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401.
The complexity of nectar: secretion and resorption dynamically regulate nectar features 总被引:2,自引:0,他引:2
In this paper, we review the phenomenon of nectar resorption, focusing on its physiological and ecological meaning. Nectar
resorption is a phenomenon that has long been known but was rarely reported until the1990s. It has more recently been demonstrated
in several species by various direct and indirect methodologies. It has generally been demonstrated in senescent flowers as
a phenomenon separate in time from, and independent of, nectar secretion. The significance of this type of resorption is generally
recognized as a resource-recovery strategy, recycling at least some materials invested in nectar production. Nevertheless,
nectar resorption can occur concomitantly with nectar secretion. Nectar production is therefore best considered as a unified
process comprising nectar secretion and resorption. The modulation of these two opposite phases allows nectar concentration
to be maintained in a range suitable for pollinators (nectar homeostasis). The mechanism of nectar resorption at the cell
level has received little attention, and its molecular basis can only be hypothesized on the basis of recent studies concerning
sugar sensing. 相似文献
402.
Mazur Karolina E. Borucka Aleksandra Kaczor Paulina Gądek Szymon Bogucki Rafał Mirzewiński Dariusz Kuciel Stanisław 《Journal of Polymers and the Environment》2022,30(6):2341-2354
Journal of Polymers and the Environment - In the study, polylactide-based (PLA) composites modified with natural particles (wood, bamboo, and cork) and with different levels of infilling (100%,... 相似文献
403.
The European Landscape Convention (2000) obligates European Union countries to identify and implement landscape quality objectives (LQOs) understood as the specification of public expectations and preferences concerning the landscape of a given area, expressed by competent public authorities. The convention emphasizes the important role of local community representatives in this field. In Poland, the implementation of the LQO concept was first undertaken in two regions with radically different landscape characteristics: (1) the West Polesie Biosphere Reserve and (2) the selected protected areas of the Roztocze–Solska Forest, nominated to the rank of a biosphere reserve. The first stage of the presented study was the recognition of public opinion on the quality of key features of landscape, based on a questionnaire (n = 470). The primary objective of the study was to provide an answer to the following questions: (1) Whether similar social expectations regarding landscape quality exist in spite of radically different landscape characteristics of the regions investigated (landscape quality is understood as spatial arrangement, scenic beauty, and lack of environmental pollution); (2) which landscape features are considered to be most preservation worthy by the representatives of both local communities; and (3) What processes or development impacts pose the greatest threat to the landscape quality of both regions according to the public opinion? The conducted comparative assessment revealed that it is possible to define a set of features fundamental to the quality of both areas and that representatives of local communities pointed out the same threats to the natural and cultural values of both regions investigated. 相似文献
404.
405.
Polybrominated diphenyl ethers (PBDEs) in mussels from selected French coastal sites: 1981-2003 总被引:1,自引:0,他引:1
The present study focused on the retrospective analysis of PBDEs in archived blue mussel (Mytilus edulis or Mytilus galloprovincialis) samples collected over the past 22 years (1981-2003) from coastal areas of France. We have found that PBDE levels in mussels from the English Channel increased markedly from 1981 to 1991-1995, doubling approximately every 5-6 years followed by a levelling off and a possible beginning of a decrease. The rate of the decline of hexa- and hepta-BDE congeners was more rapid than the decline of tetra- and penta-BDEs in these mussel samples. The difference in the course of time of lower and higher brominated PBDE concentrations suggests that the congener profile in the mussel samples changes over time. The increase in PBDE concentrations in the mussel samples contrasts with a concomitant constant decrease of chlorobiphenyls (CBs) in the same set of samples. However, pulse inputs of both groups of organohalogen compounds were determined for the mussel samples collected at the mouth of the Seine estuary and were probably related to riverine inundations and a flushing out of the deposited sediments from the internal estuary into the bay of the River Seine, as well as considerable dredging activities taking place during same years. In France, the highest PBDE concentrations were determined in the mussels from the English Channel, more precisely in the bay of the Seine, and the regional differences in PBDE levels were mainly connected to the difference in anthropogenic urban and industrial environmental pressures. Published data comparing PBDE levels in mussels have shown significant differences in concentrations between North/South America and Europe. This observation further confirms that the PBDE levels in the North American environment are higher than in Europe. However, the data used for this comparison of mussel contamination by PBDEs is still relatively sparse. 相似文献
406.
Wielgosiński G 《Journal of the Air & Waste Management Association (1995)》2011,61(5):511-526
The first reports that it is possible to emit dioxins from the heat and power generation sector are from the beginning of the 1980s. Detailed research proved that the emission of dioxins might occur during combustion of hard coal, brown coal, and furnace oil as well as coke-oven gas. The emission of dioxins occurs in wood incineration; wood that is clean and understood as biomass; or, in particular, wood waste (polluted). This paper thoroughly discusses the mechanism of dioxin formation in thermal processes, first and foremost in combustion processes. The parameters influencing the quantity of dioxins formed and the dependence of their quantity on the conditions of combustion are highlighted. Furthermore, the methods of reducing dioxin emissions from combustion processes (primary and secondary) are discussed. The most efficacious methods that may find application in the heat and power generation sector are proposed; this is relevant from the point of view of the implementation of the Stockholm Convention resolutions in Poland with regard to persistent organic pollutants. 相似文献