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1.
Masahiro Yamaguchi Makoto Watanabe Mayumi Iwasaki Chikako Tabe Hideyuki Matsumura Yoshihisa Kohno Takeshi Izuta 《Trees - Structure and Function》2007,21(6):707-718
To obtain the basic data for evaluating the critical level of ozone (O3) to protect Japanese deciduous broad-leaved forest tree species, the growth and photosynthetic responses of Fagus crenata seedlings to O3 under different nitrogen (N) loads were investigated. The seedlings were grown in potted andisol supplied with N as NH4NO3 solution at 0, 20 or 50 kg ha−1 year−1 and were exposed to charcoal-filtered air or O3 at 1.0, 1.5 and 2.0 times the ambient concentration for two growing seasons. The interactive effect of O3 and N load on the whole-plant dry mass of the seedlings at the end of the second growing season was significant. The O3-induced reduction in the whole-plant dry mass of the seedlings was greater in the relatively high N treatment than that in
the low N treatment. This interactive effect was mainly due to the difference in the degree of O3-induced reduction in net photosynthesis among the N treatments. The degree of O3-induced reduction in N availability to photosynthesis was greater in the relatively high N treatment than that in the low
N treatment. In conclusion, the sensitivity of growth and photosynthetic parameters of F. crenata seedlings to O3 become high with increasing amounts of N added to the soil. Therefore, N deposition from the atmosphere should be taken into
account to evaluate the critical level of O3 to protect Japanese deciduous broad-leaved forest tree species. 相似文献
2.
Effects of ozone exposure on sub-tropical evergreen Cinnamomum camphora seedlings grown in different nitrogen loads 总被引:1,自引:0,他引:1
Zhaozhong Feng Junfeng Niu Weiwei Zhang Xiaoke Wang Fangfang Yao Yuan Tian 《Trees - Structure and Function》2011,25(4):617-625
The present study aims in investigating the individual and combined effects of ozone (O3) exposure and nitrogen (N) load on the growth and photosynthetic characters of Cinnamomum camphora seedlings, a dominant evergreen broadleaf tree species in sub-tropical regions. The seedlings were supplied with N as NH4NO3 solution at 0, 30 and 60 kg ha−1 year−1 (simplified as N0, N30, N60, respectively) and were exposed to ambient O3 concentration (AA) or elevated [O3] (E-O3, AA +60 ppb) for one growth season. E-O3 induced significant negative effects on foliar photosynthesis, including lower photosynthetic rate, reduced carboxylation
efficiency, quantum yield of PSII and photosynthetic pigment contents, despite no effect on growth. In contrast, N load acted
as fertilization effects. Medium N (N30) increased photosynthetic pigments and stem-base diameter growth relative to N0, whereas
high N load (N60) significantly enhanced the growth, photosynthetic pigments, and dark and light action of photosynthesis
of C. camphora seedlings. No significant interactive effects of O3 and N load on the growth, net photosynthetic rate and pigment contents of the seedlings were found, suggesting that N supply
to the soil at ≤60 kg ha−1 year−1 does not significantly change the sensitivity of C. camphora to ozone. 相似文献
3.
Primary leaves of bean (Phaseolus vulgaris L.) seedlings cultivated for 14 days in a growth chamber on complete (control) and phosphate deficient (−P) Knop liquid medium
were used for measurements. The −P leaves were smaller and showed an increased specific leaf area (SLA). Their inorganic phosphate
(Pi) concentration was considerably lowered. They did not show any significant changes in chlorophyll (Chl) (a + b) concentration and in their net CO2 assimilation rate when it was estimated under the conditions close to those of the seedlings growth. Light response curves
of photosynthetic net O2 evolution (P
NO2) of the leaves for the irradiation range up to 500 μmol(photon) m−2 s−1 were determined, using the leaf-disc Clark oxygen electrode. The measurements were taken under high CO2 concentration of about 1 % and O2 concentrations of 21 % or lowered to about 3 % at the beginning of measurement. The results obtained at 21 % O2 and the irradiations close to or higher than those used during the seedlings growth revealed the phosphorus stress suppressive
effect on the leaf net O2 evolution, however, no such effect was observed at lower irradiations. Other estimated parameters of P
NO2 such as: apparent quantum requirement (QRA) and light compensation point (LCP) for the control and −P leaves were similar. However, with a high irradiation and lowered
O2 concentration the rate of P
NO2 for the −P leaves was markedly higher than that for the control, in relation to both the leaf area and leaf fresh mass. This
difference also disappeared at low irradiations, but the estimated reduced QRA values indicate, under those conditions, the increased yield of photosynthetic light reaction, especially in the −P leaves.
The presented results confirm the suggestion that during the initial phase of insufficient phosphate feeding the acclimations
in the light phase of photosynthesis, both structural and functional appear. They correspond, probably, to the increased energy
costs of carbon assimilation under phosphorus stress, e.g. connected with raised difficulties in phosphate uptake and turnover and enhanced photorespiration. Under the experimental
conditions especially advantageous for the dark phase of photosynthesis (saturating CO2 and PAR, low O2 concentration), those acclimations may be manifested as an enhancement of photosynthetic net O2 evolution. 相似文献
4.
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
5.
Akio Takenaka 《Ecological Research》1986,1(2):129-140
Ecophysiological comparisons were made of the growth and photosynthetic characteristics between seedlings of deciduousQuercus serrata and evergreenQuercus myrsinaefolia. Q. myrsinaefolia seedlings naturally occurring in secondary coppice forests showed exponential-like growth in height with age, while sympatricQ. serrata seedlings were considerably smaller in height, their growth being limited by shortage of light. The photosynthetic characteristics
measured under laboratory conditions showed no bases for the differences in growth between the two species on the forest floor:
Light compensation points of the seedlings raised under 5% daylight were almost identical for the two species, being about
6.0 μE·m−2·s−1. Growth analysis of seedlings planted in a coppice forest showed that bothQ. serrata andQ. myrsinaefolia could hardly grow during the summer under the shrub layer, when relative photon flux density (RPFD) was 0.9±0.5%. In the
winter, when RPFD under the leafless canopy increased to 29.3±2.7%, the dry matter production of the evergreen seedlings ofQ. myrsinaefolia was much improved. Current-year seedlings of the species showed NAR of 0.102±0.021 g·dm−2·mo−1 during the winter. Temperature dependency of photosynthesis and increment of leaf temperature by direct solar beam also indicated
active photosynthesis ofQ. myrsinaefolia on the forest floor during the winter. 相似文献
6.
Niels Thomas Eriksen Frederik Kier Riisgård William Stuart Gunther Jens Jørgen Lønsmann Iversen 《Journal of applied phycology》2007,19(2):161-174
Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO2, H2, and N2 were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively.
The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO2 uptake was estimated from the addition of CO2 as acidic titrant and O2 evolution was estimated from titration by H2, which was used to reduce O2 over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O2 evolution and CO2 up-take rates. NH4
+, NO2
−, or NO3
− was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient
growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH4
+ as the nitrogen source and 1.3 when NO3
− was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards
1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree
of reduction of the biomass. When using the titrations of CO2 and H2 into the reactor headspace to estimate the up-take of CO2, the production of O2, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be
estimated, and different growth phases could be identified. 相似文献
7.
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
8.
Kristell Hergoualc’h Ute Skiba Jean-Michel Harmand Catherine Hénault 《Biogeochemistry》2008,89(3):329-345
The objective of this study was to evaluate the effect of N fertilization and the presence of N2 fixing leguminous trees on soil fluxes of greenhouse gases. For a one year period, we measured soil fluxes of nitrous oxide
(N2O), carbon dioxide (CO2) and methane (CH4), related soil parameters (temperature, water-filled pore space, mineral nitrogen content, N mineralization potential) and
litterfall in two highly fertilized (250 kg N ha−1 year−1) coffee cultivation: a monoculture (CM) and a culture shaded by the N2 fixing legume species Inga densiflora (CIn). Nitrogen fertilizer addition significantly influenced N2O emissions with 84% of the annual N2O emitted during the post fertilization periods, and temporarily increased soil respiration and decreased CH4 uptakes. The higher annual N2O emissions from the shaded plantation (5.8 ± 0.3 kg N ha−1 year−1) when compared to that from the monoculture (4.3 ± 0.1 kg N ha−1 year−1) was related to the higher N input through litterfall (246 ± 16 kg N ha−1 year−1) and higher potential soil N mineralization rate (3.7 ± 0.2 mg N kg−1 d.w. d−1) in the shaded cultivation when compared to the monoculture (153 ± 6.8 kg N ha−1 year−1 and 2.2 ± 0.2 mg N kg−1 d.w. d−1). This confirms that the presence of N2 fixing shade trees can increase N2O emissions. Annual CO2 and CH4 fluxes of both systems were similar (8.4 ± 2.6 and 7.5 ± 2.3 t C-CO2 ha−1 year−1, −1.1 ± 1.5 and 3.3 ± 1.1 kg C-CH4 ha−1 year−1, respectively in the CIn and CM plantations) but, unexpectedly increased during the dry season. 相似文献
9.
Aguedo M Gomes N Garcia EE Waché Y Mota M Teixeira JA Belo I 《Biotechnology letters》2005,27(20):1617-1621
Yarrowia lipolytica converts methyl ricinoleate to γ-decalactone, a high-value fruity aroma compound. The highest amount of 3-hydroxy-γ-decalactone
produced by the yeast (263 mg l-1) occurred by increasing the kLa up to 120 h−1 at atmospheric pressure; above it, its concentration decreased, suggesting a predominance of the activity of 3-hydroxyacyl-CoA
dehydrogenase. Cultures were grown under high-pressure, i.e., under increased O2 solubility, but, although growth was accelerated, γ-decalactone production decreased. However, by applying 0.5 MPa during
growth and biotransformation gave increased concentrations of dec−2-en-4-olide and dec-3-en-4-olide (70 mg l−1). 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.
The photosynthetic responses of the tropical tree species Acacia nigrescens Oliv. grown at different atmospheric CO2 concentrations—from sub-ambient to super-ambient—have been studied. Light-saturated rates of net photosynthesis (A
sat) in A. nigrescens, measured after 120 days exposure, increased significantly from sub-ambient (196 μL L−1) to current ambient (386 μL L−1) CO2 growth conditions but did not increase any further as [CO2] became super-ambient (597 μL L−1). Examination of photosynthetic CO2 response curves, leaf nitrogen content, and leaf thickness showed that this acclimation was most likely caused by reduction
in Rubisco activity and a shift towards ribulose-1,5-bisphosphate regeneration-limited photosynthesis, but not a consequence
of changes in mesophyll conductance. Also, measurements of the maximum efficiency of PSII and the carotenoid to chlorophyll
ratio of leaves indicated that it was unlikely that the pattern of A
sat seen was a consequence of growth [CO2] induced stress. Many of the photosynthetic responses examined were not linear with respect to the concentration of CO2 but could be explained by current models of photosynthesis. 相似文献
12.
Gyöngyi Kenesi Hesham M. Shafik Attila W. Kovács Sándor Herodek Mátyás Présing 《Hydrobiologia》2009,623(1):191-202
The aim of this research was to test whether NH4
+ and NO3
− affect the growth, P demand, cell composition and N2 fixation of Cylindrospermopsis raciborskii under P limitation. Experiments were carried out in P-limited (200 μg l−1 PO4-P) chemostat cultures of C. raciborskii using an inflowing medium containing either 4,000 μg l−1 NH4-N, 4,000 μg l−1 NO3-N or no combined N. The results showed the cellular N:P and C:P ratios of C. raciborskii decreased towards the Redfield ratio with increasing dilution rate (D) due to the alleviation of P limitation. The cellular C:N and carotenoids:chlorophyll-a ratios also decreased with D, predominantly as a result of an increase in the chlorophyll-a and N content. The NH4
+ and NO3
− supply reduced the P maintenance cell quota of C. raciborskii. Consequently, the biomass yield of the N2-grown culture was significantly lower. The maximum specific growth rate of N2-grown culture was also the lowest observed. It is suggested that these differences in growth parameters were caused by the
P and energy requirement for heterocyte formation, nitrogenase synthesis and N2 fixation. N2 fixation was partially inhibited by NO3
− and completely inhibited by NH4
+. It was probably repressed through the high N content of cells at high dissolved N concentrations. These results indicate
that C. raciborskii is able to grow faster and maintain a higher biomass under P limitation where a sufficient supply of NH4
+ or NO3
− is maintained. Information gained about the species-specific nutrient and pigment stoichiometry of C. raciborskii could help to access the degree of nutrient limitation in water bodies.
Handling editor: Luigi Naselli-Flores 相似文献
13.
Yosuke Okimoto Akihiro Nose Keizo Ikeda Sakae Agarie Kenzo Oshima Yutaka Tateda Takashi Ishii Dang D. Nhan 《Wetlands Ecology and Management》2008,16(2):155-171
In many coastal areas of South-East Asia, attempts have been made to revive coastal ecosystem by initiating projects that
encourage planting of mangrove trees. Compared to the terrestrial trees, mangrove trees possess a higher carbon fixation capacity.
It becomes a very significant option for clean development mechanism (CDM) program. However, a reliable method to estimate
CO2 fixation capacity of mangrove trees has not been established. Acknowledging the above fact, we decided to set up an estimation
method for the CDM program, using gas exchange analysis to estimate mangrove productivity, we put into consideration the net
CO2 fixation of reforested Kandelia candel (5-, 10-, and 15-year-old stand). This was estimated by gas exchange analysis and growth curve analysis. In growth curve
analysis, we drew a growth curve of a single stand using data of above- and below-ground biomass. In the gas exchange analysis,
we calculated CO2 fixation capacity by (1) measuring respiration rate of each organ of stand and calculating respiratory CO2 emission from above- to below-ground biomass. (2) Measuring the single-leaf photosynthetic rate in response to light intensity
and calculating the photosynthetic CO2 absorption. (3) We also developed a model for the diurnal changes in temperature, and monthly averages based on one-day estimation
of CO2 absorption and emission, which we corrected by this model in order to estimate the net CO2 fixation capacity in response to temperature. Comparing the biomass accumulation of the two methods constructed for the same
forest, the above-ground biomass accumulation of 10-year-old forest (34.3 ton ha−1 yr−1) estimated by gas exchange analysis was closely compared to those of growth curve analysis (26.6 ton ha−1 yr−1), suggesting that the gas exchange analysis was capable of estimating mangrove productivity. The validity of the estimated
CO2 fixation capacity by the gas exchange analysis and the growth curve analysis was also discussed. 相似文献
14.
This study examined the effects of season-long exposure of Chinese pine (Pinus tabulaeformis) to elevated carbon dioxide (CO2) and/or ozone (O3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in
open-top chambers (OTC) were exposed to control (ambient O3, 55 nmol mol−1 + ambient CO2, 350 μmol mol−1, CK), elevated CO2 (ambient O3 + high CO2, 700 μmol mol−1, EC) and elevated O3 (high O3, 80 ± 8 nmol mol−1 + ambient CO2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth
in elevated O3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity
were observed in trees exposed to elevated CO2 concentration compared with control. Elevated O3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees
pre-exposed to elevated CO2 were transferred to elevated O3 (EC–EO) or trees pre-exposed to elevated O3 were transferred to elevated CO2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in
IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles
may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may
cause changes in Chinese pine’s growth.
An erratum to this article can be found at 相似文献
15.
Masahiro Yamaguchi Makoto Watanabe Hideyuki Matsumura Yoshihisa Kohno Takeshi Izuta 《Trees - Structure and Function》2010,24(1):175-184
To clarify the effects of ozone (O3) on nitrogen (N) metabolism in the leaves of Fagus crenata seedlings under different N loads, the combined effects of O3 and N load on N enzyme activity, amino acid profiles and soluble protein concentrations were investigated. The seedlings
were grown in potted andisol supplied with N at 0 (N0), 20 (N20) and 50 kg ha−1 year−1 (N50) and were exposed to charcoal-filtered air or O3 at 1.0, 1.5 and 2.0 times the ambient concentration in open-top chambers from April 2004 to October 2005. The average 24-h
concentrations of O3 during the two growing seasons were 11.8, 42.7, 63.3 and 83.7 ppb, respectively. In July 2005, exposure to O3 did not significantly affect the concentration of total free amino acids and activities of nitrite reductase and glutamine
synthetase in any N treatment. Exposure to O3 significantly increased the relative content of acidic amino acids in all N treatments while it significantly reduced concentration
of total soluble protein (TSP) and ratio of TSP concentration to leaf N concentration in the N50 treatment, but not in the
N0 and N20 treatments. Based on the results obtained in the present study, we concluded that exposure to O3 reduces the allocation of N to soluble protein in addition to O3-induced degradation of protein in the leaves of seedlings grown under a relatively high N load, with the result that the
degree of O3-induced reduction in the soluble protein was greater under a relatively high N load than under a relatively low N load. 相似文献
16.
Effects of elevated CO<Subscript>2</Subscript> and nitrogen on wheat growth and photosynthesis 总被引:1,自引:0,他引:1
The effects of nitrogen [75 and 150 kg (N) ha−1] and elevated CO2 on growth, photosynthetic rate, contents of soluble leaf proteins and activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and nitrate reductase (NR) were studied on wheat (Triticum aestivum L. cv. HD-2285) grown in open top chambers under either ambient (AC) or elevated (EC) CO2 concentration (350 ± 50, 600 ± 50 μmol mol−1) and analyzed at 40, 60 and 90 d after sowing. Plants grown under EC showed greater photosynthetic rate and were taller and attained greater leaf area along with higher total plant dry mass at all growth stages than those grown under AC. Total soluble and Rubisco protein contents decreased under EC but the activation of Rubisco was higher at EC with higher N supply. Nitrogen increased the NR activity whereas EC reduced it. Thus, EC causes increased growth and PN ability per unit uptake of N in wheat plants, even if N is limiting. 相似文献
17.
Jirko Holst Chunyan Liu Nicolas Brüggemann Klaus Butterbach-Bahl Xunhua Zheng Yuesi Wang Shenghui Han Zhisheng Yao Jin Yue Xingguo Han 《Ecosystems》2007,10(4):623-634
Gross rates of N mineralization and nitrification, and soil–atmosphere fluxes of N2O, NO and NO2 were measured at differently grazed and ungrazed steppe grassland sites in the Xilin river catchment, Inner Mongolia, P. R.
China, during the 2004 and 2005 growing season. The experimental sites were a plot ungrazed since 1979 (UG79), a plot ungrazed
since 1999 (UG99), a plot moderately grazed in winter (WG), and an overgrazed plot (OG), all in close vicinity to each other.
Gross rates of N mineralization and nitrification determined at in situ soil moisture and soil temperature conditions were
in a range of 0.5–4.1 mg N kg−1 soil dry weight day−1. In 2005, gross N turnover rates were significantly higher at the UG79 plot than at the UG99 plot, which in turn had significantly
higher gross N turnover rates than the WG and OG plots. The WG and the OG plot were not significantly different in gross ammonification
and in gross nitrification rates. Site differences in SOC content, bulk density and texture could explain only less than 15%
of the observed site differences in gross N turnover rates. N2O and NO
x
flux rates were very low during both growing seasons. No significant differences in N trace gas fluxes were found between
plots. Mean values of N2O fluxes varied between 0.39 and 1.60 μg N2O-N m−2 h−1, equivalent to 0.03–0.14 kg N2O-N ha−1 y−1, and were considerably lower than previously reported for the same region. NO
x
flux rates ranged between 0.16 and 0.48 μg NO
x
-N m−2 h−1, equivalent to 0.01–0.04 kg NO
x
-N ha−1 y−1, respectively. N2O fluxes were significantly correlated with soil temperature and soil moisture. The correlations, however, explained only
less than 20% of the flux variance. 相似文献
18.
To obtain basic information for evaluating critical loads of acid deposition for protecting Japanese beech forests, growth, net photosynthesis and leaf nutrient status of Fagus crenata seedlings grown for two growing seasons in brown forest soil acidified with H2SO4 or HNO3 solution were investigated. The whole-plant dry mass of the seedlings grown in the soil acidified by the addition of H2SO4 or HNO3 solution was significantly less than that of the seedlings grown in the control soil not supplemented with H+ as H2SO4 or HNO3 solution. However, the degrees of reduction in the whole-plant dry mass and net photosynthetic rate of the seedlings grown in the soil acidified by the addition of H+ as H2SO4 solution at 100 mg l–1 on the basis of air-dried soil volume (S-100 treatment) were greater than those of the seedlings grown in the soil acidified by the addition of H+ as HNO3 solution at 100 mg l–1 (N-100 treatment). The concentrations of Al and Mn in the leaves of the seedlings grown in the S-100 treatment were significantly higher than those in the N-100 treatment. A positive correlation was obtained between the molar ratio of (Ca+Mg+K)/(Al+Mn) in the soil solution and the relative whole-plant dry mass of the seedlings grown in the acidified soils to that of the seedlings grown in the control soil. Based on the results, we concluded that the negative effects of soil acidification due to sulfate deposition are greater than those of soil acidification due to nitrate deposition on growth, net photosynthesis and leaf nutrient status of F. crenata, and that the molar ratio of (Ca+Mg+K)/(Al+Mn) in soil solution is a suitable soil parameter for evaluating critical loads of acid deposition in efforts to protect F. crenata forests in Japan. 相似文献
19.
Microcoleus chthonoplastes constitutes one of the dominant microorganisms in intertidal microbial mat communities. In the laboratory, the effects of
repeated daily exposure to ultraviolet radiation (16:8 light:dark cycle) was investigated in unicyanobacterial cultures isolated
from three different localities (Baltic Sea = WW6; North Sea = STO and Brittany = BRE). Photosynthesis and growth were measured
in time series (12–15 days) while UV-absorbing mycosporine-like amino acids (MAAs) and cellular integrity were determined
after 12 and 3 days exposure to three radiation treatments [PAR (22 μmol photon m−2 s−1) = P; PAR + UV-A (8 W m−2) = PA; PAR + UV-A + UV-B (0.4 W m−2) = PAB]. Isolate-specific responses to UVR were observed. The proximate response to radiation stress after 1-day treatment
showed that isolate WW6 was the most sensitive to UVR. However, repeated exposure to radiation stress indicated that photosynthetic
efficiency (F
v/F
m) of WW6 acclimated to UVR. Conversely, although photosynthesis in STO exhibited lower reduction in F
v/F
m during the first day, the values declined over time. The BRE isolate was the most tolerant to radiation stress with the lowest
reduction in F
v/F
m sustained over time. While photosynthetic efficiencies of different isolates were able to acclimate to UVR, growth did not.
The discrepancy seems to be due to the higher cell density used for photosynthesis compared to the growth measurement. Apparently,
the cell density used for photosynthesis was not high enough to offer self-shading protection because cellular damage was
also observed in those filaments under UVR. Most likely, the UVR acclimation of photosynthesis reflects predominantly the
performance of the surviving cells within the filaments. Different strategies were observed in MAAs synthesis. Total MAAs
content in WW6 was not significantly different between all the radiation treatments. In contrast, the additional fluence of
UV-A and UV-B significantly increased MAAs synthesis and accumulation in STO while only UV-B fluence significantly increased
MAAs content in BRE. Regardless of the dynamic photosynthetic recovery process and potential UV-protective functions of MAAs,
cellular investigation showed that UV-B significantly contributed to an increased cell mortality in single filaments. In their
natural mat habitat, M. chthonoplastes benefits from closely associated cyanobacteria which are highly UVR-tolerant due to the production of the extracellular UV-sunscreen
scytonemin. 相似文献