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1.
Effect of temperature on the CO2/O2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase and the rate of respiration in the light 总被引:1,自引:0,他引:1
Responses of the rate of net CO2 assimilation (A) to the intercellular partial pressure of CO2 (p
i
) were measured on intact spinach (Spinacia oleracea L.) leaves at different irradiances. These responses were analysed to find the value of p
i
at which the rate of photosynthetic CO2 uptake equalled that of photorespiratory CO2 evolution. At this CO2 partial pressure (denoted ), net rate of CO2 assimilation was negative, indicating that there was non-photorespiratory CO2 evolution in the light. Hence was lower than the CO2 compensation point, . Estimates of were obtained at leaf temperatures from 15 to 30°C, and the CO2/O2 specificity of ribulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase (E.C. 4.1.1.39) was calculated from these data, taking into account changes in CO2 and O2 solubilities with temperature. The CO2/O2 specificity decreased with increasing temperature. Therefore we concluded that temperature effects on the ratio of photorespiration to photosynthesis were not solely the consequence of differential effects of temperature on the solubilities of CO2 and O2. Our estimates of the CO2/O2 specificity of RuBP carboxylase/oxygenase are compared with in-vitro measurements by other authors. The rate of nonphotorespiratory CO2 evolution in the light (R
d
) was obtained from the value of A at . At this low CO2 partial pressure, R
d
was always less than the rate of CO2 evolution in darkness and appeared to decrease with increasing irradiance. The decline was most marked up to about 100 mol quanta m-2 s-1 and less marked at higher irradiances. At one particular irradiance, however, R
d
as a proportion of the rate of CO2 evolution in darkness was similar in different leaves and this proportion was unaffected by leaf temperature or by [O2] (ambient and greater). After conditions of high [CO2] and high irradiance for several hours, the rate of CO2 evolution in darkness increased and R
d
also increased.Abbreviations and symbols A
rate of net CO2-assimilation
-
CO2 compensation point
-
CO2 compensation point in the absence of R
d
-
p
i
intercellular partial pressure of CO2
-
R
d
(day respiration)
rate of non-photorespiratory CO2 evolution in the light
-
R
n
(night respiration)
rate of CO2 evolution in darkness
- RuBP
ribulose-1,5-bisphosphate
- Rubisco
RuBP carboxylase/oxygenase 相似文献
2.
Measurement of the light response of photosynthetic CO2 uptake is often used as an implement in ecophysiological studies. A method is described to calculate photosynthetic parameters, such as the maximum rate of whole electron transport and dissimilative respiration in the light, from the light response of CO2 uptake. Examples of the light-response curves of flag leaves and ears of wheat (Triticum aestivum cv. ARKAS) are shown.Abbreviations and symbols A
net photosynthesis rate
-
D
1
rate of dissimilative respiration occurring in the light
-
f
loss factor
-
I
incident PPFD
-
I
effective absorbed PPFD
-
J
rate of whole electron transport
-
J
m
maximum rate of whole electron transport
-
p
c
intercellular CO2 partial pressure
- PPFD
photosynthetic photon flux density
-
q
effectivity factor for the use of light (electrons/quanta)
-
absorption coefficient
-
I
*
CO2 compensation point in the absence of dissimilative respiration (bar)
-
II
conversion factor for calculation of CO2 uptake from the rate of whole electron transport
-
convexity factor
Gas-exchange rates relate to the projective area and are given in mol·m-2·s-1. Electron-transport rates are given in mol electrons·m-2·s-1; PPFD is given in mol quanta·m-2·s-1. 相似文献
3.
The light dependence of quantum yields of Photosystem II (II) and of CO2 fixation were determined in C3 and C4 plants under atmospheric conditions where photorespiration was minimal. Calculations were made of the apparent quantum yield for CO2 fixation by dividing the measured rate of photosynthesis by the absorbed light [A/I=CO2 and of the true quantum yield by dividing the estimated true rate of photosynthesis by absorbed light [(A+Rl)/Ia=CO2·], where RL is the rate of respiration in the light. The dependence of the II/CO2 and II/CO2
* ratios on light intensity was then evaluated. In both C3 and C4 plants there was little change in the ratio of II/CO2 at light intensities equivalent to 10–100% of full sunlight, whereas there was a dramatic increase in the ratio at lower light intensities. Changes in the ratio of II/CO2 can occur because respiratory losses are not accounted for, due to changes in the partitioning of energy between photosystems or changes in the relationship between PS II activity and CO2 fixation. The apparent decrease in efficiency of utilization of energy derived from PS II for CO2 fixation under low light intensity may be due to respiratory loss of CO2. Using dark respiration as an estimate of RL, the calculated II/CO2
* ratio was nearly constant from full sunlight down to approx 5% of full sunlight, which suggests a strong linkage between the true rate of CO2 fixation and PS II activity under varying light intensity. Measurements of photosynthesis rates and II were made by illuminating upper versus lower leaf surfaces of representative C3 and C4 monocots and dicots. With the monocots, the rate of photosynthesis and the ratio of II/CO2 exhibited a very similar patterns with leaves illuminated from the adaxial versus the abaxial surface, which may be due to uniformity in anatomy and lack of differences in light acclimation between the two surfaces. With dicots, the abaxial surface had both lower rates of photosynthesis and lower II values than the adaxial surface which may be due to differences in anatomy (spongy versus palisade mesophyll cells) and/or light acclimation between the two surfaces. However, in each species the response of II/CO2 to varying light intensity was similar between the two surfaces, indicating a comparable linkage between PS II activity and CO2 fixation.Abbreviations A
measured rate of CO2 assimilation
- A+RL
true rate of CO2 assimilation; e
- CO2
estimate of electrons transported through PSII per CO2 fixed by RuBP carboxylase
- f
fraction of light absorbed by Photosystem II
- F'm
yield of PSII chlorophyll fluorescence due to a saturating flash of white light under steady-state photosynthesis
- Fs
variable yield of fluorescence under steady-state photosynthesis; PPFD-photosynthetic photon flux density
- Ia
absorbed PPFD
- PS II
Photosystem II
- Rd
rate of respiration in the dark
- RI
rate of respiration in the light estimated from measurement of Rd or from analysis of quantum yields
-
apparent quantum yield of CO2 assimilation under a given condition (A/absorbed PPFD)
-
true quantum yield of CO2 assimilation under a given condition [(A+RL)/(absorbed PPFD)]
-
quantum yield for photosynthetic O2 evolution
-
electrons transported via PS II per quantum absorbed by PS II
Supported by USDA Competitive Grant 90-37280-5706. 相似文献
4.
M. Küppers A. M. Wheeler B. I. L. Küppers M. U. F. Kirschbaum G. D. Farquhar 《Oecologia》1986,70(2):273-282
Summary The rate of CO2 assimilation at light saturation and an intercellular CO2 concentration of 350 l l-1 (photosynthetic capacity), measured in leaves of Eucalyptus pauciflora, E. behriana, E. delegatensis and Acacia melanoxylon, declined over the course of cloudless days under naturally varying environmental conditions as well as under constant optimal conditions for high CO2 uptake. Since the capacity did not recover during the light period, it was different from the midday depression of gas exchange. The change appeared to be caused neither by the diurnal variation of total leaf water potential, by photoinhibition of redox-reaction centres in photosystems nor by changes in the intrinsic properties of Ribulose-bisphosphate carboxylase-oxygenase. The decline was more pronounced in winter than in summer. It was related to the duration of illumination or the cumulative carbon gain. It was reversible in the following dark phase, and it did not occur on changeable days with short peaks of high light.Despite the decline in photosynthetic capacity, the initial slope of the CO2 response of net photosynthesis, as obtained at low intercellular CO2 concentrations, remained constant during the day, but declined at night when photosynthetic capacity recovered. In all cases stomatal conductance varied in parallel with photosynthetic capacity. The relevance of changes in photosynthetic capacity for the intercellular CO2 concentration is discussed.Abbreviations and symbols A
CO2 assimilation
- ABA
abscisic acid
- Ac350
photosynthetic capacity at ci=350l l-1
- ci
intercellular CO2 concentration
- g
leaf conductance to water vapour
- I
photon flux density (irradiance)
- P
air pressure
- Pi
inorganic phosphate
- Rd
net CO2 release at *
- Rubisco
Ribulose-bisphosphate carboxylase-oxygenase
- RuBP
Ribulose-bisphosphate
- T
leaf temperature
- w
leaf-to-air water vapour concentration difference
- A/ci
carboxylation efficiency at low ci
- *
light-independent CO2 compensation point
-
total leaf water potential 相似文献
5.
The underwater light field in the Bellingshausen andAdmundsen Seas was characterised using data collectedduring the R/V Polarstern cruise ANT XI/3, from12.1.94 to 27.3.94. The euphotic zone varied from 24to 100 m depth. Spectral diffuse vertical attenuationcoefficients (K
d
())were determined for 12narrow wavebands as well as for photosyntheticallyavailable radiation (PAR, 400–700 nm): K
d
(490)ranged from 0.03 to 0.26 m1; K
d
(550) from0.04 to 0.17 m1; K
d
(683) from 0.04 to0.17 m1; and K
d
(PAR) varied from 0.02 to0.25 m1. K
d
() for wavelengths centred at412 nm, 443 nm, 465 nm, 490 nm, 510 nm, 520 nm and550 nm were significantly correlated with chlorophyllconcentration (ranging from 0.1 to 6 mg m3). Thevertical attenuation coefficients for 340 nm and380 nm ranged from 0.10 to 0.69 m1 and from 0.05to 0.34 m1, respectively, and were also highlycorrelated with chlorophyll concentrations. These K
d
values indicate that the 1% penetration depthmay reach maxima of 46 m and 92 m for 340 nm and380 nm, respectively. The spectral radiancereflectances (Rr()) for 443 nm, 510 nm and 550 nmwere less than 0.01 sr1. Rr() for 665 nm and683 nm increased with depth up to 0.2 sr1 because ofchlorophyll fluorescence. Using a model that predicts downwardirradiances by taking into account the attenuation bywater and absorption by chlorophyll, we show thatchlorophyll fluorescence has a significant influenceon the red downward irradiance (E
d
(633, 665, 683))in deeper layers. The ability of the phytoplanktonpopulation to influence the light environment byautofluorescence and absorption processes depends onthe light conditions and on the photoacclimation ofthe cells, represented by the in vivo crosssection absorption coefficient of chlorophyll (a*). Theobtained mean chlorophyll-specific light attenuationcoefficients of phytoplankton in situ (k
d
) are higherthan the in vivo absorption coefficient of chlorophyll,more than to be excepted from the scattering. a*(), m2 mg chl1, decreased due topackaging effect with increasing chlorophyllconcentrations. 相似文献
6.
Pekka Lankinen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,159(1):123-142
Summary The time measuring system ofDrosophila littoralis strains originating between 40–70° N was found to be highly variable and latitude dependent. The critical daylength for photoperiodic adult diapause varied from 12 h or no diapause response in the south to 20 h in north. The median timing of pupal eclosion rhythm varied correspondingly from 21 h to 12 h from lights off in LD 321, and the period of free-running rhythm of eclosion from 24 h to 19 h. The phase of the free-running rhythm was also variable, and correlated with the phase of the entrained rhythm. Latitudinal variation in the entrained rhythm of eclosion and in diapause is adaptive, leading to eclosion early in the morning and to overwintering at the adult stage. In some strains with a late phase of eclosion, strong transient cycles were seen following the transition from LL to DD. A total damping of the free-running eclosion rhythm within 2–7 days was common to all strains. This damping was more pronounced in the northern strains. The phase and period of eclosion rhythms were statistically independent. Diapause was not correlated with any parameters of the eclosion rhythm in the analysis. Diapause may still be influenced by the period of the eclosion rhythm, even though its minor contribution may be masked by a more variable, eclosion rhythm independent system in the determination of diapause.Abbreviations, symbols and terms
LD
Light/dark; as in LD 321 meaning a cycle of 3 h light21 h darkness
-
LL
Continuous light
-
DD
Continuous darkness
-
T
Period of a Zeitgeber cycle
-
Natural period of eclosion rhythm in constant conditions
-
EL
Phase of the free-running rhythm of eclosion
-
A
Amplitude of the free-running rhythm of eclosion; possible range is from 4.17% (no rhythmicity) to 20% (the daily eclosion peaks 2–6 within 5 h each)
-
P
Persistence of the free-running rhythm of eclosion; the number of daily eclosion peaks where the mean for five highest hourly percentages still exceed 6%
-
A phase shift, expressed in h; a re-setting of a rhythm; either as an advance shift (i.e. earlier= +), or as a delay shift (i.e. later = –)
-
PRC
Phase-response curve
-
LD
Phase of entrained rhythm of eclosion; e.g.
LD 321 is the median hour of eclosion peak from lights off at LD 321
-
SD
ecl
Amplitude of the entrained rhythm of eclosion; the smaller SDecl the higher the amplitude
-
PPRC
Photoperiodic response curve; proportion of females in diapause displayed as a function of daylength
-
CDL
Critical photoperiod; the photoperiod in the 24 h LD cycle at which 50% of the population studied diapauses
-
SD
diap
Accuracy of diapause response of a strain; the smaller the SDdiap the more accurate the response
-
Cdl
The main locus controlling CDL inD. littoralis 相似文献
7.
Howard Griffiths Mark S. J. Broadmeadow Anne M. Borland Clive S. Hetherington 《Planta》1990,181(4):604-610
Short-term measurements of instantaneous carbon-isotope discrimination have been determined from mass-spectrometric analyses of CO2 collected online during gas exchange for the epiphytic bromeliad Tillandsia utriculata L. Using this technique, the isotopic signature of CO2 exchange for each phase of Crassulacean acid metabolism (CAM) has been characterised. During night-time fixation of CO2 (Phase I), discrimination () ranged from 4.4 to 6.6, equivalent to an effective carbon-isotope ratio (13C) of –12.3 to –14.5 versus Pee Dee Belemnite (PDB). These values reflected the gross photosynthetic balance between net CO2 uptake and refixation of respiratory CO2, characteristic of CAM in the Bromeliaceae. When for the relative proportion of external (p
a
) and internal (p
i) CO2 is taken into account, calculated p
i/p
a decreased during the later part of the dark period from 0.68 to 0.48. Measurements of during Phase II, early in the light period, showed the transition between C4 and C3 pathways, with carboxylation being increasingly dominated by ribulose bisphosphate carboxylase (Rubisco) as increased from 10.5 to 21.2 During decarboxylation in the light period (Phase III), CO2 leaked out of the leaf and the inherent discrimination of Rubisco was expressed. The value of calculated from on-line measurements (64.4) showed that the CO2 lost was considerably enriched in 13C, and this was confirmed by direct analysis of the CO2 diffusing out into a CO2-free atmosphere (
13C = + 51.6 versus PDB). Instantaneous discrimination was characteristic of the C3 pathway during Phase IV (late in the light period), but a reduction in showed an increasing contribution from phosphoenolpyruvate carboxylase. The results from this non-invasive technique confirm the observations that double carboxylation involving both phosphoenolpyruvate carboxylase and Rubisco occurs during the transient phases of CAM (II and IV) in the light period.Abbreviations and Symbols CAM
Crassulacean acid metabolism
-
H+
(dawn-dusk) variation in titratable acidity
-
13C
carbonisotope ratio of plant organic material, relative to Pee Dee Belemnite (vs. PDB)
-
discrimination against 13CO2,
-
p
i, p
a
internal, external partial pressures of CO2
- Rubisco
ribulose1,5-bisphosphate carboxylase
- PAR
photosynthetically active radiation
- PEPCase
phosphoenolpyruvate carboxylase
We are grateful for financial support in respect of research grants (GR3/5360, GR3/6419) and a studentship awarded by the Natural Environment Research Council, UK. 相似文献
8.
Acclimation of barley to changes in light intensity: photosynthetic electron transport activity and components 总被引:9,自引:0,他引:9
Barley seedlings (Hordeum vulgare L. Boone) were grown at 20°C with 16 h/8 h light/dark cycle of either high (H) intensity (500 mole m-2 s-1) or low (L) intensity (55 mole m-2 s-1) white light. Plants were transferred from high to low (H L) and low to high (L H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod. Thylakoid membranes were isolated from 3 cm apical segments and assayed for photosynthetic electron transport, Photosystem II (PS II) atrazine-binding sites (QB), cytochrome f(Cytf) and the P-700 reaction center of Photosystem I (PS I). Whole chain, PS I and PS II electron transport activities were higher in H than in L controls. QB and Cytf were elevated in H plants compared with L plants. The acclimation of H L plants to low light occurred slowly over a period of 7 days and resulted in decreased whole chain and PS II electron transport with variable effects on PS I activity. The decrease in electron transport of H L plants was associated with a decrease in both QB and Cytf. In L H plants, acclimation to high light occurred slowly over a period of 7 days with increased whole chain, PS I and PS II activities. The increase in L H electron transport was associated with increased levels of QB and Cytf. In contrast to the light intensity effects on QB levels, the P-700 content was similar in both control and transferred plants. Therefore, PS II/PS I ratios were dependent on light environment.Abbreviations Asc
ascorbate
- BQ
2,5-dimethyl-p-benzoquinone
- DBMIB
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone
- DCIP
2,6-dichlorophenolindophenol
- H
control plants grown under high light intensity
- H L
plants transferred from high to low light intensity
- L
low control plants grown under low light intensity
- L H
plants transferred from low to high light intensity
- MV
methyl viologen
- P-700
photoreaction center of Photosystem I
- QB
atrazine binding site
- TMPD
N,N,N,N-tetramethyl-p-phenylenediamine
Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC. Paper No. 11990 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, USA. 相似文献
9.
R. Schwind 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,177(4):439-448
For diverse water insects (species of Hydrophilidae, Hadraenidae, Dytiscidae, Haliplidae and aquatic Heteroptera), the attractiveness of an artificial water surface was found to vary when the polarization of the reflected light, the property by which these insects identify water, was abolished in different regions of the spectrum. The sensitivity maxima of their reflection-polarization visual systems (max(POL)) thus determined were in various spectral regions, between < 360 nm (UV) and ca. 550 nm (yellow-green). Species with max(POL) at the short-wavelength end of the spectrum would be able to identify bodies of water by polarization regardless of whether the subsurface reflection was bright or dark; nevertheless, this group includes forms that avoid water with a bright subsurface because of the intensity of the reflected light. Species with max(POL) in the long-wavelength region fail to use certain bodies of water with a bright subsurface as habitats because the light they reflect at the longer wavelengths is insufficiently polarized. That the POL system of a species has a large max could affect habitat choice; on the other hand, it could also be that systems operating in the long-wavelength region were produced in the course of adaptation to the light conditions in or above the habitat.Abbreviations
max(POL)
spectral sensitivity maximum for polarization vision 相似文献
10.
The cyclic 35-nucleotide phosphodiesterase D3 was purified from Sinorhizobium fredii MAR-1. The native enzyme had a molecular weight of approximately 44.5kDa and a subunit molecular weight of approximately 21kDa as judged by SDS-gel electrophoresis. The pH optimum of the enzyme for the hydrolysis of cyclic AMP was approximately 6.0 with both acetate and Tris-maleate buffers. The optimum temperature for hydrolysing cyclic AMP was approximately 50C. No metal ion was required for activity and EDTA up to 2.5mM did not markedly affect the enzyme. However, methylxanthines, adenine and adenosine as well as 5-AMP, ATP, ADP and metal ions like Zn2+, Fe2+, Pb2+, Al3+ and Fe3+, were strongly inhibitory at 2.5mM.The D3 enzyme could hydrolyse both cyclic AMP and cyclic GMP with the apparent K
m for cyclic AMP of approximately 0.23M. 相似文献
11.
Chlorobium limicola has been proposed to assimilate CO2 autotrophically via a reductive tricarboxylic acid cycle rather than via the Calvin cycle. This proposal has been a matter of considerable controversy. In order to determine which pathway is operative, the bacterium was grown on a mineral salts medium with CO2 as the main carbon source supplemented with specifically labeled 14C-pyruvate, and the incorporation of 14C into alanine (intracellular pyruvate), aspartate (oxaloacetate), glutamate (-ketoglutarate), and glucose (hexosephosphate) was measured in exponentially growing cells in long term labeling experiments. During growth in presence of pyruvate, 20% of the cell carbon were derived from pyruvate in the medium, 80% from CO2. Since pyruvate was not oxidized to CO2, only those compounds should become labeled which were synthesized from CO2 via pyruvate.The three amino acids and glucose were found to be labeled. Alanine had one fifth the specific radioactivity of the extracellular pyruvate, indicating that 20% of the intracellular pyruvate pool were derived from pyruvate in the medium, 80% were synthesized from CO2. Glucose had twice the specific radioactivity of alanine, showing that hexosephosphate synthesis from CO2 proceeded via the pyruvate pool. The latter finding is not consistent with the operation of the Calvin cycle, in which pyruvate is not an intermediate. The specific radioactivities of aspartate (oxaloacetate) and of glutamate (-ketoglutarate) were practically identical but considerably lower than that of alanine ( intracellular pyruvate). These findings are compatible with the operation of a reductive tricarboxylic acid cycle as mechanism of autotrophic CO2 fixation. Degradation studies of the cell components support this interpretation.
Offprint requests to: G. Fuchs 相似文献
12.
Summary Soluble lead salts and a number of lead-containing minerals catalyze the formation of oligonucleotides from nucleoside 5-phosphorimidazolides. The effectiveness of lead compounds correlates strongly with their solubility. Under optimal conditions we were able to obtain 18% of pentamer and higher oligomers from ImpA. Reactions involving ImpU gave smaller yields.Abbreviations A
adenosine
-
U
uridine
-
Im
imidazole
-
MeIm
1-methyl-imidazole
-
EDTA
ethylenediaminetetraacetic acid
-
pA
adenosine 5-phosphate
-
pU
uridine 5-phosphate
-
Ap
adenosine cyclic 2:3-phosphate
-
ATP
adenosine 5-triphosphate
-
AppA
P1,P2-diadenosine 5-diphosphate
-
pNp (N = A,U)
nucleotide 2(3), 5-diphosphate
-
ImpA
adenosine 5-phosphoreimidazolide
-
ImpU
uridine 5-phosphorimidazolide
-
A
2pA
adenylyl-[25]-adenosine
-
A
3pA
adenylyl-[35]-adenosine
-
pA
2pA
5-phospho-adenylyl-[25]-adenosine
-
pA
3pA
5-phospho-adenylyl-[35]-adenosine
-
pUpU
5-phospho-uridylyl-uridine
-
pApU
5-phospho-adenylyl-uridine
-
pUpA
5-phospho-uridylyladenine
-
(pA)n (n, 2,3,4,)
oligoadenylates with 5 terminal phosphate
-
ImpApA
5-phosphorimidazolide of adenylyl adenosine
-
(pA)
5+
pentamer and higher oligoadenylates with 5 terminal phosphate
-
(Ap)nA (n = 2,3,4)
oligoadenylates without terminal phosphates
In the following we do not specify the nature of the internucleotide linkageIn the following we do not specify the nature of the internucleotide linkage 相似文献
13.
Elevated CO2 (ambient + 35 Pa) increased shoot dry mass production in Avena fatua by 68% at maturity. This increase in shoot biomass was paralleled by an 81% increase in average net CO2 uptake (A) per unit of leaf area and a 65% increase in average A at the ecosystem level per unit of ground area. Elevated CO2 also increased ecosystem A per unit of biomass. However, the products of total leaf area and light-saturated leaf A divided by the ground surface area over time appeared to lie on a single response curve for both CO2 treatments. The approximate slope of the response suggests that the integrated light saturated capacity for leaf photosynthesis is 10-fold greater than the ecosystem rate. Ecosystem respiration (night) per unit of ground area, which includes soil and plant respiration, ranged from-20 (at day 19) to-18 (at day 40) mol m-2 s-1 for both elevated and ambient CO2
Avena. Ecosystem below-ground respiration at the time of seedling emergence was -10 mol m-2 s-1, while that occuring after shoot removal at the termination of the experiment ranged from -5 to-6 mol m-2 s-1. Hence, no significant differences between elevated and ambient CO2 treatments were found in any respiration measure on a ground area basis, though ecosystem respiration on a shoot biomass basis was clearly reduced by elevated CO2. Significant differences existed between leaf and ecosystem water flux. In general, leaf transpiration (E) decreased over the course of the experiment, possibly in response to leaf aging, while ecosystem rates of evapotranspiration (ET) remained constant, probably because falling leaf rates were offset by an increasing total leaf biomass. Transpiration was lower in plants grown at elevated CO2, though variation was high because of variability in leaf age and ambient light conditions and differences were not significant. In contrast, ecosystem evapotranspiration (ET) was significantly decreased by elevated CO2 on 5 out of 8 measurement dates. Photosynthetic water use efficiencies (A/E at the leaf level, A/ET at the ecosystem level) were increased by elevated CO2. Increases were due to both increased A at leaf and ecosystem level and decreased leaf E and ecosystem ET. 相似文献
14.
The fluorescent calcium-sensitive dye 1-[2-amino-5-(6-carboxyindol-2-yl)-phenoxy]-2-(2-amino-5-methylphenoxy)-ethane-N,N,N,N-tetraacetic acid (indo-1) was loaded by a transplasmalemma pH gradient into filamentous cells and protoplasts of Mougeotia scalaris, such that most of the indo-1 fluorescence originated from the cytoplasm. Incubation of M. scalaris filaments in ethylene glycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA)-buffered media (-log [Ca2+] (=pCa) 8 versus pCa 3) caused a consistent and significant decrease in the cytoplasmic free [Ca2+]. Pulses of the fluorescence excitation light (UV-A 365 nm, 0.7 s) caused an increase in cytoplasmic free [Ca2+] in M. scalaris that was nearly independent of the external [Ca2+] and of chloroplast dislocation by centrifugation. This calcium flux, highest in UV-A light, compared with blue or red light, probably resulted from a release of Ca2+ from intracellular stores. Increased cytoplasmic [Ca2+] may affect the velocity of chloroplast rotation since UV-A-light-mediated chloroplast movement was faster than in blue or red light. Consistently, the calcium ionophore A23187 and the calcium-channel agonist Bay-K8644 both increased the velocity of the red-light-mediated chloroplast rotation. Based on these and other observations, a Ca2+-induced decrease in cytoplasmic viscosity in Mougeotia is presumed to occur.Abbreviations EGTA
ethylene glycol-bis-(-aminoethyl ether)N,N,N,N-tetraacetic acid
- indo-1
1-[2-amino-5-(6-carboxyindol-2-yl)-phenoxy]-2-(2-amino-5-methylphenoxy)-ethane-N,N,N,Ntetraacetic acid
- pCa
log [Ca2+]
- Pfr
far-red-absorbing form of phytochrome
- Pr
red-absorbing form of phytochrome
- xG
geometric mean
Dedicated to Professor Wolfgang Haupt on the occasion of his 70th birthdayThis paper is part of the Ph.D. thesis of U. Russ at the Justus-Liebig-Universitat Giessen (FRG). Part of this work has been presented at a meeting on Calcium and intracellular signalling in plants in Plymouth, UK, Dec. 1990We are indebted to Dr. G. Seibold and Dipl. Phys. H. Weintraut for their advice on the technique of microspectrofluorometry and for allowing access to the microspectrophotometric facilities in the Strahlenzentrum der Justus-Liebig-Universität, Giessen, FRG. We thank Mrs. A. Quanz for reliable culture of the algae and evaluation of the videotapes. Bay-K8644 was a generous gift of Bayer AG, Wuppertal, FRG. U. russ was supported by a scholarship according to the Hessisches Graduierten Förderungsgesetz. This work was supported by the Deutsche Forschungsgemeinschaft. 相似文献
15.
Micropropagated plantlets are fragile and often lack sufficient vigour to survive the acclimatization shock during transplantation to the soil. Effects of photosynthetic photon flux densities (PPFDs) on growth, photosynthesis and anatomy of micropropagated Doritaenopsis were studied after 4 months of acclimatization in a greenhouse at 25 °C. The plantlets were transferred to three different PPFDs for four months, i.e. low light (175), intermediate light (270) and high light (450 mol m–2 s–1). For most of the growth parameters measured i.e. leaf length, leaf area, leaf width, fresh weight, dry weight, chlorophyll (Chl) a/b ratio, were greater for the intermediate light levels after 4 months of acclimatization. The only exception was leaf thickness, which was increased more under high light levels. Results showed that the survival of Doritaenopsis plantlets was greatest (90%) in low light and intermediate light (89%) compared with only (73%) at high light. However, at low light levels, pigment concentrations (chlorophyll a, b and total chlorophyll) were higher. Net CO2 assimilation (A), stomatal conductance (g) and transpiration (E) were higher in plantlets grown at high level PPFD than at low after 4 months of acclimatization. Photosynthetic efficiency (Fv/Fm) decreased insignificantly; only at mid day for the high light treatment whereas leaf temperature and stomatal closure increased compared to low light. Scanning electron microscopic (SEM) images of leaves from acclimatized plantlets showed an increase in wax formation for the high light grown plantlets compared to those at low light. Microscopic analysis of acclimatized root sections showed highly developed multiseriate-velamen layers and higher root cell activity; while shoots had larger leaf air spaces than those of in vitro grown plantlets. These results suggest that physiological acclimation occurs at the intermediate PPFD (270 mol m–2 s–1) in Doritaenopsis compared to treatment at the high light level. 相似文献
16.
Khehra A. S. Singh H. Dhillon B. S. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,69(3):259-261
Summary The nature and magnitude of variability in the interpopulation cross of Mezcla Amarillo Selection (MAS), an introduction from CIMMYT, Mexico, and J607, a population developed in India using indigenous, American, and Yugoslavian germplasm, were studied. Interpopulation progenies developed by following the North Carolina Design I were evaluated at two locations. The additive genetic variance component in interpopulation cross,
A(12)
2
, and in one population assuming the other population as tester,
A12
2
and
A21
2
were significant for all the traits evaluated, namely ear length, ear girth, kernel rows and days to silk, with one exception. For kernel rows, the dominance variance component,
A(12)
2
, was also significant but it was smaller than
A(12)
2
. The variance component due to dominance X location interaction,
DL(12)
2
, was significant for all traits except kernel rows. In the case of ear length and ear girth,
DL(12)
2
was greater than the other components.
AL(12)
2
,
AL12
2
and
AL21
2
were not significant for any trait. Expected genetic advance indicated a superiority of half-sib reciprocal recurrent selection over full-sib reciprocal recurrent selection. 相似文献
17.
Summary Photosynthetic characteristics of two important grasses of Indian desert have been studied. Pennisetum typhoides, an important cereal crop, known to have Kranz-type leaf anatomy and low CO2-compensation point, shows the C-4-dicarboxylic acid pathway for photosynthetic carbon reduction. Lasiurus sindicus, a promising forage grass, has also been shown to possess, for the first time, a typical Kranz-type leaf anatomy and a very similar CO2-fixation pattern like Pennisetum typhoides. It is remarkable that both species after short time exposure to 14CO2 show a high labelling not only in malate but also in alanine. This may be due to the activity of an aspartic acid decarboxylase. 相似文献
18.
Internal motions of d-ribose selectively 2H-labeled at the 2 position were measured using solid state 2H NMR experiments. A sample of d-ribose-2
-d was prepared in a hydrated, non-crystalline state to eliminate effects of crystal-packing. Between temperatures of –74 and –60°C the C2–H2 bond was observed to undergo two kinds of motions which were similar to those of C2–H2/H2 found previously in crystalline deoxythymidine (Hiyama et al. (1989) J. Am. Chem. Soc., 111, 8609–8613): (1) Nanosecond motion of small angular displacement with an apparent activation energy of 3.6 ± 0.7 kcal mol–1, and (2) millisecond to microsecond motion of large amplitude with an apparent activation energy 4 kcal mol–1. At –74°C, the slow, large-amplitude motion was best characterized as a two-site jump with a correlation time on the millisecond time scale, whereas at –60°C it was diffusive on the microsecond time scale. The slow, large-amplitude motions of the C2–H2 bond are most likely from interconversions between C2-endo and C3-endo by way of the O4-endo conformation, whereas the fast, small-amplitude motions are probably librations of the C2–H2 bond within the C2-endo and C3-endo potential energy minima. 相似文献
19.
During the visual process, light absorption in the 11-cis retinylidene chromophore leads to a rapid cis-trans-isomerization which initiates the phototransduction step. Important spectroscopic properties of this chromophore can be derived from polarized UV-absorption spectra of crystalline 11-cis-retinal if a parallel X-ray structure analysis is performed. Several questions about the relation between molecular geometry and spectroscopic behavior could not be answered from these spectra. All crystal forms of 11-cis-retinal contain this molecule in its 6-s-cis-ring conformation. For the retinal homologue, -8-apocarotenal (APC), however, two crystal forms with different ring conformation can be grown. The spectrum of -APC (6-s-cis) shows a vibronic structure whereas that of -APC (6-s-trans) is diffuse but has a distinct shoulder on the low energy side of the main band. This S-band is typical for retinal spectra and has been ascribed to a transition into a 1A
g
-*
-state. The appearance of the S-band is not correlated with a 6-s-cis-conformation as suggested by the retinal spectra but is due to intermolecular interactions: -APC has a dense dimer packing and a strong electrostatic interaction between the -electron systems. This might cause the forbidden 1A
g
-*
-transition. On the other hand, this interaction is missing in the loose and polar packing of -APC which favors vibration in the polyene chain. This finding is remarkable in view of the photodynamic behavior of the visual chromophore for which strong electrostatic interactions with the protein helices of its binding site have to be postulated.Abbreviations APC
8--Apocarotenal
- -APC/-APC
/-form of crystallized APC
- -CIS/-CIS
/-form of crystallized 11-cis-retinal
- ATR
all-trans retinal
- UV
ultraviolet light
- CI
quantum-mechanical calculation employing configuration interaction
- PPP-MRD
quantum-mechanical calculations after Pariser, Parr, Pople employing multireference determinants
- S-bands
shoulder on main absorption band
- R, S
right, left enantiomer
- EtOH
ethyl alcohol
- PE
petroleum ether
- E
direction of electric vector of incident light
-
b
crystallographic b-axis 相似文献
20.
Palmaria palmata, which is able to use HCO
inf3
sup–
as a carbon source for photosynthesis, and Lomentaria articulata, which is dependent on diffusive uptake of dissolved CO2, were grown under constant light and light with sunflecks designed to model wave-induced fluctuations of near-shore underwater light. Both species exhibited significantly increased stable carbon isotope discrimination (more negative values of 13C relative to PDB) when grown with sunflecks. More negative 13C values were associated with decreased growth rate of P. palmata but not of L. articulata. The contrasting effects of sunflecks on the carbon-use characteristics of the two species are discussed in terms of the energetic cost of HCO
inf3
sup–
use and the susceptibility of CO2 diffusion-dependent species to photoinhibition. 相似文献