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1.
The n‐alkane composition and the nonacosan‐10‐ol content in the needle cuticular waxes of Serbian spruce ( Picea omorika), Bosnian pine ( Pinus heldreichii), and Macedonian pine ( Pinus peuce) were compared. The amount of nonacosan‐10‐ol in the needle waxes of P. omorika was higher than those in P. heldreichii and P. peuce. The range of n‐alkanes was also wider in P. omorika (C 18–C 35) than in P. heldreichii and P. peuce (C 18–C 33). The dominant n‐alkanes were C 29 in the needle waxes of P. omorika, C 23, C 27, and C 25 in those of P. heldreichii, and C 29, C 25, C 27, and C 23 in those of P. peuce. The waxes of P. omorika contained higher amounts of n‐alkanes C 29, C 31, and C 33, while those of P. heldreichii and P. peuce had higher contents of n‐alkanes C 21, C 22, C 23, C 24, and C 26. The principal component analysis of the contents of nine n‐alkanes showed a clear separation of the Serbian spruce populations from those of the two investigated pine species, which partially overlapped. The separation of the species was due to high contents of the n‐alkanes C 29 and C 31 ( P. omorika), C 19, C 20, C 21, C 22, C 23, and C 24 ( P. heldreichii), and C 28 ( P. peuce). Cluster analysis also showed a clear separation between the P. omorika populations on one side and the P. heldreichii and P. peuce populations on the other side. The n‐alkane and terpene compositions are discussed in the light of their usefulness in chemotaxonomy as well as with regard to the biogeography and phylogeny of these rare and endemic conifers. 相似文献
2.
The parameters estimated from traditional A/ C
i curve analysis are dependent upon some underlying assumptions that substomatal CO 2 concentration ( C
i) equals the chloroplast CO 2 concentration ( C
c) and the C
i value at which the A/ C
i curve switches between Rubisco- and electron transport-limited portions of the curve ( C
i-t) is set to a constant. However, the assumptions reduced the accuracy of parameter estimation significantly without taking
the influence of C
i-t value and mesophyll conductance ( g
m) on parameters into account. Based on the analysis of Larix gmelinii’s A/ C
i curves, it showed the C
i-t value varied significantly, ranging from 24 Pa to 72 Pa and averaging 38 Pa. t-test demonstrated there were significant differences in parameters respectively estimated from A/ C
i and A/ C
c curve analysis ( p<0.01). Compared with the maximum ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate (V cmax), the maximum electron transport rate (J max) and J max/V cmax estimated from A/ C
c curve analysis which considers the effects of g
m limit and simultaneously fits parameters with the whole A/ C
c curve, mean V cmax estimated from A/ C
i curve analysis (V cmax- C
i) was underestimated by 37.49%; mean Jmax estimated from A/ C
i curve analysis (J max- C
i) was overestimated by 17.8% and (J max- C
i)/(V cmax- C
i) was overestimated by 24.2%. However, there was a significant linear relationship between V cmax estimated from A/ C
i curve analysis and V cmax estimated from A/ C
c curve analysis, so was it J max ( p<0.05). 相似文献
3.
Summary Clear mutants which differ from regular C
I
, C
II
, C IIIand y mutants have been isolated from phage 434 hy. These mutants resemble C
I
mutants in plaque and spot phenotype but efficiently complement C
I
mutants for lysogenization. Like C
II
mutants, they do not complement authentic C
II
mutants for lysogenization but in contrast to C
II
mutants they also fail to complement C
III
mutants. They map between the lambda-434 non-homology region and Co
1 ( aC
II
mutant). On account of this map position adjacent to C
II
the mutants of the new type are called C
IIa
. They arise from phage 434 hy with a frequency comparable to that of C
I
and C
II
mutants. Such mutants are also obtained from phage lambda but apparently not from phage b 5.
C
IIa
mutants would not fit into a picture of three independently acting cistrons C
I
, C II, and C
III
. The hypothesis is presented that C
IIa
and C
II
mutants are in the same structural gene. Two possibilities are discussed that would account for the complementation patterns: 1. C
IIa
mutants may block the expression of gene C
III
in cis position; or 2. the products of genes C
II
and C
III
function through an oligomeric complex they form. 相似文献
4.
This is the first report on the composition and variability of the needle‐wax n‐alkanes in natural populations of Pinus nigra in Serbia. Samples of 195 trees from seven populations belonging to several infraspecific taxa (ssp. nigra, var. gocensis, ssp. pallasiana, and var. banatica) were analyzed. In general, the size of the n‐alkanes ranged from C 16 to C 33, with the exception of ssp. nigra, for which it ranged from C 18 to C 33. The most abundant were C 23‐, C 25‐, C 27‐, and C 29‐alkanes. The needle waxes of Populations I– III and V were characterized by a higher content of C 23‐, C 25‐, and C 27‐alkanes and a lower content of C 24‐, C 26‐, C 28‐, and C 30‐alkanes, compared to the other populations, and the trees of these populations could be assigned to ssp. nigra. The samples of Population VI were characterized by higher amounts of C 22‐, C 24‐, C 30‐, and C 32‐alkanes and lower amounts of C 25‐ and C 27‐alkanes, and the trees could be considered as ssp. pallasiana. The samples of Population VII, consisting of trees belonging to var. banatica, were richer in C 29‐, C 31‐, and C 33‐alkanes. The wax compositions of Populations IV and V, both composed of trees previously determined as P. nigra var. gocensis, showed a tendency of splitting. Indeed, the alkane composition of Population IV was closer to that of ssp. pallasiana pines, while that of Population V was more similar to that of ssp. nigra pines. From the results presented here, it is obvious that in the central part of the Balkan Peninsula, significant diversification and differentiation of the populations of black pine exists, and these populations could be defined as different intraspecific taxa. Our results also indicate the validity of n‐alkanes as chemotaxonomic characters within this aggregate. 相似文献
5.
Atmospheric CO 2 (C a) has risen dramatically since preglacial times and is projected to double in the next century. As part of a 4‐year study, we examined leaf gas exchange and photosynthetic acclimation in C 3 and C 4 plants using unique chambers that maintained a continuous C a gradient from 200 to 550 µmol mol ?1 in a natural grassland. Our goals were to characterize linear, nonlinear and threshold responses to increasing C a from past to future C a levels. Photosynthesis ( A), stomatal conductance ( gs), leaf water‐use efficiency ( A/ gs) and leaf N content were measured in three common species: Bothriochloa ischaemum, a C 4 perennial grass, Bromus japonicus, a C 3 annual grass, and Solanum dimidiatum, a C 3 perennial forb. Assimilation responses to internal CO 2 concentrations ( A/C i curves) and photosynthetically active radiation ( A/PAR curves) were also assessed, and acclimation parameters estimated from these data. Photosynthesis increased linearly with C a in all species ( P < 0.05). S. dimidiatum and B. ischaemum had greater carboxylation rates for Rubisco and PEP carboxylase, respectively, at subambient than superambient C a ( P < 0.05). To our knowledge, this is the first published evidence of A up‐regulation at subambient C a in the field. No species showed down‐regulation at superambient C a. Stomatal conductance generally showed curvilinear decreases with C a in the perennial species ( P < 0.05), with steeper declines over subambient C a than superambient, suggesting that plant water relations have already changed significantly with past C a increases. Resource‐use efficiency ( A/ gs and A/leaf N) in all species increased linearly with C a. As both C 3 and C 4 plants had significant responses in A, gs, A/ gs and A/leaf N to C a enrichment, future C a increases in this grassland may not favour C 3 species as much as originally thought. Non‐linear responses and acclimation to low C a should be incorporated into mechanistic models to better predict the effects of past and present rising C a on grassland ecosystems. 相似文献
6.
The carbon dioxide concentrating system in C 4 photosynthesis allows high net photosynthetic rates ( P
N) at low internal carbon dioxide concentrations ( C
i), permitting higher P
N relative to stomatal conductance ( g
s) than in C 3 plants. This relation would be reflected in the ratio of C
i to external ambient ( C
a) carbon dioxide concentration, which is often given as 0.3 or 0.4 for C 4 plants. For a C
a of 360 μmol mol −1 that would mean a C
i about 110–140 μmol mol −1. Our field observations made near midday on three weedy C 4 species, Amaranthus retroflexus, Echinochloa crus-galli, and Setaria faberi, and the C 4 crop Sorghum bicolor indicated mean values of C
i of 183–212 μ mol mol −1 at C
a = 360 μmol mol −1. Measurements in two other C 4 crop species grown with three levels of N fertilizer indicated that while midday values of C
i at high photon flux were higher at limiting N, even at high nitrogen C
i averaged 212 and 196 μmol mol −1 for Amaranthus hypochondriacus and Zea mays, respectively. In these two crops midday C
i decreased with increasing leaf to air water vapor pressure difference. Averaged over all measurement days, the mean C
i across all C 4 species was 198 μmol mol −1, for a C
i/ C
a ratio of 0.55. Prior measurements on four herbaceous C 3 species using the same instrument indicated an average C
i/ C
a ratio of 0.69. Hence midday C
i values in C
4 species under field conditions may often be considerably higher and more similar to those of C 3 species than expected from measurements made on plants in controlled environments. Reducing g
s in C 4 crops at low water vapor pressure differences could potentially improve their water use efficiency without decreasing P
N. 相似文献
7.
During the past 25 Myr, partial pressures of atmospheric CO 2 ( Ca) imposed a greater limitation on C 3 than C 4 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 C 3 and C 4 subspecies of Alloteropsis semialata. Plant size decreased more in the C 3 than C 4 subspecies at low Ca, but nitrogen pool sizes were unchanged, and nitrogen concentrations increased across all plant partitions. The C 3, but not C 4 subspecies, preferentially allocated biomass to leaves and increased specific leaf area at low Ca. In the C 3 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 C 3 subspecies, but these were insufficient to maintain photosynthetic rates. In contrast, the C 4 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 C 4 carbon‐concentrating mechanism therefore offered a significant advantage over the C 3 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 C 4 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 CO 2 and resource limitation benefit C 4 plants over C 3 plants in glacial–interglacial environments, but that this advantage is lessened under anthropogenic conditions. 相似文献
8.
Phospho enolpyruvate carboxylase (PEPC) was purified from leaves of four species of Alternanthera differing in their photosynthetic carbon metabolism: Alternanthera sessilis (C 3), A. pungens (C 4), A. ficoides and A. tenella (C 3-C 4 intermediates or C 3-C 4). The activity and properties of PEPC were examined at limiting (0.05 mM) or saturating (10 mM) bicarbonate concentrations.
The V max as well as K m values (for Mg 2+ or PEP) of PEPC from A. ficoides and A. tenella (C 3-C 4 intermediates) were in between those of C 3 ( A. sessilis) and C 4 species ( A. pungens). Similarly, the sensitivity of PEPC to malate (an inhibitor) or G-6-P (an activator) of A. ficoides and A. tenella (C 3-C 4) was also of intermediate status between those of C 3 and C 4 species of A. sessilis and A. pungens, respectively. In all the four species, the maximal activity (V max), affinity for PEP (K m), and the sensitivity to malate (K I) or G-6-P (K A) of PEPC were higher at 10 mM bicarbonate than at 0.05 mM bicarbonate. Again, the sensitivity to bicarbonate of PEPC from
C 3-C 4 intermediates was in between those of C 3- and C 4-species. Thus the characteristics of PEPC of C 3-C 4 intermediate species of Alternanthera are intermediate between C 3- and C 4-type, in both their kinetic and regulatory properties. Bicarbonate could be an important modulator of PEPC, particularly
in C 4 plants.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
The potential for C 4 photosynthesis was investigated in five C 3-C 4 intermediate species, one C 3 species, and one C 4 species in the genus Flaveria, using 14CO 2 pulse- 12CO 2 chase techniques and quantum-yield measurements. All five intermediate species were capable of incorporating 14CO 2 into the C 4 acids malate and aspartate, following an 8-s pulse. The proportion of 14C label in these C 4 products ranged from 50–55% to 20–26% in the C 3-C 4 intermediates F. floridana Johnston and F. linearis Lag. respectively. All of the intermediate species incorporated as much, or more, 14CO 2 into aspartate as into malate. Generally, about 5–15% of the initial label in these species appeared as other organic acids. There was variation in the capacity for C 4 photosynthesis among the intermediate species based on the apparent rate of conversion of 14C label from the C 4 cycle to the C 3 cycle. In intermediate species such as F. pubescens Rydb., F. ramosissima Klatt., and F. floridana we observed a substantial decrease in label of C 4-cycle products and an increase in percentage label in C 3-cycle products during chase periods with 12CO 2, although the rate of change was slower than in the C 4 species, F. palmeri. In these C 3-C 4 intermediates both sucrose and fumarate were predominant products after a 20-min chase period. In the C 3-C 4 intermediates, F. anomala Robinson and f. linearis we observed no significant decrease in the label of C 4-cycle products during a 3-min chase period and a slow turnover during a 20-min chase, indicating a lower level of functional integration between the C 4 and C 3 cycles in these species, relative to the other intermediates. Although F. cronquistii Powell was previously identified as a C 3 species, 7–18% of the initial label was in malate+aspartate. However, only 40–50% of this label was in the C-4 position, indicating C 4-acid formation as secondary products of photosynthesis in F. cronquistii. In 21% O 2, the absorbed quantum yields for CO 2 uptake (in mol CO 2·[mol quanta] -1) averaged 0.053 in F. cronquistii (C 3), 0.051 in F. trinervia (Spreng.) Mohr (C 4), 0.052 in F. ramosissima (C 3-C 4), 0.051 in F. anomala (C 3-C 4), 0.050 in F. linearis (C 3-C 4), 0.046 in F. floridana (C 3-C 4), and 0.044 in F. pubescens (C 3-C 4). In 2% O 2 an enhancement of the quantum yield was observed in all of the C 3-C 4 intermediate species, ranging from 21% in F. ramosissima to 43% in F. pubescens. In all intermediates the quantum yields in 2% O 2 were intermediate in value to the C 3 and C 4 species, indicating a co-function of the C 3 and C 4 cycles in CO 2 assimilation. The low quantum-yield values for F. pubescens and F. floridana in 21% O 2 presumably reflect an ineffcient transfer of carbon from the C 4 to the C 3 cycle. The response of the quantum yield to four increasing O 2 concentrations (2–35%) showed lower levels of O 2 inhibition in the C 3-C 4 intermediate F. ramosissima, relative to the C 3 species. This indicates that the co-function of the C 3 and C 4 cycles in this intermediate species leads to an increased CO 2 concentration at the site of ribulose-1,5-bisphosphate carboxylase/oxygenase and a concomitant decrease in the competitive inhibition by O 2.Abbreviations PEP
phosphoenolpyruvate
- PGA
3-phosphoglycerate
- RuBP
ribulose-1,5-bisphosphate 相似文献
10.
Diatoms are one of the largest groups of primary producers in the oceans, yet despite their environmental importance little is known about their plastidial lipid biochemistry. It has been previously reported that Skeletonema species contain primarily C 16/C 16 and C 20/C 16 forms of mono‐ and digalactosyldiacylglycerol (MGDG and DGDG, respectively). Likewise, it was also reported that Phaeodactylum tricornutum contains primarily C 16/C 16 and C 20/C 20 forms of MGDG and DGDG. We seek to relate their studies to other diatoms, both in the centrics and pennates, with particular focus on the marennine‐producing pennate diatom, Haslea ostrearia. To this end, the composition and positional distribution of fatty acids of MGDG and DGDG were examined using positive‐ion electrospray ionization/mass spectrometry (ESI/MS). Two centric diatoms, Skeletonema marinoi and Thalassiosira weissflogii, and the pennate diatom, P. tricornutum, contained primarily C 20/C 16 ( sn‐1/ sn‐2) and C 18/C 16 forms of MGDG and DGDG. The other pennate diatoms, H. ostrearia and Navicula perminuta, contained primarily C 18/C 16 or C 18/C 18 forms of MGDG and DGDG, indicating a previously unrecognized fatty acid diversity in diatom MGDG and DGDG. 相似文献
11.
Stomatal function mediates physiological trade‐offs associated with maintaining a favourable H 2O balance in leaf tissues while acquiring CO 2 as a photosynthetic substrate. The C 3 and C 4 species appear to have different patterns of stomatal response to changing light conditions, and variation in this behaviour may have played a role in the functional diversification of the different photosynthetic pathways. In the current study, we used gain analysis theory to characterize the stomatal conductance response to light intensity in nine different C 3, C 4 and C 3‐C 4 intermediate species Flaveria species. The response of stomatal conductance ( gs) to a change in light intensity represents both a direct (related to a change in incident light intensity, I) and indirect (related to a change in intercellular CO 2 concentration, Ci) response. The slope of the line relating the change in gs to Ci was steeper in C 4 species, compared with C 3 species, with C 3‐C 4 species having an intermediate response. This response reflects the greater relative contribution of the indirect versus direct component of the gs versus I response in the C 4 species. The C 3‐C 4 species, Flaveria floridana, exhibited a C 4‐like response whereas the C 3‐C 4 species, Flaveria sonorensis and Flaveria chloraefolia, exhibited C 3‐like responses, similar to their hypothesized position along the evolutionary trajectory of the development of C 4 photosynthesis. There was a positive correlation between the relative contribution of the indirect component of the gs versus I response and water use efficiency when evaluated across all species. Assuming that the C 3‐C 4 intermediate species reflect an evolutionary progression from fully expressed C 3 ancestors, the results of the current study demonstrate an increase in the contribution of the indirect component of the gs versus I response as taxa evolve toward the C 4 extreme. The greater relative contribution of the indirect component of the stomatal response occurs through both increases in the indirect stomatal components and through decreases in the direct. Increases in the magnitude of the indirect component may be related to the maintenance of higher water use efficiencies in the intermediate evolutionary stages, before the appearance of fully integrated C 4 photosynthesis. 相似文献
12.
Evidence is presented contrary to the suggestion that C 4 plants grow larger at elevated CO 2 because the C 4 pathway of young C 4 leaves has C 3-like characteristics, making their photosynthesis O 2 sensitive and responsive to high CO 2. We combined PAM fluorescence with gas exchange measurements to examine the O 2 dependence of photosynthesis in young and mature leaves of Panicum antidotale (C 4, NADP-ME) and P. coloratum (C 4, NAD-ME), at an intercellular CO 2 concentration of 5 Pa. P. laxum (C 3) was used for comparison. The young C 4 leaves had CO 2 and light response curves typical of C 4 photosynthesis. When the O 2 concentration was gradually increased between 2 and 40%, CO 2 assimilation rates ( A) of both mature and young C 4 leaves were little affected, while the ratio of the quantum yield of photosystem II to that of CO 2 assimilation ( ΦPSII/ ΦCO2) increased more in young (up to 31%) than mature (up to 10%) C 4 leaves. A of C 3 leaves decreased by 1·3 and ΦPSII/ ΦCO2 increased by 9-fold, over the same range of O 2 concentrations. Larger increases in electron transport requirements in young, relative to mature, C 4 leaves at low CO 2 are indicative of greater O 2 sensitivity of photorespiration. Photosynthesis modelling showed that young C 4 leaves have lower bundle sheath CO 2 concentration, brought about by higher bundle sheath conductance relative to the activity of the C 4 and C 3 cycles and/or lower ratio of activities of the C 4 to C 3 cycles. 相似文献
13.
The n‐alkane composition in the leaf cuticular waxes of natural populations of Bosnian pine ( Pinus heldreichii), Austrian pine ( P. nigra), and Macedonian pine ( P. peuce) was compared for the first time. The range of n‐alkanes was wider in P. nigra (C 16 – C 33) than in P. heldreichii and P. peuce (C 18 – C 33). Species also diverged in abundance and range of dominant n‐alkanes ( P. heldreichii: C 23, C 27, and C 25; P. nigra: C 25, C 27, C 29, and C 23; P. peuce: C 29, C 25, C 27, and C 23). Multivariate statistical analyses (PCA, DA, and CA) generally pointed out separation of populations of P. nigra from populations of P. heldreichii and P. peuce (which were, to a greater or lesser extent, separated too). However, position of these species on the basis of n‐alkane composition was in accordance neither with infrageneric classification nor with recent molecular and terpene investigations. 相似文献
14.
The amphibious leafless sedge, Eleocharis baldwinii, expresses C 4 characteristics in the terrestrial form and intermediate characteristics between C 3 and C 4 photosynthesis in the submerged form. This study examined the immunocytochemical localization of C 3 and C 4 enzymes in culms of the two forms to elucidate the regulatory mechanism of photosynthetic metabolism and compared the activities and amounts of C 3 and C 4 enzymes with those in other Eleocharis species, E. vivipara and E. retroflexa, which show C 4 characteristics on land but C 3 and C 4 characteristics under water. The terrestrial form of E. baldwinii exhibited a C 4‐like pattern of enzyme localization. The submerged form exhibited a modified anatomy with well‐developed mesophyll cells and small Kranz cells. The C 4 enzyme levels declined conspicuously in outer mesophyll cells adjacent to the epidermis, whereas Rubisco levels increased throughout the mesophyll in the submerged form. These results suggest that intermediate photosynthesis between C 3 and C 4 photosynthesis in the submerged form results from the predominant operation of the C 3 pathway in the outer mesophyll cells and the C 4 pathway in both the inner mesophyll and Kranz cells. Differences in the degree of C 4 expression in terrestrial forms of Eleocharis species may cause the differences in the expression of photosynthetic modes under water. 相似文献
15.
Soil organic carbon (SOC) pools are important in maintaining soil productivity and influencing the CO 2 loading into the atmosphere. An attempt is made here to investigate into the dynamics of pools of SOC viz., total organic
carbon ( C
tot), oxidisable organic carbon ( C
oc) and its four different fractions such as very labile ( C
frac 1), labile ( C
frac 2), less labile ( C
frac 3) and non-labile ( C
frac 4), microbial biomass carbon ( C
mic), mineralizable carbon ( C
min), and particulate organic carbon ( C
p) in relation to crop productivity using a 34 year old rice ( Oryza sativa L)–wheat ( Triticum aestivum L)–jute ( Corchorus olitorius L) cropping system with different management strategies (no fertilization, only N, NP, NPK and NPK + FYM) in the hot humid,
subtropics of India. A fallow treatment was also included to compare the impact of cultivation vis-à-vis no cultivation. Cultivation
over the years caused a net decrease, while balanced fertilization with NPK maintained the SOC pools at par with the fallow.
Only 22% of the C applied as FYM was stabilized into SOC, while the rest got lost. Of the analysed pools, C
frac 1, C
mic, C
p and C
min were influenced most by the treatments imposed. Most of the labile pools were significantly correlated with each other and
with the yield and sustainable yield index (SYI) of the studied system. Of them, C
frac1, C
min, C
mic and C
p explained higher per cent variability in the SYI and yield of the crops. Results suggest that because of low cost and ease
of estimation and also for upkeeping environmental conditions, C
frac1 may be used as a good indicator for assessment of soil as to its crop productivity.
Responsible Editor: Hans Lambers. 相似文献
16.
Phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.3) is a key enzyme of C 4 photosynthesis. It has evolved from ancestral non-photosynthetic (C 3) isoforms and thereby changed its kinetic and regulatory properties. We are interested in understanding the molecular changes,
as the C 4 PEPCases were adapted to their new function in C 4 photosynthesis and have therefore analysed the PEPCase genes of various Alternanthera species. We isolated PEPCase cDNAs from the C 4 plant Alternanthera pungens H.B.K., the C 3/C 4 intermediate plant A. tenella Colla, and the C 3 plant A. sessilis (L.) R.Br. and investigated the kinetic properties of the corresponding recombinant PEPCase proteins and their phylogenetic
relationships. The three PEPCases are most likely derived from orthologous gene classes named ppcA. The affinity constant for the substrate phosphoenolpyruvate ( K
0.5 PEP) and the degree of activation by glucose-6-phosphate classified the enzyme from A. pungens (C 4) as a C 4 PEPCase isoform. In contrast, both the PEPCases from A. sessilis (C 3) and A. tenella (C 3/C 4) were found to be typical C 3 PEPCase isozymes. The C 4 characteristics of the PEPCase of A. pungens were accompanied by the presence of the C 4-invariant serine residue at position 775 reinforcing that a serine at this position is essential for being a C 4 PEPCase (Svensson et al. 2003). Genomic Southern blot experiments and sequence analysis of the 3′ untranslated regions of these genes indicated the existence
of PEPCase multigene family in all three plants which can be grouped into three classes named ppcA, ppcB and ppcC. 相似文献
17.
n-Alkanes pattern in response to NaCl stress has been studied in the cyanobacterium Anabaena cylindrica. Saturated hydrocarbons were separated and identified by gas chromatography-mass spectrometry (GC-MS) using serially coupled
capillary column. Light chain n-alkanes in the range of C 9–C 17 (43%) and heavy chain n-alkanes in range of C 17–C 23 (34%) and C 23–C 31 (23%) were identified as the major components of total hydrocarbons in the NaCl adapted cells of A. cylindrica. In contrast, NaCl-untreated cells of A. cylindrica had dominance of only long chain n-alkanes in the range of C 23–C 31 comprising about 94% of its total n-alkanes. The persistence of high level (43%) of short chain n-alkanes (C 9–C 17) in NaCl adapted cells of A. cylindrica as compared to its negligible level (0.2%) in NaCl untreated counterpart clearly indicates that NaCl stress causes the A. cylindrica to shift towards the synthesis of short chain n-alkanes. 相似文献
18.
Stands of Scirpus olneyi, a native saltmarsh sedge with C 3 photosynthesis, had been exposed to normal ambient and elevated atmospheric CO 2 concentrations ( Ca) in their native habitat since 1987. The objective of this investigation was to characterize the acclimation of photosynthesis of Scirpus olneyi stems, the photosynthesizing organs of this species, to long-term elevated Ca treatment in relation to the concentrations of Rubisco and non-structural carbohydrates. Measurements were made on intact stems in the Held under existing natural conditions and in the laboratory under controlled conditions on stems excised in the field early in the morning. Plants grown at elevated Ca had a significantly higher (30–59%) net CO 2 assimilation rate ( A) than those grown at ambient Ca when measurements were performed on excised stems at the respective growth Ca. However, when measurements were made at normal ambient Ca, A was smaller (45–53%) in plants grown at elevated Ca than in those grown at ambient Ca. The reductions in A at normal ambient Ca, carboxylation efficiency and in situ carboxylase activity were caused by a decreased Rubisco concentration (30–58%) in plants grown at elevated Ca; these plants also contained less soluble protein (39–52%). The Rubisco content was 43 to 58% of soluble protein, and this relationship was not significantly altered by the growth CO 2 concentrations. The Rubisco activation state increased slightly, but the in situ carboxylase activity decreased substantially in plants grown at elevated Ca. When measurements were made on intact stems in the field, the elevated Ca treatment caused a greater stimulation of, A (100%) and a smaller reduction in carboxylation efficiency (which was not statistically significant) than when measurements were made on excised stems in the laboratory. The possible reasons for this arc discussed. Plants grown at elevated Ca contained more non-structural carbohydrates (25–53%) than those grown at ambient Ca. Plants grown at elevated Ca appear to have sufficient sink capacity to utilize the additional carbohydrates formed during photosynthesis. Overall, our results are in agreement with the hypothesis that elevated C a leads to an increased carbohydrate concentration and the ensuing acclimation of the photo-synthetic apparatus in C 3 plants results in a reduction in the protein complement, especially Rubisco, which reduces the photosynthetic capacity in plants grown at elevated C a, relative to plants grown at normal ambient C a. Nevertheless, when compared at their respective growth C a, Scirpus olneyi plants grown at elevated C a in their native habitat maintained a substantially higher rate of photosynthesis than those grown at normal ambient C a even after 8 years of growth at elevated C a. 相似文献
19.
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
20.
Environmental conditions that promote photorespiration are considered to be a major driving force for the evolution of C 4 species from C 3 ancestors. The genus Flaveria contains C 3 and C 4 species as well as a variety of intermediate species. In this study, we compare the water-use efficiency of intermediate
Flaveria species to that of C 3 and C 4 species. The results indicate that under both well-watered and a drought-stress condition, C 3–C 4 and C 4-like intermediacy in Flaveria species improve water-use efficiency as compared to C 3 species. 相似文献
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