氮限制与UV辐射对假微型海链藻光合特性的耦合效应

Coupling effects of nitrogen limitation and ultraviolet radiation on photosynthetic performance of Thalassiosira pseudonana

分析了不同氮水平下硅藻假微型海链藻(Thalassiosira pseudonana(Hustedt)Hasle et Heimdal CCMP 1335)对UV辐射的光合响应。结果表明:UV辐射显著抑制假微型海链藻PSII的最大光化学效率(F/F),且氮限制加剧该抑制效应;氮限制条件下藻细胞反应中心净关闭速率(M)升高,Q_(A)^(-)向Q的电子传递效率(ψ)下降,对光能的吸收效率(α)下降,从而使得藻细胞对UV辐射的耐受能力降低;UV辐射下,尤其是氮限制时,藻细胞PSII的修复速率与损伤速率(r/k)的比值显著降低,表明UV辐射通过对修复过程的抑制,使得两者耦合对假微型海链藻的光合抑制效应加剧;氮限制与UV辐射的耦合作用显著降低假微型海链藻的光合能力,从而影响其初级生产。

In this study,we examined the photosynthetic response of diatom Thalassiosira pseudonana to UV radiation under different nitrogen concentrations.Results showed that the maximum photochemical yield(F/F)of PSII was significantly inhibited by UV radiation,which was aggravated by nitrogen limitation.Under nitrogen limitation,the net closing rate of the reaction center(M)increased,the electron transfer efficiency fromQ_(A)^(-)to Q(ψ)decreased,the absorption efficiency of light energy(α)was depressed,which together reduced the tolerance of T.pseudonana cells to UV radiation.UV radiation,especially when under nitrogen limitation,significantly decreased the ratio of PSII repair rate to damage rate(r/k),indicating that the photoinhibition of PSII was intensified by UV radiation through the damage of repair process.Our results suggest that the combination of nitrogen limitation and UV radiation could decrease photosynthetic capacity of T.pseudonana,with consequences on the primary production.