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1.
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
2.
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
3.
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
4.
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
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.
C 4 plants have two carboxylases which function in photosynthesis. One, phosphoenolpyruvate carboxylase (PEPC) is localized in mesophyll cells, and the other, ribulose bisphosphate carboxylase (RuBPC) is found in bundle sheath cells. In contrast, C 3 plants have only one photosynthetic carboxylase, RuBPC, which is localized in mesophyll cells. The expression of PEPC in C 3 mesophyll cells is quite low relative to PEPC expression in C 4 mesophyll cells. Two chimeric genes have been constructed consisting of the structural gene encoding β-glucuronidase (GUS) controlled by two promoters from C 4 (maize) photosynthetic genes: (i) the PEPC gene ( pepc) and (ii) the small subunit of RuBPC ( rbcS). These constructs were introduced into a C 3 cereal, rice. Both chimeric genes were expressed almost exclusively in mesophyll cells in the leaf blades and leaf sheaths at high levels, and no or very little activity was observed in other cells. The expression of both genes was also regulated by light. These observations indicate that the regulation systems which direct cell-specific and light-inducible expression of pepc and rbcS in C 4 plants are also present in C 3 plants. Nevertheless, expression of endogenous pepc in C 3 plants is very low in C 3 mesophyll cells, and the cell specificity of rbcS expression in C 3 plants differs from that in C 4 plants. Rice nuclear extracts were assayed for DNA-binding protein(s) which interact with a cis-regulatory element in the pepc promoter. Gel-retardation assays indicate that a nuclear protein with similar DNA-binding specificity to a maize nuclear protein is present in rice. The possibility that differences in pepc expression in a C 3 plant (rice) and C 4 plant (maize) may be the result of changes in cis-acting elements between pepc in rice and maize is discussed. It also appears that differences in the cellular localization of rbcS expression are probably due to changes in a trans-acting factor(s) required for rbcS expression. 相似文献
7.
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
8.
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
9.
The effect of drought stress (DS) on photosynthesis and photosynthesis-related enzyme activities was investigated in F. pringlei (C 3), F. floridana (C 3–C 4), F. brownii (C 4-like), and F. trinervia (C 4) species. Stomatal closure was observed in all species, probably being the main cause for the decline in photosynthesis in
the C 3 species under ambient conditions. In vitro ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and stromal fructose 1,6-bisphosphatase (sFBP) activities were sufficient
to interpret the net photosynthetic rates ( P
N), but, from the decreases in P
N values under high CO 2 ( C
a = 700 μmol mol − 1) it is concluded that a decrease in the in vivo rate of the RuBPCO reaction may be an additional limiting factor under DS in the C 3 species. The observed decline in the photosynthesis capacity of the C 3–C 4 species is suggested to be associated both to in vivo decreases of RuBPCO activity and of the RuBP regeneration rate. The decline of the maximum P
N observed in the C 4-like species under DS was probably attributed to a decrease in maximum RuBPCO activity and/or to decrease of enzyme substrate
(RuBP or PEP) regeneration rates. In the C 4 species, the decline of both in vivo photosynthesis and photosynthetic capacity could be due to in vivo inhibition of the phospho enolpyruvate carboxylase (PEPC) by a twofold increase of the malate concentration observed in mesophyll cell extracts from DS
plants. 相似文献
10.
Summary Bovine serum albumin (BSA) was recovered from aqueous solutions by foam flotation. The protein concentrations in foam liquid C
S, in feed C
Pand in residue C
Rwere determined. The protein enrichment C
S/C Pand the separation C
S/C Ras well as the protein fraction in the foam liquid % BSA and foam liquid volume flow were determined as functions of the medium properties, operational conditions, and equipment parameters as well as concentrations of solid particles. At low protein concentrations in feed (e.g., C
P=40 mg · l -1), and at 40° C, high performance was attained ( C
X=2,000 mg · l -1, C
R=4.4 mg · l -1, C
S/C P=50, C
S/C R=450, 90% BSA. Continuous foam flotation is an efficient procedure for the recovery of low concentrations of proteins from liquid cultures.Abbreviations BSA
bovine serum albumine
-
C
P
protein concentration in feed (mg · l -1)
-
C
R
protein concentration in residue (mg · l -1)
-
C
S
protein concentration in foam liquid (mg · l -1)
-
C
S/C R
protein separation (-)
-
C
S/C P
protein enrichment (-)
-
V
P
feed rate (ml · min -1)
-
V
R
residue flow rate (ml · min -1)
-
V
S
foam liquid volume flow (ml · min -1)
-
N
number of theoretical stages in an ideal cascade (-)
-
temperature (° C)
-
mean residence time (min) 相似文献
11.
Photosynthetic pathway characteristics were studied in nine species of Heliotropium ( sensu lato, including Euploca), using assessments of leaf anatomy and ultrastructure, activities of PEP carboxylase and C 4 acid decarboxylases, and immunolocalization of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) and the P‐subunit of glycine decarboxylase (GDC). Heliotropium europaeum, Heliotropium calcicola and Heliotropium tenellum are C 3 plants, while Heliotropium texanum and Heliotropium polyphyllum are C 4 species. Heliotropium procumbens and Heliotropium karwinskyi are functionally C 3, but exhibit ‘proto‐Kranz’ anatomy where bundle sheath (BS) cells are enlarged and mitochondria primarily occur along the centripetal (inner) wall of the BS cells; GDC is present throughout the leaf. Heliotropium convolvulaceum and Heliotropium greggii are C 3–C 4 intermediates, with Kranz‐like enlargement of the BS cells, localization of mitochondria along the inner BS wall and a loss of GDC in the mesophyll (M) tissue. These C 3–C 4 species of Heliotropium probably shuttle photorespiratory glycine from the M to the BS tissue for decarboxylation. Heliotropium represents an important new model for studying C 4 evolution. Where existing models such as Flaveria emphasize diversification of C 3–C 4 intermediates, Heliotropium has numerous C 3 species expressing proto‐Kranz traits that could represent a critical initial phase in the evolutionary origin of C 4 photosynthesis. 相似文献
12.
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
13.
A biological system consisting of a population of cells suspended in a liquid substrate is considered. The general problem
addressed in the paper is the derivation of the kinetic pattern of population growth as a statistical effect of a very large
number of elementary interactions between a single cell and the molecules of nutrient in substrate. Solution of the problem
is obtained in the form of equation expressing the population growth rate c as a function of substrate concentration, C
s. The analytical expression derived is applied to a real bacterial population ( Escherichi coli) and kinetic patterns are theoretically computed. The major findings, expressed roughly, without nuances, are: (i) the concentration
of nutrient at the cell membrane, C
c, can only be equal to either 0 (for the C
s below some threshold value C
*) or C
s (for C
s> C
*); (ii) the Michaelis-Menten-Monod kinetics observed in experiments is an artifact: the pure (not contaminated by foreign
factors) dependence of c on C
s is actually such that the function c=c(C
s) has practically linear increase when C
s< C
*, and is constant, c=c(C
*)=const, when C
s> C
*; (iii) the Liebig principle is strictly fulfilled: up to a feasible accuracy of observation, under no circumstances can population
growth be limited (controlled) by more than one substrate component—replacement of a limiting component for another one is
an instant event rather than a gradual process. 相似文献
14.
The rapid increase in atmospheric CO 2 concentrations ( Ca) has resulted in extensive research efforts to understand its impact on terrestrial ecosystems, especially carbon balance. Despite these efforts, there are relatively few data comparing net ecosystem exchange of CO 2 between the atmosphere and the biosphere (NEE), under both ambient and elevated Ca. Here we report data on annual sums of CO 2 (NEE net) for 19 years on a Chesapeake Bay tidal wetland for Scirpus olneyi (C 3 photosynthetic pathway)‐ and Spartina patens (C 4 photosynthetic pathway)‐dominated high marsh communities exposed to ambient and elevated Ca (ambient + 340 ppm). Our objectives were to (i) quantify effects of elevated Ca on seasonally integrated CO 2 assimilation (NEE net = NEE day + NEE night, kg C m ?2 y ?1) for the two communities; and (ii) quantify effects of altered canopy N content on ecosystem photosynthesis and respiration. Across all years, NEE net averaged 1.9 kg m ?2 y ?1 in ambient Ca and 2.5 kg m ?2 y ?1 in elevated Ca, for the C 3‐dominated community. Similarly, elevated Ca significantly ( P < 0.01) increased carbon uptake in the C 4‐dominated community, as NEE net averaged 1.5 kg m ?2 y ?1 in ambient Ca and 1.7 kg m ?2 y ?1 in elevated Ca. This resulted in an average CO 2 stimulation of 32% and 13% of seasonally integrated NEE net for the C 3‐ and C 4‐dominated communities, respectively. Increased NEE day was correlated with increased efficiencies of light and nitrogen use for net carbon assimilation under elevated Ca, while decreased NEE night was associated with lower canopy nitrogen content. These results suggest that rising Ca may increase carbon assimilation in both C 3‐ and C 4‐dominated wetland communities. The challenge remains to identify the fate of the assimilated carbon. 相似文献
15.
A homologous series of eleven δ-lactones (1,5-alkanolides) was identified in cuticular waxes from leaves of Cerinthe minor L., six of them representing novel compounds. They accounted for 79% of the total coverage of 41 μg wax per cm 2 leaf area. Various chemical transformations with product identification by GC-mass spectrometry and GC-FTIR were employed to assign the structures. The chain-lengths of the δ-lactones ranged from C 22 to C 32 and even-numbered homologues were prevalent. Additionally, aldehydes (C 26–C 30), alkanes (C 23–C 29), primary alcohols (C 26–C 32), alkanoic acids (C 20–C 32), wax esters (C 40–C 56) and lupeol were detected. 相似文献
16.
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
17.
The effect of elevated carbon dioxide (600±50 cm 3 m −3; C 600) on growth performance, biomass production, and photosynthesis of Cenchrus ciliaris L. cv. 3108 was studied. This crop responded significantly by plant height, leaf length and width, and biomass production
under C 600. Leaf area index increased triple fold in the crops grown in the open top chamber with C 600. The biomass production in term of fresh and dry biomass accumulation increased by 134.35 (fresh) and 193.34 (dry) % over
the control (C 360) condition where the crops were grown for 20 d. The rate of photosynthesis and stomatal conductance increased by 24.51 and
46.33 %, respectively, in C 600 over C 360 plants. In comparison with C 360, the rate of transpiration decreased by 6.8 % under C 600. Long-term exposure (120 d) to C 600 enhanced photosynthetic water use efficiency by 34 %. Also the contents of chlorophylls a and b significantly increased in C 600. Thus C. ciliaris grown in C 600 throughout the crop season may produce more fodder in terms of green biomass. 相似文献
18.
The protein content of the filamentous Cladophora glomerata (L.) Kz., Ulothrix zonata (Web, & Mohr) Kz. and Spirogyra sp., collected from natural populations for 1 year, averaged 8.0–12.4% of the total dry weight; whereas, the corresponding levels of lipid, cellulose and ash were 11.9–16.1%, 10.0–17.8% and 14.6–24.0%, respectively. Mean values for carbohydrates, estimated by difference, ranged from 32.8 to 56.0%. The colonial Scenedesmus dimorphus (Turp.) Kz. and the unicellular Cosmarium laeve Rab., on the other hand, contained more protein, lipid and carbohydrate (estimated by difference) averaging 13–15.0%, 22.5–25.9% and 415–46.8%, respectively, and less cellulose (7.5–9.8%) and ash (8.2–9.8%). A consistent pattern of seasonal variation in the proximate composition was not normally evident for any species, reflecting the influence of several environmental parameters on the algae. Cladophora contained the greatest amount of phospholipid averaging; 10% by weight of total lipid with the smallest quantity (5%) in Scenedesmus. The predominant phospholipid fatty acid in all species was C 18:1 followed by C 18:2, C 18:3 and C 16:1 in Cladophora, Ulothrix and Spirogyra, and C 16:1, C 18:2 and C 16:0 in Scenedesmus and Cosmarium. Oleic (C 18:1) and hexadecanoic (C 16:1) acids were predominant in the neutral lipids of all the algae, followed by C 16:0, C 18:2 and C 18:3. The concentration of the different fatty acids of each Species varied considerably during the year with the proportion of C 16:0 and C 16:1, usually rising and that of C 18:1 failing during the colder months. 相似文献
19.
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
20.
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
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