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31.
Growth as an integrative parameter of all physiological processes was measured in young sporophytes of temperate Laminaria digitata, Laminaria saccharina and Laminaria hyperborea exposed in the laboratory to irradiance consisting of either only photosynthetically active radiation (PAR) or to a spectrum
including ultraviolet radiation (UVR) (PAR+UVA+UVB) by use of cut-off glass filters. Size increment was measured every 10 min
over a period of 18–21 days using growth chambers with on-line video measuring technique. In the chamber, plants were grown
at 10±2°C and 16:8 h light–dark cycles with 6 h additional UVR exposure in the middle of the light period. Tissue morphology
and absorption spectra were measured in untreated young sporophytes while chlorophyll a content and DNA damage were measured
in treated thalli at the end of the experiment. Sensitivity of growth under UVR was found to be related to the observed upper
depth distribution limit of the upper sublittoral L. digitata, upper to mid sublittoral L. saccharina and lower sublittoral L. hyperborea. Tissue DNA damage is, however, dependent on thallus thickness which minimizes UVR effect where outer cell layers shade inner
cells and provide longer pathlength for UVR. Exposure to UVR causes cellular, enzymatic and molecular damage. Presence of
UV-absorbing compounds further reduces effective UVR from reaching physiological targets. The cost of producing higher amount
of UV-absorbing compounds and effective DNA repair mechanism can, however, divert photosynthate at the expense of growth.
Tissue chlorophyll a content was not significantly different between treatments suggesting a capacity for acclimation to moderate
UVR fluence. Growth acclimation to repeated UVR exposure was observed within a period of 12 days while growth inhibition was
observed after a longer UVR exposure period of 21 days. The results give further insight into the effects of UVR on the cellular
level and show how ecological parameters such as the upper depth distribution limit are dependent on cellular processes. 相似文献
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The ocean plays a central role in the global carbon cycle being by far the largest active reservoir. Atmospheric CO2 level depends on the CO2concentration in the ocean surface layer, which is relatively low compared to mean oceanic values due to biological and physical carbon pumps. Although the ocean may take up much of the carbon released by the increased burning of fossil fuels, this capacity is limited because of the chemical buffering and a mismatch in time scales (oceanic mixing is much slower than anthropogenic perturbations). 相似文献
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The Science of Nature - 相似文献
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Hermann H. Dieter 《Environmental management》1992,16(1):21-31
The limit value of 0.1 μg/liter for “substances used in plant treatment and pest control including their main toxic degradation
products” (PBSM) established in the German Drinking Water Regulations (Trinkwasserverordnung) serves comprehensively to protect
drinking water from unexpected toxicological risks and thus corresponds to theaxiom of concern (Besorgnisgrundsatz) contained in §11,2 of the Federal Communicable Disease Control Act (Bundesseuchengesetz), which is an
essential cornerstone of the Drinking Water Regulations. Furthermore, precautionary values that are specific to the particular
substance and near the valid limit can be found for about 10% of all registered active substances. The goal of the PBSM Recommendations
of the Federal Health Office (BGA) issued in July 1989 is to preserve and restore groundwater and drinking water through measures
to be taken by the causal party, while reducing consumer health risks to the greatest extent possible. The EC commission's
drawbacks on these recommendations and the imminent EC-wide directive for the uniform registration of pesticides being based
solely on Article 43 of the European Treaty would seriously endanger this goal. Therefore, a situation threatens in Europe
similar to that in the United States, where at least 18 active ingredients have been detected in groundwater in concentrations
of up to 1000 times the toxicologically established limits for drinking water.
This article appeared first in the German journal?ffentliches Gesundheitswesen 52(8–9); 372–379, 1990. We thank the editor (Georg Thieme Verlag, D-7000 Stuttgart) for the kind permission to publish this
slightly revised English version inEnvironmental Management. 相似文献
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Plant chemistry and insect sequestration 总被引:2,自引:1,他引:1
Most plant families are distinguished by characteristic secondary metabolites, which can function as putative defence against
herbivores. However, many herbivorous insects of different orders can make use of these plant-synthesised compounds by ingesting
and storing them in their body tissue or integument. Such sequestration of putatively unpalatable or toxic metabolites can
enhance the insects’ own defence against enemies and may also be involved in reproductive behaviour. This review gives a comprehensive
overview of all groups of secondary plant metabolites for which sequestration by insect herbivores belonging to different
orders has been demonstrated. Sequestered compounds include various aromatic compounds, nitrogen-containing metabolites such
as alkaloids, cyanogenic glycosides, glucosinolates and other sulphur-containing metabolites, and isoprenoids such as cardiac
glycosides, cucurbitacins, iridoid glycosides and others. Sequestration of plant compounds has been investigated most in insects
feeding or gathering on Apocynaceae s.l. (Apocynoideae, Asclepiaoideae), Aristolochiaceae, Asteraceae, Boraginaceae, Fabaceae and Plantaginaceae, but it also occurs
for some gymnosperms and even lichens. In total, more than 250 insect species have been shown to sequester plant metabolites
from at least 40 plant families. Sequestration predominates in the Coleoptera and Lepidoptera, but also occurs frequently
in the orders Heteroptera, Hymenoptera, Orthoptera and Sternorrhyncha. Patterns of sequestration mechanisms for various compound
classes and common or individual features occurring in different insect orders are highlighted. More research is needed to
elucidate the specific transport mechanisms and the physiological processes of sequestration in various insect species. 相似文献