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1.
Belowground biomass is a critical factor regulating ecosystem functions of coastal marshes, including soil organic matter
(SOM) accumulation and the ability of these systems to keep pace with sea-level rise. Nevertheless, belowground biomass responses
to environmental and vegetation changes have been given little emphasis marsh studies. Here we present a method using stable
carbon isotopes and color to identify root and rhizomes of Schoenoplectus americanus (Pers.) Volk. ex Schinz and R. Keller (C3) and Spartina patens (Ait.) Muhl. (C4) occurring in C3− and C4-dominated communities in a Chesapeake Bay brackish marsh. The functional significance of the biomass classes we identified
is underscored by differences in their chemistry, depth profiles, and variation in biomass and profiles relative to abiotic
and biotic factors. C3 rhizomes had the lowest concentrations of cellulose (29.19%) and lignin (14.43%) and the lowest C:N (46.97) and lignin:N
(0.16) ratios. We distinguished two types of C3 roots, and of these, the dark red C3 roots had anomalously high C:N (195.35) and lignin:N (1.14) ratios, compared with other root and rhizome classes examined
here and with previously published values. The C4-dominated community had significantly greater belowground biomass (4119.1 g m−2) than the C3-dominated community (3256.9 g m−2), due to greater total root biomass and a 3.6-fold higher C3-root:rhizome ratio in the C4-dominated community. C3 rhizomes were distributed significantly shallower in the C4-dominated community, while C3 roots were significantly deeper. Variability in C3 rhizome depth distributions was explained primarily by C4 biomass, and C3 roots were explained primarily by water table height. Our results suggest that belowground biomass in this system is sensitive
to slight variations in water table height (across an 8 cm range), and that the reduced overlap between C3 and C4 root profiles in the C4-dominated community may account for the greater total root biomass observed in that community. Given that future elevated
atmospheric CO2 and accelerated sea-level rise are likely to increase C3 abundance in Atlantic and Gulf coast marshes, investigations that quantify how patterns of C3 and C4 belowground biomass respond to environmental and biological factors stand to improve our understanding of ecosystem-wide
impacts of global changes on coastal wetlands. 相似文献
2.
Summary The nature of the photosynthetic pathways of Cyperaceae found in Japan were investigated on the basis of Kranz anatomy, the CO2 compensation concentration and previously reported data. Among 301 species (96% of all cyperaceous species recorded in the region), 58 species were classified as being C4 plants. These C4 species were scattered among the tribes Fimbristylideae, Lipocarpheae, Cypereae and Rhynchosporeae in the subfamily Cyperoideae. The genera Cyperus, Eleocharis and Rhynchospora included, in Japan, both C3 and C4 species within a single genus. Using these data, an analysis was made of the ecological characteristics and geographical distribution of the C3 and C4 species in Japan. Although cyperaceous species grow in markedly different environments, the majority were found in wet and aquatic areas (61%) or shaded areas, such as forest floors (20%). Most of the C3 species were also hygrophytes (58%) and forest-living species (25%), and C3 species growing in mesic and dry areas were relatively rare. The C4 species inhabited wet and aquatic (75%), mesic (13%) and dry areas (6%) and showed marked ecological characteristics with respect to soil-moisture conditions, unlike other C4 plants, although they were absent from shaded habitats. In order to determine the climatic factors that influence the relative floristic abundance of C3 and C4 members of the Cyperaceae in Japan, the ratios of number of C4 species to the total number of members of Cyperaceae (C4 percentage) in 16 representative locales were examined in terms of various climatic variables. There were strong positive correlations between the C4 percentage and temperature. Among the C3 groups of three subfamilies, there were different distributional trends for various temperature regimes. The C3 subfamily Caricoideae increased its relative contribution to the cyperaceous flora with a decrease in mean annual temperature, while the C3 subfamily Sclerioideae exhibited the opposite pattern. The C3 group of the subfamily Cyperoideae did not show any marked change in pattern along temperature gradients, unlike the two other C3 subfamilies, and seemed to be heterogeneous in terms of its response to temperature. The relationships between the C4 biochemical subtypes and ecological characteristics are also discussed. 相似文献
3.
M. J. Earnshaw K. A. Carver T. C. Gunn K. Kerenga V. Harvey H. Griffiths M. S. J. Broadmeadow 《Oecologia》1990,84(2):280-288
Summary A total of 22 grass species were examined from 5 sites spanning the altitudinal range 1550–4350 m.a.s.l. The presence of the C3 or C4 photosynthetic pathway was determined from 13C values and chilling tolerance was assessed on the basis of electrolyte leakage from leaf slices incubated on melting ice. Most of the grasses studied at the lower altitude sites of 1550 m.a.s.l. (annual mean of daily minimum temperature, 14.6° C) and 2600 m.a.s.l. (9.4° C) possessed C4 photosynthesis and were chill-sensitive. The single except ion was Agrostis avenacea, a montane chill-resistant C3 species which occurred at 2600 m.a.s.l. The three species apparently most sensitive to chilling were Ischaemum polystachyum, Paspalum conjugatum and Saccharum robustum, all occurring at 1550 m.a.s.l. At the higher altitude sites of 3280 (5.6° C), 3580 (4.0° C) and 4350 (–0.7°C) m.a.s.l., most of the grasses exhibited C3 photosynthesis and were chill-resistant. However, an Upland population of the C4 species, Miscanthus floridulus was found at 3280 m.a.s.l. which had acquired chill-resistance as confirmed by additional in vivo variable chlorophyll fluorescence measurements. Cell sap osmotic potential values of the upland grasses at altitudes of 3280–4350 m.a.s.l. were lower (–8.1 to –19.8 bars) than values in grasses from 1550 and 2600 m.a.s.l. (–3.9 to –7.5 bars) due mainly to the presence of non-electrolyte osmoticants, which may be involved in frost avoidance mechanism(s).Abbreviations ABA
abscisic acid
- FR
the maximal rate of rise of induced chlorophyll fluorescence
- s
osmotic potential 相似文献
4.
Glycolate oxidase (GO; EC 1.1.3.1) was purified from the leaves of three plant species:Amaranthus hypochondriacus L.(NAD-ME type C4 dicot),Pisum sativum L. (C3 species) andParthenium hysterophorus L. (C3–C4. intermediate). A flavin moiety was present in the enzyme from all the three species. The enzyme from the C4 plant had a low specific activity, exhibited lower KM for glycolate, and required a lower pH for maximal activity, compared to the C3 enzyme. The enzyme from the C4 species oxidized glyoxylate at <10% of the rate with glycolate, while the GO from the C3 plant oxidized glyoxylate at a rate of about 35 to 40% of that with glycolate. The sensitivity of GO from C4 plant to -hydroxypyridinemethane sulfonate, 2-hydroxy-3-butynoate and other inhibitors was less than that of the enzyme from C3 source. The properties of GO fromParthenium hysterophorus, were similar to those of the enzyme fromPisum sativum. The characteristics of glycolate oxidase from leaves of a C4 plant,Amaranthus hypochondriacus are different from those of the C3 species or the C3–C4 intermediate. 相似文献
5.
Sanjay K. Gupta Maurice S. B. Ku Jenq-Horng Lin Dianzhong Zhang Gerald E. Edwards 《Photosynthesis research》1994,42(2):133-143
In this report, the effects of light on the activity and allosteric properties of phosphoenolpyruvate (PEP) carboxylase were examined in newly matured leaves of several C3 and C4 species. Illumination of previously darkened leaves increased the enzyme activity 1.1 to 1.3 fold in C3 species and 1.4 to 2.3 fold in C4 species, when assayed under suboptimal conditions (pH 7) without allosteric effectors. The sensitivities of PEP carboxylase to the allosteric effectors malate and glucose-6-phosphate were markedly different between C3 and C4 species. In the presence of 5 mM malate, the activity of the enzyme extracted from illuminated leaves was 3 to 10 fold higher than that from darkened leaves in C4 species due to reduced malate inhibition of the enzyme from illuminated leaves, whereas it increased only slightly in C3 species. The Ki(malate) for the enzyme increased about 3 fold by illumination in C4 species, but increased only slightly in C3 species. Also, the addition of the positive effector glucose-6-phosphate provided much greater protection against malate inhibition of the enzyme from C4 species than C3 species. Feeding nitrate to excised leaves of nitrogen deficient plants enhanced the degree of light activation of PEP carboxylase in the C4 species maize, but had little or no effect in the C3 species wheat. These results suggest that post-translational modification by light affects the activity and allosteric properties of PEP carboxylase to a much greater extend in C4 than in C3 species. 相似文献
6.
T. R. Wentworth 《Plant Ecology》1983,52(1):21-34
Distributional patterns of C4 plants were investigated in 4 study areas located in se Arizona: granite slopes in the Mule Mountains, limestone slopes in the Mule Mountains, calcareous bajada (alluvial plain) below the Mule Mountains, and limestone slopes in the Huachuca Mountains. Cover data for all vascular species were obtained from 238 0.1 ha (20×50 m) sample quadrats located over ranges of elevation and topographic position within the study areas. Overall, 69 C4 species representing 6 angiosperm families were encountered. C4 species accounted for 13.5% to 22.3% of vascular species within the study areas. C4 species frequency in quadrats (on the basis of all species or of grasses only) increased from mesic to xeric community types in all study areas except the calcareous bajada. Similar, but less consistent, trends were evident in the relative cover contributed by C4 species. In two of the study areas (granite slopes in the Mule Mountains, limestone slopes in the Huachuca Mountains) regression analyses revealed statistically significant trends of C4 species frequency and relative cover along environmental (elevation/solar-irradiation scalar) and compositional (reciprocal averaging ordination) gradients. A lack of consistent trends on limestone slopes in the Mule Mountains may be the result of grazing and/or recent invasion of low-elevation limestone areas by a Chihuahuan Desert flora dominated by C3 dicot shrubs. The calcareous bajada below the Mule Mountains was studied less intensively, but its flora was found to contain the highest frequency of C4 species of the 4 study areas. In contrast, C4 cover on the bajada was low, presumably as a consequence of heavy grazing pressure on the grasses. The results of the present investigation support the prediction that C4 species should be proportionally more successful in habitats characterized by high temperatures, high irradiance and low moisture. 相似文献
7.
The potential for C4 photosynthesis was investigated in five C3-C4 intermediate species, one C3 species, and one C4 species in the genus Flaveria, using 14CO2 pulse-12CO2 chase techniques and quantum-yield measurements. All five intermediate species were capable of incorporating 14CO2 into the C4 acids malate and aspartate, following an 8-s pulse. The proportion of 14C label in these C4 products ranged from 50–55% to 20–26% in the C3-C4 intermediates F. floridana Johnston and F. linearis Lag. respectively. All of the intermediate species incorporated as much, or more, 14CO2 into aspartate as into malate. Generally, about 5–15% of the initial label in these species appeared as other organic acids. There was variation in the capacity for C4 photosynthesis among the intermediate species based on the apparent rate of conversion of 14C label from the C4 cycle to the C3 cycle. In intermediate species such as F. pubescens Rydb., F. ramosissima Klatt., and F. floridana we observed a substantial decrease in label of C4-cycle products and an increase in percentage label in C3-cycle products during chase periods with 12CO2, although the rate of change was slower than in the C4 species, F. palmeri. In these C3-C4 intermediates both sucrose and fumarate were predominant products after a 20-min chase period. In the C3-C4 intermediates, F. anomala Robinson and f. linearis we observed no significant decrease in the label of C4-cycle products during a 3-min chase period and a slow turnover during a 20-min chase, indicating a lower level of functional integration between the C4 and C3 cycles in these species, relative to the other intermediates. Although F. cronquistii Powell was previously identified as a C3 species, 7–18% of the initial label was in malate+aspartate. However, only 40–50% of this label was in the C-4 position, indicating C4-acid formation as secondary products of photosynthesis in F. cronquistii. In 21% O2, the absorbed quantum yields for CO2 uptake (in mol CO2·[mol quanta]-1) averaged 0.053 in F. cronquistii (C3), 0.051 in F. trinervia (Spreng.) Mohr (C4), 0.052 in F. ramosissima (C3-C4), 0.051 in F. anomala (C3-C4), 0.050 in F. linearis (C3-C4), 0.046 in F. floridana (C3-C4), and 0.044 in F. pubescens (C3-C4). In 2% O2 an enhancement of the quantum yield was observed in all of the C3-C4 intermediate species, ranging from 21% in F. ramosissima to 43% in F. pubescens. In all intermediates the quantum yields in 2% O2 were intermediate in value to the C3 and C4 species, indicating a co-function of the C3 and C4 cycles in CO2 assimilation. The low quantum-yield values for F. pubescens and F. floridana in 21% O2 presumably reflect an ineffcient transfer of carbon from the C4 to the C3 cycle. The response of the quantum yield to four increasing O2 concentrations (2–35%) showed lower levels of O2 inhibition in the C3-C4 intermediate F. ramosissima, relative to the C3 species. This indicates that the co-function of the C3 and C4 cycles in this intermediate species leads to an increased CO2 concentration at the site of ribulose-1,5-bisphosphate carboxylase/oxygenase and a concomitant decrease in the competitive inhibition by O2.Abbreviations PEP
phosphoenolpyruvate
- PGA
3-phosphoglycerate
- RuBP
ribulose-1,5-bisphosphate 相似文献
8.
Russell K. Monson 《Oecologia》1989,80(2):215-221
Summary Analyses of carbon-assimilation patterns in response to intercellular CO2 concentrations, and the photosynthetic water-and nitrogen-use efficiencies, were conducted for a C3, a C4, and three C3–C4 species in the genus Flaveria in order to determine some of the advantages and disadvantages of C3–C4 intermediate photosynthesis. Operational intercellular CO2 partial pressures (pi), determined when the atmospheric CO2 partial pressure (pa) was approximately 330 bar, in the C3–C4 species were generally equal to, or greater than, those observed in the C3 species under well-watered or water-stressed conditions. This reflects equal, or lower, water-use efficiencies (WUEs) in the C3–C4 species. The only case in which higher WUEs were observed in the C3–C4 species, compared to the C3 species, was when photosynthesis rates were limited by available nitrogen and were less than 12.5 mol CO2 m-2s-1. At higher photosynthesis rates, the C3–C4 species exhibited lower values of photosynthesis rate for equal values of stomatal conductance (lower WUE), compared to the C3 species. Comparing slopes for the linear regions of the relationship between leaf nitrogen content and net photosynthesis rate (taken as an index of photosynthetic nitrogen-use efficiency, NUE), the C4 species exhibited the highest NUE, followed by the C3–C4 species, F. ramosissima, with the other two C3–C4 species and the C3 species being equal and exhibiting the lowest NUEs. The lack of consistent advantages in NUE and WUE in the C3–C4 species F. pubescens and F. floridana suggest that in some C3–C4
Flaveria species C4-like anatomy and biochemistry do not provide the same gas exchange advantages that we typically attribute to the CO2-concentrating mechanism of fully-expressed C4 plants. 相似文献
9.
Phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) from Flaveria trinervia Mohr (C4), F. floridana Johnston (C3–C4), and F. cronquistii Powell (C3) leaves were compared by electrotransfer blotting/enzyme-linked immunoassay (Western-blot analysis), mobility of the native enzyme in polyacrylamide gels and in isoelectric focusing (IEF) gels, peptide mapping, and in-vitro translation of RNA isolated from each plant. The PEPCases from the C3 and C3–C4 plants were very similar to each other in terms of electrophoretic mobilities on gels and isoenzyme patterns on IEF gels, and identical in peptide mapping. Quantitative differences were noted, however, in that the C3–C4 intermediate plant contained more PEPCase overall and that the relative activity of individual isoenzymes shifted between the C3 and C3–C4 intermediate PEPCases. The PEPCase from the C4 plant had a different isoenzyme pattern, a different peptide map, and was far more abundant than the other two enzymes. Western blot analysis demonstrated the cross-reactivity of PEPCases from all three Flaveria species with antibody raised against maize PEPCase. The results provide evidence, at the molecular level, that supports the view of C3–C4 intermediate species as C3-like plants with some C4-like photosynthetic characteristics, but there are differences from the C3 plant in the quantity and properties of the PEPCase from the C3–C4 intermediate plant.Abbreviations IEF
isoelectric focusing
- kDa
kilodalton
- PEPCase
phosphoenolpyruvate carboxylase
- Rubisco
Ribulose-1,5-bisphosphate carboxylase/oxygenase 相似文献
10.
受损景观是由不同比例的植被斑块组成的镶嵌体,阐明植被斑块的景观结构特征对物种多样性的影响,有助于提高受损景观物种多样性保护。在塞罕坝自然保护区选取38个天然植被斑块,其中包括12个草地、11个灌木林和15个天然次生林。根据光合作用的不同途径将草本物种划分为C_3和C_4功能群。选取斑块面积、形状指数、隔离度指数及每个斑块500 m缓冲区内的森林和草地比例作为景观因子。通过结构方程模型探讨C_3、C_4草本物种丰富度与景观因子的相互关系。斑块面积(2.18—74.06 hm~2)与C_3、C_4草本及总物种丰富度分布格局均具有显著的正相关关系(P0.05),且对C_3草本的影响最大;形状指数(1.06—3.11)、隔离度指数(33.51—327.65)对C_3、C_4草本及总物种丰富度影响不显著(P0.05);C_3、C_4草本及总物种丰富度与毗邻斑块草地比例(4.20%—64.95%)呈正相关,而与森林比例(35.05%—95.80%)呈负相关。研究区斑块面积和毗邻斑块植被构成是影响C_3、C_4草本植物的主要因素。在破碎化景观中保存面积大的天然植被斑块及提高毗邻斑块草地比例是保护关键C_3、C_4草本植物物种的有效途径。 相似文献
11.
Arid regions of Saudi Arabia occupy most of the area of the Arabian Peninsula. These areas are at the meeting position of plants from Mediterranean, Irano-Turanian, Saharo-Arabian, and Sudanian phytogegraphical regions. Geomorphology of the area reveals a wide diversity of landforms including coastal lines, desert plains, and high mountains. Grasses are well represented in the flora of Saudi Arabia and form an appropriate group for studying the relation of grass distribution, chorology, and photosynthetic pathways. In this paper, geographical distribution of C3 and C4 grasses was studied in an area extending between latitude 17°N and latitude 31°N. Two regions were recognized in the study area, namely; a (relatively) cold region north of latitude 24°N with ample winter rainfall, and a hot region south of latitude 24°N with scarce summer rainfall. Work involved field observations and collection of grass species in the study area. Work also depended on published carbon discrimination values of grasses and biochemical analysis of C4 species subtypes. Climatic conditions in the study area vary considerably, and the distribution of grass species was found to follow patterns that reveal adaptive advantages of different photosynthetic pathways. Grass species in the cold northern region with ample winter rainfall are generally C3 grasses belonging mainly to Mediterranean/Irano-Turanean chorotypes. C3 grass species found in the southern hot region were recorded at high altitudes of southern mountains characterized by low temperatures. Grass species recorded at low altitudes in the south hot region with scarce summer rainfall were mainly C4 grasses belonging to Tropical and Saharo-Arabian-Sudanean chorotypes. Pronounced spatial variations of temperature profoundly control the geographical distribution of C3 and C4 grasses. Low temperatures in the northern cold region and at high altitudes of the southern hot region limit the occurrence of C4 grasses and shift the ecological balance in favor of C3 grasses. Results are discussed in terms of heat sensitivity of the CO2 carboxylating enzyme of C3 grasses and high temperature optima for CO2 assimilation of C4 grasses. Results are also discussed in comparison with geographical distribution of grasses in other parts of the world. 相似文献
12.
Species in the Laxa and Grandia groups of the genus Panicum are adapted to low, wet areas of tropical and subtropical America. Panicum milioides is a species with C3 photosynthesis and low apparent photorespiration and has been classified as a C3/C4 intermediate. Other species in the Laxa group are C3 with normal photorespiration. Panicum prionitis is a C4 species in the Grandia group. Since P. milioides has some leaf characteristics intermediate to C3 and C4 species, its photosynthetic response to irradiance and temperature was compared to the closely related C3 species, P. laxum and P. boliviense and to P. prionitis. The response of apparent photosynthesis to irradiance and temperature was similar to that of P. laxum and P. boliviense, with saturation at a photosynthetic photo flux density of about 1 mmol m-2 s-1 at 30°C and temperature optimum near 30°C. In contrast, P. prionitis showed no light saturation up to 2 mmol m-2 s-1 and an optimum temperature near 40°C. P. milioides exhibited low CO2 loss into CO2-free air in the light and this loss was nearly insensitive to temperature. Loss of CO2 in the light in the C3 species, P. laxum and P. boliviense, was several-fold higher than in P. milioides and increased 2- to 5-fold with increases in temperature from 10 to 40°C. The level of dark respiration and its response to temperature were similar in all four Panicum species examined. It is concluded that the low apparent photorespiration in P. milioides does not influence its response of apparent photosynthesis to irradiance and temperature in comparison to closely related C3 Panicum species.Abbreviations AP
apparent photosynthesis
- I
CO2 compensation point
- gl
leaf conductance; gm, mesophyll conductance
- PPFD
photosynthetic photon flux density
- PR
apparent photorespiration rate
- RuBPC
sibulose bisphosphate carboxylase 相似文献
13.
The in-situ inter- and intracellular localization patterns of phosphoenolpyruvate (PEP) and ribulose 1,5-bisphosphate (RuBP) carboxylases in green leaves of severalPanicum species were investigated using an indirect immunofluorescence technique. Four species were examined and compared:P. miliaceum (C4),P. bisulcatum (C3), andP. decipiens andP. milioides (C3–C4 intermediates which have Kranz-like leaf anatomy and reduced photorespiration). In the C4
Panicum, PEP carboxylase was located in the cytosol of the mesophyll cells and RuBP carboxylase was restricted to the bundle-sheath chloroplasts. In contrast, in the C3
Panicum species, PEP carboxylase was found throughout the leaf chlorenchyma, in both the cytosol and chloroplasts, and RuBP carboxylase was located in the chloroplasts. For the C3–C4 intermediate plants, the patterns depended on the species examined. ForP. decipiens, the in-situ localization of both carboxylases was similar to that described forP. bisulcatum and other C3 plants. However, inP. milioides, PEP carboxylase was found exclusively in the cytosol of the mesophyll cells, as inP. miliaceum and other C4 species, whereas RuBP carboxylase was distributed in both the mesophyll and bundle-sheath chloroplasts.Abbreviations PEP
phosphoenolpyruvate
- RuBP
ribulose 1,5-bisphosphate 相似文献
14.
Photosynthetic Pathway Types of Forage Species Along Grazing Gradient from the Songnen Grassland,Northeastern China 总被引:3,自引:0,他引:3
Photosynthetic pathway types (C3 and C4 species) and their dynamics along grazing gradient were determined for 42 plant species in 30 genera and 13 families from the Songnen grassland, Northeastern China. Of the total, 10 species in 9 genera and 4 families had C4 photosynthesis; 32 species in 21 genera and 12 families had C3 photosynthesis. The proportion of C4 species in total plants and C4/C3 increased with grazing intensity, and peaked in overgrazed plot. Most of the increased C4 species (6 of 10) along the grazed gradient were annual grasses and halophytes. This indicated that the C4 species had greater capacity to tolerate environmental stresses (e.g. drought and saline) caused by animal grazing in the Songnen grassland, Northeastern China. 相似文献
15.
Natural occurrence of C4 species, life forms, and their longitudinal distribution patterns along the Northeast China Transect (NECT) were studied. Six vegetation regions experiencing similar irradiation regimes, but differing in longitude, precipitation, and altitude were selected along the NECT from 108 to 131 °E, around altitude of 43.5 °N. Seventy C4 species were identified in 41 genera and 13 families. 84 % of the total C4 species were found in four families: Gramineae (38 species), Chenopodiaceae (11 species), Cyperaceae (5 species), and Amaranthaceae (5 species). C4 grasses make up 54 % of the total identified C4 species along the NECT and form the leading C4 family in meadow, steppe, and desert along the NECT. C4
Chenopodiaceae species make up about 16 % of the C4 species and become less important, particularly in the meadow and the eastern end of the NECT. 57 % of the total C4 species are therophytes and 37 % are hemicryptophytes, which is consistent with floristic composition and land utilization. In general, the number of C4 species decreased significantly from the west to the east or from dry to moist areas along the NECT, and was remarkably correlated with annual precipitation (r
2= 0.677) and aridity (r
2= 0.912), except for salinized meadow region. The proportion of C4 species from all the six vegetation regions was considerably correlated with these two climatic parameters (r
2= 0.626 or 0.706, respectively). These findings suggest that the natural occurrence of C4 species varies significantly along the large-scale longitudinal gradient of the NECT. The notable relationship of C4 species number and proportion in the flora with variations in annual precipitation and aridity suggest that these two climatic parameters are the main factors controlling the longitudinal distribution patterns of C4 species along the NECT. 相似文献
16.
Carbon-isotope ratios were examined as 13C values in several C3, C4, and C3–C4
Flaveria species, and compared to predicted 13C, values generated from theoretical models. The measured 13C values were within 4 of those predicted from the models. The models were used to identify factors that contribute to C3-like 13C values in C3–C4 species that exhibit considerable C4-cycle activity. Two of the factors contributing to C3-like 13C values are high CO2 leakiness from the C4 pathway and pi/pa values that were higher than C4 congeners. A marked break occurred in the relationship between the percentage of atmospheric CO2 assimilated through the C4 cycle and the 13C value. Below 50% C4-cycle assimialtion there was no significant relationship between the variables, but above 50% the 13C values became less negative. These results demonstrate that the level of C4-cycle expression can increase from, 0 to 50% with little integration of carbon transfer from the C4 to the C3 cycle. As expression increaces above 50%, however, increased integration of C3- and C4-cycle co-function occurs.Abbreviations and symbols RuBP carboxylase
ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39)
- PEP carboxylase
phosphoenolpyruvate carboxylase (EC 4.1.1.31)
- pa
atmospheric CO2 partial pressure
- pi
intercellular CO2 partial pressure
-
isotope ratio
-
quantum yield for CO2 uptake 相似文献
17.
Photosynthetic pathways (e.g. C3, C4) and morphological functional types (e.g. trees, shrubs, high perennial grasses, perennial forbs) were identified for the native species from the Saskatchewan mixed
prairie, using the data from references published between 1950 and 2003. Of the total 219 identified species in 145 genera
and 45 families, 208 species in 137 genera and 44 families were found with C3 photosynthesis, and most of these species are dominants (e.g. Agropyron dasystachyum Hook. and Stipa spartea var. curtiseta Hitchc.). 11 species in 10 genera and 3 families were identified with C4 photosynthesis (e.g. Atriplex argentea Nutt., Andropogon scoparius Michx., Boutelou gracilis Lag., Calamovilfa longifolia Hook.). The amount of total identified C4 species in the region is much less than that from the South Dakota mixed prairie (27 species). Gramineae is the leading family with C4 photosynthesis (8 species), Chenopodiaceae ranks the second (2 species). Relatively less forb types [50 % perennial forbs (PEF) and 12 % annual forbs (ANF)] and more
graminoid types (25 %) composition suggested that the rangelands in the region are relatively stable. Lacking of the knowledge
on the optimal traits for PFTs classification in the region, further studies (e.g. C3 and C4 plant identification and optimal trait selection) are needed to explore the relationships between PFTs and vegetation variations,
as well as land-use and climate changes. 相似文献
18.
The genus Flaveria consists of 23 species with significant variation in photosynthetic physiologies. We tested whether photosynthetic pathway variation in seven co-existing Flaveria species corresponds to geographic distributions or physiological performance in C3, C4, and intermediate species growing under natural conditions in south-central Mexico. We found that Flaveria pringlei (C3) was the most widely distributed species with multiple growth habits. Numerous populations of Flaveria kochiana (C4), a recently described species with a previously unknown distribution, were located in the Mixtec region of Oaxaca. Flaveria cronquistii (C3) and Flaveria ramosissima (C3-C4) were only located in the Tehuacán Valley region while Flaveria trinervia (C4) was widely distributed. Only one population of Flaveria angustifolia (C3-C4) and Flaveria vaginata (C4-like) were located near Izúcar de Matamoros. Midday leaf water potential differed significantly between Flaveria species, but did not vary according to growth habit or photosynthetic pathway. The quantum yield of photosystem II did not vary between species, despite large differences in leaf nitrogen content, leaf shape, plant size and life histories. We did not find a direct relationship between increasing C4 cycle characteristics and physiological performance in the Flaveria populations examined. Furthermore, C3 species were not found at higher elevation than C4 species as expected. Our observations indicate that life history traits and disturbance regime may be the primary controllers of Flaveria distributions in south-central Mexico. 相似文献
19.
Background and Aims
Cleomaceae is one of 19 angiosperm families in which C4 photosynthesis has been reported. The aim of the study was to determine the type, and diversity, of structural and functional forms of C4 in genus Cleome.Methods
Plants of Cleome species were grown from seeds, and leaves were subjected to carbon isotope analysis, light and scanning electron microscopy, western blot analysis of proteins, and in situ immunolocalization for ribulose bisphosphate carboxylase oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC).Key Results
Three species with C4-type carbon isotope values occurring in separate lineages in the genus (Cleome angustifolia, C. gynandra and C. oxalidea) were shown to have features of C4 photosynthesis in leaves and cotyledons. Immunolocalization studies show that PEPC is localized in mesophyll (M) cells and Rubisco is selectively localized in bundle sheath (BS) cells in leaves and cotyledons, characteristic of species with Kranz anatomy. Analyses of leaves for key photosynthetic enzymes show they have high expression of markers for the C4 cycle (compared with the C3–C4 intermediate C. paradoxa and the C3 species C. africana). All three are biochemically NAD-malic enzyme sub-type, with higher granal development in BS than in M chloroplasts, characteristic of this biochemical sub-type. Cleome gynandra and C. oxalidea have atriplicoid-type Kranz anatomy with multiple simple Kranz units around individual veins. However, C. angustifolia anatomy is represented by a double layer of concentric chlorenchyma forming a single compound Kranz unit by surrounding all the vascular bundles and water storage cells.Conclusions
NAD-malic enzyme-type C4 photosynthesis evolved multiple times in the family Cleomaceae, twice with atriplicoid-type anatomy in compound leaves having flat, broad leaflets in the pantropical species C. gynandra and the Australian species C. oxalidea, and once by forming a single Kranz unit in compound leaves with semi-terete leaflets in the African species C. angustifolia. The leaf morphology of C. angustifolia, which is similar to that of the sister, C3–C4 intermediate African species C. paradoxa, suggests adaptation of this lineage to arid environments, which is supported by biogeographical information. 相似文献20.
Floristic compositions, life forms, reproductive types for forage species, and their responses to desertification in Hunshandake desert were studied. 164 species, in 30 families and 94 genera, were identified with C3 (137 species), C4 (25 species), and CAM (2 species) photosynthesis. Of the 25 C4 species, 76 % were grasses and Chenopodiaceae species (hereafter chenopods). This suggests that the C4 species mainly occurred in a few families in the desert region. The reduction of C3 species and the increase of C4 species with desertification indicated that C4 species might have higher tolerance to environmental stresses (e.g. dry and poor soil). Relatively more hemicrytophyte and therophyte forms in the desert are related to the local temperate climate and vegetation dynamics. Relatively greater proportions of C4/C3 and clonal species/sexual species at mobile dune showed that the C4 species and clonal species could make greater contribution to sand land restoration in the Hunshandake desert. 相似文献