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1.
Many biotypes of Lolium rigidum Gaud, (annual ryegrass) have developed resistance to herbicides; however, few have developed resistance to phenylurea herbicides. Two biotypes with different histories of herbicide selection pressure were six to eight times less sensitive to the phenylurea herbicide, chlorotoluron, than a susceptible biotype. Resistance was not due to differences in the herbicide target site as oxygen evolution by thylakoids isolated from resistant and susceptible biotypes was similarly inhibited by diuron and chlorotoluron. There was no difference in the uptake and distribution of chlorotoluron into resistant and susceptible plants. There was a twofold greater rate of chlorotoluron detoxification in resistant plants with N-demethylation being a major detoxification reaction. Resistant plants treated with a 3-h pulse of 120 M chlorotoluron recovered net carbon fixation after 42 h, half the time taken by susceptible plants. The mixed-function oxidase inhibitor 1-aminobenzotriazole (70 M) intensified the effects of chlorotoluron in resistant plants when applied in combination with the herbicide for 7 d. 1-Aminobenzotriazole also inhibited the metabolism of chlorotoluron in both resistant and susceptible plants. The cytochrome P-450 inhibitor, piperonyl butoxide piperonyl butoxide, interacted with chlorotoluron when applied to plants growing in soil. Chlorotoluron applied with reduced plant dry weight to a greater extent than chlorotoluron alone. It appears, therefore, that enhanced detoxification is the major mechanism of resistance to chlorotoluron in the resistant biotypes studied.Abbreviations ABT
1-aminobenzotriazole
- VLR1
Victorian L. rigidum biotype 1 — herbicide susceptible
- VLR69
Victorian L. rigidum biotype 69 — herbicide resistant
- WLR2
Western Australian L. rigidum biotype 2 — herbicide resistant
M.W.M.B, was supported by an Australian Postgraduate Research Award and a supplementary scholarship from the Grains Research and Development Corporation. We are very grateful to Dr. E. Ebert, Ciba Geigy, Basal, Switzerland for providing [14C]chlorotoluron and standards of chlorotoluron metabolites. We express our gratitude to Dr. John Huppatz of the CSIRO Division of Plant Industry for providing ABT. We also thank Ciba Geigy Australia for providing technical-grade chlorotoluron and formulated phenylurea herbicides. 相似文献
2.
Gravitropic stimulation of maize (Zea mays L.) seedlings resulted in a continuous curvature of the coleoptiles in a direction opposing the vector of gravity when the seedlings were rotated on a horizontal clinostat. The orientation of this response, however, was reversed when the gravitropic stimulation was preceeded by symmetric preirradiation with blue light (12.7 mol photons·m–2). The fluence-response curve of this blue light exhibited a lower threshold at 0.5 mol·m–2, and could be separated into two parts: fluences exceeding 5 mol·m–2 reversed the direction of the gravitropic response, whereas for a range between the threshold and 4 mol·m–2 a split population was obtained. In all cases a very strong curvature resulted either in the direction of gravity or in the opposite orientation. A minor fraction of seedlings, however, curved towards the caryopsis. Furthermore, the capacity of blue light to reverse the direction of the gravitropic response disappeared with the duration of gravitropic stimulation and it depended on the delay time between both stimulations. Thistonic blue-light influence appears to be transient, which is in contrast to the stability observed fortropistic blue-light effects.This work was supported by the Deutsche Forschungsgemeinschaft. 相似文献
3.
Resistance to Acetolactate Synthase-Inhibiting Herbicides in Annual Ryegrass (Lolium rigidum) Involves at Least Two Mechanisms 总被引:2,自引:0,他引:2
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WLR1, a biotype of Lolium rigidum Gaud. that had been treated with the sulfonylurea herbicide chlorsulfuron in 7 consecutive years, was found to be resistant to both the wheat-selective and the nonselective sulfonylurea and imidazolinone herbicides. Biotype SLR31, which became cross-resistant to chlorsulfuron following treatment with the aryloxyphenoxypropionate herbicide diclofop-methyl, was resistant to the wheat-selective, but not the nonselective, sulfonylurea and imidazolinone herbicides. The concentrations of herbicide required to reduce in vitro acetolactate synthase (ALs) activity 50% with respect to control assays minus herbicide for biotype WLR1 was greater than those for susceptible biotype VLR1 by a factor of >30, >30, 7,4, and 2 for the herbicides chlorsulfuron, sulfometuron-methyl, imazapyr, imazathapyr, and imazamethabenz, respectively. ALS activity from biotype SLR31 responded in a similar manner to that of the susceptible biotype VLR1. The resistant biotypes metabolized chlorsulfuron more rapidly than the susceptible biotype. Metabolism of 50% of [phenyl-U-14C]chlorsulfuron in the culms of two-leaf seedlings required 3.7 h in biotype SLR31, 5.1 h in biotype WLR1, and 7.1 h in biotype VLR1. In all biotypes the metabolism of chlorsulfuron in the culms was more rapid than that in the leaf lamina. Resistance to ALS inhibitors in L. rigidum may involve at least two mechanisms, increased metabolism of the herbicide and/or a herbicide-insensitive ALS. 相似文献
4.
To investigate whether the in-vivo photoinhibition of photosystem II (PSII) function by excess light is an intrinsic property of PSII, the maximal photochemical efficiency of PSII (Fv/Fm) and the content of functional PSII (measured by repetitive flash yield of oxygen evolution) were determined in leaves of pea (Pisum sativum L.), grown in 50 (low light), 250 (medium light), and 650 (high light) mol photons·m–2·s–1. The modulation of PSII functionality in vivo was induced in 1.1% CO2 by varying either (i) the duration (0–2 h) of light treatment (fixed at 1800 mol photons· m–2·s–1) or (ii) irradiance (0–3200 mol photons·m–2·s–1) at a fixed duration (1 h), after infiltration of leaves with water (control), lincomycin (an inhibitor of chloroplast-encoded protein synthesis), or a combination of lincomycin with nigericin (an uncoupler), through the cut petioles of leaves of 22-to 24-d-old plants. The reciprocity law of irradiance and duration of illumination for PSII function in vivo (Park et al. 1995, Planta 196: 401–411) holds in all differently light-grown peas, demonstrating that inactivation of functional PSII depends on photon exposure (mol photons·m–2), not on the rate of photon absorption. In vivo, PSII acts as an intrinsic photon counter and at higher photon exposures is inactivated following absorption of about 3 × 107 photons. There is a functional heterogeneity of PSII in vivo with 25% less-stable PSIIs that are inactivated at low photon exposure, compared to 75% more-stable PSIIs regardless of modulation of the photosynthetic apparatus. We suggest that the less-stable PSIIs represent monomers located in the nonappressed granal margins, while the more-stable PSIIs are dimers located in the appressed grana membrane cores. The capacity for D1-protein synthesis was the same in all the light-acclimated peas and saturated at low light, indicating that D1-protein repair is also an intrinsic property of PSII. This accounts for the low intensity required for recovery of photoinhibition in sun and shade plants which is independent of light-harvesting antennae size or PSII/PSI stoichiometries.Abbreviations D1-protein
psbA gene product
- D2 protein
psbD gene product
- Fo
chlorophyll fluorescence corresponding to open PSII reaction centres
- Fv, Fm
variable and maximum fluorescence after dark incubation, respectively
- PS
photosystem
- QB
secondary quinone electron acceptor
Financial support for this research by the Department of Employment, Education and Training/Australian Research Council International Research Fellowships Program (Korea) is gratefully acknowledged. 相似文献
5.
Sylvie Ferrario Marie-Hélène Valadier Jean-François Morot-Gaudry Christine H. Foyer 《Planta》1995,196(2):288-294
Transformed Nicotiana plumbaginifolia plants with constitutive expression of nitrate reductase (NR) activity were grown at different levels of nitrogen nutrition. The gradients in foliar NO
3
–
content and maximum extractable NR activity observed with leaf order on the shoot, from base to apex, were much decreased as a result of N-deficiency in both the transformed plants and wild type controls grown under identical conditions. Constitutive expression of NR did not influence the foliar protein and chlorophyll contents under any circumstances. A reciprocal relationship between the observed maximal extractable NR activity of the leaves and their NO
3
–
content was observed in plants grown in nitrogen replete conditions at low irradiance (170 mol photons·m–2 ·s–1). This relationship disappeared at higher irradiance (450 mol photons·m–2·S–1) because the maximal extractable NR activity in the leaves of the wild type plants in these conditions increased to a level that was similar to, or greater than that found in constitutive NR-expressors. Much more NO
3
–
accumulated in the leaves of plants grown at 450 mol photons·m–2·s–1 than in those grown at 170 mol photons·m–2·s–1 in N-replete conditions. The foliar NO
3
–
level and maximal NR activity decreased with the imposition of N-deficiency in all plant types such that after prolonged exposure to nitrogen depletion very little NO
3
–
was found in the leaves and NR activity had decreased to almost zero. The activity of NR decreased under conditions of nitrogen deficiency. This regulation is multifactoral since there is no regulation of NR gene expression by NO
3
–
in the constitutive NR-expressors. We conclude that the NR protein is specifically targetted for destruction under nitrogen deficiency. Consequently, constitutive expression of NR activity does not benefit the plant in terms of increased biomass production in conditions of limiting nitrogen.Abbreviations Chl
chlorophyll
- N
nitrogen
- NR
NADH-nitrate reductase
- WT
wild type 相似文献
6.
The light-dependent rate of photosystem-II (PSII) damage and repair was measured in photoautotrophic cultures of Dunaliella salina Teod. grown at different irradiances in the range 50–3000 mol photons · m–2· s–1. Rates of cell growth increased in the range of 50–800 mol photons·m–2·s–1, remained constant at a maximum in the range of 800–1,500 mol photons·m–2 ·s–1, and declined due to photoinhibition in the range of 1500–3000 mol photons·m–2·s–1. Western blot analyses, upon addition of lincomycin to the cultures, revealed first-order kinetics for the loss of the PSII reaction-center protein (D1) from the 32-kDa position, occurring as a result of photodamage. The rate constant of this 32-kDa protein loss was a linear function of cell growth irradiance. In the presence of lincomycin, loss of the other PSII reaction-center protein (D2) from the 34-kDa position was also observed, occurring with kinetics similar to those of the 32-kDa form of D1. Increasing rates of photodamage as a function of irradiance were accompanied by an increase in the steady-state level of a higher-molecular-weight protein complex ( 160-kDa) that cross-reacted with D1 antibodies. The steady-state level of the 160-kDa complex in thylakoids was also a linear function of cell growth irradiance. These observations suggest that photodamage to D1 converts stoichiometric amounts of D1 and D2 (i.e., the D1/D2 heterodimer) into a 160-kDa complex. This complex may help to stabilize the reaction-center proteins until degradation and replacement of D1 can occur. The results indicated an intrinsic half-time of about 60 min for the repair of individual PSII units, supporting the idea that degradation of D1 after photodamage is the rate-limiting step in the PSII repair process.Abbreviations Chl
chlorophyll
- PSI
photosystem I
- PSII
photosystem II
- D1
the 32-kDa reaction-center protein of PSII, encoded by the chloroplast psbA gene
- D2
the 34-kDa reactioncenter protein of PSII, encoded by the chloroplast psbD gene
- QA
primary electron-accepting plastoquinone of PSII
The work was supported by grant 94-37100-7529 from the US Department of Agriculture, National Research Initiative Competitive Grants Program. 相似文献
7.
Protective systems against active oxygen species in spinach: response to cold acclimation in excess light 总被引:25,自引:0,他引:25
Spinach (Spinacia oleracea L.) plants were acclimated to 1° C or maintained at 18° C under the same light regime (260–300 mol photons·m–2·s–1). The cold acclimation led to several metabolic and biochemical changes that apparently include improved protection of the photosynthetic apparatus against active oxygen species. In particular, cold-acclimated leaves exhibited a considerably higher ascorbate content and significantly increased activities of superoxide dismutase, ascorbate peroxidase, and monodehydroascorbate reductase in the chloroplasts. The level of dehydroascorbate reductase did not alter. Catalase activity decreased. The photosynthetic pigment composition of cold-acclimated spinach was characterized by increased levels of the xanthophylls lutein + zeaxanthin and violaxanthin. The observed changes are discussed in terms of their possible relevance for plant resistance to photoinhibition at chilling temperatures.Abbreviations DHA
dehydroascorbate
- GSH
reduced glutathione
- MDA
monodehydroascorbate
- SOD
superoxide dismutase
The authors thank the Deutsche Forschungsgemeinschaft for financial support of this study. 相似文献
8.
Acclimation to changes in the light environment was investigated in Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta. Plants grown under four light regimes showed differences in their development, morphology, photosynthetic performance and in the composition of the photosynthetic apparatus. Plants grown under high light showed higher maximum rates of oxygen evolution and lower levels of light-harvesting complexes than their low light-grown counterparts; plants transferred to low light showed rapid changes in maximum photosynthetic rate and chlorophyll-a/b ratio as they became acclimated to the new environment. In contrast, plants grown under lights of differing spectral quality showed significant differences in the ratio of photosystem II to photosystem I. These changes are consistent with a model in which photosynthetic metabolism provides signals which regulate the composition of the thylakoid membrane.Abbreviations
Aac1
gene encoding actin
- Chl
chlorophyll
- F
far-red-enriched light (R:FR = 0.72)
- FR
far-red light
- H
high light (400 mol · m–2 · s–1)
- L
low light (100 ml · m–2 · s–1)
- LHCII
light-harvesting complex of PSII
- Lhcb
genes encoding the proteins of LHCII
- R
red light
-
Rbcs
genes encoding the small subunit of Rubisco
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- W
white light (R:FR = 1.40)
This work was supported by Natural Environment Research Council Grant No. GR3/7571A. We would like to thank H. Smith (Botany Department, University of Leicester) and E. Murchie (University of Sheffield) for helpful discussions. 相似文献
9.
10.
Shi Tan Gregory R. Wolfe Francis X. Cunningham Jr Elisabeth Gantt 《Photosynthesis research》1995,45(1):1-10
Thylakoids isolated from cells of the red alga Porphyridium cruentum exhibit an increased PS I activity on a chlorophyll basis with increasing growth irradiance, even though the stoichiometry of Photosystems I and II in such cells shows little change (Cunningham et al. (1989) Plant Physiol 91: 1179–1187). PS I activity was 26% greater in thylakoids of cells acclimated at 280 mol photons · m–2 · s–1 (VHL) than in cells acclimated at 10 mol photons · m–2 · s–1 (LL), indicating a change in the light absorbance capacity of PS I. Upon isolating PS I holocomplexes from VHL cells it was found that they contained 132±9 Chl/P700 while those obtained from LL cells had 165±4 Chl/P700. Examination of the polypeptide composition of PS I holocomplexes on SDS-PAGE showed a notable decrease of three polypeptides (19.5, 21.0 and 22 kDa) in VHL-complexes relative to LL-complexes. These polypeptides belong to a novel LHC I complex, recently discovered in red algae (Wolfe et al. (1994a) Nature 367: 566–568), that lacks Chl b and includes at least six different polypeptides. We suggest that the decrease in PS I Chl antenna size observed with increasing irradiance is attributable to changes occurring in the LHC I-antenna complex. Evidence for a Chl-binding antenna complex associated with PS II core complexes is lacking at this point. LHC II-type polypeptides were not observed in functionally active PS II preparations (Wolfe et al. (1994b) Biochimica Biophysica Acta 1188: 357–366), nor did we detect polypeptides that showed immunocross-reactivity with LHC II specific antisera (made to Chlamydomonas and Euglena LHC II).Abbreviations Bis-Tris
bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane
- DCPIP
2,6-dichlorophenol indophenol
- -dm
dodecyl--d-maltoside
- HL
high light of 150 mol photons · m–2 · s–1
- LGB
lower green band
- LHC I
light-harvesting complex of PS I
- LHC II
light-harvesting complex of PS II
- LL
low light of 10 mol photons · m–2 · s–1
- ML
medium light of 50 mol photons · m–2 · s–1
- MES
2-(N-morpholino) ethanesulfonic acid
- P700
reaction center of PS I
- PFD
photon flux density
- Trizma
tris(hydroxymethyl)aminomethane
- UGB
upper green band
- VHL
very high light of 280 mol photons · m–2 · s–1 相似文献
11.
The light-dependent modulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity was studied in two species: Phaseolus vulgaris L., which has high levels of the inhibitor of Rubisco activity, carboxyarabinitol 1-phosphate (CA1P), in the dark, and Chenopodium album L., which has little CA1P. In both species, the ratio of initial to fully-activated Rubisco activity declined by 40–50% within 60 min of a reduction in light from high a photosynthetic photon flux density (PPFD; >700 mol · m–2 · s–1) to a low PPFD (65 ± 15 mol · m–2 · s–1) or to darkness, indicating that decarbamylation of Rubisco is substantially involved in the initial regulatory response of Rubisco to a reduction in PPFD, even in species with potentially extensive CA1P inhibition. Total Rubisco activity was unaffected by PPFD in C. album, and prolonged exposure (2–6 h) to low light or darkness was accompanied by a slow decline in the activity ratio of this species. This indicates that the carbamylation state of Rubisco from C. album gradually declines for hours after the large initial drop in the first 60 min following light reduction. In P. vulgaris, the total activity of Rubisco declined by 10–30% within 1 h after a reduction in PPFD to below 100 mol · m–2 · s–1, indicating CA1P-binding contributes significantly to the reduction of Rubisco capacity during this period, but to a lesser extent than decarbamylation. With continued exposure of P. vulgaris leaves to very low PPFDs (< 30 mol · m–2 · s–1), the total activity of Rubisco declined steadily so that after 6–6.5 h of exposure to very low light or darkness, it was only 10–20% of the high-light value. These results indicate that while decarbamylation is more prominent in the initial regulatory response of Rubisco to a reduction in PPFD in P. vulgaris, binding of CA1P increases over time and after a few hours dominates the regulation of Rubisco activity in darkness and at very low PPFDs.Abbreviations CA1P
2-carboxyarabinitol 1-phosphate
- CABP
2-carboxyarabinitol 1,5-bisphosphate
- kcat
substrate-saturated turnover rate of fully carbamylated enzyme
- PPFD
photosynthetically active photon flux density (400–700 nm)
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bisphosphate 相似文献
12.
In this study we investigated the basis for the reduction in the quantum yield of carbon assimilation in maize (Zea mays L. cv. LG11) caused by chilling in high light. After chilling attached maize leaves at 5° C for 6 h at high irradiance (1000 mol photons·m–2·s–1) chlorophyll fluorescence measurements indicated a serious effect on the efficiency of photochemical conversion by photosystem II (PSII) and measurements of [14C]atrazine binding showed that the plastoquinone binding site was altered in more than half of the PSII reaction centres. Although there were no direct effects of the chilling treatment on coupling-factor activity, ATP-formation capacity was affected because the photoinhibition of PSII led to a reduced capacity to energize the thylakoid membranes. In contrast to chilling at high irradiance, no photoinhibition of PSII accompanied the 20% decrease in the quantum yield of carbon assimilation when attached maize leaves were chilled in low light (50 mol photons·m–2·s–1). Thus it is clear that photoinhibition of PSII is not the sole cause of the light-dependent, chillinduced decrease in the quantum yield of carbon assimilation. During the recovery of photosynthesis from the chilling treatment it was observed that full [14C]atrazinebinding capacity and membrane-energization capacity recovered significantly more slowly than the quantum yield of carbon assimilation. Thus, not only is photoinhibition of PSII not the sole cause for the decreased quantum yield of carbon assimilation, apparently an appreciable population of photoinhibited PSII centres can be tolerated without any reduction in the quantum yield of carbon assimilation.Abbreviations and Symbols PPFD
photosynthetically active photon flux density
- PSII
photosystem II
- Fv/Fm
ratio of variable to maximal fluorescence
-
quantum yield of carbon assimilation
This work was supported in part by grants from the UK Agricultural and Food Research Council (AG 84/5) to N.R.B. and from the U.S. Department of Agriculture (Competitive Research Grant 87-CRCR-1-2381) to D.R.O. G.Y.N. was the recipient of a British Council scholarship and N.R.B. received a fellowship from the Organization for Economic Co-operation and Development (Project on Food Production and Preservation). 相似文献
13.
Anacystis nidulans R-2 produced ammonia from endogenous sources for at least 6 h when illuminated without external nitrogen source but with CO2 in the presence of 50 M methionine sulfoximine. The onset of ammonia release coinciding with complete inhibition of glutamine synthetase. The total quantity of ammonia which could be released exceeded the nitrogen content of small molecule pools, and suggested protein degradation as the most likely source of the nitrogen. Ammonia release was not accompanied by leakage of carbon compounds from the cells. Methionine sulfoximine-induced ammonia release was energy requiring, and was barely detectable under dark anaerobic conditions, or in the presence of 10 M carbonyl cyanide m-chlorophenylhydrazone in light. Phenyl methyl sulfonylfluoride, an inhibitor of serine proteases, eliminated ammonia release, and the rate of release was reduced to one-third of control values, after a lag, in the presence of 50–75 g/ml chloramphenicol. The rate of NH
+
4
release was maximal (1.4 nmol·min-1·mg-1 protein) if suspensions were bubbled with 100% O2, but could not be reduced below 0.6 nmol·min-1·mg-1 protein in air: CO2, suggesting that release was at most only partly due to photorespiration.Abbreviations used MSX
L-methionine D,L-sulfoximine
- PMSF
phenylmethylsulfonylfluoride
- CAP
chloramphenicol
- CCCP
carbonyl cyanide-m-chlorophenyl hydrazone 相似文献
14.
Jonas Collén Miguel Jiménez Del Rio Guillermo García-Reina Marianne Pedersén 《Planta》1995,196(2):225-230
Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of H2O2 was light dependent with a production of 1.2 mol·g FW–1·h–1 in sea water (pH 8.2) at an irradiance of 700 mol photons m–2·s–1. The excretion was also pH dependent: in pH 6.5 the production was not detectable (< 5 nmol·g FW–1·h–1) but at pH 9.0 the production was 5.0 mol·g FW–1·h–1. The production of H2O2 was totally inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). The ability of U. rigida growing in tanks (7501) under a natural light regime to excrete H2O2 was checked and found to be seven times higher at 08.00 hours than other times of the day. The H2O2 concentration in the cultivation tank (density: 2 g FW·l–1) reached the highest value (3 M) at 11.00 hours. Photosynthesis was not influenced by H2O2 formation. The H2O2 is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW–1·h–1 at pH 8.2 and 90 mmol·g FW–1·h–1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H2O2 production. The H2O2 production is sufficiently high to be of physiological and ecological significance, and is suggested to be a part of the defence against epi and endophytes.Abbreviations ACL
artificial, continuous light
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- GNL
greenhouse
- LDC
Luminol-dependent chemiluminescence
- SOD
Superoxide dismutase
This investigation was supported by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Hierta-Retzius Foundation, Marianne and Marcus Wallenberg Foundation, the Swedish Environmental Protection Board, and CICYT Spain. 相似文献
15.
Summary A mutant strain of Anabaena variabilis, strain SA-1 that supported growth of wheat plants in a hydroponic co-culture in nitrogen (N) free medium also produced enough oxygen (O2) to support root respiration. The steady-state concentration of net O2 in the co-culture was dependent on incident light intensity. At an incident photosynthetic photoflux (PPF) of 1000 mol photons·m–2·s–1, net O2 evolution by the co-culture in the root zone reached a maximum value of about 220 mol O2 evolved·h–1·mg chlorophyll (Chl)–1. The O2 concentration in the rhizosphere of the co-culture stayed above the ambient air level. O2 uptake in the dark by strain SA-1-supplemented wheat roots washed free of cyanobacterium was higher than the root respiration of nitrate-grown plants. Nitrate-grown plants required aeration for maximum growth while the wheat-cyanobacterial co-culture can be cultured without aeration. These results show that O2 produced by strain SA-1 can be used to supply the O2 needs for root respiration of wheat. Respiration reduced net O2 evolution by the mutant SA-1, decreasing the partial pressure of O2 at the sites of cyanobacterial attachment to the roots. This led to an increase in the specific activity of nitrogenase of the co-culture at the high light intensities used to support wheat growth. This activity of about 30 mol ethylene produced·mg Chl–1·h–1 was three-fold higher than the activities obtained with the free-living strain SA-1 assayed at the same light intensity. In the co-culture, ammonia produced by the mutant strain SA-1 was not detectable. The NH
inf4
sup+
produced by strain SA-1 was used by the wheat plants and, under these conditions, the total N content of the plants reached as high as 85% of the total N content of nitrate-grown plants. In the co-culture system the metabolism of wheat and the cyanobacterium complemented each other, leading to higher plant growth in N-free medium.
Offprint requests to: M. Gunasekaran 相似文献
16.
The effects of light intensity, oxygen concentration, and pH on the rates of photosynthesis and net excretion by metalimnetic phytoplankton populations of Little Crooked Lake, Indiana, were studied. Photosynthetic rates increased from 1.42 to 3.14 mg C·mg–1 chlorophylla·hour–1 within a range of light intensities from 65 to 150E·m–2·sec–1, whereas net excretion remained constant at 0.05 mg C·mg–1 chlorophylla·hour–1. Bacteria assimilated approximately 50% of the carbon released by the phytoplankton under these conditions. Excreted carbon (organic compounds either assimilated by bacteria or dissolved in the lake water) was produced by phytoplankton at rates of 0.02–0.15 mg C·mg–1 chlorophylla·hour–1. These rates were 6%–13% of the photosynthetic rates of the phytoplankton. Both total excretion of carbon and bacterial assimilation of excreted carbon increased at high light intensities whereas net excretion remained fairly constant. Elevated oxygen concentrations in samples incubated at 150E· m–2·sec–1 decreased rates of both photosynthesis and net excretion. The photosynthetic rate increased from 3.0 to 5.0 mg C·mg–1 chlorophylla· hour–1 as the pH was raised from 7.5 to 8.8. Net excretion within this range decreased slightly. Calculation of total primary production using a numerical model showed that whereas 225.8 g C·m–2 was photosynthetically fixed between 12 May and 24 August 1982, a maximum of about 9.3 g C·m–2 was released extracellularly. 相似文献
17.
The growth of the anaerobic acetogenic bacterium Acetobacterium woodii DSM 1030 was investigated in fructose-limited chemostat cultures. A defined medium was developed which contained fructose, mineral salts, cysteine · HCl and Ca pantothenate (1 mg · 1–1) supplied in a vitamin supplement. Growth at high dilution rates was dependent on the presence of CO2 in the gas phase. The
max was found to be 0.16 h–1 and the fructose maintenance requirement was 0.1 to 0.13 mmol fructose · (g dry wt)–1 · h–1. A growth yield of 61 g dry wt · (mol fructose)–1, corrected for the cell maintenance requirement and for incorporation of fructose carbon into cell biomass, was determined from the fructose consumption. A corresponding growth yield of 69 g dry wt · (mol fructose)–1 was calculated from the acetate production assuming that fructose fermentation was homoacetogenic. A YATP of 12.2 to 13.8 g dry wt · (mol ATP)–1 was calculated from these growth yields using a value of 5 mol ATP · (mol fructose)–1 as an estimate of the amount of ATP synthesised from fructose fermentation. The addition of yeast extract (0.5 g · 1–1) to the medium did not influence the
max or cell yield. After prolonged growth under fructose-limited conditions the requirement of the culture for CO2 in the gas phase was reduced.Abbreviations YE
yeast extract
- IC
inorganic carbon
- D
fermenter dilution rate : h–1
- MX
maintenance requirement for X: mmol X · (g dry wt)–1 · h–1
- X
may be fructose (Fruct), fructose consumed in energy metabolism (Fruct [E]), acetate (Ac)
- ATP
CO2, NH
inf4
sup+
or Pi
- qX
specific rate of utilisation or consumption of X: mmol X · (g dry wt)–1 · h–1
- V
fermenter volume: litre
- rC
· Cell, fermenter cell carbon production: mmol C · h–1
- YX
yield of cells on X: g dry wt · (mol X)–1
- Y
infx
supmax
the yield corrected for cell maintenance: g dry wt · (mol X)–1
- SATP
stoichiometry of ATP synthesis from fructose: mol ATP · (mol frucose)–1
- x
cell concentration: g dry wt · 1–1
-
specific growth rate : h–1
-
max
maximum specific growth rate: h–1 相似文献
18.
Biochemical and biophysical parameters, including D1-protein turnover, chlorophyll fluorescence, oxygen evolution activity and zeaxanthin formation were measured in the marine seagrassZostera capricorni (Aschers) in response to limiting (100 mol·m–2·–1), saturating (350 mol·m–2·s–1) or photoinhibitory (1100 mol·m–2·s–1) irradiances. Synthesis of D1 was maximal at 350 mol·m–2·s–1 which was also the irradiance at which the rate of photosynthetic O2 evolution was maximal. Degradation of D1 was saturated at 350 mol·m–2·s–1. The rate of D1 synthesis at 1100 mol·m–2·s–1 was very similar to that at 350 mol·m–2·s–1 for the first 90 min but then declined. At limiting or saturating irradiance little change was observed in the ratio of variable to maximal fluorescence (Fv/Fm) measured after dark adaptation of the leaves, while significant photoinhibition occurred at 1100 mol·m–2·s–1. The proportion of zeaxanthin in the total xanthophyll pool increased with increasing irradiance, indicative of the presence of a photoprotective xanthophyll cycle in this seagrass. These results are consistent with a high level of regulatory D1 turnover inZostera under non-photoinhibitory irradiance conditions, as has been found previously for terrestrial plants.We would like to thank Professor Peter Böger (Department of Plant Biochemistry, University of Konstanz, Germany) for the kind gift of D1 antibodies. This work was partly supported by a University of Queensland Enabling Grant to CC. 相似文献
19.
The increase in growth, determined by dry weight gain, of rice (Oryza sativa L.) and maize (Zea mays L.) caused by foliar applications of 9--L(+) adenosine, a putative second messenger elicited by triacontanol, was studied under different environmental conditions. Maize seedlings cultured in the greenhouse under approximately 100 mol m–2s–1 of light prior to treatment with L(+) adenosine did not respond unless they received supplemental light (250–300 mol m–2s–1) after treatment. Exposure of rice seedlings growing for 16 h at 150 mol m–2s–1 to short periods of 450 mol m–2s–1 (< than 20 min) had no effect on the positive response of rice to L(+) adenosine; however, exposure for 60 min or more increased the growth of rice and obviated the effect of L(+) adenosine. Rice seedlings treated with L(+) adenosine at different times during the day responded only when treated 9 to 12h after initiation of the photoperiod. Normal growing temperatures under different light intensities had little or no direct effect on the response of plants to L(+) adenosine. 相似文献
20.
Cytological abnormalities are observed in salivary chromosomes of stocks of Drosophila melanogaster possessing DNA-induced, v
+ transformations mapping either at 10.0 or 133.0. In initial studies, the untransformed control stock and six transformed stocks were assigned code numbers prior to cytological examination. Salivary chromosome regions 1B9 · 10—1C2 · 3 and 10A1 · 2—10B1 · 2 were carefully examined in each of the coded stocks. (Band 1B11 is tentatively identified as the site of the suppressor-of-sable locus at 10.0 and band 10A1 is the site of the vermilion locus at 133.0.) When cytological studies were complete each of the stocks was identified. In every transformed stock examined, anomalies had been scored in association with the chromosome region corresponding to the map position of the DNA-induced alteration. In the control stock, anomalies were observed at neither position. — Approximately 10–15% of the nuclei in transformed stocks exhibit significant departure from normality in the pertinent chromosome region. The perturbations range from minor alterations of banding pattern to apparent pieces of extra chromatin in the most extreme cases. In stocks with v+ transformations mapping at 133.0, apparent extra chromatin is observed with frequencies varying from 0.05 to 0.02. In these cases the abnormal structures are associated with salivary band 10A1 · 2, forming a band-like structure, frequently an almost perfect doublet (open or closed), often lying in an abnormal position, and with fine chromatin threads connecting to the chromosomal doublet. In stocks with v+ transformations mapping at 10.0, apparent extra chromatin is observed with a frequency of about 0.001. These abnormal structures are frequently thread-like, lying to the side or off the tip of the chromosome, with compact regions which sometimes resemble chromomeres, and with fine threads connecting to the chromosomal 1B11 region. 相似文献