桢楠幼树光合特性对镉胁迫的响应

Responses of photosynthetic characteristics and chlorophyll fluorescence parameters of Phoebe zhennan saplings to cadmium stress

以3.5 a桢楠(Phoebe zhennan)幼树为试验材料,采用盆栽控制试验,探讨桢楠幼树光合生理在不同浓度镉(Cd)胁迫下的变化情况。试验设置6个Cd(CdCl2)处理水平(0、10、20、30、40、50 mg/kg)。每处理施用量等分为5份,分五次施入,每两月施一次,待处理结束后测定相关指标。(1)随着Cd胁迫程度加重,叶绿素a(Chla)、叶绿素b(Chlb)、类胡萝卜(Car)及叶绿素总量均呈下降趋势,Chla/b逐渐升高;(2)净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(LS)随Cd胁迫加重而显著下降,胞间二氧化碳浓度(Ci)则显著上升;(3)随着Cd胁迫程度的加重,最大净光合速率(Pmax)、光饱和点(LSP)和暗呼吸速率(Rd)均呈下降趋势,光补偿点(LCP)则逐渐上升;(4)初始荧光(F0)、最大荧光(Fm)、实际光量子效率(ΦPSⅡ)、电子传递速率(ETR)、光化学淬灭系数(qP)均随Cd胁迫程度的加重呈下降趋势,非光化学淬灭系数(qN)则逐渐增加,最大光化学效率(Fv/Fm)、PSII潜在活性(Fv/F0)在T1-T4时无显著变化,T5时显著增高;(5)桢楠幼树对剩余光能的耗散均以热耗散途径为主,但随着Cd浓度的增加(T3-T5),会增加桢楠幼树非化学反应能量(Ex)的耗散,减少热耗散能量(D)和光化学反应能量(P)。低浓度Cd(T1-T2)胁迫时,桢楠幼树的光合作用受到严重抑制,随着Cd浓度的进一步增加(T3-T4),叶绿素荧光参数变化显著,桢楠幼树对吸收光能的分配发生明显改变,表明其耐Cd的耐性较弱,因此需注重桢楠幼林造林地的选择,避免在Cd污染严重地区种植。

Using 3.5 a saplings of Phoebe zhennan as experimental materials, the response of photosynthetic physiology and chlorophyll fluorescence parameters of P. zhennan under different concentrations of cadmium(Cd) stress was investigated by pot experiment.A total of 6 Cd(CdCl2) treatment levels(0, 10, 20, 30, 40, 50 mg/kg) were set up, and the application amount of each treatment was divide into 5 equal parts and each part was applied once every two months., the photosynthesis and photosynthetic physiological indicators were measured as soon as the experiment was over.(1) With the aggravation. of Cd stress, the total amount of chlorophyll a(Chl a), chlorophyll b(Chl b), carotenoid(Car) decreased, and Chla/b gradually increased.(2) The net photosynthetic rate(Pn), stomatal conductance(Gs), and transpiration rate(Tr) decreased significantly with the aggravation of stress, while the intercellular carbon dioxide concentration(Ci) increased.(3) With the enhancement of cadmium stress, the light saturation point(LSP) and the dark respiration rate(Rd) all showed a downward trend, and the light compensation point(LCP) gradually increased.(4) Initial fluorescence(F0), maximum fluorescence(Fm), actual photon efficiency(ΦPSII), electron transfer rate The ETR and photochemical quenching coefficient(qP) decreased with the increase of cadmium stress, and the non-photochemical quenching coefficient(qN) increased gradually. As for the maximum photochemical efficiency(Fv/Fm) and PSII potential activity(Fv/F0), there was no significant change at T1-T4, and it was significantly increased at T5.(5) The dissipation of residual light energy of seedlings was mainly based on the pathway of heat dissipation, but with the increment of cadmium concentration(T3-T5), the dissipation of non-chemical reaction energy(Ex) increased, and the heat dissipation energy(D) and photochemical reaction energy(P) decreased. The photosynthesis of P. zhennan saplings were severely inhibited under low concentration of Cd(T1-T2) stress. With the further increase of Ca concentration(T3-T4), the chlorophyll fluorescence parameters changed significantly. The distribution of light energy has changed significantly, indicating that the cadmium tolerance of P. zhennan saplings is weak, so it is necessary to pay attention to the site selection for young plantation of P. zhennan,and in particular, to avoid to plant it in place where cadmium pollution is serious.