统光合作用和呼吸作用的温度敏感性(Q10)随纬度、气候和植被的分布规律。结果表明:在全球尺度下,光合作用和呼吸过程的温度敏感性(Q10,G和Q10,R)都随纬度的升高而增加,其中Q10,G和Q10,R的均值分别为3.99±0.21和2.28±0.074。除热带多树草原、常绿落叶林外,Q10,G均大于Q10,R值。不同植被类型的温度敏感性存在显著性差异,表现为:针叶林阔叶林;落叶林常绿林,其中生态系统的季节性变异是造成差异的主要原因。当植被类型和纬度区域共同影响Q10值时,植被类型对Q10值的总变异贡献更大。气候类型对Q10,G和Q10,R都有显著影响。在气候带上,干旱带的Q10,G最小,而冷温带的Q10,G最高。不同气候类型下(除温带草原气候外)的Q10,G都大于Q10,R。在极端条件下,温度可能不在是主导因素,而水分对温度敏感性的影响不可忽略,今后的研究需要更多的关注生态系统温度敏感性对水分变化的响应。 相似文献
3.
S. Berger J. Dirk L. VON Lindern D. Wolff D. Mergenhagen 《Plant biology (Stuttgart, Germany)》1992,105(5):382-386
The circadian rhythm in the oxygen production of 30 individual Acetabularia cells has been studied at different temperatures. The temperature induced period variation was continuously evaluated over the whole data record of each individual cell with an advanced spectral analysis technique. The observed circadian periods of O2 production displayed a well established region of temperature compensation between 25 °C and 30 °C with a Q10, value of 0.9, whereas between 15°C and 22°C a positive temperature coefficient was measured (Q10 at 22 °C 0.9, Q10 at 20°C 0.8, Q10at 17°C 0.7). 相似文献
4.
The effects of time after exposure to acetylene and of nodule excision were examined using a flow-through system. After a transient depression in the rate of acetylene reduction that began about 1.5 min after exposure to acetylene, the rate recovered to 98% of the initial maximum value after 40 min. After nodule excision the rate stabilized to 90% of the initial maximum value observed in the intact plant.Excised nodules, measured at 6-min intervals in a closed system, with frequent changes of the gas mixture, were used for the remaining experiments. Acetylene reduction by the nodules increased rapidly as temperature was increased between 6 and 26°C. Between 26 and 36°C there was relatively little effect of temperature on acetylene reduction.Nodules and cultures ofFrankia were compared with respect to the effect of temperature and pO2 (partial pressure of oxygen) on oxygen uptake. Cultures ofFrankia were grown on a nitrogen-free medium at either 0.3 kPa O2 (vesicles absent) or 20 kPa O2 (vesicles present). Oxygen uptake by nodules (vesicles absent) and by vesicle-containing cultures was strongly dependent on pO2 at values below 20 kPa. This suggests the presence of a barrier to oxygen diffusion. Oxygen uptake was dependent on temperature as well as on pO2, but the Q10 was much larger for the cultures than for the nodules. This suggests that vesicles or related structures are not the source of the diffusion barrier in Casuarina nodules. Respiration by cultures ofFrankia lacking vesicles became O2-saturated at low pO2 values. Thus these cultures did not have a significant diffusion barrier. From these results it is concluded that nodules ofCasuarina cunninghamiana have a barrier to oxygen diffusion supplied by the host tissue and not byFrankia. 相似文献
5.
采用红外气体分析法(IRGA)于2014年1—12月原位测定了北京市4个典型树种(国槐Sophora japonica,旱柳Salix matsudana,华北落叶松Larix principis-rupprechtii和侧柏Platycladus orientalis)在不同高度上的木质组织CO_2通量速率(E_(CO_2)),旨在比较不同树种间E_(CO_2)及其温度敏感性(Q_(10))的时间变化规律和铅锤分异特征。研究结果显示:(1)4个树种的E_(CO_2)均表现为单峰型季节变化规律,生长月份内的E_(CO_2)显著高于非生长月份,温度和枝干的径向生长是影响E_(CO_2)季节变化的主要因素;(2)E_(CO_2)对温度的敏感性在夏季月份明显降低,且出现明显的垂直分异:Q_(10)随测量高度的增加而增加,呈现出非连续的阶梯分布;(3)在日间尺度上,阔叶树种E_(CO_2)对温度的感性系数Q_(10)出现昼夜不对称现象,晚上Q_(10)明显升高。准确量化E_(CO_2)的时间变化规律和铅锤分异特征,细化不同时间尺度下E_(CO_2)对温度的响应特征,成为准确估算木质组织碳排放的前提条件。 相似文献
6.
JEROEN GILLABEL BEATRIZ CEBRIAN‐LOPEZ JOHAN SIX ROEL MERCKX 《Global Change Biology》2010,16(10):2789-2798
The ability to predict C cycle responses to temperature changes depends on the accurate representation of temperature sensitivity (Q10) of soil organic matter (SOM) decomposition in C models for different C pools and soil depths. Theoretically, Q10 of SOM decomposition is determined by SOM quality and availability (referred to here as SOM protection). Here, we focus on the role of SOM protection in attenuating the intrinsic, SOM quality dependent Q10. To assess the separate effects of SOM quality and protection, we incubated topsoil and subsoil samples characterized by differences in SOM protection under optimum moisture conditions at 25 °C and 35 °C. Although lower SOM quality in the subsoil should lead to a higher Q10 according to kinetic theory, we observed a much lower overall temperature response in subsoil compared with the topsoil. Q10 values determined for respired SOM fractions of decreasing lability within the topsoil increased from 1.9 for the most labile to 3.8 for the least labile respired SOM, whereas corresponding Q10 values for the subsoil did not show this trend (Q10 between 1.4 and 0.9). These results indicate the existence of a limiting factor that attenuates the intrinsic effect of SOM quality on Q10 in the subsoil. A parallel incubation experiment of 13C‐labeled plant material added to top‐ and subsoil showed that decomposition of an unprotected C substrate of equal quality responds similarly to temperature changes in top‐ and subsoil. This further confirms that the attenuating effect on Q10 in the subsoil originates from SOM protection rather than from microbial properties or other nutrient limitations. In conclusion, we found experimental evidence that SOM protection can attenuate the intrinsic Q10 of SOM decomposition. 相似文献
7.
We present a new soil respiration model, describe a formal model testing procedure, and compare our model with five alternative models using an extensive data set of observed soil respiration. Gas flux data from rangeland soils that included a large number of measurements at low temperatures were used to model soil CO2 emissions as a function of soil temperature and water content. Our arctangent temperature function predicts that Q10 values vary inversely with temperature and that CO2 fluxes are significant below 0 °C. Independent data representing a broad range of ecosystems and temperature values were used for model testing. The effects of plant phenology, differences in substrate availability among sites, and water limitation were accounted for so that the temperature equations could be fairly evaluated. Four of the six tested models did equally well at simulating the observed soil CO2 respiration rates. However, the arctangent variable Q10 model agreed closely with observed Q10 values over a wide range of temperatures (r2 = 0.94) and was superior to published variable Q10 equations using the Akaike information criterion (AIC). The arctangent temperature equation explained 16–85% of the observed intra-site variability in CO2 flux rates. Including a water stress factor yielded a stronger correlation than temperature alone only in the dryland soils. The observed change in Q10 with increasing temperature was the same for data sets that included only heterotrophic respiration and data sets that included both heterotrophic and autotrophic respiration. 相似文献
8.
The thermotropic properties of coenzymes Q10, Q9, Q8, and Q7 have been examined by differential scanning calorimetry and wide-angle X-ray diffraction. Typical scanning calorimetry cooling curves of coenzyme Q from the liquid state exhibit a single exothermic phase transition into a crystalline state at a temperature that decreases as the length of the polyisoprenoid side-chain substituent decreases. Upon subsequent heating, the molecules undergo a series of thermal events which precede the main crystalline-to-liquid endothermic phase transition. The temperature of these transitions increases with increasing chain length. The crystallization phase transition temperature depends markedly on the rate at which the sample is cooled and increases with decreasing scan rate; the temperature of the melting endotherm is not markedly affected by the scan rate. Detailed calorimetric studies of coenzyme Q10 indicate that two crystalline states are formed, one at relatively high cooling rates to low temperatures and the other when preparations are cooled slowly from the liquid state to relatively high temperatures. Heating the crystalline phase formed by rapid cooling causes its transformation into the phase observed by cooling slowly. X-ray diffraction analysis confirmed the existence of these two crystal phases in coenzymes Q9 and Q10 and the transformation from the rapidly crystallized form to the more ordered form associated with slower cooling rates. At body temperature (310 K) under equilibrium conditions coenzyme Q10 exists in an ordered crystalline phase; the implications of the thermotropic behavior of coenzyme Q10 on mitochondrial functionin vitro andin vivo are discussed. 相似文献
9.
Diversity of juvenile fish assemblages in the pelagic waters of Lebanon (eastern Mediterranean) 总被引:1,自引:0,他引:1
Oxygen consumption rates of nauplii of the brine shrimp Artemia franciscana Kellogg 1906 were determined over a range of salinities from 10 to 110 ppm, in temperatures from 0 to 30°C, using a multi-factorial
design. The oxygen micro-sensors employed have a fast response time and are capable of accurately measuring oxygen concentrations
at temperatures well below 0°C. Oxygen uptake rate ranged from 0.03 to 0.66 μmol O2 mg−1 h−1 and was sensitive to changes in both salinity and temperature. Temperature was the dominant factor affecting oxygen consumption
rates, which showed a significant increase with increasing temperature. A slight decrease was measured in oxygen consumption
with increasing salinity related to differential solubility of oxygen in waters of different salinities. Thermal sensitivity
of oxygen consumption determined from calculations of Q
10, indicated physiological adaptation of Artemia nauplii to the ranges of temperatures tested.
Handling editor: A. van Kerchove 相似文献
10.
Effects of low temperature on respiration and uptake of rubidium ions by excised barley and corn roots 总被引:5,自引:4,他引:1
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The effect of temperature upon ion uptake and respiration was investigated with excised roots of corn (Zea mays) and barley (Hordeum vulgare). A strong inhibition (Q10 = 5 to 8) of ion uptake was observed at temperatures below 10 C. At higher temperatures more normal temperature dependencies (Q10 = 1.3 to 2) were obtained. When the data were plotted according to the Arrhenius relationship, two different activation energies were indicated above and below 10 C. Other studies have related such changes with temperature in activation energy of processes to changes in membrane properties induced by temperature. These results suggest that such phase transitions may affect ion uptake processes. If so, then differences among species in their capacity to maintain normal root function at low soil temperature and to resist low temperature stress may be related to differences in the physical properties of cellular membranes. 相似文献
11.
ACTIVE UPTAKE OF [3 H]5-HT BY SYNAPTIC VESICLES FROM RAT BRAIN 总被引:2,自引:0,他引:2
The question of whether synaptic vesicles accumulate [3H]5-HT by an active process was investigated in a mixed population of vesiclcs from whole rat brain. The temperature dependence and the effect of metabolic inhibitors were studied in synaptosomal suspensions and vesicular fractions. Arrhenius plots for synaptosomes differed from those for vesicles as did the temperature coefficients for these two fractions. For synaptosomes the Q10 was 7 and for vesicles 1.6. However, if ATP was added to the incubation, the temperature dependence of vesicular amine accumulation became manifest; the Arrhenius plot resembled that of synaptosomes and the Q10 was greater than 20 indicating strong temperature dependence. In the presence of ATP, vesicular uptake was stimulated approx 8-fold. Ouabain, dinitrophenol and NEM inhibited synaptosomal uptake but failed to affect [3H]5-HT accumulation by vesicles in the absence of ATP. When ATP was added, vesicular uptake was also blocked by NEM but was unaffected by either ouabain or DNP. Total observed uptake consisted of two components, one ATP-dependent and one nonsaturable and ATP-independent. The active process had a Km= 1.25 × 10?7 M and could be completely blocked by either 10?3 M or 10?7 M-reserpine. Active vesicular [3H]5-HT uptake was magnesium dependent and was inhibited by sodium and potassium. Cation effects on uptake were specific and could not be accounted for by either changes in osmotic pressure or ionic strength. It was concluded that synaptic vesicles from whole rat brain accumulate [3H]5-HT by an active process. 相似文献
12.
RICHARD T. CONANT RHAE A. DRIJBER† MICHELLE L. HADDIX WILLIAM J. PARTON ELDOR A. PAUL ALAIN F. PLANTE‡ JOHAN SIX§ J. MEGAN STEINWEG 《Global Change Biology》2008,14(4):868-877
The relationship between organic matter (OM) lability and temperature sensitivity is disputed, with recent observations suggesting that responses of relatively more resistant OM to increased temperature could be greater than, equivalent to, or less than responses of relatively more labile OM. This lack of clear understanding limits the ability to forecast carbon (C) cycle responses to temperature changes. Here, we derive a novel approach (denoted Q10?q) that accounts for changes in OM quality during decomposition and use it to analyze data from three independent sources. Results from new laboratory soil incubations (labile Q10?q=2.1 ± 0.2; more resistant Q10?q=3.8 ± 0.3) and reanalysis of data from other soil incubations reported in the literature (labile Q10?q=2.3; more resistant Q10?q=3.3) demonstrate that temperature sensitivity of soil OM decomposition increases with decreasing soil OM lability. Analysis of data from a cross‐site, field litter bag decomposition study (labile Q10?q=3.3 ± 0.2; resistant Q10?q=4.9 ± 0.2) shows that litter OM follows the same pattern, with greater temperature sensitivity for more resistant litter OM. Furthermore, the initial response of cultivated soils, presumably containing less labile soil OM (Q10?q=2.4 ± 0.3) was greater than that for undisturbed grassland soils (Q10?q=1.7 ± 0.1). Soil C losses estimated using this approach will differ from previous estimates as a function of the magnitude of the temperature increase and the proportion of whole soil OM comprised of compounds sensitive to temperature over that temperature range. It is likely that increased temperature has already prompted release of significant amounts of C to the atmosphere as CO2. Our results indicate that future losses of litter and soil C may be even greater than previously supposed. 相似文献
13.
Carbon quality and soil microbial property control the latitudinal pattern in temperature sensitivity of soil microbial respiration across Chinese forest ecosystems
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《Global Change Biology》2018,24(7):2841-2849
Understanding the temperature sensitivity (Q10) of soil organic C (SOC) decomposition is critical to quantifying the climate–carbon cycle feedback and predicting the response of ecosystems to climate change. However, the driving factors of the spatial variation in Q10 at a continental scale are fully unidentified. In this study, we conducted a novel incubation experiment with periodically varying temperature based on the mean annual temperature of the soil origin sites. A total of 140 soil samples were collected from 22 sites along a 3,800 km long north–south transect of forests in China, and the Q10 of soil microbial respiration and corresponding environmental variables were measured. Results showed that changes in the Q10 values were nonlinear with latitude, particularly showing low Q10 values in subtropical forests and high Q10 values in temperate forests. The soil C:N ratio was positively related to the Q10 values, and coniferous forest soils with low SOC quality had higher Q10 values than broadleaved forest soils with high SOC quality, which supported the “C quality temperature” hypothesis. Out of the spatial variations in Q10 across all ecosystems, gram‐negative bacteria exhibited the most importance in regulating the variation in Q10 and contributed 25.1%, followed by the C:N ratio (C quality), fungi, and the fungi:bacteria ratio. However, the dominant factors that regulate the regional variations in Q10 differed among the tropical, subtropical, and temperate forest ecosystems. Overall, our findings highlight the importance of C quality and microbial controls over Q10 value in China's forest ecosystems. Meanwhile, C dynamics in temperate forests under a global warming scenario can be robustly predicted through the incorporation of substrate quality and microbial property into models. 相似文献
14.
Regional variation in the temperature sensitivity of soil organic matter decomposition in China's forests and grasslands 总被引:1,自引:0,他引:1
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Yuan Liu Nianpeng He Jianxing Zhu Li Xu Guirui Yu Shuli Niu Xiaomin Sun Xuefa Wen 《Global Change Biology》2017,23(8):3393-3402
How to assess the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition and its regional variation with high accuracy is one of the largest uncertainties in determining the intensity and direction of the global carbon (C) cycle in response to climate change. In this study, we collected a series of soils from 22 forest sites and 30 grassland sites across China to explore regional variation in Q10 and its underlying mechanisms. We conducted a novel incubation experiment with periodically changing temperature (5–30 °C), while continuously measuring soil microbial respiration rates. The results showed that Q10 varied significantly across different ecosystems, ranging from 1.16 to 3.19 (mean 1.63). Q10 was ordered as follows: alpine grasslands (2.01) > temperate grasslands (1.81) > tropical forests (1.59) > temperate forests (1.55) > subtropical forests (1.52). The Q10 of grasslands (1.90) was significantly higher than that of forests (1.54). Furthermore, Q10 significantly increased with increasing altitude and decreased with increasing longitude. Environmental variables and substrate properties together explained 52% of total variation in Q10 across all sites. Overall, pH and soil electrical conductivity primarily explained spatial variation in Q10. The general negative relationships between Q10 and substrate quality among all ecosystem types supported the C quality temperature (CQT) hypothesis at a large scale, which indicated that soils with low quality should have higher temperature sensitivity. Furthermore, alpine grasslands, which had the highest Q10, were predicted to be more sensitive to climate change under the scenario of global warming. 相似文献
15.
Yosepha Shahak Christof Klughammer Ulrich Schreiber Etana Padan Inge Herrman Günter Hauska 《Photosynthesis research》1994,39(2):175-181
The reduction by sulfide of exogenous ubiquinone is compared to the reduction of cytochromes in chromatophores of Rhodobacter capsulatus. From titrations with sulfide values for Vmax of 300 and 10 moles reduced/mg bacteriochlorophyll a·h, and for Km of 5 and 3 M were estimated, for decyl-ubiquinone-and cytochrome c-reduction, respectively. Both reactions are sensitive to KCN, as has been found for sulfide-quinone reductase (SQR) in Oscillatoria limnetica, which is a flavoprotein. Effects of inhibitors interfering with quinone binding sites suggest that at least part of the electron transport from sulfide in R. capsulatus employs the cytochrome bc
1-complex via the ubiquinone pool.Abbreviations BChl a
bacteriochlorophyll a
- DAD
diaminodurene
- decyl-UQ
decyl-ubiquinone
- LED
light emitting diode
- NQNO
2-n-nonyl-4-hydroxyquinoline-N-oxide
- PQ-1
plastoquinone 1
- SQR
sulfide-quinone reductase (E.C. 1.8.5.'.)
- UQ
ubiquinone 10
- Qc
the quinone reduction site on the cytochrome b
6
f/bc
1, complex (also termed Qi or Qr or Qn)
- Qs
the quinone reduction site on SQR
- Qz
quinol oxidation site on the b
6
f/bc
1, complex (also termed Qo or Qp) 相似文献
16.
Kurets V. K. Drozdov S. N. Popov E. G. Dembo E. D. Khilkov N. I. Trofimova S. A. 《Russian Journal of Plant Physiology》2003,50(3):308-313
Effects and aftereffects of typical temperatures of cultivar habitat (background temperature), heat-hardening, and cold-hardening temperatures on dark respiration of leaf segments and intact plants were investigated on plant species differing in cold tolerance—cucumber (Cucumis sativus L.), tomato (Lycopersicon esculentum Mill.), cicer milkvetch (Astragalus cicer L.), and narrow-leaved lupine (Lupinus angustifolium L.). At cold-hardening temperatures, the respiratory metabolism underwent rearrangements serving to compensate for elevated energy losses during plant adaptation. This was manifested in the increase in the respiratory coefficient (RC) and the Q
10 coefficient during hardening. The preconditioning of plants at hardening temperatures enhanced O2 uptake and elevated the ratio of growth respiration to maintenance respiration in the post-treatment period. Conversely, temperature variations within the background range had no aftereffect on RC, Q
10, and O2 uptake. 相似文献
17.
Andreas Schindlbacher Sophie Zechmeister-Boltenstern Barbara Kitzler Robert Jandl 《Plant and Soil》2008,303(1-2):323-330
We warmed the top soil of a mature coniferous forest stand by means of heating cables on control and trenched plots within
24 h by 10°C at 1 cm soil depth (9°C at 5 cm depth) and measured the effect on the autotrophic (RA) and heterotrophic (RH) component of total soil CO2 efflux (RS). The short time frame of warming enabled us to exclude confounding fluctuations in soil moisture and carbon (C) flow from
the canopy. The results of the field study were backed up by a lab soil incubation experiment. During the first 12 h of warming,
RA strongly responded to soil warming; The Q
10 values were 5.61 and 6.29 for 1 and 5 cm soil depth temperature. The Q
10 values for RA were almost twice as high as the Q
10 values of RH (3.04 and 3.53). Q
10 values above 5 are above reasonable plant physiological values for root respiration. We see interactions of roots, mycorrhizae
and heterotrophic microbes, combined with fast substrate supply to the rhizosphere as an explanation for the high short-term
temperature response of RA. When calculated over the whole duration (24 h) of the field soil-warming experiment, temperature sensitivities of RA and RH were similar (no significant difference at P < 0.05); Q
10 values were 3.16 and 3.96 for RA and 2.94 and 3.35 for RH calculated with soil temperatures at 1 and 5 cm soil depth, respectively. Laboratory incubation showed that different soil
moisture contents of trenched and control plots affected rates of RH, but did not affect the temperature sensitivity of RH. We conclude that a single parameter is sufficient to describe the temperature sensitivity of RS in soil C models which operate on larger temporal and spatial scales. The strong short-term response of RA may be of relevance in soils suspected to experience increasingly strong diurnal temperature variations. 相似文献
18.
Temperature responses of rates of respiratory CO2 efflux from plants, soils, and ecosystems are frequently modelled using exponential functions with a constant Q10 near 2.0 (fractional change in rate with a 10 °C increase in temperature). However, we present evidence that Q10 declines with short‐term increases in temperature in a predictable manner across diverse plant taxa. Thus, models using a constant Q10 are biased, and use of a temperature‐corrected Q10 may improve the accuracy of modelled respiratory CO2 efflux in plants and ecosystems in response to temperature and predicted global climate changes. 相似文献
19.
Ilagan RP Chapp TW Hiller RG Sharples FP Polívka T Frank HA 《Photosynthesis research》2006,90(1):5-15
Low temperature, steady-state, optical spectroscopic methods were used to study the spectral features of peridinin-chlorophyll-protein
(PCP) complexes in which recombinant apoprotein has been refolded in the presence of peridinin and either chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll d (Chl d), 3-acetyl-chlorophyll a (3-acetyl-Chl a) or bacteriochlorophyll a (BChl a). Absorption spectra taken at 10 K provide better resolution of the spectroscopic bands than seen at room temperature and reveal
specific pigment–protein interactions responsible for the positions of the Qy bands of the chlorophylls. The study reveals that the functional groups attached to Ring I of the two protein-bound chlorophylls
modulate the Qy and Soret transition energies. Fluorescence excitation spectra were used to compute energy transfer efficiencies of the various
complexes at room temperature and these were correlated with previously reported ultrafast, time-resolved optical spectroscopic
dynamics data. The results illustrate the robust nature and value of the PCP complex, which maintains a high efficiency of
antenna function even in the presence of non-native chlorophyll species, as an effective tool for elucidating the molecular
details of photosynthetic light-harvesting. 相似文献
20.
The effects of Photosystem II inhibiting herbicides, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), atrazine and two novel
2-benzylamino-1,3,5-triazine compounds, on photosynthetic oxygen evolution and chlorophyll a fluorescence induction were measured in thylakoids isolated from Chenopodium album (wild type and atrazine-resistant plants) and cyanobacterial intact cells. The resistant plants have a mutation of serine
for glycine at position 264 of the D1 protein. Diuron and two members of a novel class of 2-benzylamino-1,3,5-triazine compounds
were almost as active in wild-type as in atrazine-resistant thylakoids, indicating that the benzylamino substitution in the
novel triazines may be important for the lack of resistance in these atrazine-resistant plants. The inhibition by the herbicides
of oxygen evolution in the cyanobacteria was somewhat lower than in the thylakoids of Chenopodium album wild type, probably caused by a slower uptake in the intact cells. The so-called OJIP fluorescence induction curve was measured
during a one second light pulse in the absence and in the presence of high concentrations of the four herbicides. In the presence
of a herbicide we observed an increase of the initial fluorescence at the origin (Fo′), a higher J level, and a decreased
steady state at its P level (Fp). The increase to Fo′ and the decreased leveling Fp are discussed. After dark adaptation about
25% of the reaction centers are in the S0 state of the oxygen evolving complex with an electron on the secondary electron accepting quinone, QB. The addition of a herbicide causes a transfer of the electron on QB to the primary quinone acceptor, QA, and displacement of QB by the herbicide; the reduced QA leads to a higher Fo′. The decrease of Fp in the presence of the herbicides is suggested to be caused by inhibition of the
photo-electrochemical stimulation of the fluorescence yield.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献