During the summer months, wet (hyporheic) soils associated with ephemeral streams and lake edges in the Antarctic Dry Valleys (DVs) become hotspots of biological activity and are hypothesized to be an important source of carbon and nitrogen for arid DV soils. Recent research in the DV has focused on the geochemistry and microbial ecology of lakes and arid soils, with substantially less informat...

In this work the spectroscopic properties of the special low-energy absorption bands of the outer antenna complexes of higher plant Photosystem I have been investigated by means of low-temperature absorption, fluorescence, and fluorescence line-narrowing experiments. It was found that the red-most absorption bands of Lhca3, Lhca4, and Lhca1-4 peak, respectively, at 704, 708, and 709 nm and are ...

The effects of floating macroalgae (250 g DW m(-2)) on photoautotrophic microbenthos were studied in a flow-through mesocosm with a parallel mesocosm without macroalgae serving as Control. Vertical microprofiles of O(2) at the sediment-water interface showed a immediate and complete suppression of photosynthetic activity of microphytobenthos (MPB) under the macroalgal canopy, resulting in a shi...

The earliest primary photochemical reaction of green plant photosynthesis has, thus far, remained unexplored as reaction center chlorophyll a (Chl a) complexes have not yet been isolated [l] . In contrast, primary photochemical steps have been successfully studied, with picosecond (ps) absorption spectroscopy [2,3] in isolated bacteriochlorophyll (B Chl)-reaction center complexes from photosynt...

The cyanobacterium Synechococcus sp. PCC 7942 possesses a small psbA multigene family that codes for two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We showed previously that the normally predominant D1 form (D1:1) was rapidly replaced with the alternative D1:2 when cells adapted to a photon irradiance of 50 mumol.m-2.s-1 are shifted to 500 mumol.m-2.s-1 and...

[1] Satellite data show that oceanic eddies generated in the Southern Antarctic Circumpolar Current Front (SACCF) are associated with increased phytoplankton biomass. Cyclonic eddies with high chlorophyll a concentration (Chl-a) retain phytoplankton within the eddy cores and increase the light available for photosynthesis in the upper mixed layer by limiting vertical mixing and lifting of the i...

Phytoplankton biomass and productivity have been continuously monitored from ocean color satellites for over a decade. Yet, the most widely used empirical approach for estimating chlorophyll a (Chl) from satellites can be in error by a factor of 5 or more. Such variability is due to differences in absorption and backscattering properties of phytoplankton and related concentrations of colored-di...

In the course of a study of the pigment composition of some marine algae (6) certain organisms were found to possess highly active systems capable of converting chlorophyll a to chlorophyllide derivatives. Two chlorophyllides could be obtained from the diatom Phaeodactylnin tricornutunt (Bohlin) depending on the conditions of incubation. One possessed a spectrum identical with chlorophyll a, an...

We imaged reflectance and variable fluorescence in 25 cyanobacterial mats from four distant sites around the globe to assess, at different scales of resolution, spatial variabilities in the physiological parameters characterizing their photosynthetic capacity, including the absorptivity by chlorophyll a (A chl), maximum quantum yield of photosynthesis (Y max), and light acclimation irradiance (...

Foliar frost resistance of three endemic New Zealand land trees, Nothofagus menziesii (Hook. f.) Oerst. (Fagaceae), Pittosporum eugenioides A. Cunn. (Pittosporaceae) and Griselinia littoralis Forst. f. (Cornaceae), was examined as the trees hardened from late summer to midwinter in a lowland forest site. The lowest temperatures causing 50% damage (LT(50)) occurred in late winter and were simila...