共查询到20条相似文献,搜索用时 46 毫秒
1.
V. S. Kuwahara R. Nakajima B. H. R. Othman M. R. M. Kushairi T. Toda 《Coral reefs (Online)》2010,29(3):693-704
Biologically diverse coral-reef ecosystems are both directly and indirectly susceptible to changes in the spectral ultraviolet
radiation (UVR) distribution. The purpose of this study was to (1) measure the variability of UVR and photosynthetically active
radiation (PAR) penetration in the water above coral reefs around the Malaysian peninsula, (2) measure the variability and
distribution of UVR-specific biogeochemical factors, and (3) determine the impact of biogeochemical variability as it affects
the UVR:PAR ratio. Downwelling UVR and PAR irradiance and bio-optically derived biogeochemical factors were measured at 14
coral survey stations around the Malaysian peninsula from August 10–29, 2007. The West Coast was characterized by relatively
shallow mean 10% UV-B (320 nm) penetration (1.68 ± 1.12 m), high chlorophyll (3.00 ± 4.72 μg l−1), high chromophoric dissolved organic matter (CDOM; 6.61 ± 3.31 ppb), high particulate organic carbon (POC; 190.65 ± 97.99 mg m−3), and low dissolved organic carbon (DOC; 1.34 ± 0.65 mg m−3). By contrast, the East Coast was characterized by relatively deep mean 10% UV-B penetration (5.03 ± 2.19 m), low chlorophyll
(0.34 ± 0.22 μg l−1), low CDOM (1.45 ± 0.44 ppb), low POC (103.21 ± 37.93 mg m−3), and relatively high DOC (1.91 ± 1.03 mg m−3). The UVR:PAR ratio was relatively higher on the East Coast relative to the West Coast, suggesting variable concentrations
of UVR-specific absorbing components. At all sites, UVR attenuation coefficients showed significant correlations with CDOM,
but were spatially dependent with regard to chlorophyll a, POC, and DOC. The results suggest that bio-optically significant CDOM and DOC factors are uncoupled in coral-reef communities
of Malaysia. Furthermore, the results support prior studies that show chromophorically active concentrations of DOM and POC
are significantly altering the amount of UVR penetration above coral reefs and may be notable factors in regulating intricate
biogeochemical cycles around benthic coral communities in Malaysia. 相似文献
2.
Penetration of solar ultraviolet radiation into New Zealand lakes: influence of dissolved organic carbon and catchment vegetation 总被引:5,自引:0,他引:5
Eleven lakes in the South Island of New Zealand were sampled in summer 1996. Water column profiles of ultraviolet radiation
(UVR) at four wavelengths and photosynthetically available radiation (PAR) were obtained, along with analyses of dissolved
organic carbon (DOC) concentration, total suspended solids (TSS), and catchment vegetation, including forest and natural grassland.
Downward attenuation coefficients (K
d) and lake water transparency (1/K
d) for UVR were examined in relation to these variables. Consistent with other regions of the world, DOC concentration and
variables related to DOC were the best predictors of UVR penetration. With our data set, we calculated ratios of water column
integrals (RI) of UVR/PAR irradiance, using equations from the literature. At DOC concentrations below 4 g m−3, a progressive increase in RI shows that lakes become increasingly transparent to UVR. We also normalized chromophoric dissolved
organic matter (CDOM) absorption of UVR at 380 nm (a
380) to DOC concentration and found that the UVR-absorbing capacity per unit DOC increases with increasing percentage of forest
in the catchment area. This indicates that not only DOC concentration but also DOC type or composition is important in determining
the transparency of lake water to UVR, and that qualitative differences in DOC are dictated by the type and amount of vegetation
present in the lake's catchment area.
Received: September 18, 2000 / Accepted: December 14, 2000 相似文献
3.
Sunlight penetration through the water column is controlled by the amount and kind of materials dissolved and suspended in
the water. Understanding UV penetration in its complexity is essential for the prediction of the impact of UV radiation on
aquatic ecosystems. However, only limited data are available on the penetration of UVR into shallow waters rich in inorganic
suspended solids and chromophoric dissolved organic matter (CDOM). The same is true for the specific attenuation coefficients
of light-absorbing components at the UV waveband. This study analyses the role of CDOM, algal-free suspended solids and algae
in the formation of underwater UVR and PAR climate in 30 water bodies from clear gravel pit lakes trough the shallow Lake
Balaton to turbid soda pans. Irradiance-depth profiles were obtained at 305, 313, 320 nm (UV-B), 340, 380, 395 nm (UV-A) and
400–700 nm (PAR) with a Biospherical PUV-2500 radiometer. Vertical attenuation coefficients (K
d) were calculated. Water samples were taken for the laboratory measurement of the concentration of light-absorbing components:
algae as chlorophyll a (CHL), chromophoric dissolved organic matter as colour (CDOM), and algal-free suspended solids (TSS-Alg) parallel with the
in situ light measurements. Specific attenuation coefficient values were calculated by multiple regression analysis (n = 140). The obtained specific UV attenuation coefficient values of CHL, CDOM and TSS-Alg made it possible to establish light
attenuation at different wavelengths based on the knowledge of the concentration of these light-absorbing components. 相似文献
4.
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
5.
Absorption measurements from chromophoric dissolved organic matter (CDOM) and their relationships with dissolved organic carbon
(DOC) and fluorescence were studied in Lake Taihu, a large, shallow, subtropical lake in China. Absorption spectra of lake
water samples were measured from 240 nm to 800 nm. Highest values of a(λ), DOC and F
n
(355) occurred near the river inflow to Meiliang Bay and decreased towards the central lake basin. A significant spatial difference
was found between Meiliang Bay and the central lake basin in absorption coefficient, DOC-specific absorption coefficient,
exponential slope coefficient, DOC concentration and fluorescence value. The spatial distribution of CDOM suggested that a
major part of CDOM in the lake was from river input. CDOM absorption coefficients were correlated with DOC over the wavelength
range 280–500 nm, and a(355) was also correlated with F
n
(355), which showed that CDOM absorption could be inferred from DOC and fluorescence measurement. The coefficient of variation
between a(λ) and DOC concentration decreased with increase in wavelength from 240 nm to 800 nm. Furthermore, a significant negative
linear relationship was recorded between S value and CDOM absorption coefficient, as well as DOC-specific absorption coefficient. S value and DOC-specific absorption coefficient were used as a proxy for CDOM composition and source. Accurate CDOM absorption
measurements are very useful in explaining UV attenuation and in developing, validating remote sensing model of water quality
in Lake Taihu. 相似文献
6.
The responses of the early development of Laminaria japonica collected from Kiaochow Bay in China to enhanced ultraviolet-B radiation (UV-B, 280–320 nm) were studied in the laboratory.
The low UV-B radiations (11.7–23.4 J·m−2·d−1) had no significant effects on zoospores attachment, but when the UV-B dose > 35.1 J·m−2·d−1 the attachment decreased significantly compared with the control. Germination of embryospores was >93% under the low (11.7–35.1
J·m−2·d−1) doses, and in the range of 78.5%–88.5% under the high (46.8–70.2 J·m−2·d−1) UV-B doses, indicating a significant radiation effect. Under the higher UV-B exposure (35.1–70.2 J·m−2·d−1), all of the few gametophytes formed from embryospores died 120 h post-release. After exposure to the low UV-B radiation
(11.7–23.4 J·m−2·d−1), the formation of sporophytes decreased and the female gametophyte clones increased compared with the control. However,
the sex ratio and the relative growth of female gametophytes/sporophytes had not significantly changed. According to the results,
enhanced UV-B radiation has a significant effect on the early development of L. japonica under laboratory conditions, suggesting that the UV-B radiation could not be overlooked as one of the important environmental
factors influencing the ontogeny of macroalgae living in marine ecosystems.
Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-05-0597) and National Natural Science
Foundation of China (Grant No. 30270258) 相似文献
7.
The carbon-flux via algal bloom events involves bacteria as an important mediator. The present study, carried out during the
spring inter-monsoon month of April 2008 onboard CRV Sagar Manjusha-06 in the Eastern Arabian Sea, addresses the bloom-specific
flow of carbon to bacteria via chromophoric dissolved organic matter (CDOM). Eleven stations monitored were located in the
coastal, shelf and open-ocean areas off Ratnagiri (16°59′N, 73°17′E), Goa (15°30′N, 73°48′E) and Bhatkal (13°58′N, 74°33′E)
coasts. Visible bloom of “saw-dust” color in the Ratnagiri shelf were microscopically examined and the presence of cyanobacteria
Trichodesmium erythraeum and T. thieabautii with cell concentrations as high as 3.05 × 106 trichomes L−1 was recorded. Total bacterial counts (TBC) varied between 94.09 × 108 cells L−1 in the bloom to 1.34 × 108 cells L−1 in the non-bloom area. Chromophoric dissolved organic matter (CDOM) concentrations averaged 2.27 ± 3.02 m−1 (absorption coefficient 325 nm) in the bloom to 0.28 ± 0.07 m−1 in the non-bloom waters respectively. CDOM composition varied from a higher molecular size with lower aromaticity in the
bloom to lower molecular size and increased aromaticity in the non-bloom areas respectively. Strong positive relationship
of TBC with Chlorophyll a (R
2 = 0.65, p < 0.01) and CDOM concentrations (R
2 = 0.8373, p = 0.01) in the bloom area indicated hydrolysis and/or uptake of CDOM by bacteria. Absorption by mycosporine-like amino acid
palythene (λ
max = 360 nm) was recorded in the filtrate of bloom. Morphotypes of Trichodesmium-associated bacteria revealed a higher frequency of Gram-positive rods. The role of bacteria in relation to changing CDOM
nature and as a factor in affecting oxygen content of the water column is discussed in context of the Arabian Sea. 相似文献
8.
M. K. Pradhan L. Nayak P. N. Joshi P. K. Mohapatra L. Patro B. Biswal U. C. Biswal 《Photosynthetica》2008,46(3):370-377
Alterations in photosynthetic capacity of primary leaves of wheat seedlings in response to ultraviolet-B (UV-B; 280–320 nm;
60 μmol m−2 s−1) exposure alone and in combination with photosynthetically active radiation (PAR; 400–800 nm; 200 μmol m−2 s−1) during different phases of leaf growth and development were assessed. UV-B exposure resulted in a phase-dependent differential
loss in photosynthetic pigments, photochemical potential, photosystem 2 (PS2) quantum yield, and in vivo O2 evolution. UV-B exposure induced maximum damage to the photosynthetic apparatus during senescence phase of development. The
damages were partially alleviated when UV-B exposure was accompanied by PAR. UV-B induced an enhancement in accumulation of
flavonoids during all phases of development while it caused a decline in anthocyanin content during senescence. The differential
changes in these parameters demonstrated the adaptation ability of leaves to UV-B stress during all phases of development
and the ability was modified in UV-B+ PAR exposed samples. 相似文献
9.
The influence of ultraviolet-B radiation on the growth, pigment production and chlorophyll fluorescence of Norway spruce seedlings 总被引:3,自引:0,他引:3
Norway spruce (Picea abies (L.)Karst.) from seven seed sources was grown in a greenhouse with 8.3 and 14.7 kJ·m−2·d−1 m UV-BBE (biologically effective UV-B: 280–320 nm) irradiation, and with no supplemental irradiation as control. The seedlings total
biomass (dry weight) and shoot growth decreased with high UV-B treatment but spruce from low elevation seed sources were more
affected. The seedlings grown at the highest UV-B irradiance (14.7 kJ·m−2·d−1) showed from 5 to 38% inhibition of total biomass and 15 to 70 % shoot growth inhibition. Norway spruce populations from
higher altitude seed sources manifested greater tolerance to UV-B radiation compared to plants from low altitudes. Changes
in phospholipids and protective pigments were also determined. The plants grown at the lower UV-B irradiance (8.3 kJ·m−2·d−1) showed greater ability to concentrations UV-B-absorbing pigments then control plants. Chlorophyll a fluorescence parameter
Rfd, (Rfd=(Fm-Fs)/Fs) showed a significant decrease in needles of UV-B treated plants and this correlated with the altitude of seed source. Exposure
to UV-B affect levels of the ratio of variable to maximum fluorescence (Fv/Fm). Results from this study suggest that the response to increased levels of UV-B radiation is depended upon the ecotypic differentiation
of Norway spruce and involved changes in metabolites in plant tissues. 相似文献
10.
The study comprises a data set of CTD, optical properties—K
0(PAR), c
p, a(PAR), b(PAR)—and optical constituents—Chl a, SPM, CDOM—from 72 shelf and off-shelf stations in the Faroe Islands (62°N, 7°W) North East Atlantic, in early spring 2005.
Results showed that shelf waters surrounding the islands were cold and low saline, whereas off-shelf waters were warmer (~1°C)
and more saline (~0.05) PSU. A pronounced oceanographic front separated the two waters, and diffuse light attenuation K
0(PAR), beam attenuation c
p, Chl a, absorption a(PAR), and scattering coefficient b(PAR) were all significantly higher on the shelf. Analyses showed that off-shelf light attenuation K
0(PAR) was governed by Chl a, shown by a high (r
2 = 0.64) Chl a–K
0(PAR) correlation, whereas light attenuation on the shelf was governed by both Chl a, SPM, and CDOM in combination. A Chl a specific diffuse attenuation coefficient
K0* ( \textPAR ) K_{0}^{*} \left( {\text{PAR}} \right) of 0.056 (m2 mg−1 Chl a) and a Chl a specific beam attenuation (
c\textp* c_{\text{p}}^{*} ) of 0.27 (m2 mg−1 Chl a) coefficients were derived for the off-shelf. It is pointed out that Chl a is the single variable that changes over time as no rivers with high SPM and CDOM enter the shelf area. Data were obtained
in early spring, and Chl a concentrations were low ~0.5 mg Chl a m−3. Spring bloom Chl a are about 10 mg Chl a m−3 and estimations showed that shelf K
0(PAR) will increase about 5 times and beam attenuation about 10 times. The Faroe Islands shelf–off-shelf waters is a clear
example where physical conditions maintain some clear differences in optical properties and optical constituents. The complete
data set is enclosed. 相似文献
11.
Using Satellite Remote Sensing to Estimate the Colored Dissolved Organic Matter Absorption Coefficient in Lakes 总被引:4,自引:0,他引:4
Tiit Kutser Donald C. Pierson Lars Tranvik Anu Reinart Sebastian Sobek Kari Kallio 《Ecosystems》2005,8(6):709-720
Given the importance of colored dissolved organic matter (CDOM) for the structure and function of lake ecosystems, a method
that could estimate the amount of CDOM in lake waters over large geographic areas would be highly desirable. Satellite remote
sensing has the potential to resolve this problem. We carried out model simulations to evaluate the suitability of different
satellite sensors (Landsat, IKONOS, and the Advanced land Imager [ALI]) to map the amount of CDOM in concentration ranges
that occur in boreal lakes of the Nordic countries. The results showed that the 8-bit radiometric resolution of Landsat 7
is not adequate when absorption by CDOM at 420 nm is higher than 3 m−1. On the other hand, the 16-bit radiometric resolution of ALI, a prototype of the next generation of Landsat, is suitable
for mapping CDOM in a wider range of concentrations. An ALI image of southern Finland was acquired on 14, July 2002 and in
situ measurements were carried out in 15 lakes (18 stations). The results showed that there is a high correlation (R2 = 0.84) between the 565 nm/660 nm ALI band ratio and the CDOM absorption coefficient in lakes. Analysis of 245 lakes in the
acquired satellite image showed a normal distribution of CDOM concentration among the lakes. However, the size distribution
of lakes was highly skewed toward small lakes, resulting in the CDOM concentration per unit lake area being skewed toward
high values. We showed that remote sensing enables synoptic monitoring of the CDOM concentration in a large number of lakes
and thus enables scaling up to the level of large ecosystems and biomes. 相似文献
12.
Pre-matured florets of Benibana, a cultivar of saffron thistle (Carthamus tinctorius L.) was irradiated with UV-B (280–320 nm) or UV-C (254 nm) light for 48 h at 23±1 °C and the influence of UV-light on carthamin
accumulation and floret elongation was investigated. UV-C light enhances carthamin accumulation most prominently, showing
a specific value of 52.3 nmol carthamin·dm−3·h−1·25μm−2 (13.9 times of control), while it restricts floret elongation by a light-suppression manner (net elongation: 0.058 mm·h−1, one ninth of control). UV-B light is also promotive for the red colour appearance (25.0 nmol carthamin·dm−3·h−1·25 μm−2, 6.7 times of control) with suppressing floret elongation (net elongation: 0.17 mm·h−1, one third of control). Heterogeneous productivity of carthamin was seen in floret tissues after continuous treating under
UV-C light. Carthamin accumulation, heterogeneous carthamin productivity and decrease of floret elongation restraint under
UV-lights are discussed. 相似文献
13.
Stephen A. Diamond Peter C. Trenham Michael J. Adams Blake R. Hossack Roland A. Knapp Stacey L. Stark David Bradford P. Stephen Corn Ken Czarnowski Paul D. Brooks Dan Fagre Bob Breen Naomi E. Detenbeck Kathy Tonnessen 《Ecosystems》2005,8(5):462-477
Ultraviolet-B radiation (UV-B, 280–320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia
(Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/Kings Canyon
(Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools,
field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose
estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks
was 19.3 W-h m−2 (range of 3.4–32.1 W-h m−2). The mean dose was lowest in Acadia (13.7 W-h m−2) and highest in Rocky (24.4 W-h m−2). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 μW cm−2 (range 21.4–194.7 μW cm−2) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column
UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L−1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%–87 %. DOC concentration, as well
as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape
reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in
UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B
on aquatic organisms. 相似文献
14.
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
15.
Luz Allende Guillermo Tell Horacio Zagarese Ana Torremorell Gonzalo Pérez José Bustingorry Roberto Escaray Irina Izaguirre 《Hydrobiologia》2009,624(1):45-60
Shallow lakes often alternate between two possible states: one clear with submerged macrophytes, and another one turbid, dominated
by phytoplankton. A third type of shallow lakes, the inorganic turbid, result from high contents of suspended inorganic material,
and is characterized by low phytoplankton biomass and macrophytes absence. In our survey, the structure and photosynthetic
properties (based on 14C method) of phytoplankton were related to environmental conditions in these three types of lakes in the Pampa Plain. The
underwater light climate was characterized. Clear-vegetated lakes were more transparent (K
d 4.5–7.7 m−1), had high DOC concentrations (>45 mg l−1), low phytoplankton Chl a (1.6–2.7 μg l−1) dominated by nanoflagellates. Phytoplankton productivity and photosynthetic efficiency (α ~ 0.03 mgC mgChla
−1 h−1 W−1 m2) were relatively low. Inorganic-turbid lakes showed highest K
d values (59.8–61.4 m−1), lowest phytoplankton densities (dominated by Bacillariophyta), and Chl a ranged from 14.6 to 18.3 μg l−1. Phytoplankton-turbid lakes showed, in general, high K
d (4.9–58.5 m−1) due to their high phytoplankton abundances. These lakes exhibited the highest Chl a values (14.2–125.7 μg l−1), and the highest productivities and efficiencies (maximum 0.56 mgC mgChla
−1 h−1 W−1 m2). Autotrophic picoplankton abundance, dominated by ficocianine-rich picocyanobacteria, differed among the shallow lakes independently
of their type (0.086 × 105–41.7 × 105 cells ml−1). This article provides a complete characterization of phytoplankton structure (all size fractions), and primary production
of the three types of lakes from the Pampa Plain, one of the richest areas in shallow lakes from South America.
Handling editor: J. Padisak 相似文献
16.
Near-isogenic lines of maize varying in their genes for flavonoid biosynthesis were utilized to examine the effects of foliar
flavonoids and nutrient deficiency on maximum net photosynthetic rate (P
N) and chlorophyll (Chl) fluorescence (Fv/Fm) in response to ultraviolet-B (UV-B) radiation. Plants with deficient (30 to 70 % lower N, K, Mn, Fe, and Zn) and sufficient
nutrients were exposed to four irradiation regimes: (1) no UV-B with solar photosynthetically active radiation (PAR), (2) two day shift to ambient artificial UV-B, 8.2–9.5 kJ m−2 d−1 (21–25 mmol m−2 d−1); (3) continuous ambient artificial UV-B; (4) continuous solar UV-B in Hawaii 12–18 kJ m−2 d−1 (32–47 mmol m−2 d−1). The natural ratio of UVB: PAR (0.25–0.40) was maintained in the UV-B treatments. In the adequately fertilized plants, lines
b and lc had higher contents of flavonoids and anthocyanins than did lines hi27 and dta. UV-B induced the accumulation of
foliar flavonoids in lines hi27 and b, but not in the low flavonoid line dta or in the high flavonoid line lc. In plants grown
on deficient relative to adequate nutrients, flavonoid and anthocyanin contents decreased by 30–40 and 40–50 %, respectively,
and Chl a and Chl b contents decreased by 30 and 70 %, respectively. The UV-B treatments did not significantly affect P
N and Fv/Fm in plants grown on sufficient nutrients, except in the low flavonoid lines dta and hi27 in which P
N and Fv/Fm decreased by ∼15 %. P
N, Fv/Fm, and stomatal conductance decreased markedly (20–30 %) in all lines exposed to UV-B when grown on low nutrients. The decrease
in Fv/Fm was 10 % less in higher flavonoid lines b and lc. The photosynthetic apparatus of maize readily tolerated ambient UV-B in
the tropics when plants were adequately fertilized. In contrast, ambient UV-B combined with nutrient deficiency significantly
reduced photosynthesis in this C4 plant. Nutrient deficiency increased the susceptibility of maize to UV-B-induced photoinhibition in part by decreasing the
contents of photoprotective compounds. 相似文献
17.
Ozone depletion is highest during spring and summer in Antarctica, coinciding with the seasonal reproduction of most macroalgae.
Propagules are the life-stage of an alga most susceptible to environmental perturbations therefore, reproductive cells of
three intertidal macroalgal species Adenocystis utricularis (Bory) Skottsberg, Monostroma hariotii Gain, and Porphyra endiviifolium (A and E Gepp) Chamberlain were exposed to photosynthetically active radiation (PAR), PAR + UV-A and PAR + UV-A + UV-B radiation
in the laboratory. During 1, 2, 4, and 8 h of exposure and after 48 h of recovery, photosynthetic efficiency, and DNA damage
were determined. Saturation irradiance of freshly released propagules varied between 33 and 83 μmol photons m−2 s−1 with lowest values in P. endiviifolium and highest values in M. hariotii. Exposure to 22 μmol photons m−2 s−1 PAR significantly reduced photosynthetic efficiency in P. endiviifolium and M. hariotii, but not in A. utricularis. UV radiation (UVR) further decreased the photosynthetic efficiency in all species but all propagules recovered completely
after 48 h. DNA damage was minimal or not existing. Repeated exposure of A. utricularis spores to 4 h of UVR daily did not show any acclimation of photosynthesis to UVR but fully recovered after 20 h. UVR effects
on photosynthesis are shown to be species-specific. Among the tested species, A. utricularis propagules were the most light adapted. Propagules obviously possess good repair and protective mechanisms. Our study indicates
that the applied UV dose has no long-lasting negative effects on the propagules, a precondition for the ecological success
of macroalgal species in the intertidal. 相似文献
18.
Ferdinand Schanz 《Hydrobiologia》1986,134(2):183-192
Spectral light attenuation, from the surface to 20 m, was followed on 15 sunny days and compared with the vertical phytoplankton
distribution. The most penetrating wavelengths lie between 565 and 590 nm. High phytoplankton density causes a rapid loss
of blue light with depth. Consequently the yellow and red regions of the spectrum contain a relatively high proportion of
the light energy present at a particular depth. The vertical attenuation coefficients of monochromatic light Kd(λ) in the 400 to 700 nm region are influenced significantly by the phytoplankton biomass. The specific light attenuation
coefficient for chlorophyll a (kc) is highest below 550 nm (e.g. 450 nm, surface layer: kc = 0.027 m2 · mg−1, n = 14; lowermost layer: kc = 0.044 m2 · mg−1, n = 9). 相似文献
19.
Riitta Tegelberg Satu Turtola Matti Rousi Beat Meier Riitta Julkunen-Tiitto 《Trees - Structure and Function》2006,20(3):299-303
Hybridisation between certain willow species is a common feature leading to novel genotypes varying in growth rate and stress tolerance. The objective of this 4-week study was to investigate the effects of decreased watering, enhanced ultraviolet-B irradiation (UV-BBE, 280–315 nm, 7.2 kJ m−2 day−1) and combined decreased watering and enhanced UV-B irradiation on di- and polyamines in the leaves of Salix myrsinifolia and its hybrid with S. myrsinites. Control plantlets were well-watered and exposed to ambient UV-B irradiation (UV-BBE, 3.6 kJ m−2 day−1). HPLC analyses showed that the constitutive concentrations of soluble di- and polyamines varied markedly between S. myrsinifolia and its hybrids. The degree of responses to treatments also varied: in S. myrsinifolia, concentrations of free putrescine were clearly increased by reduced watering, while in the hybrid willow, change in putrescine was less pronounced and not significant. Results also showed that the increase in putrescine in S. myrsinifolia by reduced watering was mitigated by concurrent enhancement of UV-B irradiation. There were no direct UV-B effects on the soluble polyamines. 相似文献
20.
We report the effect of UV-B radiation (0.8 ± 0.1 mW cm−2) and UV-B radiation supplemented with low-intensity PAR (∼80 μmol photons m−2 s−1) on the photosynthesis, photosynthetic pigments, phosphoglycolipids, oxidative damage, enzymatic antioxidants, and UV-absorbing
compounds in Phormidium tenue, a marine cyanobacterium. UV-B radiation resulted in a decline in photosynthesis and photosynthetic pigments leading to lower
biomass. P. tenue synthesized UV-absorbing compounds like mycosporine-like amino acids (MAAs) and scytonemin in response to UV-B radiation.
Quantity of MAAs and scytonemin was higher when UV-B was supplemented with low-level PAR. UV-B treatment also resulted in
quantitative changes in phosphoglycolipids of the membrane. The UV-B treatment resulted in a slight increase in the level
of peroxidation of cell membrane and very little increase in the activity of superoxide dismutase (SOD). Results indicate
that UV-B affected photosynthesis and that the main protective system was the synthesis of MAAs and scytonemin-like compounds
rather than antioxidant enzymes such as SOD. 相似文献