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首页> 外文期刊>Journal of Experimental Marine Biology and Ecology >Effect of enhanced UV-B radiation on photosynthetic characteristics of marine microalgae Dunaliella salina (Chlorophyta, Chlorophyceae)
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Effect of enhanced UV-B radiation on photosynthetic characteristics of marine microalgae Dunaliella salina (Chlorophyta, Chlorophyceae)

机译：UV-B辐射增强对海洋微藻盐藻盐藻（Chlorophyta，Chlorophyceae）光合特性的影响

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Ultraviolet B radiation (UV-B, 280-320 nm) is a natural stress factor that has the potential to negatively affect phytoplankton organisms. In the present study, the model marine microalga Dunaliella salina was exposed to UV-B enhancement (0.25-1.00 kJ m(-2) d(-1)), and its photosynthetic processes, including light and carbon reactions, were analyzed. This study aimed to elucidate what occurs during microalgal photosynthesis under UV-B stress. The results revealed (1) the contents of both chlorophyll and carotenoids. The ratio between these was altered significantly with UV-B enhancement, particularly in the initial phase of exposure, and the ratios of chlorophyll a to b were markedly changed compared with the control. The results indicated that UV-B enhancement could interfere with the light absorption of D. salina, but the results suggest a well-developed strategy depending on the adjustment of photosynthetic pigment to cope with the stress. The damage to the chloroplast ultrastructure was analyzed by transmission electron microscopy. Their shape was irregular, and the lamellae thylakoids were fractured. The grana were disintegrated in the treated groups, and the extent of the damage increased with UVB enhancement. (2) The chlorophyll fluorescence parameters indicated that the maximal photochemical efficiency of PSII (F-v/F-m), the actual photochemical efficiency of PSII in the light (Phi PSII), the relative electron transport rate (rETR) and the photochemical quenching (qP) displayed few changes after initial exposure but were significantly decreased 48 h after UV-B enhancement compared with the control. The results indicate that UV-B stress can decrease the light energy utilization of photosystem II and thus damage the photosynthetic capacity in light reaction. (3) The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which is the key carbon fixation enzyme, was observed to increase significantly in the treated groups compared with the control. This finding indicates that microalga have an adaptive mechanism to moderate UV-B radiation. The results of the present study suggest an alteration in energy distribution after exposure to different doses of UV-B radiation. Non-photochemical quenching may be the main pathway for the dissipation of excessive light energy in photosystem II exposed to low doses, whereas an improved photochemical quenching capacity may play an essential role in avoiding photoinhibition when exposed to higher doses. It appears that there is a dynamic balance between damage and adaptation in microalga that aids their coping with UV-B-induced alterations to the photosystem. (C) 2015 Elsevier B.V. All rights reserved.
机译：紫外线B辐射（UV-B，280-320 nm）是一种自然胁迫因子，可能会对浮游植物产生负面影响。在本研究中，模型海洋微藻杜氏盐藻暴露于UV-B增强（0.25-1.00 kJ m（-2）d（-1）），并分析了其光合作用过程，包括光和碳反应。这项研究旨在阐明在UV-B胁迫下微藻光合作用过程中发生的情况。结果表明（1）叶绿素和类胡萝卜素的含量。它们之间的比率随着UV-B的增强而发生了显着变化，尤其是在暴露的初始阶段，并且叶绿素a与b的比率与对照组相比发生了显着变化。结果表明，UV-B增强可能会干扰盐衣藻的光吸收，但结果表明，根据光合色素的调节来应对压力，这是一种完善的策略。通过透射电子显微镜分析对叶绿体超微结构的损害。它们的形状是不规则的，并且薄片类囊体断裂。谷物在治疗组中崩解，损伤程度随UVB增强而增加。 （2）叶绿素荧光参数表明PSII的最大光化学效率（Fv / Fm），PSII在光中的实际光化学效率（Phi PSII），相对电子传输速率（rETR）和光化学猝灭（qP）与对照相比，初次暴露后显示很少的变化，但在UV-B增强后48小时显着下降。结果表明，UV-B胁迫会降低光系统II的光能利用率，从而损害光反应中的光合能力。 （3）观察到作为关键碳固定酶的核糖-1，5-双磷酸羧化酶/加氧酶（Rubisco）的活性与对照组相比显着增加。这一发现表明微藻具有适度的机制来缓和UV-B辐射。本研究的结果表明，暴露于不同剂量的UV-B辐射后能量分布发生了变化。在暴露于低剂量的光系统II中，非光化学猝灭可能是消散过多光能的主要途径，而暴露于高剂量时，提高的光化学猝灭能力可能在避免光抑制中起重要作用。似乎在微藻的损害与适应之间存在动态平衡，这有助于它们应对UV-B引起的光系统变化。 （C）2015 Elsevier B.V.保留所有权利。

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