用便携式光谱仪同步测定和计算光强和光质的新方法

外界光强和光质对植物的影响在植物生理生态研究领域中一直受到高度关注。而测定光强的光量子计不能测定光质; 测定光质的光谱仪不能直接测定光强, 两者均不能同步测定光强和光质。该文作者建立了一个基于光谱仪测定条件的能量与光量子的经验转换公式, 用4只不同波长的窄带发光二极管(LED)光源结合光量子计(LI-190SB)对便携式光谱仪(AvaSpec-ULS2048×64)所获得的光谱进行了快速标定, 实现了用便携式光谱仪同步直接测定光量子通量密度和光质的目的。在自然光照条件下, 采用转换公式计算出光量子通量密度(PPFD)与实测的PPFD之间误差在-2%-5%范围内, 证实了这种方法的可靠性。通过这个新方法, 可以极大地拓宽便携式光谱仪的适用范围: 1)实验室内或野外只需用便携式光谱仪即可对光源及植物生长的光强和光质环境进行同步精确测定和计算; 2)可以计算光谱仪测定范围内任意波长区段的光量子通量密度; 3)无需采用标准光源即可获得绝对辐射(光)通量值。因此, 这项技术在植物生理生态研究领域具有广阔的应用前景。     

A new method to measure and calculate light intensity and light quality simultaneously by using portable spectrometer

The influence of light intensity and light quality on plants is highly concerned in the field of plant physiology and ecology. However, the calibrated quantum meter for measurement of light intensity cannot measure light quality, and vice versa. Here we developed an empirical formula to convert light energy to photon flux density, based on the measurement conditions of spectrometer. Under the guide of the formula, a portable spectrometer (AvaSpec-ULS2048×64) was calibrated by using four narrowband light emitting diode (LEDs) in combination with a calibrated quantum meter (LI-190SB). After calibration of the spectrometer, we can calculate photosynthetic photon flux density (PPFD or PAR) and measure spectrum of radiation flux simultaneously. Under natural light conditions, the errors between measured and calculated PPFDs are in the range from -2% to 5%, indicating the reliability of the method. With this new approach, the application of portable spectrometer can be greatly broadened: 1) the light intensity and quality of light source and plant growth light environment can be obtained simultaneously, 2) PPFD can be obtained within any specified wavelength range, and 3) there is no need to use standard light source to obtain the absolute light/radiation flux of a spectrum measured by spectrometer. In conclusion, this method has potential applications for the study of plant physiology and ecology.     

Solar ultraviolet radiation affects the activity of ribulose-1,5-bisphosphate carboxylase-oxygenase and the composition of photosynthetic and xanthophyll cycle pigments in the intertidal green alga Ulva lactuca L

The effect of solar UV radiation on the physiology of the intertidal green macroalga Ulva lactuca L. was investigated. A natural Ulva community at the shore of Helgoland was covered with screening foils, excluding UV-B or UV-B + UV-A from the solar spectrum. In the sampled material, changes in the activity and concentration of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), and the concentration of photosynthetic and xanthophyll cycle pigments were determined. Exclusion of UV radiation from the natural solar spectrum resulted in an elevated overall activity of Rubisco, related to an increase in its cellular concentration. Among the photosynthetic pigments, lutein concentration was substantially elevated under UV exclusion. In addition, marked UV effects on the xanthophyll cycle were found: exclusion of solar UV radiation (and particularly UV-B) resulted in an increased ratio of zeaxanthin concentration to the total xanthophyll content, indicating adverse effects of UV-B on the efficiency of photoprotection under high irradiances of photosynthetically active radiation. The results confirm a marked impact of present UV-B levels on macroalgal physiology under field conditions.     

Artificial and solar UV radiation induces strand breaks and cyclobutane pyrimidine dimers in Bacillus subtilis spore DNA

The loss of stratospheric ozone and the accompanying increase in solar UV flux have led to concerns regarding decreases in global microbial productivity. Central to understanding this process is determining the types and amounts of DNA damage in microbes caused by solar UV irradiation. While UV irradiation of dormant Bacillus subtilis endospores results mainly in formation of the "spore photoproduct" 5-thyminyl-5,6-dihydrothymine, genetic evidence indicates that an additional DNA photoproduct(s) may be formed in spores exposed to solar UV-B and UV-A radiation (Y. Xue and W. L. Nicholson, Appl. Environ. Microbiol. 62:2221-2227, 1996). We examined the occurrence of double-strand breaks, single-strand breaks, cyclobutane pyrimidine dimers, and apurinic-apyrimidinic sites in spore DNA under several UV irradiation conditions by using enzymatic probes and neutral or alkaline agarose gel electrophoresis. DNA from spores irradiated with artificial 254-nm UV-C radiation accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, while DNA from spores exposed to artificial UV-B radiation (wavelengths, 290 to 310 nm) accumulated only cyclobutane pyrimidine dimers. DNA from spores exposed to full-spectrum sunlight (UV-B and UV-A radiation) accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, whereas DNA from spores exposed to sunlight from which the UV-B component had been removed with a filter ("UV-A sunlight") accumulated only single-strand breaks and double-strand breaks. Apurinic-apyrimidinic sites were not detected in spore DNA under any of the irradiation conditions used. Our data indicate that there is a complex spectrum of UV photoproducts in DNA of bacterial spores exposed to solar UV irradiation in the environment.     

Exposure of eggs to solar UV‐B leads to reduced hatching rates in two sparid fishes,red sea bream Pagrus major and black sea bream Acanthopagrus schlegeli

Hatching success was examined under exposure to solar ultraviolet radiation (UVR) using filters to give three different light conditions [C1: UV‐B, UV‐A and photosynthetically active radiation (PAR), C2: UV‐A and PAR, C3: PAR] in red Pagrus major and black Acanthopagrus schlegeli sea bream. Hatching rate of both species was reduced by an exposure over a 2 day period to UVR and was not significantly different between two species under the three light conditions.     

Reconstruction of daily solar UV irradiation from 1893 to 2002 in Potsdam,Germany

Long-term records of solar UV radiation reaching the Earth’s surface are scarce. Radiative transfer calculations and statistical models are two options used to reconstruct decadal changes in solar UV radiation from long-term records of measured atmospheric parameters that contain information on the effect of clouds, atmospheric aerosols and ground albedo on UV radiation. Based on earlier studies, where the long-term variation of daily solar UV irradiation was derived from measured global and diffuse irradiation as well as atmospheric ozone by a non-linear regression method [Feister et al. (2002) Photochem Photobiol 76:281–293], we present another approach for the reconstruction of time series of solar UV radiation. An artificial neural network (ANN) was trained with measurements of solar UV irradiation taken at the Meteorological Observatory in Potsdam, Germany, as well as measured parameters with long-term records such as global and diffuse radiation, sunshine duration, horizontal visibility and column ozone. This study is focussed on the reconstruction of daily broad-band UV-B (280–315 nm), UV-A (315–400 nm) and erythemal UV irradiation (ER). Due to the rapid changes in cloudiness at mid-latitude sites, solar UV irradiance exhibits appreciable short-term variability. One of the main advantages of the statistical method is that it uses doses of highly variable input parameters calculated from individual spot measurements taken at short time intervals, which thus do represent the short-term variability of solar irradiance.     

Natural microbial UV radiation filters--mycosporine-like amino acids

Ozone depletion by anthropogenic gases has increased the atmospheric transmission of solar ultraviolet-B radiation (UV-B, 280-315 nm). There is a logical link between the natural defenses of terrestrial and marine organisms against UV radiation and the prevention of UV-induced damage to human skin. UV light degrades organic molecules such as proteins and nucleic acids, giving rise to structural changes that directly affect their biological function. These compounds offer the potential for development of novel UV blockers for human use. The biological role of mycosporine-like amino acids (MAAs) and scytonemin as a defense against solar radiation in organisms, together with their structure, synthesis, distribution, regulation and effectiveness, are reviewed in this article. This review points to the role of MAAs as a natural defense against UV radiation.     

UV‐A/BLUE LIGHT–INDUCED REACTIVATION OF SPORE GERMINATION IN UV‐B IRRADIATED ULVA PERTUSA (CHLOROPHYTA)1

Recent reduction in the ozone shield due to manufactured chlorofluorocarbons raised considerable interest in the ecological and physiological consequences of UV‐B radiation (λ=280–315 nm) in macroalgae. However, early life stages of macroalgae have received little attention in regard to their UV‐B sensitivity and UV‐B defensive mechanisms. Germination of UV‐B irradiated spores of the intertidal green alga Ulva pertusa Kjellman was significantly lower than in unexposed controls, and the degree of reduction correlated with the UV doses. After exposure to moderate levels of UV‐B irradiation, subsequent exposure to visible light caused differential germination in an irradiance‐ and wavelength‐dependent manner. Significantly higher germination was found at higher photon irradiances and in blue light compared with white and red light. The action spectrum for photoreactivation of germination in UV‐B irradiated U. pertusa spores shows a major peak at 435 nm with a smaller but significant peak at 385 nm. When exposed to December sunlight, the germination percentage of U. pertusa spores exposed to 1 h of solar radiation reached 100% regardless of the irradiation treatment conditions. After a 2‐h exposure to sunlight, however, there was complete inhibition of germination in PAR+UV‐A+UV‐B in contrast to 100% germination in PAR or PAR+UV‐A. In addition to mat‐forming characteristics that would act as a selective UV‐B filter for settled spores under the parental canopy, light‐driven repair of germination after UV‐B exposure could explain successful continuation of U. pertusa spore germination in intertidal settings possibly affected by intense solar UV‐B radiation.     

Artificial and Solar UV Radiation Induces Strand Breaks and Cyclobutane Pyrimidine Dimers in Bacillus subtilis Spore DNA

The loss of stratospheric ozone and the accompanying increase in solar UV flux have led to concerns regarding decreases in global microbial productivity. Central to understanding this process is determining the types and amounts of DNA damage in microbes caused by solar UV irradiation. While UV irradiation of dormant Bacillus subtilis endospores results mainly in formation of the “spore photoproduct” 5-thyminyl-5,6-dihydrothymine, genetic evidence indicates that an additional DNA photoproduct(s) may be formed in spores exposed to solar UV-B and UV-A radiation (Y. Xue and W. L. Nicholson, Appl. Environ. Microbiol. 62:2221–2227, 1996). We examined the occurrence of double-strand breaks, single-strand breaks, cyclobutane pyrimidine dimers, and apurinic-apyrimidinic sites in spore DNA under several UV irradiation conditions by using enzymatic probes and neutral or alkaline agarose gel electrophoresis. DNA from spores irradiated with artificial 254-nm UV-C radiation accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, while DNA from spores exposed to artificial UV-B radiation (wavelengths, 290 to 310 nm) accumulated only cyclobutane pyrimidine dimers. DNA from spores exposed to full-spectrum sunlight (UV-B and UV-A radiation) accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, whereas DNA from spores exposed to sunlight from which the UV-B component had been removed with a filter (“UV-A sunlight”) accumulated only single-strand breaks and double-strand breaks. Apurinic-apyrimidinic sites were not detected in spore DNA under any of the irradiation conditions used. Our data indicate that there is a complex spectrum of UV photoproducts in DNA of bacterial spores exposed to solar UV irradiation in the environment.     

Effect of solar ultraviolet radiation on growth in the marine macroalga Dictyota dichotoma (Phaeophyceae) at Helgoland and its ecological consequences

At Helgoland, in the North Sea, growth of the high sublittoral brown macroalga Dictyota dichotoma (Hudson) Lamoroux was examined in October (the time of tetraspore release) in an outdoor tank by exposing 2-day-old germlings to four solar radiation treatments achieved with different filter materials or an additional artificial light source: photosynthetically active radiation (PAR; 395–700 nm), PAR plus ultraviolet (UV)-A (320–700 nm), full solar spectrum, or solar spectrum plus artificial UV radiation (UVR). Based on length measurements over a period of 3 weeks, the growth rate in germlings strongly decreased in conditions with UVR compared to PAR: by 14% under PAR+UV-A, by 31% under the full solar spectrum and by 65% with additional UVR. Although growth rates of germlings under UVR were reduced mainly in the first week, the plants did not regain the size of the untreated plants even after 9 weeks. Regardless of the exposure, no defects in morphology or anatomy including the exposed apical meristem were detected, except for a reduction in cell division rates perhaps due to additional cost for photoprotective or repair mechanisms. Depending on the actual position of D. dichotoma plants in the natural habitat, individuals in high positions receive substantial amounts of the more harmful UV-B while those lower down might only receive UV-A during part of the day, thus the effect of UV-B on the growth of D. dichotoma will depend on its position in the field. The effects of tidal variation of the light climate and the implications of our results for the zonation of D. dichotoma are discussed. Received in revised form: 6 July 2000 Electronic Publication     

Determination of erythema-effective solar radiation in Japan and Germany with a spore monolayer film optimized for the detection of UVB and UVA – results of a field campaign

The available physical and biological broadband radiometers designed to determine erythema-effective radiation do not show any response or over/underestimate the biologically effective radiation to a high extent in the ultraviolet (UV)A spectral region. The data presented in this paper demonstrate that the biological system used in this study is the first one to make possible measurements of erythema-effective radiation in the sun in the UVA and UVB spectral region. These measurements were performed with a spore-film filter system as well as with spectroradiometers. It was demonstrated that this biotechnological method could be used to determine exact values expressed as minimal erythemal dose (MED). The spore-film system was tested in various field campaigns performed in Germany and in Japan. The seasonal daily variation of UV radiation in Germany determined in the period November 1995 to December 1996 using the spore-film filter system in sunny conditions tallied well with model calculations. The daily dose in Germany measured with the spore-film system close to the summer solstice, in sunny conditions (20.45 MED), was approximately 20 times higher than the lowest value measured close to the winter solstice (0.82 MED), a result which was in accordance with model calculations. The data determined with the spore-film filter system in Sapporo and Naha, Japan, fitted to the erythema-weighted data calculated from spectroradiometric measurements (Brewer), even at low solar radiation angles in a solar spectrum with less UVB but significant UVA. The spore-film dosimeter values were about 103 ± 8% of the integrated dose of the Brewer instrument. The standard deviation of the spore-film measurements obtained in Japan was 12.8%. The responsivity of the spore-film system towards longer wavelengths within the UVA spectrum was tested with the Okasaki Large Spectrograph with monochromatic radiation. At a wavelength of 365 nm – in a spectral region which is dominant in many tanning lamps and with minor importance for solar radiation in summer conditions – the tested spore-film system gave results that were close (112% compared to the calibration dose) to the calibration dose which was used for irradiation. Received: 27 January 1998 / Received last revision: 21 July 1998 / Accepted: 29 July 1998     

A new filter that accurately mimics the solar UV-B spectrum using standard UV lamps: the photochemical properties, stabilization and use of the urate anion liquid filter

The physiological effects unique to solar ultraviolet (UV)-B exposure (280-315 nm) are difficult to accurately replicate in the laboratory. This study evaluates the effectiveness of the sodium urate anion in a liquid filter that yields a spectrum nearly indistinguishable from the solar UV-B spectrum while filtering the emissions of widely used UV-B lamps. The photochemical properties and stability of this filter are examined and weighed against a typical spectrum of ground-level solar UV-B radiation. To test the effectiveness of this filter, light-saturated photosynthetic oxygen evolution rates were measured following exposure to UV-B filtered either by this urate filter or the widely used cellulose acetate (CA) filter. The ubiquitous marine Chlorophyte alga Dunaliella tertiolecta was tested under identical UV-B flux densities coupled with ecologically realistic fluxes of UV-A and visible radiation for 6 and 12 h exposures. These results indicate that the urate-filtered UV-B radiation yields minor photosynthetic inhibition when compared with exposures lacking in UV-B. This is in agreement with published experiments using solar radiation. In sharp contrast, radiation filtered by CA filters produced large inhibition of photosynthesis.     

Sources and measurement of ultraviolet radiation

Ultraviolet (UV) radiation is part of the electromagnetic spectrum. The biological effects of UV radiation vary enormously with wavelength and for this reason the UV spectrum is further subdivided into three regions: UVA, UVB, and UVC. Quantities of UV radiation are expressed using radiometric terminology. A particularly important term in clinical photobiology is the standard erythema dose (SED), which is a measure of the erythemal effectiveness of a UV exposure. UV radiation is produced either by heating a body to an incandescent temperature, as is the case with solar UV, or by passing an electric current through a gas, usually vaporized mercury. The latter process is the mechanism whereby UV radiation is produced artificially. Both the quality (spectrum) and quantity (intensity) of terrestrial UV radiation vary with factors including the elevation of the sun above the horizon and absorption and scattering by molecules in the atmosphere, notably ozone, and by clouds. For many experimental studies in photobiology it is simply not practicable to use natural sunlight and so artificial sources of UV radiation designed to simulate the UV component of sunlight are employed; these are based on either optically filtered xenon arc lamps or fluorescent lamps. The complete way to characterize an UV source is by spectroradiometry, although for most practical purposes a detector optically filtered to respond to a limited portion of the UV spectrum normally suffices.     

Photoinhibition by visible and ultraviolet radiation in the red macroalga Porphyra umbilicalis grown in the laboratory

Photosynthetic oxygen production and PAM fluorescence measurements were used to follow photoinhibition in the red macroalga Porphyra umbilicalis. Exposure to simulated solar radiation caused inhibition of the effective photosynthetic quantum yield from which the thalli partially recovered in the shade in subsequent hours. There were no significant differences between samples exposed to unfiltered radiation and those exposed to radiation from which increasing portions of UV radiation had been removed indicating that the thalli are well adapted to current levels of solar PAR and UV radiation. This notion was supported by the finding of high concentrations of UV screening pigments which were even enhanced by exposure to increased UV radiation. However, when exposed to (only) UV radiation about 50% higher than that encountered by the organisms in their natural habitat, the photosynthetic yield decreased slowly and did not show any recovery even when the degree of inhibition did not exceed 10%.     

Water transparency affects the survival of the medusa stage of the invasive freshwater jellyfish <Emphasis Type="Italic">Craspedacusta sowerbii</Emphasis>

Craspedacusta sowerbii is a global invader of inland waters, but little is known on what environmental factors control its colonization success. We hypothesized that water transparency and thus, exposure to UV radiation are relevant for the colonization success of this relatively transparent invasive hydroid. Here we used field and laboratory experiments to assess the effect of natural solar radiation and artificial UV radiation on the medusa stage of C. sowerbii across natural and simulated water transparency gradients in three Chilean Patagonian lakes. Short-term exposure of the jellyfish to artificial UV radiation under low Dissolved Organic Carbon (DOC) treatments induced mortality and caused sublethal effects such as swimming anomalies and production of reactive oxygen species. Outdoor exposure of jellyfish to full solar radiation in the most transparent water (Lake Ranco; DOC = 0.6 mg l^?1) resulted in almost complete mortality. However, higher DOC contents provided partial or almost complete protection against the adverse impact of UV radiation. Overall, our findings provide evidence of the role of underwater light conditions in the underlying mechanisms that may favor the invasion of this gelatinous alien species in inland waters. The results imply that under the current “brownification” of lakes, an increase in water color might provide more favorable conditions for the invasion process of this hydroid.     

Screening of visible and UV radiation as a photoprotective mechanism in plants

Prolonged exposure of plants to high fluxes of solar radiation as well as to other environmental stressors disturbs the balance between absorbed light energy and capacity of its photochemical utilization resulting in photoinhibition of and eventually in damage to plants. Under such circumstances, the limiting of the light absorption by the photosynthetic apparatus efficiently augments the general photoprotective mechanisms of the plant cell, such as reparation of macromolecules, elimination of reactive oxygen species, and thermal dissipation of the excessive light energy absorbed. Under stressful conditions, plants accumulate, in different cell compartments and tissue structures, pigments capable of attenuation of the radiation in the UV and visible parts of the spectrum. To the date, four principle key groups of photoprotective pigments are known: mycosporine-like amino acids, phenolic compounds (including phenolic acids, flavonols, and anthocyanins), alkaloids (betalains), and carotenoids. The accumulation of UV-absorbing compounds (mycosporine-like amino acids and phenolics in lower and higher plants, respectively) is a ubiquitous mechanism of adaptation to and protection from the damage by high fluxes of solar radiation developed by photoautotrophic organisms at the early stages of their evolution. Extrathylakoid carotenoids, betalains, and anthocyanins play an important role in long-term adaptation to the illumination conditions and in protection of plants against photodamage. A prominent feature of certain plant taxa lacking some classes of photoprotective pigments (such as anthocyanins) is their substitution by other compounds (e.g. keto-carotenoids or betalains) disparate in terms of chemical structure and subcellular localization but possessing close spectral properties.     

Photosynthesis of Major C3 Plants on Qinghai Plateau

The biological yield is bound up with photosynthesis. Though the air temperature on Qinghai plateau is very low, yet the intense solar radiation on the plateau and of the long sunshine hours are favourable to photosynthesis. While the air temperature is very high, it may cause the photosynthesis to midday depression in the areas of low elevation. However, this does not occur on alpine meadow in Qinghai plateau. Diurnal variation of net photosynthetic rate(Pn) of plant leaves in alpine meadow under natural environmental conditions depends on the change of air temperature and solar radiation intensity. It gives a typical curve with one peak. None or little midday depression of net photosynthetic rate was observed. The apparent quantum requirement(AQR) of plant leaves in alpine meadow under natural environmental conditions remains constant in the morning and afternoon on fine days, which indicated that no significant photoinhibition occurred. However, diurnal variation of net photosynthetic rate of plateau plant still revealed as of double peak when soil is seriously lack of water and air temperature is 30℃ or over. Under general conditions, the light compensation point and dark respiration rate in plant of alpine meadow are lower. The light saturation point and the apparent quantum requirement are higher; Therefore the apparent quantum efficiency is lower. This is related to low atmospheric pressure in the areas of high elevation on Qinghai plateau.     

Modeling study on photosynthetic-light response curves of a C4 plant,maize

Aims A light response curve can reflect a plant’s ability to utilize light, which is also a key tool in determining the relationship between photosynthetic capacity and environmental factors; however the model accuracies concerning the light response curve remain elusive. The objectives of this study were to compare and assess the model accuracies related to a light response curve and the effects of drought. Methods A field rain shelter was used to control the soil water conditions. To obtain photosynthesis parameters from the light response curve and the drought effects, the relevant models (including the rectangular model, non-rectangular hyperbolic model, modified rectangular hyperbolic model, exponential model, quadratic function model, and a newly modified model) were applied to fit the light response curves. The validity of each model was tested by analyzing the differences between the fitted values obtained by the models and the measured values. Important findings The newly modified model has been proved to performing relatively better in accurately describing the light response curve patterns, and credibly obtaining the crucial photosynthetic parameters such as the maximum net photosynthetic rate, light saturation point, light compensation point, and dark respiration rate, especially under high radiation conditions.     

UVB radiation may ameliorate photoinhibition in specific shallow-water tropical marine macrophytes

Anthropogenic stratospheric ozone depletion causes an increase in UVB radiation impinging on the earth's surface, which is a threat to plants not adapted to higher UVB irradiances. Investigations were carried out among tropical marine macrophytes, Turbinaria turbinata, Sargassum polyceratium var. ovatum, Padina sanctae-crucis, Lobophora variegate, Dictyota spec., Halimeda discoidea, Udotea flabellum, Thalassia testudinum and Syringodium filiforme collected from 0.3 to 26 m depths at the Belizean barrier reef, where ultraviolet radiation (UV)-irradiances are naturally high. Photoinhibition was induced under full solar, UV (UVA + UVB), and UVA only-depleted radiation conditions. Photosynthetic activity during high radiation stress and during recovery in reduced solar radiation was determined in vivo by measuring fluorescence changes using a PAM fluorometer device. Generally, UV caused an additional decrease of photosynthetic performance during high light stress which varies according to species, depth of growth and UV penetration at the site of collection; an observation in concordance with the conventional harmful UV-radiation effects on phototrophs. When solar radiation was reduced by 50%, significant photosynthetic recovery was observed. However, some shallow water species which are adapted to high UV were observed to recover less under treatment with depleted solar UVB radiation. Our result supports earlier reports that UVB causes not only negative effects on photosynthesis, but may also facilitate or induce recovery processes in aquatic macrophytes acclimated to high solar radiation which grow at the upper shoreline. Among the eulittoral macroalgae, e.g. Dictyota spec., P. sanctae-crucis, and H. discoidea and the seagrass T. testudinum, initiation of photosynthetic recovery processes in the presence of low irradiance of short UV-wavelengths may present an ecophysiological advantage compared to macrophytes which initiate photosynthetic recovery process during low light or in the absence of UV.     

羊栖菜幼孢子体对不同N水平生长条件和阳光紫外辐射的响应

探讨了太阳紫外辐射对两种N水平生长条件下羊栖菜幼孢子体光化学特性的影响及其恢复。结果显示,在高的光辐射下羊栖菜藻体的有效光化学效率和相对电子传递速率急剧下降,在全波长太阳辐射条件下它们的下降幅度要比仅在可见光处理下的藻体更大,2种N水平条件下藻体的光化学活性下降趋势相似,但是N加富的生长条件使得藻体具有更高抵御紫外辐射的能力,这可能是与N加富生长条件下的藻体中含有较高含量的紫外吸收物质和类胡萝卜素有关。结果表明羊栖菜的幼孢子体具有比成体更强抵御紫外线的能力,这主要体现在藻体受到紫外辐射损伤后的修复上。