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971.
Abstract. Exposure of young bean foliage to acid rain induces free-radical-mediated lipid peroxidation and causes the same disruptive changes in the molecular organization of membrane lipid-bilayers that are observed during natural leaf senescence. Young plants were misted daily for 7d with simulated acid rain for a 2h period. Wide angle X-ray diffraction revealed the presence of gel-phase lipid in a fraction containing predominantly chloroplast membranes isolated from treated leaves, and the lipid-phase transition temperature of these membranes rose from below −30°C to ∼ 36°C over the treatment period. The formation of gel-phase lipid is known to be associated with lipid peroxidation, and it is therefore significant that production of ethane and levels of malondialdehyde in the leaves, which are both products of lipid peroxidation, rose throughout the treatment period. There was also increased production of ethylene and superoxide radical, which are typical responses of plant tissue to toxicity. 相似文献
972.
Comparative fluxome and metabolome analysis for overproduction of succinate in Escherichia coli
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973.
974.
Epiphytic lichen and bryophyte Floristic Richness (FR) and distribution were investigated in Lisbon and the adjacent southern riverbank, in the centre-west of Portugal within the Lisbon Metropolitan Area (LMA). Field studies were carried out in the years 2010–2011 to replicate research conducted 30 years ago in 1980–1981.Compared to previous surveys, we confirm that the overall environmental condition has largely improved, with higher epiphyte richness. The two areas have been recolonized during the last 30 years by sensitive species mainly due to changes in SO2 levels. However, the traffic-related NO2 and dust deposition have become the main pollutants and the increase of nitrophilous and saxicolous/terricolous taxa reflects this influence. But, besides air pollution, the important variable affecting the epiphytic flora of LMA, currently updated to more than 200 taxa, is the influence of arborisation system type, road type and road proximity of the new surveys, in addition to urbanization (calculated in an Index of Human Impact – IHI).According to their current epiphyte diversity, with Floristic Richness (RF) ranging from 4 to more than 90 taxa (lichens and bryophytes), five zones were identified in LMA and related with air quality.As a conclusion, significant changes in the Floristic Richness (FR) were observed over the past 30 years, not only the value but also the spatial pattern which differs greatly between the two areas, linked significantly with air quality and other human influences.Due to the few number of available air quality monitoring stations, in particularly for NO2 values, the important contributions of epiphytic flora in defining the distribution range and spatial patterns of urban disturbance imply that FR may be a practical and useful indicator of air quality in LMA. 相似文献
975.
976.
以外来入侵杂草紫茎泽兰(Eupatorium adenophorum L.)和本地土著杂草艾草(Artemisia argyi Levl)为材料,以自然光照为对照,用增强UV-B(0.46mW·cm-2·h-1)对材料进行7周辐射处理,随后停止辐射增强进行恢复试验,观察2种植物的生长状况,测定分析其光合特性、氧化物和抗氧化物含量、抗氧化酶活性的变化,探讨在紫外UV-B辐射增强条件下2种植物光合作用、光保护及损伤修复能力的差异。结果表明:(1)随着辐射时间的增长,2类植物叶片开放的PSⅡ反应中心激发能捕获效率(Fv′/Fm′)和PSⅡ凌晨最大潜在最大光化学效率(Fv/Fm)受到轻微抑制,但紫茎泽兰最大净光合速率(Pn max)受到的抑制比艾草更明显。(2)2类植物叶片内过氧化产物丙二醛(MDA)和超氧基离子(O-·2)的含量增加,但艾草中O-·2的相对累积比例比紫茎泽兰要高很多。(3)紫茎泽兰的抗氧化物抗坏血酸(ASA)和谷胱甘肽(GSH)的含量先增加后减少,艾草中的含量则保持在更高水平;2种植物的过氧化物酶(POD)和超氧化物歧化酶(SOD)活性都显著增强,抗坏血酸过氧化物酶(APX)活性都先增强后减弱,紫茎泽兰的过氧化氢酶(CAT)活性逐渐被抑制,而艾草则是先增强后减弱。研究认为,紫茎泽兰和艾草对UV-B辐射增强的光合作用和抗氧化系统响应过程类似但存在差异,对增强UV-B辐射环境的适应能力及抗逆性均较强。 相似文献
977.
M. C. Bartolomé A. A. Cortés A. Sánchez-Fortún M. G. Garnica-Romo S. Sánchez-Carrillo 《International journal of phytoremediation》2016,18(12):1171-1177
Changes induced on freshwater microalga Dictyosphaerium chlorelloides (Dcwt) acclimated in the laboratory until their survival in culture media enriched with cadmium 100 µM have been studied. Cadmium removal by living cells of this Cd-resistant (DcCdR100) strain was tested in cultures exposed to 100 µM Cd during 30 days. Cell dimensions were measured under light microscopy, and cell growth was studied. Photosynthetic yield (ΦPSII) was analyzed and the photosynthetic oxygen development and respiration response was obtained. Results show that DcCdR100 strain exhibited significant cell morphology changes in comparison to Dcwt cells, which affected both surface area and cell biovolume. Malthusian fitness analysis showed that DcCdR100 strain living in Cd-enriched culture had developed a lower capacity of nearly 50% growth, and its photosynthetic oxygen development and respiration response were significantly reduced in both light and dark photosynthetic phases. DcCdR100 strain showed a very high capacity to remove cadmium from the aquatic environment (over 90%), although most of the removed heavy metal (≈70%) is adhered to the cell wall. These specific characteristics of DcCdR100 cells suggest the possibility of using this strain in conjunction with Dcwt strain as bioelements into a dual-head biosensor, and in bioremediation processes on freshwater polluted with Cd. 相似文献
978.
979.
When offered a mixed diet of different zooplanktonic items covering a body size range of 75–2200 μm, (a) rohu, Labeo rohita and (b) singhi, Heteropneustes fossilis larvae ingested progressively larger prey as they grew, due to age-related increase in gape. However, a nearly constant prey size/mouth size ratio was maintained for a period of 4wk after hatching. The dominance of rotifers in the diet during the first 2-wk was followed by cladocerans, particularly Moina macrocopa. Significant differences observed in the growth rates of the larvae reared on different diet regimes were related to ontogenetic changes in prey selection. An exclusive copepod diet throughout resulted in the lowest weight gain in the larvae of both species. However, copepods had no apparent adverse effects when present with the preferred rotifers and cladocerans. Although constituting a suboptimal prey size for the older larvae, rotifers alone, when present in sufficient densities, produced growth rates comparable to those obtained on a cladoceran diet. However, a mixed diet regime contributed to the maximum growth. The implications of these findings to rearing larvae of the economically important rohu and singhi are discussed. 相似文献
980.
Robert J. Livingston 《Environmental Biology of Fishes》1988,22(3):225-234
Synopsis The species is not always appropriate as a unit of measure when used in quantitative ecological studies. Analyses of fish
trophic relationships in coastal areas indicate that, in many instances, more substantial ecological differences exist among
life stages of a given species than among similar trophic units of different species. The use of a species in quantitative
ecological studies can lead to problems of interpretation concerning the relationships of coastal fishes to complex habitats.
Use of the species as a convenient unit of measure substitutes a basically taxonomic entity for more relevant life-history
stages in ecological determinations. Niche breadth of a given species can be so extensive that quantitative determinations
of significant ecological processes are difficult to make. Migratory coastal fishes undergo diverse ontogenetic trophic transformations.
Without adequate recognition of the complex ecological stages that characterize such fishes, the oversimplification that characterizes
many ecological studies in coastal areas will continue. This simplification, and the attendant overgeneralization that follows,
tends to add to the continuing problem of unverified models and the inability to identify causal relationships in estuarine
and coastal systems. Quantitative ecological studies would benefit from an approach that includes the use of identifiable,
ontological trophic entities. 相似文献