共查询到20条相似文献,搜索用时 781 毫秒
1.
Leaf photosynthesis, plant growth and nitrogen allocation in rice under different irradiances 总被引:6,自引:0,他引:6
The photosynthetic rates and various components of photosynthesis including ribulose-1,5-bisphosphate carboxylase (Rubisco;
EC 4.1.1.39), chlorophyll (Chl), cytochrome (Cyt) f, and coupling factor 1 (CF1) contents, and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity were examined in young, fully expanded leaves of rice
(Oryza sativa L.) grown hydroponically under two irradiances, namely, 1000 and 350 μmol quanta · m−2 · s−1, at three N concentrations. The light-saturated rate of photosynthesis measured at 1800 μmol · m−2 · s−1 was almost the same for a given leaf N content irrespective of growth irradiance. Similarly, Rubisco content and SPS activity
were not different for the same leaf N content between irradiance treatments. In contrast, Chl content was significantly greater
in the plants grown at 350 μmol · m−2 · s−1, whereas Cyt f and CF1 contents tended to be slightly smaller. However, these changes were not substantial, as shown by the fact that the light-limited
rate of photosynthesis measured at 350 μmol · m−2 · s−1 was the same or only a little higher in the plants grown at 350 μmol · m−2 · s−1 and that CO2-saturated photosynthesis did not differ between irradiance treatments. These results indicate that growth-irradiance-dependent
changes in N partitioning in a leaf were far from optimal with respect to N-use efficiency of photosynthesis. In spite of
the difference in growth irradiance, the relative growth rate of the whole plant did not differ between the treatments because
there was an increase in the leaf area ratio in the low-irradiance-grown plants. This increase was associated with the preferential
N-investment in leaf blades and the extremely low accumulation of starch and sucrose in leaf blades and sheaths, allowing
a more efficient use of the fixed carbon. Thus, morphogenic responses at the whole-plant level may be more important for plants
as an adaptation strategy to light environments than a response of N partitioning at the level of a single leaf.
Received: 23 February 1997 / Accepted: 8 May 1997 相似文献
2.
Photosynthetic acclimation of maize to growth under elevated levels of carbon dioxide 总被引:4,自引:0,他引:4
The effects of elevated CO2 concentrations on the photochemistry, biochemistry and physiology of C4 photosynthesis were studied in maize (Zea mays L.). Plants were grown at ambient (350 μL L−1) or ca. 3 times ambient (1100 μL L−1) CO2 levels under high light conditions in a greenhouse for 30 d. Relative to plants grown at ambient CO2 levels, plants grown under elevated CO2 accumulated ca. 20% more biomass and 23% more leaf area. When measured at the CO2 concentration of growth, mature leaves of high-CO2-grown plants had higher light-saturated rates of photosynthesis (ca. 15%), lower stomatal conductance (71%), higher water-use
efficiency (225%) and higher dark respiration rates (100%). High-CO2-grown plants had lower carboxylation efficiencies (23%), measured under limiting CO2, and lower leaf protein contents (22%). Activities of a number of C3 and C4 cycle enzymes decreased on a leaf-area basis in the high-CO2-grown plants by 5–30%, with NADP-malate dehydrogenase exhibiting the greatest decrease. In contrast, activities of fructose
1,6-bisphosphatase and ADP-glucose pyrophosphorylase increased significantly under elevated CO2 condition (8% and 36%, respectively). These data show that the C4 plant maize may benefit from elevated CO2 through acclimation in the capacities of certain photosynthetic enzymes. The increased capacity to synthesize sucrose and
starch, and to utilize these end-products of photosynthesis to produce extra energy by respiration, may contribute to the
enhanced growth of maize under elevated CO2.
Received: 30 April 1999 / Accepted: 17 June 1999 相似文献
3.
To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending
on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 μmol m−2 s−1) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a
control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 μmol m−2 s−1. The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 μmol m−2 s−1 and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300–1600 μmol m−2 s−1). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite
content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase
and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 μmol m−2 s−1 or in the glasshouse than in plants grown at 330 μmol m−2 s−1. Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar
under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 μmol m−2 s−1 can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate.
This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase
and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate.
This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.
Received: 15 November 1999 / Accepted: 27 January 2000 相似文献
4.
Pilar Pérez Aitor Alonso Gloria Zita Rosa Morcuende Rafael Martínez-Carrasco 《Plant Growth Regulation》2011,65(3):439-447
Increases in growth temperature have been observed to affect photosynthesis differently under long-term exposure to ambient-
and twice ambient-air CO2 concentrations. This study investigates the causes of this interaction in wheat (Triticum aestivum L.) grown in the field over two consecutive years under temperature gradient chambers in ambient (370 μmol mol−1) or elevated (700 μmol mol−1) atmospheric CO2 concentrations and at ambient or ambient +4°C temperatures, with either a low or a high nitrogen supply. The photosynthesis-internal
CO2 response curves and the activity, activation state, kcat and amount of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) were measured, as well as the soluble protein concentration
in flag leaves at ear emergence and 8–15 days after anthesis. A high nitrogen supply increased Vcmax, the Rubisco amount and activity and soluble protein contents, but did not significantly change the Rubisco kcat. Both elevated CO2 and above ambient temperatures had negative effects on Vcmax and Rubisco activity, but at elevated CO2, an increase in temperature did not decrease Vcmax or Rubisco activity in relation to ambient temperature. The amounts of Rubisco and soluble protein decreased with elevated
CO2 and temperature. The negative impact of elevated CO2 on Rubisco properties was somewhat counteracted at elevated temperatures by an increase in kcat. This effect can diminish the detrimental effects on photosynthesis of combined increases of CO2 and temperature. 相似文献
5.
J. D. Barnes I. Bettarini A. Polle N. Slee C. Raines F. Miglietta A. Raschi M. Fordham 《Oecologia》1997,110(2):169-178
The aim of this study was to characterise growth and photosynthetic capacity in plants adapted to long-term contrasting atmospheric
CO2 concentrations (C
a). Seeds of Agrostis canina L. ssp. monteluccii were collected from a natural CO2 transect in central-western Italy and plants grown in controlled environment chambers at both ambient and elevated CO2 (350 and 700 μmol mol−1) in nutrient-rich soil. Seasonal mean C
a at the source of the plant material ranged from 610 to 451 μmol CO2 mol−1, derived from C4 leaf stable carbon isotope discrimination (δ13C). Under chamber conditions, CO2 enrichment stimulated the growth of all populations. However, plants originating from elevated C
a exhibited higher initial relative growth rates (RGRs) irrespective of chamber CO2 concentrations and a positive relationship was found between RGR and C
a at the seed source. Seed weight was positively correlated with C
a, but differences in seed weight were found to explain no more than 34% of the variation in RGRs at elevated CO2. Longer-term experiments (over 98 days) on two populations originating from the extremes of the transect (451 and 610 μmol
CO2 mol−1) indicated that differences in growth between populations were maintained when plants were grown at both 350 and 700 μmol
CO2 mol−1. Analysis of leaf material revealed an increase in the cell wall fraction (CWF) in plants grown at elevated CO2, with plants originating from high C
a exhibiting constitutively lower levels but a variable response in terms of the degree of lignification. In vivo gas exchange measurements revealed no significant differences in light and CO2 saturated rates of photosynthesis and carboxylation efficiency between populations or with CO2 treatment. Moreover, SDS-PAGE/ LISA quantification of leaf ribulose bisphosphate carboxylase/oxygenase (Rubisco) showed no
difference in Rubisco content between populations or CO2 treatments. These findings suggest that long-term adaptation to growth at elevated CO2 may be associated with a potential for increased growth, but this does not appear to be linked with differences in the intrinsic
capacity for photosynthesis.
Received: 16 August 1996 / Accepted: 19 October 1996 相似文献
6.
L. Balaguer E. Manrique A. de los Rios C. Ascaso K. Palmqvist M. Fordham J. D. Barnes 《Oecologia》1999,119(2):166-174
Acclimation to elevated CO2 was investigated in Parmelia caperata originating from the vicinity of a natural CO2 spring, where the average daytime CO2 concentration was 729 ± 39 μmol mol−1 dry air. Thalli showed no evidence of a down-regulation in photosynthetic capacity following long-term exposure to CO2 enrichment in the field; carboxylation efficiency, total Ribulose bisphosphate carboxylase/oxygenase (Rubisco) content, apparent
quantum yield of CO2 assimilation, and the light-saturated rate of CO2 assimilation (measured under ambient and saturating CO2 concentrations) were similar in thalli from the naturally CO2 enriched site and an adjacent control site where the average long-term CO2 concentration was about 355 μmol mol−1. Thalli from both CO2 environments exhibited low CO2 compensation points and early saturation of CO2 uptake kinetics in response to increasing external CO2 concentrations, suggesting the presence of an active carbon-concentrating mechanism. Consistent with the lack of significant
effects on photosynthetic metabolism, no changes were found in the nitrogen content of thalli following prolonged exposure
to elevated CO2. Detailed intrathalline analysis revealed a decreased investment of nitrogen in Rubisco in the pyrenoid of algae located
in the elongation zone of thalli originating from elevated CO2, an effect associated with a reduction in the percentage of the cell volume occupied by lipid bodies and starch grains. Although
these differences did not affect the photosynthetic capacity of thalli, there was evidence of enhanced limitations to CO2 assimilation in lichens originating from the CO2-enriched site. The light-saturated rate of CO2 assimilation measured at the average growth CO2 concentration was found to be significantly lower in thalli originating from a CO2-enriched atmosphere compared with that of thalli originating and measured at ambient CO2. At lower photosynthetic photon flux densities, the light compensation point of net CO2 assimilation was significantly higher in thalli originating from elevated CO2, and this effect was associated with higher usnic acid content.
Received: 8 May 1998 / Accepted: 22 January 1999 相似文献
7.
The effect of short-term exposure to elevated CO2 concentration and high irradiance on the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases
(GPX) and catalase (CAT), and on the extent of the lipid peroxidation was studied in bean (Phaseolus vulgaris L.) plants. Plants were exposed for 4 d (8 h a day) to irradiance of 100 (LI) or 1000 (HI) μmol m−2 s−1 at ambient (CA, 350 μmol mol−1) or elevated (CE, 1300 μmol mol−1) CO2 concentration. Four-day exposure to CE increased the leaf dry mass in HI plants and RuBPC activity and chlorophyll content
in LI plants. Total soluble protein content, leaf dry matter and RuBPC activity were higher in HI than in LI plants, although
the HI and CE increased the contents of malonyldialdehyde and H2O2. Under CA, exposure to HI increased the activity of APX and decreased the total SOD activity. Under CE, HI treatment also
activated APX and led to reduction of both, SOD and GPX, enzymes activities. CE considerably reduced the CAT activity at both
irradiances, possibly due to suppressed rate of photorespiration under CE conditions. 相似文献
8.
Gas-exchange measurements were performed to analyze the leaf conductances and assimilation rates of potato (Solanum tuberosum L. cv. Desireé) plants expressing an antisense construct against chloroplastic fructose-1,6-bisphosphatase (FBPase, EC 3.1.3.11)
in response to increasing photon flux densities, different relative air humidities and elevated CO2 concentrations. Assimilation rates (A) and transpiration rates (E) were observed during a stepwise increase of photon flux
density. These experiments were carried out under atmospheric conditions and in air containing 500 μmol mol−1 CO2. In both gas atmospheres, two levels of relative air humidity (60–70% and 70–80%) were applied in different sets of measurements.
Intercellular CO2 concentration, leaf conductance, air-to-leaf vapour pressure deficit, and instantaneous water-use efficiency (A/E) were determined.
As expected, assimilation rates of the FBPase antisense plants were significantly reduced as compared to the wild type. Saturation
of assimilation rates in transgenic plants occurred at a photon flux density of 200 μmol m−2 s−1, whereas saturation in wild type plants was observed at 600 μmol m−2 s−1. Elevated ambient CO2 levels did not effect assimilation rates of transgenic plants. At 70–80% relative humidity and atmospheric CO2 concentration the FBPase antisense plants had significantly higher leaf conductances than wild-type plants while no difference
emerged at 60–70%. These differences in leaf conductance vanished at elevated levels of ambient CO2. Stomatal response to different relative air humidities was not affected by mesophyll photosynthetic activity. It is suggested
that the regulation of stomatal opening upon changes in photon flux density is merely mediated by a signal transmitted from
mesophyll cells, whereas the intercellular CO2 concentration plays a minor role in this kind of stomatal response. The results are discussed with respect to stomatal control
by environmental parameters and mesophyll photosynthesis.
Received: 24 September 1998 / Accepted: 9 February 1999 相似文献
9.
Photosynthetic nitrogen-use efficiency of species that differ inherently in specific leaf area 总被引:42,自引:0,他引:42
Factors that contribute to interspecific variation in photosynthetic nitrogen-use efficiency (PNUE, the ratio of CO2 assimilation rate to leaf organic nitrogen content) were investigated, comparing ten dicotyledonous species that differ inherently
in specific leaf area (SLA, leaf area:leaf dry mass). Plants were grown hydroponically in controlled environment cabinets
at two irradiances (200 and 1000 μmol m–2 s–1). CO2 and irradiance response curves of photosynthesis were measured followed by analysis of the chlorophyll, Rubisco, nitrate
and total nitrogen contents of the leaves. At both irradiances, SLA ranged more than twofold across species. High-SLA species
had higher in situ rates of photosynthesis per unit leaf mass, but similar rates on an area basis. The organic N content per
unit leaf area was lower for the high-SLA species and consequently PNUE at ambient light conditions (PNUEamb) was higher in those plants. Differences were somewhat smaller, but still present, when PNUE was determined at saturating
irradiances (PNUEmax). An assessment was made of the relative importance of the various factors that underlay interspecific variation in PNUE.
For plants grown under low irradiance, PNUEamb of high-SLA species was higher primarily due to their lower N content per unit leaf area. Low-SLA species clearly had an
overinvestment in photosynthetic N under these conditions. In addition, high SLA-species allocated a larger fraction of organic
nitrogen to thylakoids and Rubisco, which further increased PNUEamb. High-SLA species grown under high irradiance showed higher PNUEamb mainly due to a higher Rubisco specific activity. Other factors that contributed were again their lower contents of Norg per unit leaf area and a higher fraction of photosynthetic N in electron transport and Rubisco. For PNUEmax, differences between species in organic leaf nitrogen content per se were no longer important and higher PNUEmax of the high SLA species was due to a higher fraction of N in␣photosynthetic compounds (for low-light plants) and a higher
Rubisco specific activity (for high-light grown plants).
Received: 11 October 1997 / Accepted: 9 April 1998 相似文献
10.
Carlos Eduardo Aragón Maritza Escalona Roberto Rodriguez Maria Jesús Cañal Iris Capote Danilo Pina Justo González-Olmedo 《In vitro cellular & developmental biology. Plant》2010,46(1):89-94
In vitro physiology and carbon metabolism can be affected by the sink–source relationship. The effect of different sucrose concentrations
(10, 30, and 50 g L−1), light intensities (80 and 150 μmol m−2 s−1), and CO2 levels (375 and 1,200 μmol mol−1) were tested during plantain micropropagation in temporary immersion bioreactors. Activities of pyruvate kinase, phosphoenol
pyruvate carboxylase, and the photosynthesis rate were recorded. From the morphological and practical point of view, the best
results were obtained when plants were cultured with 30 g L−1 sucrose, 80 μmol m−2 s−1 light intensity, and 1,200 μmol mol−1 CO2 concentration. This treatment improved leaf and root development, reduced respiration during in vitro culture, and increased starch level at the end of the hardening phase. In addition to that, the number of competent plants
was increased from 80.0% to 91.0% at the end of the in vitro phase and the survival percentage from 95.71% to 99.80% during ex vitro hardening. 相似文献
11.
I. R. Sanders R. Streitwolf-Engel M. G. A. van der Heijden T. Boller A. Wiemken 《Oecologia》1998,117(4):496-503
Prunella vulgaris was inoculated with different arbuscular mycorrhizal fungi (AMF) and grown at two concentrations of CO2 (ambient, 350 μl l−1, and elevated, 600 μl l−1) to test whether a plants response to elevated CO2 is dependent on the species of AMF colonizing the roots. Using compartments accessible only to AMF hyphae but not to roots,
we also tested whether elevated CO2 affects the growth of external AMF hyphae. Plant biomass was significantly greater at elevated than at ambient CO2; the biomass of the root system, for example, increased by a factor of 2. The colonization of AMF inside the root remained
constant, indicating that the total AMF inside the root system also increased by a factor of 2. The length of external AMF
hyphae at elevated CO2 was up to 5 times that at ambient CO2, indicating that elevated CO2 promoted allocation of AMF biomass to the external hyphae. The concentration and content of phosphorus in the stolons differed
significantly between ambient and elevated CO2 but this resulted in either an increase or a decrease, according to which AMF isolate occupied the roots. We hypothesized
that an increase in external hyphal growth at elevated CO2 would result in increased P acquistion by the plant. To test this we supplied phosphorus, in a compartment only accessible
to AMF hyphae. Plants did not acquire more phosphorus at elevated CO2 when phosphorus was added to this compartment. Large increases in AMF hyphal growth could, however, play a significant role
in the movement of fixed carbon to the soil and increase soil aggregation.
Received: 28 March 1998 / Accepted: 27 August 1998 相似文献
12.
To examine the role of sink size on photosynthetic acclimation under elevated atmospheric CO2 concentrations ([CO2]), we tested the effects of panicle-removal (PR) treatment on photosynthesis in rice (Oryza sativa L.). Rice was grown at two [CO2] levels (ambient and ambient + 200 μmol mol−1) throughout the growing season, and at full-heading stage, at half the plants, a sink-limitation treatment was imposed by
the removal of the panicles. The PR treatment alleviated the reduction of green leaf area, the contents of chlorophyll (Chl)
and Rubisco after the full-heading stage, suggesting delay of senescence. Nonetheless, elevated [CO2] decreased photosynthesis (measured at current [CO2]) of plants exposed to the PR treatment. No significant [CO2] × PR interaction on photosynthesis was observed. The decrease of photosynthesis by elevated [CO2] of plants was associated with decreased leaf Rubisco content and N content. Leaf glucose content was increased by the PR
treatment and also by elevated [CO2]. In conclusion, a sink-limitation in rice improved N status in the leaves, but this did not prevent the photosynthetic down-regulation
under elevated [CO2]. 相似文献
13.
Guanghui Lin John Adams Blake Farnsworth Yongdan Wei Bruno D. V. Marino Joseph A. Berry 《Oecologia》1999,119(1):97-108
The ecosystem-level carbon uptake and respiration were measured under different CO2 concentrations in the tropical rainforest and the coastal desert of Biosphere 2, a large enclosed facility. When the mesocosms
were sealed and subjected to step-wise changes in atmospheric CO2 between daily means of 450 and 900 μmol mol−1, net ecosystem exchange (NEE) of CO2 was derived using the diurnal changes in atmospheric CO2 concentrations. The step-wise CO2 treatment was effectively replicated as indicated by the high repeatability of NEE measurements under similar CO2 concentrations over a 12-week period. In the rainforest mesocosm, daily NEE was increased significantly by the high CO2 treatments because of much higher enhancement of canopy CO2 assimilation relative to the increase in the nighttime ecosystem respiration under high CO2. Furthermore, the response of daytime NEE to increasing atmospheric CO2 in this mesocosm was not linear, with a saturation concentration of 750 μmol mol−1. In the desert mesocosm, a combination of a reduction in ecosystem respiration and a small increase in canopy CO2 assimilation in the high CO2 treatments also enhanced daily NEE. Although soil respiration was not affected by the short-term change in atmospheric CO2 in either mesocosm, plant dark respiration was increased significantly by the high CO2 treatments in the rainforest mesocosm while the opposite was found in the desert mesocosm. The high CO2 treatments increased the ecosystem light compensation points in both mesocosms. High CO2 significantly increased ecosystem radiation use efficiency in the rainforest mesocosm, but had a much smaller effect in the
desert mesocosm. The desert mesocosm showed much lower absolute response in NEE to atmospheric CO2 than the rainforest mesocosm, probably because of the presence of C4 plants. This study illustrates the importance of large-scale experimental research in the study of complex global change
issues.
Received: 30 October 1998 / Accepted: 2 December 1998 相似文献
14.
CO2 exchange of the endolithic lichen Verrucaria baldensis was measured in the laboratory under different conditions of water content, temperature, light, and CO2 concentration. The species had low CO2 exchange rates (maximum net photosynthesis: c. 0.45 μmol CO2 m−2 s−1; maximum dark respiration: c. 0.3 μmol CO2 m−2 s−1) and a very low light compensation point (7 μmol photons m−2 s−1 at 8°C). The net photosynthesis/respiration quotient reached a maximum at 9–15°C. Photosynthetic activity was affected only
after very severe desiccation, when high resaturation respiratory rates were measured. Microclimatic data were recorded under
different weather conditions in an abyss of the Trieste Karst (northeast Italy), where the species was particularly abundant.
Low photosynthetically active radiation (normally below 40 μmol photons m−2 s−1), very high humidities (over 80%), and low, constant temperatures were measured. Thallus water contents sufficient for CO2 assimilation were often measured in the absence of condensation phenomena.
Received: 22 September 1996 / Accepted: 26 April 1997 相似文献
15.
Elena Litchman 《Oecologia》1998,117(1-2):247-257
Light is a major resource in aquatic ecosystems and has a complex pattern of spatio-temporal variability, yet the effects
of dynamic light regimes on communities of phytoplankton are largely unexplored. I examined whether and how fluctuating light
supply affects the structure and dynamics of phytoplankton communities. The effect of light fluctuations was tested at two
average irradiances: low, 25 μmol quanta m−2 s−1 and high, 100 μmol quanta m−2 s−1 in 2- and 18-species communities of freshwater phytoplankton. Species diversity, and abundances of individual species and
higher taxa, depended significantly on both the absolute level and the degree of variability in light supply, while total
density, total biomass, and species richness responded only to light level. In the two-species assemblage, fluctuations increased
diversity at both low and high average irradiances and in the multispecies community fluctuations increased diversity at high
irradiance but decreased diversity at low average irradiance. Species richness was higher under low average irradiance and
was not affected by the presence or absence of fluctuations. Diatom abundance was increased by fluctuations, especially at
low average irradiance, where they became the dominant group, while cyanobacteria and green algae dominated low constant light
and all high light treatments. Within each taxonomic group, however, there was no uniform pattern in species responses to
light fluctuations: both the magnitude and direction of response were species-specific. The temporal regime of light supply
had a significant effect on the growth rates of individual species grown in monocultures. Species responses to the regime
of light supply in monocultures qualitatively agreed with their abundances in the community experiments. The results indicate
that the temporal regime of light supply may influence structure of phytoplankton communities by differentially affecting
growth rates and mediating species competition.
Received: 24 September 1997 / Accepted: 8 July 1998 相似文献
16.
Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to differential responses of overstory and understory plants or plant parts. In the long term, seedling recruitment,
competition, and thus population or community structure may be affected. Aside from the possible differential direct effects
of elevated CO2 on photosynthesis and growth, both the quantity and quality of the light below the overstory canopy could be indirectly affected
by CO2-induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order to explore such possible
interactions, we compared canopy leaf area development, canopy light extinction and the quality of light beneath overstory
leaves of two-storied monospecific stands ofRicinus communis exposed to ambient (340 μl l−1) and elevated (610 μl l−1) CO2. Plants in each stand were grown in a common soil as closed “artificial ecosystems” with a ground area of 6.7 m2. LAI of overstory plants in all ecosystems more than doubled during the experiment but was not different between CO2 treatments at the end. As a consequence, extinction of photosynthetically active radiation (PAR) was also not altered. However,
under elevated CO2 the red to far-red ratio (R:FR) measured beneath overstory leaves was 10% lower than in ecosystems treated with ambient CO2. This reduction was associated with increased thickness of palisade layers of overstory leaves and appears to be a plausible
explanation for the specific enhancement of stem elongation of understory plants (without a corresponding biomass response)
under elevated CO2. CO2 enrichment led to increased biomass of overstory plants (mainly stem biomass) but had no effect on understory biomass. The
results of this study raise the possibility of an important indirect effect of elevated CO2 at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio beneath overstory canopies may affect understory plant development independently of the effects
of PAR extinction. 相似文献
17.
The effect of elevated CO2 concentration and nutrient supply on carbon-based plant secondary metabolites in Pinus sylvestris L. 总被引:3,自引:0,他引:3
This study investigated changes in carbon-based plant secondary metabolite concentrations in the needles of Pinus sylvestris saplings, in response to long-term elevation of atmospheric CO2, at two rates of nutrient supply. Experimental trees were grown for 3 years in eight open-top chambers (OTCs), four of which
were maintained at ambient (∼350 μmol mol−1) and four at elevated (700 μmol mol−1) CO2 concentrations, plus four open air control plots. Within each of these treatments, plants received either high (7.0 g N m−2 year−1 added) or low (no nutrients added) rates of nutrient supply for two years. Needles from lateral branches were analysed chemically
for concentrations of condensed tannins and monoterpenes. Biochemical determinations of cellulase digestibility and protein
precipitating capacity of their phenolic extracts were made because of their potential of importance in ecological interactions
between pine and other organisms including herbivores and decomposers. Elevated CO2 concentration caused an increase (P<0.05) in dry mass per needle, tree height and the concentration of the monoterpene α-pinene, but there were no direct effects
of CO2 concentration on any of the other chemical measurements made. High nutrient availability increased cellulase digestibility
of pine needles. There was a significant negative effect of the OTCs on protein precipitating capacity of the needle extracts
in comparison to the open-air controls. Results suggest that predicted changes in atmospheric CO2 concentration will be insufficient to produce large changes in the concentration of condensed tannins and monoterpenes in
Scots pine. Processes which are influenced by these compounds, such as decomposition and herbivore food selection, along with
their effects on ecosystem functioning, are therefore unlikely to be directly affected through changes in these secondary
metabolites.
Received: 20 October 1997 / Accepted: 28 February 1998 相似文献
18.
Liang C Xiao W Hao H Xiaoqing L Chao L Lei Z Fashui H 《Biological trace element research》2008,121(3):249-257
Mg2+ in various concentrations was added to purified Rubisco in vitro to gain insight into the mechanism of molecular interactions
between Mg2+ and Rubisco. The enzyme activity assays showed that the reaction between Rubisco and Mg2+ was two order, which means that the enhancement of Rubisco activity was accelerated by low concentration of Mg2+ and slowed by high concentration of Mg2+. The kinetics constant (K
m) and V
max was 1.91 μM and 1.13 μmol CO2 mg−1 protein∙min−1, respectively, at a low concentration of Mg2+, and 3.45 μM and 0.32 μmol CO2∙mg−1 protein∙min−1, respectively, at a high concentration of Mg2+. By UV absorption and fluorescence spectroscopy assays, the Mg2+ was determined to be directly bound to Rubisco; the binding site of Mg2+ to Rubisco was 0.275, the binding constants (K
A) of the binding site were 6.33 × 104 and 5.5 × 104 l·mol−1. Based on the analysis of the circular dichroism (CD) spectra, it was concluded that the binding of Mg2+ did not alter the secondary structure of Rubisco, suggesting that the observed enhancement of Rubisco carboxylase activity
was caused by a subtle structural change in the active site through the formation of the complex with Mg2+. 相似文献
19.
Nuphar lutea is an amphibious plant with submerged and aerial foliage, which raises the question how do both leaf types perform photosynthetically
in two different environments. We found that the aerial leaves function like terrestrial sun-leaves in that their photosynthetic
capability was high and saturated under high irradiance (ca. 1,500 μmol photons m−2 s−1). We show that stomatal opening and Rubisco activity in these leaves co-limited photosynthesis at saturating irradiance fluctuating
in a daily rhythm. In the morning, sunlight stimulated stomatal opening, Rubisco synthesis, and the neutralization of a night-accumulated
Rubisco inhibitor. Consequently, the light-saturated quantum efficiency and rate of photosynthesis increased 10-fold by midday.
During the afternoon, gradual closure of the stomata and a decrease in Rubisco content reduced the light-saturated photosynthetic
rate. However, at limited irradiance, stomatal behavior and Rubisco content had only a marginal effect on the photosynthetic
rate, which did not change during the day. In contrast to the aerial leaves, the photosynthesis rate of the submerged leaves,
adapted to a shaded environment, was saturated under lower irradiance. The light-saturated quantum efficiency of these leaves
was much lower and did not change during the day. Due to their low photosynthetic affinity for CO2 (35 μM) and inability to utilize other inorganic carbon species, their photosynthetic rate at air-equilibrated water was
CO2-limited. These results reveal differences in the photosynthetic performance of the two types of Nuphar leaves and unravel how photosynthetic daily rhythm in the aerial leaves is controlled. 相似文献
20.
Travis E. Huxman Erik P. Hamerlynck Dean N. Jordan Katrina J. Salsman Stanley D. Smith 《Oecologia》1998,114(2):202-208
Seeds were collected and compared from parent plants of Bromusrubens L. (Poaceae), an exotic Mojave Desert annual grass, grown in ambient (360 μmol mol−1) and elevated (700 μmol mol−1) CO2 to determine if parental CO2 growth conditions affected seed quality. Performance of seeds developed on the above plants was evaluated to determine the
influence of parental CO2 growth conditions on germination, growth rate, and leaf production. Seeds of B. rubens developed on parents grown in elevated CO2 had a larger pericarp surface area, higher C:N ratio, and less total mass than ambient-developed seeds. Parental CO2 environment did not have an effect on germination percentage or mean germination time, as determined by radicle emergence.
Seedlings from elevated-CO2-developed seeds had a reduced relative growth rate and achieved smaller final mass over the same growth period. Elevated-CO2-developed seeds had smaller seed reserves than ambient seeds, as determined by growing seedlings in sterile media and monitoring
senescence. It appears that increased seed C:N ratios associated with plants grown under elevated CO2 may have a major effect on seed quality (morphology, nutrition) and seedling performance (e.g., growth rate and leaf production).
Since the invasive success of B. rubens is primarily due to its ability to rapidly germinate, increase leaf area and maintain a relatively high growth rate compared
to native annuals and perennial grasses, reductions in seed quality and seedling performance in elevated CO2 may have significant impacts on future community composition in the Mojave Desert.
Received: 11 April 1997 / Accepted: 20 November 1997 相似文献