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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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We present an in-depth decompositionanalysis using physical indicators oftrends in Carbon dioxide (CO2) emissions in the cementindustry in Brazil, China, South Korea andthe United States. Physical indicatorsallow a detailed analysis of intra-sectoraltrends, in contrast to the often usedmonetary indicators. We assess thecontribution of different factors affectingCO2 emissions in the cement industry,including change in product mix, efficiencyof power generation, changes in fuel mixand changes in energy efficiency. Thedecomposition results show that in allexamined countries, increased productionwas the main contributor to the increase intotal CO2 emissions. Energy-efficiencyimprovement is the most important factorthat led to the reduction of emissionintensities for all countries except Korea.For Korea, structural change in the productmix is the most important factorcontributing to the emission intensityreduction. 相似文献
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