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1.
Uptake rates of dissolved inorganic phosphorus and dissolved inorganic nitrogen under unsaturated and saturated conditions were studied in young sporophytes of the seaweeds Saccharina latissima and Laminaria digitata (Phaeophyceae) using a “pulse‐and‐chase” assay under fully controlled laboratory conditions. In a subsequent second “pulse‐and‐chase” assay, internal storage capacity (ISC) was calculated based on VM and the parameter for photosynthetic efficiency Fv/Fm. Sporophytes of S. latissima showed a VS of 0.80 ± 0.03 μmol · cm?2 · d?1 and a VM of 0.30 ± 0.09 μmol · cm?2 · d?1 for dissolved inorganic phosphate (DIP), whereas VS for DIN was 11.26 ± 0.56 μmol · cm?2 · d?1 and VM was 3.94 ± 0.67 μmol · cm?2 · d?1. In L. digitata, uptake kinetics for DIP and DIN were substantially lower: VS for DIP did not exceed 0.38 ± 0.03 μmol · cm?2 · d?1 while VM for DIP was 0.22 ± 0.01 μmol · cm?2 · d?1. VS for DIN was 3.92 ± 0.08 μmol · cm?2 · d?1 and the VM for DIN was 1.81 ± 0.38 μmol · cm?2 · d?1. Accordingly, S. latissima exhibited a larger ISC for DIP (27 μmol · cm?2) than L. digitata (10 μmol · cm?2), and was able to maintain high growth rates for a longer period under limiting DIP conditions. Our standardized data add to the physiological understanding of S. latissima and L. digitata, thus helping to identify potential locations for their cultivation. This could further contribute to the development and modification of applications in a bio‐based economy, for example, in evaluating the potential for bioremediation in integrated multitrophic aquacultures that produce biomass simultaneously for use in the food, feed, and energy industries. 相似文献
2.
Variability in iodine in temperate seaweeds and iodine accumulation kinetics of Fucus vesiculosus and Laminaria digitata (Phaeophyceae,Ochrophyta)
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The biogeochemistry of iodine in temperate coastal ecosystems is largely mediated by macroalgae, which act as a major biological sink and source of iodine. Their capacity to accumulate, retain and release iodine has been associated with abiotic and biotic stressors, but quantitative information is limited. We evaluated the seasonal iodine retention capacity of eleven macroalgal species belonging to different systematic groups, collected from two sites in Ireland. Iodine accumulation and retention were then further quantified in Fucus vesiculosus and Laminaria digitata in relation to I? concentrations in seawater and temperature. In general, iodine contents were ~101–102 μmol · (g dw)?1 for Laminariales, 100–101 μmol · (g dw)?1 for Fucales, 10?1–100 μmol · (g dw)?1 for Rhodophyta, and 10?1 μmol · (g dw)?1 for Chlorophyta. Typically, algal iodine contents were above average in winter and below average in summer. Iodine accumulation in F. vesiculosus and L. digitata depended on I? availability and followed the Michaelis‐Menten kinetic. The ratio of maximum accumulation rate to half accumulation coefficient (ρmax: K t) was 2.4 times higher for F. vesiculosus than for L. digitata , suggesting that F. vesiculosus was more efficient in iodine accumulation. Both species exhibited a temperature‐dependent net loss of iodine, and only an exposure to sufficient external I? concentrations compensated for this loss. This study revealed that both environmental (e.g., I? in seawater, temperature) and organismal (e.g., the status of the iodine storage pool) variables determine retention and variability in iodine in temperate seaweeds. 相似文献
3.
The toxigenic diatom Pseudo‐nitzschia cuspidata, isolated from the U.S. Pacific Northwest, was examined in unialgal batch cultures to evaluate domoic acid (DA) toxicity and growth as a function of light, N substrate, and growth phase. Experiments conducted at saturating (120 μmol photons · m?2 · s?1) and subsaturating (40 μmol photons · m?2 · s?1) photosynthetic photon flux density (PPFD), demonstrate that P. cuspidata grows significantly faster at the higher PPFD on all three N substrates tested [nitrate (NO3?), ammonium (NH4+), and urea], but neither cellular toxicity nor exponential growth rates were strongly associated with one N source over the other at high PPFD. However, at the lower PPFD, the exponential growth rates were approximately halved, and the cells were significantly more toxic regardless of N substrate. Urea supported significantly faster growth rates, and cellular toxicity varied as a function of N substrate with NO3?‐supported cells being significantly more toxic than both NH4+‐ and urea‐supported cells at the low PPFD. Kinetic uptake parameters were determined for another member of the P. pseudodelicatissima complex, P. fryxelliana. After growth of these cells on NO3? they exhibited maximum specific uptake rates (Vmax) of 22.7, 29.9, 8.98 × 10?3 · h?1, half‐saturation constants (Ks) of 1.34, 2.14, 0.28 μg‐at N · L?1, and affinity values (α) of 17.0, 14.7, 32.5 × 10?3 · h?1/(μg‐at N · L?1) for NO3?, NH4+ and urea, respectively. These labo‐ratory results demonstrate the capability of P. cuspidata to grow and produce DA on both oxidized and reduced N substrates during both exponential and stationary growth phases, and the uptake kinetic results for the pseudo‐cryptic species, P. fryxelliana suggest that reduced N sources from coastal runoff could be important for maintenance of these small pennate diatoms in U.S. west coast blooms, especially during times of low ambient N concentrations. 相似文献
4.
Marine phytoplankton and macroalgae acquire important resources, such as inorganic nitrogen, from the surrounding seawater by uptake across their entire surface area. Rates of ammonium and nitrate uptake per unit surface area were remarkably similar for both marine phytoplankton and macroalgae at low external concentrations. At an external concentration of 1 μM, the mean rate of nitrogen uptake was 10±2 nmol·cm?2·h?1 (n=36). There was a strong negative relationship between log surface area:volume (SA:V) quotient and log nitrogen content per cm2 of surface (slope=?0.77), but a positive relationship between log SA:V and log maximum specific growth rate (μmax; slope=0.46). There was a strong negative relationship between log SA:V and log measured rate of ammonium assimilation per cm2 of surface, but the slope (?0.49) was steeper than that required to sustain μmax (?0.31). Calculated rates of ammonium assimilation required to sustain growth rates measured in natural populations were similar for both marine phytoplankton and macroalgae with an overall mean of 6.2±1.4 nmol·cm?2·h?1 (n=15). These values were similar to maximum rates of ammonium assimilation in phytoplankton with high SA:V, but the values for algae with low SA:V were substantially less than the maximum rate of ammonium assimilation. This suggests that the growth rates of both marine phytoplankton and macroalgae in nature are often constrained by rates of uptake and assimilation of nutrients per cm2 surface area. 相似文献
5.
Roel Riegman Willem Stolte Anna A. M. Noordeloos Doris Slezak 《Journal of phycology》2000,36(1):87-96
Emiliania huxleyi (strain L) expressed an exceptional P assimilation capability. Under P limitation, the minimum cell P content was 2.6 fmol P·cell?1, and cell N remained constant at all growth rates at 100 fmol N·cell?1. Both, calcification of cells and the induction of the phosphate uptake system were inversely correlated with growth rate. The highest (cellular P based) maximum phosphate uptake rate (VmaxP) was 1400 times (i.e. 8.9 h?1) higher than the actual uptake rate. The affinity of the P‐uptake system (dV/dS) was 19.8 L·μmol?1·h?1 at μ = 0.14 d?1. This is the highest value ever reported for a phytoplankton species. Vmax and dV/dS for phosphate uptake were 48% and 15% lower in the dark than in the light at the lowest growth rates. The half‐saturation constant for growth was 1.1 nM. The coefficient for luxury phosphate uptake (Qmaxt/Qmin) was 31. Under P limitation, E. huxleyi expressed two different types of alkaline phosphatase (APase) enzyme kinetics. One type was synthesized constitutively and possessed a Vmax and half‐saturation constant of 43 fmol MFP·cell?1·h?1 and 1.9 μM, respectively. The other, inducible type of APase expressed its highest activity at the lowest growth rates, with a Vmax and half‐saturation constant of 190 fmol MFP·cell?1·h?1 and 12.2 μM, respectively. Both APase systems were located in a lipid membrane close to the cell wall. Under N‐limiting growth conditions, the minimum N quotum was 43 fmol N·cell?1. The highest value for the cell N‐specific maximum nitrate uptake rate (VmaxN) was 0.075 h?1; for the affinity of nitrate uptake, 0.37 L·μmol?1·h?1. The uptake rate of nitrate in the dark was 70% lower than in the light. N‐limited cells were smaller than P‐limited cells and contained 50% less organic and inorganic carbon. In comparison with other algae, E. huxleyi is a poor competitor for nitrate under N limitation. As a consequence of its high affinity for inorganic phosphate, and the presence of two different types of APase in terms of kinetics, E. huxleyi is expected to perform well in P‐controlled ecosystems. 相似文献
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7.
The goal of this study was to examine growth, erosion rates, and the photosynthetic and nitrogen ecophysiology of the invasive seaweed Undaria pinnatifida (Harv.) Suringar. Sporophytes of U. pinnatifida that appeared in Otago Harbour, southeastern New Zealand, in late autumn (May) 1996 were tagged, and their growth rates followed until the onset of senescence in early summer (November 1996). Blade growth rates were maximal between May and August when they ranged from 0.77 ± 0.05 to 0.93 ± 0.05 cm · d?1 and declined from September onward. In laboratory experiments, U. pinnatifida took up nitrate and ammonium simultaneously at rates ranging from 21.3 ± 2.1 to 179.3 ± 65.1 μmol · g?1 dry weight (dwt) · h?1. When monthly patterns of growth rate, seawater inorganic nitrogen, nitrogen uptake kinetics, soluble tissue nitrate, % tissue carbon (C) and nitrogen (N), and C:N ratio were considered together, there was no evidence that N limited the growth of U. pinnatifida. Furthermore, the photosynthetic parameters Pmax, α, Ek, Ec, and Rd derived from P versus E curves indicated that the growth of U. pinnatifida was not light limited, and that the population could potentially grow deeper than its observed location at 4 m depth. Nitrogen and light ecophysiological parameters of U. pinnatifida more closely resemble those of small, ephemeral seaweeds, such as Ulva, than other members of the Laminariales. We suggest that a “plastic” physiology may allow U. pinnatifida sporophytes to match their physiology to a range of environments, which is one reason for its success as an invasive seaweed. 相似文献
8.
Forest ecosystem respiration estimated from eddy covariance and chamber measurements under high turbulence and substantial tree mortality from bark beetles 总被引:1,自引:0,他引:1
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Heather N. Speckman John M. Frank John B. Bradford Brianna L. Miles William J. Massman William J. Parton Michael G. Ryan 《Global Change Biology》2015,21(2):708-721
Eddy covariance nighttime fluxes are uncertain due to potential measurement biases. Many studies report eddy covariance nighttime flux lower than flux from extrapolated chamber measurements, despite corrections for low turbulence. We compared eddy covariance and chamber estimates of ecosystem respiration at the GLEES Ameriflux site over seven growing seasons under high turbulence [summer night mean friction velocity (u*) = 0.7 m s?1], during which bark beetles killed or infested 85% of the aboveground respiring biomass. Chamber‐based estimates of ecosystem respiration during the growth season, developed from foliage, wood, and soil CO2 efflux measurements, declined 35% after 85% of the forest basal area had been killed or impaired by bark beetles (from 7.1 ± 0.22 μmol m?2 s?1 in 2005 to 4.6 ± 0.16 μmol m?2 s?1 in 2011). Soil efflux remained at ~3.3 μmol m?2 s?1 throughout the mortality, while the loss of live wood and foliage and their respiration drove the decline of the chamber estimate. Eddy covariance estimates of fluxes at night remained constant over the same period, ~3.0 μmol m?2 s?1 for both 2005 (intact forest) and 2011 (85% basal area killed or impaired). Eddy covariance fluxes were lower than chamber estimates of ecosystem respiration (60% lower in 2005, and 32% in 2011), but the mean night estimates from the two techniques were correlated within a year (r2 from 0.18 to 0.60). The difference between the two techniques was not the result of inadequate turbulence, because the results were robust to a u* filter of >0.7 m s?1. The decline in the average seasonal difference between the two techniques was strongly correlated with overstory leaf area (r2 = 0.92). The discrepancy between methods of respiration estimation should be resolved to have confidence in ecosystem carbon flux estimates. 相似文献
9.
Nitrogen fixation has been proposed as a mechanism that allows the diazotrophic cyanobacterium, Cylindrospermopsis raciborskii, to bloom in nitrogen‐limited freshwater systems. However, it is unclear whether dinitrogen fixation (N2 fixation) can supplement available dissolved inorganic nitrogen (DIN) for growth, or only provides minimum nitrogen (N) for cell maintenance under DIN deplete conditions. Additionally, the rate at which cells can switch between DIN use and N2 fixation is unknown. This study investigated N2 fixation under a range of nitrate concentrations. Cultures were grown with pretreatments of nitrate replete (single dose 941 μmol · L?1) and N‐free conditions and then either received a single dose of 941 μmol · L?1 (N941), 118 μmol · L?1 (N118) or 0 N. Heterocysts appeared from days 3 to 5 when treatments of high were transferred to N free media (N941:N0), and from day 5 in N941 transferred to N118 treatments. Conversely, transferring cells from N0 to N941 resulted in heterocysts being discarded from day 3 and day 5 for N0:N118. Heterocyst appearance correlated with a detectable rate of N2 fixation and up‐regulation of nifH gene expression, the discard of heterocysts occurred after sequential reduction of nifH expression and N2 fixation. Nitrate uptake rates were not affected by pretreatment, suggesting no regulation or saturation of this uptake pathway. These data demonstrate that for C. raciborskii, N2 fixation is regulated by the production or discard of heterocysts. In conclusion, this study has shown that N2 fixation only provides enough N to support relatively low growth under N‐limited conditions, and does not supplement available nitrate to increase growth rates. 相似文献
10.
The ichthyotoxic flagellate Pseudochattonella has formed recurrent blooms in the North Sea, Skagerrak and Kattegat since 1998. Five strains of Pseudochattonella farcimen and two strains of P. verruculosa were examined in an assay comparing the light response of specific growth rates over a range of temperatures and salinities to get further knowledge on the autecology of members of this genus. Temperature optima were lower in P. farcimen (9°C–15°C) than in P. verruculosa (12°C–20°C). P. farcimen also showed a somewhat lower salinity optimum (18–26) than P. verruculosa (20–32). All strains showed light‐dependent growth responses reaching saturation between 18 and 52 μmol · photons · m?2 · s?1 at optimal temperature and salinity conditions. Compensation point estimates ranged from 4.2 to 15 μmol · photons · m?2 · s?1. Loss rates increased with temperature and were lowest at salinities close to optimal growth conditions. Blooms of P. farcimen have been recorded in nature under conditions more similar to those minimizing loss rates rather than those maximizing growth rates in our culture study. 相似文献
11.
We quantified the effects of initial macroalgal tissue nitrogen (N) status (depleted and enriched) and varying pulses of nitrate (NO3?) concentration on uptake and storage of nitrogen in Ulva intestinalis L. and Ulva expansa (Setch.) Setch. et N. L. Gardner using mesocosms modeling shallow coastal estuaries in Mediterranean climates. Uptake of NO3? (μmol · g dry weight [dwt]?1 · h?1) was measured as loss from the water after 1, 2, 4, 8, 12, and 24 h and storage as total tissue nitrogen (% dwt) and nitrate (ppm). Both species of algae exhibited a high affinity for NO3? across all N pulses and initial tissue contents. There was greater NO3? removal from the water for depleted than enriched algae across all time intervals. In the low‐N‐pulse treatment, U. intestinalis and U. expansa removed all measurable NO3? within 8 and 12 h, respectively, and in the medium and high treatments, removal was high and then decreased over time. Maximum mean uptake rates of nitrate were greater for U. expansa (~300 μmol · g dwt?1 · h?1) than U. intestinalis (~100 μmol · g dwt?1 · h?1); however, uptake rates were highly variable over time. Overall, U. expansa uptake rates were double those of U. intestinalis. Maximum tissue NO3? for U. expansa was >1,000 ppm, five times that of U. intestinalis, suggesting that U. expansa has a greater storage capacity in this cellular pool. These results showed that opportunistic green algae with differing tissue nutrient histories were able to efficiently remove nitrate from the water across a wide range of N pulses; thus, both are highly adapted to proliferate in estuarine environments with pulsed nutrient supplies. 相似文献
12.
Influences of salinity on the physiology and distribution of the Arctic coralline algae,Lithothamnion glaciale (Corallinales,Rhodophyta)
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Kathryn M. Schoenrock Marion Bacquet Danni Pearce Brice R. Rea J. Edward Schofield James Lea Doug Mair Nicholas Kamenos 《Journal of phycology》2018,54(5):690-702
In Greenland, free‐living red coralline algae contribute to and dominate marine habitats along the coastline. Lithothamnion glaciale dominates coralline algae beds in many regions of the Arctic, but never in Godthåbsfjord, Greenland, where Clathromorphum sp. is dominant. To investigate environmental impacts on coralline algae distribution, calcification and primary productivity were measured in situ during summers of 2015 and 2016, and annual patterns of productivity in L. glaciale were monitored in laboratory‐based mesocosm experiments where temperature and salinity were manipulated to mimic high glacial melt. The results of field and cold‐room measurements indicate that both L. glaciale and Clathromorphum sp. had low calcification and photosynthetic rates during the Greenland summer (2015 and 2016), with maximum of 1.225 ± 0.17 or 0.002 ± 0.023 μmol CaCO 3 · g?1 · h?1 and ?0.007 ±0.003 or ?0.004 ± 0.001 mg O2 · L?1 · h?1 in each species respectively. Mesocosm experiments indicate L. glaciale is a seasonal responder; photosynthetic and calcification rates increase with annual light cycles. Furthermore, metabolic processes in L. glaciale were negatively influenced by low salinity; positive growth rates only occurred in marine treatments where individuals accumulated an average of 1.85 ± 1.73 mg · d?1 of biomass through summer. These results indicate high freshwater input to the Godthåbsfjord region may drive the low abundance of L . glaciale , and could decrease species distribution as climate change increases freshwater input to the Arctic marine system via enhanced ice sheet runoff and glacier calving. 相似文献
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14.
Throughout the summer, abundance of Ulva lactuca L. declined while biomass of Cladophora vagabunda (L.) van den Hoek and Gracilaria tikvahiae McLachlan increased in a New England embayment undergoing eu-trophication (Waquoit Bay, Massachusetts). We investigated the physiological basis for the summer dieback, focusing on temporal variations in photosynthetic performance and tissue nitrogen (N). We also compared photosynthetic and N uptake capabilities of U. lactuca with other abundant species in this eutrophic system. Photosynthetic egiciency and capacity of U. lactuca declined markedly at 25°C, compared with a spring (15°C) peak in photosynthetic performance; Pmax was 4.6 ± 0.3 and 1.8 ± 0.6 μmol O2.m?2.s?1 during spring and summer, respectively. Notably, summer pmax of other abundant species of the embayment was 1.5–3 × higher than that measured for U. lactuca. Ulva lactuca showed a signifciant photosynthetic response to dissolved inorganic carbon enrichment during summer, when water-column-dissolved CO2 levels were 20% of spring values. Although ammonium uptake rates of U. lactuca were extremely high at both subsaturating (15μM) and saturating (75 μM) N concentrations, as predicted by the functional-form hypothesis, tissue N fell to 1% by late summer. We suggest that a carbon imbalance, initiated by rising water temperatures and declining water-column N; thermal stress; and biological factors (competition, grazing) all contribute to the recurrent summer decline of U. lactuca in this shallow, eutrophic embayment. Thus, while the morphology of U. lactuca might be considered a successful strategy for disturbed, or “stressed” (sensu Littler and Littler 1980), habitats, its inability to persist and flourish in this environment emphasizes the complexity of factors at work in natural systems. 相似文献
15.
The red seaweed Gracilariopsis is an important crop extensively cultivated in China for high‐quality raw agar. In the cultivation site at Nanao Island, Shantou, China, G. lemaneiformis experiences high variability in environmental conditions like seawater temperature. In this study, G. lemaneiformis was cultured at 12, 19, or 26°C for 3 weeks, to examine its photosynthetic acclimation to changing temperature. Growth rates were highest in G. lemaneiformis thalli grown at 19°C, and were reduced with either decreased or increased temperature. The irradiance‐saturated rate of photosynthesis (Pmax) decreased with decreasing temperature, but increased significantly with prolonged cultivation at lower temperatures, indicating the potential for photosynthesis acclimation to lower temperature. Moreover, Pmax increased with increasing temperature (~30 μmol O2 · g?1FW · h?1 at 12°C to 70 μmol O2 · g?1FW · h?1 at 26°C). The irradiance compensation point for photosynthesis (Ic) decreased significantly with increasing temperature (28 μmol photons · m?2 · s?1 at high temperature vs. 38 μmol photons · m?2 · s?1 at low temperature). Both the photosynthetic light‐ and carbon‐use efficiencies increased with increasing growth or temperatures (from 12°C to 26°C). The results suggested that the thermal acclimation of photosynthetic performance of G. lemaneiformis would have important ecophysiological implications in sea cultivation for improving photosynthesis at low temperature and maintaining high standing biomass during summer. Ongoing climate change (increasing atmospheric CO2 and global warming) may enhance biomass production in G. lemaneiformis mariculture through the improved photosynthetic performances in response to increasing temperature. 相似文献
16.
Process optimization and modeling for the cultivation of Nannochloropsis sp. and Tetraselmis striata via response surface methodology
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The aim of this study was to determine the optimal physical process conditions for the cultivation of locally isolated strains of Nannochloropsis sp. and Tetraselmis striata to achieve maximum growth rate. It was essential to evaluate biomass production at different agitation rates, light intensities, and temperature levels. Central composite design and response surface methodology were applied to design the experiments and optimize the cultivation process for Nannochloropsis sp. and T. striata. The specific growth rate of 0.250 d?1 was obtained for Nannochloropsis sp. cells under the light intensity of 54 μmol photons · m?2 · s?1, at the agitation rate of 151 rpm in 24.5°C. The optimal physical process conditions for T. striata were obtained under the light intensity of 56 μmol photons · m?2 · s?1 in 25.5°C at the agitation rate of 151 rpm in 25.5°C, resulting in a specific growth rate of 0.226 d?1. The predicted values were justified by the verification tests. Good agreement between the predicted values and the experimental values confirmed the validity of the models for the cultivation of microalgal strains. In this article, the noteworthy result was that temperature was a dominant factor in obtaining high chl‐a content for Nannochloropsis sp., whereas the growth of T. striata strongly depended on light exposure. 相似文献
17.
Microbial physiology and soil CO2 efflux after 9 years of soil warming in a temperate forest – no indications for thermal adaptations
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Andreas Schindlbacher Jörg Schnecker Mounir Takriti Werner Borken Wolfgang Wanek 《Global Change Biology》2015,21(11):4265-4277
Thermal adaptations of soil microorganisms could mitigate or facilitate global warming effects on soil organic matter (SOM) decomposition and soil CO2 efflux. We incubated soil from warmed and control subplots of a forest soil warming experiment to assess whether 9 years of soil warming affected the rates and the temperature sensitivity of the soil CO2 efflux, extracellular enzyme activities, microbial efficiency, and gross N mineralization. Mineral soil (0–10 cm depth) was incubated at temperatures ranging from 3 to 23 °C. No adaptations to long‐term warming were observed regarding the heterotrophic soil CO2 efflux (R10 warmed: 2.31 ± 0.15 μmol m?2 s?1, control: 2.34 ± 0.29 μmol m?2 s?1; Q10 warmed: 2.45 ± 0.06, control: 2.45 ± 0.04). Potential enzyme activities increased with incubation temperature, but the temperature sensitivity of the enzymes did not differ between the warmed and the control soils. The ratio of C : N acquiring enzyme activities was significantly higher in the warmed soil. Microbial biomass‐specific respiration rates increased with incubation temperature, but the rates and the temperature sensitivity (Q10 warmed: 2.54 ± 0.23, control 2.75 ± 0.17) did not differ between warmed and control soils. Microbial substrate use efficiency (SUE) declined with increasing incubation temperature in both, warmed and control, soils. SUE and its temperature sensitivity (Q10 warmed: 0.84 ± 0.03, control: 0.88 ± 0.01) did not differ between warmed and control soils either. Gross N mineralization was invariant to incubation temperature and was not affected by long‐term soil warming. Our results indicate that thermal adaptations of the microbial decomposer community are unlikely to occur in C‐rich calcareous temperate forest soils. 相似文献
18.
Piotr Trębicki Narelle Nancarrow Ellen Cole Nilsa A. Bosque‐Pérez Fiona E. Constable Angela J. Freeman Brendan Rodoni Alan L. Yen Jo E. Luck Glenn J. Fitzgerald 《Global Change Biology》2015,21(9):3511-3519
Current atmospheric CO2 levels are about 400 μmol mol?1 and are predicted to rise to 650 μmol mol?1 later this century. Although the positive and negative impacts of CO2 on plants are well documented, little is known about interactions with pests and diseases. If disease severity increases under future environmental conditions, then it becomes imperative to understand the impacts of pathogens on crop production in order to minimize crop losses and maximize food production. Barley yellow dwarf virus (BYDV) adversely affects the yield and quality of economically important crops including wheat, barley and oats. It is transmitted by numerous aphid species and causes a serious disease of cereal crops worldwide. This study examined the effects of ambient (aCO2; 400 μmol mol?1) and elevated CO2 (eCO2; 650 μmol mol?1) on noninfected and BYDV‐infected wheat. Using a RT‐qPCR technique, we measured virus titre from aCO2 and eCO2 treatments. BYDV titre increased significantly by 36.8% in leaves of wheat grown under eCO2 conditions compared to aCO2. Plant growth parameters including height, tiller number, leaf area and biomass were generally higher in plants exposed to higher CO2 levels but increased growth did not explain the increase in BYDV titre in these plants. High virus titre in plants has been shown to have a significant negative effect on plant yield and causes earlier and more pronounced symptom expression increasing the probability of virus spread by insects. The combination of these factors could negatively impact food production in Australia and worldwide under future climate conditions. This is the first quantitative evidence that BYDV titre increases in plants grown under elevated CO2 levels. 相似文献
19.
Here, we report the first‐ever measurements of light CO2 respiration rate (CRR) by seaweeds. We measured the influence of temperature (15–25°C) and light (irradiance from 60 to 670 μmol · m?2 · s?1) on the light CCR of two subtropical seaweed species, and measured the CRR of seven different seaweed species under the same light (150 μmol · m?2 · s?1) and temperature (25°C). There was little effect of irradiance on light CRR, but there was an effect of temperature. Across the seven species light CRR was similar to OCR (oxygen consumption rate in the dark), with the exception of a single species. The outlier species was a coralline alga, and the higher light CRR was probably driven by calcification. CRR could be estimated from OCR, as well as carbon photosynthetic rates from oxygen photosynthetic rates, which suggests that previous studies have probably provided good estimations of gross photosynthesis for seaweeds. 相似文献
20.
《African Journal of Aquatic Science》2013,38(3):331-337
The effect of various macroalgal diets on the growth of grow-out (>20 mm shell length) South African abalone Haliotis midae was investigated on a commercial abalone farm. The experiment consisted of four treatments: fresh kelp blades (Ecklonia maxima (Osbeck) Papenfuss) (c. 10% protein); farmed, protein-enriched Ulva lactuca Linnaeus (c. 26% protein) grown in aquaculture effluent; wild U. lactuca (c. 20% protein); and a combination diet of kelp blades + farmed U. lactuca. Abalone grew best on the combination diet (0.423 ± 0.02% weight d?1 SGR [specific growth rate]; 59.593 ± 0.02 ?m d?1 DISL [daily increment in shell length]; 1.093 final CF [condition factor]) followed by the kelp only diet (0.367 ± 0.02% weight d?1 SGR; 53.148 ± 0.02 ?m d?1 DISL; 1.047 final CF), then the farmed, protein-enriched U. lactuca only diet (0.290 ± 0.02% weight d?1 SGR; 42.988 ± 0.03 um d”1 DISL; 1.013 final CF) that in turn outperformed the wild U. lactuca only diet (-0.079 ± 0.01% weight d?1 SGR; 3.745 ± 0.02 ?m d”?1 DISL; 0.812 final CF). The results suggest that protein alone could not have accounted for the differences produced by the varieties of U. lactuca and that the gross energy content is probably important. 相似文献