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1.
Leaf carbon isotope ratios (δ13C) and photosynthetic gas exchange were measured on plants growing in hanging garden communities in southern Utah, USA. Hanging
gardens are unusual, mesic cliff communities occurring where water seeps from the sandstone bedrock in an otherwise extremely
arid region; there is very limited overlap in species distributions inside and outside these gardens. Solar exposure in hanging
gardens varied with orientation and one of the gardens (Ribbon Garden) was shaded throughout the day. The leaf δ13C values of plants in hanging gardens were significantly more negative than for plants from either nearby ephemeral wash or
riparian communities. In Ribbon Garden, the observed δ13C values were as low as −34.8‰, placing them among the most negative values reported for any terrestrial plant species growing
in a natural environment. Hanging garden plants were exposed to normal atmospheric CO2 with an average δ13C value of −7.9‰ and so the low leaf δ13C values could not be attributed to exposure to a CO2 source with low 13C content. There was a seasonal change toward more negative leaf δ13C values at the end of the growing season. The observed leaf δ13C values were consistent with photosynthetic gas exchange measurements that indicated unusually high leaf intercellular CO2 concentrations associated with the relatively low light levels in hanging gardens. Thus, extremely negative leaf δ13C values would be expected if significant amounts of the seasonal carbon gain occur at light levels low enough to be near
the light compensation point. Maximum observed photosynthetic rates varied with light levels at each of the gardens, with
maximum rates averaging 20.3, 14.6, and 3.1 μmol m−2 s−1 at Double Garden, Lost Garden, and Ribbon Garden, respectively. Leaf nitrogen contents averaged 18.5 mg g−1 in species from the more shaded hanging gardens (Lost and Ribbon). When expressed on a leaf area basis, nitrogen contents
averaged 117 mmol N m−2 at Lost Garden and 65 mmol N m−2 at Ribbon Garden (shadiest of the two gardens). Leaf nitrogen isotope ratios averaged −2.3‰ (range of −0.7 to −6.1‰), suggesting
that most of the nitrogen was derived from a biological fixation source which is most likely the Nostoc growing on the sandstone walls at the seep. These values contrast with leaf nitrogen isotope ratios of 5–9‰ which have been
previously reported for arid zone plants in nearby ecosystems.
Received: 19 January 1997 / Accepted: 19 April 1997 相似文献
2.
Leaf photosynthesis, plant growth and nitrogen allocation in rice under different irradiances 总被引:6,自引:0,他引:6
The photosynthetic rates and various components of photosynthesis including ribulose-1,5-bisphosphate carboxylase (Rubisco;
EC 4.1.1.39), chlorophyll (Chl), cytochrome (Cyt) f, and coupling factor 1 (CF1) contents, and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity were examined in young, fully expanded leaves of rice
(Oryza sativa L.) grown hydroponically under two irradiances, namely, 1000 and 350 μmol quanta · m−2 · s−1, at three N concentrations. The light-saturated rate of photosynthesis measured at 1800 μmol · m−2 · s−1 was almost the same for a given leaf N content irrespective of growth irradiance. Similarly, Rubisco content and SPS activity
were not different for the same leaf N content between irradiance treatments. In contrast, Chl content was significantly greater
in the plants grown at 350 μmol · m−2 · s−1, whereas Cyt f and CF1 contents tended to be slightly smaller. However, these changes were not substantial, as shown by the fact that the light-limited
rate of photosynthesis measured at 350 μmol · m−2 · s−1 was the same or only a little higher in the plants grown at 350 μmol · m−2 · s−1 and that CO2-saturated photosynthesis did not differ between irradiance treatments. These results indicate that growth-irradiance-dependent
changes in N partitioning in a leaf were far from optimal with respect to N-use efficiency of photosynthesis. In spite of
the difference in growth irradiance, the relative growth rate of the whole plant did not differ between the treatments because
there was an increase in the leaf area ratio in the low-irradiance-grown plants. This increase was associated with the preferential
N-investment in leaf blades and the extremely low accumulation of starch and sucrose in leaf blades and sheaths, allowing
a more efficient use of the fixed carbon. Thus, morphogenic responses at the whole-plant level may be more important for plants
as an adaptation strategy to light environments than a response of N partitioning at the level of a single leaf.
Received: 23 February 1997 / Accepted: 8 May 1997 相似文献
3.
To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending
on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 μmol m−2 s−1) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a
control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 μmol m−2 s−1. The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 μmol m−2 s−1 and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300–1600 μmol m−2 s−1). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite
content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase
and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 μmol m−2 s−1 or in the glasshouse than in plants grown at 330 μmol m−2 s−1. Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar
under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 μmol m−2 s−1 can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate.
This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase
and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate.
This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.
Received: 15 November 1999 / Accepted: 27 January 2000 相似文献
4.
Submerged aquatic higher plants maintain acropetal water transport to the young leaves in active growth to satisfy their
demand for nutrients and hormones derived from the roots. We here present the first measurements of hydraulic properties for
a submerged plant, the monocotyledon Sparganium emersum Rehman. The hydraulic conductance per unit length, Kh, was measured in leaf segments without the leaf tip and shown to be greater in old, fully developed leaves (1.5 · 10−10 · m4 · MPa−1 · s−1) than in young leaves (1.0 · 10−10 · m4 · MPa−1 · s−1). In leaves with intact leaf tips, however, Kh was significantly greater in the youngest leaves, which suggests that the leaf tip with the hydathode influences resistance
and thus flow. Microscopy confirmed that the hydathodal area, which is an apical opening, undergoes structural changes with
leaf age; a matrix of microorganisms develops in the older leaves and probably restricts water flow by clogging the hydathodes.
The leaf specific conductivity expressing transport capacity relative to the leaf area supplied, of S. emersum (0.1 · 10−8 to 9 · 10−8 · m2 MPa−1· s−1) was within the same range as for various species of terrestrial ferns, vines and trees. This finding does not support the
traditional concept of functionally reduced vascular transport in
Received: 15 July 1996 / Accepted: 30 November 1996 相似文献
5.
Gas-exchange measurements were performed to analyze the leaf conductances and assimilation rates of potato (Solanum tuberosum L. cv. Desireé) plants expressing an antisense construct against chloroplastic fructose-1,6-bisphosphatase (FBPase, EC 3.1.3.11)
in response to increasing photon flux densities, different relative air humidities and elevated CO2 concentrations. Assimilation rates (A) and transpiration rates (E) were observed during a stepwise increase of photon flux
density. These experiments were carried out under atmospheric conditions and in air containing 500 μmol mol−1 CO2. In both gas atmospheres, two levels of relative air humidity (60–70% and 70–80%) were applied in different sets of measurements.
Intercellular CO2 concentration, leaf conductance, air-to-leaf vapour pressure deficit, and instantaneous water-use efficiency (A/E) were determined.
As expected, assimilation rates of the FBPase antisense plants were significantly reduced as compared to the wild type. Saturation
of assimilation rates in transgenic plants occurred at a photon flux density of 200 μmol m−2 s−1, whereas saturation in wild type plants was observed at 600 μmol m−2 s−1. Elevated ambient CO2 levels did not effect assimilation rates of transgenic plants. At 70–80% relative humidity and atmospheric CO2 concentration the FBPase antisense plants had significantly higher leaf conductances than wild-type plants while no difference
emerged at 60–70%. These differences in leaf conductance vanished at elevated levels of ambient CO2. Stomatal response to different relative air humidities was not affected by mesophyll photosynthetic activity. It is suggested
that the regulation of stomatal opening upon changes in photon flux density is merely mediated by a signal transmitted from
mesophyll cells, whereas the intercellular CO2 concentration plays a minor role in this kind of stomatal response. The results are discussed with respect to stomatal control
by environmental parameters and mesophyll photosynthesis.
Received: 24 September 1998 / Accepted: 9 February 1999 相似文献
6.
Lolium temulentum L. Ba 3081 was grown hydroponically in air (350 μmol mol−1 CO2) and elevated CO2 (700 μmol mol−1 CO2) at two irradiances (150 and 500 μmol m−2 s−1) for 35 days at which point the plants were harvested. Elevated CO2 did not modify relative growth rate or biomass at either irradiance. Foliar carbon-to-nitrogen ratios were decreased at elevated
CO2 and plants had a greater number of shorter tillers, particularly at the lower growth irradiance. Both light-limited and light-saturated
rates of photosynthesis were stimulated. The amount of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) protein was
increased at elevated CO2, but maximum extractable Rubisco activities were not significantly increased. A pronounced decrease in the Rubisco activation
state was found with CO2 enrichment, particularly at the higher growth irradiance. Elevated-CO2-induced changes in leaf carbohydrate composition were small in comparison to those caused by changes in irradiance. No CO2-dependent effects on fructan biosynthesis were observed. Leaf respiration rates were increased by 68% in plants grown with
CO2 enrichment and low light. We conclude that high CO2 will only result in increased biomass if total light input favourably increases the photosynthesis-to-respiration ratio.
At low irradiances, biomass is more limited by increased rates of respiration than by CO2-induced enhancement of photosynthesis.
Received: 23 February 1999 / Accepted: 15 June 1999 相似文献
7.
The role of gibberellins (GAs) in the regulation of shoot elongation is well established but the phytohormonal control of
dry-matter production is poorly understood. In the present study, shoot elongation and dry-matter production were resolved
by growing Brassica napus L. seedlings under five light intensities (photon flux densities) ranging from 25 to 500 μmol m−2 s−1. Under low light, plants were tall but produced little dry weight; as light intensity was increased, plants were progressively
shorter but had increasing dry weights. Endogenous GAs in stems of 16- and 17-d-old plants were analyzed by gas chromatography-selected
ion monitoring with [2H2] internal standards. The contents of GAs increased dramatically with decreasing light intensity: GA1, GA3, GA8 and GA20 were 62, 15, 16 and 32 times higher, respectively, under the lowest versus highest light intensities. Gibberellin A19 was not measured at 25 μmol m−2 s−1 but was 9␣times greater in the 75 compared to 500 μmol m−2 s−1 treatment. Shoot and hypocotyl lengths were closely positively correlated with (log) GA concentration (for example: r
2 = 0.93 for GA1 and hypocotyl length) but shoot dry matter was negatively correlated with GA concentration. The application of gibberellic
acid (GA3) produced elongation of plants grown under high light, indication that their low level of endogenous GA was limiting shoot
elongation. Although endogenous GA20 showed the greatest influence of light treatment, metabolism of [3H]GA20 and of [3H]GA1 was only slightly influenced by light intensity, suggesting that neither 2β- nor 3β-hydroxylation were points of metabolic
regulation. The results of this study indicate that GAs control shoot elongation but are not directly involved in the regulation
of shoot dry weight in Brassica. The study also suggests a role of GAs in photomorphogenesis, serving as an intermediate between light condition and shoot
elongation response.
Received: 18 June 1998 / Accepted: 29 July 1998 相似文献
8.
Leaf carbon isotope discrimination (Δ13C) varies with the balance between net photosynthesis (A) and stomatal conductance (g
s
). Inferences that can be made with Δ13C are limited, as changes could reflect variation in A and/or g
s
. Investigators have suggested that leaf δ18O enrichment above source water (Δ18O) may enable differentiation between sources of variation in Δ13C, as leaf Δ18O varies with transpiration rate (E), which is closely correlated with g
s
when leaves experience similar leaf to air vapor pressure differences. We examined leaf gas exchange of Salix arctica at eight sites with similar air temperatures and relative humidities but divergent soil temperatures and soil water contents
near Pituffik, Greenland (76°N, 38°W). We found negative correlations at the site level between g
s
and Δ18O in bulk leaf tissue (r
2 = 0.62, slope = −17.9‰/mol H2O m−2 s−1, P = 0.02) and leaf α-cellulose (r
2 = 0.83, slope = −11.5‰ mol H2O m−2 s−1, P < 0.01), consistent with the notion that leaf water enrichment declines with increasing E. We also found negative correlations at the site-level between intrinsic water-use efficiency (iWUE) and Δ13C in bulk leaf tissue (r
2 = 0.65, slope = −0.08‰/μmol CO2 /mol H2O, P = 0.02) and leaf α-cellulose (r
2 = 0.50, slope = −0.05 ‰/[μmol CO2 /mol H2O], P = 0.05). When increasing Δ13C was driven by increasing g
s
alone, we found negative slopes between Δ13C and Δ18O for bulk leaf tissue (−0.664) and leaf α-cellulose (−1.135). When both g
s
and A
max increased, we found steeper negative slopes between Δ13C and Δ18O for bulk leaf tissue (−2.307) and leaf α-cellulose (−1.296). Our results suggest that the dual isotope approach is capable
of revealing the qualitative contributions of g
s
and A
max to Δ13C at the site level. In our study, bulk leaf tissue was a better medium than leaf α-cellulose for application of the dual
isotope approach. 相似文献
9.
Microstegium vimineum (Trin.) A. Camus, a shade-tolerant C4 grass, has spread throughout the eastern United States since its introduction in 1919. This species invades disturbed understory
habitats along streambanks and surrounding mesic forests, and has become a major pest in areas such as Great Smoky Mountains
National Park. The focus of this study was to characterize the photosynthetic induction responses of M. vimineum, specifically its ability to utilize low light and sunflecks, two factors that may be critical to invasive abilities and
survival in the understory. In addition, we were curious about the ability of a grass with the C4 photosynthetic pathway to respond to sunflecks. Plants were grown under 25% and 50% ambient sunlight, and photosynthetic
responses to both steady-state and variable light were determined. Plants grown in both 25% and 50% ambient sun became 90%
light saturated between 750–850 μmol m−2 s−1; however, plants grown in 50% ambient sun had significantly higher maximum steady-state photosynthetic rates (16.09 ± 1.37 μmol m−2 s−1 vs. 12.71 ± 1.18 μmol m−2 s−1). Both groups of plants induced to 50% of the steady-state rate in 3–5 min, while it took 10–13 min to reach 90% of maximum
rates, under both flashing and steady-state light. For both groups of plants, stomatal conductance during induction reached
maximum rates in 6–7 min, after which rates decreased slightly. Upon return to low light, rates of induction loss and stomatal
closure were very rapid in both groups of plants, but were more rapid in those grown in high light. Rapid induction and the
ability to induce under flashing light may enable this species to invade and dominate mesic understory habitats, while rapid
induction loss due to stomatal closure may prevent excess water loss when low light constrains photosynthesis. The C4 pathway itself does not appear to present an insurmountable barrier to the ability of this grass species to respond to sunflecks
in an understory environment.
Received: 21 February 1997 / Accepted: 10 October 1997 相似文献
10.
The concept of using higher plants to maintain a sustainable life support system for humans during long-duration space missions is dependent upon photosynthesis. The effects of extended exposure to microgravity on the development and functioning of photosynthesis at the leaf and stand levels were examined onboard the International Space Station (ISS). The PESTO (Photosynthesis Experiment Systems Testing and Operations) experiment was the first long-term replicated test to obtain direct measurements of canopy photosynthesis from space under well-controlled conditions. The PESTO experiment consisted of a series of 21–24 day growth cycles of Triticum aestivum L. cv. USU Apogee onboard ISS. Single leaf measurements showed no differences in photosynthetic activity at the moderate (up to 600 μmol m−2 s−1) light levels, but reductions in whole chain electron transport, PSII, and PSI activities were measured under saturating light (>2,000 μmol m−2 s−1) and CO2 (4000 μmol mol−1) conditions in the microgravity-grown plants. Canopy level photosynthetic rates of plants developing in microgravity at ∼280 μmol m−2 s−1 were not different from ground controls. The wheat canopy had apparently adapted to the microgravity environment since the CO2 compensation (121 vs. 118 μmol mol−1) and PPF compensation (85 vs. 81 μmol m−2 s−1) of the flight and ground treatments were similar. The reduction in whole chain electron transport (13%), PSII (13%), and PSI (16%) activities observed under saturating light conditions suggests that microgravity-induced responses at the canopy level may occur at higher PPF intensity. 相似文献
11.
S. Sánchez V. Bravo E. Castro A. J. Moya F. Camacho 《Applied microbiology and biotechnology》1998,50(5):608-611
We have analysed the influence of the initial pH of the medium and the quantity of aeration provided during the batch fermentation
of solutions of d-xylose by the yeast Hansenula polymorpha (34438 ATCC). The initial pH was altered between 3.5 and 6.5 whilst aeration varied between 0.0 and 0.3 vvm. The temperature
was kept at 30 °C during all the experiments. Hansenula polymorpha is known to produce high quantities of xylitol and low quantities of ethanol. The most favourable conditions for the growth
of xylitol turned out to be: an initial pH of between 4.5 and 5.5 and the aeration provided by the stirring vortex alone.
Thus, at an initial pH of 5.5, the maximum specific production rate (μm) was 0.41 h−1, the overall biomass yield (Y
x/s
G) was 0.12 g g−1, the specific d-xylose-consumption rate (q
s
) was 0.075 g g−1 h−1 (for t = 75 h), the specific xylitol-production rate (q
Xy
) was 0.31 g g−1 h−1 (for t = 30 h) and the overall yields of ethanol (Y
E/s
G) and xylitol (Y
Xy/s
G) were 0.017 and 0.61 g g−1 respectively. Both q
s
and q
Xy
decreased during the course of the experiments once the exponential growth phase had finished.
Received: 26 March 1998 / Received revision: 30 June 1998 / Accepted: 2 July 1998 相似文献
12.
In three tropical rain forest light environments in Sabah, Malaysia, we compared photosynthesis in seedlings of ten climax
tree species with putatively differing shade tolerances. The objectives of the study were (a) to characterise the range of
photosynthetic responses in ten species of the Dipterocarpaceae and (b) to elucidate those photosynthetic characteristics
that might provide a basis for niche partitioning. Seedlings were acclimated (c. 7 months) in three light environments; understorey, partial shade and a gap (140 m2). The light environments represented a gradation in median diurnal (0630–1830 hours) photon flux density (PFD) ranging from
understorey (4.7 μmol m−2 s−1), through partial shade (21.2 μmol m−2 s−1) to gap (113.7 μmol m−2 s−1). Integrated diurnal PFD were in the sequence gap > partial shade > understorey (15.2, 4.7, 1.3 mol m−2 day−1, respectively). In gap-acclimated plants, species differed in the photosynthetic light-response variables apparent quantum
yield, dark respiration rate, light compensation point, net saturated leaf assimilation rate (A
sat), and in stomatal conductance (g
s sat) when assimilation rate (A) was saturated. A light-demanding pioneer species (Macaranga hypoleuca) and a shade-demanding understorey species (Begonia sp.) had, respectively, higher and lower A
sat and g
s sat than the dipterocarp species. In high-light conditions A
sat and g
s sat were strongly positively correlated in dipterocarp species. Differing photosynthetic characteristics of gap-acclimated plants
suggest that, in these dipterocarp species, different rates of carbon fixation may be an important factor contributing towards
niche partitioning. Mean integrated diurnal A (A
diurnal) in the gap, partial shade and understory were, respectively, 122.9, 52.7, 20.5 mmol m−2 day−1. Differences occurred in A
diurnal of dipterocarp species between light environments. When Macaranga was included, differences in A
diurnal were evident in the gap and partial shade, and in both cases were attributed to the pioneer. For the variable A
diurnal, there was of a shift in the rank position of Macaranga among light environments, but a shift did not occur among the dipterocarp species. Results from this study are consistent
with the idea that rates of carbon fixation per unit leaf area may contribute towards niche differentiation between the climax
and single pioneer species, but not within the group of climax species. Other physiological and/or carbon allocation factors
may be involved in any niche partitioning; dipterocarp species often have inherently different growth rates and susceptibility
to herbivory. As an alternative to niche partitioning, dipterocarp species may co-exist in natural light environments as a
result of habitat disequilibrium or purely stochastic processes.
Received: 2 April 1997 / Accepted: 13 July 1997 相似文献
13.
L. Guglielmo G. C. Carrada G. Catalano A. Dell'Anno M. Fabiano L. Lazzara O. Mangoni A. Pusceddu V. Saggiomo 《Polar Biology》2000,23(2):137-146
Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S,
164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes
of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were
studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition,
microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in
relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values
of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to
35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations
in the intact sea ice ranged from 0.5 to 2.3 mg l−1 and 0.2 to 2.0 mg l−1, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic
activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l−1 h−1 ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By
contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was
converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom
layer was high, increasing during the sampling period from 680 to 2480 μg l−1. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities.
The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P
B
max
of 0.12 mgC mg Chl−1 and low photoadaptation index (E
k=18 μE m−2 s−1, E
m=65 μE m−2 s−1). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m−2 s−1. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms.
Accepted: 4 August 1999 相似文献
14.
CO2 exchange of the endolithic lichen Verrucaria baldensis was measured in the laboratory under different conditions of water content, temperature, light, and CO2 concentration. The species had low CO2 exchange rates (maximum net photosynthesis: c. 0.45 μmol CO2 m−2 s−1; maximum dark respiration: c. 0.3 μmol CO2 m−2 s−1) and a very low light compensation point (7 μmol photons m−2 s−1 at 8°C). The net photosynthesis/respiration quotient reached a maximum at 9–15°C. Photosynthetic activity was affected only
after very severe desiccation, when high resaturation respiratory rates were measured. Microclimatic data were recorded under
different weather conditions in an abyss of the Trieste Karst (northeast Italy), where the species was particularly abundant.
Low photosynthetically active radiation (normally below 40 μmol photons m−2 s−1), very high humidities (over 80%), and low, constant temperatures were measured. Thallus water contents sufficient for CO2 assimilation were often measured in the absence of condensation phenomena.
Received: 22 September 1996 / Accepted: 26 April 1997 相似文献
15.
J. M. Guehl A. M. Domenach M. Bereau T. S. Barigah H. Casabianca A. Ferhi J. Garbaye 《Oecologia》1998,116(3):316-330
Functional aspects of biodiversity were investigated in a lowland tropical rainforest in French Guyana (5°2′N, annual precipitation
2200 mm). We assessed leaf δ15N as a presumptive indicator of symbiotic N2 fixation, and leaf and wood cellulose δ13C as an indicator of leaf intrinsic water-use efficiency (CO2 assimilation rate/leaf conductance for water vapour) in dominant trees of 21 species selected for their representativeness
in the forest cover, their ecological strategy (pioneers or late successional stage species, shade tolerance) or their potential
ability for N2 fixation. Similar measurements were made in trees of native species growing in a nearby plantation after severe perturbation
(clear cutting, mechanical soil disturbance). Bulk soil δ15N was spatially quite uniform in the forest (range 3–5‰), whereas average leaf δ15N ranged from −0.3‰ to 3.5‰ in the different species. Three species only, Diplotropis purpurea, Recordoxylon speciosum (Fabaceae), and Sclerolobium melinonii (Caesalpiniaceae), had root bacterial nodules, which was also associated with leaf N concentrations higher than 20 mg g−1. Although nodulated trees displayed significantly lower leaf δ15N values than non-nodulated trees, leaf δ15N did not prove a straightforward indicator of symbiotic fixation, since there was a clear overlap of δ15N values for nodulated and non-nodulated species at the lower end of the δ15N range. Perturbation did not markedly affect the difference δ15Nsoil − δ15Nleaf, and thus the isotopic data provide no evidence of an alteration in the different N acquisition patterns. Extremely large
interspecific differences in sunlit leaf δ13C were observed in the forest (average values from −31.4 to −26.7‰), corresponding to intrinsic water-use efficiencies (ratio
CO2 assimilation rate/leaf conductance for water vapour) varying over a threefold range. Wood cellulose δ13C was positively related to total leaf δ13C, the former values being 2–3‰ higher than the latter ones. Leaf δ13C was not related to leaf δ15N at either intraspecific or interspecific levels. δ13C of sunlit leaves was highest in shade hemitolerant emergent species and was lower in heliophilic, but also in shade-tolerant
species. For a given species, leaf δ13C did not differ between the pristine forest and the disturbed plantation conditions. Our results are not in accord with the
concept of existence of functional types of species characterized by common suites of traits underlying niche differentiation;
rather, they support the hypothesis that each trait leads to a separate grouping of species.
Received: 18 August 1997 / Accepted: 14 April 1998 相似文献
16.
Carlos Eduardo Aragón Maritza Escalona Roberto Rodriguez Maria Jesús Cañal Iris Capote Danilo Pina Justo González-Olmedo 《In vitro cellular & developmental biology. Plant》2010,46(1):89-94
In vitro physiology and carbon metabolism can be affected by the sink–source relationship. The effect of different sucrose concentrations
(10, 30, and 50 g L−1), light intensities (80 and 150 μmol m−2 s−1), and CO2 levels (375 and 1,200 μmol mol−1) were tested during plantain micropropagation in temporary immersion bioreactors. Activities of pyruvate kinase, phosphoenol
pyruvate carboxylase, and the photosynthesis rate were recorded. From the morphological and practical point of view, the best
results were obtained when plants were cultured with 30 g L−1 sucrose, 80 μmol m−2 s−1 light intensity, and 1,200 μmol mol−1 CO2 concentration. This treatment improved leaf and root development, reduced respiration during in vitro culture, and increased starch level at the end of the hardening phase. In addition to that, the number of competent plants
was increased from 80.0% to 91.0% at the end of the in vitro phase and the survival percentage from 95.71% to 99.80% during ex vitro hardening. 相似文献
17.
P. L. Sáez L. A. Bravo K. L. Sáez M. Sánchez-Olate M. I. Latsague D. G. Ríos 《Biologia Plantarum》2012,56(1):15-24
The anatomic and functional leaf characteristics related to photosynthetic performance of Castanea sativa growing in vitro and in nursery were compared. The irradiance saturated photosynthesis in in vitro grown plantlets was significantly lower compared to nursery plants (65 vs. 722 μmol m−2 s−1). The maximum photosynthetic rate (PNmax) was 4.0 and 10.0 μmol(CO2) m−2 s−1 in in vitro microshoots and nursery plant leaves, respectively. Carboxylation efficiency (CE) and electron transport rate (ETR) were three-folds higher in nursery plants than in microshoots. The nonphotochemical quenching
(NPQ) was saturated at 80 μmol m−2 s−1 in microshoots suggesting limited photoprotection by thermal dissipation. The microshoots had wide open, spherical stomata
and higher stomatal density than nursery plants and they had almost no epicuticular wax. Consequently, the microshoots had
high stomatal conductance and high transpiration rate. These anatomic and functional leaf characteristics are likely major
causes of the low survival rates of plantlets after ex vitro transfer. 相似文献
18.
A simple procedure is described for the fabrication of micrometer to nanometer-scale platinum electrodes to be used in a
vibrating oxygen-selective system. The electrode was prepared by etching a fine platinum wire and insulating it with an electrophoretic
paint. The dimensions allowed this electrode to be used with the “vibrating probe technique” in exploratory studies aimed
at mapping and measuring the patterns of net influxes as well as effluxes of oxygen in Olea europaea L. leaves and roots with spatial and temporal resolutions of a few microns and a few seconds, respectively. The magnitude
and spatial localisation of O2 influxes in roots was characterised by two distinct peaks. The first, in the division zone, averaged 38 ± 5 nmol m−2 s−1; the second, in the elongation region, averaged 68 ± 6 nmol m−2 s−1. Long-term records of oxygen influx in the elongation region of the root showed an oscillatory regime characterised by a
fast oscillation with periods of about 8–9 min. In leaves, the system allowed the measurement of real-time changes in O2 evolution following changes in light. Furthermore, it was possible to obtain “topographical” images of the photosynthetically
generated oxygen diffusing through different stomata from a region of the leaf of 120 μm × 120 μm. The combination of topographic
and electrochemical information at the micrometer scale makes the system an efficient tool for studying biological phenomena
involving oxygen diffusion.
Received: 12 November 1999 / Accepted: 1 February 2000 相似文献
19.
The vertical profile of stable carbon isotope ratios (δ13C) of leaves was analyzed for 13 tree species in a cool-temperate deciduous forest in Japan. The vertical distribution of
long-term averaged δ13C in atmospheric CO2 (δa) was estimated from δ13C of dry matter from NADP-malic enzyme type C4 plant (Zea mays L. var. saccharata Sturt.) grown at a tower in the forest for 32␣days, assuming constant Δ value (3.3‰) in Z. mays against height. The δa value obtained from δ13C in Z.␣mays was lowest at the forest floor (−9.30 ± 0.03‰), increased with height, and was almost constant above 10␣m (−7.14 ± 0.14‰).
Then leaf Δ values for the tree species were calculated from tree leaf δ13 C andδa. Mean leaf Δ values for the three tall deciduous species (Fraxinus mandshurica, Ulmus davidiana, and Alnus hirsuta) were significantly different among three height levels in the forest: 23.1 ± 0.7‰ at the forest floor (understory), 21.4 ± 0.5‰
in lower canopy, and 20.5 ± 0.3‰ in upper canopy. The true difference in tree leaf Δ among the forest height levels might
be even greater, because Δ in Z. mays probably increased with shading by up to ∼‰. The difference in tree leaf Δ among the forest height levels would be mainly
due to decreasing intercellular CO2 (C
i) with the increase in irradiance. Potential assimilation rate for the three tree species probably increased with height,
since leaf nitrogen content on an area basis for these species also increased with height. However, the increase in stomatal
conductance for these tree species would fail to meet the increase in potential assimilation rate, which might lead to increasing
the degree of stomatal limitation in photosynthesis with height.
Received: 30 September 1995 / Accepted: 25 October 1996 相似文献
20.
Water availability is an important factor limiting the productivity of desert plants but little is known about the impact
of water-limiting conditions on the physiology of plants in mesic environments. Riparian ecosystems of the western US receive
significantly more water than the surrounding desert environments but experience dramatic interannual fluctuations in water
availability because both stream flow and precipitation are highly variable over time. This variability results in different
growing conditions each year which may influence the physiology of riparian species such as Fremont cottonwood (Populus fremontii), the dominant, native canopy tree species in lowland southwestern US river systems. We wished to determine if the physiology
of this species varies among years, what climatic parameters are related to any observed physiological variation and if individuals
within a P. fremontii population differ in their physiological response to variation through time. We collected tree ring cores from a central
New Mexico cottonwood population and analyzed carbon isotope composition (δ13C) in each year from 1981 to 1995. We used δ13C analysis in this study because it allowed us to obtain multi-year estimates of physiological activity. During these years,
mean stream flow at our study site ranged over two orders of magnitude from 0.82 to 80.94 m3 s−1, precipitation ranged fourfold from 49 to 215 ccmm and mean temperature ranged from 20.5 to 22.6°C during the growing season.
δ13C varied from a low of −26.7‰ in 1984 to a high of −24.7‰ in 1981. Low δ13C values were associated with years in which stream flow and/or precipitation were high and temperature was low. The opposite
was true of years with high δ13C values. We observed a strong linear relationship between δ13C and stream flow during years when stream flow was <25 m3 s−1 but no significant relationship between these variables when stream flow was >25 m3 s−1. Additionally, there was a linear relationship between δ13C and precipitation during years when stream flow was <25 m3 s−1 but not in years when stream flow was >25 m3 s−1. These data suggest that above a threshold of total stream flow, increased flow does not influence physiology. Below this
threshold, precipitation can be an important water source. The ten individuals within our study population varied significantly
in mean δ13C values but responded to interannual variation in a similar manner (i.e., all individuals had low δ13C values when water was abundant). These results suggest that precipitation as well as stream flow are important factors influencing
the physiology of this riparian tree.
Received: 25 November 1998 / Accepted: 9 February 1999 相似文献