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1.
Phytoplankton biomass is mainly controlled by hydrology and phosphorus concentrations in tropical hydroelectric reservoirs 总被引:5,自引:0,他引:5
Luciana M. Rangel Lúcia H. S. Silva Priscila Rosa Fábio Roland Vera L. M. Huszar 《Hydrobiologia》2012,693(1):13-28
Phytoplankton is widely recognized as being regulated mainly by resources (nutrients and light) and predation by higher trophic levels. In reservoirs, these controls also can be modulated by hydrology, for example through the influence of flow pulses generated by the operation of the dam. In this study, we tested the influence of light, nutrients, and zooplankton grazing pressure, and also hydrology (as water residence time) on the phytoplankton biomass in eight tropical hydroelectric reservoirs, which differ in size, morphometry, location, trophic state, and water residence time. Our hypothesis was that, as these reservoirs are used for hydroelectric purposes, the control that would otherwise be exerted on phytoplankton biomass primarily by resource availability and grazing will also be modulated by hydrology. Low phytoplankton biomass (range of system medians = 12–299 μg C l−1) occurred in most systems, except for one highly eutrophic reservoir (median = 1331 μg C l−1). Our data showed that phosphorus was more often likely to be the limiting nutrient in these systems, as assessed through nutrient limitation indexes (nitrogen and phosphorus), based on concentrations and ratios. For most reservoirs, excluding the eutrophic system with high cyanobacteria biomass, seasonal water residence time was the variable that best explained phytoplankton variation among the several environmental variables analyzed in this study (P < 0.0001; adjusted r 2 = 0.38). Hydrology was an important and additional factor modulating phytoplankton in these tropical reservoirs, directly removing phytoplankton populations and their potential zooplankton grazers by washout, and also affecting nutrient availability. 相似文献
2.
Kirsten Falk Uta Friedrich Goddert von Oheimb Kerstin Mischke Konrad Merkle Hartmut Meyer Werner Härdtle 《Plant Ecology》2010,209(1):47-56
In the present study we analysed whether airborne N pollution may constitute one important driver for the encroachment of
Molinia caerulea in dry heathland ecosystems. Based on full-factorial field experiments (in 2006 and 2008) and complementary greenhouse experiments
(in 2008), we quantified growth responses of Molinia caerulea to N and P fertilisation (50 kg N ha−1 year−1, 20 kg P ha−1 year−1). Aboveground biomass production of Molinia
caerulea was limited by P in 2006, but by N in both experiments in 2008. In the greenhouse experiment, N addition caused a sixfold
increase of the biomass of vegetative tillers, and in all experiments the biomass and numbers of flowering tillers showed
a significant increase due to fertilisation. Our experiments indicated that growth of Molinia caerulea was primarily limited by N, but in dry heaths the kind of nutrient limitation may be mediated by other factors such as water
availability during the vegetative period. Shifts in biomass allocation patterns resulting from N fertilisation showed that
Molinia
caerulea encroachment in dry heaths is not only attributable to increased leaf biomass, but also due to higher investments in reproductive
tissue that allow for increased seed production and thus accelerated encroachment of seedlings in places where the dwarf shrub
canopy has been opened after disturbance. 相似文献
3.
Seasonal dynamics of fine root biomass, root length density, specific root length, and soil resource availability in a Larix gmelinii plantation 总被引:1,自引:0,他引:1
Cheng Yunhuan Han Youzhi Wang Qingcheng Wang Zhengquan 《Frontiers of Biology in China》2006,1(3):310-317
Fine root turnover is a major pathway for carbon and nutrient cycling in terrestrial ecosystems and is most likely sensitive
to many global change factors. Despite the importance of fine root turnover in plant C allocation and nutrient cycling dynamics
and the tremendous research efforts in the past, our understanding of it remains limited. This is because the dynamics processes
associated with soil resources availability are still poorly understood. Soil moisture, temperature, and available nitrogen
are the most important soil characteristics that impact fine root growth and mortality at both the individual root branch
and at the ecosystem level. In temperate forest ecosystems, seasonal changes of soil resource availability will alter the
pattern of carbon allocation to belowground. Therefore, fine root biomass, root length density (RLD) and specific root length
(SRL) vary during the growing season. Studying seasonal changes of fine root biomass, RLD, and SRL associated with soil resource
availability will help us understand the mechanistic controls of carbon to fine root longevity and turnover. The objective
of this study was to understand whether seasonal variations of fine root biomass, RLD and SRL were associated with soil resource
availability, such as moisture, temperature, and nitrogen, and to understand how these soil components impact fine root dynamics
in Larix gmelinii plantation. We used a soil coring method to obtain fine root samples (⩽2 mm in diameter) every month from May to October
in 2002 from a 17-year-old L. gmelinii plantation in Maoershan Experiment Station, Northeast Forestry University, China. Seventy-two soil cores (inside diameter
60 mm; depth intervals: 0–10 cm, 10–20 cm, 20–30 cm) were sampled randomly from three replicates 25 m × 30 m plots to estimate
fine root biomass (live and dead), and calculate RLD and SRL. Soil moisture, temperature, and nitrogen (ammonia and nitrates)
at three depth intervals were also analyzed in these plots. Results showed that the average standing fine root biomass (live
and dead) was 189.1 g·m−2·a−1, 50% (95.4 g·m−2·a−1) in the surface soil layer (0–10 cm), 33% (61.5 g·m−2·a−1), 17% (32.2 g·m−2·a−1) in the middle (10–20 cm) and deep layer (20–30cm), respectively. Live and dead fine root biomass was the highest from May
to July and in September, but lower in August and October. The live fine root biomass decreased and dead biomass increased
during the growing season. Mean RLD (7,411.56 m·m−3·a−1) and SRL (10.83 m·g−1·a−1) in the surface layer were higher than RLD (1 474.68 m·m−3·a−1) and SRL (8.56 m·g−1·a−1) in the deep soil layer. RLD and SRL in May were the highest (10 621.45 m·m−3 and 14.83m·g−1) compared with those in the other months, and RLD was the lowest in September (2 198.20 m·m−3) and SRL in October (3.77 m·g−1). Seasonal dynamics of fine root biomass, RLD, and SRL showed a close relationship with changes in soil moisture, temperature,
and nitrogen availability. To a lesser extent, the temperature could be determined by regression analysis. Fine roots in the
upper soil layer have a function of absorbing moisture and nutrients, while the main function of deeper soil may be moisture
uptake rather than nutrient acquisition. Therefore, carbon allocation to roots in the upper soil layer and deeper soil layer
was different. Multiple regression analysis showed that variation in soil resource availability could explain 71–73% of the
seasonal variation of RLD and SRL and 58% of the variation in fine root biomass. These results suggested a greater metabolic
activity of fine roots living in soil with higher resource availability, which resulted in an increased allocation of carbohydrate
to these roots, but a lower allocation of carbohydrate to those in soil with lower resource availability.
__________
Translated from Acta Phytoecologica Sinica, 2005, 29(3): 403–410 [译自: 植物生态学报, 2005, 29(3): 403–410] 相似文献
4.
Plants in nutrient-poor environments typically have low foliar nitrogen (N) concentrations, long-lived tissues with leaf traits
designed to use nutrients efficiently, and low rates of photosynthesis. We postulated that increasing N availability due to
atmospheric deposition would increase photosynthetic capacity, foliar N, and specific leaf area (SLA) of bog shrubs. We measured
photosynthesis, foliar chemistry and leaf morphology in three ericaceous shrubs (Vaccinium myrtilloides, Ledum groenlandicum and Chamaedaphne calyculata) in a long-term fertilization experiment at Mer Bleue bog, Ontario, Canada, with a background deposition of 0.8 g N m−2 a−1. While biomass and chlorophyll concentrations increased in the highest nutrient treatment for C. calyculata, we found no change in the rates of light-saturated photosynthesis (A
max), carboxylation (V
cmax), or SLA with nutrient (N with and without PK) addition, with the exception of a weak positive correlation between foliar N
and A
max for C. calyculata, and higher V
cmax in L. groenlandicum with low nutrient addition. We found negative correlations between photosynthetic N use efficiency (PNUE) and foliar N, accompanied
by a species-specific increase in one or more amino acids, which may be a sign of excess N availability and/or a mechanism
to reduce ammonium (NH4) toxicity. We also observed a decrease in foliar soluble Ca and Mg concentrations, essential minerals for plant growth, but
no change in polyamines, indicators of physiological stress under conditions of high N accumulation. These results suggest
that plants adapted to low-nutrient environments do not shift their resource allocation to photosynthetic processes, even
after reaching N sufficiency, but instead store the excess N in organic compounds for future use. In the long term, bog species
may not be able to take advantage of elevated nutrients, resulting in them being replaced by species that are better adapted
to a higher nutrient environment. 相似文献
5.
Carbon allocation in ectomycorrhizal plants at limited and optimal N supply: an attempt at unraveling conflicting theories 总被引:1,自引:0,他引:1
Ana Corr��a R��diger Hampp Elisabeth Magel Maria-Am��lia Martins-Lou??o 《Mycorrhiza》2011,21(1):35-51
With regard to mycorrhiza, conflicting theories try to explain how the balance between fungal demand for carbohydrates and
the plant’s needs for nutrients varies, resulting in conflicting predictions. In order to evaluate current concepts, we investigated
some metabolic parameters, which are indicative for plant carbon allocation in response to mycorrhization at limited and optimal
N supply. Pinus pinaster seedlings were inoculated with living or dead (control) cultures of Pisolithus tinctorius, supplied with ammonium at 4 (limiting) or 7% d−1 (non-limiting) N relative addition rate (RARN), and followed development for 29 days. Mycorrhizal colonization of roots was quantified by the determination of ergosterol.
A series of enzymes (sucrose and trehalose metabolism, anaplerosis) and metabolites (soluble carbohydrate, including trehalose;
fructose 2,6 bisphosphate, free amino acids) relevant in the C/N exchange between symbionts, and in the carbon allocation
and sink strength within the plant were assayed for 2-day-intervals for up to 14 days, and at 5-day-intervals for the rest
of the experiment. The first 10 days reflected the establishment of mycorrhizal interaction, and the carbon allocation to
the root was higher in M plants independent of N supply. Following this period, carbon allocation became N-related, higher
at low, and lower at high N supply. The belowground C investment of M plants was dependent on N availability, but not on N
gain. Finally, increased belowground C allocation was accompanied by a shift from plant to fungal metabolism. 相似文献
6.
Adrien C. Finzi 《Biogeochemistry》2009,92(3):217-229
It is commonly assumed that nitrogen (N) is the primary mineral resource limiting the productivity of temperate forests. Sustained
inputs of N via atmospheric deposition are altering the N status of temperate forests raising the possibility that nutrients
such as phosphorus (P) are increasingly limiting productivity. The objective of this study was to determine whether P availability
limits tree growth alone or in combination with N. This study was conducted in two forest types common throughout the New
England landscape of the northeastern United States; in sugar maple and white ash dominated stands growing on base rich parent
material characterized by rapid rates of N cycling and high N availability, and in red oak–beech–hemlock dominated stands
growing on base-poor parent material characterized by slow rates of N cycling and low N availability. Starting in 2004, N
and P were added to replicate plots in each forest type in factorial combination at a rate of 150 and 50 kg ha−1 year−1, respectively. Diameter growth rates of all trees >10 cm DBH were measured in 2005 and 2006 using dendrometer bands and converted
into units of basal area increment (BAI) and wood production. Following 2 years of fertilization, basal area increment in
the sugar maple–white ash forests remained strongly N limited. Fertilization with P did not significantly increase BAI alone,
although both N and P fertilization tended (P < 0.10) to increase diameter growth in white ash. Wood production in the N-fertilized plots increased by 100 g C m−2 year−1, roughly doubling production in the non-fertilized plots. In the red oak–beech–hemlock stands, there was no overall effect
of N or P fertilization on BAI or wood production because BAI in some species was stimulated by fertilization with N alone
(e.g., black cherry, red oak), while in other species BAI was unaffected (e.g., red maple, beech) or negatively affected by
fertilization with N or P (e.g., eastern hemlock). Given that BAI in several tree species responded to fertilization with
N alone and that only one species responded to P fertilization once N was added, this study suggests that decades of atmospheric
N deposition have not (yet) resulted in widespread P limitation or saturation of tree demand for N. 相似文献
7.
Optimality and phenotypic plasticity of shoot-to-root ratio under variable light and nutrient availabilities 总被引:3,自引:0,他引:3
We studied the phenotypic plasticity of shoot-to-root ratio with a model of plant growth in different availabilities of light and nutrients. Optimal shoot-to-root ratio was defined as the equal limitation of growth by light and nutrients. An optimally growing plant had a curved relative growth rate (RGR) isoclines and a faster growth rate than a fixed-allocation plant having right-angled RGR isoclines. We assumed the plant be exposed to a unit standard deviation of bivariate normally distributed resources. Plants were more plastic in a low than in a high resource availability. Negative correlation between resources increased and positive correlation decreased plasticity. Plasticity was high in plants that saturate at low resource availabilities but independent of maximum growth rate. A trade-off between the maximum growth rate and plasticity of shoot-to-root allocation may rise indirectly from the tendency of fast-growing plants to have high resource requirements. 相似文献
8.
Nuisance growth of Myriophyllum aquaticum has often been attributed to high amounts of nutrients. The uptake of nitrogen and phosphorus from sediments and their allocation
have been documented in both natural and laboratory populations. However, nutrient loading to surface water is increasingly
becoming an important issue for water quality standards. Aquatic macrophytes that develop adventitious roots may be able to
survive through the uptake of water column nutrients. Our objectives for this study were to assess M. aquaticum growth when combinations of nitrogen and phosphorus were added to the water column. Mesocosm experiments were conducted where
nitrogen (1.8, 0.8, and 0.4 mg l−1; high, medium, and low) and phosphorus (0.09, 0.03, 0.01 mg l−1; high, medium, and low) concentrations were paired and added to the water column. After 12 weeks, the combination of 1.80:0.01 N:P
resulted in greater (P < 0.01) total biomass and greater biomass for all plant tissues. Total biomass at the 1.80:0.01 N:P combination was 53% greater
than biomass at all other combinations. The yield response of M. aquaticum was a quadratic function of tissue nutrient content. Yield was positively (r
2 = 0.82) related to increasing nitrogen content, whereas a negative (r
2 = 0.89) relationship was determined for increasing phosphorus content. We propose the negative relationship is due to increased
nutrient competition and shading by algae resulting in reduced M. aquaticum growth. Tissue nutrient content indicated that critical concentrations (1.8% nitrogen and 0.2% phosphorus) for growth were
not attained except for nitrogen in plants grown in the 1.80:0.01 N:P combination. These data provide further evidence that
M. aquaticum requires high levels of nitrogen to achieve nuisance growth. Survival through uptake of water column nutrients may be a mechanism
for survival during adverse conditions, a means of long distance dispersal of fragments, or may offer a competitive advantage
over species that rely on sediment nutrients. 相似文献
9.
Alejandro Mora Izquierdo María del Pilar Nicasio Torres Gabriela Sepúlveda Jiménez Francisco Cruz Sosa 《Acta Physiologiae Plantarum》2011,33(6):2135-2147
Cecropia peltata is popularly known as “guarumbo” in Mexico and is used in traditional medicine for treatment of diabetes mellitus. C. peltata plants were cultivated in a hydroponic system under controlled conditions. Gradients of light (20, 30 and 100 μmol m−2 s−1) and nitrate concentrations (13, 2 and 0.2 mM) were applied to estimate their effect on biomass allocation and accumulation
of bioactive (chlorogenic acid and isoorientin) phenolic compounds over a 28-day period. According to carbon nutrient balance
(CNB) hypothesis predictions, biomass accumulation in foliage was stimulated by the highest irradiance (100 μmol m−2 s−1); similarly, at highest irradiance in combination with lowest nitrate concentration (0.2 mM), root growth was stimulated
(root-to-shoot ratio increased twofold with respect to the control). In these conditions, total phenolics (TP) and chlorogenic
acid (CGA) contents were higher in aerial parts than in roots, with a 3.8-fold increase in TP and a 7.7-fold increase in CGA
in foliage with respect to the control plants. Isoorientin was accumulated at very low levels. Antioxidant activity and total
phenolic content showed a strong positive correlation. Phenylalanine ammonia-lyase activity (PAL) in aerial parts exhibited
significant changes (>twofold) by highest irradiance. C. peltata plants allocate biomass and/or phenolic compounds to compensate the oxidative damage (increase in MDA levels) due to changes
in light and nitrate restriction. The results are the basis for the establishment of a system of C. peltata culture in view of the potential use of C. peltata in therapeutic preparations for the treatment of diabetes mellitus. 相似文献
10.
Short-term soil inorganic N pulse after experimental fire alters invasive and native annual plant production in a Mojave Desert shrubland 总被引:1,自引:0,他引:1
Todd C. Esque Jason P. Kaye Sara E. Eckert Lesley A. DeFalco C. Richard Tracy 《Oecologia》2010,164(1):253-263
Post-fire changes in desert vegetation patterns are known, but the mechanisms are poorly understood. Theory suggests that
pulse dynamics of resource availability confer advantages to invasive annual species, and that pulse timing can influence
survival and competition among species. Precipitation patterns in the American Southwest are predicted to shift toward a drier
climate, potentially altering post-fire resource availability and consequent vegetation dynamics. We quantified post-fire
inorganic N dynamics and determined how annual plants respond to soil inorganic nitrogen variability following experimental
fires in a Mojave Desert shrub community. Soil inorganic N, soil net N mineralization, and production of annual plants were
measured beneath shrubs and in interspaces during 6 months following fire. Soil inorganic N pools in burned plots were up
to 1 g m−2 greater than unburned plots for several weeks and increased under shrubs (0.5–1.0 g m−2) more than interspaces (0.1–0.2 g m−2). Soil NO3
−−N (nitrate−N) increased more and persisted longer than soil NH4
+−N (ammonium−N). Laboratory incubations simulating low soil moisture conditions, and consistent with field moisture during
the study, suggest that soil net ammonification and net nitrification were low and mostly unaffected by shrub canopy or burning.
After late season rains, and where soil inorganic N pools were elevated after fire, productivity of the predominant invasive
Schismus spp. increased and native annuals declined. Results suggest that increased N availability following wildfire can favor invasive
annuals over natives. Whether the short-term success of invasive species following fire will direct long-term species composition
changes remains to be seen, yet predicted changes in precipitation variability will likely interact with N cycling to affect
invasive annual plant dominance following wildfire. 相似文献
11.
Effects of prescribed burning on plant available nutrients
in dry heathland ecosystems 总被引:2,自引:0,他引:2
Abdelmenam Mohamed Werner Härdtle Bettina Jirjahn Thomas Niemeyer Goddert von Oheimb 《Plant Ecology》2007,189(2):279-289
Heathland management is an important tool with which to modify ecosystem impacts caused by atmospheric nutrient deposition.
Since changes in nutrient availability as a result of management measures affect the outcomes of heathland succession and
species competition, studies on this issue are important from both a nature conservation and management point of view. This
study reports the effects of prescribed burning on nutrient availability in dry heathland soils and the nutrient content of
the two competing heathland species Calluna vulgaris and Deschampsia flexuosa, with particular reference to N and P. We hypothesise that winter prescribed burning leads to additional N availability,
which enhances the importance of P in the context of nutrient limitation in heathland ecosystems. In the nature reserve “Lueneburg
Heath” (NW Germany) we examined the availability of nutrients in the humus horizons and in the leachate as well as the relevant
C:element ratios in Calluna and Deschampsia before and after a burning experiment. Our results show that prescribed burning resulted in drastically increased NH4+ availability in the O-horizon. We observed only short-term effects (for NO3−, PO43−, Mg) and insignificant effects on the availability of other nutrients (K, Ca). As a consequence of an increased nutrient
availability in the humus horizons and a limited nutrient uptake by plants after burning, leaching increased significantly
for N, Ca, K, and Mg after burning treatment. No significant changes were found in the foliar C:N ratios for either species
after prescribed burning, although Deschampsia showed an increased deficiency for all the other nutrients, particularly for P, as expressed by increased foliar C:P and
N:P ratios. By contrast, the nutrient content of Calluna did not change significantly, suggesting that prescribed burning favours the competitive capacity of Calluna as against Deschampsia. We assume that water shortage as a result of changes in the microclimate was mainly responsible for the deterioration of
the nutrient content of Deschampsia. This gives Calluna a competitive advantage, enabling it to out-compete Deschampsia on burned heathlands, with respect to the key factor P-limitation. 相似文献
12.
Dana Michael Blumenthal 《Biological invasions》2009,11(6):1281-1290
Increases in nitrogen (N) availability can favor fast-growing invasive species over slow-growing native species. One way to
reduce N availability is to add labile carbon (C) to the soil, which can lead to microbial immobilization of plant available
N. This method has been used, with widely varying degrees of success, to both study and control plant invasions. One reason
that C addition might not work as expected is that N is not always the limiting resource for plant growth. For example, if
plant growth is limited by water, changes in N availability might have little effect on invasion. Here I ask whether effects
of C addition on N availability, resident plant biomass, and invasion depend on water availability in semi-arid mixedgrass
prairie. Six invasive species were seeded into plots treated with a factorial combination of water (ambient or added) and
N (+C, control or +N). Carbon addition reduced capture of mineral N by resin probes (by an average of 73%), and reduced biomass
of resident species (from 336 g m−2 to 203 g m−2), both with and without added water. In contrast, because there was little invasion in ambient-water plots, C addition reduced
invasion only in added-water plots. Given added water, C addition reduced biomass of Centaurea diffusa by 95%, and prevented invasion by Gypsophila paniculata and Linaria dalmatica. Mechanisms by which C addition reduced invasion varied by species, with added C reducing the growth of individual C. diffusa plants, but reducing numbers of G. paniculata and L. dalmatica individuals. 相似文献
13.
Intra and interspecific competition among invasive and native species during early stages of plant growth 总被引:2,自引:0,他引:2
Seema Mangla Roger L. Sheley Jeremy J. James Steven R. Radosevich 《Plant Ecology》2011,212(4):531-542
Plant competition is a primary ecological process limiting grassland restoration success. Appropriate restoration techniques
require an understanding of the degree to which intra and interspecific competition control invasive and native plant growth.
The objective of this study was to determine how the intensity of intra and interspecific competition changes during early
stages of plant growth. Two invasive (Bromus
tectorum and Taeniatherum caput-medusae) and two native (Pseudoroegneria
spicata and Poa
secunda) species were grown in a diallel competition experiment, either alone or in 1:1 binary combinations and exposed to two levels
of N (no N or 400 mg N kg−1 soil added) in a greenhouse. Total biomass for each species was quantified over four harvests and competitive effects were
calculated. Our results show that the relative magnitude of intra and interspecific competition changes through time. Intraspecific
competition was intense for native species at the initial harvests and therefore important in contributing to the outcome
of final size of native species seedlings. Interestingly, bluebunch wheatgrass imposed interspecific competition on annual
grasses at the first two harvests and appeared to be a better competitor than Sandberg’s bluegrass. We found that fast growing
invasive species became more competitive compared to slow growing native species with increasing N and appear to establish
a positive feedback mechanism between size and resource uptake. Opportunities to improve restoration success exist from determining
the optimum combination of density, species proportion, and their spatial arrangement in various ecosystems and environments. 相似文献
14.
The above-ground accumulation of N,N uptake and litter quality resulting from improved or deteriorated availability of water
and nutrients in a 25 year old Norway spruce stand in SW Sweden (as part of the Skogaby project) is presented. Treatment include
irrigation; artificial drought; ammonium sulphate addition; N-free-fertilisation and irrigation with liquid fertilisers including
a complete set of nutrients according to the Ingested principle (fertigation).
At start of the experiment the stand contained 86.5 t dry mass and 352 kg N ha−1. The following three years the annual N uptake in untreated trees was 32 kg N ha−1 to be compared with the annual N throughfall of 17 kg ha−1. Simultaneously, the treatment with ammonium sulphate and liquid fertilisation resulted in 48 and 56 kg ha−1 y−1, respectively, in treatment specific N-uptake following an application of 100 kg N ha−1 y−1. Addition of a N-free fertiliser resulted in improved N-uptake by 19 kg N ha−1 y−1 and irrigation by 10 kg N ha−1 y−1, compared to control. A linear relation between total above-ground dry mass production and N-uptake was found for trees growing
with similar water availability. Dry mass production increased with increased water availability given the same N-uptake.
It is concluded that the studied stand this far is not N saturated', as N fertilisation resulted in both increased N uptake
and increased growth. Addition of a N-free-fertiliser resulted in increased uptake of N compared to the control, indicating
an increased mineralisation rate or uptake capacity of the root system. The linear relation between N uptake and biomass production
shows that at this study site N is a highly limiting factor for growth. 相似文献
15.
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as
a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L−1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L−1 h−1. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L−1 in 26.5 h at a mean growth rate 3.37 g DW L−1 h−1. Mean specific growth rate μ was about 0.1 h−1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from
0.8 to 81.6 g DW L−1 in 66.5 h at a mean growth rate 1.22 g DW L−1 h−1 and μ = 0.07 h−1. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities
higher than 10 g DW L−1) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L−1) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)−1. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping
aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency. 相似文献
16.
An ecosystem model of the phytoplankton competition in the East China Sea, as based on field experiments 总被引:1,自引:0,他引:1
Yanbin Li Xiulin Wang Xiurong Han Keqiang Li Xixi Zhao Xiaoyong Shi 《Hydrobiologia》2008,600(1):283-296
An ecological dynamic model for the simulation of two pelagic phytoplankton groups is developed in this article. Model parameters
were adjusted and validated based on the light-limited field culture experiments and the mesocosm experiments in the East
China Sea (ECS). The calculation comparisons from the proposed model, along with field experiment observations, show that
the model simulate the datasets very well, qualitatively and quantitatively. The parameters’ sensitivity analysis indicates
that the competition between the diatoms and dinoflagellates is most sensitive to the photosynthetic process, followed by
the exudation process of the phytoplankton, while the autolysis and respiration processes of phytoplankton and the grazing
and exudation processes of zooplankton can also influence this competition to some extent. The sensitive parameters include:
the photosynthetic optimal specific rate; the optimal irradiance and optimal temperature for phytoplankton growth; and the
half-saturation constant for limiting nutrients, etc. Results of the sensitivity analysis also indicate that light, temperature
and limiting nutrients are the controlling environmental factors for the competition between the diatoms and dinoflagellates
in the ECS. In order to explore the effects of light and nutrients on the phytoplankton competition, simulations were carried
out with varying light and nutrient conditions. Model simulations suggest that the diatoms favor higher irradiance, lower
DIN/PO4–P ratios, higher SiO4–Si/DIN ratios and higher nutrient concentrations, as compared to the dinoflagellates. These results support the speculation
that the increase in the DIN/PO4−P ratio and the decrease in the SiO4–Si/DIN ratio in the ECS may be responsible for the composition change in the functional Harmful Algal Bloom (HAB) groups
from the diatom to the dinoflagellate communities over the last two decades.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: L. Naselli-Flores 相似文献
17.
Smita Srivastava Ashok Kumar Srivastava 《In vitro cellular & developmental biology. Plant》2012,48(1):73-84
Azadirachtin, a well-known biopesticide, is a secondary metabolite extracted from the seeds of Azadirachta indica. In the present study, azadirachtin was produced in hairy roots of A. indica, generated by Agrobacterium rhizogenes-mediated transformation of leaf explants. Liquid cultures of A. indica hairy roots were developed with a liquid-to-flask volume ratio of 0.15. The kinetics of growth and azadirachtin production
were established in a basal plant growth medium containing MS medium major and minor salts, Gamborg’s medium vitamins, and
30 g l−1 sucrose. The highest azadirachtin accumulation in the hairy roots (up to 3.3 mg g−1) and azadirachtin production (∼44 mg l−1) was obtained on Day 25 of the growth cycle, with a biomass production of 13.3 g l−1 dry weight. To enhance the production of azadirachtin, a Plackett–Burman experimental design protocol was used to identify
key medium nutrients and concentrations to support high root biomass production and azadirachtin accumulation in hairy roots.
The optimal nutrients and concentrations were as follows: 40 g l−1 sucrose, 0.19 g l−1 potassium dihydrogen phosphate, 3.1 g l−1 potassium nitrate, and 0.41 g l−1 magnesium sulfate. Concentrations were determined by a central composite design protocol and verified in shake-flask cultivation.
The optimized medium composition yielded a root biomass production of 14.2 g l−1 and azadirachtin accumulation of 5.2 mg g−1, which was equivalent to an overall azadirachtin production of 73.84 mg l−1, 68% more than that obtained under non-optimized conditions. 相似文献
18.
In semi-arid regions, a major population limitation for riparian trees is seedling desiccation during the dry season that
follows annual spring floods. We investigated the stress response of first-year pioneer riparian seedlings to experimental
water table declines (0, 1 and 3 cm day−1), focusing on the three dominant cottonwood and willows (family Salicaceae) in California’s San Joaquin Basin. We analyzed
growth and belowground allocation response to water stress, and used logistic regression to determine if these traits had
an influence on individual survival. The models indicate that high root growth (>3 mm day−1) and low shoot:root ratios (<1.5 g g−1) strongly predicted survival, but there was no evidence that plants increased belowground allocation in response to drawdown.
Leaf δ13C values shifted most for the best-surviving species (net change of +3.5 per mil from −30.0 ± 0.3 control values for Goodding’s
willow, Salix gooddingii), implying an important role of increased water-use efficiency for surviving water stress. Both S. gooddingii and sandbar willow (S. exigua) reduced leaf size from controls, whereas Fremont cottonwood (Populus fremontii) sustained a 29% reduction in specific leaf area (from 13.4 to 9.6 m2 kg−1). The functional responses exhibited by Goodding’s willow, the more drought-tolerant species, may play a role in its greater
relative abundance in dry regions such as the San Joaquin Basin. This study highlights the potential for a shift in riparian
forest composition. Under a future drier climate regime or under reduced regulated river flows, our results suggest that willow
establishment will be favored over cottonwood. 相似文献
19.
Tamotsu Hoshino Fumihiro Terami Oleg B. Tkachenko Motoaki Tojo Naoyuki Matsumoto 《Mycoscience》2010,51(2):98-103
The snow mold fungus, Sclerotinia borealis, shows optimal growth at 4°C on potato dextrose agar (PDA) and can grow even at subzero temperature. Its mycelial growth
was improved on frozen PDA at −1°C and on PDA containing potassium chloride (KCl) (water potential, −4.27 to −0.85 MPa) or
d(−) sorbitol (−3.48 to −0.92 MPa). Its optimal growth temperature shifted from 4 to 10°C on PDA amended with KCl or sorbitol,
indicating that inherent optimal growth occurs at high temperatures. These results suggest that S. borealis uses concentrated nutrients in the frozen environment and that such physiologic characteristics are critical for the fungus
to prevail at subzero temperatures. 相似文献
20.
The eco-physiological responses of three nitrogen-fixing cyanobacteria (N-fixing cyanobacteria), Aphanizomenon gracile, Anabaena minderi, and Ana. torques-reginae, to light were assessed under nutrient saturation. The N-fixing cyanobacteria were isolated into monocultures from a natural
bloom in a shallow colored lake and their growth irradiance parameters and pigment composition were assessed. The different
ecological traits related to light use (μmax, α, I
k) suggest that these N-fixing cyanobacteria are well adapted to low light conditions at sufficient nutrients, yet interspecific
differences were observed. Aphanizomenon gracile and Anabaena minderi had high relative growth rates at low irradiances (ca. 70% of those in high light), low half saturation constant for light-limited
growth (I
k < 9.09 μmol photon m−2 s−1) and high efficiency (α < 0.11 day−1 μmol photon−1 m2 s). Conversely, Ana. torques-reginae showed poorer light competitiveness: low relative growth rates at low irradiances (ca. 40% of those in high light), low α
(0.009 day−1 μmol photon−1 m2 s) and higher I
k (35.5 μmol photon m−2 s−1). Final densities in Aphanizomenon gracile and Anabaena minderi reached bloom densities at irradiances above 30 μmol photon m−2 s−1 with different hierarchy depending on irradiance, whereas Ana. torques-reginae never achieved bloom densities. All species had very low densities at irradiances ≤17 μmol photon m−2 s−1, thus no N-fixing blooms would be expected at these irradiances. Also, under prolonged darkness and at lowest irradiance
(0 and 3 μmol photon m−2 s−1) akinetes were degraded, suggesting that in ecosystems with permanently dark sediments, the prevalence of N-fixing cyanobacteria
should not be favored. All species displayed peaks of phycocyanin, but no phycoeritrin, probably due to the prevailing red
light in the ecosystem from which they were isolated. 相似文献