He-Ne激光对增强UV-B辐射后小麦幼苗光合作用的影响

以"晋麦8号"小麦幼苗为研究材料,分别采用He-Ne激光(辐照剂量为5 mW·mm-2)、增强UV-B(辐射剂量为10.08 kJ·m-2·d-1)以及二者的复合辐照进行处理.循坏处理不同天数(4、5、6、7、8 d)后,利用电导仪、低温荧光测定法检测了小麦叶绿体电子传递速率、膜透性和荧光发射光谱的变化;采用紫外分光光...     

肋果沙棘幼苗抗氧化酶系统及总黄酮对UV-B辐射增强的响应

该文以青藏高原特有木本植物肋果沙棘为材料,在62μW·cm-2的UV-B辐射强度下,分别测定处理了0～6 d幼苗叶片的氧化损伤程度、抗氧化系统酶活性和总黄酮含量及其抗氧化活性,以探究肋果沙棘对UV-B辐射的生理生态响应机制。结果表明:随UV-B辐射时间的增加,肋果沙棘幼苗过氧化氢含量(H2O2)和膜脂过氧化产物(MDA)显著增加;抗氧化系统酶中过氧化氢酶(CAT)活性显著升高;过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)活性呈先降后升的趋势,且活性均显著低于对照,超氧化物歧化酶(SOD)活性无明显变化;总黄酮含量随辐射时间的积累显著增加,作为非酶抗氧化物质的总黄酮对1,1-二苯基-2-苦基肼(DPPH)的清除率与其含量变化具有显著正相关关系。综上结果表明,肋果沙棘幼苗在抵御该辐射产生的氧化损伤中,通过提高CAT活性及增加总黄酮含量来抵御辐射造成的氧化损伤。     

Increased antioxidant activity in Cassia seedlings under UV-B radiation

Cassia auriculata L. seedlings were irradiated with ultraviolet B (UV-B) in an environment-control chamber. The two doses assayed (7.5 and 15.0 kJ m⁻²) induced oxidative damage with an increase in lipid peroxidation and hydrogen peroxide and a decrease in chlorophyll and total phenol contents. The ascorbate and dehydroascorbate content as well as the reduced glutathione/oxidized glutathione content and ratio were significantly increased. The UV-B stress led to significant increases of the activity of superoxide dismutase, catalase, peroxidase and polyphenol oxidase. It is suggested that Cassia seedlings try to counteract high concentrations of oxygen species produced under UV-B stress through a co-ordinated increase in the contents and activities of antioxidants involved in their detoxification.     

Response of barley seedlings to UV-B radiation as affected by NaCl

The response of barley seedlings, subjected to 150 mmol/L NaCl for 4 days at different light regimes (4 d in the light, 4 d in darkness and a 12 h light/dark cycle) before UV-B radiation was investigated. NaCl treatment resulted in a decrease of total chlorophyll content and an increase in H2O2, free proline and lipid peroxidation, as quantified by measurement of malondialdehyde. Significantly more proline was accumulated in the light than in darkness. The combination of UV-B and NaCl treatment produced an additive effect on most of the parameters studied. UV-B radiation reduced the chlorophyll/carotenoids ratio and photochemical efficiency of PSII as estimated by chlorophyll fluorescence. NaCl pre-exposure decreased H2O2 generation and lipid peroxidation and alleviated the inhibitory effect of UV-B on PSII activity. Proline accumulated under salt stress conditions might be one of the reasons for the observed tolerance of barley seedlings to UV-B radiation.     

Changes in photosynthesis, antioxidant enzymes and lipid peroxidation in soybean seedlings exposed to UV-B radiation and/or Cd

Aims

With a high growth rate and biomass production, bamboos are frequently used for industrial applications and recently have proven to be useful for wastewater treatment. Bamboos are considered as Si accumulators and there is increasing evidence that silicon may alleviate abiotic stresses such as metal toxicity. The aim of this study was to investigate the extent of metal concentrations and possible correlations with Si concentrations in plants.

Methods

This study presents, for the first time, reference values for silicon (Si), copper (Cu) and zinc (Zn) concentrations in stems and leaves of various bamboo species grown under the natural pedo-climatic conditions of the island of Réunion (Indian Ocean).

Results

A broad range of silicon concentrations, from 0 (inferior to detection limit) to 183 mg g^?1 dry matter (DM), were found in stems and leaves. Mean leaf Cu and Zn concentrations were low, i.e. 5.1 mg kg^?1 DM and 15.7 mg kg^?1 DM, respectively. Silicon, Cu and Zn concentrations increased over the following gradient: stem base?<?stem tip?<?leaves. Significant differences in Si, Cu and Zn contents (except Zn in the stem) were noted between bamboo species, particularly between monopodial and sympodial bamboo species, which differ in their rhizome morphology. Sympodial bamboos accumulated more Si and Cu than monopodial bamboos, in both stems and leaves, whereas sympodial bamboos accumulated less Zn in leaves than monopodial bamboos.

Conclusions

The findings of this study suggest that a genotypic character may be responsible for Si, Cu and Zn accumulation in bamboo.     

植物酶系统对UV-B辐射的响应机制

紫外辐射作为一种自然界存在的环境因子,影响着植物的生长发育。在植物从太阳辐射中获得光照和热量的同时,不可避免地要受到UV-B辐射的胁迫。植物在长期对环境的适应中,在体内形成了防御系统,以保护自身的安全,酶系统是其中之一。植物酶系统在实施防护的同时也受到了UV-B辐射的影响,信号分子对调节酶响应UV-B胁迫起了关键作用。本文重点论述了UV-B辐射增强下,植物酶系统的变化、植物酶系统的响应机制以及酶系统与信号物质的关系,并对该领域未来的研究方向提出了展望。     

Characterization of Transcriptome Expression: The Response of Isatis indigotica to Salt Stress

Russian Journal of Plant Physiology - Isatis indigotica Fort. is extremely widely planted and used for the source of the traditional Chinese medicine Radix Isatidis (Ban-Lan-Gen), which had...     

Photosynthetic Physiological Response of Radix Isatidis (Isatis indigotica Fort.) Seedlings to Nicosulfuron

Radix Isatidis (Isatis indigotica Fort.) is one of the most important traditional Chinese medicine plants. However, there is no suitable herbicide used for weed control in Radix Isatidis field during postemergence stage. To explore the safety of sulfonylurea herbicide nicosulfuron on Radix Isatidis (Isatis indigotica Fort.) seedlings and the photosynthetic physiological response of the plant to the herbicide, biological mass, leaf area, photosynthetic pigment content, photosynthetic rate, chlorophyll fluorescence characteristics, and P₇₀₀ parameters of Radix Isatidis seedlings were analyzed 10 d after nicosulfuron treatment at 5th leaf stage in this greenhouse research. The results showed that biological mass, total chlorophyll, chlorophyll a, and carotenoids content, photosynthetic rate, stomatal conductance, PS II maximum quantum yield, PS II effective quantum yield, PS II electron transport rate, photochemical quenching, maximal P₇₀₀ change, photochemical quantum yield of PS I, and PS I electron transport rate decreased with increasing herbicide concentrations, whereas initial fluorescence, quantum yield of non-regulated energy dissipation in PS II and quantum yield of non-photochemical energy dissipation due to acceptor side limitation in PS I increased. It suggests that nicosulfuron ≥1 mg L−1 causes the damage of chloroplast, PS II and PS I structure. Electron transport limitations in PS I receptor side, and blocked dark reaction process may be the main cause of the significantly inhibited growth and decreased photosynthetic rate of Radix Isatidis seedlings.     

黄瓜幼苗非结构性碳水化合物代谢对干旱胁迫与CO2倍增的响应

以‘津优1号’黄瓜水培幼苗为试材,采用裂区设计,主区设大气CO₂浓度(约380 μmol·mol^-1)和倍增CO₂浓度(760±20 μmol·mol^-1)2个CO₂浓度处理,裂区设无干旱胁迫、中度干旱胁迫和重度干旱胁迫3个水分处理(以PEG 6000模拟根际干旱胁迫),研究了黄瓜幼苗非结构性碳水化合物代谢对干旱胁迫和CO₂倍增的响应.结果表明: CO₂倍增促进了黄瓜叶片中非结构性碳水化合物(葡萄糖、果糖、蔗糖、水苏糖)的积累,降低了渗透势,提高了黄瓜的耐旱性.在干旱胁迫处理过程中,叶片中蔗糖合成酶、可溶性酸性转化酶和碱性转化酶活性先上升后下降;根中可溶性酸性转化酶和碱性转化酶活性则逐渐上升,蔗糖磷酸合成酶活性先上升后下降.CO₂倍增提高了蔗糖合成酶的活性而降低了蔗糖磷酸合成酶的活性,这两种酶和转化酶相互配合,促进了蔗糖的分解和抑制蔗糖合成,导致己糖积累,从而降低了细胞的渗透势,增强吸水能力.因此,CO₂倍增能缓解干旱胁迫造成的不利影响,提高黄瓜的耐旱性,并且这种缓解效应在干旱胁迫严重时表现更为明显.
     

Impact of silicon on maize seedlings exposed to short-term UV-B irradiation

Enhanced UV-B irradiation is one of the most important abiotic stresses that can influence various aspects of plant morphology, biochemistry and physiology. Silicon as a beneficial element can increase the plant’s tolerance against different abiotic stresses, including UV-B stress. In this work, the effect of silicon supplementation on the sensitivity of young maize (Zea mays L.) seedlings exposed to short-term UV-B radiation was studied. The seedlings were grown with 0 or 5 mM silicon in cultivation medium and on the fifth day of cultivation, they were exposed for 15 and 30 min to UV-B (302 nm) radiation. No significant changes in growth and content of assimilation pigments and the chlorophyll a/b ratio were observed in any of tested irradiation periods in control or Si-treated plants. Under UV-B stress, the content of ROS (hydrogen peroxide and superoxide radical) and TBARS increased in control plants. The oxidative status of Si-treated plants was only slightly affected even after 30 min. Phenolic metabolites (total phenols and flavonoids), important for their screening function under radiation stress, slightly increased after UV-B exposure in control plants, however, only flavonoids increased after 30 min in Si-treated plants. The measured parameters indicated that to some extent silicon supplementation contributes to higher UV-B tolerance of maize seedlings.     

UV-B辐射胁迫下杨梅幼苗的高光谱响应

设置UV-B滤光减弱、UV-B辐射增强和自然光(对照)3组模拟大田试验,比较了不同UV-B辐射处理下,亚热带典型木本植物杨梅幼苗的叶绿素含量、光谱反射率及光谱特征参数,研究UV-B辐射变化对亚热带森林树种的影响.结果表明:增强UV-B辐射可降低杨梅幼苗的叶绿素含量,而降低辐射则会显著促进叶绿素的增加,并且这种胁迫反应于光谱反射率中.3种不同梯度UV-B辐射作用下,可见光部分光谱反射率间的差异主要集中在绿光反射峰及红边附近,同时红边所在波长位置“红移”.UV-B辐射对杨梅的胁迫在时间上具有积累性.用反高斯模型参数R0、λ0、λp、Rs、6指示杨梅受UV-B胁迫,以Rs最显著.不同UV-B辐射水平下植物叶片光谱反射率上的差异,可通过较窄波段光谱反射率或特定波长光谱反射率所构建的植被指数加以有效区分.     

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.     

Cascade transduction and production of the light-nitric oxide signal from shoots to roots in maize seedlings exposed to enhanced UV-B radiation

The biomasses, rate of apparent nitric oxide (NO)-release, nitric oxide synthase (NOS) activity as well as β-d-endo and exo-glucanase activity of the cell wall were analyzed and determined in the roots of maize seedlings. It was found that rhizospheric treatments of 2-phenyl-4,4,5,5-tetramethlimida-zoline-l-oxyl-3-oxide (PTIO), a NO scavenger, and radiation of enhanced ultraviolet-B (UV-B) to aerial parts of the seedling markedly inhibited the rate of NO release in roots, raised the activity of β-d-endo and exo-glucanase, and increased the biomasses of roots. The patent inhibitor, N-nitro-l-arginine (LNNA), of NOS was unable to inhibit NOS activity and NO generation. Inversely, reactive oxygen species (ROS) eliminator, N-acetyl-cysteine (NAC), stimulated the rate of NO release. There is no relationship between NOS activity and the rate of NO release. The latter showed a positive correlation with nitrate reductase (NR) activity, whereas it showed a negative correlation with the bio-masses and the activity of β-d-endo and exo-glucanase. All results implicated that NO was a by-product generated by NR catalysis, whereas NR activity was sensitively repressed by the systemic signal network (involved in ROS) induced by enhanced UV-B. It indicated that the downstream signal molecule of enhanced UV-B light is probably ROS which decreased NO generation through inhibiting NR activity. The endogenous NO generated by NR catalysis is perhaps such a messenger for restraining β-d-endo and exo-glucanase activity that the root growth was retarded.     

Protective effect of zinc supplementation on blood antioxidant defense system in rats exposed to cadmium

The aim of this study was to assess the effects of subchronic exposure to cadmium (Cd) on the antioxidant defense system of red blood cells (RBCs) and lipid peroxide concentration in the plasma, as well as the possible protective role of zinc (Zn). For this purpose, 60 male Wistar rats (8 weeks old) were divided into three groups: the first group was exposed to Cd in the form of CdCl₂, administered in five doses (each of 0.4 mg Cd/kg BW) on days 5, 10, 15, 20 and 25, giving a total dose of 2 mg Cd/kg BW, i.p.; the second group was simultaneously exposed to Zn and Cd with the same timeline and the same doses of Cd as the first group but with, in addition, injections of Zn in the form of ZnCl₂, administered in doses of 0.8 mg Zn/kg BW, giving a total dose of 4 mg Zn/kg BW, i.p.; a control group received 0.5 mL of physiological saline in an identical manner.

It was shown that exposure to Cd induced a significant decrease (p<0.05) in superoxide dismutase (Zn/Cu SOD) and catalase (CAT) activities in RBCs. Increased lipid peroxide concentration, measured by thiobarbituric acid reactive substances (TBARS), was also observed in the plasma of cadmium-exposed rats. Cd had no effect on glutathione peroxidase (GSH-Px) activity. Zn administration had a beneficial effect on the Cd-induced decrease in Zn/Cu SOD activity (p<0.05) but not on CAT activity. Animals receiving Cd and Zn simultaneously had significantly (p<0.05) lower concentrations of lipid peroxides than rats exposed to Cd alone. Our results indicate that Cd causes oxidative stress and that Zn supply in conditions of exposure to Cd can partially protect against Cd-induced oxidative stress.     

Effects of exogenous spermidine on antioxidant system of tomato seedlings exposed to high temperature stress

The effects of foliar spraying with spermidine (Spd) on antioxidant system in tomato (Lycopersicon esculentum Mill.) seedlings were investigated under high temperature stress. The high temperature stress significantly inhibited plant growth and reduced chlorophyll (Chl) content. Application of exogenous 1 mM Spd alleviated the inhibition of growth induced by the high temperature stress. Malondialdehyde (MDA), hydrogen peroxide (H₂O₂) content and superoxide anion (O₂) generation rate were significantly increased by the high temperature stress, but Spd significantly reduced the accumulation of reactive oxygen species (ROS) and MDA content under the stress. The high temperature stress significantly decreased glutathione (GSH) content and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), but increased contents of dehydroascorbic acid (DHA), ascorbic acid (AsA), and oxidized glutathione (GSSG) in tomato leaves. However, Spd significantly increased the activities of antioxidant enzymes, levels of antioxidants and endogenous polyamines in tomato leaves under the high temperature stress. In addition, to varying degrees, Spd regulated expression of MnSOD, POD, APX2, APX6, GR, MDHAR, DHAR1, and DHAR2 genes in tomato leaves exposed to the high temperature stress. These results suggest that Spd could change endogenous polyamine levels and alleviate the damage by oxidative stress enhancing the non-enzymatic and enzymatic antioxidant system and the related gene expression.     

Response of growth and antioxidant enzymes in Azolla plants (Azolla pinnata and Azolla filiculoides) exposed to UV-B

Effect of ultravilolet-B (0.4 Wm(-2)) irradiation on growth, flavonoid content, lipid peroxidation, proline accumulation and activities of superoxide dismutase and peroxidase was comparatively analysed in Azolla pinnata and Azolla filiculoides. Growth measured as increment in dry weight reduced considerably due to all UV-B treatments. However, the reduction was found to be severe in A. filiculoides as compared to A. pinnata. The level of UV-absorbing compound flavonoids increased significantly in A. pinnata plants whereas only a slight increase in the flavonoid content was observed in A. filiculoides. UV-B exposure led to enhanced production of malondialdehyde (MDA) and electrolyte leakage in A. filiculoides than A. pinnata. Proline accumulation also showed a similar trend. Marked differences in the activity of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD) was noticed in both the plants exposed to UV-B. Our comparative studies indicate A. pinnata to be better tolerant to UV-B as compared with A. filiculoides which appears to be sensitive.     

Protective role of selenium in wheat seedlings subjected to enhanced UV-B radiation

Selenium (Se) is beneficial for some plants and is able to increase resistance and antioxidant capacity of plants subjected to stressful environment. In this work, the effects of enhanced ultraviolet-B (UV-B) radiation, Se supply, and their combination on growth and physiological traits of wheat (Triticum aestivum L., cv. Han NO.7086) seedlings were studied. The objective was to elucidate whether Se could alleviate the expected adverse effects of UV-B stress on seedlings. UV-B treatment caused a marked decline in growth parameters and total chlorophyll content and changed biomass allocation between aboveground and underground parts, which led to an increase in the root/shoot ratio. UV-B treatment also increased MDA content and the rate of superoxide radical (O₂^·−) production, although it increased some antioxidant (proline, phenolic compounds, and flavonoids) content and activity of antioxidant enzymes (peroxidase, superoxide dimutase, catalase (CAT)). Se treatment only increased total chlorophyll content and CAT activity. Compared with UV-B treatment alone, the combined treatment with UV-B and Se induced a significant increase in the biomass, total chlorophyll content, antioxidant content, and activity of antioxidant enzymes, and an evident decrease in MDA content and the rate of O₂^·− production. The results of this study demonstrated that Se alleviated the damage caused by UV-B to wheat seedlings to some extent by increasing antioxidant enzyme activity and antioxidant content.     

Carbon and nitrogen metabolism in barley plants exposed to UV-B radiation

The effect of UV-B radiation on FW, leaf and stem length, photosynthetic O₂ evolution, levels of carbohydrates and nitrates, and extractable activities of some of the enzymes involved in C and N metabolism was evaluated in barley ( Hordeum vulgare L. cv. Express) seedlings during the 9 days following transfer to an UV-B enriched environment. The results show that under our experimental conditions UV-B radiation scarcely affects the photosynthetic competence of barley leaves, expressed as RuBP carboxylase (EC 4.1.1.39) activity, O₂ evolution rate and chlorophyll content. Nevertheless, this treatment induced significant alterations of the enzyme activity of nitrate reductase (EC 1.6.6.1) and glutamine synthetase (EC 6.3.1.2), although only after a few days of treatment. The effects were not confined to the exposed tissue, but were detectable also at the root level. In fact, nitrate reductase decreased in response to UV-B in both leaf and root tissue, whereas glutamine synthetase was affected only in the root. In contrast, nitrate content was not influenced by the treatment, neither in root nor in leaf tissue, whilst leaf sucrose diminished in exposed plants only on the last day of treatment.     

A morphological and cytological study of Petunia hybrida exposed to UV-B radiation

The aim of this study was to investigate whether the cytoskeleton, and in particular the microtubular system, is affected by enhanced levels of ultraviolet-B (280–320 nm, 9 kJ m⁻² day⁻¹ biologically effective UV-B radiation) radiation in epidermal cells of Petunia x hybrida Vilm, isolated from leaves of plants grown under UV-B radiation and visible light. In addition, morphological changes during development were monitored. In a previous study microtubules were depolymerized and delays in the different stages of the cell cycle were found when protoplasts of Petunia were irradiated with UV-B radiation (Staxén et al. 1993. Protoplasma 173: 70–76). Thus it was of interest to ascertain whether the cytoskeleton would be similarly affected in an intact system. Assuming an effect of UV-B radiation on the microtubular system, we wished to determine whether this could be correlated to concomitant changes in leaf morphology. Plants of Petunia hybrida were grown in greenhouse conditions in the presence or absence of UV-B radiation. During the course of the experiment, samples were taken from young, expanding leaves and from older, fully expanded leaves and prepared for localization and analysis of microtubules from the adaxial epidermal cells. Morphology rather than the cytoskeleton was affected by UV radiation, despite the fact that the epidermal cytoskeleton would most likely be affected, since it is located in the cells which form the first intercepting layer for incident radiation.
Morphological changes under UV-B radiation, as compared to those under control conditions, were reflected in earlier flowering and an increase in leaf number. Cell division was thus stimulated as was also evidenced from the increased leaf area. Our results indicate that the number of stomata differentiated on a leaf area basis was not altered although the number of stomata per epidermal cell was reduced.