Effects of UV radiation on photosynthesis and excretion of UV-absorbing compounds of Dasycladus vermicularis (Dasycladales, Chlorophyta) from southern Spain

Abstract

1998. Effects of UY radiation on photosynthesis and excretion of UY-absorbing compounds of Dasycladus vermicularis (Oasycladales, Chlorophyta) from southern Spain. Phy cologia 37: 379-387.Photosynthesis measured by chlorophyll fluorescence and oxygen exchange, pigment composition, and excretion of UY absorbing compounds were tested in the green alga Dasycladus vermicularis (Scopoli) Krasser following exposure to a combination of ultraviolet radiation and photosynthetically active radiation (PAR) in the laboratory. A preliminary chro matographic analysis of a thallus extract resulted in three separated substances, one showing an absorption maximum at 332 nm and two at 348 nm (UY-A). In contrast, the compound or set of compounds excreted to the medium had a spectrophotometric absorption maximum at 387 nm, indicating degradation or chemical conversion of the in situ precursors. The total absorbances of these UY-absorbing compounds in seawater and in the thallus were higher when plants were exposed to PAR alone (P) or to PAR + ultraviolet A and B radiation (PAB). This suggests that accumulation and excretion of this substance respond either to UY-B radiation or to a low irradiance of PAR. Pulse amplitude modulated fluorescence (PAM) and oxygen evolution were also affected by exposure to PAB and P. After 72 h exposure to PAB and P, the optimal (FiFm) quantum yield of fluorescence decreased between 15 and 30% compared to initial control, whereas lower photo inhibition of fluorescence occurred under PAR + UY-A conditions. Complete loss of O 2 evolution was observed in thalli irradiated for 24 h with PAB, whereas no effects after UY-A exposure were observed. In general, following 24 h exposure to the different treatments, an increase in light requirements for compensation (1,) and saturation (Ik) of photosynthesis was seen. Calculations of biologically effective UY doses using known action spectra revealed that fluorescence is impaired by 25% at UY-B doses above 900 kJ m-2 •

Physiological acclimation to gradients of solar irradiance within mats of the filamentous green macroalga Chaetomorpha linum from southern Spain

“…Additionally, Ultraphan 295 was used to correct for the decrease in irradiance produced by the plastic filter foils. The effects of the respective foils on the spectral distribution of solar radiation have been previously published (Pérez-Rodríguez et al 1998). Upon solar exposure, the temperature underneath the filter foils increased moderately by 2 to 3°C compared to uncovered algal stands.…”

Short-term effects of increasing CO2, nitrate and temperature on three Mediterranean macroalgae: biochemical composition

“…The release of phenolic compounds from C. tamariscifolia thalli at noon has been suggested to be a photoprotective mechanism under high irradiance conditions (Abdala-Díaz et al 2006, Celis-Plá et al 2014). In the green macroalga Dasycladus vermi cu laris, phenolic compounds (trihydroxycoumarins) with antioxidant capacity are released under stressful conditions, reducing photoinhibition and increasing the recovery capacity of the photosynthetic yield and productivity (Pérez-Rodríguez et al 1998, 2001. Thus, the combination of thallus thickness, phenolic compounds (and their positive response to temperature increase), antioxidant activity and the reduction in UV penetration by the release of phenolic compounds might give C. tamariscifolia an advantage over U. rigida in high light environments that could even result in a higher production of the first species, especially with increasing temperatures.…”

“…Investigations have been conducted in the field (in situ) and in experimentally controlled conditions under solar radiation (outdoor) and under artificial conditions (indoor). Mechanisms for acclimation to global climate changes have been evaluated as the effect on photoinhibition, photoprotection, nutrient uptake systems and patterns of growth, reproduction and morphogenesis of different developmental stages of macroalgae (Häder & Figueroa 1997, Gómez & Figueroa 1998, Figueroa et al 2003b, Villafañe et al 2003, De la Coba et al 2009). …”

Oxidative stress and enzymatic scavenging of superoxide radicals induced by solar UV-B radiation in <i>Ulva</i> canopies from southern Spain

“…Additionally, Ultraphan 295 was used to be able to discriminate the additional effect of the coverage of samples with the plastic filter foils compared to the samples exposed to unfiltered radiation. The optical characteristics of the respective filters were previously published by Pérez-Rodríguez et al (1998) and Bischof et al (2002b). Additionally, mats were exposed to unfiltered solar radiation and also placed under UG-5 filters (Schott, Mainz, Germany), which almost completely absorb PAR but exhibit a high transmission below 400 nm, allowing both UV-A and UV-B to pass.…”