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1.
The photosynthetic characteristics of differently shaped leaves in Populus euphratica Olivier 总被引:4,自引:0,他引:4
There is a distinct leaf shape polymorphism within a single plant of P. euphratica Olivier. The anatomical structure, carbon isotope discrimination (Δ13C), and stomatal and photosynthetic behaviour were investigated in broad-ovate (BOL) and lanceolate (LL) leaves, located at
the top and bottom in crown, respectively, of a mature Euphrates poplar growing in its native habitat. Both types of leaves
had a non-Kranz anatomy and low Δ13C values. However, Δ13C of a LL was in average 3.2‰ larger than that of a BOL. In comparison with the LL, the BOL had a smaller stomatal conductance,
causing subsequent decreases in transpiration rate and ratio of CO2 concentrations in intercellular spaces to air. Carbon assimilation rate and water use efficiency were higher in the BOLs
than in the LLs. The BOL exhibited C4-like enzymological features, the activity of glycollate oxidase, and the ratio of activities of ribulose-1,5-bisphosphate
carboxylase (RuBPC) to phosphoenolpyruvate carboxylase (PEPC) was lower in BOL than in LL throughout the whole growing season.
The lowered ratio of RuBPC/PEPC in BOL was mainly associated with a marked decline in the activity of RuBPC, and only a slight
increase in the activity of PEPC. These differences might contribute to microclimate adaptation in both types of leaves.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Photosynthetic14CO2 assimilation, ribulose 1, 5-bisphosphate carboxylase (RuBPC), phosphoenol pyruvate carboxylase (PEPC) and dry matter (DM) production were examined in wheat under varying levels and forms of nitrogen.14CO2 assimilation increased gradually after germination reaching a peak value at anthesis, followed by a sharp decline. A similar pattern was observed for both the carboxylases, RuBPC and PEPC activities. Increase in nitrogen levels, in general, brought about a significant increase over the control (zero-nitrogen) in14CO2 assimilation, RuBPC, PEPC activities and DM production. There were no significant differences in RuBPC activity and14CO2 assimilation with respect to the forms of nitrogen. Significantly higher PEPC activity and DM was observed in plants supplied with nitrate-nitrogen (NO3-N), as compared to those supplied with ammonium-nitrogen (NH4-N). The significance of PEPC activity in C3 photosynthesis is discussed in relation to DM distribution. 相似文献
3.
In two winter wheat (Triticum aestivum L.) cultivars differing in their response to high temperature, JD8 (tolerant) and J411 (sensitive) we studied the effect of heat stress on the activities of phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase (RuBPC) in green organs during grain-filling. There were significantly higher PEPC activities and lower RuBPC activities in each of the non-leaf organs (awn, glume, lemma, peduncle, and sheath) than in the flag leaf blade. Under heat stress for 12 d, the activity of RuBPC quickly declined and the activity of PEPC first increased and later declined in all organs, resulting in a great increase of the PEPC/RuBPC ratios in the organs, particularly in non-leaf organs which had a higher PEPC/RuBPC than the flag leaf blade in all times. The PEPC activity and PEPC/RuBPC ratio in every organ of JD8 were higher than those in the same organ of J411. Thus the differences in PEPC activities and PEPC/RuBPC may be associated with the differences in photosynthetic heat tolerance among the organs of the same plant or between the two cultivars. 相似文献
4.
The activities of ribulose bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC), as indicators of autotrophic and nonautotrophic CO2 fixation, were measured in excised cotyledons of Pinus radiata D. Don cultured for 21 days under shoot-forming (SF) and nonshoot-forming (NSF) conditions. The activity of RuBPC was found to increase in both SF and NSF cultures during the initial 5 days of culture. However, it leveled off from day 5 to day 10 and subsequently began to decrease until the end of the culture period under the SF conditions. In contrast, in the NSF cultures, RuBPC activity increased until day 15, when it was twofold higher than the maximum activity found in the SF cultures. An increase in PEPC activity of about 2.5 times the level of activity in freshly excised cotyledons was observed during the initial 5 days of culture under the SF conditions. PEPC activity began to decline after day 5 until it reached the level of activity seen in NSF cotyledons by day 15. In contrast, the activity of PEPC did not show any significant increase during the initial 10 days of culture under the NSF conditions. The Km (phosphoenolpyruvate) of PEPC from SF cotyledons was about 35% higher than that of NSF cotyledons. Cotyledons from two culture periods (days 5 and 15) were incubated for 15 seconds with NaH14CO3. The label in the malate and asparatate fractions as a percentage of total 14C incorporation was 3 times higher in the SF cotyledons than in the NSF cotyledons. A higher incorporation of 14C into products of photosynthesis under the NSF conditions was also observed. 相似文献
5.
mRNA expression patterns of genes for metabolic key enzymes sucrose phosphate synthase (SPS), phosphoenolpyruvate carboxylase (PEPC), pyruvate kinase, ribulose 1,5-bisphosphate carboxylase/oxygenase, glutamine synthetase 1, and
glutamine synthetase 2 were investigated in leaves of rice plants grown at two nitrogen (N) supplies (N0.5, N3.0). The relative gene expression patterns were similar in all leaves except for 9th leaf, in which mRNA levels were generally depressed. Though increased N supply prolonged the expression period of each mRNA,
it did not affect the relative expression intensity of any mRNA in a given leaf. SPS Vmax, SPS limiting and PEPC activities, and carbon flow were examined. The ratio between PEPC activity and SPS Vmax was higher in leaves developed at the vegetative growth stage (vegetative leaves: 5th and 7th leaves) than in leaves developed after the ear primordia formation stage (reproductive leaves: 9th and flag leaves). PEPC activity and SPS Vmax decreased with declining leaf N content. After using 14CO2 the 14C photosynthate distribution in the amino acid fraction was higher in vegetative than in reproductive leaves when compared
for the same leaf N status. Thus, at high PEPC/SPS activities ratio, more 14C photosynthate was distributed to the amino acid pool, whereas at higher SPS activity more 14C was channelled into the saccharide fraction. Thus, leaf ontogeny was an important factor controlling photosynthate distribution
to the N- or C-pool, respectively, regardless of the leaf N status. 相似文献
6.
Maize plants (Zea mays L.) were subjected to soil flooding for 72, 96, and 120 h. A noticeable decrease in the rate of net photosynthesis (PN) and the activity of ribulose-1,5-bisphosphate carboxylase (RuBPC, EC 4.1.1.39) were observed. The values of intercellular
CO2 concentrations (ci) increased in all flooded plants without significant changes in stomatal conductance (gs). The activity of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) increased twofold 120 h after soil flooding. Flooding
of maize plants led to a decrease in chlorophyll and protein levels and to slight increase of proline content. Flooded plants
exhibited a large accumulation of leaf acidity. An increase in the values of some important parameters associated with oxidative
stress, namely peroxides production, lipid peroxidation, and electrolyte leakage, confirmed the suggestion that root oxygen
deficiency caused photooxidative damage in maize leaves. 相似文献
7.
When frozen leaves of 24-day-old maize (Zea mays L.) plant werethawed on moist filter paper at 26°C (freeze-thaw treatment)several enzymes, including phosphoenolpyruvate carboxylase (PEPC)and ribulose-1,5-bisphosphate carboxylase (RuBPC), were rapidlyinactivated and degraded. The kinetics of the inactivation anddegradation were pseudo first-order, and the halftimes for inactivationof PEPC and RuBPC were 3.2 and 2.4 min, respectively. The effectof the freeze-thaw treatment on the inactivation and degradationdiffered among various enzymes: the residual activities of RuBPC,PEPC, hydroxypyruvate reductase, Cyt c oxidase, NADP-malic enzymeand a-mannosidase 10 min after the start of the thawing treatmentwere 7, 16, 54, 64, 97 and 98% of the initial respective levels.Thirty min after the starting of thawing treatment, the amountsof total soluble protein, the large subunit of RuBPC, the smallsubunit of RuBPC, the PEPC subunit and the NADP-malic enzymesubunit had fallen to 61, 2, 16, 8, and 66% of the initial respectiveamounts. The effect of freeze-thaw treatment on PEPC was greater in oldleaves than in young leaves. There was a steady increase ofthe rate of degradation of PEPC by freeze-thaw treatment asplants aged from 6 to 24 days. These results are discussed inthe context of protein degradation in plant cells. (Received August 9, 1993; Accepted January 10, 1994) 相似文献
8.
Activity regulation and physiological impacts of maize C4-specific phosphoenolpyruvate carboxylase overproduced in transgenic rice plants 总被引:6,自引:0,他引:6
Fukayama H Hatch MD Tamai T Tsuchida H Sudoh S Furbank RT Miyao M 《Photosynthesis research》2003,77(2-3):227-239
Phosphoenolpyruvate carboxylase (PEPC) was overproduced in the leaves of rice plants by introducing the intact maize C4-specific PEPC gene. Maize PEPC in transgenic rice leaves underwent activity regulation through protein phosphorylation in
a manner similar to endogenous rice PEPC but contrary to that occurring in maize leaves, being downregulated in the light
and upregulated in the dark. Compared with untransformed rice, the level of the substrate for PEPC (phosphoenolpyruvate) was slightly lower and the product (oxaloacetate) was slightly higher in transgenic rice, suggesting that maize
PEPC was functioning even though it remained dephosphorylated and less active in the light. 14CO2 labeling experiments indicated that maize PEPC did not contribute significantly to the photosynthetic CO2 fixation of transgenic rice plants. Rather, it slightly lowered the CO2 assimilation rate. This effect was ascribable to the stimulation of respiration in the light, which was more marked at lower
O2 concentrations. It was concluded that overproduction of PEPC does not directly affect photosynthesis significantly but it
suppresses photosynthesis indirectly by stimulating respiration in the light. We also found that while the steady-state stomatal
aperture remained unaffected over a wide range of humidity, the stomatal opening under non-steady-state conditions was destabilized
in transgenic rice.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Net photosynthetic rate (P
N) in the mother leaves was higher in the drought tolerant (DT) clones of tea (Camellia sinensis) while liberation of the fixed 14C in light from the mother leaves was higher in the drought susceptible (DS) clones. The DT clones translocated more photosynthates to the crop shoots (three leaves and a bud) from the mother leaf than the DS clones. Concentrations of RuBP carboxylase (RuBPC) or oxygenase (RuBPO) had no relationship with the drought tolerant nature of tea clones but their ratio correlated with the same. DT tea clones had higher catalase activity that could scavenge the hydrogen peroxide formed in the photorespiratory pathway and thereby reduced photorespiration rate (P
R). The ratio of RuBPC/RuBPO had a positive correlation with P
N and catalase activity. Negative correlation between RuBPC/RuBPO and P
R and between catalase activity and RuBPO activity was established. 相似文献
10.
The physiological and photosynthetic responses of Littorella uniflora (L.) Ascherson, an amphibious macrophyte of isoetid life form, to rapid and prolonged emersion onto dry land, was studied at a reservoir. Water relations were little affected in the short term, but declining water potential and turgor pressure indicated water stress after flowering. High leaf lacunal CO2 concentrations suggested continued CO2 uptake from sediments. In contrast, a switch from Crassulacean acid metabolism (CAM) to C3 photosynthesis was indicated by much lower levels of ΔH+ (down minus dusk titratable acidity) and phosphoenolpyruvate carboxylase (PEPC) activity in new terrestrial leaves, 7–8‐fold higher activity of ribulose bisphosphate carboxylase oxygenase (Rubisco), and increased chlorophyll and soluble protein contents. Accumulated nitrate and amino acid pools were depleted, whereas storage of carbohydrates as soluble sugars, fructan and starch increased. Plant carbon and nitrogen isotope ratios (δ13C and δ15N) declined, perhaps reflecting changes in C fixation processes, N metabolism, and source C and N. In leaves of plants grown half‐emersed for an extended period, contrasting activities of PEPC and Rubisco were found in submersed and emersed portions. Overall, L. uniflora showed considerable phenotypic plasticity, yet seemed to remain poised for re‐submersion; these characteristics could be adaptive in the unpredictable water margin habitat. 相似文献
11.
12.
Variation in amounts of pyruvate, orthophosphate dikinase, and some other enzymes of the c(4) pathway in some wheat species 下载免费PDF全文
First leaves and flag leaves of the wheat species Triticum aestivum cv Anza (6×), T. boeoticum Boiss (2×) L. were examined for content of pyruvate, orthophosphate dikinase (PPDK), phosphoenolpyruvate carboxylase (PEPC), and ribulose 1,5-bisphosphate carboxylase (RuBPC) by protein blot analyses using antibodies to maize leaf enzymes and by activity assays. In agreement with previous reports, the amount of RuBPC per mesophyll cell was about 3 times more in the hexaploid species, T. aestivum, than in the diploid species, T. boeoticum, both in first leaves and in flag leaves. In contrast, the level of PPDK polypeptide was nearly 3-fold higher per unit leaf area in the first leaf and 63% higher in the flag leaf of this diploid species compared to this hexaploid species. There was no significant difference in the levels of polypeptide and enzyme activity of PEPC between diploid and hexaploid wheat. Despite this significantly greater level of PPDK in the diploid species, the actual amount of PPDK could still supply only a limited amount of the enzyme activity necessary to provide phosphoenolpyruvate (PEP) for any putative intracellular C4 carbon shuttle providing carbon to RuBPC. Thus, this difference in enzyme amount could not by itself account for the reported high rates of net photosynthesis at high light intensity in T. boeoticum. Together with reported anatomical differences between the diploid and hexaploid species, however, this biochemical difference may be of physiological importance. 相似文献
13.
Losanka P. Popova Zhivka G. Stoinova Liliana T. Maslenkova 《Journal of Plant Growth Regulation》1995,14(4):211-218
In Hordeum vulgare L. plants, NaCl stress imposed through the root medium for a period of 8 days decreased the rate of CO2 assimilation, the chlorophyll and protein leaf content, and the activity of ribulose-1,5-bisphosphate carboxylase. The activity of phosphoenolpyruvate carboxylase was twofold over the control. Pretreatment with abscisic acid (ABA) for 3 days before salinization diminished the inhibitory effect of NaCl on the rate of CO2 fixation. The leaf Na+ and Cl– content decreased in ABA-pretreated plants. Both ABA and NaCl treatments led to an increase in the endogenous level of ABA in the plant leaves. Patterns of total proteins extracted from the leaves of control or ABA- and salt-treated plants were compared. Both ABA and NaCl induced marked quantitative and qualitative changes in the polypeptide profiles concerning mainly the proteins with approximately equal mobility. The results are discussed in terms of a possible role of ABA in increasing the salt tolerance when ABA is applied to the plants for a short period before exposure to salinity stress, thus improving the invulnerability to unfavorable conditions.Abbreviations RuBPC
ribulose-1,5-bisphosphate carboxylase
- PSII
photosystem II
- ABA
abscisic acid
- PEPC
phosphoenolpyruvate carboxylase
- DTTr
dithiothreitol
- BSA
bovine serum albumin
- ELISA
enzyme-linked immunosorbent assay
- SDS
sodium dodecyl sulfate
- PAGEr
polyacrylamide gel electrophoresis 相似文献
14.
Isotype analyses were performed on biochemical fractions isolated from leaves of Kalanchoe blossfeldiana Tom Thumb. during aging under long days or short days. Irrespective of the age or photoperiodic conditions, the intermediates of the starch-malate sequence (starch, phosphorylated compounds and organic acids) have a level of 13C higher than that of soluble sugars, cellulose and hemicellulose. In short days, the activity of the crassulacean acid metabolism pathway is predominant as compared to that of C3 pathway: leaves accumulate organic acids, rich in 13C. In long days, the activity of the crassulacean acid metabolism pathway increases as the leaves age, remaining, however, relatively low as compared to that of C3 pathway: leaves accumulate soluble sugars, poor in 13C. After photoperiodic change (long daysshort days), isotopic modifications of starch and organic acids suggest evidence for a lag phase in the establishment of the crassulacean acid metabolism pathway specific to short days. The relative proportions of carbon from a C3-origin (RuBPC acitivity as strong discriminating step, isotope discrimination in vivo=20) or C4-origin (PEPC activity as weak discriminating step, isotope discrimination in vivo=4) present in the biochemical fractions were calculated from their 13C values. Under long days, 30 to 70% versus 80 to 100% under short days, of the carbon of the intermediates linked to the starch-malate sequence, or CAM pathway (starch, phosphorylated compounds and organic acids), have a C4-origin. Products connected to the C3 pathway (free sugars, cellulose, hemicellulose) have 0 to 50% of their carbon, arising from reuptake of the C4 from malate, under long days versus 30 to 70% under short days.Abbreviations CAM
crassulacean acid metabolism
- CAM pathway
pathway with malate accumulation by -carboxylation of PEP, arising from glycolysis of starch (starch-malate sequence)
- C3-metabolism
metabolism with primary carbon fixed by the Calvin and Benson pathway (C3-origin)
- C4-metabolism
metabolism with primary carbon fixed by the Hatch and Slack pathway (C4-origin)
- C3-pathway
pathway with RuBPC activity and the Calvin and Benson pathway, irrespective of the CO2-source, atmospheric or reuptake of the C4 from malate
- 13C()=(Rsample-RPDR)103/RPDB where PDB
Pee Dee belemnite (belemnite from the Pee Dee formation, South Carolina) and R=13C/12C
- D
isotope discrimination
- PEP
phosphoenolpyruvate
- PEPC (EC 4.1.1.31)
PEP carboxylase
- PGA
phosphoglyceric acid
- Py.di-PK (EC 2.7.9.1)
pyruvate, Pi-dikinase
- RuBP
ribulose bisphosphate
- RuBPC (EC 4.1.1.39)
RuBP carboxylase
- SD
short days
- LD
long days 相似文献
15.
Wheat (T. aestivum) cvs. Kalyansona and Kundan grown under atmospheric (CA) and elevated CO2 concentrations (650±50 cm3 m-3 - CE) in open top chambers were examined for net photosynthetic rate (PN), stomatal limitation (l s) of P N, ribulose-1,5-bisphosphate carboxylase (RuBPC) activity, and saccharide content of the leaves. The P N values of both CA- and CE-grown plants compared at the same CO2 concentration showed a down regulation under CE at the post-anthesis stage. The negative acclimation of P N appeared to be due to both stomatal and mesophyll components, and the RuBPC activity got also adjusted. There was a decrease in activation state of RuBPC under CE. In connection with this, an increased accumulation of saccharides in wheat leaf under CE was observed. Kalyansona, owing to its larger sink potential in terms of the number of grains, showed a greater enhancement under CE in both post-ear emergence dry matter production and grain yield. Under CE, this cultivar also showed a lower down regulation of P N than Kundan. 相似文献
16.
17.
Photosynthetic acclimation to elevated CO2 in wheat cultivars 总被引:2,自引:0,他引:2
Wheat (T. aestivum) cvs. Kalyansona and Kundan grown under atmospheric (CA) and elevated CO2 concentrations (650±50 cm3 m-3 - CE) in open top chambers were examined for net photosynthetic rate (PN), stomatal limitation (l
s) of P
N, ribulose-1,5-bisphosphate carboxylase (RuBPC) activity, and saccharide content of the leaves. The P
N values of both CA- and CE-grown plants compared at the same CO2 concentration showed a down regulation under CE at the post-anthesis stage. The negative acclimation of P
N appeared to be due to both stomatal and mesophyll components, and the RuBPC activity got also adjusted. There was a decrease
in activation state of RuBPC under CE. In connection with this, an increased accumulation of saccharides in wheat leaf under
CE was observed. Kalyansona, owing to its larger sink potential in terms of the number of grains, showed a greater enhancement
under CE in both post-ear emergence dry matter production and grain yield. Under CE, this cultivar also showed a lower down
regulation of P
N than Kundan.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
J. Kvto 《Biologia Plantarum》2001,44(3):447-450
Three clones of tobacco transformed with the T-DNA of Agrobacterium rhizogenes Ri plasmid A4b cultivated in vitro on a solid agar medium neither showed pronounced morphological diversity nor significantly differed in chlorophyll (Chl) contents from control plants. However, the transformation caused a 27 to 83 % decay in leaf oxygen evolution and in both ribulose-1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC) activities. Therefore, the transformation brought about a reduction of active PEPC as well as activable RuBPC amounts in plant tissues. Individual clones did not mutually differ. In tobacco transformed with A. rhizogenes strain TR101 and grown in soil only the mean leaf area tended to reduce. Chl contents, Chl a/b ratio, oxygen evolution, and activities of both RuBPC and PEPC were insignificantly affected by the transformation. 相似文献
19.
In woody species, the photosynthesis of stems, especially young branches, occurs by refixing part of the internal respiratory
CO2. The present study aims to improve the physiological characterization of stem photosynthesis by examining enzymatic characteristics.
During an entire growing season, three enzymatic activities that are linked to C3 and C4 metabolism were investigated in relation to the CO2 efflux and chlorophyll content of current year stems of European beech and were compared to the corresponding characteristics
of leaves. High activities of phosphoenolpyruvate carboxylase (PEPC) and NADP malic enzyme were detected in stems (up to 13 times and 30 times higher in stems than
in leaves, respectively), whereas Rubisco activity remained low in comparison with leaves. Stem maximal Rubisco and PEPC activities
occurred at the beginning of the season when the total chlorophyll content and the CO2 assimilation rate were also maximal. Stems were characterized by a PEPC:Rubisco ratio that was equal to 2.5 [an intermediate
value between that of C3-plants (about 0.1) and that of C4-plants (about 10)], whereas it was equal to 0.1 in leaves. Eight other tree species were also measured and the PEPC:Rubisco
ratio was, on average, equal to 3.6. The potential role of PEPC in stem carbon assimilation is discussed in relation to its
known involvement in the anaplerotic function of C3 plants and in the carbon metabolism of the C4 pathway. 相似文献
20.
C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO2 concentration around ribulose bisphosphate carboxylase oxygenase (Rubisco) in the bundle sheath (BS). Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO2 retrodiffusing from the BS relative to C4 carboxylation processes. Maize plants were grown under high and low light regimes (respectively HL, 600 versus LL, 100 μE m?2 s?1). Short‐term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry. Direct measurement of respiration in the light, and ATP production rate (JATP), allowed us use a novel approach to derive Φ, compared with the conventional fitting of measured and predicted Δ. HL grown plants responded to decreasing light intensities with the well‐documented increase in Φ. Conversely, LL plants showed a constant Φ, which has not been observed previously. We explain the pattern by two contrasting acclimation strategies: HL plants maintained a high CCM activity at LL, resulting in high CO2 overcycling and increased Φ; LL plants acclimated by down‐regulating the CCM, effectively optimizing scarce ATP supply. This surprising plasticity may limit the impact of Φ‐dependent carbon losses in leaves becoming shaded within developing canopies. 相似文献