多蒴灰藓（苔藓植物门：藓纲）对短期极端温度的生理响应

近年来,藓类植物作为一类模式植物,在分子生物学、抗性生理学研究中受到重视,因此,开展逆境条件下藓类植物渗透调节物质和膜保护系统相关指标变化的研究,将为了解藓类植物对逆境条件适应的生理机制提供基础资料。多蒴灰藓（Hypnum fertile Senden.）分布广泛,生境多样,本文研究了低温(5℃)和高温(40℃和60℃)在不同胁迫时间(0、1、2、4、6、8h)下多蒴灰藓体内可溶性糖、游离脯氨酸、丙二醛（MDA）含量和过氧化物酶（POD）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性的变化,以期了解多蒴灰藓对不同温度条件的适应能力和响应的生理机制。结果表明：在5℃低温处理下,随处理时间延长,多蒴灰藓的可溶性糖含量逐渐增加,在高温处理下,呈现先升高后降低的趋势;游离脯氨酸、MDA在低温和高温胁迫下随处理时间延长都逐渐升高。CAT在5℃低温处理下活性逐渐升高,在40℃高温处理下先升高后降低,在60℃高温处理下则迅速降低,6 h后酶完全丧失活性。SOD的活性在5℃低温处理下随处理时间延长逐渐降低,在高温处理下则表现出先升高后降低趋势,40℃高温胁迫下6 h达到最大值,60℃胁迫下0.5 h达到最大值。POD在5℃和40℃处理下活性随处理时间延长逐渐升高,在60℃高温处理下则先升高后降低。这些结果表明,多蒴灰藓适生于20℃左右的温度条件下,60℃高温对多蒴灰藓的伤害明显,与高温相比,多蒴灰藓更适合生长于低温环境;多蒴灰藓通过增加游离脯氨酸以提高对温度逆境的适应;POD和CAT在多蒴灰藓抵御低温胁迫时可能起着主要作用,而SOD则在其抵御高温胁迫时起一定的作用。     

石生南亚毛灰藓在不同温度和干旱条件下的生理生化特性

通过模拟高温和干旱处理,对喀斯特石漠化生境中南亚毛灰藓(Homomallium simlaense(Mitt.)Broth.Mitt)在胁迫条件下生理特征的变化进行了研究。结果表明,南亚毛灰藓在高温和干旱条件下,各项生理指标均与相对含水量呈显著正相关;丙二醛、渗透调节物质和叶绿素含量均随处理时间的增加和含水量的降低而减少,但植株仍保持较高的可溶性糖含量以维持渗透压的平衡。在极端干旱和高温的条件下,南亚毛灰藓可通过降低生理活性,保持一定的可溶性糖含量度过胁迫期,同时丙二醛含量保持最低状态。高温和干旱处理结束后,进行复水处理,植株的渗透调节物质和丙二醛含量显著升高,光合作用迅速恢复。研究结果表明,南亚毛灰藓适应干旱和高温的极端条件可能与丙二醛含量有关,但复水结束后丙二醛含量升高,胁迫反而增强,说明南亚毛灰藓对高温和干旱具有一定耐受性,原因可能与其长期生存于喀斯特的石生环境有关。     

山杜英和黧蒴幼苗对干旱胁迫(PEG)的生理响应

以山杜英(Elaeocarpus sylvestris)和黧蒴(Castanopsis fissa)幼苗为试验材料,利用聚乙二醇6000(PEG-6000)人工模拟水分胁迫环境,设置三个胁迫强度处理(轻度、中度、重度)、三个胁迫持续时间处理(12h、24h、36h),以不加PEG-6000的1/2Hoagland营养液中的苗木作为对照,对2个树种幼苗的叶片相对含水量、相对电导率、脯氨酸含量、叶绿素含量、超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量和可溶性糖含量进行了测定,研究了水分胁迫对这2种幼苗的影响。结果表明:随着水分胁迫强度的加深及持续时间的延长,2种幼苗叶片相对含水量出现下降趋势,黧蒴的含水量下降更为显著;2种树种幼苗叶片内相对电导率呈波动性上升,黧蒴在轻度胁迫时相对电导率有大幅增加;2种幼苗的脯氨酸含量显著增加,叶绿素含量呈小幅波动,SOD活性先升后降,可溶性糖含量呈现波动性上升;山杜英叶片的MDA含量增加较缓慢,而黧蒴叶片的MDA含量大幅度增加。研究表明幼苗山杜英比黧蒴抗旱性强,叶片相对含水量、相对电导率和MDA含量可作为评价这2种苗木抗旱性的依据。     

Pb、Ni胁迫对大羽藓抗氧化酶系统的影响

研究了Pb、Ni单一及复合胁迫下大羽藓细胞活性氧自由基的累积与清除、光合系统和膜系统的受损情况及其抗氧化酶系统的变化.结果表明：在较低胁迫浓度(Pb<0.1 mmol·L^-1,Ni<0.01 mmol·L^-1)下,大羽藓叶绿素含量具有应激效应,在较高胁迫浓度(Pb>0.1 mmol·L^-1,Ni>0.01 mmol·L^-1)下则具有抑制效应;随Pb-Ni复合胁迫浓度的增加,苔藓活性氧自由基和丙二醛的累积量逐渐增大;大羽藓超氧化物歧化酶和过氧化氢酶活性降低,过氧化物酶活性增加,过氧化物酶在清除Pb、Ni胁迫产生的活性氧自由基的过程中起着重要作用.大羽藓丙二醛含量和过氧化氢酶活性对Pb、Ni胁迫具有浓度依赖性,可以将其作为监测该类重金属污染的生物标志物.     

高温胁迫下两种藓类植物过氧化物酶活性的变化

在不同的高温胁迫条件下 ,对湿地匍灯藓 (Plagiomnium acutum)和大羽藓 (Thuidium cymbifolium)过氧化物酶 (POD)活性及其与处理时间和处理温度的关系进行了初步研究。结果表明 ,在一定的温度范围内 ,随着温度的升高 ,POD活性增加 ,二者成线形关系。在一定温度条件下 ,一般随着处理时间的延长 ,POD活性增加。但是当超过一定的温度 (4 5～ 5 0°C)以及一定的处理时间 (4～ 6h) ,POD活性有所下降。结果还表明 ,湿地匍灯藓的POD活性显著高于大羽藓。而且在高温胁迫下 ,湿地匍灯藓 POD活性变化比大羽藓活跃 ,其变化幅度也比大羽藓大。     

Pb、Cd单一及复合污染对弯叶灰藓某些生理特性的影响

主要研究了Pb、Cd单一及复合污染对弯叶灰藓外部形态及总叶绿素含量的影响,结果表明:不同浓度的Pb、Cd对弯叶灰藓造成不同程度的伤害,随着Pb、Cd胁迫浓度的增加,弯叶灰藓表现出逐渐严重的伤害症状,总叶绿素的含量也随之下降,并且复合污染效应明显大于单一污染效应。     

紫外辐射对菜豆不同叶位叶片光合及保护酶活性的影响

以菜豆为实验材料,用紫外辐射处理,测定植物各叶位叶片的生理活性。结果表明,紫外辐射条件下,叶片的光合、蒸腾速率先升高,随后迅速降低,辐射处理3 h对光合作用的抑制程度随叶位升高而增加;第1叶气孔导度和胞间CO2浓度随辐射处理略有增加,而第2、3叶的则先升高随后降低;辐射处理使叶绿素含量先降低随后有所增加,但明显增加叶片丙二醛(MDA)含量;紫外辐射处理后,叶片过氧化物酶(POD)活性先升高随后降低,紫外辐射3 h第1叶POD活性比对照降低26.9%,辐射使第1叶超氧化物歧化酶(SOD)活性略有升高,但明显降低第2、3叶的SOD活性。     

铅胁迫对3种藓类植物抗氧化酶活性的影响

采用水培实验研究了重金属Pb对3种藓类植物尖叶拟船叶藓(Dolichomitriopsis diversiformis)、湿地匍灯藓(Plagiomnium acutum)和匍枝青藓(Brachythecium procumbens)的抗氧化酶(SOD、POD和CAT)活性的影响.结果表明,(1)在1~200 mg·L-1的铅胁迫浓度范围内,Pb对3种藓类植物的SOD活性均具有显著的促进作用,对Pb胁迫的种间敏感性差异为尖叶拟船叶藓>湿地匍灯藓>匍枝青藓;(2)POD活性对Pb胁迫的反应趋势有一定差别,尖叶拟船叶藓和匍枝青藓的POD活性随Pb浓度的增加先升后降,湿地匍灯藓的POD活性变化较为平缓,种间敏感性差异为匍枝青藓>尖叶拟船叶藓>湿地匍灯藓;(3)在100 mg·L-1时Pb对湿地匍灯藓CAT活性表现为显著促进作用外,其余在低浓度下显示无显著影响,在高浓度下表现为抑制效应,种间敏感性差异为尖叶拟船叶藓>匍枝青藓>湿地匍灯藓.3种藓类植物的抗氧化酶体系中对Pb胁迫的抵抗起关键作用的是SOD,可作为藓类植物受Pb胁迫的敏感生理指标.3种植物中对Pb胁迫的反应较为敏感的是尖叶拟船叶藓.     

温度和紫外辐射胁迫对西藏飞蝗抗氧化系统的影响

为探讨西藏飞蝗(Locusta migratoria tibetensis Chen)对环境的适应机制,报道了温度和紫外辐射胁迫对西藏飞蝗抗氧化系统影响。以西藏飞蝗成虫为试材,研究5—20℃低温、30—45℃高温胁迫和紫外线辐射对其抗氧化酶活性和膜脂过氧化物丙二醛(MDA)含量的影响。在5—20℃低温胁迫下,成虫体壁和消化道超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性及丙二醛(MDA)含量分别随温度降低而升高;在30—35℃高温胁迫下,成虫SOD、POD和CAT活性分别随温度升高而升高,当温度超过35℃时,3种氧化酶活性均下降。长波紫外辐射(UV-A)和中波紫外辐射(UV-B)对处理后24h和72h成虫的SOD活性的影响大于可见光,在UV-A、UV-B和可见光3种光波长处理下,成虫的POD和CAT活性随光照时间的延长而增加,其中UV-B对两种酶活性影响大于UV-A和可见光,表现为UV-B处理组>UV-A处理组>可见光处理组;UV-A和UV-B处理能导致虫体体壁MDA含量明显升高,且对脂质过氧化的诱导存在时间效应;雌虫体壁、雌虫消化道、雄虫体壁和雄虫消化道的MDA含量分别在UV-B72h、UV-A72h、UV-A72h和UV-B72h达最大值0.72、0.88、0.66和0.94 nmol/g鲜重。在20—5℃低温胁迫下,西藏飞蝗成虫抗氧化酶活性升高,能较好的保护自身免遭活性氧自由基的伤害;西藏飞蝗对高温忍耐力差,在高于35℃高温胁迫下,成虫SOD、POD、CAT活性均下降;在长波和中波紫外辐射下,西藏飞蝗抗氧化酶活性显著升高,是西藏飞蝗对紫外线辐射强度大的青藏高原的一种重要适应。     

铅胁迫对3种藓类植物细胞伤害及光合色素含量的影响

采用水培实验研究了重金属Pb2+胁迫下3种藓类植物[尖叶拟船叶藓(Dolichomitriopsis diversiformis)、湿地匍灯藓(Plagiomnium acutum)和匍枝青藓(Brachythecium procumbens)]的细胞伤害、光合色素含量和Pb2+累积量的变化,以探讨藓类植物对Pb2+胁迫的反应敏感性和耐性强弱.结果表明:(1)Pb2+胁迫导致尖叶拟船叶藓、湿地葡灯藓和匍枝青藓叶细胞显著损伤的最低浓度分别为100、1和10 mg·L-1,叶细胞伤害随Pb2+浓度的升高而显著增加,它们对高浓度Pb2+的耐受性顺序为尖叶拟船叶藓>湿地匍灯藓>匍枝青藓;(2)低浓度Pb2+胁迫(小于100 mg·L-1)对3种藓类植物的总叶绿素含量均没有影响,高浓度Pb2+胁迫则导致总叶绿素含量显著下降,降幅依次为匍枝青藓>湿地匍灯藓>尖叶拟船叶藓;叶绿素a/b值显示,高浓度Pb2+胁迫对尖叶拟船叶藓叶绿素b的抑制远大于叶绿素a,而对匍枝青藓和湿地葡灯藓使叶绿素a的抑制大于叶绿素b;当Pb2+胁迫浓度达到200 mg·L-1时3种藓类植物的类胡萝卜素含量显著降低;(3)3种藓类植物均能显著地富集Pb2+,高浓度Pb2+胁迫下,其富集能力急剧增加,而且与其耐受性呈正相关.     

Effects of ultraviolet-B radiation on cotton (Gossypium hirsutum L.) morphology and anatomy

Cotton (Gossypium hirsutum L.) crop, cultivated between 40 degrees N and 40 degrees S, is currently experiencing 2-11 kJ m-2 d-1 of UV-B radiation. This is predicted to increase in the near future. An experiment was conducted to study the effect of enhanced UV-B radiation on vegetative and reproductive morphology and leaf anatomy of cotton in sunlit, controlled environment chambers. From emergence to harvest, cotton plants were exposed to 0, 8 or 16 kJ m-2 d-1 of UV-B in a square wave approach for 8 h from 0800 to 1600 h. Changes in plant height, internode and branch length, mainstem node number, leaf area, length and area of petals and bracts, and anther number per flower were recorded. Epidermal cell and stomatal density, stomatal index, leaf thickness, and epidermal, palisade and mesophyll tissue thickness were also measured. Initial chlorotic symptoms on leaves turned into necrotic patches on continued exposure to enhanced UV-B. Exposure to high UV-B reduced both vegetative and reproductive parameters and resulted in a smaller canopy indicating sensitivity of cotton to UV-B radiation. Enhanced UV-B radiation increased epicuticular wax content on adaxial leaf surfaces, and stomatal index on both adaxial and abaxial leaf surfaces. Leaf thickness was reduced following exposure to UV-B owing to a decrease in thickness of both the palisade and mesophyll tissue, while the epidermal thickness remained unchanged. The vegetative parameters studied were affected only by high levels of UV-B (16 kJ m-2 d-1), whereas the reproductive parameters were reduced at both ambient (8 kJ m-2 d-1) and high UV-B levels. The study shows that cotton plants are sensitive to UV-B at both the whole plant and anatomical level.     

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.     

紫外线B对水稻叶组织中活性氧代谢及膜系统的影响

增强ＵＶ－Ｂ处理下,水稻叶片的Ｏ净产生速率、Ｈ２Ｏ２和ＭＤＡ含量以及膜透性都显著增加,敏感性弱的品种Ｏ２净产生速率和膜伤害程度较低。在ＵＶ－Ｂ处理初期活性氧清除系统的水平增高,但随着处理时间的延长,ＳＯＤ、ＣＡＴ和ＡＰ活性以及ＡＳＡ含量降低,其中ＡＰ和ＳＯＤ活性的下降最为明显,而敏感性弱的品种ＳＯＤ活性始终高于敏感性强的品种。处理１４ｄ后去掉ＵＶ－Ｂ,再经则１４ｄ上述各指标均恢复到与对照相近的水平。根据这些结果推测,水稻的ＵＶ－Ｂ伤害可能主要是由于ＳＯＤ活性的降低而导致Ｏ增生和膜脂过氧化。     

UV-B 辐射对番茄花粉生活力的影响与内源激素和多胺的关系

以成熟期不同的两个番茄品种同辉(早熟型)和霞光(晚熟型)为试材, 模拟兰州地区12%和20%臭氧层减薄时增强的UVB辐射(分别为T1=2.54 KJ.m-2.d-1和T2=4.25 KJ.m-2.d-1), 研究了大田条件下增强UV-B辐射对其花粉生活力的影响以及雄蕊中4种内源激素(IAA、GAs、ZR和ABA)和多胺(Put、Spm和Spd)及脯氨酸的变化。结果表明: 辐射抑制了同辉的花粉萌发和花粉管伸长, 但只降低了霞光的花粉萌发率; 两种辐射明显降低了两品种番茄雄蕊中的GAs含量, 同时造成同辉雄蕊中Put和Spd含量明显增加, Spm和Put/Spd+Spm比值显著降低; 霞光中3种多胺含量都显著减少, 导致高辐射时Put/Spd+Spm比值上升; 同辉番茄雄蕊的脯氨酸含量不受影响, 但高辐射使霞光番茄雄蕊的脯氨酸含量降低。实验表明, 两品种番茄花粉生活力的变化与增强UV-B 辐射下雄蕊中GAs水平、Spm含量以及脯氨酸含量的减少有关。雄蕊中多胺和脯氨酸含量变化对UVB辐射的响应说明霞光品种对UV-B辐射更敏感。     

Effects of Enhanced UV- B Radiation on Protein Metabolism of Bean Leaves

Bean ( Phaseolus vulgaris L. ) seedlings were grown in a greenhouse condition under UV-B (280 ~ 320 nm) radiation and an UV-B-free control condition. At early stage of bean growth, UV-B radiation(UV- BBE: 16 kJ·m-2·d-1 ) increased the synthetic rate of protein in bean leaves. UV-B radiation decreased the synthetic rate of protein and the content of soluble protein, increased the activities of caseolytic enzymes and the content of total amino acids in bean leaves at later growth stage. The results of SDS-PAGE indicated that UV-B radiation increased the contents of polypeptide in a range of 99 kD, 88 kD, 76 kD, 42 kD, 35 kD and 33 kD at the early stage, and increased that of 10 ~ 14 kD, 29 kD, 33 kD and 35 kD at later growth stage. It is suggested that the increase of these polypeptides is an adaptation response of plants to the enhanced UV-B radiation.     

Influence of high light and UV-B radiation on photosynthesis and D1 turnover in atrazine-tolerant and -sensitive cultivars of Brassica napus

An atrazine-tolerant mutant and an atrazine-sensitive cultivar of Brassica napus L. were grown under visible radiation (400 mumol m-2 s-1, photosynthetically active radiation, PAR) and then subjected to treatment conditions. These included short-term high PAR (1600 mumol m-2 s-1) which was given for 4 h either alone or in combination with an enhanced level of UV-BBE radiation (4.6 kJ m-2 h-1 biologically effective UV-B, 280-320 nm). Recovery from the radiation treatment was studied for 4 h under the light conditions for growth. Since it is known that the atrazine-tolerant mutant is susceptible to photoinhibition, one of the aims of the present study was to determine the effects of a supplemental, enhanced level of UV-B radiation with regard to the mutant. The results indicate an additive effect of UV-B radiation on Fv/Fm, photochemical yield and photosynthetic oxygen evolution during both exposure and recovery, and also a higher susceptibility of the mutant to photoinhibitory PAR conditions alone and in combination with UV-B, which may have implications in a changing environment. Both cultivars also showed a higher D1 turnover during the radiation stress than during recovery, as shown by immunoblotting and 35S-methionine incorporation measurements.     

Oxidative stress injury in tomato plants induced by supplemental UV-B radiation

Tomato (Lycopersicon esculentum Mill. cv. PKM 1) plants growing under field conditions were exposed for 15 d to solar radiation with UV-B component (280 - 320 nm) enhanced to 6.3 kJ m-2 d-1. This simulated a 15% stratospheric ozone depletion over Madurai (9° 50′ N latitude). Lipid peroxidation in the leaves of UV-B treated plants was 32% higher compared to the control. Superoxide dismutase (SOD) and catalase activities registered parallel promotion by 126 and 50 %, respectively, in the UV-B treated plants. Further, the contents of total phenols and anthocyanins in the leaves have also been enhanced by 40 and 156%, respectively. On the contrary, polyphenol oxidase activity demonstrated a 58 % inhibition in the leaves of UV-B treated plants. While anthocyanins and phenols are proposed to act as antioxidants, the reduction in polyphenol oxidase activity may maintain the turnover of phenols in the UV-B treated plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

增强UV-B辐射和He-Ne激光对小麦原生质体微管骨架的影响

以小麦叶片原生质体为材料,采用间接免疫荧光定位法标记其微管系统,并利用激光共聚焦扫描显微系统进行观察。研究了低剂量He-Ne激光(5mW.mm-2)、增强UV-B辐射(10.08kJ.m-2.d-1)及二者的复合处理对小麦幼苗叶肉细胞中微管骨架的影响。结果表明,增强UV-B辐射后,小麦叶片细胞中微管骨架发生解聚,呈短棒状或点状分布,微管束弥散且荧光强度减弱;而增强UV-B辐射后再施以He-Ne激光处理,小麦叶肉细胞微管骨架有部分断裂,但较单独UV-B处理组的损伤程度轻,说明低剂量的He-Ne激光可以部分修复增强UV-B辐射对微管骨架的损伤,且对微管的聚合有促进作用。     

Stratospheric ozone reduction and ecosystem processes: enhanced UV-B radiation affects chemical quality and decomposition of leaves of the dune grassland species Calamagrostis epigeios

This study reports changes in the plant's chemical composition and the decomposition of this plant material under enhanced solar UV-B radiation. Calamagrostis epigeios, a dominant grass species in the dune grassland in The Netherlands, was grown outdoor on an experimental field under ambient and enhanced solar UV-B (5 and 7.5 kJ m^-2 day^-1 UV-B_BE, respectively), corresponding to about 15% stratospheric ozone depletion. After one growing season aerial plant parts were harvested. The decomposition of this harvested leaf material was studied in a dune grassland and on the above mentioned experimental field under ambient (5 kJ m^-2 day^-1 UV-B_BE) and enhanced (7.5 kJ m^-2 day^-1 UV-B_BE) radiation, using litter bags. The chemical quality of the leaves grown under enhanced solar UV-B changed. There was an increase in the leaf content of lignin, while no significant changes occurred for the content of -cellulose, hemicellulose and tannins under enhanced UV-B. In the field, the rate of decomposition of leaf material grown under enhanced UV-B (with an increased content of lignin) was reduced. The content of lignin of the decomposing leaf material increased, but less under exposure to enhanced UV-B. The latter may be explained by photodegradation of the lignin. The consequences of enhanced UV-B radiation for carbon fluxes in the dune grassland ecosystem are discussed.