Mechanism of Nitrogen Assimilation of Porphyra from New England

Mechanism of Nitrogen Assimilation of Porphyra from New England

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Intertidal seaweeds at different tidal elevations are exposed to various frequencies and durations of emergence. Their physiological activities (e.g. nutrient uptake) may be affected by water loss during emersion. I used some of the most cosmopolitan species of Porphyra (Rhodophyta, Bangiophyceae, Bangiales) to understand desiccation effects on nitrogen assimilation from coastal New England. Eulittoral and sublittoral species of Porphyra have different strategies for nutrient uptake. Nitrate uptake function recovered quickly after emersion of upper littoral P. umbilicalis , while lower- or sub-littoral P. leucosticta and P. yezoensis, respectively, could not recover their function. Population differences also were found for the upper and lower littoral populations of P. umbilicalis. The upper littoral population of P. umbilicalis was not affected by desiccation, whereas the nitrate uptake and nitrate reductase (NR) activity of the lower littoral population were significantly lower than those of non-desiccated controls post desiccation. Different Porphyra species with different cross-sectional thicknesses, from the same vertical habitats have different growth strategies when they experience periodic desiccation. When Porphyra experienced severe desiccation stress, the thinner species, P. linearis, grew slower (... at 540 nm was measured with a Spectronic Genesys 5 spectrophotometer ( Spectronic Instruments, Rochester, NY, U.S.A.). ... pH 7.3, 0.14% [v/v] 2- mercaptoethanol, 10 mM MnCl2, 10% [v/v] glycerol, 0.03% [v/v] Tween-20, 1% [w/ v] PWP).

Title:Mechanism of Nitrogen Assimilation of Porphyra from New England
Author:Jang Kyun Kim
Publisher:ProQuest - 2008


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