环境浓度微囊藻毒素-LR对菖蒲无机氮吸收特性的影响

Effects of Microcystin-LR at Environmental Concentrations on Inorganic Nitrogen Uptake Characteristics of Acorus calamus L.

富营养化水体中存在的微囊藻毒素(microcystins,MCs)会对水生植物的营养吸收产生潜在威胁。为探讨MCs对水生植物无机氮吸收的影响,分析不同浓度微囊藻毒素-LR(MC-LR)暴露15 d后挺水植物菖蒲对无机氮的吸收特性及其动力学特征。结果表明,0.001 mg·L^(-1) MC-LR暴露条件下,菖蒲根系活力、根系生物量及细胞质膜(PM)H+-ATP酶活性均显著增加,MC-LR暴露对菖蒲的NO-3-N和NH+4-N吸收均有促进作用;0.01 mg·L^(-1) MC-LR暴露条件下,菖蒲根系活力、根系生物量及PM H+-ATP酶活性均有一定程度上升,菖蒲对NO-3-N的亲和力和吸收潜能下降,但对NH+4-N的吸收速率上升;0.03 mg·L^(-1) MC-LR暴露条件下,菖蒲根系活力、根系生物量及PM H+-ATP酶活性均显著下降,MC-LR暴露通过降低菖蒲对NO-3-N和NH+4-N的亲和力和吸收潜能来抑制其对无机氮的吸收。与NH+4-N相比,0.03 mg·L^(-1) MC-LR对NO-3-N吸收的抑制作用更强。MC-LR(0.001~0.01 mg·L^(-1))暴露对菖蒲NH+4-N吸收有不同程度的促进作用,而0.03 mg·L^(-1) MC-LR暴露对菖蒲的NH+4-N和NO-3-N吸收均产生明显抑制,对菖蒲生长及其氮的去除能力产生不利影响。

Microcystins(MCs)in eutrophic water may pose a potential threat to nutrient uptake of aquatic plants.To investigate the effects of MCs on inorganic nitrogen uptake by aquatic plants,the uptake characteristics and kinetics of inorganic nitrogen in Acorus calamus L.after exposure to different concentrations of microcystin-leucine-arginine(MC-LR)for 15 d were analyzed.The results showed that when exposed to 0.001 mg·L^(-1) MC-LR,the root activity,root biomass and plasma membrane(PM)H+-ATPase activity of A.calamus L.increased significantly,and the exposure to MC-LR had an stimulating effect on the uptake of both NO-3-N and NH+4-N.When exposed to 0.01 mg·L^(-1) MC-LR,the root activity,root biomass and PM H+-ATPase activity increased to a certain extent.The exposure to MC-LR decreased the affinity and uptake potential for NO-3-N,but increased NH+4-N uptake rate.When exposed to 0.03 mg·L^(-1) MC-LR,the root activity,root biomass and PM H+-ATPase activity of A.calamus L.decreased significantly.The exposure to 0.03 mg·L^(-1) MC-LR inhibited inorganic nitrogen uptake by decreasing the affinity and uptake potential for NO-3-N and NH+4-N,which also enhanced the inhibitory effect of MC-LR on NO-3-N uptake when compared with that of NH+4-N uptake.Therefore,exposure to MC-LR(0.001~0.01 mg·L^(-1))promoted NH+4-N uptake by A.calamus L.to a varying degree.However,exposure to 0.03 mg·L^(-1) MC-LR significantly inhibited NH+4-N and NO-3-N uptake by A.calamus L.,which adversely affected the growth and nitrogen removal ability of A.calamus L..