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1.
Atmospheric changes could strongly influence how terrestrial ecosystems function by altering nutrient cycling. We examined
how the dynamics of nutrient release from leaf litter responded to two important atmospheric changes: rising atmospheric CO2 and tropospheric O3. We evaluated the independent and combined effects of these gases on foliar litter nutrient dynamics in aspen (Populus tremuloides Michx) and birch (Betula papyrifera Marsh)/aspen communities at the Aspen FACE Project in Rhinelander, WI. Naturally senesced leaf litter was incubated in litter
bags in the field for 735 days. Decomposing litter was sampled six times during incubation and was analyzed for carbon, and
both macro (N, P, K, S, Ca, and Mg) and micro (Mn, B, Zn and Cu) nutrient concentrations. Elevated CO2 significantly decreased the initial litter concentrations of N (−10.7%) and B (−14.4%), and increased the concentrations
of K (+23.7%) and P (+19.7%), with no change in the other elements. Elevated O3 significantly decreased the initial litter concentrations of P (−11.2%), S (−8.1%), Ca (−12.1%), and Zn (−19.5%), with no
change in the other elements. Pairing concentration data with litterfall data, we estimated that elevated CO2 significantly increased the fluxes to soil of all nutrients: N (+12.5%), P (+61.0%), K (+67.1%), S (+28.0%), and Mg (+40.7%),
Ca (+44.0%), Cu (+38.9%), Mn (+62.8%), and Zn (+33.1%). Elevated O3 had the opposite effect: N (−22.4%), P (−25.4%), K (−27.2%), S (−23.6%), Ca (−27.6%), Mg (−21.7%), B (−16.2%), Cu (−20.8%),
and Zn (−31.6%). The relative release rates of the nine elements during the incubation was: K ≥ P ≥ mass ≥ Mg ≥ B ≥ Ca ≥ S ≥ N ≥ Mn ≥ Cu ≥ Zn.
Atmospheric changes had little effect on nutrient release rates, except for decreasing Ca and B release under elevated CO2 and decreasing N and Ca release under elevated O3. We conclude that elevated CO2 and elevated O3 will alter nutrient cycling more through effects on litter production, rather than litter nutrient concentrations or release
rates. 相似文献
2.
The changes in photosynthetic efficiency and photosynthetic pigments during dehydration of the resurrection plantSelaginella lepidophylla (from the Chiuhahuan desert, S.W. Texas, USA) were examined under different light conditions. Changes in the photosynthetic
efficiency were deduced from chlorophyll a fluorescence measurements (Fo, Fm, and Fv) and pigment changes were measured by HPLC analysis. A small decrease in Fv/Fm was seen in hydrated stems in high light (650 μmol photons·m−2·s−1) but not in low light (50 μmol photons·m−2·s−1). However, a pronounced decline in Fv/Fm was observed during dehydration in both light treatments, after one to two hours of dehydration. A rise in Fo was observed only after six to ten hours of dehydration. Concomitant with the decrease in photosynthetic efficiency during
dehydration a rise in the xanthophyll zeaxanthin was observed, even in low-light treatments. The increase in zeaxanthin can
be related to previously observed photoprotective non-photochemical quenching of fluorescence in dehydrating stems ofS. lepidophylla. We hypothesize that under dehydrating conditions even low light levels become excessive and zeaxanthin-related photoprotection
is engaged. We speculate that these processes, as well as stem curling and self shading (Eickmeier et al. 1992), serve to
minimize photoinhibitory damage toS. lepidophylla during the process of dehydration. 相似文献
3.
Yuexia Wang Guorong Sun Biao Suo Gang Chen Jianbo Wang Yan Yan 《Acta Physiologiae Plantarum》2008,30(2):143-150
Antioxidant enzymes in chloroplasts and chlorophyll fluorescence parameters of leaves of Puccinellia tenuiflora (Turcz.) scribn.et Merr. under isotonic Na2CO3 and NaCl stresses were studied. Ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities showed a similar increasing
trend and then decreased with the decreasing osmotic potential of culture solution, peaking at −4.74 × 105 Pa under NaCl stress and at −3.40 × 105 Pa under Na2CO3 stress. APX, glutathione transferase and SOD activities were higher under NaCl stress than those under Na2CO3 stress, and higher activities of antioxidant enzymes in chloroplasts were accompanied by lower MDA content under NaCl stress.
F
v/F
m, F
v/F
o and F
v′/F
m′ all initially increased and then decreased with the decreasing osmotic potential of culture solution, while Φ
PSII, qNP and HDR showed a constant increase. F
v/F
m, F
v/F
o, Φ
PSII and qNP under NaCl stress were also shown to be higher than those under Na2CO3 stress. The present study suggested that acidity played an important role in the hurt toPuccinellia tenuiflora seedlings, which was due to higher activities of antioxidant enzymes, qNP and Φ
PSII, and the Na2CO3 resistance to Puccinellia tenuiflora was also supposed to be less than NaCl resistance in present work. 相似文献
4.
Quantitative characteristics of photosynthetic electron transport were evaluated in vivo on the basis of the multi-exponential
analysis of OJIP fluorescence transients induced by saturating actinic light. The OJIP fluorescence curve F(t), measured in Chlamydomonas reinhardtii cells, was transformed into the (1 − F
O/F(t)) × (F
V
/F
M)−1 transient, which is shown to relate to PS 2 closure. We assumed that kinetics of PS 2 closure during OJIP rise reflects time-separated
processes related to the establishment of redox equilibrium at the PS 2 acceptor side (OJ), PQ pool (JI), and beyond Cyt b/f
(IP). Three-exponential fitting was applied to (1 − F
O/F(t)) × (F
V
/F
M)−1 transient to obtain lifetimes and amplitudes of the OJ, JI, and IP components of PS 2 closure, which were used to calculate
overall rates of reduction and re-oxidation of the PS 2 acceptor side, PQ pool, and intermediates beyond Cyt b/f complex.
The results, obtained in the presence of inhibitors, oxidative reagents, and under different stress conditions prove the suggested
model and characterize the introduced parameters as useful indicators of photosynthetic function. 相似文献
5.
Cavender-Bares J 《Photosynthesis research》2007,94(2-3):437-453
Sensitivity to cold and freezing differs between populations within two species of live oaks (Quercus section Virentes Nixon) corresponding to the climates from which they originate. Two populations of Quercus virginiana (originating from North Carolina and north central Florida) and two populations of the sister species, Q. oleoides, (originating from Belize and Costa Rica) were grown under controlled climate regimes simulating tropical and temperate conditions.
Three experiments were conducted in order to test for differentiation in cold and freezing tolerance between the two species
and between the two populations within each species. In the first experiment, divergences in response to cold were tested
for by examining photosystem II (PS II) photosynthetic yield (ΔF/F
m′) and non-photochemical quenching (NPQ) of plants in both growing conditions after short-term exposure to three temperatures
(6, 15 and 30°C) under moderate light (400 μmol m−2 s−1). Without cold acclimation (tropical treatment), the North Carolina population showed the highest photosynthetic yield in
response to chilling temperatures (6°C). Both ecotypes of both species showed maximum ΔF/F
m′ and minimum NPQ at their daytime growth temperatures (30°C and 15°C for the tropical and temperate treatments, respectively).
Under the temperate treatment where plants were allowed to acclimate to cold, the Q. virginiana populations showed greater NPQ under chilling temperatures than Q. oleoides populations, suggesting enhanced mechanisms of photoprotective energy dissipation in the more temperate species. In the second
and third experiments, inter- and intra-specific differentiation in response to freezing was tested for by examining dark-adapted
F
v/F
m before and after overnight freezing cycles. Without cold acclimation, the extent of post-freezing declines in F
v/F
m were dependent on the minimum freezing temperature (0, −2, −5 or −10°C) for both populations in both species. The most marked
declines in F
v/F
m occurred after freezing at −10°C, measured 24 h after freezing. These declines were continuous and irreversible over the
time period. The North Carolina population, however, which represents the northern range limit of Q. virginiana, showed significantly less decline in F
v/F
m than the north central Florida population, which in turn showed a lower decline in Fv/F
m than the two Q. oleoides populations from Belize and Costa Rica. In contrast, after exposure to three months of chilling temperatures (temperate treatment),
the two Q. virginiana populations showed no decline in F
v/F
m after freezing at −10°C, while the two Q. oleoides populations showed declines in F
v/F
m reaching 0.2 and 0.1 for Costa Rica and Belize, respectively. Under warm growth conditions, the two species showed different
F
0 dynamics directly after freezing. The two Q. oleoides populations showed an initial rise in F
0 30 min after freezing, followed by a subsequent decrease, while the Q. virginiana populations showed a continuous decrease in F
0 after freezing. The North Carolina population of Q. virginiana showed a tendency toward deciduousness in response to winter temperatures, dropping 58% of its leaves over the three month
winter period compared to only 6% in the tropical treatment. In contrast, the Florida population dropped 38% of its leaves
during winter. The two populations of the tropical Q. oleoides showed no change in leaf drop during the 3-months winter (10% and 12%) relative to their leaf drop over the same timecourse
in the tropical treatment. These results indicate important ecotypic differences in sensitivity to freezing and cold stress
between the two populations of Q. virginiana as well as between the two species, corresponding to their climates of origin. 相似文献
6.
Rehmannia glutinosa seedlings were pretreated with choline chloride (CC) in concentrations of 0, 0.7, 2.1 and 3.5 mM, and then subjected to drought
and rewatering treatment to study the effects of CC on the generation of reactive oxygen species (O2−, H2O2), lipid peroxidation, proline accumulation, water status and photosynthesis. The results showed that pretreatment with CC
alleviated the inhibition of SOD and APX activity caused by drought stress, and therefore, the rate of O2− production and H2O2 concentration were reduced and lipid peroxidation decreased in pretreated plants. CC pretreatment also accelerated accumulation
of proline, maintained higher Ψw and RWC, deferred leaf water loss during drought stress and retarded the drop in proline
concentration after rewatering. Consequently, drought-induced decreases in Fm/F0, Fv/Fm, ΦPS2, qP, and A and increase in qNP were inhibited and the recovery of photosynthesis after rewatering was quicker in pretreated plants. Although differences
in Fv/Fm, ΦPS2 and qP between treatments were not significant, there was a general trend that the effects of CC increased with the rise of its
concentrations. The data suggested that 2.1 mM of CC be suitable for alleviating lipid peroxidation, promoting proline accumulation,
retarding leaf water loss and improving photosynthesis of R. glutinosa seedlings under drought stress. 相似文献
7.
Teodoro JC Baptista-Neto A Cruz-Hernández IL Hokka CO Badino AC 《Applied microbiology and biotechnology》2006,72(3):450-455
First, the effect of different levels of nitrogen source on clavulanic acid (CA) production was evaluated in batch cultivations utilizing complex culture medium containing glycerol and three different levels of soy protein isolate (SPI). Cellular growth, evaluated in terms of the rheological parameter K, was highest with a SPI concentration of 30 g.L−1 (4.42 g.L−1 N total). However, the highest production of CA (380 mg.L−1) was obtained when an intermediate concentration of 20 g.L−1 of SPI (2.95 g.L−1 total N) was used. To address this, the influences of volumetric flow rate (F) and glycerol concentration in the complex feed medium (CsF) in fed-batch cultivations were investigated. The best experimental condition for CA production was F=0.01 L.h−1 and CsF=120 g.L−1, and under these conditions maximum CA production was practically twice that obtained in the batch cultivation. A single empirical equation was proposed to relate maximum CA production with F and CsF in fed-batch experiments. 相似文献
8.
Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological
mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NPmax), maximum efficiency of photosystem II [variable fluorescence (F
v)/maximum fluorescence yield (F
m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NPmax did not differ between control (0.2 g N m−2 year−1) and high N (3.0 g N m−2 year−1), but was higher in the mid N treatment (1.5 g N m−2 year−1). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F
v/F
m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had
no significant effect on NPmax or F
v/F
m. Addition of 2 g S m−2 year−1 showed a weak negative effect on NPmax and F
v/F
m. Our results suggest a unimodal response of NPmax to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g−1. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects
on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences
in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes. 相似文献
9.
Abies faxoniana is a key species in reforestation processes in the southeast of the Qinghai-Tibetan Plateau of China. The changes in growth,
photosynthesis and nutrient status of A. faxoniana seedlings exposed to enhanced ultraviolet-B (UV-B), nitrogen supply and their combination were investigated. The experimental
design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m−2 day−1; enhanced UV-B, 14.33 KJ m−2 day−1) and two nitrogen levels (0; 20 g N m−2). The results indicated that: (1) enhanced UV-B significantly caused a marked decline in growth parameters, net photosynthetic
rate (Pn), photosynthetic pigments and F
v/F
m, (2) supplemental nitrogen supply increased the accumulation of total biomass, Pn, photosynthetic pigments and F
v/F
m under ambient UV-B, whereas supplemental nitrogen supply reduced Pn, and not affect biomass under enhanced UV-B, (3) enhanced
UV-B or nitrogen supply changed the concentration of nutrient elements of various organs. 相似文献
10.
Simultaneous measurements of chlorophyll (Chl) fluorescence and CO2 assimilation (A) in Vicia faba leaves were taken during the first weeks of growth to evaluate the protective effect of 24-epibrassinolide (EBR) against
damage caused by the application of the herbicide terbutryn (Terb) at pre-emergence. V. faba seeds were incubated for 24 h in EBR solutions (2 × 10−6 or 2 × 10−5 mM) and immediately sown. Terb was applied at recommended doses (1.47 or 1.96 kg ha−1) at pre-emergence. The highest dose of Terb strongly decreased CO2 assimilation, the maximum quantum yield of PSII photochemistry in the dark-adapted state (F
V/F
M), the nonphotochemical quenching (NPQ), and the effective quantum yield (ΔF/F′M) during the first 3–4 weeks after plant emergence. Moreover, Terb increased the basal quantum yield of nonphotochemical processes
(F
0/F
M), the degree of reaction center closure (1 − q
p), and the fraction of light absorbed in PSII antennae that was dissipated via thermal energy dissipation in the antennae
(1 − F′V/F′M). The herbicide also significantly reduced plant growth at the end of the experiment as well as plant length, dry weight,
and number of leaves. The application of EBR to V. faba seeds before sowing strongly diminished the effect of Terb on fluorescence parameters and CO2 assimilation, which recovered 13 days after plant emergence and showed values similar to those of control plants. The protective
effect of EBR on CO2 assimilation was detected at a photosynthetic photon flux density (PFD) of 650 μmol m−2 s−1 and the effect on ΔF/F′M and photosynthetic electron transport (J) was detected under actinic lightings up to 1750 μmol m−2 s−1. The highest dose of EBR also counteracted the decrease in plant growth caused by Terb, and plants registered the same growth
values as controls. 相似文献
11.
Erika S. Zavaleta 《Plant Ecology》2006,184(1):53-63
Accelerating invasion of grasslands by woody species is a widespread global phenomenon. The native shrub Baccharis pilularis has recently increased in abundance in some California grasslands, with large local community and ecosystem effects. I investigated potential contributions of (1) future global climate and atmospheric changes and (2) variation in moisture and nutrient availability to increased Baccharis germination and early establishment rates. I examined responses of Baccharis seeds and seedlings to simulated warming (+ 1−2 °C) and elevated CO2 (+ 300 ppm) in a 2-year field experiment. Warming and CO2 treatments were applied at ambient and increased water and nitrogen levels chosen to simulate future increases in precipitation (+ 50%) and N deposition (+ 7 gN m−2 y−1). Elevated CO2 and water addition each increased or accelerated germination. Herbivory strongly reduced seedling populations during the winter wet season; drought further reduced seedling survival in the spring. Overall Baccharis survivorship was extremely low (<0.1%) across all treatments, complicating the interpretation of global change effects. 相似文献
12.
Rangaraj Nandakumar Li Chen Suzanne M. D. Rogers 《In vitro cellular & developmental biology. Plant》2007,43(3):187-194
A highly reproducible Agrobacterium-mediated transformation system was developed for the wetland monocot Juncus accuminatus. Three Agrobacterium tumefaciens binary plasmid vectors, LBA4404/pTOK233, EHA105/pCAMBIA1201, and EHA105/pCAMBIA1301 were used. All vectors contained the
35SCaMV promoter driven, intron containing, β-glucuronidase (gus), and hygromycin phosphotransferase (hptII) genes within their T-DNA. After 48 h of cocultivation, 21-d-old seedling derived calli were placed on medium containing
timentin at 400 mg l−1, to eliminate the bacteria. Calli were selected on MS medium containing 40 or 80 mg l−1 hygromycin, for 3 mo. Resistant calli were regenerated and rooted on MS medium containing hygromycin, 5 mg l−1(22.2 μM) of 6-benzylamino-purine (BA) and 0.1 mg l−1(0.54 μM) of alpha-naphthaleneacetic acid (NAA), respectively. Seventy-one transgenic cell culture lines were obtained and
39 plant lines were established in the greenhouse. All the plants were fertile, phenotypically normal, and set viable seed.
Both transient and stable expression of the gus gene were demonstrated by histochemical GUS assays of resistant calli, transgenic leaf, root, inflorescence, seeds, and whole
plants. The integration of gus and hptII genes were confirmed by polymerase chain reaction (PCR) and Southern analysis of both F0 and F1 progenies. The integrated genes segregated to the subsequent generation in Mendelian pattern. To our knowledge, this is the
first report of the generation of transgenic J. accuminatus plants. 相似文献
13.
Commercial farming of the intertidal brown alga Hizikia fusiformis (Harvey) Okamura in China and South Korea in the sea depends on three sources of seedlings: holdfast-derived regenerated
seedlings, young plants from wild population and zygote-derived seedlings. Like many successfully farmed seaweed species,
the sustainable development of Hizikia farming will rely on a stable supply of artificial seedlings via sexual reproduction under controlled conditions. However,
the high rate of detachment of seedlings after transfer to open sea is one of the main obstacles, and has limited large-scale
application of zygote-derived seedlings. To seek the optimal condition for growing seedlings on substratum in land-based tanks
for avoidance of detachment in this investigation, young seedlings were grown in both outdoor tanks exposed directly to sunlight
and in indoor raceway tanks in reduced, filtered sunlight. Results showed that young seedlings, immediately after fertilization,
could withstand a daily fluctuation of direct solar irradiance up to a level of 1800 μmol photons m−2 s−1, and maintained a faster growth rate than seedlings grown in indoor tanks. Detailed experiments by use of chlorophyll fluorescence
measurements further demonstrated that the overnight (12 h) recovery of optimal fluorescence quantum yield (Fv/Fm) of seedlings after 1 h treatment at 40°C was 98%, and the 48 h recovery of Fv/Fm of seedlings after 1 h exposure to 1800 μmol m−2 s−1 was 92%. Forty-one-day-old seedlings showed no significant decrease of optimal fluorescence quantum yield at salinity ranging
from 30 to 5 ppt for a treatment up to 17 h. Six-hour desiccation treatment did not have any influence on the optimal fluorescence
quantum yield. Exposure to 18 mmol L−1 sodium hypochlorite for 10 min did not damage the PSII efficiency, and thus could be used to remove epiphytic algae. The
strong tolerance of young seedlings to high temperature, high irradiance, low salinity and desiccation found in this investigation
supports the view that mass production of Hizikia seedlings should be performed in ambient light and temperature instead of in shaded greenhouse tanks. 相似文献
14.
Y. Kitaya L. Xiao A. Masuda T. Ozawa M. Tsuda K. Omasa 《Journal of applied phycology》2008,20(5):737-742
Symbiotic dinoflagellates of the species Amphidinium are expected to be pharmaceutically useful microalgae because they produce antitumor macrolides. A microalgae production
system with a large number of cells at a high density has been developed for the efficient production of macrolide compounds.
In the present study, the effects of culture conditions on the cellular growth rate of dinoflagellates were investigated to
determine the optimum culture conditions for obtaining high yields of microalgae. Amphidinium species was cultured under conditions with six temperature levels (21–35°C), six levels of photosynthetic photon flux density
(15–70 μmol photons m−2 s−1), three levels of CO2 concentration (0.02–0.1%), and three levels of O2 concentration (0.2–21%). The number of cells cultured in a certain volume of solution was monitored microscopically and the
cellular growth rate was expressed as the specific growth rate. The maximum specific growth rate was 0.022 h−1 at a temperature of 26°C and O2 concentration of 5%, and the specific growth rate was saturated at a CO2 concentration of 0.05%, a photosynthetic photon flux density of 35 μmol photons m−2 s−1 and a photoperiod of 12 h day−1 upon increasing each environmental parameter. The results demonstrate that Amphidinium species can multiply efficiently under conditions of relatively low light intensity and low O2 concentration. 相似文献
15.
Influence of boron on somatic embryogenesis in papaya (Carica papaya L.) cv. Honey Dew was investigated. Immature zygotic embryos were grown in the induction medium containing Murashige and
Skoog basal salts, with B5 vitamins, picloram (1 mg dm−3) or 2,4-dichlorophenoxy acetic acid (2 mg dm−3) and different concentrations of boric acid (30 to 500 mg dm−3). Maximum somatic embryo initiation was observed at 62 mg dm−3 boric acid irrespective of the growth regulator used. The cotyledonary stage somatic embryos were germinated on MS basal
medium devoid of growth regulators. The regenerated plantlets were hardened under greenhouse conditions and transferred to
field.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Philip G. Oguntunde 《Plant and Soil》2005,278(1-2):371-383
Cassava (Manihot esculenta Crantz), a perennial woody shrub, is known to be highly productive under favourable conditions and produce reasonably well
under adverse conditions where other crops fail. Using constant heat sap flow sensors, sap flow density (F
d
) of cassava was monitored for 10 days in December 2002. Sap flow was highly correlated (R
2
=0.72, P<0.05) to incoming solar radiation (R
s) than to other climatic factors. Using cross-correlation analysis, no time shift was detected between F
d
and solar radiation, whereas vapour pressure deficit (VPD) lags F
d
by 110 min. Solar radiation and VPD together explained 83% of diurnal variation in sap flow. Whole-plant transpiration ranged
from 0.8 to 1.2 mm day−1 and daily canopy conductance (g
c), computed based on the inverted Penman–Monteith model, varied between 0.7 and 2.1 mm s−1 (mean = 1.4 ± 0.5 mm s−1). For the measurement period, characterized by high evaporative demand coupled with low available soil water, transpiration
accounted for 21% of the available energy and was only able to meet 24% of the atmospheric water demand. Average decoupling
factor (Ω) of 0.05±0.02 estimated suggested that a 10% change in g
c may lead to more than 9% change in transpiration which further supports the notion that stomata play significant role in
regulating cassava water use compared to other known mechanisms. Beyond light saturation (R
s
>300 W m−2) and at higher VPD (>1.0 kPa), wind effects on the canopy transpiration under water stress condition were low, while VPD
explains 94% of the observed variance in daily canopy conductance. 相似文献
17.
Jiří Masojídek Jiří Kopecký Luca Giannelli Giuseppe Torzillo 《Journal of industrial microbiology & biotechnology》2011,38(2):307-317
This work aims to: (1) correlate photochemical activity and productivity, (2) characterize the flow pattern of culture layers
and (3) determine a range of biomass densities for high productivity of the freshwater microalga Chlorella spp., grown outdoors in thin-layer cascade units. Biomass density, irradiance inside culture, pigment content and productivity
were measured in the microalgae cultures. Chlorophyll-fluorescence quenching was monitored in situ (using saturation-pulse
method) to estimate photochemical activities. Photobiochemical activities and growth parameters were studied in cultures of
biomass density between 1 and 47 g L−1. Fluorescence measurements showed that diluted cultures (1–2 g DW L−1) experienced significant photostress due to inhibition of electron transport in the PSII complex. The highest photochemical
activities were achieved in cultures of 6.5–12.5 g DW L−1, which gave a maximum daylight productivity of up to 55 g dry biomass m−2 day−1. A midday depression of maximum PSII photochemical yield (F
v/F
m) of 20–30% compared with morning values in these cultures proved to be compatible with well-performing cultures. Lower or
higher depression of F
v/F
m indicated low-light acclimated or photoinhibited cultures, respectively. A hydrodynamic model of the culture demonstrated
highly turbulent flow allowing rapid light/dark cycles (with frequency of 0.5 s−1) which possibly match the turnover of the photosynthetic apparatus. These results are important from a biotechnological point
of view for optimisation of growth of outdoor microalgae mass cultures under various climatic conditions. 相似文献
18.
M. Angélica Casanova-Katny Gustavo E. Zúñiga Luis J. Corcuera Leon Bravo Miren Alberdi 《Polar Biology》2010,33(4):477-483
Primary photochemistry of photosystem II (F
v/F
m) of the Antarctic hair grass Deschampsia antarctica growing in the field (Robert Island, Maritime Antarctic) and in the laboratory was studied. Laboratory plants were grown
at a photosynthetic photon flux density (PPFD) of 180 μmol m−2 s−1 and an optimal temperature (13 ± 1.5°C) for net photosynthesis. Subsequently, two groups of plants were exposed to low temperature
(4 ± 1.5°C day/night) under two levels of PPFD (180 and 800 μmol m−2 s−1) and a control group was kept at 13 ± 1.5°C and PPFD of 800 μmol m−2 s−1. Chlorophyll fluorescence was measured during several days in field plants and weekly in the laboratory plants. Statistically
significant differences were found in F
v/F
m (=0.75–0.83), F
0 and F
m values of field plants over the measurement period between days with contrasting irradiances and temperature levels, suggesting
that plants in the field show high photosynthetic efficiency. Laboratory plants under controlled conditions and exposed to
low temperature under two light conditions showed significantly lower F
v/F
m and F
m. Moreover, they presented significantly less chlorophyll and carotenoid content than field plants. The differences in the
performance of the photosynthetic apparatus between field- and laboratory-grown plants indicate that measurements performed
in ex situ plants should be interpreted with caution. 相似文献
19.
Chunhui Cao Shichun Sun Xuekui Wang Wenling Liu Ying Liang 《Journal of applied phycology》2011,23(6):1039-1043
Experimental ecology methods and chlorophyll fluorescence technology were used to study the effects of different concentrations
of manganese (10−12– 10−4 mol L−1) on the growth, photosystem II and superoxide dismutase (SOD) activity of Amphidinium sp. MACC/D31. The results showed that manganese had a significant effect on the growth rate, fluorescence parameters (maximal
photochemical efficiency of PSII (F
v
/F
m
), photochemical quenching (qP) and non-photochemical quenching (NPQ)) in the exponential stage (days 1–3) and SOD activity
of Amphidinium sp. (P < 0.05). F
v/F
m in the exponential stage in 10−12 mol L−1 manganese concentration was significantly lower whilst qP and NPQ significantly higher than those in the other concentrations.
F
v
/F
m
(days 6–9) in 10−4 mol L−1 manganese was significantly higher than those in the other concentrations. F
v
/F
m
(days 3–6) increased with increased concentration of manganese from 10−12 to 10−4 mol L−1. The values of qP and NPQ decreased with decreased concentrations of manganese, except for those in days 4–6. F
v
/F
m
under each concentration increased earlier and decreased later with culture stage whilst NPQ decreased earlier and increased
later. The SOD activity increased with increased concentration of manganese from 10−12 to 10−8 mol L−1. The SOD activity in 10−4 mol L−1 manganese was significantly higher than those in the other concentrations and in 10−12 mol L−1 manganese, it was significantly lower than those in the other concentrations. 相似文献
20.
Hwang HS Lee SH Baek YM Kim SW Jeong YK Yun JW 《Applied microbiology and biotechnology》2008,78(3):419-429
In the present study, optimum culture conditions for the production of extracellular polysaccharides (EPS) in submerged culture
of an edible mushroom, Laetiporus sulphureus var. miniatus and their stimulatory effects on insulinoma cell (RINm5F) proliferation and insulin secretion were investigated. The maximum
mycelial growth (4.1 g l−1) and EPS production (0.6 g l−1) in submerged flask culture were achieved in a medium containing 30 g l−1 maltose, 2 g l−1 soy peptone, and 2 mM MnSO4·5H2O at an initial pH 2.0 and temperature 25°C. In the stirred-tank fermenter under optimized medium, the concentrations of mycelial
biomass and EPS reached a maximum level of 8.1 and 3.9 g l−1, respectively. Interestingly, supplementation of deep sea water (DSW) into the culture medium significantly increased both
mycelial biomass and EPS production by 4- and 6.7-fold at 70% (v/v) DSW medium, respectively. The EPS were proved to be glucose-rich polysaccharides and were able to increase proliferation
and insulin secretary function of rat insulinoma RINm5F cells, in a dose-dependent manner. In addition, EPS also strikingly
reduced the streptozotocin-induced apoptosis in RINm5F cells indicating the mode of the cytoprotective role of EPS on RINm5F
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