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Abstract Rich fens are common boreal ecosystems with distinct hydrology, biogeochemistry and ecology that influence their carbon (C) balance. We present growing season soil chamber methane emission (FCH4), ecosystem respiration (ER), net ecosystem exchange (NEE) and gross primary production (GPP) fluxes from a 9‐years water table manipulation experiment in an Alaskan rich fen. The study included major flood and drought years, where wetting and drying treatments further modified the severity of droughts. Results support previous findings from peatlands that drought causes reduced magnitude of growing seasonFCH4,GPPandNEE, thus reducing or reversing their C sink function. Experimentally exacerbated droughts further reduced the capacity for the fen to act as a C sink by causing shifts in vegetation and thus reducing magnitude of maximum growing seasonGPPin subsequent flood years by ~15% compared to control plots. Conversely, water table position had only a weak influence onER, but dominant contribution toERswitched from autotrophic respiration in wet years to heterotrophic in dry years. Droughts did not cause inter‐annual lag effects onERin this rich fen, as has been observed in several nutrient‐poor peatlands. WhileERwas dependent on soil temperatures at 2 cm depth,FCH4was linked to soil temperatures at 25 cm. Inter‐annual variability of deep soil temperatures was in turn dependent on wetness rather than air temperature, and higherFCH4in flooded years was thus equally due to increased methane production at depth and decreased methane oxidation near the surface. Short‐term fluctuations in wetness caused significant lag effects onFCH4, but droughts caused no inter‐annual lag effects onFCH4. Our results show that frequency and severity of droughts and floods can have characteristic effects on the exchange of greenhouse gases, and emphasize the need to project future hydrological regimes in rich fens.
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Coumarin‐based Fluorescent Probes for Selectively Targeting and Imaging the Endoplasmic Reticulum in Mammalian Cells
Abstract Developing improved fluorescent probes for imaging the endoplasmic reticulum (ER) is necessary for structure‐activity studies of this dynamic organelle. Two coumarin‐based compounds with sulfonamide side groups were synthesized and characterized asER‐targeting probes. Their selectivity to target theERin HeLa andGM07373 mammalian cells was shown with co‐localization experiments using commercially available probes that localize in theER, mitochondria, or lysozymes. The hydrophobicity of the coumarin‐based probes was comparable to known probes that partition into theERmembrane. Their cytotoxicity in mammalian cells was low withIC50 values that range from 205 to 252 μm. The fluorescent quantum yields of the coumarin‐based probes when excited with 400 nm light were 0.60, and they have a much narrower emission spectrum (from 435 to 525 nm in methanol) than that of the only commercially availableERprobe that is exited with 400 nm light (ER‐Tracker™ Blue‐WhiteDPX). Thus, the coumarin‐based probes are more useful for multicolor imaging with yellow and red emitting fluorophores. In addition to the above benefits,ERlabeling was achieved with the coumarin‐based probes in both live cells and fixed cells, revealing their versatility for a wide range of cellular imaging applications.
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- Award ID(s):
- 1709099
- PAR ID:
- 10072715
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Photochemistry and Photobiology
- Volume:
- 95
- Issue:
- 2
- ISSN:
- 0031-8655
- Page Range / eLocation ID:
- p. 556-562
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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