An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta)

Longstaff, B. J., Kildea, T., Runcie, J. W., Cheshire, A., Dennison, W. C., Hurd, C., Kana, T., Raven, J. A. and Larkum, A. W. D. (2002) An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta). Photosynthesis Research, 74 3: 281-293. doi:10.1023/A:1021279627409

Author Longstaff, B. J.
Kildea, T.
Runcie, J. W.
Cheshire, A.
Dennison, W. C.
Hurd, C.
Kana, T.
Raven, J. A.
Larkum, A. W. D.
Title An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta)
Journal name Photosynthesis Research   Check publisher's open access policy
ISSN 0166-8595
Publication date 2002-12-01
Sub-type Article (original research)
DOI 10.1023/A:1021279627409
Open Access Status Not yet assessed
Volume 74
Issue 3
Start page 281
End page 293
Total pages 13
Place of publication Dordrecht, Netherlands
Publisher Kluwer Academic Publishers
Language eng
Subject C1
270402 Plant Physiology
770403 Living resources (flora and fauna)
Abstract Direct comparisons between photosynthetic O-2 evolution rate and electron transport rate (ETR) were made in situ over 24 h using the benthic macroalga Ulva lactuca (Chlorophyta), growing and measured at a depth of 1.8 m, where the midday irradiance rose to 400-600 mumol photons m(-2) s(-1). O-2 exchange was measured with a 5-chamber data-logging apparatus and ETR with a submersible pulse amplitude modulated (PAM) fluorometer (Diving-PAM). Steady-state quantum yield ((Fm'-Ft)/Fm') decreased from 0.7 during the morning to 0.45 at midday, followed by some recovery in the late afternoon. At low to medium irradiances (0-300 mumol photons m(-2) s(-1)), there was a significant correlation between O-2 evolution and ETR, but at higher irradiances, ETR continued to increase steadily, while O-2 evolution tended towards an asymptote. However at high irradiance levels (600-1200 mumol photons m-(2) s(-1)) ETR was significantly lowered. Two methods of measuring ETR, based on either diel ambient light levels and fluorescence yields or rapid light curves, gave similar results at low to moderate irradiance levels. Nutrient enrichment (increases in [NO3-], [NH4+] and [HPO42-] of 5- to 15-fold over ambient concentrations) resulted in an increase, within hours, in photosynthetic rates measured by both ETR and O-2 evolution techniques. At low irradiances, approximately 6.5 to 8.2 electrons passed through PS II during the evolution of one molecule of O-2, i.e., up to twice the theoretical minimum number of four. However, in nutrient-enriched treatments this ratio dropped to 5.1. The results indicate that PAM fluorescence can be used as a good indication of the photosynthetic rate only at low to medium irradiances.
Keyword Plant Sciences
Benthic Algae
Electron Transport
Nutrient Uptake
Oxygen Evolution
Primary Production
Pulse Amplitude Modulation
Modulated Pam Fluorometry
Algal Community
O-2 Evolution
Quantum Yield
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biological Sciences Publications
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