Mesotrione, an herbicide increasingly found in aquatic systems due to its increased application frequency in corn fields, is an inhibitor of the p-hydroxyphenylpyruvate dioxygenase (HPPD), a key enzyme for plastoquinone-9, α-tocopherol and indirectly for carotenoid biosynthesis. The direct effect of mesotrione on plastoquinone-9 and α-tocopherol synthesis and their degradation rates are well documented, but few information exists on its action on photosynthetic processes under various light intensities. We therefore investigated the photosynthetic activity, energy dissipation processes, pigment composition and α-tocopherol content when Chlamydomonas reinhardtii were exposed to mesotrione for 24 h under low light condition and then the impacts of HL treatment (75 min) were also investigated. Under low light growth conditions, mesotrione did not induce PSII photoinhihition, while substantially decreased Car:Chl-a ratio, maximal energy-dependant quenching and state 1 to state 2 transition. Under high light conditions (HL), PSII activity was highly decreased in presence of mesotrione, and the non-photochemical energy dissipation processes were drastically affected in these conditions compared to the HL treatment alone. Mesotrinone also prevent the complete recovery of PSII damage caused by HL. Light condition seems therefore to be a non-negligible factor modulating mesotrione toxicity, and this has an obvious importance in agricultural waterbodies where phytoplankton is subjected to fluctuating light intensities.

甲基磺草酮是一种在水生系统中因在玉米田中增加的应用频率而日益广泛发现的除草剂，它是对羟基苯丙酮酸双加氧酶（HPPD）的抑制剂，该酶是质体醌9，α-生育酚的关键酶，间接用于类胡萝卜素的生物合成。甲基磺草酮对质体醌9和α-生育酚合成及其降解速率的直接作用已有很好的文献记载，但是在各种光照强度下其对光合作用过程的作用的信息很少。因此，我们研究了莱茵衣藻时的光合活性，能量耗散过程，色素成分和α-生育酚含量。在弱光条件下将其暴露于甲基磺草酮中24 h，然后还研究了HL处理（75分钟）的影响。在弱光条件下，甲基磺草酮不会诱导PSII光抑制，而Car：Chl- a则显着降低。比率，最大能量依赖淬灭和状态1到状态2的过渡。在高光照条件下（HL），在甲基磺草酮的存在下PSII活性大大降低，并且与单独的HL处理相比，在这些条件下非光化学能量耗散过程受到了极大的影响。Mesotrinone还可以阻止由HL引起的PSII损伤的完全恢复。因此，光照条件似乎是调节甲基磺草酮毒性的不可忽略的因素，这在浮游植物的光照强度波动的农业水体中具有明显的重要性。