Acclimation of photosynthetic properties in ice algae

尽管这些环境非常恶劣，但冰藻和硅藻仍能进行高效的光合作用。我们研究了它们的光收集系统或光系统如何适应非常低的辐照度以实现有效的光合作用。它的驯化方式非常独特，与高等植物或绿藻的驯化方式相反。在较低的辐照下，冰藻的辅助色素和RubisCO减少，光系统I （PSI）与PS II的比值降低。高度适应极低辐照的光合系统受到功能二氧黄质循环（相当于高等植物的叶黄素循环）的保护，以抵御较高的辐照。最大光合速率也保持在同一水平，在-800 uEm-2s-1的光照条件下不存在光抑制现象。这些特性可能表明硅藻细胞在相对于其产生时间的短时间尺度辐照度变化较大的情况下，如在冰中，其光系统的高效光能利用和功能。

Ice algae and diatoms perform highly efficient photosynthesis, in spite of these very severe environments. We investigated how their light-harvesting systems or photosystems acclimate to very low irradiance to achieve efficient photosynthesis. The way of acclimation was very unique, which was opposite to that of higher plants or green algae. In ice algae, the accessory pigments and also RubisCO were decreased and the ratio of photosystem I (PSI) to PS II was lowered in lower irradiance. And photosynthetic systems acclimated highly to very low irradiance were protected by functional diadinoxanthin cycle, equivalent to the xanthophylls cycle of higher plant, against higher irradiance.The maximum photosysthetic rate was also retained at the same level and photo inhibition could not be observed under illumination up to -800 uEm-2s-1. These properties may indicate that the efficient light-energy utilization and functioning of photosystems of the diatom cells under large variation of irradiance at short time-scale relative to their generation time such as in the ice.