激波管壁AlO自由基B~2∑~+-X~2∑~+和C~2∏_r-X~2∑~+带系辐射光谱的研究

爆轰驱动过程中产生的高温高压气流对铝质膜片、激波管壁产生烧蚀和冲刷作用,以致激波管壁、端盖上附有氧化铝等杂质,而高温下AlO自由基在气体分子的高速碰撞下被激发并产生强烈的辐射,从而干扰了高温气体辐射光谱的分析。用爆轰驱动加热技术将空气加热到4 000~7 000 K,利用多通道光学分析仪对AlO自由基辐射光谱进行分析,实验发现在460~530 nm波长范围内有多支辐射非常强烈的AlO自由基B2Σ+-X2Σ+(T00=20 689 cm-1)带系辐射谱带,且每支谱带都由多个带头组成,带头间隔约为2 nm,带头处于高频位置并向低频方向伸延。通过实验与理论计算相结合,重点分析了AlO自由基B2Σ+-X2Σ+带系辐射光谱的结构特征。AlO自由基C2Πr-X2Σ+(T00=33 047 cm-1)带系辐射光谱处于270~335 nm波长范围内,其辐射强度相对于B2Σ+-X2Σ+带系较弱,并且与OH基A2Σ+-X2Π(T00=32 682 cm-1)带系辐射光谱互相干扰而难以分辨,对该波段高温空气的辐射光谱分析产生不利的影响。

青藏高原东缘几种树苗对增强紫外线-B和氮供应的响应

大气臭氧的损耗导致了地球表面具有生物学效应的紫外线-B(UV-B)辐射增强。同时，大气成分变化中除了UV-B辐射增强外，氮沉降是一个新近出现而又令人担忧的环境问题，其来源和分布正在迅速扩展到全球范围，并不断向陆地和水生生态系统沉降。本试验在四川省境内的中国科学院茂县生态站内进行，以云山、冷杉、色木槭和红椋子幼苗为模式植物，从生长形态、光合作用、抗氧化能力和矿质营养等方面研究了青藏高原东缘4种树苗对全球变化－增强UV-B辐射和氮供应(氮沉降)的响应。该试验为室外盆栽试验，包括四个处理：(1)大气UV-B辐射+无额外的氮供应(C)；(2)大气UV-B辐射+额外的氮供应(N)；(3)增强UV-B辐射+无额外的氮供应(UV-B)；(4)增强UV-B辐射+额外的氮供应(UV-B+N)。其目的：一方面有助于丰富我国对全球变化及区域响应研究的全面认识，进一步完善在全球气候变化条件下臭氧层削减和氮沉降对陆地生态系统影响的内容；另一方面，在一定程度上有助于我们更好的理解在全球变化下森林更新的早期过程。具体结果如下： 增强的UV-B辐射在生长形态、光合、抗氧化能力、活性氧和矿质营养方面对4种幼苗都有显著的影响。UV-B辐射增强对幼苗的影响不仅与物种有关，而且，还与氮营养水平相关。总体表现为，高的UV-B辐射导致了色木槭和红椋子幼苗叶片的皱缩和卷曲，并降低了色木槭幼苗的叶片数和叶重，在额外的氮供应下，云杉、冷杉和红椋子的叶重也显著地降低了；色木槭和红椋子幼苗叶片的解剖结构受到了增强的UV-B辐射的影响，增强的UV-B辐射显著地降低了色木槭叶片的栅栏组织厚度，提高了红椋子叶片的厚度；增强的UV-B辐射显著地降低了4种幼苗的单株总生物量、植物地下部分的生长、总叶绿素含量 [Chl (a + b)]、净光合速率和最大量子产量(Fv/Fm)，提高了4种幼苗叶片的膜脂过氧化(MDA含量)，改变了植物体不同器官中的矿质元素含量；增强的UV-B辐射提高了冷杉、色木槭和红椋子叶片中的过氧化氢含量(H2O2)、超氧负离子(O2-)生成速率，在额外的氮供应下，云杉叶片中的活性氧含量也显著地提高了；在无额外的氮供应条件下，增强的UV-B辐射显著地提高了4种幼苗叶片中的UV-B吸收物质、脯氨酸含量和抗氧化酶的活性(SOD、POD、CAT、GR和APX)。在额外的氮供应条件下，UV-B辐射的增强却显著地降低了冷杉叶片中脯氨酸含量和红椋子叶片中UV-B吸收物质含量，但是，在4种幼苗叶片中，5种抗氧化酶的活性对UV-B辐射的增强没有明显的规律性，增强的UV-B辐射显著地提高了云杉叶片中的POD、SOD和GR的活性，提高了冷杉叶片中的POD和GR活性，提高了色木槭叶片中的POD、SOD和CAT活性和红椋子幼苗叶片中的POD和SOD活性。从这些结果可知，植物在遭受高的UV-B辐射导致的过氧化胁迫时，植物体内形成了一定的保护机制，但是，这种保护不能抵抗高的UV-B辐射对植物的伤害。 额外的氮供应在生长形态、光合、抗氧化能力、活性氧和矿质营养方面对4种幼苗都有一定的影响，不同幼苗对额外的氮供应响应不同，并且受到UV-B辐射水平的影响。在当地现有的UV-B辐射水平下，额外的氮供应显著地提高了幼苗的单株总生物量、植物地下部分的生长、Chl (a + b)、净光合速率(红椋子除外)、UV-B吸收物质(冷杉除外)、脯氨酸含量(红椋子除外)和部分抗氧化酶的活性，降低了H2O2的含量、O2-的生成速率和MDA含量(红椋子除外)，改变了植物体内部分矿质元素含量，显著地提高了云杉和冷杉叶片中的Fv/Fm。这些指标总体表明，在当地现有大气UV-B辐射水平下，额外的氮供应对植物的生长和发育是有利的。在增强的UV-B辐射水平下，4种幼苗的生长形态和光合大部分指标都没有受到额外氮供应的影响，额外的氮供应提高了红椋子幼苗的单株总生物量和Chl (a + b)含量，提高了冷杉和色木槭叶片中的活性氧含量和MDA含量，却降低了红椋子叶片中的活性氧含量；额外的氮供应也提高了云杉、色木槭和红椋子叶片中UV-B吸收物质和脯氨酸含量，降低了冷杉叶片中UV-B吸收物质和脯氨酸含量；在抗氧化酶活性方面，额外的氮供应降低了云杉、冷杉叶片中5种抗氧化酶的活性和红椋子叶片中POD和GR的活性，提高了色木槭叶片中的POD和SOD的活性；4种幼苗植物体内的矿质元素含量对额外的氮供应没有显著的规律性。从这些结果可知，在高的UV-B辐射下，额外的氮供应提高了云杉、冷杉和色木槭幼苗对高的UV-B辐射的敏感性，然而，额外的氮供应却促进了红椋子幼苗的生长，原因可能是，在高的UV-B辐射下，额外的氮供应增加了红椋子叶片的厚度、叶重和叶片数，降低了叶片中活性氧含量的结果。表明在高的UV-B辐射水平下，额外的氮供应降低了红椋子幼苗对高的UV-B辐射的敏感性。 在全球变化的趋势下，UV-B辐射增强和氮沉降可能同时存在，我们的研究表明，与大气UV-B辐射+无额外的氮供应处理相比，增强UV-B辐射+额外的氮供应处理显著地降低了幼苗的单株总生物量(红椋子除外)、Chl (a + b)、净光合速率、Fv/Fm(冷杉除外)和MDA含量(红椋子除外)，提高了活性氧含量 (云杉除外)、UV-B紫外吸收物质含量(冷杉除外)、脯氨酸含量和部分抗氧化酶的活性，改变了植物体不同器官中的矿质元素含量。结果表明，在当地现有条件下，全球变化(UV-B辐射增强和氮沉降)对云杉、冷杉和色木槭幼苗的生长是不利，尽管植物体内一些抗氧化性指标提高了，然而，却对红椋子幼苗的单株总生物量的累积没有显著的影响。 The depletion of the ozone led to the increase of ultraviolet-B (UV-B) with biological effects in the earth’s surface. At the same time, except for enhanced UV-B radiation, nitrogen deposition was an anxious environmental problem at present, rapidly expanding to the global scope and continuously depositing to land and aquatic ecosystem. The experiment was conducted in Maoxian Ecological Station of Chinese Academy of Sciences, Sichuan province, China. Picea asperata, Abies faxoniana, Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings were selected as model plants to assess the effects of enhanced UV-B radiation and supplemental nitrogen supply on growth, morphological, photosynthesis, antioxidant and mineral nutrient traits of 4 species seedlings in east Qinghai-Tibetan Plateau. The experiment was potted outdoor, including 4 treatments: (1) ambient UV-B without supplemental nitrogen (control, C); (2) ambient UV-B with supplemental nitrogen (N); (3) enhanced UV-B without supplemental nitrogen (UV-B); (4) enhanced UV-B with supplemental nitrogen (UV-B+N). One hand, it was helpful for enriching our country to comprehensive understanding of the researches in the global change and the region response, further perfecting the effects of the depleted ozone layer and nitrogen deposition on land ecosystem under the global change; the other hand, it was favorable for us to better understanding of the early process of forest renews under the global change. The results were as follows: Enhanced UV-B radiation had significant effects on 4 species seedlings in growth, morphological, photosynthesis, antioxidant and mineral nutrient traits of 4 species seedlings. The effects of enhanced UV-B on plants were not only related with species, but also related with nitrogen nutrient level. Generally, the increase of UV-B radiation led to the shrinkage and curl of leaves in Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings, and reduced the number of leaf and leaf weight of Acer mono Maxim seedlings, under supplemental nitrogen supply, leaf weight of Picea asperata, Abies faxoniana and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings significantly also reduced; the anatomical features of leaf in Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings affected by enhanced UV-B radiation, the increase of UV-B radiation markedly reduced the palisade tissue thickness of Acer mono Maxim leaf and enhanced the leaf thickness of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings; the enhanced UV-B radiation significantly reduced total biomass per plant of 4 species seedlings, the growth of the underground parts, Chl (a + b), net photosynthetic rate and maximum potential quantum yield of photosynthesis (Fv/Fm), and increased the degree of lipid peroxidation (MDA content) and changed the content of mineral elements in different parts of plants; the enhanced UV-B radiation also increased the rate of superoxide radical (O2-) production and hydrogen peroxide (H2O2) content in leaves of Abies faxoniana, Acer mono Maxim, Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings, under supplemental nitrogen supply, the reactive oxygen species in leaves of Picea asperata seedlings also significantly increased by enhanced UV-B radiation; under without supplemental nitrogen supply, enhanced UV-B radiation evidently induced an increase in UV-B absorbing compounds, proline content and the activities of antioxidant enzymes (SOD, POD, CAT, GR and APX) of leaves in 4 species seedlings. Under supplemental nitrogen supply, enhanced UV-B radiation induced a decrease in proline content of leaves in Abies faxoniana seedlings and UV-B absorbing compounds of leaves in Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings, but, there were no obvious rules in the activities of five antioxidant enzymes of 4 species seedling leaves to enhanced UV-B radiation, enhanced UV-B radiation significantly increased the activities of POD, SOD and GR in Picea asperata leaves, the activities of POD and GR in Abies faxoniana leaves and the activities of POD, SOD and CAT in Acer mono Maxim leaves. The results indicated that some protective mechanism was formed when plants were exposed to enhanced UV-B radiation, but the protection could not counteract the harm of high UV-B radiation on plants. Supplemental nitrogen supply had some effects on 4 species seedlings in growth, morphological, photosynthesis, antioxidant and mineral nutrient traits. The response of 4 species seedlings was different to supplemental nitrogen supply, and was affected by UV-B levels. Under local ambient UV-B radiation, supplemental nitrogen supply significantly increased the total biomass per plant, the growth of underground parts, Chl (a + b), net photosynthetic rate (except for Acer mono Maxim seedlings), UV-B absorbing compounds (except for Abies faxoniana seedlings), proline content (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings) and the activities of some antioxidant enzymes, and reduced H2O2 content, the rate of O2- production and MDA content (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings) and changed the content of mineral elemental in different parts; supplemental nitrogen supply also evidently increased Fv/Fm in Picea asperata and Abies faxoniana seedlings. These results indicated that supplemental nitrogen supply was favorable for the growth of plants under local ambient UV-B radiation. Under enhanced UV-B radiation, mostly parameters in growth and morphology of 4 species seedlings were not affected by supplemental nitrogen supply. Supplemental nitrogen supply increased the total biomass per plant and Chl (a + b) of Swida hemsleyi (Schneid. et Wanger.) Sojak seedling, increased the reactive oxygen species and MDA content in Abies faxoniana and Acer mono Maxim leaves, and reduced the reactive oxygen species in Swida hemsleyi (Schneid. et Wanger.) Sojak leaves; supplemental nitrogen supply also increased UV-B absorbing compounds and proline content in Picea asperata, Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak leaves, decreased UV-B absorbing compounds and proline content in Abies faxoniana leaves; in the activities of antioxidant enzymes, supplemental nitrogen supply significantly reduced the activities of antioxidant enzymes in Picea asperata and Abies faxoniana leaves and the activities of POD and GR in Swida hemsleyi (Schneid. et Wanger.) Sojak leaves, and increased the activities of POD and SOD in Acer mono Maxim leaves; the content of mineral elements in 4 species seedlings was no significantly rule to supplemental nitrogen supply. We knew from the results, under enhanced UV-B radiation, supplemental nitrogen supply made Picea asperata, Acer faxoniana and Acer mono Maxim seedlings more sensitivity to enhanced UV-B radiation, however, accelerated the growth of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings. The reason was probably that supplemental nitrogen supply increased the leaf thickness, leaf weight and leaf number, reduced the reactive oxygen content of leaf in Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings grown under high UV-B radiation. This showed that supplemental nitrogen supply reduced the sensitivity of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings to high UV-B radiation. Under the tendency of the global change, enhanced UV-B radiation and nitrogen deposition may probably coexist. The results showed, compared with the treatment of ambient UV-B radiation without supplemental nitrogen supply, the treatment of enhanced UV-B radiation with supplemental nitrogen supply significantly reduced the total biomass per plants (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings), Chl (a + b), net photosynthetic rate, Fv/Fm and MDA content (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings), and increased reactive oxygen content (except for Picea asperata seedlings), UV-B absorbing compounds (except for Abies faxoniana seedlings), proline content and part antioxidant enzymes, and changed the content of mineral elements of different parts. The results indicated that the global change (enhanced UV-B and nitrogen deposition) were not favorable for the growth of plants under local ambient UV-B radiation and nitrogen nutrient level,, though increased some antioxidant indexes, however, the treatment of enhanced UV-B with supplement nitrogen supply did not significantly affect on the biomass accumulation of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings.

荞麦(Fagopyrum tataricum Gaertn.和F. esculentum Moench.)对紫外线B辐射的响应研究

近二十多年来，基于对臭氧层衰减、紫外线B（UV-B）增强的担心，研究者希望了解到紫外线辐射对不同作物的影响情况，增强UV-B辐射条件下是否对作物的生长发育、产量质量构成威胁。在本试验中，我们首先探讨了双子叶作物黄瓜（Cucumis sativus）和大豆（Glycine max）对不同紫外波段的生物效应[分别为B-UVA（315-400 nm），N-UVA（315-340 nm），B-UVB（275-400 nm）和N-UVB（290-340 nm），UV-（>400nm）作对照]。我们观察到所有的UV波段处理都使黄瓜和大豆的生长受到抑制，并且细胞受到不同程度的氧化伤害；UV波段处理的作用效果与不同波段的紫外有效生物辐射剂量有关。处理差异在UV-B波段内部和UV-A波段内部同样存在。植物生长UV辐射公式（BSWF）能很好的预测本试验UV-B波段内的平均植物效应，但不能预测UV-A波段的植物效应。短波UV-A的生物作用强于长波UV-A。光合色素的变化与UV波谱差异和种间差异有关。在高的紫外/可见光背景下，UV-A处理同UV-B同样导致光合色素的降低，但黄瓜类胡萝卜素/叶绿素比例升高。与其他研究者的试验结果比较后，我们认为紫外线B辐射的生物效应一致性很高，但紫外线A波段的生物学效应存在较大争议。因此我们在本试验的基础上仅进行荞麦[苦荞(Fagopyrum tataricum Gaertn.)和甜荞(Fagopyrum esculentum Moench.)]对紫外线B波段的响应研究。 我们对苦荞品种-圆籽荞进行了连续两个生长季节的大田半控制试验以观察UV-B辐射对苦荞生长、发育、产量及叶片色素的影响；试验小区进行降低UV-B、近充足UV-B和增强UV-B辐射处理。我们的试验表明在不同强度UV-B辐射下苦荞的生长、地上部生物量积累及最终产量都有所下降，但苦荞的发育加快；当前条件下的日光紫外线B辐射对植物生长和产量也造成负面影响。植物光合色素被日光及增强UV-B辐射降低；UV化合物及卢丁含量在中低剂量的UV-B辐射强度下显著升高，但在高剂量的增强UV-B辐射下短期升高后迅速下降。我们的试验表明苦荞是一个对UV-B高度敏感的作物。苦荞对UV-B的敏感性与UV-B剂量、外界环境因素及生长季节有关。 单个苦荞品种的试验结果使我们认识到外界UV-B辐射已经对苦荞生长发育构成逆境条件，未来全球气候变化条件下增强紫外线B辐射可能使其处于更不利的生长环境中。因此我们有进行了多个种群进行UV-B响应观察并筛选耐性种群。我们对15个苦荞种群进行增强UV-B辐射处理（6.30 kJ m2 UV-BBE，模拟当地25%的臭氧衰减），我们观察苦荞UV-B辐射效应存在显著的种内差异，UV-B辐射对多数种群具有抑制作用，但对一些种群还有刺激作用。我们采用主成分分析方法与作物UV-B响应指数（RI）来评价苦荞作物UV-B辐射耐性。我们发现作物的UV-B耐性不仅与其原产地背景UV-B强度有关，而且与作物相对生长效率、次生代谢产物含量（如卢丁）及其他因素有关。我们观察到苦荞伸展叶总叶绿素变化与UV-B耐性成正相关；室内苦荞幼苗的UV-B辐射致死试验表明：苦荞种群死亡率与其UV-B耐性成负相关。 此外，我们对甜荞的UV-B辐射响应也进行了初步研究。选取美姑甜荞、巧家甜荞和云龙甜荞进行5个梯度的增强UV-B辐射室外模拟试验。我们观察到UV-B辐射显著降低了甜荞的生长、生物量及产量；并严重影响了甜荞的生殖生长，降低了花序数、种子数和结实率；并且UV-B辐射对甜荞的抑制作用存在显著的剂量效应。三种甜荞品种存在显著的种内差异，其中美姑品种UV-B耐性最强，且膜脂受UV-B辐射氧化伤害最小，这与该品种UV-B辐射下较高的GR酶活性、APX酶活性和PPO酶活性、以及含量更高的抗坏血酸有关。甜荞的次生代谢也受到增强UV-B辐射的影响，其香豆酰类化合物在UV-B辐射下升高显著，而槲皮素含量也在高剂量UV-B辐射下有所增加；卢丁含量依赖UV-B辐射剂量而变化，中低剂量UV-B辐射下其卢丁含量逐渐升高，但在高剂量辐射下逐渐下降。 通过对生长在高海拔地区的荞麦作物(苦荞和甜荞)进行的室外研究，我们认识到作物不同品种存在很大的耐性差异，这就为UV-B耐性育种创造了有利条件。进一步加大荞麦种质资源筛选力度并深入认识荞麦抗性机理，在此基础上通过杂交或其他基因融合手段培育抗性品种，对高剂量UV-B辐射地区的荞麦产量的提高将起到重要推动作用，并使荞麦生产能有效应对未来全球气候变化条件下UV-B辐射可能升高的威胁。 During last few decades, due to concern of ozone layer depletion and enhancement of ultraviolet B radiation（UV-B, 280-315 nm), the agronomist want to know the responses of different crop species to UV-B. In the first experiment of our study, the effect of different UV band [B-UVA（315-400 nm), N-UVA（315-340 nm), B-UVB（275-400 nm), N-UVB（290-340 nm）and UV-（>400nm, as control)] on the cucumber（Cucumis sativus）and soybean（Glycine max）were investigated in growth room. Spectra-dependent differences in growth and oxidation indices existed within UV-A bands as well as UV-B bands. The general biological effects of different band were UV- ＜ B-UVA＜ N-UVA＜N-UVB＜B-UVB. The plant growth biologically spectra weighting function（BSWF）matched well with average plant response in UV-B region, but not in UV-A region. Shorter UV-A wavelength imposed more negative impact than longer UV-A wavelength did in both species. The effect on photosynthetic pigment was related to different UV bands and different species. The photosynthetic pigment content was decreased by UV-A spectra as well as UV-B spectra. In comparison with the results of previous studies, we found that the wavelength-dependent biological effect of ultraviolet B radiation has high consistency, but the biological effect of ultraviolet-A radiation was inconsistent. We narrow our following study on the effect of ultraviolet B radiation on the buckwheat（tartary buckwheat and common buckwheat). The tartary buckwheat（Fagopyrum tataricum Gaertn.）cultivars Yuanziqiao was grown in the sheltered field plots for two consecutive seasons under reduced, near-ambient and two supplemental levels of UV-B radiation. The crop growth, photosynthetic pigments, total biomass, final seed yield and thousand-grain weight were decreased by near-ambient and enhanced UV-B radiation, while crop development was promoted by enhanced UV-B radiation. Leaf rutin concentration and UV-B absorbing compound was generally increased by UV-B with the exception of 8.50 kJ m-2 day-1 supplemental levels. Our results showed that tartary buckwheat is a potentially UV-B sensitive species. Study on one cultivars showed that ambient solar radiation had present a stress to tartary buckwheat. This makes it necessary to observe the UV-B response of many cultivars and screen tolerant cultivars. Fifteen populations of tartary buckwheat were experienced enhanced UV-B radiation simulating 25% depletion of the stratospheric ozone layer in Kunming region, and plant responses in growth, morphology and productivity were observed. Principal components analysis（PCA）was used to evaluate overall sensitivity of plant response to UV-B as well as response index. The different populations exhibited significant differences in responses to UV-B. The photosynthetic pigments of young seedlings were also affected significantly under field condition. On the other hand, the healthy seedlings of different populations were exposed to the high level of UV-B radiation in growth chambers to determine the plant lethality rate. The plant tolerance evaluated by multivariate analysis was positively related to total plant chlorophyll change, but negatively related to lethality rate. In other hand, the UV-B responses of the other important cultivated buckwheat species, common buckwheat（Fagopyrum esculentum Moench.), were also studied preliminarily. Three widespread cultivated variety（Meigu, Qiaojia and Yunlong cultivars）were provided with five level of enhanced UV-B radiation outdoors. We observed that the crop growth, development and production were significantly decreased, and reproductive production, like anthotaxy number, seed number and seed setting ratio, was also decreased. Dose-dependent inhibition effect caused by enhanced UV-B radiation also existed in common buckwheat. Significant intraspecific difference existed in those three cultivars. The Meigu cultivars with dwarfed growth and lower production have highest UV-B tolerance as well as lowest damage in cell membrane, this could be associated with profound enhancements of glutathione reductase（GR）activity, ascorbate peroxidase activity and polyphenol oxidase activity as well as higher ascorbic acid concentration. The secondary metabolism was also affected by UV-B radiation, with profound elevation of coumarin compound and moderate increase of quercetin concentration. Rutin concentration was peaked in 5kJ m-2 UV-B. The contrasting effect of UV-B radiation on different populations indicated that there existed abundant genetic resources for selecting tolerant populations of common and tartary buckwheat. Much effort needed be pose on screening of buckwheat germplasm and clarification of mechanism of buckwheat tolerance to UV-B. On this base the tolerant cultivars could be bred by hybridization and other gene transfusion method, this would help increase buckwheat yield in high ambient UV-B region and counteract the effect of possible enhanced UV-B radiation in future.

青杨组(Populus section Tacamahaca Spach)不同种对增强UV-B的反应差异

人类向大气中排放的大量氮氧化合物和氟氯烃类化合物(CFC’s)引起臭氧分子的分解，导致到达地球表面的紫外辐射增加，特别是UV-B辐射增强。本项目以青杨组杨树为模式植物，从形态和生理方面研究了来自不同UV-B背景下的康定杨与青杨在增强UV-B下的反应及其反应差异,并探讨了干旱、施肥对它们抗UV-B能力的影响。杨树具有分布广、适应性强、在生态环境治理和解决木材短缺方面均占有重要位置，研究成果可为生态系统的恢复与重建提供理论依据和科学指导。主要研究结果有以下： 1. 在温室中经过增强UV-B处理，杨树的外部形态及生理活动受到了一定程度的影响。增强UV-B导致康定杨、青杨的生物量、叶面积及节间长度降低，叶片增厚，SOD活性升高，膜伤害增加，而对叶片数目、R/S、叶绿素A、叶绿素B及整个叶绿素含量没有影响。两种杨树对UV-B胁迫的响应存在差异：在增强UV-B条件下，青杨的植株高度、生物量、叶面积、脯氨酸含量、长期用水效率受到的影响大于康定杨，相比而言，康定杨在比叶面积、叶片厚度、可溶性糖含量、UV-B吸收物质的含量及SOD和GPX活性方面增加的程度大于青杨。这些区别说明，来自于高海拔的康定杨比来自于低海拔的青杨对增强UV-B 具有更强的耐性。我们认为二者在叶片厚度、比叶面积、UV-B吸收物质含量及SOD、GPX活性差异是导致对增强UV-B耐性不同的原因。 2. 干旱与增强UV-B对杨树的生长和生理特性均产生了影响，而且两种胁迫共同作用时干旱表现减弱或加剧了UV-B对杨树某些形态和生理特性的影响。 据试验结果，干旱显著地降低了杨树的株高、叶片数目、叶面积，增加了叶片厚度，促进ABA的积累，提高了CAT活性。对于干旱，两种杨树之间也表现出了一定的差异性。可溶性蛋白质和脯氨酸在青杨叶片中得到显著积累，而在康定杨中没有变化。此外，CAT、长期用水效率在康定杨中受到的影响更加明显。长期用水效率的不同变化趋势说明两种杨树对水分胁迫采用了不同的用水策略，康定杨采用的是节水用水策略，提高用水效率，而青杨采用的是耗水的用水策略。根据干旱对叶面积、脯氨酸、ABA含量、CAT活性及长期用水效率等方面的影响，我们认为来自高海拔地区的康定杨比来自低海拔的青杨有更大的耐旱性，这是对生长环境长期适应的结果。在高海拔地区，因霜冻常带来土壤水分不可利用，降低了根系对水分的吸收，树木容易受到的生理性干旱。另外，高海拔的地区低的气温使植株对严寒有较强的耐性，减少了水分的需要。 生长于增强UV-B下的康定杨和青杨植株表现为高度降低，叶面积缩小，比叶面积增加；叶片栅栏组织、海绵组织均受到增强UV-B的影响，其厚度的增加导致整个叶片变厚。增强UV-B还显著提高了杨树的APX活性、UV-B吸收物质含量，而对叶片数目、ABA、可溶性蛋白质含量及CAT活性没有产生影响。试验中也观察到了两种杨树对增强UV-B响应的差异：与康定杨相比，在增强UV-B下青杨株高、叶面积降低的程度更大一些，SOD活性显著提高。另外UV-B吸收物质受到的影响不同。根据这些差别，高海拔的康定杨(3500 m)比来自低海拔的青杨(1500 m)增强UV-B有较强的耐性。 与水分充足情况下UV-B对植株的影响相比，干旱对杨树抗增强UV-B产生了一定的影响，表现为加剧或减弱UV-B对植物的影响，但这种影响与形态、生理指标有关。当干旱与增强UV-B共同作用时，杨树植株的株高、叶面积进一步降低、叶片进一步增厚。就脯氨酸的积累的而言，在没有水分胁迫时，增强UV-B促使它显著增加，而在干旱处理下这种效果变得不明显。干旱对增强UV-B的影响还与杨树的种类有一定的关系。在康定杨中，干旱减弱了增强UV-B对栅栏组织与海绵组织的影响，且在植株高度、叶面积上表现出累加效应，而在CAT上交互作用显著；但在青杨中干旱则加剧增强UV-B对栅栏组织与海绵组织的影响，在植株高度、叶面积及比叶面积上表现出显著的交互作用。据碳同素分析，在水分充足的条件下，无论是康定杨，还是青杨，增强UV-B均导致其长期用水效率的提高，然而当两种胁迫共同作用时，长期用水效率则表现出差异，在青杨中，长期用水效率得到进一步增高，而康定杨中干旱的效应被增强UV-B所减轻。 3. 田间试验表明，杨树的生长、生理特征都受到养分和增强UV-B的影响。施肥对杨树的影响表现为：提高了叶面积、生物量及SOD的活性，降低了抗坏血酸含量。对于施肥作用，两种杨树的反应也有区别：在康定杨中施肥显著增加了的叶片长度、宽度及光合色素的含量，降低了净光合速率、气孔导度及胞间CO2浓度；在青杨中，则SOD、GPX、APX活性表现增加。从试验看出，施肥对来自于高海拔地区的康定杨(3500 m)的影响较大，对来自低海拔的青杨(1500 m)影响较小，这与它们对原产地的生境适应有一定关系。在康定杨生长的高海拔地区，低温度和湿度不能为地上凋落物或土壤中的根分解提供理想的条件，造成当地土壤的低养分状况，所以当肥料施用以后，效果显著。 经过增强UV-B处理，杨树叶片中UV-B吸收物质含量、GPX的活性得到提高，而脯氨酸、丙二醛、可溶性蛋白质、叶绿素及类胡萝卜素含量没有受到影响。对于增强UV-B两种杨树受到的影响也有所不同：在青杨中增强UV-B导致叶面积缩小，生物量、净光合速率降低，APX的活性及长期用水效率的提高，而对康定杨的这些指标没有产生显著影响，相反抗氧化酶的活性明显高于青杨。这些差异性是由于两种杨树对原产地不同UV-B背景的长期适应结果。康定杨长期生长在较高UV-B环境中，对UV-B有较强的耐性。而青杨适应于较低的UV-B环境，对增强UV-B较为敏感。 试验中施肥也影响了植株对增强UV-B的反应，不过这种影响与杨树的种类及测定指标有一定的相关性。例如，在缺肥的情况下，青杨的长期用水效率和康定杨的叶绿素含量都受到增强UV-B的显著影响，而施肥以后这种影响变得不显著。在缺肥的条件下，GPX、APX在青杨中的活性、GPX在康定杨中的活性对增加UV-B反应不敏感；而施肥以后则变化显著，同样胞间CO2浓度在康定杨也有类似的变化。 For past decades, Ultraviolet radiation, especially UV-B reaching the Earth’s surface increased because of depletion of ozone layer resulted from emission of NxO and CFC’s from human activities. In this experiment, different species of Populus section Tacamahaca Spach from different UV-B background were selected as a model plant to assess the effects of enhanced UV-B radiation. Morphological and physiological traits induced by enhanced UV-B were observed and the different responses between P. kangdingensis and P. cathayana were discussed, furthermore the influences of drought and fertilizer on responses induced by enhanced UV-B were studied. Since poplars play an important role in lumber supply, and are important component of ecosystems due to their fast growth and wide adaptation, the study could provide a strong theoretical evidence and scientific direction for the afforestation, and rehabilitation of ecosystem. The results are as follows: 1. The experiment conducted in a greenhouse indicated that morphological and physiological traits of two poplars were affected by enhanced UV-B radiation. Enhanced UV-B radiation not only reduced biomass, leave area and internode length, but also increased leaf thickness and SOD activity as well as MDA concentration and electrolyte rate. However, no significant changes in leaf numbers, root shoot ratio, and total chlorophyll and chlorophyll component were observed. There were different responses to enhanced UV-B radiation between two species. Compared with P. kangdingensis, cuttings of P. cathayana, exhibited lower height increment and smaller leaf area. In addition, there were significant differences in free proline, soluble protein, and UV-B absorbing compounds, and the activity of SOD and GPX, long-term WUE between them. Differences in plant height, biomass, leaf area, free proline concentration, and long-termed WUE showed that P. cathayana were more affected by enhanced UV-B radiation than P. kangdingensis. In contrast, more increase of specific leaf mass, leaf thickness, and soluble sugar, and UV-B absorbing compounds, and activity of SOD and GPX were observed in P. kangdingensis. According to these results, we suggested that P. kangdingensis from high elevation, which adapted to higher UV-B environments, had more tolerance to enhanced UV-B than P. cathayana from low elevation, which adapted to lower UV-B environment. We believe it was the difference of leaf thickness, specific leaf mass, and UV-B absorbing compounds as well as the activity of SOD and GPX resulted in lower adaptation of P. cathayana to enhanced UV-B radiation. 2. Growth and physiological traits of two poplars were affected by both drought and enhanced UV-B radiation. Moreover, it was observed that when two stresses applied together drought could exacerbate UV-B effects or decrease sensitivity to UV-B. In the experiment, drought significantly decreased plant height, leaf numbers, leaf area, and increased leaf thickness, and ABA, and CAT activity of two poplars. There were significant interspecific differences to drought stress. Exposed to drought, soluble protein and proline concentration were increased in P. cathayana but not in P. kangdingensis. However, more changes in CAT and long-term WUE were observed in kangdingensis. Different change in long-term WUE suggests that two poplars adapted different water-use strategies. P. kangdingensis employ a conservative water-use strategy, whereas P. cathayana employ a prodigal water-use strategy. Based on the differences in leaf area, accumulation of free proline and ABA, CAT activity as well as long-term WUE, we believed that P. kangdingensis from high elevation had a greater tolerance to drought than P. cathayana from low elevation，which is the result of adaptation to local environment. In high elevation area, trees are prone to suffer from physiological drought because of un-movable water caused by frost. Besides lower temperature enable the plants had greater adaptability to frost as a results the requirement of water is reduced Enhanced UV-B radiation decreased shoots height, leaf area, and increased specific leaf mass and thickness of palisade and sponge layer as well as APX activity and UV-B absorbing compounds in both species. Whereas, leaf numbers, ABA content, soluble protein and CAT activity showed no differences to enhanced UV-B radiation. Interspecific differences were also observed. Compared with P. kangdingensis, P. cathayana showed lower shoot height and smaller leaf area, higher SOD activity. Besides, variation in UV-B absorbing compounds was found. These differences suggested that P. kangdingensis from high elevation (3500 m) was more tolerant to enhanced UV-B radiation than P. cathayana from low elevation (1500 m). Compared with morphological and physiological changes induced by enhanced UV-B radiation under well-watered conditions, drought exacerbated or decreased these changes. However, these effects vary with parameters measured. When two stresses applied together, shoot height and leaf area further decreased while leaf thickness further increased. Under well-watered conditions, enhanced UV-B radiation significantly increased proline content, but such effect was not observed under drought conditions. The effect of drought on enhanced UV-B radiation was related to species. For example, drought reduced the effects of enhanced UV-B radiation on palisade parenchyma and sponge mesophyll in P. kangdingensis, and additive effects in shoot height and leaf area and interactive effect CAT activity were observed. In contrast, for P. cathayana drought significantly exacerbated the effects of enhanced UV-B radiation on palisade parenchyma and sponge mesophyll; there were noticeable interaction in shoot height, leaf area and specific leaf mass. As far as long-term WUE is concerned, it was increased by enhanced UV-B radiation under well-watered conditions in both species. While different effect was observed between two species in combination of two stresses. Long-term water use efficiency was further increased in P. cathayana whereas the effect was less significant in P. kangdingensis. 3. The field experiment showed that growth and physiological traits of poplars were affected by nutrition and enhanced UV-B radiation. Fertilization significantly increased leaf area, biomass and SOD activity, reduced Ascorbic acid concentration. There was interspecific difference in response to fertilization. For P. kangdingensis, fertilization significantly increased leaf width, leaf length and photosynthetic pigments content while net photosynthetic rate and stomatal conductance, intercellular CO2 concentration were significantly decreased. However, for P. cathayana, these parameters were unaffected except the increase of SOD, GPX and APX activity. From above, it could concluded that P. kangdingensis from high elevation was more affected by fertilization than P. cathayana, This difference was due to adaptation to local environment., The low temperature and moisture where P. kangdingensis was collected can not provided optimum to decompose roots and litter fall as a result the nutrition in soil was poor. Exposed to enhanced UV-B radiation, for both species UV-B absorbing compounds and GPX activity were significantly increased while proline, MDA, soluble protein, chlorophyll, carotenoids were not affected. Different responses were also observed between the two species. Enhanced UV-B radiation caused significant decreases in leaf area, biomass, net photosynthetic rate and increase in APX activity and long-term WUE in P. cathayana but not in P. kangdingensis. In addition, activity in antioxidant enzymes was much higher in P. kangdingensis than in P. cathayana. In the experiment fertilization affected responses of cuttings to enhanced UV-B radiation, but it concern species and parameters measured. Long-term WUE in P. cathayana and chlorophyll in P. kangdingensis were significantly increased by enhanced UV-B radiation under non-fertilization treatments while the increase was not found under fertilization treatment. In contrast, under no fertilization treatment enhanced UV-B radiation did not affected GPX and APX activity in P. cathayana and GPX in P. kangdingensis while significant increase appeared after application of fertilization. Similar effect of enhanced UV-B radiation on intercellular CO2 concentration in P. kangdingensis was observed.

沙棘(Hippophae rhamnoides L.)在低温和增强UV-B胁迫下的生态生理反应

植物生长和生产力受到自然界各种形式的生物和非生物胁迫因子的影响。这些胁迫包括低温、高温、盐碱、干旱、洪水、重金属、虫害、病害和紫外线辐射等等。而人类活动大大加剧了这些胁迫所带来的影响。由于人类污染而导致臭氧层衰减以及由此产生的地球表面紫外辐射增强已经成为全球气候变化的一个主要方面。UV-B胁迫，甚至当前的辐射水平，所带来的影响已经引起科学工作者的广泛关注。 为了生存和繁殖，植物不得不面临环境中各种潜在胁迫所带来的负面影响。然而，植物生活型的不可移动性决定了其逃避胁迫的局限性。因此，绝大多数植物都是通过对胁迫作出反应，通过修复或者更新组织来降低伤害。而植物应对环境变化的能力则是由其生长模式的种属特异性和本身的遗传组成所决定。在自然界，植物常常同时面临多种胁迫，这些胁迫所引发的植物反应可能具有叠加、协同或者拮抗作用。沙棘是一种具刺、具有固氮功能的多年生雌雄异株灌木，广泛分布于亚欧大陆的温带地区和亚洲亚热带的高海拔地区。在中国，沙棘常常被用作植被恢复中的先锋树种而大量栽培。本文采用沙棘作为模式植物，试图探索木本植物对低温，UV-B辐射增强以及其与干旱的复合胁迫的响应以及沙棘对这些胁迫响应是否具有种群差异性。 对来自南北两个种群的沙棘进行短日照和低温处理，检测了其在抗寒锻炼和抗寒性发育过程中存在的性别差异。结果表明，短日照和低温都分别能够诱导抗寒锻炼的发生，而两者同时存在对所有实验植株抗寒性的大小具有叠加效应。然而，短日照和低温所诱导的抗寒性在两个种群中都具有性别差异性，雄性植株比雌雄植株对短日照和低温更为敏感。同时，南北种群间也存在差异性，北方种群的植物比南方种群的植物对短日照和低温敏感，从而在短日照下抗寒锻炼的发生时间更早，低温诱导的抗寒性更大。短日照和低温诱导植物增加抗寒性的同时伴随着脱落酸的变化。脱落酸的变化因处理，种群和性别的不同而不同。这些生理反应表明不同的沙棘种群，不同的植株性别对同一环境胁迫可能存在不同的生存策略。 比较了来自高低两个海拔的沙棘种群对于干旱和UV-B辐射增强以及两者复合胁迫条件下的生理生态反应。干旱使两个种群中植株总的生物量，总叶面积，比叶面积，叶片含碳量，含磷量，木质素含量和碳氮比显著降低，使根冠比，粗根细根比和叶片脱落酸含量显著增加。干旱而非UV-B使得δ13C 值显著增加。但是，比较而言，来自高海拔的种群对干旱反应更为强烈，而来自低海拔的种群对UV-B更敏感。在UV-B辐射增强的处理下，干旱所诱导的脱落酸的积累被显著抑制。而且我们检测到在一些指标上存在显著的干旱×UV-B交互作用，如两个种群中在总生物量上，低海拔种群中在总叶面积，粗根细根比上，高海拔种群中在比叶面积，δ13C值，木质素含量上都存在明显的交互作用。这些结果表明这两个种群对胁迫具有不同的适应性反应，来自高海拔的种群比来自低海拔的种群更能够抵御干旱和UV-B胁迫。 室外实验表明，UV-B 去除/增补对沙棘高低两个海拔种群的影响都不大。对生物量的积累，植株高度以及一些常见的胁迫反应生理指标比如丙二醛、ABA 和游离脯氨酸都没有显著影响。UV-B 的效应比UV-A 大，植物反应在无UV 和仅有UV-A 的处理间没有什么区别。然而，UV-B 去除的两个处理和UV-B 存在的两个处理间存在显著区别。UV-B 使得两个种群都显著降低了比叶面积(SLA)，但却使长期用水效率增加。但UV-B对光合色素和光合系统II 的影响不大。总体看来，来自低海拔的种群对UV-B 更为敏感。 Plant is adversely affected by various abiotic and biotic stress factors. These stressors includelow temperature, heat, salt, drought, flooding, heavy metal toxicity, wounding by herbivores,infecting by pathogenic microorganisms, ultraviolet (UV) radiation and so on. Variousanthropogenic activities have accentuated the existing stress factors. One of the mostimportant aspects of global change is that of stratospheric ozone depletion caused by seriousanthropogenic pollution and the resulting increase in UV radiation reaching the surface of theEarth. Scientists have become concerned about the effects that considerable UV-B stress, evenat current levels. In order to survive and reproduce, plants have to be able to cope with lots of potentiallyharmful stress factors that are almost constantly present in their environment. Most plants’responses under stress are to neutralize the stress, repairing the damage or regrowing newtissue rather than to avoid it due to their sessile life style. The plant defense capacity dependson plant-specific modular growth patterns and genetic make-up that allows for flexibleresponses to changing environments. Plants usually encounter several stresses simultaneouslyunder field conditions, and the stresses may cause a variety of plant responses, which can beadditive, synergistic or antagonistic. Sea buckthorn (Hippophae rhamnoides L.), a thorny nitrogen fixing deciduously perennialshrub, which is widely distributed throughout the temperate zones of Asia and Europe and thesubtropical zones of Asia at high altitudes. It has been widely used in forest restoration as thepioneer species in China. In this paper, we used sea buckthorn as a model, tried to get some understand of how plants fight low temperature, enhanced UV-B radiation level and thatcombination of drought. And also, want to know whether does there exist some populationspecific responses to such stressors. Sexual differences in cold acclimation and freezing tolerance development of two contrastingsea buckthorn (Hippophae rhamnoides L.) ecotypes from northern and southern regions inChina were recorded after exposure to short day photoperiod (SD) and low temperature (LT).The results demonstrated that cold acclimation could be triggered by exposing the plants toSD or LT alone, and that a combination of both treatments had an additive effect on freezingtolerance in all plants tested. However, development of freezing tolerance was dependent onthe sex of plants under SD and LT, the males were clearly more responsive to SD and LT thanthe females in both ecotypes studied. On the other hand, development of freezing tolerancewas also ecotype-dependent, the northern ecotype was more responsive to SD and LT than thesouthern ecotype, resulting in earlier cold acclimation under SD and higher freezing toleranceunder LT. Moreover, development of freezing tolerance induced by SD and LT wasaccompanied by changes in ABA levels. These alterations in ABA levels were different indifferent treatments, ecotypes and sexes. Therefore, the differences in SD and LT-inducedphysiological responses showed that the different ecotypes and the different sexes mightemploy different survival strategies under environmental stress. Two contrasting populations from the low and high altitudinal regions were employed toinvestigate the effects of drought, UV-B and their combination on sea buckthorn. Droughtsignificantly decreased total biomass, total leaf area, specific leaf area，leaf carbon (C),phophous (P), lignin content and the ratio of C: N in both populations, and increasedroot/shoot ratio, fine root/coarse root ratio and abscisic acid content (ABA), in bothpopulations. Drought but not UV-B resulted in significantly greater carbon isotopecomposition (δ13C) values in both populations. However, the high altitudinal population wasmore responsive to drought than the low altitudinal population. The drought-inducedenhancement of ABA in the high altitudinal population was significantly suppressed in thecombination of drought and elevated UV-B. Moreover, significant drought × UV-B interactionwas detected on total biomass in both populations, total leaf area and fine root/coarse root inthe low altitudinal population, specific leaf area, δ13C value and leaf lignin content in the high altitudinal population. These results demonstrated that there were different adaptive responsesbetween two contrasting populations, the high altitudinal population exhibited highertolerance to drought and UV-B than the low altitudinal population. A field experiment was conducted to investigate effects of UV-B exclusion/supplementationon two altitudinal populations of sea buckthorn. UV-B exclusion or supplementation had littleeffects on both populations investigated. For instance, the total biomass, plant height andsome physiological index such as Malondialdehyde (MDA), ABA and free proline were notchanged significantly. The UV-B effects are more significant than that of UV-A, nodifferences were found between treatments of excluded UV and excluded UV-B. However,compared with treatments of UV-B exclusion (including absent of UV-B and all UV band),the present of UV-B (including near ambient environment and enhanced UV-B) significantdecreased specific leaf area, and increased long time water use efficiency as evaluated by δ13Cvalue. UV-B had little effects on photosynthetic pigments and Photosystem II (PSII). The lowaltitude population is more sensitive to UV-B than that of the high altitude population.

模拟增温与UV-B 辐射增强对云杉种子萌发和幼苗生长的影响

臭氧层损耗导致的地球表面UV-B辐射增强以及温室气体增多引起的气候变暖是当今两大全球环境问题。UV-B辐射增强和气候变暖对陆地植物和生态系统产生深远影响，并已成为全球变化研究的重要议题。作为世界第三极的青藏高原，UV-B 辐射增强以及气候变暖现象尤为突出。本试验所在林区是青藏高原东缘的主要林区，具有大面积的亚高山人工针叶成熟林，在全球变化背景下该森林的天然更新潜力如何是急待回答的重要问题。基于此，本研究围绕森林树种的种子和幼苗这一更新的重要阶段，开展了气候变暖、UV-B辐射增强和联合胁迫对云杉种子萌发及幼苗定居影响的研究，旨在全球变化背景下，探讨全球变暖、UV-B 辐射增强和联合胁迫是否对西南地区大面积人工亚高山针叶林更新的种子萌发和幼苗定居阶段产生影响。 本文以青藏高原东缘亚高山针叶林主要树种云杉为研究对象，研究云杉种子萌发及幼苗的生长和生理对UV-B辐射增强与气候变暖的响应。采用UV-B荧光灯（UV-lamp）来模拟增强的UV-B 辐射，此外，采用开顶式有机玻璃罩（OTCs）来模拟气候变暖。本试验包括四个处理：（1）大气UV-B 辐射+大气温度（C）；（2）大气UV-B 辐射+模拟气候变暖（W）；（3）增强的UV-B辐射+大气温度（U）；（4）增强的UV-B辐射+模拟气候变暖（U+W）。 根据本试验结果，UV-B辐射增强对云杉种子萌发没有显著影响，它对萌发云杉幼苗的影响主要体现在幼叶展开以后。根据两年的试验结果，增强的UV-B辐射降低了云杉幼苗抗氧化酶活性，降低了抗氧化物质的含量，此外，造成了膜质的过氧化，表现为MDA在针叶中的积累。增强的UV-B照射处理萌发云杉幼苗两年后，幼苗的生长受到显著抑制。我们的结果显示，OTCs分别提高了空气（10 cm）和土壤（5 cm）温度1.74℃和0.94 ℃。增温显著地促进了云杉种子提前萌发，提高了萌发速率和萌发比率，而且，明显地促进了幼苗的生长，表现为株高和生物量累积的显著增长。此外增温还有利于云杉幼苗根的伸长生长以及生物量的累积，这可以使云杉幼苗更好地利用土壤中的水分和营养元素。 根据本试验结果，温度升高显著地促进了增强UV-B辐射下云杉萌发幼苗的生长，这说明，温度升高缓解了UV-B辐射增强对云杉萌发幼苗的负面影响。这种缓解作用可能是温度升高对UV-B辐射增强处理下幼苗的抗氧化系统活性改善的结果。温度升高还缓解了高UV-B辐射对云杉幼苗根生长的抑制作用，这也可能是增温缓解伤害的原因之一。此外，根据我们的试验结果，增温与UV-B辐射增强联合作用（U+W）下云杉萌发幼苗的生长状况好于大气温度与大气UV-B辐射联合（C）处理，表现为株高、地径、根长和生物量积累均高于C处理，因此可以推断，UV-B辐射增强与气候变暖同时存在对萌发幼苗在两年之内的生长没有产生抑制作用，也就是说，气候变暖的缓解作用完全弥补了UV-B辐射增强的有害作用。 同样，增强的UV-B辐射显著影响了云杉幼苗的光合作用，表现为净光合速率（Pn）和表观量子效率（Φ）的提高，此外，根据我们的试验结果，它还造成了PSII的光抑制。增强的UV-B辐射显著抑制了云杉幼苗对营养元素的吸收，表现为大量营养元素、碳、钙、镁和锌含量的降低，但是，它却显著促进了铁在植株体内的积累。增温显著地提高了净光合速率，但是，它对光系统II（PSII）的光化学效率影响不大。温度升高缓解了UV-B增强对云杉幼苗光合作用的伤害，表现为净光合速率、表观量子效率以及PSII光化学效率的提高。此外，温度升高还缓解了UV-B辐射增强对离子吸收的抑制作用。 Enhanced UV-B radiation due to the reduction of O3 layer and global warming induced by increased greenhouse gases in the air have become the two pressing aspects of global climate changes. Moreover, enhanced UV-B radiation and warming have profound and long-term impacts on terrestrial plants and ecosystems, and the studies focusing on the two factors have attracted many attentions. Qinghai-Tibetan Plateau is the third in elevation in the world, and enhanced UV-B radiation and climate warming are especially prominent in this region. Our research located in the main forest belt in the eastern Qinghai-Tibetan Plateau where large areas of subalpine coniferous forests distributed. Based on that, we carried out a research to study the effects of enhanced UV-B radiation and climate warming on seed germination and seedlings growth of seedlings which are the important basic stage in forest regeneration. This research was arranged by a complete factorial design and included two factors (UV-B radiation and temperature) with two levels. The UV-lamps were used to manipulate the supplemental UV-B radiation and open-top chambers (OTCs) were adopted to increase temperature. The four treatments were: (1) C, ambient UV-B without warming; (2) U, enhanced UV-B without warming; (3) W, ambient UV-B with OTCs warming; (4) U+W, enhanced UV-B with OTCs warming. The main results were exhibited as follows: 1. Based on our results in this research, OTCs increased temperature on average 1.74℃ in air (10 cm above ground) and 0.92 ℃ in soil (5 cm beneath ground). Furthermore, OTCs also slightly reduced soil moisture and relative air humidity, however, the differences was not statistically significant. 2. Our results showed that enhanced UV-B had no significant effects on the seeds germination of P. asperata. Enhanced UV-B affected sprouts of P. asperata until the needles unfolded. During two years, enhanced UV-B inhibited the efficiency of the antioxidant defense systems, and as a result, it induced oxidant stress and the accumulation of MDA in needles. After two years of exposure to enhanced UV-B, the growth of P. asperata sprouts was markedly restrained compared with those under ambient UV-B radiation and temperature (C). Warming significantly stimulated the germination speed and increased the germination rate of P. asperata seeds. In the next place, it prominently facilitated the growth of P. asperata sprouts, represented as improvements in stem elongation and biomass accumulation. Furthermore, warming also increased root growth of P. asperata sprouts, which could made sprouts more efficient to use water and nutrient elements in soil. In this research, warming alleviated the deleterious effects of enhanced UV-B on P. asperata sprouts. It markedly stimulated the growth of P. asperata sprouts exposed to enhanced UV-B. The ease effects of warming on the abilities of the antioxidant defense systems might account for its amending effects on growth. After two years of exposure to enhanced UV-B radiation and warming, the growth of P. asperata sprouts was better than those under ambient UV-B radiation without warming (C), which could be seen from the higher plant height, basal diameter, root length and total biomass accumulation compared with C. 3. Enhanced UV-B radiation significantly influenced the photosynthesis processes of two-year old P. asperata seedlings. Our results showed that enhanced UV-B reduced the net photosynthetic rate (Pn) and the apparent quantum efficiency (Φ), and induced photoinhibition of photosynthetic system II (PSII). Enhanced UV-B significantly decreased the concentration of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and zinc (Zn), however, it increased the accumulation of iron (Fe) in the whole plant of P. asperata seedlings. Warming significantly stimulated Pn of P. asperata seedlings but it had no prominent impacts on the photochemical efficiency of PSII. In our research, warming also alleviated the harmful effects of enhanced UV-B on photosynthesis and absorption of ions of P. asperata seedlings. It increased Pn, Φ and the photochemical efficiency of PSII in seedlings exposed to enhanced UV-B. Moreover, warming also increased the absorption of ions of the seedlings exposed to enhanced UV-B radiation.

增强UV-B辐射对粗枝云杉(Picea asperata Mast.)和青杨(Populus cathayana Rehd.)的影响

光是植物赖以生存的重要环境因子，但是植物在获得光的同时不可避免的会受到紫外辐射的伤害。尤其是近年来，人类向大气中排放的大量氮氧化合物和氟氯烃类化合物(CFC’s)引起臭氧分子的分解，导致到达地球表面的紫外辐射增加，特别是UV-B辐射增强。而另一方面，植物对UV-B辐射反应的敏感性在种间和品种间存在差异，主要受植物基因型，生态型和生活型的控制。本项目分别以粗枝云杉和青杨组杨树为模式植物，从形态和生理生化方面分别研究了来自不同水分背景下的粗枝云杉种群和来自不同UV-B背景下的青杨种群在增强UV-B下的反应及其反应差异,并探讨了干旱、喷施外源脱落酸(ABA)对它们抗UV-B能力的影响。研究成果可为生态系统的恢复与重建提供理论依据和科学指导。主要研究结果如下： 1. 粗枝云杉的两个种群，湿润种群(来自四川黑水)和干旱种群(来自甘肃迭部)在水分良好和干旱状况下表现出对增强UV-B的不同响应。同时，干旱对粗枝云杉抗UV-B能力的影响也得到研究：两种胁迫共同作用时，干旱表现出在一定程度上减弱了增强UV-B对粗枝云杉的生理特性的影响。 干旱胁迫显著降低了两个粗枝云杉种群的光合同化速率(A), 气孔导度(gs)和PSII的有效光量子产量(Y), 同时，提高了非光化学猝灭效率(qN)和超氧化物歧化酶(SOD)的活性。与湿润种群相比，干旱种群抗旱性更强，表现为干旱种群拥有更高的SOD和干旱进一步加剧了UV-B的胁迫效应。 本研究中，干旱胁迫单独作用时，显著降低了青杨两个种群的生物量积累和气体交换，具体包括A、gs、蒸腾速率(E)和光合氮利用效率(PNUE)，提高了两个种群的瞬时水分利用效率(WUEi)、长期水分利用效率(WUET)、碳同位素组分(δ13C)和氮含量(N)。同时，UV吸收物质和ABA含量也得到积累。另一方面，增强UV-B对青杨两个种群各个指标的影响，同干旱所引起的效应有着相似的趋势。同低海拔种群相比，高海拔种群有着更强的抗旱和抗UV-B能力，具体表现在高海拔种群有着更多的生物量积累，更强的气体交换和水分利用效率及更高水平的ABA和UV吸收物质含量。相比干旱诱导的生物量积累和气体交换的降低，在干旱和增强UV-B两个胁迫同时作用于青杨时，这种降低表现的更为明显。显著的干旱和UV-B的交互作用还表现在WUEi, WUET, δ13C, 可溶性蛋白含量, UV吸收物质含量, ABA, 叶片和茎中的N含量以及C/N比中。 3. 经过一个生长季的试验观察，增强UV-B、外源ABA及两因子共同作用对青杨的生物量积累、气体交换、内源ABA和UV吸收物质含量、抗氧化系统以及碳、氮含量和碳/氮比均产生显著影响。本试验中，青杨的两个种群分别来自中国西南部的不同海拔地区，高海拔种群来自青海大通而低海拔种群来自四川九寨。外源ABA的胁迫为直接喷施ABA到青杨叶片，而增强UV-B胁迫是利用平方波系统分别保证青杨苗暴露于外界UV-B强度和两倍于外界UV-B强度下。 研究结果显示，增强UV-B显著的降低了两个青杨种群的株高、基茎、总叶面积和总生物量等生长指标，同时也导致其A、gs、E和叶片中碳含量的减少。而显著增加了SOD和过氧化物酶(GPx)活性水平，诱导了过氧化氢(H2O2)和MDA的显著增加，促进了UV吸收物质和不同器官中内源ABA含量的显著积累。另一方面，外源ABA引起了青杨光合同化速率的下降，SOD和GPx酶活性的增强，H2O2 和 MDA含量也表现出显著增加，同时，内源ABA含量得到显著累积。同低海拔种群相比，高海拔种群具有更加抗UV-B和外源ABA的特性。显著的UV-B和ABA的交互作用表现在A, E, SOD和GPx活性，以及叶片和根部的内源ABA等一系列指标中。在所有胁迫下，叶片中的碳和氮含量同其在茎和根中的含量显著相关，另外，叶片和茎中的氮含量同茎中的碳含量显著相关。 Sunlight is an indispensable environment factor for plants survival and development. Meanwhile, photosynthetic organisms need sunlight and are thus, inevitably, exposed to UV radiation. Especially for recent years, ultraviolet radiation, especially UV-B reaching the Earth’s surface increased because of depletion of ozone layer resulted from emission of NxO and CFC’s from human activities. On the other hand, the sensitivity of plants to UV-B radiation depends on the species, developmental stage and experimental conditions. In this experiment, two populations of Picea asperata Mast from different water background and two populations of Populus cathayana Rehder from different altitude background were selected as model plants to assess the effects of enhanced UV-B radiation. Morphological and physiological traits induced by enhanced UV-B in each plant species were observed and the different responses were discussed, furthermore the influences of drought and exogenous ABA on responses induced by enhanced UV-B were studied. The study could provide a strong theoretical evidence and scientific direction for the afforestation and rehabilitation of ecosystem. The results are as follows: 1. Different responses of two contrasting Picea asperata Mast. populations to enhanced ultraviolet-B (UV-B) radiation under well-watered and drought conditions were investigated. And the effects of enhanced UV-B on tolerance of drought were also observed in our study that the UV-B exposure may have alleviated some of the damage induced by drought. Two contrasting populations, originating from a wet and dry climate region in China, respectively, were employed in our study. Drought significantly decreased CO2 assimilation rate (A), stomatal conductance (gs) and effective PSII quantum yield (Y), while it significantly increased non-photochemical quenching (qN) and the activity of superoxide dismutase (SOD) in both populations. Compared with the wet climate population, the dry climate population was more acclimated to drought stress and showed much higher activities of SOD and ascorbate peroxidase (APX), and much lower levels of malondialdehyde (MDA) and electrolyte leakage. On the other hand, enhanced UV-B radiation also induced a significant decrease in the chlorophyll (Chl) content in both populations under well-watered conditions, and a significant increase in UV-absorbing compounds in the wet climate population. After one growing season of exposure to different UV-B levels and watering regimes, the increases in MDA and electrolyte leakage, as induced by drought, were less pronounced under the combination of UV-B and drought. In addition, an additive effect of drought and UV-B on A and gs was observed in the wet climate population, and on the activity of APX and qN in the dry climate population. 2. The significant effects of drought, enhanced UV-B radiation and their combination on Populus cathayana Rehd. growth and physiological traits were investigated in two populations, originating from high and low altitudes in south-west China. Our results showed that UV-B acts as an important signal allowing P. cathayana seedlings to respond to drought and that the combination of drought and UV-B may cause synergistically detrimental effects on plant growth in both populations. In both populations, drought significantly decreased biomass accumulation and gas exchange parameters, including A, gs, E and photosynthetic nitrogen use efficiency (PNUE). However, instantaneous water use efficiency (WUEi), transpiration efficiency (WUET), carbon isotope composition (δ13C) and nitrogen (N) content, as well as the accumulation of soluble protein, UV-absorbing compounds and abscisic acid (ABA) were significantly increased by drought. On the other hand, cuttings from both populations, when kept under enhanced UV-B radiation conditions, showed very similar changes in all above-mentioned parameters, as induced by drought. Compared with the low altitude population, the high altitude population was more tolerant to drought and enhanced UV-B, as indicated by the higher level of biomass accumulation, gas exchange, water-use efficiency, ABA concentration and UV-absorbing compounds. After one growing season of exposure to different UV-B levels and watering regimes, the decrease in biomass accumulation and gas exchange, induced by drought, was more pronounced under the combination of UV-B and drought. Significant interactions between drought and UV-B were observed in WUEi, WUET, δ13C, soluble protein, UV-absorbing compounds, ABA and in the leaf and stem N, as well as in the leaf and stem C/N ratio. 3. During one growing season, significant effects induced by enhanced UV-B radiation, exogenous ABA and their combination on biomass accumulation, gas exchange, endogenous ABA and UV-absorbing compounds concentrations, antioxidant system as well as carbon (C) content, nitrogen (N) content and C/N ratio were investigated in two contrasting Populus cathayana populations, originating from high and low altitudes in south-west China. Exogenous ABA was sprayed to the leaves and enhanced UV-B treatment was using a square-wave system to make the seedlings under ambient (1×) or twice ambient (2×) doses of biologically effective UV-B radiation (UV-BBE). Enhanced UV-B radiation significantly decreased height, basal diameter, total leaf area, total biomass, A, gs, E and carbon (C) content in leaves, and significantly increased activities of SOD and guaiacol peroxidase (GPx), hydrogen peroxide (H2O2) and malonaldehyde (MDA) content as well as the accumulation of UV-absorbing compounds and endogenous ABA concentrations among different organs in both populations. In contrast, exogenous ABA showed significant decrease in A and significant increases in activities of SOD and GPx, H2O2, MDA content and the endogenous ABA concentrations. Compared with the low altitude population, the high altitude population was more tolerant to enhanced UV-B and exogenous ABA. Significant interactions between UV-B and ABA were observed in A, E, activities of SOD and GPx, as well as in endogenous ABA in leaves and roots of both populations. Across all treatments, C and N content in leaves was strongly correlated with those were in stems and roots, respectively. Additionally, leaf and stem N content were significant correlated with stem C content.