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1.
We examined morphological and ultrastructural differences in chloroplasts of cotton leaves and the fruiting organs, bract,
and capsule wall to advance our understanding of their commonly observed differences in photosynthetic efficiency. Chloroplasts
from leaves were large (7.1 μm long in cross section), lens shaped with a well developed membrane system differentiated into
grana and stroma lamellae that occupied the large cross-sectional area (12.3 μm2) of the organelle. A few small plastoglobuli and starch grains were scattered in the stroma region. The bract chloroplasts
were correlative of leaf chloroplasts in size (6.8 μm in length) and shape with the exception that the bract chloroplasts
exhibited greater thylakoid number per granum (15.8) than the leaf chloroplasts (10.5). In contrast to leaf and bract, the
capsule wall chloroplasts were smaller in size (4.3 μm) and cross sectional area (6.8 μm2) than either the leaf or bract. The most intriguing feature of the capsule wall chloroplasts was its domination by large
starch granules (5.3 μm2) in the stroma which filled the whole chloroplast coercing the membrane system to move towards the periphery of the organelle.
Grana number and thylakoids per granum were lowest in the capsule wall chloroplasts.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Maize (Zea mays L.) seedlings of two cultivars (cv. Bastion adapted to W. Europe, and cv. Batan 8686 adapted to the highlands of Mexico),
raised in a glasshouse (19–25 °C), were transferred to 4.5 or 9 °C at photon flux density (PPFD) of 950 μmol m−2 s−1 with 10-h photoperiod for 58 h and then allowed to recover at 22 °C for 16 h (14 h dark and 2 h at PPFD of 180 μmol m−2 s−1). The ultrastructural responses after 4 h or 26 h at 4.5 °C were the disappearance of starch grains in the bundle sheath
chloroplasts and the contraction of intrathylakoid spaces in stromal thylakoids of the mesophyll chloroplasts. At this time,
bundle sheath chloroplasts of cv. Batan 8686 formed peripheral reticulum. Prolonged stress at 4.5 °C (50 h) caused plastid
swelling and the dilation of intrathylakoid spaces, mainly in mesophyll chloroplasts. Bundle sheath chloroplasts of cv. Batan
8686 seedlings appeared well preserved in shape and structure. Batan 8686 had also higher net photosynthetic rates during
chilling and recovery than Bastion. Extended leaf photobleaching developed during the recovery period after chilling at 4.5
°C. This was associated with collapsed chloroplast envelopes, disintegrated chloroplasts and very poor staining. 相似文献
3.
Agnieszka Mostowska 《Acta Physiologiae Plantarum》1998,20(4):419-424
Effect of low (5 mmol·dm−3) and high (10 or 20 mmol·dm−3) doses of 1.10-phenanthroline (Phe), a photodynamic herbicide, on the development of chloroplasts in etiolated and subsequently
illuminated maize seedlings and on the structure of already developed chloroplasts of green maize seedlings was examined.
Etiolated and then irradiated plants were resistant to 5 mmol·dm−3 of Phe with respect to morphology, however Phe caused inhibition of greening and of grana formation. Higher Phe concentrations
followed by exposure to light caused not only total inhibition of greening but also dilation of thylakoids, swelling of chloroplasts,
and finally total destruction of chloroplast structure. Application of Phe in the same concentrations to green plants revealed
that they were resistant to low dose of Phe with respect to morphology and structure of chloroplasts, however 10 and 20 mmol·dm−3 Phe and illumination caused the loss of turgor of treated plants and other photooxidative damages seen at the ultrastructural
level. We concluded that maize, as representant of monocotyledonous plants, is resistant to low (5 mmol·dm−3) Phe concentration. Higher (10 or 20 mmol·dm−3) concentrations, used to determine the site of damage and mode of action of Phe on the level of cell revealed that action
of photodynamic herbicides is based on standard photoinhibition mechanism and also probably on their chelating properties. 相似文献
4.
Tobacco (Nicotiana tabacum L.) plants were cultured in vitro photoautotrophically at three levels of irradiance (PAR 400–700 nm): low (LI, 60 μmol m−2 s−1), middle (MI, 180 μmol m−2 s−1) and high (HI, 270 μmol m−2 s−1). Anatomy of the fourth leaf from bottom was followed during leaf development. In HI and MI plants, leaf area expansion started
earlier as compared to LI plants, and both HI and MI plants developed some adaptations of sun species: leaves were thicker
with higher proportion of palisade parenchyma to spongy parenchyma tissue. Furthermore, in HI and MI plants palisade and spongy
parenchyma cells were larger and relative abundance of chloroplasts in parenchyma cells measured as chloroplasts cross-sectional
area in the cell was lower than in LI plants. During leaf growth, chloroplasts crosssectional area in both palisade and spongy
parenchyma cells in all treatments considerably decreased and finally it occupied only about 5 to 8 % of the cell cross-sectional
area. Thus, leaf anatomy of photoautotrophically in vitro cultured plants showed a similar response to growth irradiance as in vivo grown plants, however, the formation of chloroplasts and therefore of photosynthetic apparatus was strongly impaired. 相似文献
5.
Elizabeth Kebede-Westhead Carolina Pizarro Walter W. Mulbry 《Journal of applied phycology》2006,18(1):41-46
Cultivating algae on nitrogen (N) and phosphorus (P) in animal manure effluents presents an alternative to the current practice of land application. The objective of this study was to determine how algal productivity, nutrient removal efficiency, and elemental composition of turf algae change in response to different loading rates of raw swine manure effluent. Algal biomass was harvested weekly from laboratory scale algal turf scrubber units using four manure effluent loading rates (0.24, 0.40, 0.62 and 1.2 L m−2 d−1) corresponding to daily loading rates of 0.3–1.4 g total N and 0.08–0.42 g total P. Mean algal productivity values increased from 7.1 g DW m−2 d−1 at the lowest loading rate (0.24 L m−2 d−1) to 9.4 g DW m−2 d−1 at the second loading rate (0.40 L m−2 d−1). At these loading rates, algal N and P accounted for> 90% of input N and 68–76% of input P, respectively. However, at higher loading rates algal productivity did not increase and was unstable at the highest loading rate. Mean N and P contents in the dried biomass increased 1.5 to 2.0-fold with increasing loading rate up to maximums of 5.7% N and 1.8% P at 1.2 L m−2 d−1. Biomass concentrations of Al, Ca, Cd, Fe, K, Mg, Mn, Mo, Si, and Zn increased 1.2 to 2.6-fold over the 5-fold range of loading rate. Biomass concentrations of Cd, K, Pb, and Si did not increase significantly with loading rate. At the loading rate of 0.40 L m−2 d−1 (corresponding to peak productivity) the mean concentrations of individual components in the algal biomass were (in mg kg−1): 250 (Al), 4900 (Ca), 0.30 (Cd), 1050 (Fe), 3.4 (Pb), 2500 (Mg), 105 (Mn), 6.0 (Mo), 7,500 (K), and 510 (Zn). At these concentrations, heavy metals in the algal biomass would not be expected to reduce its value as a soil or feed amendment. 相似文献
6.
We assessed the effect of salinity on plant growth and leaf expansion rates, as well as the leaf life span and the dynamics
of leaf production and mortality in seedlings of Avicennia germinans L. grown at 0, 170, 430, 680, and 940 mol m−3 NaCl. The relative growth rates (RGR) after 27 weeks reached a maximum (10.4 mg g−1 d−1) in 170 mol m−3 NaCl and decreased by 47 and 44% in plants grown at 680 and 940 mol m−3 NaCl. The relative leaf expansion rate (RLER) was maximal at 170 mol m−3 NaCl (120 cm m−2 d−1) and decreased by 57 and 52% in plants grown at 680 and 940 mol m−3 NaCl, respectively. In the same manner as RGR and RLER, the leaf production (P) and leaf death (D) decreased in 81 and 67% when salinity increased from 170 to 940 mol m−3 NaCl, respectively. Since the decrease in P with salinity was more pronounced than the decrease in D, the net accumulation of leaves per plant decreased with salinity. Additionally, an evident increase in annual mortality
rates (λ) and death probability was observed with salinity. Leaf half-life (t
0.5) was 425 days in plants grown at 0 mol m−3 NaCl, and decreased to 75 days at 940 mol m−3 NaCl. Thus, increasing salinity caused an increase in mortality rate whereas production of new leaves and leaf longevity
decreased and, finally, the leaf area was reduced. 相似文献
7.
In this study, the effects of Cd on root growth, respiration, and transmembrane electric potential (E
m) of the outer cortical cells in maize roots treated with various Cd concentrations (from 1 μM to 1 mM) for several hours
to one week were studied. The E
m values of root cells ranged between −120 and −140 mV and after addition of Cd they were depolarized immediately. The depolarization
was concentration-dependent reaching the value of diffusion potential (E
D) when the Cd concentration exceeded 100 μM. The values of E
D ranged between −65 to −68 mV (−66 ± 1.42 mV). The maximum depolarization of E
m was registered approx. 2.5 h after addition of Cd to the perfusion solution and in some cases, partial (Cd > 100 μM) or complete
repolarization (Cd < 100 μM) was observed within 8–10 h of Cd treatment. In the time-dependent experiments (0 to 168 h) shortly
after the maximum repolarization of E
m a continuous concentration-dependent decrease of E
m followed at all Cd concentrations. Depolarization of E
m was accompanied by both increased electrolyte leakage and inhibition of respiration, especially in the range of 50 μM to
1 mM Cd, with the exception of root cells treated with 1 and 10 μM Cd for 24 and 48 h. Time course analysis of Cd impact on
root respiration revealed that at higher Cd concentrations (> 50 μM) the respiration gradually declined (∼ 6 h) and then remained
at this lowest level for up to 24 h.
All the Cd concentrations used in this experiment induced significant inhibition of root elongation and concentrations higher
than 100 μM stopped the root growth within the first day of Cd treatment. Our results suggest that Cd does not cause irreversible
changes in the electrogenic plasma membrane H+ ATPase because fusicoccin, an H+ ATPase activator diminished the depolarizing effect of Cd on the E
m. The depolarization of E
m in the outer cortical cells of maize roots was the result of a cumulative effect of Cd on ATP supply, plasmalemma permeability,
and activity of H+ ATPase. 相似文献
8.
Salix gracilistyla is one of the dominant plants in the riparian vegetation of the upper-middle reaches of rivers in western Japan. This species
colonizes mainly sandy habitats, where soil nutrient levels are low, but shows high potential for production. We hypothesized
that S.␣gracilistyla uses nutrients conservatively within stands, showing a high resorption efficiency during leaf senescence. To test this hypothesis,
we examined seasonal changes in nitrogen (N) and phosphorus (P) concentrations in aboveground organs of S. gracilistyla stands on a fluvial bar in the Ohtagawa River, western Japan. The concentrations in leaves decreased from April to May as
leaves expanded. Thereafter, the concentrations showed little fluctuation until September. They declined considerably in autumn,
possibly owing to nutrient resorption. We converted the nutrient concentrations in each organ to nutrient amounts per stand
area on the basis of the biomass of each organ. The resorption efficiency of N and P in leaves during senescence were estimated
to be 44 and 46%, respectively. Annual net increments of N and P in aboveground organs, calculated by adding the amounts in
inflorescences and leaf litter to the annual increments in perennial organs, were estimated to be 9.9 g and 0.83 g m−2 year−1, respectively. The amounts released in leaf litter were 6.7 g N and 0.44 g P m−2. These values are comparable to or larger than those of other deciduous trees. We conclude that S. gracilistyla stands acquire large amounts of nutrients and release a large proportion in leaf litter. 相似文献
9.
Natural and induced cadmium-accumulation in poplar and willow: Implications for phytoremediation 总被引:14,自引:0,他引:14
Robinson Brett H. Mills Tessa M. Petit Daniel Fung Lindsay E. Green Steve R. Clothier Brent E. 《Plant and Soil》2000,227(1-2):301-306
Potentially poplars and willows may be used for the in situ decontamination of soils polluted with Cd, such as pasturelands fertilised with Cd-rich superphosphate fertiliser. Poplar
(Kawa and Argyle) and willow (Tangoio) clones were grown in soils containing a range (0.6–60.6 μg g−1 dry soil) of Cd concentrations. The willow clone accumulated significantly more Cd (9–167 μg g−1 dry matter) than the two poplar clones (6–75 μg g−1), which themselves were not significantly different. Poplar trees (Beaupré) sampled in situ from a contaminated site near the town of Auby, Northern France, were also found to accumulate significant quantities (up
to 209 μg g−1) of Cd. The addition of chelating agents (0.5 and 2 g kg−1 EDTA, 0.5 g kg−1 DTPA and 0.5 g kg−1NTA) to poplar (Kawa) clones caused a temporary increase in uptake of Cd. However, two of the chelating agents (2 g kg−1 EDTA and 0.5 g kg−1 NTA) also resulted in a significant reduction in growth, as well as abscission of leaves. If the results obtained in these
pot experiments can be realised in the field, then a single crop of willows could remove over 100 years worth of fertiliser-induced
Cd contamination from pasturelands.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Morpho-anatomical leaf traits and photosynthetic activity of two alpine herbs, Podophyllum hexandrum (shade-tolerant) and Rheum emodi (light-requiring), were studied under field (PAR>2 000 μmol m−2 s−1) and greenhouse (PAR 500 μmol m−2 s−1) conditions. Mesophyll thickness, surface area of mesophyll cells facing intercellular spaces (Smes), surface area of chloroplasts facing intercellular spaces (Sc), intercellular spaces of mesophyll cells (porosity), photon-saturated rate of photosynthesis per unit leaf area (P
Nmax), and ribulose-1,5-bisphosphate carboxylase/oxygenase activity decreased in the greenhouse with respect to the field and
the decreases were significantly higher in R. emodi than in P. hexandrum. P. hexandrum had lower intercellular CO2 concentration than R. emodi under both irradiances. The differences in acclimation of the two alpine herbs to low irradiance were due to their highly
unlikely changes in leaf morphology, anatomy, and P
Nmax
which indicated that the difference in radiant energy requirement related to leaf acclimation had greater impact under low
than high irradiance. 相似文献
11.
The toxicity of cadmium to barley plants as affected by complex formation with humic acid 总被引:3,自引:0,他引:3
An ‘alternating solution’ culture method was used to study the effects of chloride ions and humic acid (HA) on the uptake
of cadmium by barley plants. The plants were transferred periodically between a nutrient solution and a test solution containing
one of four levels of HA (0, 190, 569 or 1710 μg cm−3) and one of five levels of Cd (0, 0.5, 1.0, 2.5 or 5.0 μg cm−3) in either a 0.006M NaNO3 or 0.006M NaCl medium. Harvest and analysis of shoots and roots was after nineteen days. The distribution of Cd in the test solutions
between Cd2+, CdCl+ and HA-Cd was determined in a separate experiment by dialysis equilibrium.
In the nitrate test solutions Cd uptake was clearly controlled by Cd2+ concentration and was therefore reduced by HA complex formation. In the absence of HA, chloride suppressed Cd uptake indicating
that Cd2+ was the preferred species. However complex formation with Cl− enhanced uptake when HA was present because of an increase in the concentration of inorganic Cd species relative to the nitrate
system.
The ratio root-Cd/shoot-Cd remained at about 10 across a wide range of shoot-Cd concentrations, from about 3 μg g−1 (sub-toxic) up to 85 μg g−1 (80% yield reduction). The ability of the barley plants to accumulate ‘non-toxic’ Cd in their roots was thus very limited.
Humic acid also had no effect on Cd translocation within the plant and the root/shoot weight ratio did not vary with any treatment.
At shoot-Cd concentrations in excess of 50 μg g−1, K, Ca, Cu and Zn uptake was reduced, probably the result of root damage rather than a specific ion antagonism. The highest
concentration of HA also lowered Fe and Zn uptake and there was a toxic effect with increasing HA concentration at Cd=0. However
the lowest HA level, comparable with concentrations found in mineral soil solutions, only reduced yield (in the absence of
Cd) by <5% while lowering Cd uptake across the range of Cd concentrations by 66%–25%. 相似文献
12.
Two rice chlorophyll (Chl) b-less mutants (VG28-1, VG30-5) and the respective wild type (WT) plant (cv. Zhonghua No. 11) were analyzed for the changes
in Chl fluorescence parameters, xanthophyll cycle pool, and its de-epoxidation state under exposure to strong irradiance,
SI (1 700 μmol m−2 s−1). We also examined alterations in the chloroplast ultrastructure of the mutants induced by methyl viologen (MV) photooxidation.
During HI (0–3.5 h), the photoinactivation of photosystem 2 (PS2) appeared earlier and more severely in Chl b-less mutants than in the WT. The decreases in maximal photochemical efficiency of PS2 in the dark (Fv/Fm), quantum efficiency of PS2 electron transport (ΦPS2), photochemical quenching (qP), as well as rate of photochemistry (Prate), and the increases in de-epoxidation state (DES) and rate of thermal dissipation of excitation energy (Drate) were significantly greater in Chl b-mutants compared with the WT plant. A relatively larger xanthophyll pool and 78–83 % conversion of violaxanthin into antheraxanthin
and zeaxanthin in the mutants after 3.5 h of HI was accompanied with a high ratio of inactive/total PS2 (0.55–0.73) and high
1–qP (0.57–0.68) which showed that the activities of the xanthophyll cycle were probably insufficient to protect the photosynthetic
apparatus against photoinhibition. No apparent difference of chloroplast ultrastructure was found between Chl b-less mutants and WT plants grown under low, LI (180 μmol m−2 s−1) and high, HI (700 μmol m−2 s−1) irradiance. However, swollen chloroplasts and slight dilation of thylakoids occurred in both mutants and the WT grown under
LI followed by MV treatment. These typical symptoms of photooxidative damage were aggravated as plants were exposed to HI.
Distorted and loose scattered thylakoids were observed in particular in the Chl b-less mutants. A greater extent of photoinhibition and photooxidation in these mutants indicated that the susceptibility to
HI and oxidative stresses was enhanced in the photosynthetic apparatus without Chl b most likely as a consequence of a smaller antenna size. 相似文献
13.
Vânia L. Souza Alex-Alan F. de Almeida Stella G. C. Lima Júlio C. de M. Cascardo Delmira da C. Silva Pedro A. O. Mangabeira Fábio P. Gomes 《Biometals》2011,24(1):59-71
Cadmium (Cd) originating from atmospheric deposits, from industrial residues and from the application of phosphate fertilizers
may accumulate in high concentrations in soil, water and food, thus becoming highly toxic to plants, animals and human beings.
Once accumulated in an organism, Cd discharges and sets off a sequence of biochemical reactions and morphophysiological changes
which may cause cell death in several tissues and organs. In order to test the hypothesis that Cd interferes in the metabolism
of G. americana, a greenhouse experiment was conducted to measure eventual morphophysiological responses and cell death induced by Cd in
this species. The plants were exposed to Cd concentrations ranging from 0 to 16 mg l−1, in a nutritive solution. In TUNEL reaction, it was shown that Cd caused morphological changes in the cell nucleus of root
tip and leaf tissues, which are typical for apoptosis. Cadmium induced anatomical changes in roots and leaves, such as the
lignification of cell walls in root tissues and leaf main vein. In addition, the leaf mesophyll showed increase of the intercellular
spaces. On the other hand, Cd caused reductions in the net photosynthetic rate, stomatal conductance and leaf transpiration,
while the maximum potential quantum efficiency of PS2 (Fv/Fm) was unchanged. Cadmium accumulated in the root system in high concentrations, with low translocation for the shoot, and
promoted an increase of Ca and Zn levels in the roots and a decrease of K level in the leaves. High concentrations of Cd promoted
morphophysiological changes and caused cell death in roots and leaves tissues of G. americana. 相似文献
14.
Hidenobu Kunii 《Ecological Research》1988,3(3):305-318
In order to determine the seasonal growth and biomass ofTrapa japonica Flerov, field observations were carried out at Ojaga-ike Pond, Chiba, Japan, during 1979 and 1980. In spring, the plant showed
exponential growth (c. 0.080 g g−1 day−1) and shoot elongation was as rapid as 10 cm day−1. The plant attained its maximum biomass (380.5±35.1 g m−2) in late August, and about 50% of this was concentrated in the topmost 30-cm stratum (645.7±33.1 g m−3); maximum total stem length exceeded 6m. The plant produced large (500–800 mg per fruit), but small numbers of nut-like fruit
(maximum, 5 fruits per rosette). Defoliation occurred almost linearly with time at a rate of 30.6 leaves m−2 day−1; annual net leaf production was estimated to be about twice as large as the seasonal maximum leaf biomass. While the number
of leaves per rosette showed moderate seasonal change, rosette density, rosette area and leaf dry weight changed considerably
during the year. From the negative log-log correlation between mean total leaf dry weight per rosette and rosette density,
density-dependent rosette growth was assumed. The cause of the wide spread of this species in aquatic habitats is briefly
discussed in terms of its seed size and morphology. 相似文献
15.
Investigations were made of the growth ofNelumbo nucifera, an aquatic higher plant, in a natural stand in Lake Kasumigaura. A rise of 1.0 m in the water level after a typhoon in August
1986 caused a subsequent decrease in biomass ofN. nucifera from the maximum of 291 g d.w. m−2 in July to a minimum of 75 g d.w. m−2. The biomass recovered thereafter in shallower regions. The underground biomass in October tended to increase toward the
shore. The total leaf area index (LAI) is the sum of LAI of floating leaves and emergent leaves. The maximum total LAI was
1.3 and 2.8 m2 m−2 in 1986 and 1987, respectively. LAI of floating leaves did not exceed 1 m2 m−2. The elongation rates of the petiole of floating and emergent leaves just after unrolling were 2.6 and 3.4 cm day−1, respectively. The sudden rise in water level (25 cm day−1) after the typhoon in August 1986 caused drowning and subsequent decomposition of the mature leaves. Only the young leaves
were able to elongate, allowing their laminae to reach the water surface. The fluctuation in water level, characterized by
the amplitude and duration of flooding and the time of flooding in the life cycle, is an important factor determining the
growth and survival ofN. nucifera in Lake Kasumigaura. 相似文献
16.
When there is a saturating supply of dissolved carbon available, photosynthetic energy storage efficiency (ES) varies linearly
with light fluence rate (I) for both Vallisneria americana and Pisum sativum leaves. The frequently reported hyperbolic relationship between ES and I occurs only when low levels of dissolved carbon
are present in the medium. The linear relationship has its origin in intracellular events and implies that two heat-producing
processes limit the value of ES. The rate of one process varies as I and the other varies as I2. The rates of both processes were changed after a 2 hour exposure to 400 μmol photons m−2 s−1 of red light, speeding up the process that depends linearly on I and slowing the other. Illumination for 1 hour with 100
μmol photons m−2 s−1 of blue (but not red) light moves many chloroplasts from the periclinal to the anticlinal cell walls [Inoue and Shibata (1973)
Planta 114: 341–358]. Blue light exposure of V. americana leaf sections (a) reduced the rate of oxygen evolution under light-limiting conditions by about 22%; (b) increased the value
of ES by an amount dependent on the light fluence rate; and (c) decreased the slope of (ES v I). The slope change indicated
that light absorption had fallen by 26% after blue light exposure. The rate of oxygen evolution (V) was measured under light-limiting
conditions with leaf sections in which the chloroplasts had been immobilised after blue or red light exposure. With both red
and blue-exposed leaf sections, V fell by about 50% after exposure to 1 hour of 1250 μmol photons m−2 s−1 of white light. Thus accumulation of chloroplasts on anticlinal walls did not protect the leaf from photoinactivation by
a high light fluence rate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Chengzhang Liao Yiqi Luo Lifen Jiang Xuhui Zhou Xiaowen Wu Changming Fang Jiakuan Chen Bo Li 《Ecosystems》2007,10(8):1351-1361
Whether plant invasion increases ecosystem carbon (C) stocks is controversial largely due to the lack of knowledge about differences
in ecophysiological properties between invasive and native species. We conducted a field experiment in which we measured ecophysiological
properties to explore the response of the ecosystem C stocks to the invasion of Spartina alterniflora (Spartina) in wetlands dominated by native Scirpus mariqueter (Scirpus) and Phragmites australis (Phragmites) in the Yangtze Estuary, China. We measured growing season length, leaf area index (LAI), net photosynthetic rate (Pn), root
biomass, net primary production (NPP), litter quality and litter decomposition, plant and soil C and nitrogen (N) stocks in
ecosystems dominated by the three species. Our results showed that Spartina had a longer growing season, higher LAI, higher Pn, and greater root biomass than Scirpus and Phragmites. Net primary production (NPP) was 2.16 kg C m−2 y−1 in Spartina ecosystems, which was, on average, 1.44 and 0.47 kg C m−2 y−1 greater than that in Scirpus and Phragmites ecosystems, respectively. The litter decomposition rate, particularly the belowground decomposition rate, was lower for Spartina than Scirpus and Phragmites due to the lower litter quality of Spartina. The ecosystem C stock (20.94 kg m−2) for Spartina was greater than that for Scirpus (17.07 kg m−2), Phragmites (19.51 kg m−2) and the mudflats (15.12 kg m−2). Additionally, Spartina ecosystems had a significantly greater N stock (698.8 g m−2) than Scirpus (597.1 g m−2), Phragmites ecosystems (578.2 g m−2) and the mudflats (375.1 g m−2). Our results suggest that Spartina invasion altered ecophysiological processes, resulted in changes in NPP and litter decomposition, and ultimately led to enhanced
ecosystem C and N stocks in the invaded ecosystems in comparison to the ecosystems with native species. 相似文献
18.
Metrosideros polymorpha, a dominant tree species in Hawaiian ecosystems, occupies a wide range of habitats. Complementary field and common-garden
studies of M. polymorpha populations were conducted across an altitudinal gradient at two different substrate ages to ascertain if the large phenotypic
variation of this species is determined by genetic differences or by phenotypic modifications resulting from environmental
conditions. Several characteristics, including ecophysiological behavior and anatomical features, were largely induced by
the environment. However, other characteristics, particularly leaf morphology, appeared to be mainly determined by genetic
background. Common garden plants exhibited higher average rates of net assimilation (5.8 μmol CO2 m−2 s−1) and higher average stomatal conductance (0.18 mol H2O m−2 s−1) than their field counterparts (3.0 μmol CO2 m−2 s−1, and 0.13 mol H2O m−2 s−1 respectively). Foliar δ13C of most common-garden plants was similar among sites of origin with an average value of −26.9‰. In contrast, mean values
of foliar δ13C in field plants increased substantially from −29.5‰ at low elevation to −24.8‰ at high elevation. Leaf mass per unit area
increased significantly as a function of elevation in both field and common garden plants; however, the range of values was
much narrower in common garden plants (211–308 g m−2 for common garden versus 107–407 g m−2 for field plants). Nitrogen content measured on a leaf area basis in common garden plants ranged from 1.4 g m−2 to 2.4 g m−2 and from 0.8 g m−2 to 2.5 g m−2 in field plants. Photosynthetic nitrogen use efficiency (PNUE) decreased 50% with increasing elevation in field plants and
only 20% in plants from young substrates in the common garden. This was a result of higher rates of net CO2 assimilation in the common garden plants. Leaf tissue and cell layer thickness, and degree of leaf pubescence increased significantly
with elevation in field plants, whereas in common garden plants, variation with elevation of origin was much narrower, or
was entirely absent. Morphological characteristics such as leaf size, petiole length, and internode length decreased with
increasing elevation in the field and were retained when grown in the common garden, suggesting a potential genetic basis
for these traits. The combination of environmentally induced variability in physiological and anatomical characteristics and
genetically determined variation in morphological traits allows Hawaiian M. polymorpha to attain and dominate an extremely wide ecological distribution not observed in other tree species.
Received: 12 March 1997 / Accepted: 27 August 1997 相似文献
19.
H. S. Aldesuquy 《Biologia Plantarum》1995,37(4):605-611
A field experiment was carried out to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in 33 or 66 mM NaCl and indolyl-3-acetic acid (IAA at 50 g m−3), gibberellic acid (GA3 at 100 g m−3) or kinetin (100 g m−3) on some tolerance criteria in wheat flag leaf at different stages of development. At various stages of flag leaf development
pretreatment with 33 or 66 mM NaCl decreased degree of succulence (particularly 66 mM), relative growth rate, net assimilation
rate, relative water content, K+ content and K+/Na+ ratio and at the same time induced accumulation of abscisic acid and Na+. In the majority of cases grain pretreatment with GA3 or kinetin and to a lesser extent with IAA alleviated either partially or completely the deleterious effect of salinity on
the above mentioned parameters. 相似文献
20.
Summary Cadmium and zinc uptake parameters were determined for intact corn (Zea mays L.) seedlings grown for 15 and 22 in nutrient solutions containing levels of Cd and Zn that were similar to those found in
soil solutions. Uptake of both elements was assumed to follow Michaelis-Menten kinetics. Calculations were based on the concentrations
of free ionic Cd (Cd2+) and Zn (Zn2+) rather than the total solution concentration. Rates of Zn uptake were measured by determining depletion of Zn for periods
of up to 30 h from solutions containing initial concentrations of 1.5 and 10μmol Zn 1−1. Depletion curves suggested that Zn uptake characteristics were similar at both levels of Zn in solution. The Imax for Zn
uptake decreased from 550 to 400 pmol m−2 root surface s−1 between 16 and 22 d of growth while Km decreased from 2.2 to 1.5 μmol Zn2+ 1−1. Cadmium uptake parameters were measured by controlling Cd2+ activities in nutrient solution betwen 6.3 to 164 nmol l−1 by continuous circulation of nutrient solution through a mixed-resin system. Imax for Cd uptake was 400 pmol m−2 root surface s−1 at 15 and 22 d of growth. The magnitude of Km increased from 30 to 100 nmol Cd2+ 1−1 during this time period. The Km value suggests that corn is efficient for Cd uptake. The results of these uptake studies
are consistent with the observed uptake of Zn and Cd by corn seedlings in soils. 相似文献