增强UV-B辐照对小麦幼苗叶肉细胞内Ca2＋水平的研究

以小麦（Triticum aestivum）幼苗叶片为材料,利用提取原生质体方法在小麦幼苗叶肉细胞中成功地装载了钙离子荧光指示剂fluo-3/AM,采用激光共聚焦显微技术检测了增强UV-B辐射后小麦幼苗叶肉细胞内游离钙离子荧光强度的分布,并对[Ca2＋];进行了测定.结果显示,对照组细胞内钙离子荧光分布较均匀,主要分布于紧贴质膜处和核周围,UV-B辐射组钙离子荧光与对照组分布相似,但其原生质体表面不如对照组平滑;同时发现增强UV-B辐射组细胞内钙离子荧光强度值较对照组高,说明增强UV-B辐射组小麦幼苗叶肉细胞维持较高浓度的钙离子水平.这些变化表明Ca2＋信号有可能以一定的方式参与了小麦响应UV-B辐射胁迫的过程.     

Phenological stages of willow (Salix)

The practice of uniform recording of biological plant growth stages or events has long been practiced in agricultural production. In this study the BBCH (Biologishe Bundesanstalt, Bundessortenamt and CHemical Industry) code has been applied to four precocious species of willows to define growth stages important to this group. The studied taxa represent varieties of potential importance in the Floral Industry. A new BBCH code is proposed where the annual cycle of willows is divided into clearly recognisable and easily distinguishable developmental phases which include eight principal stages, 30 secondary stages and six mesostages. Photographs illustrate the physical appearance of select stages. This proposed BBCH code shows a unified approach which may be applied to a large number of Salix species.     

Systemic Induction of Salicylates in Salix myrsinifolia(Salisb.)

We studied the induction of salicylates in mature leaves ofSalix myrsinifolia Salisb. (Salicaceae) following severe woundingby a specialist leaf-beetle Phratora vitellinae L. (Chrysomelidae).Levels of individual salicylates and aromatic amino acids andtheir total levels were determined in leaves at different developmentalstages. Induction of salicylates depended on: (1) the individualcompound; (2) the developmental stage of the plant organ; and(3) the genotype of the plant. Induction of salicylates wassystemic: levels of salicylates rose in unwounded young immatureand mature leaves, but no local response was detected in woundedleaves. In addition, there were clear clonal variations in boththe constant and induced levels of salicylates: clones withthe highest levels of salicylates were also most capable ofincreasing this level in response to herbivore attack i.e. notrade-off between constant and induced levels was detected.Furthermore, the levels of three aromatic amino acids, Phe,Tyr and Trp, increased in immature leaves of herbivore-affectedplants, which may indicate induction of enzymes of the shikimatepathway by wounding. The increase in salicylates was suggestedto be a consequence of an increased rate of synthesis ratherthan that of translocation. The induced levels of salicylatesdid not affect the subsequent feeding of highly specializedP. vitellinae. However, the ability to increase levels of salicylatesmay reduce grazing by generalist herbivores which are not ableto tolerate high levels of salicylates. Copyright 2001 Annalsof Botany Company Salix myrsinifolia, dark-leaved willow, Phratora vitellinae, salicylates, phenolic glycosides, herbivory, induced defence     

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。     

He-Ne激光对增强UV-B辐射小麦细胞膜的影响

采用He-Ne激光 5mW·mm-2 辐照方法,对增强UV-B 10.08kJ·m-2·d-1 辐射小麦细胞膜损伤进行修复的研究.结果表明:经He-Ne激光和UV-B复合处理后,小麦细胞膜表面电荷的电泳速度高于UV-B处理组,小麦的MDA含量比单独UV-B辐射后的低,SOD酶的活性增强.说明He-Ne激光和增强UV-B辐射复合处理后可使小麦的氧化酶活性增强,从而使MDA的浓度降低,小麦细胞膜损伤得到了一定程度的修复.     

Toxicity of 2,3,5,6-tetrachlorophenol to willow trees (Salix viminalis)

Chlorinated phenols have been intensively investigated from an eco-toxicological point of view, however almost nothing is known about toxicity of tetrachlorophenol (TeCP) to higher terrestrial plants. This article applied the willow tree acute toxicity test to study the toxicity of 2,3,5,6-TeCP to willows Salix viminalis (S. viminalis) at neutral and acidic conditions (roughly pH 7 and 4) with inhibition of transpiration as toxic endpoint. At neutral pH the EC₅₀ was >10 mg L^?1 while the EC₅₀ at acidic conditions was 0.32 ± 0.17 mg L^?1, clearly indicating that toxicity is exerted by the non-ionic chemical fraction. Standard tests running at neutral pH are therefore not capturing the full toxicity of weak acids and bases.     

Heat shock proteins in willow (Salix viminalis)

The heat shock response in three vegetatively propagated clones of Salix viminalis L. was studied. In the clone 78198, synthesis of a total of 58 proteins was induced or increased by heat shock. Of these proteins, 39 were found in both leaves and callus, 8 only in leaves, and 11 only in callus. The number of heat shock proteins differed between the three clones studied. The molecular weights of the heat shock proteins ranged from 18000 to over 94000. The optimal synthesis of heat shock proteins took place at 37–40°C, but several proteins could be induced at 25–30°C. The synthesis of the majority of the proteins present at a normal growth temperature (20°C) was not completely blocked by the heat shock. More than 12 h was needed for the reappearance of the normal protein synthesis pattern after heat shock.     

Competitive interaction in plant populations exposed to supplementary ultraviolet-B radiation

Summary Changes in plant growth and competitive balance between pairs of competing species were documented as a result of supplementary ultraviolet-B radiation (principally in the 290–315 nm waveband) under field conditions. This component of the terrestrial solar spectrum would be intensified if the atmospheric ozone layer were reduced. A method for calculating and statistically analyzing relative crowding coefficients was developed and used to evaluate the competitive status of the species pairs sown in a modified replacement series. The effect of the supplementary UV-B irradiance was generally detrimental to plant growth, and was reflected in decreased leaf area, biomass, height and density as well as changes in competitive balance for various species. For some species, interspecific competition apparently accentuated the effect of the UV-B radiation, while more intense intraspecific competition may have had the same effect for other species. A few species when grown in a situation of more severe mutual interspecific competition exhibited enhanced growth under the UV-B radiation treatment. This, however, was usually associated with a detrimental effect of the radiation on its competitor and thus was likely the result of its improved competitive circumstance rather than a beneficial physiological effect of the radiation.     

Increased CO2 and nutrient status changes affect phytomass and the production of plant defensive secondary chemicals in Salix myrsinifolia (Salisb.)

The effect of CO₂ enrichment (700 and 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and secondary chemicals of three Salix myrsinifolia clones was studied in plants cultivated at very poor (sand seedlings) and moderate (peat seedlings) nutrient availability and under low illumination. The total shoot phytomass production of sand scedlings was less than 10% of that of the peat seedlings. Carbon dioxide increased the total shoot phytomass of peat seedlings. When the ambient carbon supply was doubled (to 700 ppm) the growth of sand seedlings was slightly enhanced but 1050 ppm CO₂ gave growth figures similar to those at the control CO₂ level. Leaf nitrogen content and total soluble sugar contents were significantly higher in peat seedlings than in sand seedlings. Leaf nitrogen showed a decreasing trend in relation to CO₂ increase. On the other hand, CO₂ did not have any clear-cut effect on total sugars. At the control CO₂ level the content of salicortin, which is a dynamic phenolic, was higher in the peat seedlings than in the sand seedlings, but salicin showed the opposite trend. CO₂ enrichment considerably decreased these phenolics in the peat seedlings. At the control CO₂ level, the content of more static phenolics, such as proanthocyanidins, was higher in sand seedlings. An increased carbon supply considerably increased static phenolics in the peat seedlings. Willow defence against generalist herbivores is moderately decreased by enhancement of atmospheric carbon dioxide.     

Genomic mutation in lines of Arabidopsis thaliana exposed to ultraviolet-B radiation

Studies that have attempted to estimate the rate of deleterious mutation have typically been conducted under low levels of ultraviolet-B (UV-B) radiation, a naturally occurring mutagen. We conducted experiments to test whether the inclusion of natural levels of UV-B radiation in mutation-accumulation (MA) experiments influences the rate and effects of mildly deleterious mutation in the plant Arabidopsis thaliana. Ten generations of MA proved insufficient to observe significant changes in means or among-line variances in experimental lines maintained either with or without supplemental UV-B radiation. Maximum-likelihood estimates of mutation rate for total flower number revealed a small but significant rate of mutation for MA lines propagated under supplemental UV-B exposure, but not for those in which supplemental UV-B was omitted. A fraction of the flower number mutations under UV-B (approximately 25-30%) are estimated to increase flower number. Results from the application of transposon display to plant materials obtained after MA, in both the presence and absence of supplemental UV-B, suggest that the average rate of transposition for the class I and II transposable elements (TEs) surveyed was no more than 10(-4). Overall, the estimates of mutation parameters are qualitatively similar to what has been observed in other MA experiments with this species in which supplemental UV-B levels have not been used. As well, it appears that naturally occurring levels of UV-B do not lead to detectable increases in levels of transposable element activity.     

种子植物对中波紫外辐射胁迫的响应研究进展

臭氧层的破坏导致到达地表的中波紫外辐射(UV-B)增加。增强的UV-B对植物产生不同程度的胁迫作用。综合论述了近些年来有关种子植物对UV-B胁迫响应的研究进展。对UV-B敏感的种子植物经UV-B处理,外部形态表现为植物变矮、叶面积减小、茎缩短等;内部结构表现为叶绿体结构失去完整性、叶肉面积减小等。种子植物受UV-B影响的主要部位包括光合器官、遗传物质、蛋白质等。为了减轻UV-B的伤害,种子植物形成了一系列的保护机制,包括表皮结构对UV-B的散射、反射,叶片厚度的增加、UV-B吸收物质的积累、受损DNA的修复、自由基的去除。此外,UV-B与干旱、增强C02具有互作效应。增强的UV-B对木本植物、生态系统等方面的影响研究应加以重视。     

Nitrogen-induced reduction in leaf phenolic level is not accompanied by increased rust frequency in a compatible willow (Salix myrsinifolia)‐Melampsora rust interaction

Phenolic compounds are potential antimicrobial agents in willows ( Salix spp.). However, little is known about their role in willow‐pathogen interactions. Earlier studies have shown that phenolic levels may vary depending on genotype and environmental factors (such as nutrient availability). In the present study, the combined effects of nitrogen fertilization and infection by pathogenic rust ( Melampsora sp.) on phenolics and growth in willow ( salix myrsinifolia ) clones were investigated. Cutting-propagated plants of eight willow clones were subjected to low and optimum levels of nitrogen fertilization and inoculated with rust urediniospores or mock-inoculated with water. The plants were harvested 20 days after the inoculations and the dry weight of the leaves, stems and roots determined. Phenolics were analysed from leaf material using HPLC. The willow clones differed significantly in their phenolic content, rust frequency and phytomass production. Plants under optimum nitrogen availability showed increased shoot phytomass production and reduced root production. Rust infection increased the root phytomass of willow under both fertilization treatments, but had no consistent effect on the shoot growth of the clones. Low nitrogen availability increased the phenolic levels in willow leaves, but the rust frequency did not differ significantly between plants grown at low and optimum levels of nitrogen fertilization. In several clones, rust infection increased the concentrations of individual phenolic compounds, but there were no significant correlations between phenolic concentrations and the level of rust infection. The results indicate that resistance in compatible willow‐rust interactions may not be directly governed by phenolic compounds.     

Patterns of clonal diversity in three species of sub-arctic willow (Salix lanata, Salix lapponum and Salix herbacea)

Sub-arctic willow scrub is an endangered habitat in Britain, and typically occurs on steep crags inaccessible to grazing animals. These willows can reproduce both sexually and asexually, although the relative importance of each is unknown. Knowledge of reproductive mode is important for the design of grazing management and restoration programmes. Accordingly, clonality was assessed in the largest stand of sub-arctic willow scrub in the UK, focusing on Salix lanata and S. lapponum. Little evidence of clonal growth was detected; most individuals possessed distinct multi-locus genotypes. Thus despite the capacity for vegetative reproduction, and seedlings being rarely observed, sexual reproduction is the predominant means of perpetuation and dispersal at this site. We also examined clonal growth in a common willow species (Salix herbacea) that occupies a different habitat type (exposed mountain tops and ridges). Multiple individuals shared identical genotypes up to 7 m apart, suggesting an important role for clonal growth in local patch formation in this species.     

Sensitivity of duckweed (Lemna major) to ultraviolet-B radiation

The sensitivity of an important aquatic macrophyte, duckweed (Lemna major), to UV-B radiation was studied under experimental conditions at three different doses designated as no, mild, and severe injury dose by observing visible injury symptoms and estimating levels of chlorophyll, pheophytin, carotenoids, protein, starch, free sugar, and peroxidase activity. Laboratory-grown duckweed plants were exposed to UV-B radiation at 0.4 mW/cm(2) intensity for different time periods. Mild and severe injury were developed at 6.48 and 8.64 J, respectively. Peroxidase activity increased at all the exposure levels. Dose-dependent decrease in chlorophyll and starch with drastic depletion in protein and free sugar content were observed. Pheophytin and carotenoids content increased at no injury level, but decreased at higher exposure level. The results indicate that ambient UV-B radiation at the indicated level acts as a physiological stress in Lemna major.     

Differential response of leaf gas exchange to enhanced ultraviolet-B (UV-B) radiation in three species of herbaceous climbingplants

We measured diurnal changes in photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency in three species of herbaceous climbing plants (Luffa cylindrica, Trichosanthes kirilowii and Dioscorea opposita) exposed to two intensities of UV-B radiation: 3.0 μw cm^?2 (R1) and 8.0 μw cm^?2 UV-B (R2) radiation under ambient growth conditions. Responses differed per species and per treatment. In Luffa all values increased compared to the Control in both treatments, except for stomatal conductance in R2. In Trichosanthes photosynthetic rates and water use efficiency increased, while the transpiration rates decreased under both treatments, and stomatal conductance was lower in R1. In Dioscorea photosynthetic rates and water use efficiency decreased under both treatments, while the transpiration rates and stomatal conductance increased. The results suggested that to some extent increased UV-B radiation was beneficial to the growth of L. cylindrica and T. kirilowii, but detrimental to D. opposita.     

Differential response of leaf gas exchange to enhanced ultraviolet-B (UV-B) radiation in three species of herbaceous climbingplants

We measured diurnal changes in photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency in three species of herbaceous climbing plants (Luffa cylindrica, Trichosanthes kirilowii and Dioscorea opposita) exposed to two intensities of UV-B radiation: 3.0 μw cm^?2 (R1) and 8.0 μw cm^?2 UV-B (R2) radiation under ambient growth conditions. Responses differed per species and per treatment. In Luffa all values increased compared to the Control in both treatments, except for stomatal conductance in R2. In Trichosanthes photosynthetic rates and water use efficiency increased, while the transpiration rates decreased under both treatments, and stomatal conductance was lower in R1. In Dioscorea photosynthetic rates and water use efficiency decreased under both treatments, while the transpiration rates and stomatal conductance increased. The results suggested that to some extent increased UV-B radiation was beneficial to the growth of L. cylindrica and T. kirilowii, but detrimental to D. opposita.     

Soybean (Glycine max) pollen germination characteristics, flower and pollen morphology in response to enhanced ultraviolet-B radiation

BACKGROUND AND AIMS: Ultraviolet-B (UV-B) radiation effect on reproductive parts of the plants has received little attention. We studied the influence of UV-B radiation on flower and pollen morphology, pollen production and in vitro pollen germination and tube growth of six genotypes of soybean (Glycine max). METHODS: Soybean genotypes were investigated by growing them under four levels of biologically effective UV-B radiation of 0 (control), 5, 10 and 15 kJ m(-2) d(-1) in sunlit controlled-environment chambers. KEY RESULTS: Reductions in lengths of flower, standard petal, and staminal column along with reduced pollen production, germination and tube growth were observed in all genotypes with increasing UV-B radiation. Combined response index (CRI), the sum of percentage relative responses in flower size, pollen production, pollen germination and tube growth due to UV-B radiation varied with UV-B dosage: -67 to -152 with 5 kJ m(-2) d(-1), -90 to -212 with 10 kJ m(-2) d(-1), and -118 to -248 with 15 kJ m(-2) d(-1) of UV-B compared to controls. Genotypes were classified based on the UV-B sensitivity index (USI) calculated as CRI per unit UV-B, where D 90-9216, DG 5630RR and D 88-5320 were classified as tolerant (USI > -7.43), and DP 4933RR, Stalwart III and PI 471938 were sensitive (USI < -7.43) in their response to UV-B radiation. Pollen grains produced in plants grown at 15 kJ m(-2) d(-1) UV-B radiation were shrivelled and lacked apertures compared to control and other UV-B treatments in both sensitive and tolerant genotypes, and the differences were more conspicuous in the sensitive genotype (PI 471938) than in the tolerant genotype (D 90-9216). The number of columellae heads of the exine was reduced with increasing UV-B radiation. CONCLUSIONS: Soybean genotypes varied in their reproductive response to UV-B radiation. The identified UV-B tolerant genotypes could be used in future breeding programmes.     

Chlorophyll content and photosystem II efficiency in soybean exposed to supplemental ultraviolet-B radiation

Chlorophyll (Chl) a fluorescence parameters and rapid light curves of soybean [Glycine max (L.) Merrill] were measured by pulse amplitude modulation fluorometry. Measurements were taken during different stages of soybean growth under field conditions with 20% enhancement in ultraviolet-B (UV-B) radiation. Results showed that supplemental UV-B radiation decreased Chl contents by 5.5% (P=0.048), 8.7% (P=0.046), and 10.5% (P=0.005) in seedling, in branching-flowering, and in pod-setting stages, respectively. In the branching-flowering and pod-setting stages, maximum quantum yield of photosystem (PS) II photochemistry (F_v/F_m) decreased by 6.1% (P=0.001) and 3.0% (P=0.009), respectively. Supplemental UV-B radiation significantly decreased the effective quantum yield (Y). The photosynthetic capacity at light saturation (P_m) also decreased in both the seedling and branching-flowering stages by 28.9% (P=0.007) and 15.5% (P=0.041), respectively. However, Y and Pm showed no significant difference in the trefoil and pod-setting stages with and without the UV treatment. The light saturation parameter (E _k) decreased by 21.1% (P=0.000) and 23.2% (P=0.029) in the trefoil and seedling stages, respectively. Moreover, the initial slope (α) decreased by 21.1% (P=0.001) in the branching-flowering stage. Nonphotochemical quenching (NPQ) in the seedling stage and photochemical quenching coefficient (q_p) in the branching-flowering stage decreased significantly under UV-B treatments. The results of the present study suggest that supplemental UV-B radiation adversely affected Chl content and electron transport activity in PSII and consequently decreased the photosynthetic efficiency of soybean plants.     

Development of a hydroponic screening technique to assess heavy metal resistance in willow (Salix)

A nutrient thin film hydroponic system has been developed which allows rapid screening of willow (Salix) clones for their resistance to heavy metals, and hence their use in phytoremediation. Two clones known to be different in their resistance to heavy metals (Salix burjatica (Germany) and S. triandra x viminalis (Q83)), could be distinguished on the basis of leaf biomass, root biomass and stem height after 6 weeks. There were also differences in the uptake of heavy metals between the two clones.