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1.
The stable carbon and oxygen isotope ratios in cellulose of C3 and C4 plants growing on the surface of a montane peat bog
in the Nilgiri hills, southern India, were measured. The mean monthly δ13C values in cellulose of both C3 and C4 plants are found to be significantly related to rainfall, while the δ18O values are sensitive to changes in maximum temperature and relative humidity of the region. Further, higher δ18O values were observed in C4 plants compared to C3 plants, suggesting that C4 plants are probably less sensitive to relative
humidity as compared to C3 plants and are able to photosynthesize even during drier conditions. The plant isotope-climate
correlations thus established can be used for reconstructing the past temperature and rainfall conditions of the tropics from
the isotopic ratios of peat deposits, derived from a mixture of C3 and C4 plants in the region. 相似文献
2.
Carbon: freshwater plants 总被引:15,自引:1,他引:14
δ13C values for freshwater aquatic plant matter varies from ?11 to ?50‰ and is not a clear indicator of photosynthetic pathway as in terrestrial plants. Several factors affect δ13C of aquatic plant matter. These include: (1) The δ13C signature of the source carbon has been observed to range from +1‰ for HCO3? derived from limestone to ?30‰ for CO2 derived from respiration. (2) Some plants assimilate HCO3?, which is –7 to –11‰ less negative than CO2. (3) C3, C4, and CAM photosynthetic pathways are present in aquatic plants. (4) Diffusional resistances are orders of magnitude greater in the aquatic environment than in the aerial environment. The greater viscosity of water acts to reduce mixing of the carbon pool in the boundary layer with that of the bulk solution. In effect, many aquatic plants draw from a finite carbon pool, and as in terrestrial plants growing in a closed system, biochemical discrimination is reduced. In standing water, this factor results in most aquatic plants having a δ13C value similar to the source carbon. Using Farquhar's equation and other physiological data, it is possible to use δ13C values to evaluate various parameters affecting photosynthesis, such as limitations imposed by CO2 diffusion and carbon source. 相似文献
3.
The origin of carbon in the spores of arbuscular mycorrhizal (AM) fungi was quantified based on their obligate symbiosis
with C3 and C4 plants showing clearly different δ13C values. The δ13C values of individual spores of the AM fungus Gigaspora margarita were analyzed. In monoculture pots of a C3 or a C4 plant species, spore δ13C values were ca. 3.5‰ lower than those of host roots. In coculture pots of a C3 and a C4 plant species, spore δ13C values varied between those of the roots of C3 and C4 plants, and increased linearly from the C3 to the proximity of the C4 plant (P<0.01). This reflects the higher δ13C values in C4 plants than in C3 plants. Thus the carbon origin of G. margarita spores changed with growth state and combination of host plants. In the presence of fresh plant residue instead of living
host plants, spore δ13C values did not vary with distance from the residue. This finding supports the current view that AM fungi are obligate symbionts.
Accepted: 12 February 1999 相似文献
4.
Plant Effects on Spatial and Temporal Patterns of Nitrogen Cycling in Shortgrass Steppe 总被引:6,自引:0,他引:6
Because of the water-limited nature and discontinuous plant cover of shortgrass steppe, spatial patterns in ecosystem properties
are influenced more by the presence or absence of plants than by plant type. However, plant type may influence temporal patterns
of nutrient cycling between plant and soil. Plants having the carbon-3 (C3) or carbon-4 (C4) photosynthetic pathway differ in phenology as well as other attributes that affect nitrogen (N) cycling. We estimated net
N mineralization rates and traced nitrogen-15 (15N) additions among plant and soil components during May, July, and September of 1995 in native plots of C3 plants, C4 plants, or mixtures of C3 and C4. Net N mineralization was significantly greater in C3 plots than in C4 plots during both July and September. C3 plots retained significantly more 15N in May than did mixed and C4 plots; these differences in
15N retention were due to greater 15N uptake by C3 plants than by C4 plants during May. There were no significant differences in total 15N retention among plant communities for July and September. Soil 15N was influenced more by presence or absence of plants than by type of plant; greater quantities of
15N remained in soil interspaces between plants than in soil directly under plants for July and September. Our results indicate
that plant functional type (C3 versus C4) can affect both the spatial and the temporal patterns of N cycling in shortgrass steppe. Further research is necessary to
determine how these intraseasonal differences translate to longer-term and coarser-scale effects of plants on N cycling, retention,
and storage.
Received 8 December 1997; accepted 6 May 1998. 相似文献
5.
R. LEUNING 《Plant, cell & environment》1995,18(4):339-355
Gas-exchange measurements on Eucalyptus grandis leaves and data extracted from the literature were used to test a semi-empirical model of stomatal conductance for CO2 gSc=go+a1A/(cs-I) (1+Ds/Do)] where A is the assimilation rate; Ds and cs are the humidity deficit and the CO2 concentration at the leaf surface, respectively; g0 is the conductance as A → 0 when leaf irradiance → 0; and D0 and a1 are empirical coefficients. This model is a modified version of gsc=a1A hs/cs first proposed by Ball, Woodrow & Berry (1987, in Progress in Photosynthesis Research, Martinus Mijhoff, Publ., pp. 221–224), in which hs is relative humidity. Inclusion of the CO2 compensation point, τ, improved the behaviour of the model at low values of cs, while a hyperbolic function of Ds for humidity response correctly accounted for the observed hyperbolic and linear variation of gsc and ci/cs as a function of Ds, where Ci is the intercellular CO2 concentration. In contrast, use of relative humidity as the humidity variable led to predictions of a linear decrease in gsc and a hyperbolic variation in ci/cs as a function of Ds, contrary to data from E. grandis leaves. The revised model also successfully described the response of stomata to variations in A, Ds and cs for published responses of the leaves of several other species. Coupling of the revised stomatal model with a biochemical model for photosynthesis of C3 plants synthesizes many of the observed responses of leaves to light, humidity deficit, leaf temperature and CO2 concentration. Best results are obtained for well-watered plants. 相似文献
6.
Question: The relationship between carbon‐13 in soil organic matter and C3 and C4 plant abundance is complicated because of differential productivity, litter fall and decomposition. As a result, applying a mass balance equation to δ13C data from soils cannot be used to infer past C3 and C4 plant abundance; only the proportion of carbon derived from C3 and C4 plants can be estimated. In this paper, we compare δ13C of surface soil samples with vegetation data, in order to establish whether the ratio of C3:C4 plants (rather than the proportion of carbon from C3 and C4 plants) can be inferred from soil δ13C. Location: The Tsavo National Park, in southeastern Kenya. Methods: We compare vegetation data with δ13C of organic matter in surface soil samples and derive regression equations relating the δ13C of soil organic matter to C3:C4 plant abundance. We use these equations to interpret δ13C data from soil profiles in terms of changes in inferred C3:C4 plant ratio. We compare our method of interpretation with that derived from a mass balance approach. Results: There was a statistically significant, linear relationship between the δ13C of organic matter in surface soil samples and the natural logarithm of the ratio of C3:C4 plants in the 100m2 surrounding the soil sample. Conclusions: We suggest that interpretation of δ13C data from organic matter in soil profiles can be improved by comparing vegetation surveys with δ13C of organic matter in surface soil samples. Our results suggest that past C3 plant abundance might be under‐estimated if a mass balance approach is used. 相似文献
7.
Relative humidity- and ABA-induced variation in carbon and oxygen isotope ratios of cotton leaves 总被引:21,自引:4,他引:17
Cotton (Gossypium hirsutum L. cv. CS50) plants were grown at two levels of relative humidity (RH) and sprayed daily with abscisic acid (ABA) at four concentrations. Plants grown at lower humidity had higher transpiration rates, lower leaf temperatures and lower stomatal conductance. Plant biomass was also reduced at low humidity. Within each humidity environment, increasing ABA concentration generally reduced stomatal conductance, evaporation rates, superficial leaf density and plant biomass, and increased leaf temperature and specific leaf area. As expected, decreased stomatal conductance resulted in decreased carbon isotope discrimination in leaf material ( Δ 13Cl). Plants grown at low humidity were more enriched in 18O than those grown at high RH, as theory predicts. Within each humidity environment, increasing ABA concentration increased oxygen isotope enrichment of leaf cellulose ( Δ 18Oc) and whole‐leaf tissue ( Δ 18Ol). Values of Δ 13Cl and Δ 18Ol predicted by theoretical models were close to those observed, accounting for 79% of the measured variation in Δ 13Cl and 95% of the measured variation in Δ 18Ol. Supporting theory, Δ 13Cl and Δ 18Ol in whole‐leaf tissue were negatively related. 相似文献
8.
C4 photosynthesis in a single C3 cell is theoretically inefficient but may ameliorate internal CO2 diffusion limitations of C3 leaves 总被引:2,自引:1,他引:1
S. VON CAEMMERER 《Plant, cell & environment》2003,26(8):1191-1197
Attempts are being made to introduce C4 photosynthetic characteristics into C3 crop plants by genetic manipulation. This research has focused on engineering single‐celled C4‐type CO2 concentrating mechanisms into C3 plants such as rice. Herein the pros and cons of such approaches are discussed with a focus on CO2 diffusion, utilizing a mathematical model of single‐cell C4 photosynthesis. It is shown that a high bundle sheath resistance to CO2 diffusion is an essential feature of energy‐efficient C4 photosynthesis. The large chloroplast surface area appressed to the intercellular airspace in C3 leaves generates low internal resistance to CO2 diffusion, thereby limiting the energy efficiency of a single‐cell C4 concentrating mechanism, which relies on concentrating CO2 within chloroplasts of C3 leaves. Nevertheless the model demonstrates that the drop in CO2 partial pressure, pCO2, that exists between intercellular airspace and chloroplasts in C3 leaves at high photosynthetic rates, can be reversed under high irradiance when energy is not limiting. The model shows that this is particularly effective at lower intercellular pCO2. Such a system may therefore be of benefit in water‐limited conditions when stomata are closed and low intercellular pCO2 increases photorespiration. 相似文献
9.
C4 plants are rare in the cool climates characteristic of high latitudes and altitudes, perhaps because of an enhanced susceptibility to photo‐inhibition at low temperatures relative to C3 species. In the present study we tested the hypothesis that low‐temperature photo‐inhibition is more detrimental to carbon gain in the C4 grass Muhlenbergia glomerata than the C3 species Calamogrostis Canadensis. These grasses occur together in boreal fens in northern Canada. Plants were grown under cool (14/10 °C day/night) and warm (26/22 °C) temperatures before measurement of the light responses of photosynthesis and chlorophyll fluorescence at different temperatures. Cool growth temperatures led to reduced rates of photosynthesis in M. glomerata at all measurement temperatures, but had a smaller effect on the C3 species. In both species the amount of xanthophyll cycle pigments increased when plants were grown at 14/10 °C, and in M. glomerata the xanthophyll epoxidation state was greatly reduced. The detrimental effect of low growth temperature on photosynthesis in M. glomerata was almost completely reversed by a 24‐h exposure to the warm‐temperature regime. These data indicate that reversible dynamic photo‐inhibition is a strategy by which C4 species may tolerate cool climates and overcome the Rubisco limitation that is prevalent at low temperatures in C4 plants. 相似文献
10.
Effect of host shoot clipping on carbon and nitrogen sources for arbuscular mycorrhizal fungi 总被引:2,自引:0,他引:2
The effect of clipping of the host-plant shoot on the sources of carbon and nitrogen for the arbuscular mycorrhizal (AM) fungus Gigaspora margarita was determined by measuring 13C in spores and hyphae in cocultures of C3 and C4 plants and by differential 15N labeling. C3 and C4 plants, which have different δ13C values, were grown in the same container separated by a series of hyphal compartments. The C3 and C4 plants were applied with 14N- and 15N-urea, respectively. After clipping of the C3 shoots, spore δ
13C gradually approached that of the C4 roots. Hyphal δ
13C paralleled that of spores. Spore % 15N was similar to that of mineral N in the C4 plant compartment. Thus C in G. margarita coming from the clipped plants decreased with time. This demonstrates that C in AM fungi comes from living plants, whilst
the N in spores comes mostly from the soil.
Accepted: 28 November 2000 相似文献
11.
Root exudation (net efflux of amino acids) may increase rhizodeposition under elevated CO2 总被引:2,自引:0,他引:2
Increases in atmospheric CO2 concentration ([CO2]) can lead to global climate change and theoretically could enhance carbon (C) deposition in soil, but data on this complex issue are contradictory. One approach for clarifying the diverse forces influencing plant‐derived C in the rhizosphere involves defining how elevated [CO2] alters the fundamental process of C transfer from plant roots to the soil. We examine here how a step increase in [CO2] affects the innate influx and efflux components of root exudation in axenic plants, as one foundation for understanding how climate change may affect rhizodeposition. Increasing [CO2] from 425 to 850 μmol mol?1 during short‐term trials enhanced shoot and root dry weight (P<0.01) of annual rye grass (Lolium multiflorum Lam.) and medic (Medicago truncatula L.) but had no effect on growth of maize (Zea mays L.). Root amino‐acid flux in the same plants changed only in maize, which increased the efflux rate (nmol g root fresh weight?1 h?1) of six amino acids (arginine, alanine, proline, tyrosine, lysine and leucine) significantly (P<0.05) under elevated [CO2]. None of the three plant species altered the steady‐state concentration of 16 amino acids released into a hydroponic solution with changing [CO2], apparently because amino‐acid influx rates, measured at 2.5 μm , consistently exceeded efflux rates. Indeed, plants recovered amino acids at rates 94–374% higher than they were lost from roots regardless of [CO2]. These results indicate that, in theory, any effect of [CO2] doubling on amino‐acid efflux can be offset by innately higher rates of influx. In practice, however, higher rates of amino‐acid cycling (i.e., efflux+influx) for each root segment (in C4 maize) or from more root tissue (in the two C3 species) should increase root exudation by plants exposed to elevated [CO2] as additional amino acids would be adsorbed to soil particles or be taken up by soil microorganisms. 相似文献
12.
Studies in temperate grassland ecosystems have shown that differences in composition of C3 and C4 plant functional types can have important influences on ecosystem pools and processes. We used a plant community dynamics
model (STEPPE) linked to a biogeochemical cycling model (CENTURY) to determine how ecosystem properties in shortgrass steppe
are influenced by plant functional type composition. Because of phenological differences between C3 and C4 plants, we additionally simulated the effects of precipitation seasonality on plant communities and examined how C3 and C4 composition interacts with precipitation to affect ecosystems. The model output suggests that differences in C3 and C4 composition can lead to differences in soil organic carbon (C) and nitrogen (N) within 1000 simulation years. Soil organic
C and N (g C and N m−
2 to 0.2-m depth) were least in a 100% C4 community compared with a 100% C3 community and a mixed C3–C4 community. A change in the time of maximum precipitation from summer to spring in a simulated shortgrass steppe slightly
favored C3 plants over C4 plants. The proportion of total net primary production accounted for by C3 plants increased from 21% to 25% after 200 years, when 90 mm of precipitation was switched from summer to spring. Soil organic
matter (SOM) was relatively stable in the C4-dominated communities with respect to changes in precipitation seasonality, whereasSOM in the C3 community was sensitive to precipitation seasonality changes. These results suggest an important interaction between plant
community composition and precipitation seasonality on SOM, with phenology playing a key role.
Received 9 June 1998; accepted 6 January 1999 相似文献
13.
Hydrogen isotopic differences between C3 and C4 land plant lipids: consequences of compartmentation in C4 photosynthetic chemistry and C3 photorespiration
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Youping Zhou Kliti Grice Hilary Stuart‐Williams Charles H. Hocart Arthur Gessler Graham D. Farquhar 《Plant, cell & environment》2016,39(12):2676-2690
The 2H/1H ratio of carbon‐bound H in biolipids holds potential for probing plant lipid biosynthesis and metabolism. The biochemical mechanism underlying the isotopic differences between lipids from C3 and C4 plants is still poorly understood. GC‐pyrolysis‐IRMS (gas chromatography‐pyrolysis‐isotope ratio mass spectrometry) measurement of the 2H/1H ratio of leaf lipids from controlled and field grown plants indicates that the biochemical isotopic fractionation (ε2Hlipid_biochem) differed between C3 and C4 plants in a pathway‐dependent manner: ε2HC4 > ε2HC3 for the acetogenic pathway, ε2HC4 < ε2HC3 for the mevalonic acid pathway and the 1‐deoxy‐D‐xylulose 5‐phosphate pathway across all species examined. It is proposed that compartmentation of photosynthetic CO2 fixation into C4 mesophyll (M) and bundle sheath (BS) cells and suppression of photorespiration in C4 M and BS cells both result in C4 M chloroplastic pyruvate – the precursor for acetogenic pathway – being more depleted in 2H relative to pyruvate in C3 cells. In addition, compartmentation in C4 plants also results in (i) the transferable H of NADPH being enriched in 2H in C4 M chloroplasts compared with that in C3 chloroplasts for the 1‐deoxy‐D‐xylulose 5‐phosphate pathway pathway and (ii) pyruvate relatively 2H‐enriched being used for the mevalonic acid pathway in the cytosol of BS cells in comparison with that in C3 cells. 相似文献
14.
Rhizosphere priming effects on the decomposition of soil organic matter in C4 and C3 grassland soils 总被引:1,自引:0,他引:1
Using a natural abundance 13C method, soil organic matter (SOM) decomposition was studied in a C3 plant – `C4 soil' (C3 plant grown in a soil obtained from a grassland dominated by C4 grasses) system and a C4 plant – `C3 soil' (C4 plant grown in a soil taken from a pasture dominated by C3 grasses) system. In C3 plant – `C4 soil' system, cumulative soil-derived CO2–C were higher in the soils planted with soybean (5499 mg pot–1) and sunflower (4484 mg pot–1) than that in `C4 soil' control (3237 mg pot–1) without plants. In other words, the decomposition of SOM in soils planted with soybean and sunflower were 69.9% and 38.5% faster than `C4 soil' control. In C4 plant – `C3 soil' system, there was an overall negative priming effect of live roots on the decomposition of SOM. The cumulative soil-derived CO2–C were lower in the soils planted with sorghum (2308 mg pot–1) and amaranthus (2413 mg pot–1) than that in `C3 soil' control (2541 mg pot–1). The decomposition of SOM in soils planted with sorghum and amaranthus were 9.2% and 5.1% slower than `C3 soil' control. Our results also showed that rhizosphere priming effects on SOM decomposition were positive at all developmental stages in C3 plant – `C4 soil' system, but the direction of the rhizosphere priming effect changed at different developmental stages in the C4 plant – `C3 soil' system. Implications of rhizosphere priming effects on SOM decomposition were discussed. 相似文献
15.
Lucas C. R. Silva Melisa A. Giorgis Madhur Anand Lucas Enrico Natalia P��rez-Harguindeguy Valeria Falczuk Larry L. Tieszen Marcelo Cabido 《Plant and Soil》2011,349(1-2):261-279
Aim
Millennial-scale biogeographic changes are well understood in many parts of the world, but little is known about long-term vegetation dynamics in subtropical regions. Here we investigate shifts in C3/C4 plant abundance occurred in central Argentina during the past few millenniaMethods
We determined present day soil organic matter ??13C signatures of grasslands, shrublands and woodlands, containing different mixtures of C3 and C4 plants. We measured past changes in the relative cover of C3/C4 plants by comparing ??13C values in soil profiles with present day ??13C signatures. We analyzed 14C activity in soil depths that showed major changes in vegetation.Results
Present day relative cover of C3/C4 plants determines whole ecosystem ??13C signatures integrated as litter and superficial soil organic matter (R2?=?0.78; p?<?0.01). Deeper soils show a consistent shift in ??13C, indicating a continuous replacement of C4 by C3 plants since 3,870 (±210) YBP. During this period, the relative abundance of C3 plants increased 32% (average across sites) with significant changes being observed in all studied ecosystems.Conclusions
Our results show that C4 species were more abundant in the past, but C3 species became dominant during the late Holocene. We identified increases in the relative C3/C4 cover in grasslands, shrublands and woodlands, suggesting a physiological basis for changes in vegetation. The replacement of C4 by C3 plants coincided with changes in climate towards colder and wetter conditions and could represent a climatically driven shift in the C4 species optimum range. 相似文献16.
Elevated CO2 and plant nitrogen-use: is reduced tissue nitrogen concentration size-dependent? 总被引:1,自引:0,他引:1
Plants often respond to elevated atmospheric CO2 levels with reduced tissue nitrogen concentrations relative to ambient CO2-grown plants when comparisons are made at a common time. Another common response to enriched CO2 atmospheres is an acceleration in plant growth rates. Because plant nitrogen concentrations are often highest in seedlings and subsequently decrease during growth, comparisons between ambient and elevated CO2-grown plants made at a common time may not demonstrate CO2-induced reductions in plant nitrogen concentration per se. Rather, this comparison may be highlighting differences in nitrogen concentration between bigger, more developed plants and smaller, less developed plants. In this study, we directly examined whether elevated CO2 environments reduce plant nitrogen concentrations independent of changes in plant growth rates. We grew two annual plant species. Abutilon theophrasti (C3 photosynthetic pathway) and Amaranthus retroflexus (C4 photosynthetic pathway), from seed in glass-sided growth chambers with atmospheric CO2 levels of 350 mol·mol–1 or 700 mol·mol–1 and with high or low fertilizer applications. Individual plants were harvested every 2 days starting 3 days after germination to determine plant biomass and nitrogen concentration. We found: 1. High CO2-grown plants had reduced nitrogen concentrations and increased biomass relative to ambient CO2-grown plants when compared at a common time; 2. Tissue nitrogen concentrations did not vary as a function of CO2 level when plants were compared at a common size; and 3. The rate of biomass accumulation per rate of increase in plant nitrogen was unaffected by CO2 availability, but was altered by nutrient availability. These results indicate that a CO2-induced reduction in plant nitrogen concentration may not be due to physiological changes in plant nitrogen use efficiency, but is probably a size-dependent phenomenon resulting from accelerated plant growth. 相似文献
17.
Fundamental to our understanding of the ecology of animal communities in the tropics is knowledge of the effect of seasonal changes in the abundance of food sources in consumer diets. We determined stable‐isotope composition (13C/12C and 15N/14N) in whole blood of 14 resident avian species in a tropical dry forest to quantify the origin of their assimilated protein. We used a probabilistic approach (IsoSource) to estimate the relative contribution of C3 plants, CAM‐C4 plants, C3 insects, and CAM‐C4 insects during the dry and rainy seasons. IsoSource iteratively creates each possible combination of source contribution and produces a distribution of all feasible combinations that adequately predict the observed isotopic signature of the consumer. Granivore–frugivores and granivore–frugivore–insectivores were modeled as predominantly dependent upon plants whereas insectivorous birds were modeled to derive protein almost exclusively from insects. Between these extremes there were several species using mixed diets such as insectivore–frugivores or insectivore–granivores. In most species, virtually all assimilated food was of C3 origin with the exception of Ruddy Ground‐Doves (Columbina talpacoti) in which CAM or C4 plants contributed significantly. Seasonal changes in relative food source contribution were followed in eight species of birds. Of these species, White‐tipped Doves (Leptotila verreauxi), Grayish Saltators (Saltator coerulescens), and Social Flycatchers (Myiozetetes similis) increased their use of insects in the rainy season, in contrast to Great Kiskadees (Pitangus sulphuratus), which decreased their use of insects. Our study suggests that that diverse strategies are used by various avian species to obtain dietary proteins within seasonal habitats. 相似文献
18.
Fuller BT De Cupere B Marinova E Van Neer W Waelkens M Richards MP 《American journal of physical anthropology》2012,149(2):157-171
An isotopic reconstruction of human dietary patterns and livestock management practices (herding, grazing, foddering, etc.) is presented here from the sites of Düzen Tepe and Sagalassos in southwestern Turkey. Carbon and nitrogen stable isotope ratios were determined from bone collagen extracted from humans (n = 49) and animals (n = 454) from five distinct time periods: Classical‐Hellenistic (400–200 BC), Early to Middle Imperial (25 BC–300 AD), Late Imperial (300–450 AD), Early Byzantine (450–600 AD), and Middle Byzantine (800–1200 AD). The humans had protein sources that were based on C3 plants and terrestrial animals. During the Classical‐Hellenistic period, all of the domestic animals had δ13C and δ15N signatures that clustered together; evidence that the animals were herded in the same area or kept in enclosures and fed on similar foods. The diachronic analysis of the isotopic trends in the dogs, cattle, pigs, sheep, and goats highlighted subtle but distinct variations in these animals. The δ13C values of the dogs and cattle increased (reflecting C4 plant consumption) during the Imperial and Byzantine periods, but the pigs and the goats displayed little change and a constant C3 plant‐based diet. The sheep had a variable δ13C pattern reflecting periods of greater and lesser consumption of C4 plants in the diet. In addition, the δ15N values of the dogs, pigs, cattle, and sheep increase substantially from the Classical‐Hellenistic to the Imperial periods reflecting a possible increase in protein consumption, but the goats showed a decrease. Finally, these isotopic results are discussed in the context of zooarcheological, archeobotanical, and trace element evidence. Am J Phys Anthropol 149:157–171, 2012. © Wiley Periodicals, Inc. 相似文献
19.
Hydraulic lift among native plant species in the Mojave Desert 总被引:9,自引:1,他引:8
Hydraulic lift was investigated among native plants in the Mojave Desert using in situ thermocouple psychrometers. Night lighting
and day shading experiments were used to verify the phenomenon. Hydraulic lift was detected for all species examined: five
shrub species with different rooting depths and leaf phenologies and one perennial grass species. This study was the first
to document hydraulic lift for a CAM species, Yucca schidigera. The pattern of diel flux in soil water potential for the CAM
species was temporally opposite to that of C3 species: for the CAM plant, soil water potential increased in shallow soils during the day when the plant was not transpiring
and decreased at night when transpiration began. Because CAM plants transport water to shallow soils during the day when surrounding
C3 and C4 plants transpire, CAM species that hydraulically lift water may influence water relations of surrounding species to a greater
extent than hydraulically lifting C3 or C4 species. A strong, negative relationship between the percent sand in the study site soils at the 0.35 m soil depth and the
frequency that hydraulic lift was observed at that depth suggests that the occurrence of hydraulic lift is negatively influenced
by coarse-textured soils, perhaps due to less root–soil contact in sandy soils relative to finer-textured soils. Differences
in soil texture among study sites may explain, in part, differences in the frequency that hydraulic lift was detected among
these species. Further investigations are needed to elucidate species versus soil texture effects on hydraulic lift.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
Carbon isotope fractionation in plants 总被引:7,自引:0,他引:7
Marion H. OLeary 《Phytochemistry》1981,20(4):553-567
Plants with the C3, C4, and crassulacean acid metabolism (CAM) photosynthetic pathways show characteristically different discriminations against 13C during photosynthesis. For each photosynthetic type, no more than slight variations are observed within or among species. CAM plants show large variations in isotope fractionation with temperature, but other plants do not. Different plant organs, subcellular fractions and metabolises can show widely varying isotopic compositions. The isotopic composition of respired carbon is often different from that of plant carbon, but it is not currently possible to describe this effect in detail. The principal components which will affect the overall isotope discrimination during photosynthesis are diffusion of CO2, interconversion of CO2 and HCO?3, incorporation of CO2 by phosphoenolpyruvate carboxylase or ribulose bisphosphate carboxylase, and respiration. Theisotope fractionations associated with these processes are summarized. Mathematical models are presented which permit prediction of the overall isotope discrimination in terms of these components. These models also permit a correlation of isotope fractionations with internal CO2 concentrations. Analysis of existing data in terms of these models reveals that CO2 incorporation in C3 plants is limited principally by ribulose bisphosphate carboxylase, but CO2 diffusion also contributes. In C4 plants, carbon fixation is principally limited by the rate of CO2 diffusion into the leaf. There is probably a small fractionation in C4 plants due to ribulose bisphosphate carboxylase. 相似文献