Effects of UV-B radiation on the growth interaction of Ulva pertusa and Alexandrium tamarense

Enhanced UV-B(280-320 nm) radiation resulting from ozone depletion is one of global environmental problems. Not only marine organisms but also marine ecosystems can be affected by enhanced UV-B radiation. The effects of UV-B radiation on interaction of macro-algae and micro-algae were investigated using Ulva pertusa Kjellman and Alexandrium tamarense as the materials in this study. The results demonstrated that UV-B radiation could inhibit the growth of Ulva pertusa and Alexandrium tamarense when they were both mono-cultured, and the growth inhibition of algae was more significant with increasing doses of UV-B radiation. Alexandrium tamarense could inhibit the growth of Ulva pertusa in mixed culture, and the growth inhibition was more significant when increasing the initial cell density. However, Ulva pertusa could inhibit the growth of Alexandrium tamarense in early phase and stimulate the growth in latter phase when they were grown in mixed culture. Lower initial cell density(10~2 cell/ml) of Alexandrium tamarense could inhibit the growth of Ulva pertusa under UV-B radiation treatment,however, with the initial cell density increasing(10~3 and 10~4 cell/ml), the growth of Ulva pertusa was stimulated under lower dose of UV-B radiation and inhibited under higher dose of UV-B radiation by Alexandrium tamarense. Compared with that in mixed culture, Ulva pertusa showed more positive inhibition to the growth of Alexandrium tamarense under UV-B radiation treatment.

Effects of lanthanum(Ⅲ) on nitrogen metabolism of soybean seedlings under elevated UV-B radiation

The hydroponic culture experiments of soybean bean seedlings were conducted to investigate the effect of lanthanum （La） on nitrogen metabolism under two different levels of elevated UV-B radiation （UV-B, 280-320 nm）. The whole process of nitrogen metabolism involves uptake and transport of nitrate, nitrate assimilation, ammonium assimilation, amino acid biosynthesis, and protein synthesis. Compared with the control, UV-B radiation with the intensity of low level 0.15 W/m^2 and high level 0.45 W/m^2 significantly affected the whole nitrogen metabolism in soybean seedlings （p 〈 0.05）. It restricted uptake and transport of NO3^-, inhibited activity of some key nitrogen-metabolism-related enzymes, such as： nitrate reductase （NR） to the nitrate reduction, glutamine systhetase （GS） and glutamine synthase （GOGAT） to the ammonia assimilation, while it increased the content of free amino acids and decreased that of soluble protein as well. The damage effect of high level of UV-B radiation on nitrogen metabolism was greater than that of low level. And UV-B radiation promoted the activity of the anti-adversity enzyme glutamate dehydrogenase （GDH）, which reduced the toxicity of excess ammonia in plant. After pretreatment with the optimum concentration of La （20 mg/L）, La could increase the activity of NR, GS, GOGAT, and GDH, and ammonia assimilation, but decrease nitrate and ammonia accumulation. In conclusion, La could relieve the damage effect of UV-B radiation on plant by regulating nitrogen metabolism process, and its alleviating effect under low level was better than that under the high one.

The effect of UV-B radiation enhancement on the interspecific competition between Skeletonema costatum and Heterosigma akashiwo

The responses of the interspecific competition between Skeletonema costatum and Heterosigma akashiwo to UV-B radiation enhancement were studied by the co-culture method. The results showed that Heterosigma akashiwo exhibited inhibition on the growth of Skeletonema costatum, and with the increase of initial inoculation density of Heterosigma akashiwo, heavier inhibition on Skeletonema costatum appeared. Under different inoculation proportions, Heterosigma akashiwo could always be in predominance in competition with Skeletonema costatum. The UV-B radiation treatment could change the competition relationship between Skeletonema costatum and Heterosigma akashiwo, which could increase the competitive dominance of Skeletonema costatum and decrease the competitive dominance of Heterosigma akashiwo. When the inoculation proportions of Heterosigma akashiwo and Skeletonema costatum were H∶S=1∶4 and H∶S=1∶1,Skeletonema costatum was in predominance in this competition; however, Heterosigma akashiwo was in predominance when the inoculation proportion was H∶S=4∶1.

Effect of UV-B Radiation on Ingesting and Nutritional Selecting Behavior of Rotifer Brachionus urceus

Effect of UV-B radiation on ingesting and nutritional selecting behavior of the roifer Brachionus urceus on 5 species of microlgae were studied under controlled laboratory conditions. Restdts showed that enhanced UV-B radiation significantly inhibited ingesting of the rotifer B. urceus when it was fed with 5 species of micro-algae （p〈0.05）. The ingesting selectivity rate varied with the UV-B radiation enhancement when it was fed with 5 species micro-algal mixture. Results indicated that the enhanced UV-B radiation could affect ingesting and nutritional selectivity of B. urceus.

Effects of UV-B radiation and different light repair conditions on the early development of the tetraspores of Chondrus ocellatus Holm

The effects of exposure to UV-B radiation, 280-315 nm, and dark or dark repair conditions on the early development of Chondrus ocellatus Holm collected from Qingdao coast were studied under the laboratory condition. After being exposed to different doses [0, 36, 72, 108, 144 and 180 J/（m2.d）] of UV-B radiation, one treatment of tetraspores were put back to normal culture condition （PAR）, the other treatment were put into dark condition to repair for 2 h. During the cultivation, the diameter of the tetraspores were recorded every 4 d till the 50th day when vertical branches formed in all treatments. Then at the 50th day, CPDs, phycoerythrin, chlorophyll a and MAAs （Palythine and asterina-330） were measured. The results showed that low doses UV-B radiation could significantly accelerate the growth rate of the rate reduced gradually with UV-B radiation keep on tetraspores of C. ocellatus and the growth increasing. The variation trend of both the phycoerythrin and chlorophyll a concentration reduced significantly （P 〈0.05） once given the UV- B radiation. Under UV-B stress, the CPDs were induced, and the concentrations of CPDs were significant low in dark repair groups. The data of MAAs analyzed by LC/MS in the tetraspores of C. ocellatus suggested that there were two MAAs formed （palythine and asterina-330） after UV-B radiation induced, and low dose of UV-B irradiation could significantly induced the concentration of MAAs. From the growth and development state of the tetraspores, negative effects of UV-B radiation on the dark repair groups were more serious than PAR.

Changes of proteins in the Antarctic ice microalga Chlamydomonas sp. cultured under UV-B radiation stress

Antarctic ice microalga Chlamydomonas sp. can thrive undisturbed under high UV radiation in the Antarctic ice layer. However, it is unknown that the initial adaptation mechanisms in protein level occurring in response to high UV radiation. Global-expression profiling of proteins in response to stress was analyzed by two-dimensional electrophoresis （2-DE） and image analysis. In the 2-DE analysis, protein preparation is the key step. Three different protein extract methods were compared, and the results showed that the trichloroacetic acid （TCA）-acetone fractional precipitation method was the fittest one. At the same time, the proteins in Chlamydomonas sp. were compared in 2-DE way, and the synthesis of seven protein spots was found disappeared and 18 decreased after exposed to UV-B radiation. In addition, 14 protein spots were enhanced or induced, among which two new peptides （20 and 21 kDa） appeared whose isoelectric point （pI） was 7.05 and 4.60 respectively. These changed proteins might act as key role in the acclimation of Antarctic ice microalga to UV-B radiation

The effects of enriched C0_(2) and enhanced UV-B radiation on ultrastructure of Dunaliella salina, singly and in combination

The effects of ambient CO2/ambient UV-B, enriched CO2/ambient UV-B, ambient CO2/enhanced UV-B, and enriched CO2/enhanced UV-B on the ultrastructure of Dunaliella salina were investigated. （1） The ultrastructure of D..salina cell in the control experiment showed that the arrangement of thylakoid lamellae was regular, and there were many large starch grains among the thylakoid lamellae. A prominent well-developed pyrenoid was found in the middle of the chloroplast. Nucleus envelope and nucleolus were clearly observed. The Golgi apparatus accompanied by numerous vesicles with a compact arrangement of cisternae and the peripheral tips of the cisternae were swollen to a size comparable to that of some of the associated vesicles. （2） The ultrastructure of D. salina cell in enriched CO2 showed that the arrangement of thylakoid was regular and the lamellae were vivid. Developed pyrenoids were found in the low-CO2-grown cells, but not in the high-CO2-grown cells. The mitochondria cristae were vivid. The arrangement of Golgi apparatus was compact. （3） The ultrastructure of D. salina cell in enhanced UV-B showed that the thylakoid was dissolved and the cells had a less developed pyrenoid or no detectable pyrenoid. Part of the nucleus envelope was dissolved. The number ofmitochondria was increased and some mitochondria cristae were disintegrated. The starch grains were broken apart into many small starch grains. The Golgi apparatus with a loose arrangement ofcistemae and the peripheral tips of the Golgi cistemae were not especially swollen, with several large associated vesicles. （4） The ultrastructure of D. salina cell in the enriched CO2/enhanced UV-B showed that part of the thylakoid and nucleus envelopes of some cells were dissolved. The pyrenoid was larger than that of the enhanced UV-B. There were many mitochondria between stroma and chloroplast membrane, but mitochondria cristae were partly dissolved. Many small starch grains were accumulated in cells. The starch sheath was broken into several discontinuous starch grains with different sizes. The arrangement of Golgi apparatus was loose. Above all, although the enriched CO2 can alleviate the damage induced by the UV-B radiation, the effects of experimental UV-B radiation were larger than the effects of actual UV-B radiation, the damage induced by the UV-B radiation was so severe, therefore, CO2 enrichment could not restore the ultrastructure to the control level.

Effects of UV-B radiation intensity and timing on epidemiological components of wheat stripe rust

Stripe rust caused by Puccinia striiformis f. sp. tritici is an important wheat disease worldwide that is greatly influenced by environmental conditions. Ultraviolet B(UV-B) radiation is one important environmental factor affecting the occurrence and epidemiology of wheat stripe rust. Investigating UV-B radiation effects on the epidemiology of stripe rust may be conducive to monitoring and predicting this disease. In this study, wheat seedlings were exposed to UV-B radiation during different periods under laboratory conditions and radiation effects on epidemiological components of wheat stripe rust were investigated. Results showed that incubation period was shortened, and the infection efficiency, sporulation quantity and disease index increased when UV-B radiation was performed only pre-inoculation. When the UV-B radiation was performed only postinoculation or both pre-and post-inoculation, the incubation period was prolonged, and the infection efficiency, sporulation quantity and disease index were reduced. When healthy wheat seedlings were inoculated using urediospores collected from wheat leaves irradiated by UV-B only post-inoculation or both pre-and post-inoculation, infection efficiency, sporulation quantity and disease index were also reduced. However, in the latter, the disease incubation period did not differ under varying UV-B radiation intensities compared to that when wheat leaves were not treated with UV-B radiation. Overall, the effects of direct exposure of wheat plants to UV-B radiation with different intensities in different periods on epidemiological components of wheat stripe rust were systematically explored, and the results suggest that the effects of UV-B radiation increased gradually with the increase of UV-B radiation intensity. This information provides a basis for monitoring and predicting this disease as well as for conducting further studies on pathogen virulence variation.

Effect of atmospheric aerosols on UV-B radiation reaching the ground

Solar ultraviolet radiation reaching the ground can be reduced due to light scattering of atmospheric aerosols. Aerosol pollution has led to the decrease in biological active UV-B radiation by about 45% and 10% in city and rural areas, respectively. In populated areas, effect of aerosol scattering on UV-B radiation may offset the increased amount of UV-B caused by ozone depletion, but in clean areas such as two poles, ozone depletion may have great damage effects on ecosystems.

Effects of UV-B Radiation and Water Stress on Soybean Yield

Soybean Dongnong 47 was subjected to the experiments of increasing UV-B radiation and water stress on soybean yield components in different growth periods. The results showed that 100-seed weight greatly increased during the early stage of pod filling in the treatment of weak UV-B radiation, seed number per plant as well as seed weight per plant and Dongnong47 yield also increased, while the yield and yield components of Dongnong47 during the blossom to mature period were negatively affected in the treatment of intensive UV-B radiation. 100-seed weight of Dongnong47 all increased in the double factor treatments of UV-B radiation and water stress, with the drought intensified, seed number per plant, seed weight per plant and yield of Dongnong47 decreased, the change of 100-seed weight were various and the antagonistic action of UV-B radiation and water stress were related with their intensity.

Effect of UV-B radiation on the population dynamics of the rotifer Brachionus urceus

The effect of UV-B radiation enhancement at experimental doses of 0.00,0.24,0.48,0.72,0.96,and 1.20 kJ/m 2 on the population dynamics of the rotifer Brachionus urceus feeding on the alga Chlorella sp.was studied under controlled laboratory conditions using clonal culture and life-table techniques.The results show that UV-B radiation treatment significantly shortened the survival time of the rotifer （P 0.05）： The longest survival time （336 h） occurred in the control （0.00 kJ/m 2 ） while the shortest （222 h） occurred when exposed to the highest UV-B radiation treatment （1.20 kJ/m 2 ）.The fecundity of the rotifer B.urceus was enhanced by the lower UV-B radiation treatment （0.24 and 0.48 kJ/m 2 ） but inhibited by the higher treatments （0.96 and 1.20 kJ/m 2 ）.Life expectancy also was obviously affected by UV-B radiation （P 0.05）.The highest life expectancy occurred in the control （0.00 kJ/m 2 ）,and it became shorter with increasing doses of UV-B radiation.The resutls in the present study indicate that the life expectancy of the rotifer B.urceus can be used as an indicator for UV-B radiation enhancement.

Effect of UV-B radiation on the feeding behavior of the rotifer Brachionus plicatilis

Effect of UV - B radiation on the feeding behaviour of marine zooplankton is important to assessing the health harm of marine ecosystem due to the gradually enhanced UV - B radiation in air. However, there are a few studies on this topic. The feeding behavior of the rotifer, Brachionus plicatilis, under the treatment of UV - B radiation on five species of microalgae, i. e. , Chlorella sp. , Tetraselmis chuii, Isochrysis galbana Park 8701, Chaetoceros muelleri Lermumerman, and Nitzschia clostertum, was studied. The results showed that the filtering and feeding rates of the rotifer decreased significantly with the dose increase of UV - B radiation when fed with five species of microalgae respectively （ P 〈 0.05 ） which indicates UV - B radiation inhibits the feeding activities of the rotifer on microalage. The mixed culture experiments shows the rotifer preferred to feed Chlorella sp. , then C. muelleri, L galbana, N. clostertum and T. chuii in turn if without UV - B radiation. Under the highest dose of UV - B radiation treatment （2.70 kJ/m^2）, the rotifer preferred to feed C. muelleri, then Chlorella sp. , N. clostertum, L galbana and T. chuii in turn. Chlorella sp. , L galbana and C. muelleri became the more favorite foods of the rotifer while T. chuii and N. clostertum became less favorite foods. The change of feeding rate and feeding selectivity of zooplankton driven by the enhanced UV - B radiation will lead to the change in the structure of phytoplankton community.

Effects of UV-B radiation on tetraspores of Chondrus ocellatus Holm(Rhodophyta),and effects of red and blue light on repair of UV-B-induced damage

We evaluated the effects of red and blue light on the repair of UV-B radiation-induced damage in tetraspores of Chondrus ocellatus Holm. Tetraspores of C. ocellatus were treated with different UV-B radiation levels(0,36,72,108,144 and 180 J/m2),and thereafter subjected to PAR,darkness,or red or blue light during a 2-h repair stage,each day for 48 days. The diameters and cellular contents of cyclobutane pyrimidine dimmers(CPDs),chlorophyll a(Chl a),phycoerythrin,and UV-B-absorbing mycosporinelike amino acids(MAAs) contents of the tetraspores were determined. Our results show that low doses of UV-B radiation(36 and 72 J/m 2) promoted the growth of C. ocellatus; however,increased UV-B radiation gradually reduced the C. ocellatus growth(greater than 72 J/m2). The MAAs(palythine and asterina-330) in C. ocellatus were detected and analyzed by LC/MS. Our results suggest that moderate red light could induce the growth of this alga in aquaculture. In addition,photorepair was inhibited by red light,so there may be some other DNA repair mechanism activated by red light. Blue light promoted the activity of DNA photolyase,greatly improving remediation efficiency. Red and blue lights were found to reduce the capacity of C. ocellatus to form MAAs. Therefore,PAR,red light,and blue light play different roles during the repair processes for damage induced by UV-B radiation.

Physiological responses of macroalga Gracilaria lemaneiformis(Rhodophyta) to UV-B radiation exposure

This paper aims to evaluate the effects of ultraviolet-Bradiation(UVBR) on Gracilaria lemaneiformis,a commercial red macroalga and an important source of agar. To study the in-vitro effect of UVBR on G. lemaneiformis,this plant was cultivated and exposed to photosynthetically active radiation(PAR) at 40 μmol photons/(m2 ·s) and enhanced UVBR(0,0.36,0.72,1.08,1.44,and 1.80 k J/(m 2 ·d)) for 13 days. The samples were processed for histochemical analysis,and the growth rate,photosynthetic pigment contents,photosynthetic performance,reactive oxygen species levels,membrane permeability,malonyl dialdehyde contents and antioxidant capacity of G. lemaneiformis were investigated. After 13 days of exposure to PAR+UVBR,G. lemaneiformis showed photodamage and photoinhibition of photosynthetic pigments(chlorophylla and phycoerythrin),leading to a decreased photosynthetic efficiency. Further,there was a corresponding decrease in the relative growth rates and depigmentation and partial necrosis of the apical segments were noted after exposure to PAR+UVBR. Additionally,UVBR induced excess production of superoxide radicals and hydrogen peroxide,eliciting a marked cellular membrane damage and antioxidative response.

Protecting effect of He-Ne laser on winter wheat from UV-B radiation damage by analyzing proteomic changes in leaves

The ultraviolet-B (UV-B) radiation can affect gene expression of plant in growth and development. Winter wheat (Triticum aestivum), as a kind of economic crop cultured in the Northern China, is also damaged by present-day ultraviolet-B (UV-B) radiation. It was reported that He-Ne lasers could alleviate cell damage caused by UV-B radiation in plants. To get the proteomic changes of wheat alleviated by He-Ne lasers, we studied protein expression profiles of winter wheat (Jin Mai NO.79) leaves by running 2-DE (two-dimensional gel electrophoresis), which allowed the identification of some significantly different gel spots. The spots were further verified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry, in which they were confirmed to be winter wheat proteins. The results showed: 1) the proteomic changes between the ultraviolet-B radiation group and normal light group were significantly different on sixth day;2) The expression of some proteins such as catalase, DNA polymerase and reduced glutathione declines at the ultraviolet-B radiation group and increases at the UV-B + He-Ne laser group. This indicates UV-B could regulate genes encoding proteins in Winter wheat leaves and affect the growth of the Winter wheat. He-Ne lasers treatment could significantly alleviate UV-B-induced damage in wheat.

Effects of Elevated Solar UV-B Radiation from Ozone Depletion on Terrestrial Ecosystems

In the last three decades much researchhas been carried out to investigate the biologicaleffects of a thinning stratospheric ozone layeraccompanied by an enhanced level of solarultraviolet-B radiation at the Earth’s surface.Enhanced UV-B radiation affects ecosystems in manyways directly and indirectly. The responses can bebiochemical, physiological, morphological oranatomical, and the direction of the response can varybetween different species, communities andecosystems. In this paper we firstly introduce generalconcepts, and methods for measuring the ecologicaleffects of UV-B radiation. Secondly, we provide anoverview interpretation of the effects of enhancedUV-B on terrestrial ecosystems from recent studies.These studies include effects of UV-B on growth andreproduction, composition of communities,competitive balance, decomposition of litter, andinteractions with other factors etc. Finally, werecommend future research directions to identify theeffects of elevated UV-B radiation on ecosystems inChina.

Saponin synthesis and cotton growth is antagonistically regulated by solar UV-B radiation

Background: Earlier we have reported that the exclusion of solar UV-B increased the growth and yield of cotton plants as compared with ambient UV-B. The UV-B radiation effects on the saponins and the impact of ambient and reduced UV-B on the accumulation of saponins has not been investigated yet. Thus a field experiment was conducted to study the influence of solar UV-B on the growth response and saponin synthesis in cotton(Gossypium hirsutum) var. Vikram plants by the exclusion of UV-B. The cotton plants were grown in specially designed iron chambers, wrapped with filters that excluded UV-B(<315 nm), or transmitted ambient UV-B.Results: Exclusion of ambient UV-B enhanced the growth of cotton plants in terms of plant height and leaf area.Greater plant height in UV-B excluded plants was due to elongated internode and more number of nodes.Enhancement in growth was accompanied by a decrease in the accumulation of saponins, which was quantified by the spectrophotometric, TLC and HPLC methods. Solvent extraction of saponins from the internodes and leaves were used for the bioassay of Amaranthus hypocotyl growth and expansion of cucumber cotyledons. Extracts obtained from the UV-B excluded plants(leaves and internodes) promoted the growth to a larger extent as compared with the extracts obtained from ambient grown plants.Conclusions: The result indicates that solar UV-B may possibly suppress the plant growth by regulating the synthesis of natural growth inhibitor's like saponin.

Different Doses of the Enhanced UV-B Radiation Effects on Wheat Somatic Cell Division

Being sessile, plants are continuously exposed to DNA-damaging agents presenting in the environment such as ultraviolet (UV). Sunlight acts as an energy source for photosynthetic plants;hence, avoidance of UV radiations (namely, UV-A, 315 - 400 nm;UV-B, 280 - 315 nm;and UV-C, 1 group: 4.05 kJ&#8226m-2&#8226d-1, B2 group: 10.08 kJ&#8226m-2&#8226d-1, B3 group: 7.05 kJ&#8226m-2&#8226d-1, B4 group: 23.02 kJ&#8226m-2&#8226d-1) treatment wheat, then, explored on the growth of wheat root and wheat root tip cell of chromosome aberration effect. In wheat, root-tip cells were observed with confocal laser scanning microscopy (CLSM), the results showed that low doses of B1 group (4.05 kJ&#8226m-2&#8226d-1) promoted the growth of wheat root and cell mitosis frequency. But high dose of B2 group (10.08 kJ&#8226m-2&#8226d-1), B3 group (17.05 kJ&#8226m-2&#8226d-1), B4 group (23.02 kJ&#8226m-2&#8226d-1) inhibited the growth of wheat root tip, and made crooked growth of wheat root, and inhibited the wheat root tip cell mitotic frequency and processed that induce root tip cells of wheat produce all kinds of aberration of chromosome in the interphase containing “multiple nucleoli nuclei”, “incomplete nuclei”, “long round nuclei”, “bean sprouts nucleus”. In mitosis M period contains “dissociative chromosome”, “chromosome bridge”, “adhesion chromosome”, “multi-bundle divide”, “nuclear anomalies”. After, high doses of enhanced UV-B radiation treatment, most of the cell cycle anomaly concentrated in mitosis interphase. In mitosis M period, with UV-B radiation dose enhanced chromosome aberration rate was on the rise and the aberration types also increasing.

Comparative Analysis of Photosynthetic Activity and PSII Protein Profiles of Some Plants Grown under Enhanced Solar UV-B Radiation

The deleterious effects of ultraviolet B(UV-B)radiation on photosynthesis and photosynthetic proteins of tropical and temperate plants have been studied.Like tropical plants(black gram and green gram),the temperate plants(carrot and radish)also successfully grown in the tropical region.They were exposed to enhanced UV-B radiation under field condition.Comparative studies show that under enhanced UV-B radiation photosynthetic activity was increased in black gram.In green gram and radish the UV-B radiation slightly enhanced the photosynthetic activity,but it inhibited the photosynthetic activity in carrot.The comparative results showed changes in contents of thylakoid 55,47,43,33,29,27-25,23 and 17 kDa polypeptides that were significantly lowered in UV-B treated carrot plant when compared to other plants.The PSII protein profile results showed a strong correlation between the presence of a membrane polypeptide and photosynthetic activity.In black gram and green gram the UV-B radiation did not produce any significant difference in the PSII polypeptides.As in the case of radish the UV-B radiation increased the accumulation of 33-28 kDa protein and affected expression of the 63 kDa protein.In the case of carrot,severe degradation of 32 kDa and 33 kDa,corresponding to D1 and D2 core proteins of PSII,was observed.It could be concluded that the ability of plants to tolerate increased levels of UV-B radiation,relative to photosynthetic capacity,depends on acclimation processes of the plant in the growing region.

Stress Responses of Peanut (<i>Arachis hypogaea</i>L.) Genotypes as Measured by Trigonelline Content after Exposure to UV-B Radiation

UV-B radiation has been widely documented as a stressor for plants that can cause decreased biomass, reduction in photosynthesis, and oxidative stress. Trigonelline is a secondary metabolite that is biosynthesized in some plants in response to abiotic stress such as UV-B irradiation. The objectives of this study were to examine biochemical stress responses for peanut plants (Arachis hypogaea L.) of four different genotypes (Spanish, Valencia, Virginia, and Runner) after exposure at various lengths to UV-B radiation and to examine the alteration of trigonelline biosynthesis due to the age of the plants. Peanut plants from the genotypes were exposed to UV-B radiation at three exposure times (60, 120, and 180 min);plants from two growth stages, the flowering (R1) and early maturity (R7), were used. Significant positive correlations (rs 0.29-0.74, P≤0.05) were found for trigonelline concentrations and UV-B exposure times. With longer exposure times of 180 min for plants at R7, trigonelline biosynthesis began as early as 10 days after treatment with 154.6 μg·g-1 DW and remained or increased by up to 71.5 μg·g-1 DW (46.3%) throughout the sampling intervals (10, 20, 30, 40, and 50 days after treatment) to a final value of 226.1 μg·g-1 DW. All four genotypes at R7 exhibited trigonelline concentrations 47.3% to 52.4% (71.6 to 96.5 μg·g-1 DW) higher than individuals at R1. Trigonelline biosynthesis at R7 was significantly (P<0.05) affected by all levels of UV-B exposure, whereas trigonelline concentrations at R1 were significantly influenced (P<0.05) by only the longer exposure times (120 and 180 min). No statistically significant difference was found in trigonelline concentration among the four different genotypes. UV-B irradiation had the greatest effect on plants at R7 after 120 and 180 min of exposure, as 15 out of 20 (75%) individuals had significantly higher (P<0.05) trigonelline concentrations.