氮沉降对镉胁迫下南方四季杨生物量积累和光合生理的影响

Effects of Nitrogen Deposition on Biomass Accumulation and Photosynthetic Physiology in Populus deltoides × P. nigra under Cadmium Stress

为了探讨氮(N)沉降对植物镉(Cd)耐受性的影响,采用盆栽模拟试验,研究了低N(30 kg·hm^(-2)·a^(-1))、中N(60 kg·hm^(-2)·a^(-1))、高N(90 kg·hm^(-2)·a^(-1))3种施氮量处理下,受Cd胁迫(100 mg·kg^(-1))的南方四季杨(Populus deltoides×P.nigra)幼苗生物量积累、气体交换特征、叶绿素荧光参数、叶片绿度(S_(P,A,D))和丙二醛(MDA)质量摩尔浓度、可溶性蛋白质量浓度的差异。结果表明:单独Cd处理显著降低了根、茎、叶生物量的积累。交互作用下,低N和中N处理对各器官生物量积累影响不显著,高N处理显著提高了根、茎、叶生物量的积累。单独Cd显著降低了除胞间二氧化碳摩尔分数之外的所有气体交换参数。交互作用下,低N处理显著升高了幼苗的净光合速率(P_N);中N处理显著提高了幼苗的P_N、气孔导度(G_s)、蒸腾速率(T_r);高N处理对各参数无影响。单独Cd处理显著降低了光系统Ⅱ的实际光量子产量(Φ_(P,S,II))和S_(P,A,D)值,升高了非光化学淬灭系数(q_N)。交互条件下,中N和低N处理提高了S_(P,A,D)值,低N处理降低了q_N,而高N处理对这些参数没有显著影响。单独Cd处理显著升高了叶片的MDA质量摩尔浓度。交互作用下,MDA质量摩尔浓度随着N沉降量的增加先降低后升高,可溶性蛋白质量浓度在Cd和中N处理的交互作用下显著升高。由此可见,N对Cd胁迫的缓解作用与N沉降量和植物自身氮素亏缺状态密切相关。

We investigated the effects of simulated N deposition on growth of Populus deltoides×P.nigra seedlings exposed to cadmium(100 mg·kg^-1).We used a pot experiment,with N deposition levels as 0(Control),30(Low-N),60(Middle-N),and 90 kg·hm^-2·a^-1(High-N),respectively.We measured biomass accumulation,gas exchange characteristics,chlorophyll fluorescence characteristics,leaf greenness indication(SP,A,D)andmalondialdehyde(MDA)molarity,soluble protein content.We found that biomass accumulation of root,stem and leaf were significantly decreased in Cd^2+treatment.In N deposition and Cd^2+combined treatment,there were no significant differences on biomass accumulation among Low-N,Middle-N and Control,but root,stem and leaf biomass in High-N were significantly increased.All gas exchanged parameters except intercellular carbon dioxide(Ci)molarity were decreased in Cd^2+.In the combined treatment,net photosynthetic rate(PN)was significantly increased in Low-N,and PN,stomatal conductance(Gs)and transpiration rate(Tr)were significantly increased in Middle-N,while gas exchange parameters were no changes in High-N.We further found that actual photochemical efficiency(ΦP,S,Ⅱ)and SP,A,D were significantly decreased in Cd^2+treatment.In the combined treatment,SP,A,D was increased in Low-N and Middle-N,and photochemical quenching coefficient(qN)were decreased in Low-N,while these parameters had no changes in High-N.MDA molarity was increased in Cd^2+treatment.In the combined treatment,MDA molarity was decreased at first,then increased with simulated N deposition level increasing.Soluble protein content was increased at combined treatment of Cd^2+and Middle-N.Therefore,the mitigative effect of N deposition to Cd^2+was be closely related to the level of simulated N deposition and plant nitrogen deficiency.