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1.
In the leaves (but not corms) of the submerged aquatic plant Isoetes howellii, malic acid concentration fluctuates from 1–3 mg g –1 FW in the evening to 7–13 mg g –1 FW in the morning. Associated with this is a change in pH (a.m. pH 3–4 vs. p.m. pH 5–6) and titratable acidity (75–200 μ eq g –1 FW change in acidity between morning and evening) of the plant extract. 14CO 2-fixation experiments indicate that carbon is fixed in both the light and the dark, though the amount of carbon fixed in the light is more than double that fixed in the dark. Autoradiographs show 89% of dark-fixed CO 2 ends up in malic acid and the remainder in citric acid, whereas these two acids constitute less than 5% of the light-fixation products. It is suggested that CAM metabolism in this aquatic species may be related to the lower availability of CO 2 for photosynthesis during the day than during the night in its aquatic environment. 相似文献
2.
Luronium natans (L.) Raf. (Floating Water-plantain) is an endangered amphibious freshwater species endemic to Europe. We examined the plasticity in carbon acquisition and photosynthesis in L. natans to assess if lack of plasticity could contribute to explain the low competitive ability of the species. The plasticity of photosynthesis in submerged leaves towards inorganic carbon availability was examined and the photosynthesis of submerged, floating and aerial leaves was contrasted. L. natans was shown to be plastic in inorganic carbon uptake, as it was able to effectively acclimate to changed concentrations of free-CO 2. The photosynthetic apparatus was down-regulated in plants grown at high CO 2. Chlorophyll concentration, Rubisco activity and maximum photosynthesis were significantly lower in submerged leaves of plants grown at high CO 2 (200 μM free-CO 2) compared to plants grown at low CO 2 (18 μM free-CO 2). Furthermore, bicarbonate utilization was down-regulated in response to high CO 2. Carbon acquisition of submerged, floating and aerial leaves of L. natans differed significantly. The aerial leaves were superior in photosynthesising in air and, surprisingly, the floating leaves had the highest rates of photosynthesis in water. The study did not support the hypothesis that the low competitive ability of L. natans is caused by inefficient photosynthesis or a lack of plasticity in photosynthesis. However, the somewhat low photosynthetic performance of the submerged leaves may be a contributing factor. 相似文献
3.
The submerged aquatic plant Isoetes howellii Engelmann possesses Crassulacean acid metabolism (CAM) comparable to that known from terrestrial CAM plants. Infrared gas analysis of submerged leaves showed Isoetes was capable of net CO 2 uptake in both light and dark. CO 2 uptake rates were a function of CO 2 levels in the medium. At 2,500 microliters CO 2 per liter (gas phase, equivalent to 1.79 milligrams per liter aqueous phase), Isoetes leaves showed continuous uptake in both the light and dark. At this CO 2 level, photosynthetic rates were light saturated at about 10% full sunlight and were about 3-fold greater than dark CO 2 uptake rates. In the dark, CO 2 uptake rates were also a function of length of time in the night period. Measurements of dark CO 2 uptake showed that, at both 2,500 and 500 microliters CO 2 per liter, rates declined during the night period. At the higher CO 2 level, dark CO 2 uptake rates at 0600 h were 75% less than at 1800 h. At 500 microliters CO 2 per liter, net CO 2 uptake in the dark at 1800 h was replaced by net CO 2 evolution in the dark at 0600 h. At both CO 2 levels, the overnight decline in net CO 2 uptake was marked by periodic bursts of accelerated CO 2 uptake. CO 2 uptake in the light was similar at 1% and 21% O 2, and this held for leaves intact as well as leaves split longitudinally. Estimating the contribution of light versus dark CO 2 uptake to the total carbon gain is complicated by the diurnal flux in CO 2 availability under field conditions. 相似文献
4.
Photosynthetic gas exchange and malic acid fluctuations were monitored in 69 well-watered plants from five morphologically similar species of Talinum in an investigation of the ecophysiological significance of the Crassulacean acid metabolism (CAM)-cycling mode of photosynthesis. Unlike CAM, atmospheric CO 2 uptake in CAM-cycling occurs exclusively during the day; at night, the stomata are closed and respiratory CO 2 is recaptured to form malic acid. All species showed similar patterns of day-night gas exchange and overnight malic acid accumulation, confirming the presence of CAM-cycling. Species averages for gas exchange parameters and malic acid fluctuation were significantly different such that the species with the highest daytime gas exchange had the lowest malic acid accumulation and vice versa. Also, daytime CO 2 exchange and transpiration were negatively correlated with overnight malic acid fluctuation for all individuals examined together, as well as within one species. This suggests that malic acid may effect reductions in both atmospheric CO 2 uptake and transpiration during the day. No significant correlation between malic acid fluctuation and water-use efficiency was found, although a nonsignificant trend of increasing water-use efficiency with increasing malic acid fluctuation was observed among species averages. This study provides evidence that CO 2 recycling via malic acid is negatively correlated with daytime transpirational water losses in well-watered plants. Thus, CAM-cycling could be important for survival in the thin, frequently desiccated soils of rock outcrops on which these plants occur. 相似文献
5.
Water chemistry and titratable acidity and malic acid levels in Isoetes howellii leaves were sampled every 6 hr from plants in a seasonal pool and an oligotrophic lake. Plants in the seasonal pool showed a diurnal fluctuation of ~ 300 μequivalents titratable acidity g −1 fresh wt; daytime deacidification was 75% complete by noon and nighttime acidification was 45% complete by midnight. Late in the season after the pool had dried, emergent leaves showed only a very weak tendency to accumulate acid at night. Plants from the oligotrophic lake had a diurnal change of ~100 μeq g −1 fresh wt, daytime deacidification was only 45% complete by noon but nighttime acidification was 80 % complete by midnight. Water characteristics were distinctly different between these two systems. In the seasonal pool there were marked diurnal changes in temperature, pH, oxygen and carbon dioxide. Free-CO 2 levels were an order of magnitude greater in the early morning than in the late afternoon. In contrast, the conditions in the oligotrophic lake showed no marked diurnal fluctuation, though total inorganic carbon levels were extremely low relative to other aquatic systems. 相似文献
6.
A comparison of carbon metabolism in the constitutive crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana Hamet et Perr. and the C 3-CAM intermediate Clusia minor L. was undertaken under controlled environmental conditions where plants experience gradual changes in light intensity, temperature and humidity at the start and end of the photoperiod. The magnitude of CAM activity was manipulated by maintaining plants in ambient air or by enclosing leaves overnight in an atmosphere of N 2 to suppress C 4 carboxylation. Measurements of diel changes in carbonisotope discrimination and organic acid content were used to quantify the activities of C 3 and C 4 carboxylases in vivo and to indicate the extent to which the activities of phosphoenolpyruvate carboxylase (PEPCase), ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) and decarboxylation processes overlap at the start and end of the photoperiod. These measurements in vivo were compared with measurements in vitro of changes in the diel sensitivity of PEPCase to malate inhibition. The results demonstrate fundamental differences in the down-regulation of PEPCase during the day in the two species. While PEPCase is inactivated within the first 30 min of the photoperiod in K. daigremontiana, the enzyme is active for 4 h at the start and 3 h at the end of the photoperiod in C. minor. Enclosing leaves in N 2 overnight resulted in a two-to threefold increase in PEPCase-mediated CO 2 uptake during Phase II of CAM in both species. However, futile cycling of CO 2 between malate synthesis and decarboxylation does not occur during Phase II in either species. In terms of overall carbon balance, C 4 carboxylation accounted for ≈ 20% of net daytime assimilation in both species under control conditions, increasing to 30–34% after a night in N 2. Although N 2-treated leaves of K. daigremontiana took up 25% more CO 2 than control leaves during the day this was insufficient to compensate for the loss of CO 2 taken up by CAM the previous night. In contrast, in N 2-treated leaves of C. minor, the twofold increase in daytime PEPCase activity and the increase in net CO 2 uptake by Rubisco during Phase III compensated for the inhibition of C 4 carboxylation at night in terms of diel carbon balance. 相似文献
7.
Abstract The results described represent the first detailed measurements of gas exchange of epiphytic plants with crassulacean acid metabolism (CAM) in the humid tropics. A portable steady-state CO 2 and H 2O porometer was used to measure net exchange rates of CO 2 and H 2O vapour ( JCO2, JH2O), leaf temperature ( T1), air temperature ( TA), air relative humidity (RH) and photosynthetically active radiation (PAR) for bromeliads in the field during the dry season in February and March 1983 on the tropical island of Trinidad. Different lengths of tubing (up to 25 m) were used so that the gas exchange could be measured of bromeliads in situ in their epiphytic habitats. Derived parameters such as leaf-air water-vapour-concentration difference (Δ w), water-vapour conductance of leaves ( g) and internal CO 2 partial pressure ( piCO2) could be calculated. The particular problems of making such measurements in the humid tropics due to high relative humidities and high dew-point temperatures are discussed. The long and often broad, strap-like leaves of bromeliads are well suited for measurements with the steady-state porometer. It is shown that CAM activity varies along the length of individual leaves, and variability between different leaves is also demonstrated. The major phases of CAM, i.e. nocturnal stomalal opening, CO 2 uptake and dark fixation as malic acid (Phase I), daytime stomatal closure and light-dependent assimilation of CO 2 derived from decarboxylation of the malic acid (Phase III), and late-afternoon stomatal opening with direct light-dependent assimilation of atmospheric CO 2 (Phase IV) were all clearly shown by CAM bromeliads in situ. Their expression and magnitude depended on the environmental conditions. An early-morning peak of CO 2 uptake as is characteristic of Phase II of CAM was not detected during the night-day transition. A bromeliad intermediate between C 3 and CAM, Guzmania monostachia, showed substantial net CO 2 uptake in the early morning but no net uptake integrated over the whole of the night. 相似文献
8.
Experiments were conducted to examine the development of photosynthetic carbon metabolism in Peperomia scandens, a tropical epiphyte. Leaves were sampled during a 10-day period when they were between 30 to 165 days old. P. scandens exhibits a C 3 to CAM-cycling to CAM shift during maturation with the magnitude of CAM increasing with age. Initially, during both day and night, no significant CO 2 uptake or diurnal acid flux was evident. C 3 gas exchange was detected at 41 days of age with a gradual shift towards CAM gas exchange maximized thereafter. An acidity flux of 130 to 150 microequivalents per gram fresh weight was evident by 41 days. Between 40 and 90 days, the leaves shifted their CO 2 uptake pattern from a daytime to a nighttime peak. After 90 days, the leaves remained in CAM. The δ 13C values became progressively less negative as the leaves matured. In the 30-day-old leaves, the δ 13C value was −21.1% while in the 165-day-old leaves the δ 13C value was −18.3%. The time-dependent shift from C 3 to CAM-cycling to CAM in P. scandens does not appear to result from changes in water, light, or temperature regimes since these variables were constant for all leaves sampled. 相似文献
9.
The quantum yield of photosynthetic O 2 exchange was measured in eight species of leaf succulents representative of both malic enzyme type and phosphoenolpyruvate carboxykinase type CAM plants. Measurements were made at 25°C and CO 2 saturation using a leaf disc O 2 electrode system, either during or after deacidification. The mean quantum yield was 0.095 ± 0.012 ( sd) moles O 2 per mole quanta, which compared with 0.094 ± 0.006 ( sd) moles O 2 per mole quanta for spinach leaf discs measured under the same conditions. There were no consistent differences in quantum yield between decarboxylation types or during different phases of CAM metabolism. On the basis of current notions of compartmentation of CAM biochemistry, our observations are interpreted to indicate that CO 2 refixation is energetically independent of gluconeogenesis during deacidification. 相似文献
10.
Abstract The paper reports the results of the comprehensive study of crassulacean acid metabolism in two epiphytic tropical ferns, Drymoglossum piloselloides and Pyrrosia longifolia. The plants were investigated under different light, temperature and water status. It was found that both species are obligate CAM plants. The diurnal acidity rhythm is due to the fluctuation in malic acid concentration, which accounts for the change in titratable acidity. Besides malic acid, shikimate and oxalate are found to be present, but not contributing to the CAM acid rhythm. The diurnal rhythm of malic acid content results in a corresponding rhythm in leaf water relations. Both Φ Φ and Φ total, were lowest at the end of the night, i.e. when the level of malic acid was highest. The effects of temperature on CO 2 exchange were inverse to those observed in other CAM plants. In both ferns studied, dark CO 2 fixation increased when the night temperature was increased. Increase in day temperature reduced CO 2 uptake during phase IV and during the following night. The observed responses of the ferns to temperature changes suggest that the in situ environmental conditions are optimal for their CAM performance. In weak light, the plants showed net CO 2 output during the midday deacidification period. Increases in light intensity reduced such CO 2 output. Under drought conditions, the CO 2 exchange in the ferns was reduced to zero within 5–6 d, indicating that the ferns studied are more susceptible to water deficiency than other CAM plants. This could be due to a higher cuticular conductance for water. The results are discussed, in particular, in relation to CAM performance of epiphytes growing in the wet tropics. 相似文献
11.
The labeling patterns in malic acid from dark 13CO 2 fixation in seven species of succulent plants with Crassulacean acid metabolism were analysed by gas chromatography-mass spectrometry and 13C-nuclear magnetic resonance spectrometry. Only singly labeled malic-acid molecules were detected and on the average, after 12–14 h dark 13CO 2 fixation the ratio of [4- 13C] to [1- 13C] label was 2:1. However the 4-C carboxyl contained from 72 to 50% of the label depending on species and temperature. The 13C enrichment of malate and fumarate was similar. These data confirm those of W. Cockburn and A. McAuley (1975, Plant Physiol. 55, 87–89) and indicate fumarase randomization is responsible for movement of label to 1-C malic acid following carboxylation of phosphoenolpyruvate. The extent of randomization may depend on time and on the balance of malic-acid fluxes between mitochondria and vacuoles. The ratio of labeling in 4-C to 1-C of malic acid which accumulated following 13CO 2 fixation in the dark did not change during deacidification in the light and no doubly-labeled molecules of malic acid were detected. These results indicate that further fumarase randomization does not occur in the light, and futile cycling of decarboxylation products of [ 13C] malic acid ( 13CO 2 or [1- 13C]pyruvate) through phosphoenolpyruvate carboxylase does not occur, presumably because malic acid inhibits this enzyme in the light in vivo. Short-term exposure to 13CO 2 in the light after deacidification leads to the synthesis of singly and multiply labeled malic acid in these species, as observed by E.W. Ritz et al. (1986, Planta 167, 284–291). In the shortest times, only singly-labeled [4- 13C]malate was detected but this may be a consequence of the higher intensity and better detection statistics of this ion cluster during mass spectrometry. We conclude that both phosphoenolpyruvate carboxylase (EC 4.1.1.32) and ribulose-1,5-biphosphate carboxylase (EC 4.1.1.39) are active at this time.Abbreviations CAM
Crassulacean acid metabolism
- GCMS
gas chromatography-mass spectrometry
- MS
mass spectrometry
- NMR
nuclear magnetic resonance spectrometry
- PEP
phosphoenolpyruvate
- RuBP
ribulose 1,5-bisphosphate 相似文献
12.
High levels of variability in gas exchange characteristics and degree of CAM-cycling were found in the same and different individuals of Talinum calycinum Engelm. collected from rock outcrops in Missouri. Differences in CO 2 assimilation were mostly correlated with differences in shoot conductance to CO 2 not shoot internal CO 2 concentration. As found previously, CAM acid fluctuations were evident in well-watered plants exhibiting C 3 gas exchange patterns (CAM-cycling) and also in drought-stressed plants with stomata closed, or nearly so, day and night (CAM-idling). Drought stress also resulted in rapid stomatal closure, conserving water during droughts. Maximal CO 2 uptake rates occurred below 35°C; higher temperatures induced decreases in CO 2 assimilation and conductance while shoot internal CO 2 concentrations remained similar. Plant water-use-efficiency was severely curtailed at temperatures above 30°C. Tissue acid fluctuations were the result of changes in malic acid concentrations. Calculations of the amount of water potentially conserved by CAM-cycling yielded values of approximately 5 to 44% of daytime water loss. Thus, CAM-cycling may be an important adaptation minimizing water loss by perennial succulents growing in shallow soil on rock outcrops. 相似文献
13.
Summary In the leaves (but not corms) of the submerged aquatic Isoetes storkii malic acid concentration fluctuated from 22 eg g FW -1 in the evening to 171 eg g FW -1 in the morning. Associated with this was a change in titratable acidity of 152 eg g FW -1 between morning and evening. 14C carbon was fixed in both the light and the dark, though the amount of carbon fixed in the light was more than that fixed in the dark. Autoradiographs show 88% of 14CO 2 fixed in the dark is recovered after 1 h, in malic acid and the remainder in one other unidentified product, whereas these two products contain less than 15% of the 14C fixed after 1 h exposure to 14CO 2 in the light. It is suggested that CAM metabolism in this aquatic species may be related to the low availability of CO 2 for photosynthesis during the day in its aquatic environment and that this metabolic pathway may prove common in the genus Isoetes. 相似文献
14.
The rates of dark CO 2 fixation and the label distribution in malate following dark 14CO 2 fixation in a C-4 plant (maize), a C-3 plant (sunflower), and two Crassulacean acid metabolism plants ( Bryophyllum calycinum and Kalanchoë diagremontianum leaves and plantlets) are compared. Within the first 30 minutes of dark 14CO 2 fixation, leaves of maize, B. calycinum, and sunflower, and K. diagremontianum plantlets fix CO 2 at rates of 1.4, 3.4, 0.23, and 1.0 μmoles of CO 2/mg of chlorophyll· hour, respectively. Net CO 2 fixation stops within 3 hours in maize and sunflower, but Crassulaceans continue fixing CO 2 for the duration of the 23-hour experiment. A bacterial procedure using Lactobacillus plantarum ATCC No. 8014 and one using malic enzyme to remove the β-carboxyl (C4) from malate are compared. It is reported that highly purified malic enzyme and the bacterial method provide equivalent results. Less purified malic enzyme may overestimate the label in C4 as much as 15 to 20%. The contribution of carbon atom 1 of malate is between 18 and 21% of the total carboxyl label after 1 minute of dark CO2 fixation. Isotopic labeling in the two carboxyls approached unity with time. The rate of increase is greatest in sunflower leaves and Kalanchoë plantlets. In addition, Kalanchoë leaves fix 14CO2 more rapidly than Kalanchoë plantlets and the equilibration of the malate carboxyls occurs more slowly. The rates of fixation and the randomization are tissue-specific. The rate of fixation does not correlate with the rate of randomization of isotope in the malate carboxyls. 相似文献
15.
The kinetics of chlorophyll fluorescence were measured in Portulacaria afra (L.) Jacq. when the plants were functioning in either Crassulacean acid metabolism (CAM) or C 3/CAM cycling (called cycling) modes, as determined by fluctuation in titratable acidity and gas exchange properties. Cycling plants showed primarily daytime CO 2 uptake typical of C 3 plants, but with a slight diurnal acid fluctuation, whereas CAM plants showed nocturnal CO 2 uptake, daytime stomatal closure, and a large diurnal acid fluctuation. Results from fluorescence measurements indicated no significant differences in photochemical quenching between cycling and CAM plants; however, sizable differences were detected in nonphoto-chemical quenching (q n), with the largest differences being observed during the middle of the day. Cycling plants had lower q n than CAM plants, indicating altered photosynthetic regulation processes. This q n difference was believed to be related to reduced internal CO 2 concentration in the CAM plants because of daytime stomatal closure and reduced deacidification rates in the late afternoon when most of the malic acid has been utilized. Experimentally, higher external CO 2 given to plants in the CAM mode resulted in a decline in q n in comparison to that measured in plants in the cycling mode. No changes were observed in photochemical quenching when CO 2 was added. 相似文献
16.
In the aquatic CAM species Isoetes bolanderi, a resident of high elevation lakes in which ambient carbon levels are low and fairly constant throughout the day, CO 2 uptake by the leaves generally parallels changes in photosynthetic photon flux density as opposed to changes in ambient CO 2 levels. Overnight CO 2 uptake by the leaves of I. bolanderi contributed up to 33% of the total daily carbon assimilation from the water column which is typical of aquatic CAM species but low in comparison to the 30–50% seen in the seasonal pool congener Isoetes howellii. Two additional sources of carbon may supplement the 24-hour period for carbon assimilation conferred by CAM in I. bolanderi: the refixation of respiratory CO 2 and carbon acquisition from the interstitial sediment water via roots. CAM appears to play a significant role in enhancing carbon gain in I. bolanderi which dominates the littoral flora of Siesta and Ellery Lakes despite higher carbon uptake rates from the water column found in one associated macrophyte Fontinalis antipyretica. 相似文献
17.
The relationship between stomatal conductance and capacity for assimilation was investigated in flacca, a mutant of tomato ( Lycopersicon esculentum Mill.) that has abnormal stomatal behavior and low abscisic acid (ABA) content. The assimilation capacity, determined by measuring assimilation rate as a function of intercellular CO 2 pressure, did not differ in leaves of flacca and its parent variety, Rheinlands Ruhm (RR). On the other hand, stomatal conductance of flacca leaves was greater than that of RR, and could be phenotypically reverted by spraying with 30 micromolar ABA. Stomatal conductance of flacca leaves was also reduced by increasing CO 2 pressure, increasing leaf to air vapor pressure difference, and decreasing quantum flux, irrespective of ABA treatment. The high conductance of flacca leaves resulted in a high intercellular CO2 pressure. This allowed greater discrimination against 13CO2, as evidenced by more negative δ 13C values for flacca as compared to RR. The δ 13C values of both flacca and RR plants as influenced by ABA treatment were consistent with predictions based on gas exchange measurements, using a recent model of discrimination. 相似文献
18.
Dynamic patchiness of photosystem II (PSII) activity in leaves of the crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana Hamet et Perrier, which was independent of stomatal control and was observed during both the day/night cycle and circadian endogenous oscillations of CAM, was previously explained by lateral CO 2 diffusion and CO 2 signalling in the leaves [Rascher et al. ( 2001) Proc Natl Acad Sci USA 98:11801–11805; Rascher and Lüttge ( 2002) Plant Biol 4:671–681]. The aim here was to actually demonstrate the importance of lateral CO 2 diffusion and its effects on localized PSII activity. Covering small sections of entire leaves with silicone grease was used for local exclusion of a contribution of atmospheric CO 2 to internal CO 2 via transport through stomata. A setup for combined measurement of gas exchange and chlorophyll fluorescence imaging was used for recording photosynthetic activity with a spatiotemporal resolution. When remobilization of malic acid from vacuolar storage and its decarboxylation in the CAM cycle caused increasing internal CO 2 concentrations sustaining high PSII activity behind closed stomata, PSII activity was also increased in adjacent leaf sections where vacuolar malic acid accumulation was minimal as a result of preventing external CO 2 supply due to leaf-surface greasing, and where therefore CO 2 could only be supplied by diffusion from the neighbouring malic acid-remobilizing leaf tissue. This demonstrates lateral CO 2 diffusion and its effect on local photosynthetic activity. 相似文献
19.
Phaseolus vulgaris L. leaves were subjected to various light, CO 2, and O 2 levels and abscisic acid, then given a 10 minute pulse of 14CO 2 followed by a 5 minute chase with unlabeled CO 2. After the chase period, very little label remained in the ionic fractions (presumed to be mostly carbon reduction and carbon oxidation cycle intermediates and amino acids) except at low CO 2 partial pressure. Most label was found in the neutral, alcohol soluble fraction (presumed sucrose) or in the insoluble fraction digestable by amyloglucosidase. Sucrose formation was linearly related to assimilation rate (slope = 0.35). Starch formation increased linearly with assimilation rate (slope = 0.56) but did not occur if the assimilation rate was below 4 micromoles per square meter per second. Neither abscisic acid, nor high CO 2 in combination with low O 2 (thought to disrupt control of carbon metabolism) caused significant perturbations of the sucrose/starch formation ratio. These studies indicate that the pathways for starch and sucrose synthesis both are controlled by the rate of net CO 2 assimilation, with sucrose the preferred product at very low assimilation rates. 相似文献
20.
Summary CO 2 exchange, the diurnal variations in the levels of malic, citric and isocitric acid, and the labelling pattern after 14CO 2 fixation were measured in Sedum acre and Sedum mite growing in situ. As predicted from laboratory experiments, drought changed the gas exchange pattern from a C 3 type to a crassulacean acid metabolism (CAM) type. This shift correlated with the development of a diurnal rhythm in the malic acid content. The results of 14CO 2 pulse-chase experiments suggest that in well-watered plants a CAM pattern of carbon flow already exists; hence water stress might enhance latent CAM rather than induce it. The in situ CAM performance by the Sedum species appeared to be highly susceptible to modulation by season and external factors, particularly light and temperature.CAM did not substantially contribute to total carbon gain in S. acre and S. mite. During most of their lifecycles the plants grow under conditions that favour CO 2 uptake by the C 3 pathway rather than by CAM. Hence, despite a capability to feature CAM, the 13C values found in S. acre and S. mite are those of C 3 plants.Abbreviations CAM
Crassulacean Acid Metabolism
- PEP-C
Phosphoenolpyruvate-Carboxylase
- DW
Dry weight
Dedicated to Prof. Dr. Dr. h.c. M. Evenari on the occasion of his 75th birthday and to Dr. K.F. Springer 相似文献
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