氮限制对硅藻三角褐指藻光系统Ⅱ光化学反应的影响

Effects of nitrogen limitation on photosystem Ⅱ photochemistry reaction in diatom Phaeodactylum tricornutum

本文以硅藻三角褐指藻为实验材料,设置氮充足(882.35μmol·L^(-1))和氮限制(40μmol·L^(-1))两种营养盐供应水平进行培养,以探讨氮限制条件下三角褐指藻光系统Ⅱ(PSII)光化学反应及其对高光强的耐受性变化。结果表明:氮限制抑制三角褐指藻的生长,降低其叶绿素a含量,并加剧其受光抑制程度;通过分析快速叶绿素荧光诱导动力学曲线发现,氮限制使得电子从Q_A^-向QB的传递受阻,且高光强作用后,Q_A^-的瞬时积累进一步增加;此外,氮限制条件下,活性反应中心部分关闭,藻细胞单位反应中心吸收的能量(ABS/RC)、捕获的用于还原Q_A的能量(TRo/RC)以及耗散的能量(DI_o/RC)均明显升高;而高光的耦合作用使得PSII反应中心进一步失活;氮限制影响三角褐指藻PSII光化学反应,进而降低其对高光的耐受能力。

The diatom Phaeodactylum tricornutum was grown in matrixes of nitrogen repletion （882.35 ·mol · L-1） and limitation （40μmol ·L-1） to investigate the effects of nitrogen limitation on photosystem Ⅱ photochemistry reaction and resistance to high light intensity. Results showed that nitrogen limitation reduced the growth rate, decreased the chlorophyll a content, and accelerated the photoinhibition in P. tricornutum. The analyses of the polyphasic rise of fluores- cence transients demonstrated that nitrogen limitation inhibited the electron transfer from QA- to Qs, and high light treatment led to further accumulation of QA-. In addition, under the nitrogen limitation condition, the active reaction centers were closed partially, and the energy fluxes for absorption （ ABS/RC ）, trapping （ TRo/RC ）, and dissipation （ DIo/RC ） per reaction center were increased. The combination of high light treatment and nitrogen limitation resulted in further inactivation of PSII reaction center. Our results indicated that nitrogen limitation could modify the PSⅡ photochemistry, and reduce the resistance of P. tricornutum to high light intensity.