蓝藻水华在生长和衰亡过程中会产生包括微囊藻毒素在内的多种有毒代谢产物,这些毒素可能会随灌溉用水进入农田而对作物带来不利影响.本研究选用微囊藻毒素-LR(MC-LR)纯品和铜绿微囊藻裂解液分别对营养生长期水稻进行21d 暴露处理,考察不同浓度(0.1,1.0,10.0,100.0,500.0μg/L)MC-LR和不同稀释倍数(0.002,0.02和0.2倍)铜绿微囊藻裂解液对水稻叶绿素荧光强度、净光合速率、蒸腾速率、气孔导度及叶片超微结构的影响.研究结果表明,MC-LR对水稻光合作用特征参数具有显著的抑制作用,其中蒸腾速率和气孔导度对MC-LR 暴露最为敏感,比较来看,考察浓度范围内铜绿微囊藻裂解液对植物光合作用特性指标影响显示出不同的特点,甚至表现出一定刺激和促进作用,0.02倍裂解液暴露显著促进植株蒸腾作用和气孔导度.此外,高浓度的单一 MC-LR 和高浓度铜绿微囊藻裂解液都能对水稻叶片超微结构能造成一定程度的损伤.铜绿微囊藻裂解液和 MC-LR 作用特点不一致,推测是裂解液中其他组分造成微囊藻毒素有效性的改变和毒性的降低.%Microcystins (MCs) and other toxic metabolites, released from cyanobacterial blooms, can be transferred to farmland via irrigation and therefore may have adverse effects on terrestrial crops. In the present study, the net photosynthetic rate, transpiration rate, stomatal conductivity and chlorophyll fluorescence, as well as the ultrastructural features of leaves of rice (Oryza sativa L.) at vegetative stage were investigated under the exposure to a series of concentrations of MC-LR (0.1, 1.0, 10.0, 100.0 and 500.0μg/L) and Microcystis aeruginosa crude extracts (0.002 lysate, 0.02 lysate and 0.2 lysate) for 21days. Results showed that exposure to pure MC-LR can produce significant inhibitory effects on the photosynthetic characteristic parameters of rice, and the transpiration rate and stomatal conductivity are the most sensitive indicators in rice to MC-LR exposure. In contrast, different effect characteristics of photosynthesis parameters, even the stimulating and promoting effects, were found in rice under the exposure to Microcystis aeruginosa crude extracts (e.g. significant induction of the transpiration rate and stomatal conductivity of rice under the exposure to 0.02lysate). In addition, a series of ultrastructural alterations were also found in rice leaves exposed to high levels of the pure MC-LR and Microcystis aeruginosa crude extract. These results suggested that the toxicity mechanism of Microcystis aeruginosa crude extracts to rice is different from pure MC-LR and the decrease of biological toxicity might be due to the changes of MCs bio-availability caused by the interactions with other components co-existed in crude extract solution.
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