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Title: Photosynthetic production of hidrogen peroxide by Ulva rigida C. Ag. (Chlorophyta)
Authors: Collen, Jonás
Jimenez del Río, Miguel
García-Reina, Guillermo 
Pedersén, Marianne
UNESCO Clasification: 241707 Algología (ficología)
Keywords: Chemical defence
Hydrogen peroxide
Mehler reaction
Issue Date: 1995
Journal: Planta 
Abstract: Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of Hz02 was light dependent with a production of l.2 µmol·g Fw-1 -h-1 in sea water (pH 8.2) at an irradi­ance of 700 µmol photons m-2 ,s-1 • The excretion was also pH dependen!: in pH 6.5 the production was not de­tectable ( < 5 nmol·g FW-1 ·h-1 ) but at pH 9.0 the produc­tion was 5.0 µmol·g FW- 1 ·h-1 • The production of H202 was totally inhibited by 3-(3,4-d ichlo ro phenyl}- I, l­dimethylurea (DCMU). The ability oí U. rigida growing in tanks (750 1) under a natural light regime to excre te H202 was checked and found to be seven times higher at 08.00 hours than other times of the day. The H202 con­centration in the cultivation tank (density : 2 g FW·I-1 ) reached the highest value (3 µM) at 11.00 hours. Photo­syn thesis was not influenced by H202 formation. The Hz02 is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW-' ·h-1 at pH 8.2 and 90 mmol·g Fw-1 -h-1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H202 prod uction. The H202 production is sufficiently high to be of physio­logical and ecological signiócance, and is suggested to be a part of the defence against epi- and endophytes
ISSN: 0032-0935
Source: Planta [ISSN 0032-0935], v. 196, p.225-230
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