Influence of supplemental UV-B radiation on photosynthetic characteristics of rice plants

In a field experiment with rice (Oryza sativa L. cv. Saket 4) grown under ambient and supplemental ultraviolet-B (UV-B) radiation at 20 % ozone depletion, differences in gas exchange, concentrations of photosynthetic pigments, anthocyanins and flavonoids, biomass accumulation, catalase and peroxidase activities, and contents of ascorbic acid and phenol were determined. Decline in photosynthesis was associated with reductions in stomatal conductance and concentrations of photosynthetic pigments. Enhanced UV-B radiation (eUV-B) increased the contents of flavonoid and phenolic compounds in leaves. Peroxidase activity increased and catalase activity was always lower at eUV-B. The total plant biomass decreased at eUV-B.     

Arbuscular mycorrhizal influence on growth,photosynthetic pigments,osmotic adjustment and oxidative stress in tomato plants subjected to low temperature stress

The influence of the arbuscular mycorrhizal (AM) fungus, Glomus mosseae, on characteristics of growth, photosynthetic pigments, osmotic adjustment, membrane lipid peroxidation and activity of antioxidant enzymes in leaves of tomato (Lycopersicon esculentum cv Zhongzha105) plants was studied in pot culture under low temperature stress. The tomato plants were placed in a sand and soil mixture at 25°C for 6 weeks, and then subjected to 8°C for 1 week. AM symbiosis decreased malondialdehyde (MDA) content in leaves. The contents of photosynthetic pigments, sugars and soluble protein in leaves were higher, but leaf proline content was lower in mycorrhizal than non-mycorrhizal plants. AM colonization increased the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) in leaves. The results indicate that the AM fungus is capable of alleviating the damage caused by low temperature stress on tomato plants by reducing membrane lipid peroxidation and increasing the photosynthetic pigments, accumulation of osmotic adjustment compounds, and antioxidant enzyme activity. Consequently, arbuscular mycorrhiza formation highly enhanced the cold tolerance of tomato plant, which increased host biomass and promoted plant growth.     

增强UV-B辐射和氮对谷子叶光合色素及非酶促保护物质的影响

以谷子(Setaria italica(L)Beauv.)为对象,从拔节期开始持续给予低氮(1.875 mmol/L)和高氮(15 mmol/L)两种氮供应条件并从抽穗期开始进行26 d两种强度(4.29、7.12 kJ·m-2·d-1)的增强UV-B辐射处理,研究了谷子叶中光合色素含量、类黄酮含量和苯丙氨酸解氨酶(PAL)活性的变化.结果表明:与高氮供应条件相比,低氮供应条件明显降低了谷子叶中光合色素含量但提高了类胡萝卜素/叶绿素含量比值;在开花期中段和灌浆期中段,高氮供应条件下谷子叶中光合色素含量对增强UV-B辐射比低氮供应条件下的谷子更敏感.从灌浆期开始到处理结束,两种影响因子对谷子叶中类黄酮含量均有显著影响,增强UV-B辐射导致谷子叶中类黄酮含量逐渐升高,且相同增强UV-B辐射强度下低氮供应条件下的谷子叶中类黄酮含量明显高于高氮供应条件下的谷子.谷子叶中PAL活性对两种影响因子的响应较类黄酮含量更加敏感,低氮供应条件使谷子叶中PAL活性明显提高.结合上述指标的相关性分析结果可知,低氮供应条件加强了处于繁殖期主要阶段的谷子叶中类黄酮的积累,并使谷子叶中的类胡萝卜素/叶绿素含量比值明显提高,进而有助于维持谷子叶中光合色素含量在增强UV-B辐射条件下的相对稳定性,对植株抵抗UV-B辐射伤害有利.     

臭氧浓度升高对毛竹叶片光合色素和抗性生理的影响

为了解毛竹对温室气体浓度升高的生理响应,探索竹子应对气候变化的经营策略,运用开顶式同化箱(OTCs)开展了5个O₃浓度梯度(过滤大气CF、环境大气NF、50nl·L^-1、100nl·L^-1、150nl·L^-1对毛竹(Phyllostachys edulis)叶片光合色素、可溶性蛋白、脂质过氧化和抗氧化系统的影响研究。结果表明:随O₃浓度升高,毛竹叶片Chl和Car含量呈下降趋势,可溶性蛋白、MDA和O₂^-含量呈升高趋势。与CF相比,100nl·L^-1和150nl·L^-1O₃,浓度处理毛竹叶片光合色素含量极显著降低,叶片可溶性蛋白、MDA和O₂^-含量极显著升高;随O₃浓度升高,SOD活性呈降低趋势,100nl·L^-1和150nl·L^-1O₃浓度处理较CF极显著下降。POD活性呈升高趋势,100nl·L^-1和150nl·L^-1O₃浓度处理较CF极显著提高;长时间高O₃浓度(100nl·L^-1及以上)胁迫条件下,会导致毛竹叶片光合色素降解或合成受阻,叶片老化加快,膜脂过氧化程度加剧,膜结构和抗氧化系统功能遭到破坏,影响毛竹的正常生长。     

土壤水分和氮素有效性对刺槐幼苗叶片活性氧产生和清除的影响

采用施加氮肥和人工控水的方法,以一年生刺槐幼苗为材料进行盆栽实验,探讨提高土壤氮素含量对不同土壤水分条件下刺槐幼苗叶片中活性氧产生和清除的影响。结果表明:(1)相同氮素水平下,降低土壤水分含量引起刺槐生物量和叶片光合色素含量降低,而过氧化氢(H2O2)含量升高;抗氧化酶系统中的超氧化物歧化酶(SOD)和过氧化物酶(POD)活性和过氧化氢酶(CAT)活性不同程度降低;抗氧化剂中抗坏血酸(ASA)含量和还原型谷胱甘肽(GSH)含量均有所提高;MDA含量逐渐升高,而同期细胞膜相对电导率显著升高。(2)相同水分条件下,提高土壤氮素水平显著提高了刺槐幼苗叶片光合色素含量,同时也一定程度提高了总生物量,显著降低了H2O2含量;SOD、POD和CAT活性不同程度升高;ASA含量和GSH含量则表现出不同程度下降;相对电导率显著降低同时MDA含量一定程度降低。因此,增加土壤氮素有效性可显著提高刺槐幼苗叶片光合色素含量,显著抑制活性氧的产生,一定程度提高总生物量和抗氧化酶活性,降低膜脂过氧化程度,从而有利于缓解干旱引起的伤害。     

Effect of Zeatin on H202 Scavenging System of Vitis vulpina Leaf Disks Under Salt Stress

Leaf disks of Vitis vulpina L. were incubated in hquid media containing 0,75,100, 125,150,200 and 225 mmol•L-1 NaCl with or without 1 μmol•L-1 zeatin, at 25 ℃ ,under 1 000 μmol • m-2 • s-1 continuous illumination, leaf relative permeability, contents of photosynthetic pigments and soluble protein, and activities of catalase (CAT), ascorbate peroxidase (AsA-POD) and guaiacol peroxidase(G-POD) were compared. The results showed that relative leaf permeability was increased following the increase of NaC1 concentration, whereas activities of leaf CAT, AsA-POD and G-POD, and contents of leaf photosynthetic pigments were reduced significanfiy. These effects of salt stress were significantly inhibited in the presence of zeatin. The ,relationship between relative leaf permeability and activities of H2O2 scavenging enzymes were discussed.     

玉米素对盐渍下葡萄叶圆片H2O2清除系统的影响

研究了盐渍条件下河岸葡萄(Vitis vulpina L.)叶圆片细胞膜相对透性、光合色素和可溶蛋白含量、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(AsA-POD)和愈创木酚过氧化物酶(G-POD)活性的变化以及施加玉米素对这些酶的影响。结果表明,叶细胞膜相对透性随盐浓度增加而增强;盐渍引起叶片光合色素和可溶蛋白含量减少并使CAT、AsA-POD和G-POD活性明显下降。玉米素处理明显抑制盐渍效应,可能与其对CAT、AsA-POD和G-POD的刺激作用有关。     

Alteration in growth and thylakoid membrane lipid composition of <Emphasis Type="Italic">Azolla caroliniana</Emphasis> under phosphate deficiency

The changes in the fresh biomass accumulation, photosynthetic and anthocyanin pigments, photosystem 2 (PS 2) activity, ultrastructure of chloroplast, total lipids and fatty acid composition of thylakoid membrane were followed in the aquatic fern Azolla caroliniana grown on medium either deficient or supplied with various phosphorus concentrations. The content of photosynthetic pigments and the anthocyanin/chlorophyll ratio increased significantly with increasing PO₄ ³⁻ concentration. Phosphate deficiency inhibited growth and PS 2 activity and decreased content of total lipids and phospholipids in isolated thylakoids. This was accompanied with a significant increase in the percentage of galalactolipids.     

Effects of UV-B radiation on antioxidant parameters of iron-deficient barley plants

Iron deficiency is a stress frequently experienced by plants, owing to the low solubility of Fe(III) salts in neutral or alcaline soils. Iron is an essential plant nutrient as it is involved in fundamental metabolic processes. Furthermore, it is a constituent of important antioxidant enzymes, which are involved in maintaining the balance of cell redox state. UV-B radiation is an environmental problem which can alter the redox state of plants through the increased production of reactive oxygen species. In order to investigate if iron deficiency influences the antioxidant response of plants to UV-B radiation, barley seedlings, Hordeum vulgare L. cv. Express, were exposed to UV-B radiation while growing in nutrient solutions with or without iron. After eight days of growth, plants were harvested and analysed. Results show that, during the 8 days of the experimental period, in neither of the two nutritional conditions considered does UV-B exposure reduce shoot weight or induce evident alterations of thylakoid membranes in respect to controls. However, different responses to UV-B radiation between iron-deficient and iron-sufficient plants were observed at the level of parameters related to oxidative stress. In fact, in iron-sufficient plants the contents of photosynthetic pigments and ascorbate, and the enzyme activities of ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6) were not affected by UV-B radiation. Conversely, in iron-deficient plants the contents of ascorbate and zeaxanthin and the activity of ascorbate peroxidase increased under UV-B exposure, whereas catalase activity decreased. Furthermore, UV-B radiation induced an increase of hydrogen peroxide content which was higher in iron-deprived plants than in iron-sufficient ones. This may indicate that plants growing in an environment enriched in UV-B radiation may develop a high level of oxidative stress when iron supply is limited.     

PIGMENT AND PHOTOSYNTHETIC RESPONSES OF OSCILLATORIA AGARDHII (CYANOPHYTA) TO PHOTON FLUX DENSITY AND SPECTRAL QUALITY1

The effects of photon flux density (PFD) and spectral quality on biomass, pigment content and composition, and the photosynthetic activity of Oscillatoria agardhii Gomont were investigated in steady-state populations. For alterations of PFD, chemostat populations were exposed to 50, 130 and 230 μmol photons·m^?2·s^?1 of photosynthetic active radiation (PAR). Decreases in biomass, chlorophyll a (Chl a) and c-phycocyanin (CPC) contents, and CPC: Chl a and CPC: carotenoid content was not altered. Increases in the relative abundances of myxoxanthophyll and zeaxanthin and deceases in the relative abundances of echinenone and β-carotene within the carotenoid pigments coincided with increasing PFD. Increases in Chl a-specific photosynthetic rates and maxima and decreases in biomass-specific photosynthetic rates and maxima with increasing PFD were attributed to increased light harvesting by carotenoids per unit Chl a and reduction in total pigment content, respectively. Responses to spectral quality were tested by exposing chemostat populations to a gradient of spectral transmissions at 50 μmol photons·m^?2·s^?1 PAR. Biomass differences among populations were likely attributable to the distinct absorption of the PAR spectrum by Chl a, CPC, and carotenoids. Although pigment contents were not altered by spectral quality, relative abundances of zeaxanthin and echinenone in the carotenoid pigments increased in populations exposed to high-wavelength PAR. The population adapted to green light possessed a greater photosynthetic maximum than populations adapted to other spectral qualities.     

超氧阴离子对水稻幼苗光合色素含量的影响

分别用不同浓度的铜试剂和百草枯对水稻幼苗进行叶面喷施后,于４,２４,４８,７２ｈ分别测定叶片中叶绿素和类胡萝卜素含量的动态变化．结果表明,处理后叶片中光合色素含量降低．铜试剂及百草枯对叶绿素和类胡萝卜素含量的影响有相似的规律．在处理后的４ｈ,光合色素含量开始发生变化,铜试剂处理后幼苗叶片中光合色素含量在７２ｈ最低,百草枯处理后幼苗叶片光合色素含量在４８ｈ达最低,降低的幅度与铜试剂及百草枯的浓度成正相关．     

Selenium-induced changes in activities of antioxidant enzymes and content of photosynthetic pigments in Spirulina platensis

Spirulina platensis exposed to various selenium （Se） concentrations （0, 10, 20, 40, 80, 150, 175, 200, 250 mg/L） accumulated high amounts of Se in a dose- and time-dependent manner. Under low Se concentrations （〈150 mg/L）, Se induced increases in biomass concentration, content of photosynthetic pigments, and activities of glutathione peroxidase （GPX）, superoxide dismutase （SOD）, catalase （CAT） and Gua-dep peroxidases （POD）, which indicates that antioxidant enzymes play an important role in protecting cells from Se stress. Higher Se concentrations （≥175 mg/L） led to higher Se accumulation and increases in activities of GPX, SOD, CAT and POD, but also induced lipid peroxidation （LPO） coupled with potassium leakage and decreases in biomass concentration and contents of photosynthetic pigment. The results indicate that increases in activities of the antioxidant enzymes were not sufficient to protect cell membranes against Se stress. Time-dependent variations in the activities of antioxidant enzymes, contents of chlorophyll a and carotenoid and the LPO level were also investigated under representative Se concentrations of 40 and 200mg/L. Opposite variation trends between SOD-CAT activities, and GPX-POD-APX activities were observed during the growth cycles. The results showed that the prevention of damage to cell membranes of S. platensis cells could be achieved by cooperative effects of SOD-CAT and GPX-POD-APX enzymes. This study concludes that S. platensis possessed tolerance to Se and could protect itself from phytotoxicity induced by Se by altering various metabolic processes.     

Changes in oxidative stress defense system in wheat (Triticum aestivum L.) and mung bean (Vigna radiata L.) cultivars grown with and without mineral nutrients and irradiated by supplemental ultraviolet-B

Field study was conducted to evaluate the inter- and intra-specific variations in sensitivity of two cultivars each of wheat (Triticum aestivum L. cv. HD 2329 and HUW 234) and mung bean (Vigna radiata L. cv. Malviya Jyoti and Malviya Janpriya) to supplemental levels of UV-B irradiation (sUV-B, 280–315 nm) with and without recommended levels of mineral nutrients. Results showed decrease in photosynthetic pigments and biomass of all the four cultivars due to sUV-B radiation. Antioxidative defense system was activated in all the cultivars after irradiation with sUV-B. SOD, peroxidase and total thiol contents increased, while catalase activity and ascorbic acid contents decreased under sUV-B irradiation. On the basis of biomass, UV-B sensitivity can be arranged in decreasing order as: Malviya Janpriya < Malviya Jyoti < HD 2329 < HUW 234. Application of mineral nutrients (N, P and K) showed significant positive response in all cultivars by ameliorating the negative impact of sUV-B.     

藏北那曲地区草地退化动态评价

利用1982—2000年NOAA/AVHRR 第1通道、第2通道和NDVI的旬资料反演得到的藏北那曲地区历年植被覆盖度、年最大牧草鲜质量和6—9月平均改进型土壤调节植被指数,分析了近20年来那曲地区草地荒漠化的动态变化规律.结果表明：以草地荒漠化评价“基准”和5年滑动平均的方法,得到那曲地区近20年平均草地退化面积占土地总面积的43.1%,草地退化面积总体呈减少趋势,其中前10年呈减少趋势,后10年呈增加趋势,西部地区的退化面积大于其它地区.在气温、降水、潜在蒸散、水汽压、风速、日照时数、降水蒸散比和温度降水比8个气候因子中,潜在蒸散量对草地退化面积的影响最显著.     

不同钙浓度对宽叶雀稗幼苗的生长和抗性生理的影响

研究不同钙浓度对宽叶雀稗(Paspalum wettsteinii)幼苗生长和生理的影响, 对于揭示宽叶雀稗对不同钙浓度环境的适应机理至关重要。该研究采用盆栽砂培试验, 研究不同钙浓度(0、5、25、50、100和200 mmol·L^-1 CaCl₂)和不同处理时间(7、14、21和28天)对宽叶雀稗幼苗生长、渗透调节物质含量、抗氧化酶活性、叶绿素含量和光合参数的影响。结果表明, 随着CaCl₂浓度的增加和处理时间的延长, 宽叶雀稗幼苗株高等形态指标、生物量、渗透调节物质含量、抗氧化酶活性、叶绿素含量和光合参数呈先增后减的趋势, 低钙浓度(5-50 mmol·L^-1)环境下, 株高、叶长、叶宽、根长和生物量与对照(0 mmol·L^-1)相比均升高, 脯氨酸、可溶性蛋白和可溶性糖含量、过氧化物酶、过氧化氢酶和超氧化物歧化酶活性提高, 丙二醛含量和胞间CO₂浓度降低、叶绿素含量增加以及净光合速率、蒸腾速率和气孔导度增强; 高钙浓度(200 mmol·L^-1)环境下, 脯氨酸、可溶性蛋白和可溶性糖含量、过氧化物酶、过氧化氢酶和超氧化物歧化酶活性降低, 丙二醛含量和胞间CO₂浓度增加, 叶绿素含量减少以及净光合速率、蒸腾速率和气孔导度减弱。结合隶属函数分析, 低钙盐浓度(5-50 mmol·L^-1)处理对宽叶雀稗幼苗无抑制作用, 说明宽叶雀稗对低钙浓度具有一定的耐受性; 而在高钙浓度(200 mmol·L^-1)下, 宽叶雀稗幼苗通过提高自身有机渗透调节物质含量、增强酶活性、增加叶绿素含量以及增强光合作用等方式来快速调节植物生理代谢功能, 进而适应高钙浓度环境条件。     

Interaction of Photoprotective and Acclimation Mechanisms in Ulva rigida (Chlorophyta) in Response to Diurnal Changes in Solar Radiation in Southern Chile

Species of the genus Ulva (Chlorophyta) are regarded as opportunistic organisms, which efficiently adjust their metabolism to the prevailing environmental conditions. In this study, changes in chlorophyll‐a fluorescence‐based photoinhibition of photosynthesis, electron transport rates, photosynthetic pigments, lipid peroxidation, total phenolic compounds, and antioxidant metabolism were investigated during a diurnal cycle of natural solar radiation in summer (for 12 h) under two treatments: photosynthetically active radiation (PAR: 400–700 nm) and PAR+ ultraviolet (UV) radiation (280–700 nm). In the presence of PAR alone, Ulva rigida showed dynamic photoinhibition, and photosynthetic parameters and pigment concentrations decreased with the intensification of the radiation. On the other hand, under PAR+UV conditions a substantial decline up to 43% was detected and an incomplete fluorescence recovery, also, P‐I curve values remained low in relation to the initial condition. The phenolic compounds increased their concentration only in UV radiation treatments without showing a correlation with the antioxidant activity. The enzimatic activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased over 2‐fold respect at initial values during the onset of light intensity. In contrast, catalase (CAT) increased its activity rapidly in response to the radiation stress to reach maxima at 10 a.m. and decreasing during solar. The present study suggests that U. rigida is capable of acclimating to natural radiation stress relies on a concerted action of various physiological mechanisms that act at different times of the day and under different levels of environmental stress.     

Variations in Growth, Photosynthesis and Defense System Among Four Weed Species Under Increased UV-B Radiation

Weed tolerance of UV-B radiation varies with species, and the radiation could affect weed ecology and management. Variations In growth, photosynthesis and defense system among four important agronomic weeds, Abutllon theophrastl Medlk, Amaranthus retroflexus L., Digitaria sanguinalis （L.） Scop and Chloris virgata Swartz, under Increased UV-B radiation （ambient and increased radiation at 2.7, 5.4 and 10.8 kJ.m^-2.d-1） were studied In the greenhouse experiment. After 2 weeks of radiation, the shoots＇ dry mass decreased with increasing UV-B radiation except for D. sanguinalis. The reduction in biomass was the result of changes in morphology and physiology. Higher levels of UV-B treatment decreased the leaf area, plant height, net photosynthetic rate and chlorophyll contents, while it increased the contents of wax and UV-B absorbing compound in all species, except for A. retroflexus, which did not increase significantly. The activity of superoxide dismutase, catalase, ascorbate peroxide and the content of ascorblc acid changed differently among the weed species as UV-B radiation increased. D. sangulnalls was the most tolerant and A. retroflexus the most sensitive to increased UV-B radiation. The results also show that the two grass species （D. sanguinalis and C. virgata） were more tolerant to UV-B radiation than the two broadleafed species （A. theophrasti and A. retroflexus）. The UV-B absorbing compound and leaf wax played Important roles against UV-B damages in the two grass weeds. The overall results suggest that weed community, competition and management will be altered by continuous ozone depletion.     

自然条件下滤减UV-B辐射对烤烟光合色素含量的影响

在自然环境中,以烟草栽培品种K326为材料,通过覆盖不同透明薄膜滤减UV—B辐射,研究100％（CK）、75％（T1）、50％（T2）、35％（T3）UV—B辐射透过率处理下,不同强度UV—B辐射对烟草光合色素含量的影响。结果表明：烤烟三类光合色素对UV—B辐射有不同响应。类胡萝卜素对UV—B辐射响应较敏感。成熟初期,类胡萝卜素含量与UV—B辐射强度变化具有较好的正相关性,而chl a和chl b含量基本与UV—B辐射强度呈反向变化关系。成熟后期,由于UV—B辐射累积效应,光合色素含量变化没有明显规律。现蕾期至成熟采烤烟初期,chl a：chl b与UV—B辐射的反向变化关系较明显,后期则无明显规律,其含量的下降与UV—B辐射的累积效应有关。     

Biochar Application Improves the Drought Tolerance in Maize Seedlings

Application of biochar to agricultural soils is mostly used to improve soil fertility. Experimental treatments were comprised of two factors: i) drought at two level, i.e., 80% and 40% water holding capacity (WHC) which was maintained on gravimetric basis ii) three levels of biochar i.e., control, 2 t ha^-1 and 4 t ha^-1 added to soil. Experimentation was done to examine potential of biochar application to enhance the growth attributes, water relations, photosynthetic pigments and antioxidants activities in maize (Zea mays L.) seedlings. Results of study revealed that biochar application increased the growth qualities (total seedlings biomass, dry weight of shoot and root, shoot length and root length). In addition; contents of photosynthetic pigments (chlorophyll a, b, a + b and a/b), water relation (relative water contents, turgor potential, osmotic potential and water potential) were improved significantly due to addition of biochar. Addition of 4 t ha^-1 biochar led to significant rise activity of enzymatic antioxidant catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) in leaf of maize seedling sunder drought as well as well watered circumstances. However, biochar applied at the rate 4 t ha^-1 improved the all the physiological and biochemical attributes in maize seedlings under drought. From the results it was concluded that biochar application is an efficient way to alleviate adverse effect of drought stress on maize. In drought prone areas, long term impacts of biochar on production of maize and properties of soil could be recommended as upcoming shove.     

Growth and Nitrate Reductase Activity of Chlorella fusca Cells as Affected by Long Term Salinity

Influence of various saline media on Chlorella fusca growth, contents of photosynthetic pigments, and activity of the nitrate reductase (NRA) was determined. KCl, CaCl₂, and MgCl₂ in concentrations relative to NaCl as 1:1, 2:1, and 3:1 promote cell number, dry mass, and contents of photosynthetic pigments. The activity of NR was enhanced by Mg²⁺ and K⁺ and in some cases by Ca²⁺ at all ratios applied. This revised version was published online in July 2006 with corrections to the Cover Date.