Figueroa Felix L, Nygård Charlotta, Ekelund Nils, Gómez Iván
Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos s/n, 29071 Málaga, Spain.
J Photochem Photobiol B. 2003 Dec 5;72(1-3):35-44. doi: 10.1016/j.jphotobiol.2003.09.002.
The effect of different wavebands of artificial UV (UVB and UVA) and photosynthetically active radiation (PAR) was assessed in two species of the genus Ulva, U. olivascens and U. rotundata, from southern Spain in order to test for possible differences in acclimation of photosynthesis. Both species share similar morphology but are subject to different light environments: U. rotundata is an estuarine alga, inhabiting subtidal locations, while U. olivascens is an intertidal, sun-adapted organism. Algae were exposed to three different UV conditions, PAR+UVA+UVB, PAR+UVA and PAR for 7 d. Short-term exposure (6 h) was also carried out, using two PAR levels, 150 and 700 micromolm(-2)s(-1). Pigment contents and photosynthesis vs. irradiance curves from oxygen evolution were used to contrast sun- and shade adaptation between these species. O2-based net photosynthesis (Pmax) and PAM-chlorophyll fluorescence (optimal quantum yield, Fv/Fm) were used as parameters to evaluate photoinhibition of photosynthesis in the experiments. The results underline different photobiological characteristics among species: the subtidal U. rotundata had higher contents of pigments (Chl a, Chl b and carotenoids) than the sun-adapted U. olivascens, which resulted in higher thallus absorptance and P-I parameters characterized by higher photosynthetic efficiency at limiting irradiances (alpha) and lower saturating points for photosynthesis (Ek). After 7 d exposure, photoinhibition of Fv/Fm was close to 40-45% in both species. Differences between UV treatments were seen in U. rotundata after 5 d and after 7 d in U. olivascens, in which PAR+UVA impaired strongly photosynthesis (80%). Such patterns were correlated with a progressive decrease in pigment contents, specially chlorophylls. In short-term (6 h) exposures, combinations of UVA+UVB and high PAR level resulted in high rates of photoinhibition of chlorophyll fluorescence (68-92%) in U. rotundata, whereas in U. olivascens photoinhibition ranged between 42% and 53%. Photoinhibition under low PAR combined to UV radiation was lower than observed under high PAR. Net O2-Pmax revealed similar response among the species, with maximal photoinhibition rates close to 60% in algae incubated under high PAR+UVA+UVB. In the case of UV exposure in combination with low PAR, the highest photoinhibition rates were measured in U. rotundata.
为了测试光合作用适应方面可能存在的差异，在来自西班牙南部的两种石莼属藻类——橄榄色石莼和圆形石莼中，评估了人工紫外线（UVB和UVA）以及光合有效辐射（PAR）不同波段的影响。这两种藻类形态相似，但所处光照环境不同：圆形石莼是一种河口藻类，栖息于潮下带位置，而橄榄色石莼是一种适应阳光的潮间带生物。将藻类暴露于三种不同的紫外线条件下，即PAR + UVA + UVB、PAR + UVA和PAR，持续7天。还进行了短期暴露（6小时），采用两种PAR水平，即150和700微摩尔每平方米每秒。色素含量以及基于氧气释放的光合作用与光强曲线被用于对比这些物种之间的阳生和阴生适应性。基于氧气的净光合作用（Pmax）和脉冲幅度调制叶绿素荧光（最佳量子产率，Fv/Fm）被用作实验中评估光合作用光抑制的参数。结果突显了不同物种间不同的光生物学特征：潮下带的圆形石莼比适应阳光的橄榄色石莼具有更高的色素（叶绿素a、叶绿素b和类胡萝卜素）含量，这导致其藻体吸收率更高，并且其光响应参数的特点是在低光强下光合效率更高（α），光合作用的饱和点更低（Ek）。暴露7天后，两种藻类的Fv/Fm光抑制均接近40 - 45%。在圆形石莼中，5天后可观察到紫外线处理之间的差异，而在橄榄色石莼中，7天后出现差异，其中PAR + UVA严重损害光合作用（80%）。这种模式与色素含量的逐渐降低相关，尤其是叶绿素。在短期（6小时）暴露中，UVA + UVB与高光强PAR水平的组合导致圆形石莼叶绿素荧光的光抑制率很高（68 - 92%），而在橄榄色石莼中，光抑制率在42%至53%之间。低PAR与紫外线辐射组合下的光抑制低于高光强PAR下观察到的情况。净氧气Pmax显示不同物种间有相似的响应，在高光强PAR + UVA + UVB下培养的藻类中，最大光抑制率接近60%。在紫外线与低PAR组合暴露的情况下，圆形石莼的光抑制率最高。
