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1.
Sulphate concentrations and 34S ratios were monitored in bulk precipitation, spruce throughfall, and soil water (depth of 30 and 90 cm) at ervená jáma (CER) and Naetín (NAC), two severely polluted sites in the Czech Republic, between December 1992 and September 1994. Throughfall [SO4 2–], up to 80 mg L–1 in winter and as low as 7 mg L–1 in summer, was higher than [SO4 2–] in bulk precipitation (annual average 6 mg L–1). There was a distinct seasonaity in S isotope abundances, with lower 34SBULK in summer (+4 per mil CER, + 6 per mil NAC) and lower 34STF in winter (+3 per mil CER, +4 per mil NAC). Wintertime 34SBULK was around +8 per mil at CER and +10 per mil at NAC, summertime 34STF was close to +7 per mil at both sites. For only a 1- month period in spring, bulk precipitation S became isotopically lighter than throughfall S. Bulk precipitation data from CER were in good agreement with those from the nearby monitoring station Lesná (LES), typically differing by less than 10 mg L–1 and 2 per mil in [SO4 2–] and 34S, respectively. Suction lysimeters (soil depth of 30 and 90 cm) yielded higher sulphate concentrations and lower 34S ratios compared to both bulk and throughfall precipitation. Little seasonality was observed in [SO4 2–] at 30 cm (around 40 mg L–1); at 90 cm [SO4 2–] was higher in winter (70 mg L–1) than in summer (45 mg L–1). 34S at 90 cm was <+5 per=" mil=" in=" 1993=" and=" up=" to=" +7.5=" in=" 1994,=" lower=" in=" the=" first=" year=" and=" higher=" in=" the=" second=" year=" compared=" to=" the=" depth=" of=" 30=" cm.=" sulphur=" fluxes=" at=" cer=" and=" nac=" are=" characterized=" by=" distinct=" isotope=" compositions=" and=" can=" therefore=" be=" used=" to=" trace=" s=" pathways=" and=" transformations=" in=" the=" forest=">  相似文献   

2.
High-elevation red spruce-Fraser fir forests in the Southern Appalachian mountains: 1) receive among the highest rates of atmospheric deposition measured in North America, 2) contain old-growth forests, 3) have shown declines in forest health, 4) have sustained high insect-caused fir mortality, and 5) contain poorly buffered soils and stream systems. High rates of nitrogen and sulphur deposition (1900 and 2200 Eq·ha–1·yr–1, respectively) are dominated by dry and cloud deposition processes. Large leaching fluxes of nitrate-nitrogen (100–1400 Eq·ha–1·yr–1) occur within the soil profile. We have expanded the study to the watershed scale with monitoring of: precipitation, throughfall, stream hydrology, and stream chemistry. Two streamlets drain the 17.4 ha Noland Divide Watershed (1676–1920m) located in the Great Smoky Mountains National Park. A network of 50 20x20 m plots is being used to assess stand structure, biomass, and soil nutrient pools. Nitrate is the predominant anion in the streamlets (weighted concentrations: 47 and 54 eq·L–1 NO3 –; 31 and 43 eq·L–1 SO4 2–). Watershed nitrate export is extremely high (1000 Eq·ha–1 yr–1), facilitating significant base cation exports. Stream acid neutralizing capacity values are extremely low (–10 to 20 eq·L–1) and episodic acidifications (pH declines of a full unit in days or weeks time) occur. Annual streamwater sulfate export is on the order of 770 Eq·ha–1yr–1 or about one-third of total annual inputs, indicating there is net watershed sulfate retention. The system is highly nitrogen saturated (Stage 2, Stoddard, 1994) and this condition promotes both chronic and episodic stream acidification.  相似文献   

3.
The degree to which floating aquatic plants concentrate Se in tissues was determined for four species grown in solutions containing various levels of Se. Results of this greenhouse study showed that all four plant species, Azolla caroliniana, Eichhornia crassipes, Salvinia rotundi folia, and Lemna minor absorbed Se quickly upon exposure to Se in water as concentrated as 2.5 g Se mL–1, and attained maximum tissue concentrations within 1 to 2 weeks. Azolla absorbed Se to the highest tissue concentration (about 1000 g Se g–1 dry matter) from the 2.5 g Se mL–1 solution, followed by Salvinia (700 g Se g–1), Lemna (500 g Se g–1),and Eichhornia (300 g Se g–1). Plant growth appeared unaffected by solution Se concentrations lower than about 1.25 g mL–1. These results indicate potential for rapid Se movement from water into aquatic food chains, and for use of aquatic plants for Se removal in wastewater treatment systems.  相似文献   

4.
The Lysina catchment in the Czech Republic was studied to investigate the biogeochemical response of Al to high loadings of acidic deposition. The catchment supports Norway spruce plantations and is underlain by granite and podzolic soil. Atmospheric deposition to the site was characterized by high H+ and SO4 2– fluxes in throughfall. The volume-weighted average concentration of total Al (Alt) was 28 mol L–1 in the O horizon soil solution. About 50% of Alt in the O horizon was in the form of potentially-toxic inorganic monomeric Al (Ali). In the E horizon, Alt increased to 71 mol L–1, and Ali comprised 80% of Alt. The concentration of Alt (120 mol L–1) and the fraction of Ali (85%) increased in the lower mineral soil due to increases in Ali and decreases in organic monomeric Al (Alo). Shallow ground water was less acidic and had lower Alt concentration (29 mol L–1). The volume-weighted average concentration of Alt was extremely high in stream water (60 mol L–1) with Ali accounting for about 60% of Alt. The major species of Ali in stream water were fluorocomplexes (Al-F) and aquo Al3+. Soil solutions in the root zone were undersaturated with respect to all Al-bearing mineral phases. However, stream water exhibited Ali concentrations close to solubility with jurbanite. Acidic waters and elevated Al concentrations reflected the limited supply of basic cations on the soil exchange complex and slow weathering, which was unable to neutralize atmospheric inputs of strong acids.  相似文献   

5.
Simultaneous soil acidification and deposition of heavy metals is a major concern for forest and agricultural soils of the Black Triangle region of East Central Europe including southern former East Germany, northern Bohemia of the Czech Republic, and southern Poland. The objective of this project was to develop historical and future projections of acid and heavy metal deposition to soils (As, Cd, Pb, Zn) and to produce a preliminary map of soil sensitivity to cadmium pollution and uptake by crops. Ultimately, we wish to assess the relative hazard and recovery times of soils to metals deposition in the region. Emission and deposition data bases obtained from several models developed at IIASA were linked using the Geographical Information System ARC/INFO to produce soil maps of sensitivity to cadmium mobility based on metals deposition, soil type, soil texture, organic matter content, and acid deposition. RAINS 6.1 (Alcamo et al., 1990) was utilized to produce maps of acid deposition for EMEP grids (150 km x 150 km). The largest amount of acid load is deposited in southern East Germany. Sulfur deposition in that area was 10–12 gS/m2/yr in 1990, and S+N deposition exceeded 8000 eq/ha/yr. But the hot spot for metals deposition is further to the east, in the Silesia area of southern Poland. The TRACE2 trajectory model of Alcamo, Bartnicki, and Olendrzynski (1992) was used to estimate cumulative metals deposition since 1955 with scenarios to 2010. Pb has improved over Europe since 1970 when depositions in the Ruhr River Valley of West Germany exceeded 60 mg/m2/yr. But cadmium deposition in southern Poland (Katowice and Krakow) has now accumulated to 60–70 mg/m2 by atmospheric deposition alone. During base case simulations from 1955–87, approximately 1.8 mg/kg Pb and 0.12 mg/kg Cd have been added to the mixed plow-layer of 30 cm. If these emissions continue indefinitely, the accumulation of metals will become problematic for agriculture and the food chain.  相似文献   

6.
Ergosterol and microbial biomass C were measured in 26 arable, 16 grassland and 30 forest soils. The ergosterol content ranged from 0.75 to 12.94 g g-1 soil. The geometric mean ergosterol content of grassland and forest soils was around 5.5 g g-1, that of the arable soils 2.14 g g-1. The ergosterol was significantly correlated with biomass C in the entire group of soils, but not in the subgroups of grassland and forest soils. The geometric mean of the ergosterol: microbial biomass C ratio was 6.0 mg g-1, increasing in the order grassland (5.1), arable land (5.4) and woodland (7.2). The ergosterol:microbial biomass C ratio had a strong negative relationship with the decreasing cation exchange capacity and soil pH, indicating that the fungal part of the total microbial biomass in soils increased when the buffer capacity decreased. The average ergosterol concentration calculated from literature data was 5.1 mg g-1 fungal dry weight. Assuming that fungi contain 46% C, the conversion factor from micrograms ergosterol to micrograms fungal biomass C is 90. For soil samples, neither saponification of the extract nor the more effective direct saponification during extraction seems to be really necessary.  相似文献   

7.
This study deals with the question of establishing a statistical model to test the hypothesis that the use of pure water reduces deaths from diseases caused by pathogenic bacteria. The statistical analysis is based on data for 48 states of the United States for the year 1970. The results of this study suggest that an increase in the use of pure water would, ceteris paribus, decrease death rates due to certain diseases. The findings of this study are especially useful for developing nations where a very small proportion of the population is still served by publicly supplied water.  相似文献   

8.
Summary The influence of soil moisture on denitrification and aerobic respiration was studied in a mull rendzina soil. N2O formation did not occur below –30 kPa matric water potential (m), above 0.28 air-filled porosity (a) and below 0.55 fractional water saturation (v/PV volumetric water content/total pore volume). Half maximum rates of N2O production and O2 consumption were obtained between m = –1.2 and –12 kPa,a = 0.05 and 0.23, and v/PV = 0.63 and 0.92. No oxygen consumption was measured at v/PC 1.17. O2 uptake and denitrification occurred simultaneously arounda = 0.10 (at m = –10 kPa and v/PV = 0.81) at mean rates of 3.5 µl O2 and 0.3 µl N2 h–1g–1 soil. Undisturbed, field-moist soil saturated with nitrate solution showed constant consumption and production rates, respectively, of 0.6 µl O and 0.22 µl N2O h–1g–1 soil, whereas the rates of air-dried remoistened soil were at least 10 times these values. The highest rates obtained in remoistened soil amended with glucose and nitrate were 130 µl O2 and 27 µl N2O h–1g–1 soil.  相似文献   

9.
Mercury Content of Illinois Soils   总被引：2，自引：0，他引：2  
For a survey of Illinois soils, 101 cores had been collected and analyzed to determine the current and background elemental compositions of Illinois soils. Mercury and other elements were determined in six samples per core, including a surface sample from each core. The mean mercury content in the surface samples was 33 ± 20 g/kg soil, and the background content was 20 ± 9 g/kg. The most probable sources of mercury in these soils were the parent material, and wet and dry deposition of Hg0 and Hg2+ derived from coal-burning power plants, other industrial plants, and medical and municipal waste incinerators. Mercury-bearing sewage sludge or other fertilizers applied to agricultural fields could have been the local sources of mercury. Although the mercury content correlated with organic carbon content or clay content in individual cores, when all the data were considered, there was no strong correlation between mercury and either the organic carbon or the clay-size content.  相似文献   

10.
Seasonal changes in microbial biomass and nutrient flush in forest soils   总被引：14，自引：0，他引：14  
Microbial biomass and N, P, K, and Mg flushes were estimated in spring, summer, autumn, and winter samples of different forest soils. The microbial biomass showed significant seasonal fluctuations with an average distribution of 880±270 g C g-1 soil in spring, 787±356 g C g-1 soil in winter, 589±295 g C g-1 soil in summer, and 560±318 g C g-1 soil in autumn. The average annual concentrations of C, N, P, K, and Ca in the microbial biomass were 704, 106, 82, 69 and 10 g g-1 soil, respectively. Microbial C represented between 0.5 and 2% of the organic soil C whereas the percentage of microbial N with respect to the total soil N was two-to threefold higher than that of C; the annual fluctuations in these percentages followed a similar trend to that of the microbial biomass. Microbial biomass was positively correlated with soil pH, moisture, organic C, and total N. The mean nutrient flush was 31, 15, 7, and 4 g g-1 soil for N, K, P, and Mg, respectively, and except for K, the seasonal distribution was autumn spring winter summer. The average increase in available nutrient due to the mineralization of dead microbial cells was 240% for N, and 30, 26, and 14% for P, K, and Mg, respectively. There was a positive relationship between microbial biomass and the N, P, K, and Mg flushes. All the variables studied were significantly affected by the season, the type of soil, and the interaction between type of soil and season, but soil type often explained most of the variance.  相似文献   

11.
Summary The relative persistence of -, and -isomers of hexachlorocyclohexane (HCH) was studied in a flooded soil with and without rice seedlings under greenhouse conditions. -HCH was more stable than - and -HCH in both planted and unplanted systems. - and -HCH decreased to negligible levels (5.5% for the -isomer and 2.4% for the -isomer) after 30 days in planted and unplanted soils. During the same period, 30.9% of the added -HCH was recovered from planted soil and 50.6% from unplanted soil. Likewise, in anaerobically (H2 + CO2 atmosphere) incubated mineral salts solution inoculated with suspensions from rice rhizosphere and non-rhizosphere soils, -HCH decreased to low levels (< 15%) within 5 days. Most of the added -HCH was recovered from mineral solution inoculated with nonrhizosphere soil suspension even after 30 days while -HCH decreased to 53.6% of the original level in mineral solution inoculated with rice rhizosphere soil suspension. The data reveal that the degradation of anaerobically unstable HCH isomers is not retarded by the possible aeration of a flooded soil by rice roots.  相似文献   

12.
Knowledge of the cycling and compartmentalization of soil C that influence C storage may lead to the development of strategies to increase soil C storage potentials. The objective of this study was to use soil hydrolases and soil aggregate fractionation to explore the relationship between C cycling activity and soil aggregate structure. The prairie chronosequence soils were native prairie (NP) and agricultural (AG) and tallgrass prairies restored from agriculture in 1979 (RP-79) and 1993 (RP-93). Assays for -glucosidase (E.C. 3.2.1.21) and N-acetyl--glucosaminidase (NAGase, EC 3.2.1.30) activities were conducted on four aggregate size fractions (>2 mm, 1–2 mm, 250 m–1 mm, and 2–250 m) from each soil. There were significantly greater amounts of >2-mm aggregates in the RP-79 and RP-93 soils compared to the NP and AG soils due to rapid C accumulation from native plant establishment. Activities for both enzymes (g PNP g–1 soil h–1) were greatest in the microaggregate (2–250 m) compared to the macroaggregate (>2 mm) fraction; however, microaggregates are a small proportion of each soil (<12%) compared to the macroaggregates (75%). The RP soils have a hierarchical aggregate system with most of the enzyme activity in the largest aggregate fractions. The NP and AG soils show no hierarchical structure based on aggregate C accretion and significant C enzyme activity in smaller aggregates. The distribution of enzyme activity may play a role in the storage of C whereby the aggrading restored soils may be more susceptible to C loss during turnover of macroaggregates compared to the AG and NP soils with less macroaggregates.  相似文献   

13.
We investigated the effects of Topogard 50 WP (3 kg ha–1) on soil respiration, mineral N content, and number of denitrifying and total bacteria in four coarse-textured volcanic soils for 91 days. Topogard application decreased CO2 evolution in acid soils (Tepedibi and Karaçakl) whereas soil respiration was initially increased in neutral and alkaline soils (Kaba and Balar). The herbicide application significantly stimulated ammonification in Kaba and Balar soils, while Tepedibi and Karaçakl soils showed significantly lower NH4+-N contents than the control. The treatment inhibited the activity of nitrifying microorganisms and, thus it decreased the NO3–-N content in Tepedibi, Karaçakl, and Kaba soils, whereas the NO3–-N content was increased in Balar soil. The NO2–-N content of soils was not affected by the treatment. The activity of denitrifying bacteria was stimulated by the addition of herbicide in all soils, whereas the total number of bacteria was not influenced. It may be concluded that the effects of Topogard on the microbiological characteristics of coarse-textured soils are likely to be dependent on soil pH.  相似文献   

14.
The 13C and 15N values of sugarcane plant tissues, decomposing harvest residues, soil and the casts and body tissues of the earthwormPontoscolex corethrurus were determined. Little variation in 13C values was found between plant parts. The 13C values of the decomposing harvest residues declined and became more variable after 148 days of exposure in the field. In the decomposing residues, 13C values of the neutral detergent fibre fraction were similar to those of the whole tissues while those of the proximate lignin were more negative. The 15N values of the residues also declined over time after a short initial delay.P. corethrurus populations are more intimately associated with the roots of sugarcane than with the bulk soil. Tissue 13C values suggest that the earthworm diet is similar to or more enriched in13C than sugarcane tissues and is substantially more enriched than the soil C. Earthworm tissues have similar levels of15N enrichment to both the soil and plant tissues. These data are consistent with the hypothesis that this earthworm derives much of its assimilated C relatively directly from organic matter associated with the roots and decomposing harvest residues.  相似文献   

15.
Summary Hexaploid wheat varieties are often differentiated by reciprocal translocations. The chromosomes involved are frequently identified after crossing and F1 analysis. The hybrids show in meiosis multivalent configurations of 14, 24, 34, 16, 18, 14+16, and 24+16 with different frequencies. For several studies the knowledge about interchanges is required. Therefore, a list was compiled summarizing available data from 270 wheat combinations on the presence and number of translocations, on configurations observed and on chromosomes involved.
Ein Kompendium reziproker Translokationen beim hexploiden Weizen
Zusammenfassung Sorten und Linien des hexaploiden Weizens unterscheiden sich sehr häufig durch die Präsenz reziproker chromosomaler Translokationen. Sie können in F1-Hybriden durch die Bildung von multivalenten Chromosomenkonfigurationen identifiziert werden. Unter etwa 270 analysierten Kombinationen wurden Assoziationen von 14, 24, 34, 16, 18, 14+16 und 24+16 mit unterschiedlichen Frequenzen beobachtet. Für verschiedenartige genetische und cytogenetische Experimente ist die Kenntnis über das Vorkommen derartiger Strukturaberrationen erforderlich. Es wurde daher eine Liste verfügbarer Literaturdaten zusammengestellt, die die karyologischen Befunde die Sortenangaben und deren Herkunft sowie die in die Translokation involvierten Chromosomen bzw. Chromosomenarme beinhaltet. Die Ergebnisse werden diskutiert.
. . 270 14, 24, 34, 16, 18, 16+14 24+16 . ¶rt; . , , , , . .
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16.
The cell content of 12 bacterial phospholipid fatty acids (PLFA) was determined in bacteria extracted from soil by homogenization/centrifugation. The bacteria were enumerated using acridine orange direct counts. An average of 1.40×10-17 mol bacterial PLFA cell-1 was found in bacteria extracted from 15 soils covering a wide range of pH and organic matter contents. With this factor, the bacterial biomass based on PLFA analyses of whole soil samples was calculated as 1.0–4.8 mg bacterial C g-1 soil C. The corresponding range based on microscopical counts was 0.3–3.0 mg bacterial C g-1 soil C. The recovery of bacteria from the soils using homogenization/centrifugation was 2.6–16% (mean 8.7%) measured by PLFA analysis, and 12–61% (mean 26%) measured as microscopical counts. The soil content of the PLFA 18:26 was correlated with the ergosterol content (r=0.92), which supports the use of this PLFA as an indicator of fungal biomass. The ratio 18:26 to bacterial PLFA is therefore suggested as an index of the fungal:bacterial biomass ratio in soil. An advantage with the method based on PLFA analyses is that the same technique and even the same sample is used to determine both fungi and bacteria. The fungal:bacterial biomass ratio calculated in this way was positively correlated with the organic matter content of the soils (r=0.94).  相似文献   

17.
Zusammenfassung In Nährlösung nach Bonner und Addicott (1937) wurde der Einfluß hoher Konzentrationen von Penicillin G (1,5 · 10–3 bis 6 · 10–3 g/ml) auf Aufnahme und Einbau von35S-Methionin in das Eiweiß verschiedener Entwicklungsabschnitte isolierter Wurzeln von Erbsenkeimlingen untersucht. Die Methionin-Aufnahme wurde bei den drei Wurzelsegmenten übereinstimmend durch 6 · 10–3 g Penicillin je ml Nährlösung leicht gehemmt und durch 1,5 und 3 · 10–3 g/ml gefördert, und zwar durch die schwächere Konzentration am stärksten. Die absolute Größe des Methionin-Einbaus in das Eiweiß der Wurzelzellen und die darin erreichte spezifische Methionin-Markierung werden durch das Penicillin noch weniger beeinflußt als die Stoffaufnahme. Bei Einwirkung von Penicillinmengen, die das Wurzelwachstum stark herabsetzen, weicht die Intensität des Stoffeinbaus von den unbehandelten Kontrollen (ohne Penicillin) nur unerheblich ab.
Summary In nutrient solutions (Bonner and Addicott 1937) the influence of high concentrations of penicillin G (1,5 · 10–3 up to 6 · 10–3 g/ml) was investigated upon uptake and incorporation of35S-methionine into the proteins in segments of different developmental stage of isolated roots of pea seedlings. In all three root segments uptake of methionine was slightly depressed by 6 · 10–3 g penicillin per ml nutrient solution, and stimulated by 1,5 · 10–3 and 3 · 10–3 g/ml, most strongly by the weaker concentration. The absolute quantity of methionine incorporation into proteins of root cells and the specific methionine activity reached within these cells are less influenced by penicillin than the uptake. In solutions with penicillin quantities strongly inhibiting root growth the intensity of methionine incorporation differs but insignificantly from that of tests without penicillin.
(1937) G ( 1,5 · 10–3 6 · 10–3 / 35S- . : 6 · 10–3 , 1,5 3 · 10–3 / -; . «» , , , . , , ( ).
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18.
Soils from 38 German forest sites, dominated by beech trees (Fagus sylvatica L.) were sampled to a depth of about 10 cm after careful removal of overlying organic layers. Microbial biomass N and C were measured by fumigation-extraction. The pH of the soils varied between 3.5 and 8.3, covering a wide range of cation exchange capacity, organic C, total N, and soil C:N values. Maximum biomass C and biomass N contents were 2116 g C m-2 and 347 g N m-2, while minimum contents were 317 and 30 g m-2, respectively. Microbial biomass N and C were closely correlated. Large variations in microbial biomass C:N ratios were observed (between 5.4 and 17.3, mean 7.7), indicating that no simple relationship exists between these two parameters. The frequency distribution of the parameters for C and N availability to the microflora divided the soils into two subgroups (with the exception of one soil): (1) microbial: organic C>12 mg g-1, microbial:total N>28 mg g-1 (n=23), a group with high C and N availability, and (2) microbial:organic C12 mg g-1, microbial:total N28 mg g-1 (n=14), a group with low C and N availability. With the exception of a periodically waterlogged soil, the pH of all soils belonging to subgroup 2 was below 5.0 and the soil C:N ratios were comparatively high. Within these two subgroups no significant correlation between the microbial C:N ratio and soil pH or any other parameter measured was found. The data suggest that above a certain threshold (pH 5.0) microbial C:N values vary within a very small range over a wide range of pH values. Below this threshold, in contrast, the range of microbial C:N values becomes very large.  相似文献   

19.
Zusammenfassung In der vorliegenden Arbeit werden Modelle für die Anreicherung des Kohlenstoffatoms12C gegenüber13C bei der Photosynthese von C3- und C4-Pflanzen beschrieben und im Zusammenhang mit Literaturdaten zum Einfluß innerer und äußerer Faktoren auf diesen Vorgang diskutiert. Bei den C3-Pflanzen wird die Isotopendiskriminierung durch das Verhältnis der Geschwindigkeiten des Transports von CO2 in das Blatt und der Carboxylierung des Ribulose-1,5-bisphosphats (RuBP) bestimmt. Ausdruck dieses Zusammenhangs ist eine vonFarquhar (1980) angegebene lineare Beziehung zwischen 13C-Wert und dem Verhältnis von interzellulärer und äußerer CO2-Konzentration. Die Isotopendiskriminierung bei der C4-Photosynthese ist ebenfalls von den Geschwindigkeiten der Diffusion von CO2 in das Blatt und der primären Carboxylierung von Phosphoenolpyruvat (PEP) abhängig. Wegen der unvermeidlichen Verluste von CO2 aus den Leitbündelscheidenzellen sind aber auch die sekundäre Carboxylierung von RuBP und der CO2-Transport innerhalb des Blattes zu berücksichtigen. Ein auf dieser Grundlage entwickeltes Modell, das im Gegensatz zu einem früher beschriebenen Ansatz auch die CO2-Abhängigkeit der Geschwindigkeitsparameter für die Carboxylierungsschritte einschließlich der Limitierung der PEP-Carboxylierung durch die PEP-Regenerationsrate berücksichtigt, wird ausführlich dargestellt. Nach diesem Modell können die wenigen bisher bekannten Befunde zum Einfluß hoher CO2-Konzentrationen auf die Isotopendiskriminierung von C4-Pflanzen als Hinweis darauf interpretiert werden, daß der Isotopeneffekt der RuBP-Carboxylierung bei den C4-Pflanzen möglicherweise größer ist als bei den C3-Pflanzen.
Models of carbon isotope discrimination during photosynthesis of C3 and C4 plants
Summary Models of fractionation of carbon atoms12C and13C during photosynthesis of C3 and C4 plants are described and discussed with regard to the influence of internal and external factors on this process. Isotope discrimination in C3 plants is determined by the ratio of the rates of CO2 transfer into the leaf and carboxylation of ribulose-1,5-bisphosphate (RuBP). This relationship can be expressed by a linear equation between 13C value and the ratio of intercellular and external CO2 concentration as proposed byFarquhar (1980). Carbon isotope discrimination by C4 photosynthesis also depends on the rates of CO2 diffusion into the leaf and of primary carboxylation of phosphoenolpyruvate (PEP). However, because of the unavoidable losses of CO2 from bundle sheath cells the secondary carboxylation of RuBP as well as CO2 transfer processes within the leaf must be taken into account, too. A model based on these features is explained in some detail. In contrast to a model proposed earlier the presented model considers the dependence on CO2 concentration of rate parameters for the carboxylation steps including limitation of PEP carboxylation by PEP regeneration rate. According to the model the spare experimental results on the influence of high concentrations of CO2 on carbon isotope discrimination in C4 plants may be interpreted as an indication that the isotope effect of RuBP carboxylation in C4 plants could be higher than in C3 plants.
3 - 4 -
12 13 3 4 , , . 3- 2 -1,5- (). , (1980), 13 2. 4 2 (). 2 , 2 . , , , , 2, . , , , 2 4-, , 4 -, , , 3-.
Herrn Prof. Dr.K. Unger anläßlich der 65. Wiederkehr seines Geburtstages gewidmet.  相似文献   

20.
Summary The variability of 19 seed characters has been examined for 52 species of the genusVicia. Seed circumference, relative hilum length, hilum shape and lens position could be confirmed as the most relevant characters for grouping. By cluster analyses based upon them the material has been classified into 11 groups. Discriminant analyses gave 25 % misclassifications when all 19 variables were subjected to the analysis for the determination of individual seeds. A key for determination of the species has been proposed mainly by means of quantitative seed characters; dendrograms illustrate the result of the cluster analyses and seed diagrams show schematically important seed characters.
Die Variabilität von Samenmerkmalen bei ausgewähltenVicia-Arten
Zusammenfassung Es wurde die Variabilität von 19 Samenmerkmalen bei 52 Arten der GattungVicia geprüft. Für eine Gruppenbildung bestätigten sich dabei der Samenumfang, die relative Nabellänge, die Nabelform und die Lage der Chalaza als besonders geeignet. Bei einer auf diesen Merkmalen aufbauenden Cluster-Analyse konnten innerhalb des Untersuchungsmaterials 11 Artengruppen ausgeschieden werden. Diskriminanz-Analysen unter Verwendung von allen 19 Variablen ergaben eine Fehlklassifikation beim Versuch der Zuordnung einzelner Samen in 25 % der Fälle. Ein Schlüssel zum Bestimmen der Arten vorzugsweise an Hand von quantitativen Samenmerkmalen wurde vorgeschlagen. Dendrogramme illustrieren die Ergebnisse der Cluster-Analysen und schematische Samendiagramme die Ausprägung der relevanten Samenmerkmale.
Vicia
19 52 Vicia. : , , . , , 11 . , 19 25 % . , . , — .
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