The macro- and microalgae have been found to inhibit the growth and photosynthesis of one another due to allelopathic interactions between them. Sargassum fusiformis is a common and commercially cultivated seaweed in coastal waters of the East China Sea (ECS) and usually encounters dense harmful algal blooms (HABs) formed by dinoflagellates during their sexual reproduction period. In the present study, the effects of Prorocentrum donghaiense lipophilic extracted allelochemicals on the growth and photosynthesis of S. fusiformis zygotes were probed by fast chlorophyll fluorescence rise kinetics and chlorophyll a transient analysis (JIP-test). It was found that exposure to the allelochemicals led to decreased chlorophyll a content and photosynthetic rates of the zygotes in comparison to the ones in the control. In addition, using the JIP-test, it was found that the inhibitory effects of allelochemicals on photosynthesis of the zygotes were mainly exerted on the electron transport within PSII. The decrease of photosynthetic parameters such as V_J, Mo, ϕ_Po, ϕ_o, ϕ_Eo, PI, P_TR, P_ET in the zygotes exposed to the allelochemicals all revealed that the obstruction of electron transport, and the dominant decrease in P_ET, both implied that inhibition on the dark reaction contributed to the highest photosynthetic reduction. In addition, some reaction centers (RCs) in the zygotes exposed to the allelocamicals were inactivated, which led to higher dissipation of excitation energy, as demonstrated by the significant enhancement of the photosynthetic parameter DIo/RC. All the results indicated that the lipophilic extracts contained the allelochemicals of P. donghaiense which could inhibit the growth and photosynthesis of S. fusiformis zygotes by damaging the electron acceptors and inactivating RCs, and finally block the electron transport.

已发现大型藻类和微藻类由于它们之间的化感相互作用而抑制彼此的生长和光合作用。梭形马尾藻是东海沿岸水域常见的商业化栽培海藻，通常会在有性繁殖期间遇到由甲藻形成的密集有害藻华（HAB）。在本研究中，通过快速叶绿素荧光上升动力学和叶绿素瞬态分析（JIP-测试）探讨了东海原甲藻亲脂性提取的化感物质对梭形梭菌合子生长和光合作用的影响。结果发现，与对照相比，接触化感物质会导致受精卵的叶绿素a含量和光合速率降低。此外，通过JIP-test发现，化感物质对受精卵光合作用的抑制作用主要体现在PSII内的电子传递上。化感物质作用下受精卵光合参数V _J 、 Mo 、 phi _Po 、 phi _o 、 phi _Eo 、 PI 、 P _TR 、 P _ET等降低，均表明电子传递受阻，P 下降占主导地位。 _ET ，都表明对暗反应的抑制导致最高的光合作用减少。此外，暴露于异体物质的受精卵中的一些反应中心（RC）失活，导致激发能量耗散更高，光合参数 DIo/RC 的显着增强证明了这一点。 结果表明，亲脂性提取物中含有东海松的化感物质，可通过破坏电子受体、灭活RCs来抑制梭形梭菌合子的生长和光合作用，最终阻断电子传递。