The effects of enhanced UV-B radiation on physiological activity and growth of Norway spruce planted outdoors over 5 years

The responses of Norway spruce [Picea abies (L.) Karst.] to enhanced UV-B radiation during the 5-year treatment performed outdoors have been subjected to ecophysiological and growth analysis. The plants were exposed to UV-B radiation, simulating 17% ozone depletion. Ecophysiological parameters were monitored three times a year on three needle age classes, while growth was analysed at the end of each growth season. Spruce exhibited great variability in the amounts of photosynthetic pigments and methanol-soluble UV-B absorbing compounds, light use efficiency, photosynthesis and respiratory potential. The needle, branch and plant biomass production was not significantly affected during the 5-year treatment. The repeated-measures procedure comparing growth parameters through subsequent seasons, revealed a decrease of branch diameter under enhanced UV-B, which could be interpreted as a cumulative UV-B effect. The effects of UV-B radiation depended on needle development stage, interaction with environmental conditions and stresses. A reduced negative effect of UV-B radiation was observed during the prolonged drought in 2003, which was hypothesised as an alleviating effect. The tolerance of Norway spruce to elevated UV-B was to a large extent due to the high content of methanol-soluble UV-B absorbing compounds that was related neither to environmental conditions, including UV-B dose, nor to the developmental stage of the needles. The current year needles exhibited a tendency to increased production of UV-B absorbing compounds under elevated UV-B radiation. The outdoor study performed under variable environmental conditions showed great complexity of spruce response to enhanced UV-B.     

Changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to enhanced UV-B and to nitrogen addition

In the southeast of the Qinghai-Tibetan Plateau of China, Mono Maple is a common species in reforestation processes. The paper mainly investigated the changes in morphological, photosynthetic and physiological responses of Mono Maple seedlings to UV-B radiation, nitrogen supply and their combination. 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 a⁻¹)—to determine whether the adverse effects of UV-B on plants are eased by nitrogen supply. Enhanced UV-B caused a marked decline in growth parameters, net photosynthetic rate, and photosynthetic pigments, whereas it induced an increase in reaction oxygen species (hydrogen peroxide accumulation and the rate of superoxide radical production) and malondialdehyde content. Enhance UV-B also induced an increase in antioxidant compounds of Mono Maple, such as UV-B absorbing compounds, proline content, and activities of antioxidant enzymes (peroxidase, superoxide dimutase and catalase). On the other hand, nitrogen supply caused an increase in some growth parameters, net photosynthetic rate, photosynthetic pigments and antioxidant compounds (peroxidase, proline content and UV-B absorbing compounds), and reduced the content of reaction oxygen species (H₂O₂ accumulation, the rate of O₂⁻ production) and malondialdehyde content under ambient UV-B. However, under enhanced UV-B, nitrogen supply inhibited some growth parameters, and increased H₂O₂ accumulation, the rate of O₂⁻ production and MDA content, though proline content, UV-B absorbing compounds and activities of POD and SOD increased. These results implied that enhanced UV-B brought harmful effects on Mono Maple seedlings and nitrogen supply made plants more sensitive to enhanced UV-B, though increased some antioxidant activity.     

<Emphasis Type="Italic">Isatis indigotica</Emphasis> seedlings derived from laser stimulated seeds showed improved resistance to elevated UV-B

Sterilized seeds of Isatis indigotica (Brassicacae) were divided into four groups based on irradiation pretreatments. These control groups (C) were non irradiated, He–Ne laser treated seeds (L), UV-B treated seeds (B) and He–Ne laser followed by UV-B radiation treated seeds (LB). Laser radiation was provided by He–Ne laser, UV-B radiation was provided by filtered Qin brand 30 W fluorescent sun lamps. Malondialdehyde (MDA), proline, UV-B absorbing compounds and ascorbic acid (AsA) concentrations, as well as, the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were measured in the cotyledons of seedlings from all the four irradiation treatments. The result indicate that UV-B radiation enhanced the concentration of MDA while decreasing the activities of SOD, CAT, POD and the concentration of AsA in the seedlings compared with the controls. The concentration of MDA decreased, while the activities of SOD, CAT, POD and the concentration of AsA increased in seedling treated with He–Ne laser and UV-B compared to UV-B alone. The concentration of proline and UV absorbing compounds increased progressively with treatments i.e. UV-B irradiation, He–Ne laser irradiation, and He–Ne laser irradiation followed by UV-B irradiation compared to the controls. The present data suggest that Isatis indigotica seedlings derived from laser stimulated seeds showed improved resistance to elevated UV-B.     

NaCl induced cross-acclimation to UV-B radiation in four Barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.) cultivars

The effect of pre-treatment with 200 mM NaCl on the response of four barley cultivars (Hordeum vulgare L. cv. Bülbül-89, Kalaycı-97, Tarm-92 and Tokak-157/37) to UV-B radiation was investigated. Salt stress as well as UV-B irradiation led to a decrease of the total chlorophyll (chl) content in all cultivars, except in Kalaycı-97. While carotenoids are almost not affected by NaCl treatment, UV-B irradiation caused an increase by 5–20% of carotenoid content of all cultivars. UV-B induced damages of photosynthetic apparatus were estimated by the rate of photosynthetic electron transport measured by chl fluorescence and the rate of oxygen evolution, the latter being more affected. Pre-treatment with NaCl alleviated harmful effect of UV-B irradiation on F _v/F _m and ETR, but not on oxygen evolution. UV-B-induced and UV-B-absorbing compounds with absorption at 300 and 438 nm increased as a result of UV-B treatment. The level of stress marker proline increased considerably as a result of NaCl treatment, while UV-B irradiation resulted in a pronounced increase of the level of H₂O₂. MDA enhanced in the seedlings subjected to salt and UV-B stress. Established cross-acclimation to UV-B as a result of salt treatment could be due to the increased free proline and the level of UV-B absorbing compounds in barley seedlings subjected to NaCl.     

增强UV-B辐射及氮水平对长春花生长和生理代谢的影响

地表UV-B 辐射增强和氮沉降增加目前已成为影响植物生长的重要生态因子。本文以药用植物长春花（Catharanthus roseus）为材料,研究UV-B辐射和氮供应增加对长春花生长、生理及长春碱含量的协同效应。研究结果表明,紫外辐射增加对长春花生长和生物量积累具有显著的抑制作用。同时外源增加氮供应能明显缓解紫外辐射引起的生长抑制效应。紫外辐射引起的叶片膜脂过氧化胁迫导致了长春花叶片丙二醛含量显著增加,但同时增加氮供应能显著降低丙二醛水平。增强UV-B辐射处理显著促进长春花叶片UV-B吸收化合物合成积累,并随氮供应增加其含量进一步增加;氮供应增加和UV-B辐射增强共同作用时,长春花叶片中长春碱的含量较其单独作用时均显著增加。上述结果表明,增加氮供应不但可以缓解紫外辐射引起的生长抑制和生理伤害,同时对长春花叶片中生物碱的合成积累具有协同促进效应,其原因可能是增强UV-B辐射能促使长春花利用更多的氮源合成积累长春碱。     

云杉种子萌发和幼苗生长对气候变暖与UV B辐射增强的响应

采用开顶式有机玻璃罩(OTCs)及紫外灯分别模拟气候变暖和UV-B增强,对位于气候变暖和UV-B增强突出的青藏高原东缘的高山峡谷地云杉种子萌发、幼苗生长和光合色素含量的变化进行测定分析,探讨云杉对气候变暖和UV-B增强的响应机理。结果显示:(1)UV-B辐射增强对云杉种子萌发无显著影响,但显著抑制萌发幼苗的生长、降低其针叶叶绿素含量,并造成幼苗大量死亡(P<0.05)。(2)气候变暖使云杉种子提前萌发,并提高了发芽势、发芽率和发芽指数,促进幼苗生长和叶绿素的积累,显著降低幼苗死亡率(P<0.05)。(3)气候变暖缓解了UV-B增强对云杉萌发幼苗生长和叶绿素含量的抑制作用,并降低了UV-B胁迫下幼苗的死亡率。研究表明,在未来气候变暖和UV-B辐射增强同时存在时,气候变暖能够在一定程度上缓解UV-B增强对云杉林早期更新带来的抑制作用。     

低剂量微波辐射对增强UV-B辐射损伤菘蓝幼苗抗氧化酶活性的影响

为了探讨低剂量微波对增强UV-B辐射损伤菘蓝(Isatis indigotica Fort.)的修复作用,将经过10.08 kJ·m-2·d-1辐射损伤(PAR=220 μmol·m-2·s-1)的菘蓝幼苗分别经0、3、6、9和12 s等不同时间的微波辐照(126 mW·cm-2,2 450 MHz),然后测定其幼苗MDA含量、紫外吸收物质含量、抗坏血酸含量以及3种抗氧化酶SOD、CAT和POD活性.结果表明,增强UV-B辐射损伤菘蓝在微波的作用下其菘蓝幼苗中SOD、CAT和POD活性及紫外吸收物质含量、抗坏血酸含量提高,MDA含量得到显著的降低,说明微波对增强UV-B辐射伤害菘蓝幼苗具有修复作用.但是,随着微波剂量的增加,这种修复效应减弱,甚至消失.上述参数的变化说明适量时间的微波处理可以提高菘蓝对增强UV-B辐射的抵抗能力,并在此基础上初步探讨了微波的修复机理.     

Effects of UV-B radiation and additional irrigation on the Mediterranean evergreen sclerophyll Ceratonia siliqua L. under field conditions

Seedlings of Ceratonia siliqua L. were grown for 1 year in the field under ambient or ambient plus supplemental UV-B radiation (corresponding to 15% ozone depletion over Patras) and received two levels of additional irrigation during the summer dry period. The experiment was started during February 1998 and two major samplings were performed, the first at the end of the dry period (September 1998) and the second at the end of the experiment (January 1999). Plants receiving additional irrigation showed significantly higher leaf number, plant height and chlorophyll content at the end of the summer, but these differences were abolished at the final harvest. Plants growing under enhanced UV-B radiation had significantly fewer leaves and less nitrogen content at the end of the dry period, but these effects were also abolished at the final harvest, during which significant UV-B induced increases in stem dry mass were observed. None of the other measured parameters (mean leaf area, leaf dry mass, leaf thickness, UV-B absorbing compounds, phenolics, tannins and photochemical efficiency of PSII) were affected by either treatment. Combined UV-B / water effects were not significant. We may conclude that although some minor responses to enhanced UV-B radiation were evident, C. siliqua is resistant against UV-B radiation damage at the level applied.     

短期增强UV-B辐射对青榨槭幼苗生理特性的影响

在中国科学院茂县生态站选择2年生青榨槭幼苗进行室外盆栽实验,以人工增强0.27 W·m^-2(7.7kJ·m^-2·d^-1)的UV-B辐射剂量,研究模拟当地平流层臭氧削减1%时近地面太阳UV-B的增强对木本植物幼苗生理生态适应性的影响.处理0 d后,移除UV-B处理装置,就地测定气体交换参数和叶绿素荧光参数,并取样测定叶绿素及UV吸收物质含量.结果表明,增强UV-B辐射显著降低了青榨槭幼苗叶片最大净光合速率P_max(对照为6.214,处理为4.42),显著增加叶片暗呼吸速率Rd(对照为0.413,处理为1.29)和光补偿点LCP(对照为21.629,处理为9.861),但对表观量子速率a(对照为0.021,处理为0.032)影响不明显;它降低青榨槭幼苗每日净光合速率和水分利用效率,以及原初光化学效率(F_v/F_m)和实际光化学量子产量(ΦPS∏).此外,增强UV-B辐射使叶片叶绿素a、b含量降低(对照为16.23,.39,处理为13.17,4.93),但对叶绿素b含量影响未达显著水平.增强UV-B处理降低了青榨槭幼苗UV吸收物质含量(对照为0.87,处理为0.79).光合指标、叶绿素荧光指标和叶绿素含量的变化有较好的一致性,表明增强UV-B对青榨槭幼苗的光合作用可能有一定的抑制作用.     

UV-B辐射胁迫对杨桐幼苗生长及光合生理的影响

通过对UV-B辐射胁迫下亚热带典型木本杨桐幼苗的生长及光合生理的研究,探讨植物对于UV-B辐射胁迫的生理响应及适应性机理,进而揭示UV-B辐射变化对亚热带森林树种的影响.实验设置UV-B辐射滤光组、自然光对照组以及辐射增强组,选择亚热带典型树种杨桐(Cleyera japonica Thunb.)幼苗为实验材料.研究结果表明:(1)增强UV-B辐射会降低杨桐幼苗的叶绿素含量,而降低辐射则会显著促进叶绿素的增加,且这种胁迫在时间上具有积累性.(2)增强或降低辐射强度都会抑制杨桐地径的生长,增强辐射会产生更显著的抑制;降低辐射强度会对杨桐幼苗的株高生长产生促进作用,反之,则会抑制其生长.3个测定期数据综合分析显示随着处理时间的加长,这种胁迫作用有减小的趋势.(3)对光响应曲线的分析表明相对于自然光条件下的UV-B辐射,降低其强度对杨桐幼苗光合作用有显著的促进作用,反之则会抑制,不过抑制作用并不显著;对于光合特征参数的分析表明增强或降低UV-B辐射会显著降低杨桐幼苗的光饱和点(LSP)和光补偿点(LcP),而对最大净光合速率(Amax)、表观光合量子效率(AQY)、暗呼吸速率(Rd)影响均不显著,表明辐射胁迫对杨桐幼苗利用光能的效率影响不大,从而也并未对杨桐的光合作用产生显著性的伤害,但是由于森林树种的多年生特性,这种影响将是积累性的或延迟的,UV-B所造成的光合作用或光能利用率的微小变化都可能会积累成长期影响.因此,对森林树种进行长期研究是必要的.     

The effects of enhanced ultraviolet-B and nitrogen supply on growth,photosynthesis and nutrient status of <Emphasis Type="Italic">Abies faxoniana</Emphasis> seedlings

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.     

The influence of present-day levels of ultraviolet-B radiation on seedlings of two Southern Hemisphere temperate tree species

Seedlings of two Southern Hemisphere temperate trees species (mountain beech: Nothofagus solandri var. cliffortioides (Hook. f.) Poole and broadleaf: Griselinia littoralis Raoul) were grown in the field to determine the effects of present-day levels of ultraviolet-B radiation (UV-B) on growth, biomass, UV-B absorbing compounds, leaf optical properties and photoinhibition. Plants were covered with either UV-B transmitting or UV-B absorbing filters. After 125 days of typical summer weather, total biomass of both species was not affected by the UV-B treatments. Without UV-B, height increased (23%) and the number of leaves produced decreased (–21%) in beech, but broadleaf was unaffected. The effect of UV-B on beech height and leaf number was manifest during a second flush of leaves suggesting differences in response to UV-B of leaves initiated in different seasons and UV-B radiation regimes. Leaves of both species were essentially opaque to the transmission of UV-B. In the absence of UV-B the transmission of photosynthetically active radiation through leaves of both species increased, foliar nitrogen concentrations increased and levels of UV-B absorbing compounds decreased. In the youngest leaves of beech but not of broadleaf, removal of UV-B reduced midday photoinhibition, and did not alter the complete recovery of the fluorescence ratio F_V/F_M in the evening to predawn levels. As leaves of both species aged, midday photoinhibition decreased, with the result that UV-B had no effect on photoinhibition in mature leaves. Results of this experiment show that even under present-day UV-B levels, UV-B radiation modifies the physiology, optical properties and secondary compounds of leaves of both beech and broadleaf seedlings.     

Ultraviolet-B radiation effects on the Mediterranean ruderal Dittrichia viscosa

Young seedlings of Dittrichia viscosa L. (syn. Inula viscosa (L.) Aiton) (Asteraceae) were extensively treated with artificial rain in order to remove the water soluble component of their epicuticular UV-B absorbing compounds. As a result, 75% of the epicuticular absorbing capacity at 300 nm was lost. The seedlings were subsequently grown in a naturaly lit glasshouse for 80 days under 0.06, 6.41 and 10.14 kJ m^-2 day ^-1 biologicaly effective UV-B radiation doses. The initial, pre-rain values of the water soluble, epicuticular UV-B absorbing potential was restored in about three weeks. During this transient period the plants were exposed to the enhanced UV-B radiation doses with part of their UV-B radiation screen removed. Although a trend for increased accumulation of epicuticular UV-B absorbing capacity was observed with increasing UV-B radiation doses, the allelopathic potential of the epicuticular material remained unchanged. Internal (cellular) UV-B absorbing compounds and chlorophylls were unaffected, but total carotenoids were increased, indicating a possible protective role against UV-B radiation damage. Leaf, stem and root dry mass were the same under all treatments but UV-B radiation caused a reduction in the dry mass invested per unit leaf area with a concomitant increase in leaf area. The importance of this UV-B radiation induced selective allocation of photosynthate to the production of assimilative surfaces is discussed.     

茉莉酸对小麦幼苗UV-B抗性的生理学效应研究

以小麦品种‘西农88’(Triticum aestivum L.,cv.Xinong 88)为材料,研究了外源施加不同浓度茉莉酸(1、2.5、5、10 mmol/L)对UV-B辐射(1.5 kJ·m-2·d-1)下小麦幼苗光合色素、抗氧化酶、丙二醛、游离脯氨酸、紫外吸收物、花青素、根系活力等生理指标以及对其生长的影响,探讨了茉莉酸在UV-B辐射胁迫中的可能作用及其作用机制.研究结果表明,外源茉莉酸对小麦幼苗生理指标产生显著影响,并且表现出浓度效应,其中较低浓度的茉莉酸(1 mmol/L和2.5 mmol/L)能明显提高小麦幼苗的UV-B抗性.表现为低浓度茉莉酸显著提高UV-B辐射下小麦幼苗叶片中的总叶绿素含量、过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性.并且外源施加的茉莉酸还能够增加小麦幼苗的游离脯氨酸含量,降低脂质过氧化水平,提高花青素含量,增强根系活力.可见,茉莉酸通过提高小麦幼苗的抗氧化酶活性,增加渗透调节物含量以及保护性色素含量,从而缓解膜脂过氧化程度和提高防御物质含量,进而增强植物抵抗UV-B辐射胁迫的能力,保证小麦幼苗正常生长.     

Thiourea mediates alleviation of UV-B stress-induced damage in the Indian mustard (Brassica juncea L.)

Abstract

UV-B radiation (280–320 nm) as an environmental stress has damaging effect on plants and its overexposure can potentially interfere with growth and development. The effect of thiourea (TU) on UV-B stress tolerance of 10-day-old Brassica juncea seedlings subjected to supplementary UV-B for 5 days was investigated. An increase in the UV-B absorbing compounds anthocyanin, flavonoids and phenolic compounds was observed in UV-B + TU treated seedlings as compared to that of control. The enhanced synthesis of UV-B screening compounds resulted in lesser damage to chlorophyll and also gain in fresh weight and dry weight in UV-B + TU as compared to UV-B alone treatment. The enzymatic activities of guaiacol peroxidase (GPX) and superoxide dismutase (SOD) also increased in UV-B + TU. The expression profiling of phenylalanine ammonia lyase (pal) and chalcone synthase (chs) indicated an upregulation under UV-B + TU treatment, compared to that of control, suggesting that TU treatment ensured an early and efficient induction of flavonoid biosynthetic pathway. The results indicate that TU helps in ameliorating the damaging effects of UV-B stress by efficiently maintaining the antioxidant status and attenuating the penetration of the UV-B.     

增强UV-B辐射和氮素互作对植物生长代谢影响的研究进展

不同氮源条件下,UV-B辐射增强能改变植株对氮的吸收利用以及植株叶片的碳氢比和碳氮比,增加氨基酸的生物合成.缺氮条件下, UV-B辐射增强使植物叶片中SOD、POD活性增强,MDA含量增加;氮素过量时,UV-B辐射增强会降低植物对UV-B辐射的耐性.UV-B辐射增强和氮缺乏相互作用会降低叶片的光合速率、叶绿素含量、可溶性糖及淀粉含量,从而抑制植物的生长,降低生物量.该文对近年来国内外有关UV-B辐射增强与氮素相互作用对植物抗氧化系统、氮代谢、光合作用、生物量和形态结构的影响进行综述.     

Consequences of depletion of stratospheric ozone for terrestrial Antarctic ecosystems: the response of Deschampsia antarctica to enhanced UV-B radiation in a controlled environment

Mini UV lamps were installed over antarctic plants at Léonie Island, Antarctic peninsula, and shoot length measurements of Deschampsia antarctica were performed during the austral summer January–February 1999.We studied the response of the antarctic hairgrass, Deschampsia antarctica to enhanced UV-B. In a climate room experiment we exposed tillers of Deschampsia antarctica, collected at Léonie Island, Antarctic peninsula, to ambient and enhanced levels of UV-B radiation. In this climate room experiment with 0, 2.5 and 5 kJ m^–2 day^–1 UV-B_BE treatments we observed that length growth of shoots at 2.5 and 5 kJ m^–2 day^–1 UV-B_BE was markedly reduced compared to 0 kJ m^–2 day^–1 UV-B_BE. In addition, there was an increased number of shoots and increased leaf thickness with enhanced UV-B. The Relative Growth Rate (RGR) was not affected by UV-B, possibly because reduced shoot length growth by enhanced UV-B was compensated by increased tillering. Light response curves of net leaf photosynthesis of plants exposed to 5 kJ m^–2 day^–1 UV-B_BE did not differ from those exposed to 0 kJ m^–2 day^–1 UV-B_BE. The content of UV-B absorbing compounds of plants exposed to increasing UV-B did not significantly change.Mini UV-B lamp systems were installed in the field, to expose the terrestrial antarctic vegetation at Léonie Island to enhanced solar UV-B. In that study, the increment of shoot length of tagged plants of Deschampsia antarctica during the January-February 1999 at Léonie Island, was recorded and compared to shoot length growth under controlled conditions.The consequences of enhanced UV-B radiation as a result of ozone depletion for the terrestrial antarctic ecosytems are discussed.     

Combined effects of enhanced UV-B radiation and additional nutrients on growth of two Mediterranean plant species

Seedlings of two Mediterranean plants, the slow-growing, evergreen sclerophyll Ceratonia siliqua L. and the fast growing drought semi-deciduous Phlomis fruticosa L., were grown for one year in the field at ambient or ambient plus supplemental UV-B radiation (equivalent to a 15% ozone depletion) and two levels of applied fertilizers (NPK). The effects on growth, morphological, anatomical and physiological parameters were measured at final plant harvest. Additional nutrients increased leaf nitrogen, improved growth and reduced the root/shoot ratio in both plants, yet these effects were more pronounced in the fast growing P. fruticosa. A nutrient-induced increase in chlorophyll content was also observed in this plant. The growth responses to UV-B radiation were different for the two species. Growth in C. siliqua was not affected by UV-B radiation at both nutrient levels and the same was true for P. fruticosa at low nutrients. However, at the high nutrient level, supplemental UV-B radiation improved growth in P. fruticosa, indicating a strong interaction between the treatments. Photosystem II (PSII) photochemical efficiency, methanol-extractable UV-B absorbing capacity, total phenolics and tannins were not affected by either treatment in both plants. It is concluded that nutrient levels can strongly modify the UV-B radiation effects on growth of P. fruticosa. We presume that this may be correlated to the fast growing habit of this species.     

激光预处理可保护蚕豆细胞免受UV—B辐射的损伤

当蚕豆的胚被 He- Ne激光 (632 .8nm,1 .63J· mm- 2 )照射 5min或被 CO2 激光 (1 0 60nm,2 .53J· mm- 2 )照射 1 min后 ,将其置入 Knop营养液中进行恒温培养。当蚕豆的上胚轴长到大约 3cm时 ,在光背景 (PAR)为 70μmol· m- 2 · s- 1条件下 ,分别用 1 .0 2、3.0 3、4.52 k J· m- 2 的 UV- B辐射蚕豆的上胚轴 7h。根据蚕豆丙二醛 (MDA)、抗坏血酸 (As A)和 UV- B吸收物的含量变化 ,来测试激光对 UV- B照射蚕豆的上胚轴的保护作用。结果显示 :激光预处理可保护蚕豆上胚轴对 UV- B辐射的作用。与对照组 (没有用 UV- B或激光照射 )、UV- B单独照射组比较 ,在激光预处理的条件下 ,MDA的含量明显减少 ,As A和 UV- B吸收化合物的含量增加。如先用激光处理 ,然后再用 UV- B辐射 ,UV- B吸收物的含量将比单独用激光和 UV-B处理获得更好的改善。从而认为 ,激光预处理能增强植物对 UV- B的抵抗力。     

The influence of ultraviolet-B radiation on the growth, pigment production and chlorophyll fluorescence of Norway spruce seedlings

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-B_BE (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 R_fd, (R_fd=(F_m-F_s)/F_s) 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 (F_v/F_m). 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.