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1.
Summary Six early successional plant species with differing photosynthetic pathways (3 C3 species and 3 C4 species) were grown at either 300, 600, or 1,200 ppm CO2 and at either 0.0 or 0.25 ppm SO2. Total plant growth increased with CO2 concentration for the C3 species and varied only slightly with CO2 for the C4 species. Fumigation with SO2 caused reduced growth of the C3 species at 300 ppm CO2 but not at the higher concentrations of CO2. Fumigation with SO2 reduced growth of the C4 species at high CO2 and increased growth at 300 ppm CO2. Leaf area increased with increasing CO2 for all plant species. Fumigation with SO2 reduced leaf area of C3 plants more at low CO2 than at high CO2 while leaf area of C4 plants was reduced more at high CO2 than at low CO2. These results support the notion that C3 species are more sensitive to SO2 fumigation than are C4 species at concentrations of CO2 equal to that found in normal ambient air. However, the difference in sensitivity to SO2 between C3 and C4 species was found to be reversed at higher concentrations of CO2. A possible explanation for this reversal based upon differences in stomatal response to elevated CO2 between C3 and C4 species is discussed. 相似文献
2.
Carbon balance,productivity, and water use of cold-winter desert shrub communities dominated by C3 and C4 species 总被引:1,自引:1,他引:0
Summary Common generalizations concerning the ecologic significance of C4 photosynthesis were tested in a study of plant gas exchange, productivity, carbon balance, and water use in monospecific communities of C3 and C4 salt desert shrubs. Contrary to expectations, few of the hypotheses concerning the performance of C4 species were supported. Like the C3 species, Ceratoides lanata, the C4 shrub, Atriplex confertifolia, initiated growth and photosynthetic activity in the cool spring months and also exhibited maximum photosynthetic rates at this time of year. To compete successfully with C3 species, Atriplex may have been forced to evolve the capacity for photosynthesis at low temperatures prevalent during the spring when moisture is most abundant. Maximum photosynthetic rates of Atriplex were lower than those of the C3 species. This was compensated by a prolonged period of low photosynthetic activity in the dry late summer months while Ceratoides became largely inactive. However, the annual photosynthetic carbon fixation per ground area was about the same in these two communities composed of C3 and C4 shrubs. The C4 species did not exhibit greater leaf diffusion resistance than the C3 species. The photosynthesis/transpiration ratios of the two species were about the same during the period of maximum photosynthetic rates in the spring. During the warm summer months the C4 species did have superior photosynthesis/transpiration ratios. Yet, since Ceratoides completed a somewhat greater proportion of its annual carbon fixation earlier in the season, the ratio of annual carbon fixation/transpiratory water loss in the two communities was about the same. Atriplex did incorporate a greater percentage of the annual carbon fixation into biomass production than did Ceratoides. However, this is considered to be a reflection of properties apart from the C4 photosynthetic pathway. Both species displayed a heavy commitment of carbon to the belowground system, and only about half of the annual moisture resource was utilized in both communities. 相似文献
3.
Summary Pure and mixed cultures of the dicotyledons Atriplex hortensis L. (C3 plant) and Amaranthus retroflexus L. (C4 plant) were maintained under open air conditions in standard soil at low and high nitrogen supply levels.A comparison of shoot dry weight and shoot length in the various series shows that the growth of the aboveground parts of both species was severely reduced under low N conditions. In both pure and mixed cultures the differences resulting from low N vs. high N conditions was less pronounced with Atriplex (C3 plant) than with Amaranthus (C4 plant). The root dry weight of the two species was not reduced so much under low N conditions as was the shoot dry weight. The low N plants were found to contain a larger proportion of their biomass in the roots than did the high N plants. In general the root proportion of Atriplex was greater than that of Amaranthus. The contents of organic nitrogen and nitrate and the nitrate reductase activity (NRA) per g dry weight of both species decreased continually throughout the experiments. With the exception of young plants, the low N plants always had tower contents of organic nitrogen and nitrate and nitrate reductase activities than did the high N plants. The highest values of NRA were measured in the leaf laminae. The eaves also exhibited the highest concentrations of organic nitrogen. The highest nitrate concentrations, however, were observed in the shoot axis, and in most cases the lowest nitrate values were found in the laminae. At the end of ne growing season this pattern was found to have been reversed with Atriplex, but not with Amaranthus. Thus Atriplex was able to maintain a higher NRA in the laminae than Amaranthus under low N conditions.The transpiration per leaf area of the C4 plant Amaranthus during the course of a day was substantially lower than that of the C3 plant Atriplex. There were no significant differences in transpiration between the low N and high N series of Amaranthus. The low N plants of Atriplex, however, clearly showed in most cases higher transpiration rates than the corresponding high N plants. These different transpiration rates of the high N and the low N Atriplex plants were also reflected in a distinct 13C discrimination.The sum of these results points to the conclusion that the C3 plant Atriplex hortensis can maintain a better internal inorganic nitrogen supply than the C4 plant Amaranthus retroflexus under low N conditions and an ample water supply, due to the larger root proportion and the more pronounced and flexible transpiration of the C3 plant.Dedicated to Prof. Dr. Karl Mägdefrau, Deisenhofen, on the ocasion of his 80th birthday 相似文献
4.
Summary In an effort to predict SO2 sensitivity of plants from their morphological and physiological features, the effects of SO2 on photosynthesis were partitioned between stomatal and nonstomatal components for a drought deciduous shrub, Diplacus aurantiacus, and an evergreen shrub, Heteromeles arbutifolia. As predicted, the drought deciduous shrub had the higher gas conductance, and hence SO2 absorptance. However, nonstomatal components also play a role in determining SO2 sensitivity. Apparently a plant with a high intrinsic photosynthetic capacity will be more sensitive to SO2 than one with a lower capacity. 相似文献
5.
Abstract. The photosynthetic responses to temperature in C3, C3-C4 intermediate, and C4 species in the genus Flaveria were examined in an effort to identify whether the reduced photorespiration rates characteristic of C3-C4 intermediate photosynthesis result in adaptive advantages at warm leaf temperatures. Reduced photorespiration rates were reflected in lower CO2 compensation points at all temperatures examined in the C3-C4 intermediate, Flaveria floridana, compared to the C3 species, F. cronquistii. The C3-C4 intermediate, F. floridana, exhibited a C3-like photosynthetic temperature dependence, except for relatively higher photosynthesis rates at warm leaf temperatures compared to the C3 species, F. cronquistii. Using models of C3 and C3-C4 intermediate photosynthesis, it was predicted that by recycling photorespired CO2 in bundle-sheath cells, as occurs in many C3-C4 intermediates, photosynthesis rates at 35°C could be increased by 28%, compared to a C3 plant. Without recycling photorespired CO2, it was calculated that in order to improve photosynthesis rates at 35°C by this amount in C3 plants, (1) intercellular CO2 partial pressures would have to be increased from 25 to 31 Pa, resulting in a 57% decrease in water-use efficiency, or (2) the activity of RuBP carboxylase would have to be increased by 32%, resulting in a 22% decrease in nitrogen-use efficiency. In addition to the recycling of photorespired CO2, leaves of F. floridana appear to effectively concentrate CO2 at the active site of RuBP carboxylase, increasing the apparent carboxylation efficiency per unit of in vitro RuBP carboxylase activity. The CO2-concentrating activity also appears to reduce the temperature sensitivity of the carboxylation efficiency in F. floridana compared to F. cronquistii. The carboxylation efficiency per unit of RuBP carboxylase activity decreased by only 38% in F. floridana, compared to 50% in F. cronquistii, as leaf temperature was raised from 25 to 35°C. The C3-C4 intermediate, F. ramosissima, exhibited a photosynthetic temperature temperature response curve that was more similar to the C4 species, F. trinervia, than the C3 species, F. cronquistii. The C4-like pattern is probably related to the advanced nature of C4-like biochemical traits in F. ramosissima The results demonstrate that reductions in photorespiration rates in C3-C4 intermediate plants create photosynthetic advantages at warm leaf temperatures that in C3 plants could only be achieved through substantial costs to water-use efficiency and/or nitrogen-use efficiency. 相似文献
6.
Photosynthetic Enzyme Activities and Localization in Mollugo verticillata Populations Differing in the Levels of C(3) and C(4) Cycle Operation 总被引:3,自引:1,他引:2
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Ecotypic differences in the photosynthetic carbon metabolism of Mollugo verticillata were studied. Variations in C3 and C4 cycle activity are apparently due to differences in the activities of enzymes associated with each pathway. Compared to C4 plants, the activities of C4 pathway enzymes were generally lower in M. verticillata, with the exception of the decarboxylase enzyme, NAD malic enzyme. The combined total carboxylase enzyme activity of M. verticillata was greater than that of C3 plants, possibly accounting for the high photosynthetic rates of this species. Unlike either C3 or C4 plants, ribulose bisphosphate carboxylase was present in both mesophyll and bundle sheath cell chloroplasts in M. verticillata. The localization of this enzyme in both cells in this plant, in conjunction with an efficient C4 acid decarboxylation mechanism most likely localized in bundle sheath cell mitochondria, may account for intermediate photorespiration levels previously observed in this species. 相似文献
7.
The endemic Hawaiian species of Scaevola and Euphorbia grow in a wide variety of native habitats and exhibit a wide range of variation in photosynthetic responses. Light-saturated photosynthetic capacities range from 12.0 to 24.7 μmol CO2 m−-2 s−-1 in the Scaevola species and from 18.2 to 51.4 μmol CO2 m−-2 s−-1 in the Euphorbia species. Within each genus, differences in light-saturated photosynthetic capacity are paralleled by differences in mesophyll and leaf conductances to CO2. Within each habitat, the C4 Euphorbia species exhibits a significantly higher photosynthetic capacity and a significantly higher mesophyll conductance than the corresponding C3 Scaevola species. These differences are greatest in the dry scrub habitat and least in the wet forest habitat. One photosynthetic characteristic that exhibits little variation among the species within each genus, yet that exhibits a consistently large difference between the species within each habitat, is photosynthetic water-use efficiency. The C4 Euphorbia species possess water-use efficiencies that are 2–3½ times as high as those of the C3 Scaevola species, regardless of whether these species are native to very dry or very wet habitats. At present, the ecological significance of this large inherent difference in photosynthetic water-use efficiency is unknown. Indeed, it appears that neither photosynthetic pathway has imposed any major inherent constraints on the ability of the Scaevola and Euphorbia species to diversify into a wide variety of habitats. 相似文献
8.
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
9.
Abutilon theophrasti (C3) and Amaranthus retroflexus (C4), were grown from seed at four partial pressures of CO2: 15 Pa (below Pleistocene minimum), 27 Pa (pre-industrial), 35 Pa (current), and 70 Pa (future) in the Duke Phytotron under high light, high nutrient, and wellwatered conditions to evaluate their photosynthetic response to historic and future levels of CO2. Net photosynthesis at growth CO2 partial pressures increased with increasing CO2 for C3 plants, but not C4 plants. Net photosynthesis of Abutilon at 15 Pa CO2 was 70% less than that of plants grown at 35 Pa CO2, due to greater stomatal and biochemical limitations at 15 Pa CO2. Relative stomatal limitation (RSL) of Abutilon at 15 Pa CO2 was nearly 3 times greater than at 35 Pa CO2. A photosynthesis model was used to estimate ribulose-1,5-bisphosphate carboxylase (rubisco) activity (Vcmax), electron transport mediated RuBP regeneration capacity (J
max), and phosphate regeneration capacity (PiRC) in Abutilon from net photosynthesis versus intercellular CO2 (A–C
i) curves. All three component processes decreased by approximately 25% in Abutilon grown at 15 Pa compared with 35 Pa CO2. Abutilon grown at 15 Pa CO2 had significant reductions in total rubisco activity (25%), rubisco content (30%), activation state (29%), chlorophyll content (39%), N content (32%), and starch content (68%) compared with plants grown at 35 Pa CO2. Greater allocation to rubisco relative to light reaction components and concomitant decreases in J
max and PiRC suggest co-regulation of biochemical processes occurred in Abutilon grown at 15 Pa CO2. There were no significant differences in photosynthesis or leaf properties in Abutilon grown at 27 Pa CO2 compared with 35 Pa CO2, suggesting that the rise in CO2 since the beginning of the industrial age has had little effect on the photosynthetic performance of Abutilon. For Amaranthus, limitations of photosynthesis were balanced between stomatal and biochemical factors such that net photosynthesis was similar in all CO2 treatments. Differences in photosynthetic response to growth over a wide range of CO2 partial pressures suggest changes in the relative performance of C3 and C4 annuals as atmospheric CO2 has fluctuated over geologic time. 相似文献
10.
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
11.
Summary CO2 exchange characteristics and the activity of the carboxylating enzymes phosphoenolpyruvate carboxylase (PEP-C, E.C. 4.1.1.31) and ribulose 1,5-bisphosphate carboxylase (RuBP-C, E.C. 4.1.1.39) during one year in the greenhouse and at two levels of light and temperature in growth chambers were determined in the C3-C4 intermediate species P. milioides Nees ex. Trin. These results were compared with those of P. bisulcatum Thumb. (C3) and P. maximum Jacq. (C4). Under all tested conditions, and even when the influence of leaf surface temperature on photosynthetic rates and CO2 compensation points were measured, the biochemical and physiological behaviour of the C3-C4 intermediate was more similar to that of the C3 plant than the C4 species. The C4 plant P. maximum, however, responded positively, mainly in terms of PEP-C activity and photosynthetic rate, to the regime of high light and temperature. The results presented indicate that in the C3-C4
Panicum grown in high light and temperature no direct relationships between a low CO2 compesation point and superior growth are evident. It has still to be clarified why in nature a photosynthetic-photorespiratory pathway leading to an intermediate CO2 compensation value has evolved in P. milioides. 相似文献
12.
Stephen Rawsthorne Christopher M. Hylton Alison M. Smith Harold W. Woolhouse 《Planta》1988,173(3):298-308
Photorespiratory metabolism of the C3-C4 intermediate species Moricandia arvensis (L.) DC has been compared with that of the C3 species, Moricandia moricandioides (Boiss.) Heywood. Assays of glycollate oxidase (EC 1.1.3.1), glyoxylate aminotransferases (EC 2.6.1.4, EC 2.6.1.45) and hydroxypyruvate reductase (EC 1.1.1.29) indicate that the capacity for flux through the photorespiratory cycle is similar in both species. Immunogold labelling with monospecific antibodies was used to investigate the cellular locations of ribulose 1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), glycollate oxidase, and glycine decarboxylase (EC 2.1.2.10) in leaves of the two species. Ribulose 1,5-bisphosphate carboxylase/oxygenase was confined to the stroma of chloroplasts and glycollate oxidase to the peroxisomes of all photosynthetic cells in leaves of both species. However, whereas glycine decarboxylase was present in the mitochondria of all photosynthetic cells in M. moricandioides, it was only found in the mitochondria of bundle-sheath cells in M. arvensis. We suggest that localized decarboxylation of glycine in the leaves of M. arvensis will lead to improved recapture of photorespired CO2 and hence a lower rate of photorespiration.Abbreviations kDa
kilodalton
- RuBP
ribulose-1,5-bisphosphate 相似文献
13.
Photosynthetic rate, transpiration rate and SO2 absorption rate were simultaneously measured under exposure to SO2 (0.1–1.0 μl l ?1) for 5 or 8 hr in six species belonging to C4 or C3 plants (Zea mays, Sorghum vulgare, Amaranthus tricolor, Oryza sativa, Avena sativa andHelianthus annuus). Distinct interspecific differences were found as to the extent of inhibition of photosynthetic rate. Calculation of diffusive resistance to H2O(r) and SO2(r′) showed that the ratio of r′/r was 1.9 irrespective of species and coincided well with the theoretical value based on molecular diffusion. Thus it was made clear that the absorption of SO2 was dependent upon the gas exchange capacity of leaf blade. Using the ratio of r′/r the rate of SO2 absorption could be calculated from transpiration rate and was compared with the inhibition rate of photosynthesis. In three C4 species, the inhibition of photosynthesis increased linearly with the amount of SO2 absorbed during a 5-hour period. The pattern of inhibition of photosynthesis inA. sativa andH. annuus among C3 species was similar to that of C4 species until the amount of SO2 absorbed reached 60 mg-SO2 m?2 above which the inhibition abruptly increased. The inhibition of photosynthesis inO. sativa was exceptionally severe even with only a small amount of SO2 absorbed. 相似文献
14.
Effects of the Phosphoenolpyruvate Carboxylase Inhibitor 3,3-Dichloro-2-(Dihydroxyphosphinoylmethyl)propenoate on Photosynthesis: C(4) Selectivity and Studies on C(4) Photosynthesis 总被引:7,自引:6,他引:1
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Jenkins CL 《Plant physiology》1989,89(4):1231-1237
The effect of 3,3-dichloro-2-(dihydroxyphosphinoylmethyl)-propenoate (DCDP), an analog of phosphoenolpyruvate (PEP), on PEP carboxylase activity in crude leaf extracts and on photosynthesis of excised leaves was examined. DCDP is an effective inhibitor of PEP carboxylase from Zea mays or Panicum miliaceum; 50% inhibition was obtained at 70 or 350 micromolar, respectively, in the presence of 1 millimolar PEP and 1 millimolar HCO3−. When fed to leaf sections via the transpiration stream, DCDP at 1 millimolar strongly inhibited photosynthesis in C4 species (79-98% inhibition for a range of seven C4 species), but only moderately in C3 species (12-46% for four C3 species), suggesting different mechanisms of inhibition for each photosynthetic type. The response of P. miliaceum (C4) net photosynthesis to intercellular pCO2 showed that carboxylation efficiency, as well as the CO2 saturated rate, are lowered in the presence of DCDP and supported the view that carboxylation efficiency in C4 species is directly related to PEP carboxylase activity. A fivefold increase in intercellular pCO2 over that occurring in P. miliaceum under normal photosynthesis conditions only increased net photosynthesis rate in the presence of 1 millimolar DCDP from zero to about 5% of the maximal uninhibited rate. Therefore, it seems unlikely that direct fixation of atmospheric CO2 by the bundle sheath cells makes any significant contribution to photosynthetic CO2 assimilation in C4 species. The results support the concept that C4-selective herbicides may be developed based on inhibitors of C4 pathway reactions. 相似文献
15.
During the past 25 Myr, partial pressures of atmospheric CO2 (Ca) imposed a greater limitation on C3 than C4 photosynthesis. This could have important downstream consequences for plant nitrogen economy and biomass allocation. Here, we report the first phylogenetically controlled comparison of the integrated effects of subambient Ca on photosynthesis, growth and nitrogen allocation patterns, comparing the C3 and C4 subspecies of Alloteropsis semialata. Plant size decreased more in the C3 than C4 subspecies at low Ca, but nitrogen pool sizes were unchanged, and nitrogen concentrations increased across all plant partitions. The C3, but not C4 subspecies, preferentially allocated biomass to leaves and increased specific leaf area at low Ca. In the C3 subspecies, increased leaf nitrogen was linked to photosynthetic acclimation at the interglacial Ca, mediated via higher photosynthetic capacity combined with greater stomatal conductance. Glacial Ca further increased the biochemical acclimation and nitrogen concentrations in the C3 subspecies, but these were insufficient to maintain photosynthetic rates. In contrast, the C4 subspecies maintained photosynthetic rates, nitrogen‐ and water‐use efficiencies and plant biomass at interglacial and glacial Ca with minimal physiological adjustment. At low Ca, the C4 carbon‐concentrating mechanism therefore offered a significant advantage over the C3 type for carbon acquisition at the whole‐plant scale, apparently mediated via nitrogen economy and water loss. A limiting nutrient supply damped the biomass responses to Ca and increased the C4 advantage across all Ca treatments. Findings highlight the importance of considering leaf responses in the context of the whole plant, and show that carbon limitation may be offset at the expense of greater plant demand for soil resources such as nitrogen and water. Results show that the combined effects of low CO2 and resource limitation benefit C4 plants over C3 plants in glacial–interglacial environments, but that this advantage is lessened under anthropogenic conditions. 相似文献
16.
Summary The C4 species, Euphorbia forbesii, and the C3 species, Claoxylon sandwicense, occupy cool, shaded habitats in Hawaii. Both of these species exhibit the photosynthetic characteristics of typical shade plants: low light-saturated photosynthetic rates, low dark respiration rates, low light levels for saturation of photosynthesis, and low light compensation points. In addition, the quantum yields of the two species are similar at leaf temperatures near 22°C, reflecting a significant increase in the quantum yield of E. forbesii over that of C4 species from open habitats. C. sandwicense has a lower dark respiration rate than E. forbesii. Hence, since the quantum yields of the two species are similar at cool temperatures, C. sandwicense has a higher photosynthetic rate than E. forbesii at low incident photon flux densities. As a consequence, C. sandwicense should have a greater carbon gain than E. forbesii under the diffuse radiation conditions of their native habitat. However, since E. forbesii has a higher light-saturated photosynthetic rate than C. sandwicense, E. forbesii may have a greater carbon gain than C. sandwicense during sunflecks. 相似文献
17.
Ferit Kocacinar 《Physiologia plantarum》2015,153(3):454-466
In plants, most water is absorbed by roots and transported through vascular conduits of xylem which evaporate from leaves during photosynthesis. As photosynthesis and transport processes are interconnected, it was hypothesized that any variation in water transport demand influencing water use efficiency (WUE), such as the evolution of C4 photosynthesis, should affect xylem structure and function. Several studies have provided evidence for this hypothesis, but none has comprehensively compared photosynthetic, hydraulic and biomass allocation properties between C3 and C4 species. In this study, photosynthetic, hydraulic and biomass properties in a closely related C3 Tarenaya hassleriana and a C4 Cleome gynandra are compared. Light response curves, measured at 30°C, showed that the C4 C. gynandra had almost twice greater net assimilation rates than the C3 T. hassleriana under each increasing irradiation level. On the contrary, transpiration rates and stomatal conductance were around twice as high in the C3, leading to approximately 3.5 times higher WUE in the C4 compared with the C3 species. The C3 showed about 3.3 times higher hydraulic conductivity, 4.3 times greater specific conductivity and 2.6 times higher leaf‐specific conductivity than the C4 species. The C3 produced more vessels per xylem area and larger vessels. All of these differences resulted in different biomass properties, where the C4 produced more biomass in general and had less root to shoot ratio than the C3 species. These results are in support of our previous findings that WUE, and any changes that affect WUE, contribute to xylem evolution in plants. 相似文献
18.
The occurrence of both C3 and C4 photosynthetic characteristics in a single Zea mays plant 总被引:1,自引:0,他引:1
The activities of the carboxylating enzymes ribulose-1,5-biphosphate (RuBP) carboxylase and phosphoenolpyruvate (PEP) carboxylase in leaves of three-week old Zea mays plants grown under phytotron conditions were found to vary according to leaf position. In the lower leaves the activity of PEP carboxylase was lower than that of RuBP carboxylase, while the upper leaves exhibited high levels of PEP carboxylase. Carbon dioxide compensation points and net photosynthetic rates also differed in the lower and upper leaves. Differences in the fine structure of the lowermost and uppermost leaves are shown. The existence of both the C3 and C4 photosynthetic pathways in the same plant, in this and other species, is discussed.Abbreviations PEP
phosphoenolpyruvate
- RuBP
ribulose-1,5-biphosphate 相似文献
19.
Bhaskarrao Chinthapalli Chitra Raghavan O. Bläsing P. Westhoff A.S. Raghavendra 《Photosynthetica》2001,38(3):415-419
Phosphoenolpyruvate carboxylase (PEPC) was purified from leaves of four species of Alternanthera differing in their photosynthetic carbon metabolism: Alternanthera sessilis (C3), A. pungens (C4), A. ficoides and A. tenella (C3-C4 intermediates or C3-C4). The activity and properties of PEPC were examined at limiting (0.05 mM) or saturating (10 mM) bicarbonate concentrations.
The Vmax as well as Km values (for Mg2+ or PEP) of PEPC from A. ficoides and A. tenella (C3-C4 intermediates) were in between those of C3 (A. sessilis) and C4 species (A. pungens). Similarly, the sensitivity of PEPC to malate (an inhibitor) or G-6-P (an activator) of A. ficoides and A. tenella (C3-C4) was also of intermediate status between those of C3 and C4 species of A. sessilis and A. pungens, respectively. In all the four species, the maximal activity (Vmax), affinity for PEP (Km), and the sensitivity to malate (KI) or G-6-P (KA) of PEPC were higher at 10 mM bicarbonate than at 0.05 mM bicarbonate. Again, the sensitivity to bicarbonate of PEPC from
C3-C4 intermediates was in between those of C3- and C4-species. Thus the characteristics of PEPC of C3-C4 intermediate species of Alternanthera are intermediate between C3- and C4-type, in both their kinetic and regulatory properties. Bicarbonate could be an important modulator of PEPC, particularly
in C4 plants.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Comparative 14CO2 pulse-12CO2 chase studies performed at CO2 compensation ()-versus air-concentrations of CO2 demonstrated a four-to eightfold increase in assimilation of 14CO2 into the C4 acids malate and aspartate by leaves of the C3-C4 intermediate species Panicum milioides Nees ex Trin., P. decipiens Nees ex Trin., Moricandia arvensis (L.) DC., and M. spinosa Pomel at . Specifically, the distribution of 14C in malate and aspartate following a 10-s pulse with 14CO2 increases from 2% to 17% (P. milioides) and 4% to 16% (M. arvensis) when leaves are illuminated at the CO2 compensation concentration (20 l CO2/l, 21% O2) versus air (340 l CO2/l, 21% O2). Chasing recently incorporated 14C for up to 5 min with 12CO2 failed to show any substantial turnover of label in the C4 acids or in carbon-4 of malate. The C4-acid labeling patterns of leaves of the closely related C3 species, P. laxum Sw. and M. moricandioides (Boiss.) Heywood, were found to be relatively unresponsive to changes in pCO2 from air to . These data demonstrate that the C3-C4 intermediate species of Panicum and Moricandia possess an inherently greater capacity for CO2 assimilation via phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) at the CO2 compensation concentration than closely related C3 species. However, even at , CO2 fixation by PEP carboxylase is minor compared to that via ribulosebisphosphate carboxylase (EC 4.1.1.39) and the C3 cycle, and it is, therefore, unlikely to contribute in a major way to the mechanism(s) facilitating reduced photorespiration in the C3-C4 intermediate species of Panicum and Moricandia.Abbreviations Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- PEP
phosphoenolpyruvate
-
CO2 compensation concentration
- 3PGA
3-phosphoglycerate
- SuP
sugar monophosphates
- SuP2
sugar bisphosphates
Published as Paper No. 8249, Journal Series, Nebraska Agricultural Research Division 相似文献