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Light regulates inorganic nitrogen uptake and storage, but not nitrate assimilation, by the red macroalga Hemineura frondosa (Rhodophyta)

Citation

Paine, ER and Schmid, M and Revill, AT and Hurd, CL, Light regulates inorganic nitrogen uptake and storage, but not nitrate assimilation, by the red macroalga Hemineura frondosa (Rhodophyta), European Journal of Phycology, 56, (2) pp. 174-185. ISSN 0967-0262 (2020) [Refereed Article]

Copyright Statement

Copyright 2020 British Phycological Society

DOI: doi:10.1080/09670262.2020.1786858

Abstract

Macroalgal growth in temperate coastal ecosystems is primarily regulated by light and inorganic nitrogen availability. The effect of light (photon irradiance) on NO3 and NH4 + uptake, and NO3 assimilation, were studied in the red macroalga, Hemineura frondosa, which does not operate a carbon concentrating mechanism (non-CCM). Non-CCM macroalgae grow in low and high light environments but become increasingly dominant with depth, suggesting a mechanism for ‘preserving energy’ under low light levels. H. frondosa was acclimated to limiting (30 µmol photons m 2 s 1) and saturating (150 µmol photons m 2 s–1) irradiances for 8 days. Then, NO3 and NH4 + uptake rates were measured under limiting and saturating irradiances at six concentrations ranging from 2–64 μM. NO3 uptake did not follow saturating uptake kinetics at both irradiances suggesting multiple uptake mechanisms. NH4 + uptake saturated at concentrations <32 µM under limiting but not under saturating irradiance. Saturating irradiance resulted in greater maximum uptake rates of both NO3 and NH4 +. There was no evidence that irradiance regulated NO3 reduction by nitrate reductase. Also illustrated is the importance of measuring nitrate reductase activity on fresh material, as freezing in liquid nitrogen and storage at −80°C for 7 days caused a 65% decline in activity. Photosynthetic pigments, soluble tissue nitrogen and % total tissue nitrogen were all higher in limiting irradiance. In this first study of the nitrogen physiology of a non-CCM seaweed, we show that light regulates NO3 and NH4 + uptake but not NO3 assimilation.

Item Details

Item Type:Refereed Article
Keywords:red seaweed, algae, nitrogen uptake, nitrogen reductase
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Phycology (incl. marine grasses)
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the biological sciences
UTAS Author:Paine, ER ( Ellie Paine)
UTAS Author:Schmid, M (Dr Matthias Schmid)
UTAS Author:Hurd, CL (Professor Catriona Hurd)
ID Code:141156
Year Published:2020
Deposited By:Ecology and Biodiversity
Deposited On:2020-09-29
Last Modified:2021-06-07
Downloads:0

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