peer reviewed article for euglena light 2

peer reviewed article for euglena light 2 - PHYSIOLOGIA...

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PHYSIOLOGIA PLANTARUM 91: 69fv-702, 1994 frinli'd in Ih'nnuirk - al! rights yexeryeil ! © Physii' ISSN i PlunUniiin 1994 Influence of UV-B radiation on photosynthetic light-response curves, ahsorption spectra and motility of four phytoplankton species Nils G. A, Ekeluttd Ekelund. N. G. .\. 1994, Inlluence of UV-B radiatictti on photosynthelic light-response curves, absorption spectra and motility ol' four phvioplankton species, - Physiot, Piant. 91: 696-702. Sevetai unicellular algae wete exposed to artificial UV-B (280-320 nm) radiation after adaptation to high (43 W m"-) and lov\ (19 W nr"\ visible light. UV-B radiation had different effects on rates of photosynthesis, motility and absorption spectra for Ihese species. Photosynthesis of Fuglena gracilis and the diatom Phaeodai tvUmi tricornu- tum vvas more sensitive to UV-B inhibition than that of the dinoflagellates Heterocapsa Iriqiietra and Prnrncentnini minimum. Not only UV-B radiation hut also high visible lighl had a photoinhibitory effect on photosynthesis in all four organisms. The effect on photosynthesis was observed hoth on the quantum yield and on the light saturation rate of photosynthesis. The dinoflagellales. in contrast to £. gracilis and P. triiomutuni. absorbed strongly in the UV region (334 nm) and their absorption peaks increased after growth under high visible light or with or without UV-B radiation for one week. The swimming speed of H. triquctni decreased more after low visible light and UV-B radiation compared to high visible light and UV-B radiation. The negative effects of LiV-B radiation on P. niinimuni and F. gracilis were most pronounced ai'ter hieh visible light. Key HYirt/.v - Eiiglena gradlis. Heterocapsa iric/uelm. motility. Phaeoduayium iri- conninmi. photoinhibilion. photosynthesis. Prorotenmmi minimum. UV-B radiatton 1280-320 nm). N.G. .\. Fkehind. Lund Univ. . Section of Plant Phvsiotogv. PO. Bo.x 117. S-221 00 Lund. Sweden. Introductiort Tbe penetralion of sunligbl into tbe water column de- pends on latitude, biological aclivity, tbe amount of humic substances in tbe water and time of tbe year (Kramer 1990). Anotber important factor for tbe lighl exposure of pbytoplankton is vertical mixing which dis- tributes the plankton in tbe water column (Pierson 1990). Radiation of shorter wavelengths close to the water sur- face depends strongly on column ozone which has de- clined at norlbeni latitudes during the ia.st decade (Frede- rick 1993). The result of ozone depletion in tbe strato- spbere is an inerease in the amount of UV-B radiation W^O nm) reaching the eanb's suti'ace (Ambaeb and Blumthaler 1993, Frederick 1993). Few plankton orga- nisms have been investigated and tbese organisms bave differed greatly in sensitivity to increased ultraviolet ra- diation, tbetefore it is a great need for furtber investiga- tions. Ultraviolet radiation causes damage to photosystem II (Jones and Kok 1966). Tbe deerease in pbotosynthelic activity tbat occurs wben a plant is exposed to UV-B or bigb irradiances of visible ligbt is termed photoinbibition (Tyystjarvi 199.3). Smith et al. (1980) have shown that
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peer reviewed article for euglena light 2 - PHYSIOLOGIA...

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