Effects of solar radiation on photoinhibition and pigmentation in the red alga Porphyra leucosticta

Abstract

ABSTRACT-The effect of solar radiation on photosynthesis, quantum yield of fluorescence and pigmentation under solar radiation in a laboratory system and in the natural habitat during a daily cycle was investigated in the red eulittoral alga Porphyra leucost~cta. Optimal (F,/F,,,) and effective (hF/Fm') quantum y~e l d of fluorescence, photosynthetic efficiency and maximal photosynthesis were drastically reduced by (!V-B (280-315 nm) radiation in algac transferred from the laboratory (grown in white light) to solar radiation for 3 h. The absorptance due to chlorophyll and biliproteins (phycoerythrin and phycocyanln) increased after 3 h of incubation In photosynthetically actlve radiation (PAR, 400-700 nm) and PAR+UV-A (315-400 nni) whereas no changes were observed under PAR+UV-A+UV-B In the field, the effcctive quanturn y e l d and oxygen production decreastd at noon durlng a diiily cycle, indicating photolnhibition. When solar UV-A and UV-B radiation was removed by means of selective filters, the average effcctive quantum yield increased by 28 -c 2 " . I SD. Chlorophyll and biliprotein concentration presented a daily pattern which was affected by UV radiation Both chlorophyll and biliprotein contents were reduced at noon, follo\~ved by recovery in the afternoon, but only when UV radiation was cut off. The difference between the maximal and minimal chl a concentration during the dally cycle was greater in the presence of UV radiation, but the difference for phycoerythrin and phycocyanin was greater under PAR alone. These results seem to indicate that the accuniulation of pigments is affected by solar radiation, with short-term changes induced by UV light. The ecological relevance of the daily variations of photosynthesis and pigmentation under solar radiat~on is discussed.

Effects of solar ultraviolet radiation on photosynthesis of the marine red tide alga Heterosigma akashiwo (Raphidophyceae)

“…Duplicate samples were used in all radiation treatments. The transmission spectra of these materials are published in Figueroa et al [3].…”

“…Solar ultraviolet radiation (UVR, 280-400 nm), and the increase of UV-B radiation (280-315 nm) due to ozone depletion, has a range of effects on phytoplankton [1][2][3]. They include, among others, the impact on growth, metabolism, motility, photo-orientation, pigmentation and photosynthetic capability of phytoplankton [3][4][5][6].…”

“…They include, among others, the impact on growth, metabolism, motility, photo-orientation, pigmentation and photosynthetic capability of phytoplankton [3][4][5][6]. One of the processes that received particular attention is photosynthesis, as solar energy is directly used by autotrophic organisms, and thus any change on UVR might affect primary production [7].…”

Influência da disponibilidade de nitrato sobre crescimento, atividade da nitrato redutase, composição química e captação de nitrato e fosfato em Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)

“…O pH do tampão fosfato também pode influenciar a extração das ficobiliproteínas , sendo que na literatura são encontrados valores de pH variando de 5,5 a 7 Figueroa et al, 1995Figueroa et al, , 1997Sampath-Wiley & Neefus, 2007), apesar do pH do cloroplasto ser 8,0 (Raven et al, 2001), que poderia ser o pH ideal para a extração das ficobiliproteínas. Porém, nenhum desses trabalhos aborda qual seria o melhor pH para a extração deste pigmento fotossintetizante.…”

“…Porém, descreveram fórmulas apenas para ficoeritrina e ficocianina, visto que a quantificação de aloficocianina por espectrofotometria é dificultada pela presença de pequenas quantidades de clorofila a no extrato, a qual interfere na absorção da luz. As fórmulas descritas por A acetona, diluída a 90%, é um dos solventes orgânicos mais usados para a extração de clorofilas (Jeffrey & Humphrey, 1975;Figueroa et al, 1995Figueroa et al, , 1997Yokoya et al, 2007). Recentemente, outros solventes orgânicos têm sido empregados para a extração de clorofilas e novas fórmulas têm sido desenvolvidas para a sua quantificação, uma vez que o coeficiente de extinção das clorofilas varia de acordo com o tipo de solvente e sua diluição.…”