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131.
132.
在缺钾培养条件下,高粱苗地上部单位鲜重含钾量由于地上部鲜重的增加而下降。从高梁苗钾缺乏症出现的时间、频率和程度来看,Pro培养似乎有利于缓和或减轻缺钾对植物造成的伤害。在同样含钾量情况下,以Ca(NO_3)_2为氮源的苗受到缺钾伤害要重于以Pro为氮源的苗受到的伤害,其钾缺乏症植株的百分数增加值与含钾量降低值之比为0.26,以Pro为氮源的缺钾营养液培养的苗为0.09,即下降同样量的钾前者苗的钾缺乏症的增加要大大地超过后者。Pro并不减轻在缺钾情况下叶绿素含量的下降。 相似文献
133.
The phylogenetically related phototrophic bacteria Rhodospirillum tenue and Rhodocyclus purpureus modulate activity of their glutamine synthetases by adenylylation/deadenylylation. Evidence for covalent modification includes the inhibitory effect of Mg2+ on the activity of glutamine synthetase extracted from cells of either species grown on excess ammonia, and the lack of Mg2+ inhibition of activity of the enzyme isolated from N2-(R. tenue) or glutamine (R. purpureus)-grown cells. In addition, snake venom phosphodiesterase treatment of glutamine synthetase from either species grown on excess ammonia relieved Mg2+ inhibition of the enzyme (as measured via the -glutamyl transferase assay), and changed the cation specificity from Mn2+ to Mg2+ (in the biosynthetic assay). 相似文献
134.
Pamela J. Weathers James F. Danielli Peter M. Bradley Diane M. Hebb Judith E. Miller Rick L. Pesano 《Physiologia plantarum》1984,61(3):441-448
We report the isolation of a cukaryotic green alga ( Chlorella , strain WPI-2) which accumulates large stores of nitrogen (N) during growth in N-free medium and seems to incorporate14 N2 , yet does not reduce acetylene to ethylene. Total N accumulation during growth on N-free medium and in gases free of combined N was measured by three methods: Kjeldahl, oxidative pyrolysis via chemiluminescence (Antek N analyzer), and Dumas (Coleman N analyzer). Increases in N ranging from 22–64%± 1% were observed. Isotope dilution studies using cells labelled with 15 NO 3 - and then shifted to 14 N2 in N-free medium showed dilution of the 15 N isotope by 14 N from 5.67 to 5.32%± 0.05%. Using a variety of conditions, we were unable to demonstrate the reduction of acctylene to ethylene by WPI-2, although diazotrophic cyanobacteria gave positive results. Although the data on WPI-2 are not conclusive in establishing this alga as a diazotroph, the data do suggest that within the Chlorophyceae there may exist a novel form of nitrogen gas metabolism. 相似文献
135.
Dr. Paul A. Lespinat Yves M. Berlier Guy D. Fauque Rene Toci Gerard Denariaz Jean LeGall 《Journal of industrial microbiology & biotechnology》1987,1(6):383-388
Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D2–H+ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism. 相似文献
136.
烟草愈伤组织分化和芽原基形成期间呼吸代谢途径的改变 总被引:3,自引:0,他引:3
接种在继代培养基上的柳叶烟草愈伤组织,未观察到组织分化和芽原基形成。在分化培养基上生长的愈伤组织,接种后第6天可见拟分生组织和管胞分化,9—12天有芽原基形成,15—18天可观察到苗端结构。根据碘乙酸、Na_3PO_4和丙二酸抑制试验,以及3-磷酸甘油醛脱氢酶与琥珀酸脱氢酶活性测定结果,初步表明烟草愈伤组织呼吸中存在有EMP、HMP和TCAC代谢途径.在发生输导组织和芽原基分化的愈伤组织中(接种后第6—12天),HMP途径的运行程度较高;而芽原基的继续生长(培养12天以后),则与EMP途径的增加有关;分化培养基上生长的愈伤组织,始终较继代培养愈伤组织具有较高的FCAC活性水平。 相似文献
137.
Dipple Anthony Pigott Margaret A. Milner John A. 《Biological trace element research》1986,10(2):153-157
Since selenium has been found to exert a protective action against carcinogenesis in various systems, the mechanism where-by
sodium selenite inhibits DNA binding of the carcinogen, 7,12-dimethylbenz[a]anthracene, was investigated. It was found that
selenite preferentially reduced DNA binding occurring through ananti-dihydrodiol epoxide metabolite of this carcinogen by inhibiting the induction of an enzyme system that generates this specific
reactive metabolite. 相似文献
138.
A conventional balance study with 48 male weanling rats was conducted to determine true absorption and endogenous fecal excretion
of manganese (Mn) in relation to dietary Mn supply, following the procedures of a previously adapted isotope dilution technique.
After 10 d on a diet with 1.5 ppm Mn, eight animals each were assigned to diets containing 1.5, 4.5, 11.2, 35, 65, or 100
ppm Mn on a dry-matter basis. Three days later, each rat was given an intramuscular54Mn injection and kept on treatment for a balance period of 16 d.
Apparent Mn absorption assessed for the final 8 d, averaged 8.6 μg/d without significant treatment effects, although Mn intake
ranged from 18.6 to 1200 μg/d, in direct relation to dietary Mn concentrations. Mean fecal excretion of endogenous Mn for
the six treatments was 0.9, 2.7, 7.4, 11.0, 16.3, and 17.7 μg/d, respectively. These values delineate the rates to which true
absorption exceeded apparent rates. True absorption, as percent of Mn intake, averaged 28.7, 15.9, 11.7, 6.1, 3.4, and 2.0,
respectively, as compared with mean values of 23.9, 10.9, 6.2, 3.4, 1.2, and 0.5 for percent apparent absorption. It was concluded
that both true absorption and endogenous fecal excretion markedly responded to Mn nutrition and that the reduction in the
efficiency of true absorption was quantitatively the most significant homeostatic response for maintaining stable Mn concentrations
in body tissues. 相似文献
139.
Shoots of Sedum nuttallianum exhibited CAM* acid fluctuations in the field. These nocturnal acid accumulations persisted in the laboratory under well-watered and water-stressed conditions. Simultaneous measurements of transpiration, however, indicated daytime stomatal opening and nocturnal stomatal closure. Measurements of CO2 and H2O vapor exchange continuously for six days after watering substantiated these results in part: the majority of CO2 uptake occurred during the day early in the experiment; however, after several days without water, nighttime CO2 uptake was stimulated and eventually was greater than the drastically reduced daytime CO2 uptake. This nighttime uptake was never quite sufficient to account for all estimated increases in tissue acidity. Thus, a combination of CAM and CAM-cycling occurred early in the desiccation experiment. Evidence for CAM and a form of CAM-idling was found later in the experiment. Though nighttime CO2 uptake occurred and persisted after only one day without water, rates were too low to alter the tissue 13C/12C value from a C3-like number (–30). Thus, although CAM and CAM-idling may have survival value during extended droughts, shoots of S. nuttallianum apparently utilize the C3 pathway to obtain most of their carbon.Abbreviations C3
pathway
- CO2
fixation pathway in which an intermediate containing 3 carbon atoms is formed
- CAM
Crassulacean acid metabolism
- Chl
Chlorophyll
- ci
internal CO2 concentration
- DW
Dry weight
- gc
mean conductance to CO2
- FW
Fresh weight
- PAR
Photosynthetically active radiation
- SD
Standard deviation
- vpd
Vapor pressure deficit
- WUE
Water use efficiency 相似文献
140.
Previous studies have shown that the development anomaly encountered in meristem culture, known as vitreous plants, is due to deficient lignin synthesis. This anomaly can be cured by addition of phloridzin to the culture medium. This study examines the activities of some enzymes involved in the synthesis of lignins and of flavonoids in normal and in vitreous plants of two apple cultivars. The results showed that all enzymes were consistently less active in the vitreous plants. This agrees with previous studies made on the hydroxycinnamate: CoA ligase activity in Prunus avium (L.) meristem-derived plants. The study on the substrate specificity of the enzyme demonstrates that while its activity is lower in the vitreous plant, its conformation is identical with that of the normal plant; the substrate that is specific to enzyme extracts of both sources is para-coumaric acid. 相似文献