东海原甲藻对羊栖菜合子生长及光合活性的化感作用研究

ALLELOPATHIC EFFECTS OF PROROCENTRUM DONGHAIENSE ON GROWTH AND PHOTOSYNTHESIS OF SARGASSUM FUSIFORMIS ZYGOTES

为评估东海原甲藻(Prorocentrum donghaiense)赤潮发生对羊栖菜(Sargassum fusiformis)幼苗产量的影响并探讨其化感机理,在实验室条件下分别利用浓度为1.00×10^(5)cells/mL东海原甲藻活细胞悬浮液(LC)、细胞破碎液(RC)和无细胞滤液(FC)培养羊栖菜合子,并对其生长发育及光合活性进行测定。结果显示,LC、RC和FC均会抑制羊栖菜合子的生长、叶绿素a合成和光合活性,其中FC及LC对合子的抑制程度相似且均大于RC。JIP-test分析表明,FC及LC对合子的最大量子产率(φP_(o))、性能指数(PI)及PSⅡ反应中心密度(RCs/ABS)的抑制作用显著大于RC。表明东海原甲藻主要通过向细胞外释放化感物质产生抑制作用,这些化感物质抑制了羊栖菜合子PSⅡ的电子传递,使PSⅡ部分光化学反应中心(RCs)失活,进而使大量激发能转化为热能被耗散掉。而RC中可能含有某些能够刺激羊栖菜合子生长的物质,从而在一定程度上抵消了化感物质的抑制作用。结果表明东海原甲藻对羊栖菜合子的抑制作用主要是由化感物质引起的,东海原甲藻赤潮可以抑制羊栖菜合子的发育和光合活性,减少羊栖菜种苗产量,并最终阻碍了羊栖菜产业的发展。

Dinoflagellate Prorocentrum donghaiense is the most dominate harmful algal bloom(HAB)forming species in the coastal zones of East China Sea,according to the China Marine Environmental Quality Bulletin over the years,which has caused a huge damage to local aquatic systems and brought disaster to the aquaculture industry.In addition,blooms formed by P.donghaiense occur frequently in May every year,coincide with the sexual reproduction period of Sargassum fusiformis.Small-to medium-sized HABs have been occasionally observed to invade into the aquaculture area S.fusiformis.To evaluate the effects of HABs formed by dinoflagellate P.donghaiense on S.fusiformis and ex-plore its mechanism,zygotes of S.fusiformis were cultivated with living cell suspension(LC),ruptured cell suspension(RC)and cell-free supernatant(FC)of 1.00×10^(5)cell/mL P.donghaiense to measure growth rate and photosynthetic activities according to changes in sizes and chlorophyll(Chl.)a fluorescence transient(i.e.,OJIP)of the zygotes.The results showed that LC,RC and FC of P.donghaiense at 1.00×10^(5)cell/mL all significantly inhibited the development,growth,Chl.a contents,apparent photosynthetic efficiency(α),and the maximal electron transport rate(rETRmax)of the zygotes with greater inhibition by FC and LC.For other important photosynthetic parameters of the zygotes ob-tained through JIP-test analysis,FC and LC also greater reduced the maximum quantum yield(φpo),the performance index(PI),and the active reaction center density than RC.It indicated that the decrease in photosynthetic activities of the zygotes was caused by the allelocamicals released by P.donghaiense,and some reaction centers(RCs)in the zy-gotes exposed to the allelocamicals were inactivated,which led to higher dissipation of excitation energy.RC of P.donghaiense contained more allelochemicals than LC and FC because they were released into the media during cells lysis.Therefore,some other compounds that can stimulate the growth and photosynthetic activities of the zygotes were synchronously released,which partly offset the inhibitory effects of the allelopathic substances.These results indicate that the inhibitory effects of P.donghaiense on S.fusiformis zygotes were mainly caused by allelochemicals,and the blooms formed by P.donghaiense can restrain the development and photosynthetic activities of S.fusiformis zygotes,reduce the seedlings stock,and eventually hinder the development of S.fusiformis production industry.