Most photosynthetic organisms are sensitive to very high light, although acclimation mechanisms enable them to deal with exposure to strong light up to a point. Here we show that cultures of wild-type Chlamydomonas reinhardtii strain cc124, when exposed to photosynthetic photon flux density 3000 μmol m⁻² s⁻¹ for a couple of days, are able to suddenly attain the ability to grow and thrive. We compared the phenotypes of control cells and cells acclimated to this extreme light (EL). The results suggest that genetic or epigenetic variation, developing during maintenance of the population in moderate light, contributes to the acclimation capability. EL acclimation was associated with a high carotenoid-to-chlorophyll ratio and slowed down PSII charge recombination reactions, probably by affecting the pre-exponential Arrhenius factor of the rate constant. In agreement with these findings, EL acclimated cells showed only one tenth of the ¹O₂ level of control cells. In spite of low ¹O₂ levels, the rate of the damaging reaction of PSII photoinhibition was similar in EL acclimated and control cells. Furthermore, EL acclimation was associated with slow PSII electron transfer to artificial quinone acceptors. The data show that ability to grow and thrive in extremely strong light is not restricted to photoinhibition-resistant organisms such as Chlorella ohadii or to high-light tolerant mutants, but a wild-type strain of a common model microalga has this ability as well.

大多数光合生物对非常高的光很敏感，尽管适应机制使它们能够在一定程度上应对强光照射。在这里，我们展示了当暴露于光合光子通量密度 3000 μmol m ^-2  s ^-1时，野生型莱茵衣藻菌株cc124 的培养物几天，能够突然获得成长和茁壮成长的能力。我们比较了对照细胞和适应这种极光 (EL) 的细胞的表型。结果表明，在中等光照下维持种群期间发生的遗传或表观遗传变异有助于适应能力。EL 驯化与高类胡萝卜素与叶绿素的比率有关，并减慢了 PSII 电荷重组反应，这可能是通过影响速率常数的指数前阿伦尼乌斯因子。与这些发现一致，EL 驯化细胞仅显示对照细胞的¹ O ₂水平的十分之一。尽管低¹ O ₂在 EL 驯化细胞和对照细胞中，PSII 光抑制的破坏反应速率相似。此外，EL 适应与缓慢的 PSII 电子转移到人工醌受体有关。数据表明，在极强光下生长和茁壮成长的能力不仅限于抗光抑制生物，如Chlorella ohadii或耐高光突变体，但常见模型微藻的野生型菌株也具有这种能力。