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1.
Summary The gas exchange of leaves of Amaranthus retroflexus (C 4) measured under fluctuating environmental conditions in an experimental garden in Würzburg was compared with that of Glycine max and Chenopodium album (C 3). Consistent with previous observations, Amaranthus had higher leaf diffusion resistance than the C 3 species and low internal air space carbon dioxide concentration. Due to high photosynthetic capacity, Amaranthus fixed as much carbon during the light as the C 3 species, even at low temperatures and low light intensities. Low rates of dark respiration of leaves potentially enhances the ability of Amaranthus to grow rapidly after establishment in a disturbed habitat. The data suggest that some populations of Amaranthus retroflexus are adapted to cool climate conditions but are also able to exploit high temperature situations. 相似文献
2.
Summary Seasonal changes in the light and temperature dependence of photosynthesis were investigated in field grown plants of Mercurialis perennis and Geum urbanum. In both species changes in photosynthetic capacity were closely related to the development of the overstorey canopy. In G. urbanum there was a marked shift in the temperature dependence of photosynthesis through the season whereas no such pattern was found in M. perennis. Model predictions of field rates of photosynthesis were made using the measurements of light and temperature dependence in the laboratory and validated against field observations. Long term continuous records of light and temperature in the field were used in conjunction with the model to make predictions of carbon acquisition in shoots of the two species through the season. These calculations indicated that G. urbanum was able to take advantage of high light levels just prior to canopy closure through a combination of high photosynthetic capacity, the ability to maintain photosynthesis at relatively low temperatures and the presence of overwintering leaves. In M. perennis leaf development was early enough to utilise the high spring light period. After canopy closure M. perennis maintained a higher average rate of CO 2 flux due to a combination of high apparent quantum efficiency and low rates of respiration. 相似文献
3.
Summary Laboratory gas exchange measurements were conducted on four pioneering beach species from southern California. Atriplex leucophylla (Moq.) D. Dietr., a C 4 species, had a photosynthetic temperature optimum substantially higher than leaf temperatures normally experienced on the beach during the primary growing season. The C 3 species, Cakile maritima Scop., Ambrosia chamissonis Less. and Abronia maritima Nutt. ex Wats., had photosynthetic temperature optima close to their growth temperature and higher photosynthetic rates than the C 4 species at normal field growth temperatures. Atriplex leucophylla had higher mesophyll conductances which resulted in higher water use efficiencies at all measurement temperatures. Leaf chlorophyll and protein contents were not correlated with photosynthetic rates. The possible significance of water use efficiency is discussed in relation to the characteristics of the beach habitat. 相似文献
4.
The photosynthetic performance of C 4 plants is generally inferior to that of C 3 species at low temperatures, but the reasons for this are unclear. The present study investigated the hypothesis that the capacity of Rubisco, which largely reflects Rubisco content, limits C 4 photosynthesis at suboptimal temperatures. Photosynthetic gas exchange, chlorophyll a fluorescence, and the in vitro activity of Rubisco between 5 and 35 °C were measured to examine the nature of the low‐temperature photosynthetic performance of the co‐occurring high latitude grasses, Muhlenbergia glomerata (C 4) and Calamogrostis canadensis (C 3). Plants were grown under cool (14/10 °C) and warm (26/22 °C) temperature regimes to examine whether acclimation to cool temperature alters patterns of photosynthetic limitation. Low‐temperature acclimation reduced photosynthetic rates in both species. The catalytic site concentration of Rubisco was approximately 5.0 and 20 µmol m ?2 in M. glomerata and C. canadensis, respectively, regardless of growth temperature. In both species, in vivo electron transport rates below the thermal optimum exceeded what was necessary to support photosynthesis. In warm‐grown C. canadensis, the photosynthesis rate below 15 °C was unaffected by a 90% reduction in O 2 content, indicating photosynthetic capacity was limited by the capacity of P i‐regeneration. By contrast, the rate of photosynthesis in C. canadensis plants grown at the cooler temperatures was stimulated 20–30% by O 2 reduction, indicating the P i‐regeneration limitation was removed during low‐temperature acclimation. In M. glomerata, in vitro Rubisco activity and gross CO 2 assimilation rate were equivalent below 25 °C, indicating that the capacity of the enzyme is a major rate limiting step during C 4 photosynthesis at cool temperatures. 相似文献
5.
Net photosynthetic rates and mesophyll conductances were measured under standardized conditions for leaves of two C 3 and one C 4 annual species grown at temperatures of 20 to 32°C. Plants were grown with varying day and night temperatures, and also at constant temperatures equal to all the day and night temperatures used. Plants were grown with 8, 12, and 16 hours of light per day. This design allowed determination of whether photosynthetic characteristics were best correlated with day, night, mean, or time-weighted mean temperatures, The results showed that for Glycine max (L.) Merr. (C 3) night temperature was most important in determining photosynthetic characteristics, while in Helianthus annuus L. (C 3) and Amaranthus hypochondriacus L. (C 4) the time-weighted mean temperature was most important. The results for all species were consistent with the hypothesis that development of photosynthetic characteristics is related to a balance between the rate of leaf expansion and the rate of photosynthesis under the growth conditions. 相似文献
6.
The characteristics of oscillations in photosynthetic carbon fixation and chlorophyll fluorescence in leaves of the C 4 plant Amaranthus caudatus L. were compared to those shown by the C 3 plant Spinacia oleracea L. As in spinach, oscillations could be observed in Amaranthus when leaves were illuminated after periods of darkening, particularly at temperatures below 20°C, less so or not at all at higher temperatures. However, in contrast to spinach, pronounced oscillations occurred in Amaranthus after a sudden dark/light transition only at low, not at high photon flux densities. Whereas in spinach maxima in carbon uptake were observed slightly after minima in chlorophyll fluorescence had occurred, in Amaranthus maxima in carbon uptake were close to maxima in chlorophyll fluorescence. Since the quantum efficiency of electron transport through photosystem II of the chloroplast electron-transport chain was higher during the minima of chlorophyll fluorescence than during the maxima, the observations suggest that in Amaranthus photosynthetic water oxidation did not occur as synchronously with carbon uptake as in spinach. It is proposed that, in contrast to spinach, photosynthetic oscillations in Amaranthus are related to the diffusional transport of photosynthetic intermediates between mesophyll and bundle-sheath cells.Abbreviations F o, F m, F s
initial, maximal and steady-state chlorophyll a fluorescence
- PFD
photon flux density
- Q A
primary quinone acceptor of PSII
We are grateful to Professors D.A. Walker, FRS, Robert Hill Institute, University of Sheffield, Sheffield, UK., and Agu Laisk, Chair of Plant Physiology, University of Tartu, Tartu, Estonia, for helpful discussions and to Ms. S. Neimanis for help with the experiments. Our work was performed within the research of the Sonderforschungsbereich 251 of the University of Würzburg. It was supported by the Stiftung Volkswagenwerk. A.S.R. acknowledges also support by the Alexander-von-Humboldt-Stiftung and U.G. by the Graduate College of the University of Würzburg. 相似文献
7.
Summary Detailed growth analysis in conjunction with information on leaf display and nitrogen uptake was used to interpret competition between Abutilon theophrasti, a C 3 annual, and Amaranthus retroflexus, a C 4 annual, under ambient (350 l l -1) and two levels of elevated (500 and 700 l l -1) CO 2. Plants were grown both individually and in competition with each other. Competition caused a reduction in growth in both species, but for different reasons. In Abutilon, decreases in leaf area ratio (LAR) were responsible, whereas decreased unit leaf rate (ULR) was involved in the case of Amaranthus. Mean canopy height was lower in Amaranthus than Abutilon which may explain the low ULR of Amaranthus in competition. The decrease in LAR of Abutilon was associated with an increase in root/shoot ratio implying that Abutilon was limited by competition for below ground resources. The root/shoot ratio of Amaranthus actually decreased with competition, and Amaranthus had a much higher rate of nitrogen uptake per unit of root than did Abutilon. These latter results suggest that Amaranthus was better able to compete for below ground resources than Abutilon. Although the growth of both species was reduced by competition, generally speaking, the growth of Amaranthus was reduced to a greater extent than that of Abutilon. Regression analysis suggests that the success of Abutilon in competition was due to its larger starting capital (seed size) which gave it an early advantage over Amaranthus. Elevated CO 2 had a positive effect upon biomass in Amaranthus, and to a lesser extent, Abutilon. These effects were limited to the early part of the experiment in the case of the individually grown plants, however. Only Amaranthus exhibited a significant increase in relative growth rate (RGR). In spite of the transitory effect of CO 2 upon size in individually grown plants, level of CO 2 did effect final biomass of competitively grown plants. Abutilon grown in competition with Amaranthus had a greater final biomass than Amaranthus at ambient CO 2 levels, but this difference disappeared to a large extent at elevated CO 2. The high RGR of Amaranthus at elevated CO 2 levels allowed it to overcome the difference in initial size between the two species.This study was supported by a grant from the US Department of Energy 相似文献
8.
The Chenopodiaceae is one of the families including C4 species among eudicots. In this family, the genus Chenopodium is considered to include only C3 species. However, we report here a transition from C3 photosynthesis to proto-Kranz to C3–C4 intermediate type in Chenopodium. We investigated leaf anatomical and photosynthetic traits of 15 species, of which 8 species showed non-Kranz anatomy and a CO2 compensation point (Γ) typical of C3 plants. However, 5 species showed proto-Kranz anatomy and a C3-like Γ, whereas C. strictum showed leaf anatomy and a Γ typical of C3–C4 intermediates. Chenopodium album accessions examined included both proto-Kranz and C3–C4 intermediate types, depending on locality. Glycine decarboxylase, a key photorespiratory enzyme that is involved in the decarboxylation of glycine, was located predominantly in the mesophyll (M) cells of C3 species, in both M and bundle-sheath (BS) cells in proto-Kranz species, and exclusively in BS cells in C3–C4 intermediate species. The M/BS tissue area ratio, number of chloroplasts and mitochondria per BS cell, distribution of these organelles to the centripetal region of BS cells, the degree of inner positioning (vacuolar side of chloroplasts) of mitochondria in M cells, and the size of BS mitochondria also changed with the change in glycine decarboxylase localization. All Chenopodium species examined were C3-like regarding activities and amounts of C3 and C4 photosynthetic enzymes and δ13C values, suggesting that these species perform photosynthesis without contribution of the C4 cycle. This study demonstrates that Chenopodium is not a C3 genus and is valuable for studying evolution of C3–C4 intermediates. 相似文献
9.
Abstract. The photosynthetic responses to temperature in C 3, C 3-C 4 intermediate, and C 4 species in the genus Flaveria were examined in an effort to identify whether the reduced photorespiration rates characteristic of C 3-C 4 intermediate photosynthesis result in adaptive advantages at warm leaf temperatures. Reduced photorespiration rates were reflected in lower CO 2 compensation points at all temperatures examined in the C 3-C 4 intermediate, Flaveria floridana, compared to the C 3 species, F. cronquistii. The C 3-C 4 intermediate, F. floridana, exhibited a C 3-like photosynthetic temperature dependence, except for relatively higher photosynthesis rates at warm leaf temperatures compared to the C 3 species, F. cronquistii. Using models of C 3 and C 3-C 4 intermediate photosynthesis, it was predicted that by recycling photorespired CO 2 in bundle-sheath cells, as occurs in many C 3-C 4 intermediates, photosynthesis rates at 35°C could be increased by 28%, compared to a C 3 plant. Without recycling photorespired CO 2, it was calculated that in order to improve photosynthesis rates at 35°C by this amount in C 3 plants, (1) intercellular CO 2 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 CO 2, leaves of F. floridana appear to effectively concentrate CO 2 at the active site of RuBP carboxylase, increasing the apparent carboxylation efficiency per unit of in vitro RuBP carboxylase activity. The CO 2-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 C 3-C 4 intermediate, F. ramosissima, exhibited a photosynthetic temperature temperature response curve that was more similar to the C 4 species, F. trinervia, than the C 3 species, F. cronquistii. The C 4-like pattern is probably related to the advanced nature of C 4-like biochemical traits in F. ramosissima The results demonstrate that reductions in photorespiration rates in C 3-C 4 intermediate plants create photosynthetic advantages at warm leaf temperatures that in C 3 plants could only be achieved through substantial costs to water-use efficiency and/or nitrogen-use efficiency. 相似文献
10.
During the last Ice age, CO2 concentration ([CO2]) was 180-200 μmol/mol compared with the modern value of 380 μmol/mol,and global temperatures were ~8 ℃ cooler. Relatively little is known about the responses of C3 and C4 species to longterm exposure to glacial conditions. Here Abutilon theophrasti Medik. (C3) and Amaranthus retroflexus L. (C4) were grown at 200 μmol/mol CO2 with current (30/24 ℃) and glacial (22/16 ℃) temperatures for 22 d. Overall, the C4 species exhibited a large growth advantage over the C3 species at low [CO2]. However, this advantage was reduced at low temperature, where the C4 species produced 5× the total mass of the C3 species versus 14× at the high temperature.This difference was due to a reduction In C4 growth at low temperature, since the C3 species exhibited similar growth between temperatures. Physiological differences between temperatures were not detected for either species, although photorespirationlnet photosynthesis was reduced in the C3 species grown at low temperature, suggesting evidence of improved carbon balance at this treatment. This system suggests that C4 species had a growth advantage over C3 species during low [CO2] of the last ice age, although concurrent reductions in temperatures may have reduced this advantage. 相似文献
11.
While temperature responses of photosynthesis and plant respiration are known to acclimate over time in many species, few studies have been designed to directly compare process‐level differences in acclimation capacity among plant types. We assessed short‐term (7 day) temperature acclimation of the maximum rate of Rubisco carboxylation ( Vcmax), the maximum rate of electron transport ( Jmax), the maximum rate of phosphoenolpyruvate carboxylase carboxylation ( Vpmax), and foliar dark respiration ( Rd) in 22 plant species that varied in lifespan (annual and perennial), photosynthetic pathway (C 3 and C 4), and climate of origin (tropical and nontropical) grown under fertilized, well‐watered conditions. In general, acclimation to warmer temperatures increased the rate of each process. The relative increase in different photosynthetic processes varied by plant type, with C 3 species tending to preferentially accelerate CO 2‐limited photosynthetic processes and respiration and C 4 species tending to preferentially accelerate light‐limited photosynthetic processes under warmer conditions. Rd acclimation to warmer temperatures caused a reduction in temperature sensitivity that resulted in slower rates at high leaf temperatures. Rd acclimation was similar across plant types. These results suggest that temperature acclimation of the biochemical processes that underlie plant carbon exchange is common across different plant types, but that acclimation to warmer temperatures tends to have a relatively greater positive effect on the processes most limiting to carbon assimilation, which differ by plant type. The acclimation responses observed here suggest that warmer conditions should lead to increased rates of carbon assimilation when water and nutrients are not limiting. 相似文献
12.
In order to reveal the drought resistance and adaptation of the C 4 desert plant Haloxylon ammodendron under artificially controlled soil moisture regimes, representative plants were selected to measure canopy photosynthesis
using canopy photosynthetic measurement system. The results showed that appropriate soil moisture significantly enhances the
canopy and leaf photosynthetic capacity, and extremely high soil moisture is not conducive to the photosynthesis of H. ammodendron. 相似文献
13.
Summary Field measurements of photosynthetic CO 2 exchange were made on saplings of a C 4 tree species, Euphorbia forbesii, and a C 3 tree species, Claoxylon sandwicense, in a shaded mesic forest on Oahu, Hawaii. Both species had light responses typical of those generally found in shade plants. Light saturated photosynthetic rates were 7.15 and 4.09 mol m 2 s 1 and light compensation points were 6.3 and 1.7 mol m 2 s 1 in E. forbesii and C. sandwicense, respectively. E. forbesii maintained a higher mesophyll conductance and a higher water use efficiency than C. sandwicense as is typically found in comparisons of C 4 and C 3 plants. Under natural light regimes, both species maintained positive CO 2 uptake rates over essentially the entire day because of low respiration rates and light compensation points. However, photosynthesis during sunflecks accounted for a large fraction of the daily carbon gain. The results show that the carbon-gaining capacity of E. forbesii is comparable to that of a C 3 species in a moderately cool, shaded forest environment. There appears to be no particular advantage or disadvantage associated with the C 4 photosynthetic pathway of E. forbesii in this environment. 相似文献
14.
Summary Laboratory and field gas exchange measurements were made on C 3 ( Scirpus olneyi Gray) and C 4 ( Spartina patens (Ait.) Mahl., Distichlis spicata (L.) Green) species from an irregularly flooded tidal marsh on the Chesapeake Bay. Laboratory measurements were made on plants grown from root stocks that were transplanted to a greenhouse and grown under high light and high nutrient conditions. The two C 4 species were similar in their laboratory gas exchange characteristics: both had higher net carbon exchange rates, higher mesophyll conductances, higher photosynthetic temperature optima and lower leaf conductances than the C 3 species. The laboratory photosynthetic water use efficiency of the C 4 species was approximately three times that of the C 3 species.Field gas exchange responses of the above species were measured in situ a Chesapeake Bay tidal marsh. Despite differences in biological potential measured in the laboratory, all three species had similar in situ carbon exchange rates on a leaf area basis. On a dry weight basis, leaves of the two C 4 species had about 1.4 times higher light saturated CO 2 assimilation rates than the C 3 species. Light saturation of CO 2 exchange occurred at photosynthetic photon flux densities of 80 n Einstein cm -2s -1, compared with 160 n Einstein cm -2s -1 in the laboratory grown plants. Spartina patens and Scirpus olneyi had similar daily CO 2 assimilation rates, but the daily transpiration rate of the C 3 species was almost twice that of the C 4 species. Spartina patens showed greater seasonal decrease in photosynthesis than Distichlis spicata and Scirpus olneyi. The two C 4 grass species maintained higher mesophyll conductances and photosynthetic water use efficiencies than the C 4 sedge. 相似文献
15.
We studied gas exchange of leaves on branches that had been cut and then re-cut under water to assess the utility of measuring gas exchange on leaves of excised canopy branches. There was large variation between species in their ability to photosynthesize following excision. Some species maintained up to 86.5% of intact photosynthetic rate 60 min after excision, whereas other species dropped below 40% of intact photosynthetic rates within 3 min. Three species showed significant reductions in maximum rates of gross photosynthetic rate ( P
G) on leaves of excised branches relative to intact branches. Excision significantly reduced carboxylation rates ( Vc
max) in four species and electron transport ( J
max) in two species. There were also significant increases in compensation irradiance and reductions of day rates of respiration relative to intact measurements. While gas exchange on excised branches can provide useful measures for canopy species, responses of individual species to branch excision need to be taken into account. Measurements on pre-screened species allow a greater understanding of canopy photosynthesis of large trees when canopy access is not an option. 相似文献
16.
Summary Carbon fixation by CAM at high night temperatures was examined in the stem succulent, Opuntia basilaris. Nighttime accumulation of titratable acids was uniformly high among plants growing naturally along an altitudinal temperature gradient in Death Valley, California during the hot summer period. Plants grown at high temperature regimes (40°/30°C) had rates of CAM and C 3 fixation similar to rates observed in plants maintained at a cool temperature (20°/10°C). C 3 fixation comprised 30% of the total carbon fixed by the potted, well watered plants. However, when pads were excised, C 3 fixation was suppressed while CAM continued unabated. 相似文献
17.
Continually rising atmospheric CO 2 concentrations and possible climatic change may cause significant changes in plant communities. This study was undertaken to investigate gas exchange in two important grass species of the short-grass steppe, Pascopyrum smithii (western wheat-grass), C 3, and Bouteloua gracilis (blue grama), C4, grown at different CO 2 concentrations and temperatures. Intact soil cores containing each species were extracted from grasslands in north-eastern Colorado, USA, placed in growth chambers, and grown at combinations of two CO 2 concentrations (350 and 700 μmol mol −1) and two temperature regimes (field average and elevated by 4°C). Leaf gas exchange was measured during the second, third and fourth growth seasons. All plants exhibited higher leaf CO 2 assimilation rates ( A) with increasing measurement CO 2 concentration, with greater responses being observed in the cool-season C 3 species P. smithii. Changes in the shape of intercellular CO 2 response curves of A for both species indicated photosynthetic acclimation to the different growth environments. The photosynthetic capacity of P. smithii leaves tended to be reduced in plants grown at high CO 2 concentrations, although A for plants grown and measured at 700μmol mol −1 CO 2 was 41% greater than that in plants grown and measured at 350 μmol mol −1 CO 2. Low leaf N concentration may have contributed to photosynthetic acclimation to CO 2. A severe reduction in photosynthetic capacity was exhibited in P. smithii plants grown long-term at elevated temperatures. As a result, the potential response of photosynthesis to CO 2 enrichment was reduced in P. smithii plants grown long-term at the higher temperature. 相似文献
18.
At micro‐site scale, the spatial pattern of a plant species depends on several factors including interactions with neighbours. It has been seen that unfavourable effects generate a negative association between plants, while beneficial effects generate a positive association. In grasslands, the presence of shrubby species promotes a particular microenvironment beneath their canopy that could affect differently the spatial distribution of plants with different tolerance to abiotic conditions. We measured photosynthetic active radiation, air temperature and wind speed under shrub canopies and in adjacent open sites and analysed the spatial distribution of four grass species (two C 3 and two C 4) in relation to shrub canopy in a grazed sub‐humid natural grassland in southern Uruguay. Radiation, air temperature and wind speed were lower under shrubs than in adjacent open sites. The spatial distribution of grasses relative to the shrub canopy varied depending on the photosynthetic metabolism of grasses. C 4 grasses showed a negative association or no correlation with the shrubs, whereas C 3 grasses showed a positive association. Our results highlight the importance of the photosynthetic metabolism of the grasses in the final outcome of interactions between grasses and shrubs. Micro‐environmental conditions generated underneath shrubs create a more suitable site for the establishment of C 3 than for C 4 grasses. These results show that facilitation could be more important than previously thought in sub‐humid grasslands. 相似文献
19.
C 4 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 C 3 species. In the present study we tested the hypothesis that low‐temperature photo‐inhibition is more detrimental to carbon gain in the C 4 grass Muhlenbergia glomerata than the C 3 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 C 3 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 C 4 species may tolerate cool climates and overcome the Rubisco limitation that is prevalent at low temperatures in C 4 plants. 相似文献
20.
The effects of soil-water potential, temperature, and visibleirradiance interactions on net photo-synthetic and dark respirationrates of Pennisetum purpureum Schumach., a tropical C 4 grassand Calopogonium mucunoides Desv., a C 3 leguminous herb werestudied. The net photosynthetic rates of the two species decreased withdecreasing soil water potential and at all levels of irradianceconsidered. Similarly, the net photosynthetic rates of the twospecies decreased as soil water potential decreased at all temperatures. The C 4 species reached light saturation at very high irradiancewhereas the light saturation of the C 3 species occurred at relativelylow irradiance at high temperatures and low soil water potential. The dark respiration rates decreased with decreasing soil waterpotential and increased as temperature increased from 20 °Cto 40 °C. Key words: Soil water potential, Temperature, Irradiance, Photosynthesis, Respiration, Tropical weeds 相似文献
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