Sobrino Cristina, Neale Patrick J, Lubián Luis M
Instituto de Ciencias Marinas de Andalucía (CSIC), Puerto Real, Cádiz, Spain.
Photochem Photobiol. 2005 Mar-Apr;81(2):384-93. doi: 10.1562/2004-08-27-RA-295.
The effect of ultraviolet radiation (UVR) on inhibition of photosynthesis was studied in two species of marine picoplankton with different carbon concentration mechanisms: Nannochloropsis gaditana Lubian possesses a bicarbonate uptake system and Nannochloris atomus Butcher a CO2 active transport system. Biological weighting functions (BWFs) for inhibition of photosynthesis by UVR and photosynthesis vs irradiance (PI) curves for photosynthetically active radiation (PAR) were estimated for both species grown with an enriched CO2 supply (high dissolved inorganic carbon [DIC]: 1% CO2 in air) and in atmospheric CO2 levels (low DIC: 0.03% CO2). The response to UVR and PAR exposures was different in each species depending on the DIC treatment. Under PAR exposure, rates of maximum photosynthesis were similar between treatments in N. gaditana. However, the cultures growing in high DIC had lower sensitivity to UVR than the low DIC cultures. In contrast, N. atomus had higher rates of photosynthesis under PAR exposure with high DIC, but the BWFs were not significantly different between treatments. The results suggest that one or more processes in N. gaditana associated with HCO3- transport are target(s) for UV photodamage because there was relatively less UV inhibition of the high DIC-grown cultures in which inorganic carbon fixation is supplied by passive CO2 diffusion. Time courses of photochemical efficiency in PAR, during UV exposure and during subsequent recovery in PAR, were determined using a pulse amplitude modulated fluorometer. The results were consistent with the BWFs. In all time courses, a steady state was obtained after an initial decrease, consistent with a dynamic balance between damage and repair as found for other phytoplankton. However, the relationship of response to exposure showed a steep decline in activity that is consistent with a constant rate of repair. A novel feature of a model developed from a constant repair rate is an explicit threshold for photosynthetic response to UV.
研究了紫外线辐射（UVR）对两种具有不同碳浓缩机制的海洋微微型浮游生物光合作用抑制的影响：盐生微绿球藻（Nannochloropsis gaditana Lubian）具有一个碳酸氢根摄取系统，而扁圆微绿球藻（Nannochloris atomus Butcher）具有一个二氧化碳主动运输系统。对在高二氧化碳供应（高溶解无机碳[DIC]：空气中1%二氧化碳）和大气二氧化碳水平（低DIC：0.03%二氧化碳）下生长的这两个物种，均估算了UVR抑制光合作用的生物加权函数（BWFs）以及光合有效辐射（PAR）的光合作用与辐照度（PI）曲线。每个物种对UVR和PAR暴露的响应因DIC处理而异。在PAR暴露下，盐生微绿球藻各处理间的最大光合速率相似。然而，在高DIC中生长的培养物对UVR的敏感性低于低DIC培养物。相比之下，扁圆微绿球藻在高DIC的PAR暴露下具有更高的光合速率，但各处理间的BWFs没有显著差异。结果表明，盐生微绿球藻中与HCO3-运输相关的一个或多个过程是UV光损伤的靶点，因为在通过被动二氧化碳扩散提供无机碳固定的高DIC生长的培养物中，UV抑制相对较少。使用脉冲幅度调制荧光计测定了PAR下、UV暴露期间以及随后PAR恢复期间的光化学效率时间进程。结果与BWFs一致。在所有时间进程中，初始下降后获得了一个稳定状态，这与其他浮游植物中发现的损伤和修复之间的动态平衡一致。然而，暴露响应关系显示活性急剧下降，这与恒定的修复速率一致。从恒定修复速率开发的模型的一个新特点是光合作用对UV响应的明确阈值。
