| In this paper,Avicennia marina seedlings were treated with various contents of Cd(0.5,5,25,50,100,150 mg/L),various contents of Nap(5,10,20 mg/L),and co-contamination of Cd(25.150 mg/L )and Nap(10 mg/L).These seedlings were cultivated by 15‰man-made seawater in sand for 90 days in a greenhouse.The sprouting and survival rate,the growth of seedlings were recorded.Biomass,water content,chlorophyll content,soluble protein,MDA and ASA content,POD and SOD activity,element contents(Cd,K,Na,Mg) were observed when 45 days and 90 day inorder to inquire into the ecophysiological responses of mangrove Avicennia marina to Cd,Nap and co-contamination.The results were as follow:(1) The languishment of Avicennia marina seedlings cotyledons were accelerated, under 5～150 mg/L Cd treatment,with the leaf size and the biomass decreased.The scatheless concentration of Cd was below 25 mg/L.Under 25～150 mg/L Cd treatment, it showed poisonous speckles on the leaves,and the height of stems were obviously reduced.The seedlings were dead under 50～150 mg/L Cd treatment.(2) In 45 days,the content of soluble protein,the activity of SOD and POD in roots were obviously increased under 5～150 mg/L Cd treatment.In 90 days,the content of ASA in roots was obviously increased while MDA content was decreased under 0.5～150 mg/L Cd treatment.The activity of POD in roots was increased under 25～100 mg/L Cd treatment.The content of soluble protein in roots was increased under 50～100 mg/L Cd treatment.All in all,the content of soluble protein,the activity of SOD,POD were increased under Cd treatments.But as the time went on,the stimulation reduced.(3) In 45 days,the content of soluble protein and the activity of POD in leaves were obviously increased under 0.5～25 mg/L Cd treatment,while decreased under 25～150 mg/L Cd treatment.The activity of SOD showed the opposite trend.In 90 days,the content of protein in leaves showed almost the same trend as 45 days.The activity of POD and the content of ASA in leaves were increased under 0.5～50 mg/L Cd treatment,and the activity of SOD increased under 5～50 mg/L Cd treatment.(4) The content of chlorophyll was reduced under Cd pollution,and the restriction was intensified as the contents increasing and time passing.In 90 days,the content of chlorophyll was obviously under 25～100 mg/L Cd treatment,and especially the content of Chl b.(5) The content of Cd was highest in roots,and 50%of Cd in the seedlings were cumulated in roots.Cd was cumulated in the cotyledons,and may taken away from seedlings by the languishment of cotyledon.The Avicennia marina seedlings may also excreted overmuch Cd by saltglands.(6) The contents of Na and Mg in leaves were reduced as the Cd concentrations increasing.In 90 days,the absorption of K in roots was obviously restrained under 5～100 mg/L Cd treatment.The absorption of Na in roots was obviously enhanced under 25～100 mg/L Cd treatment.(7) The leaf size,biomass,water content of Avicennia marina seedlings showed no significant difference between CK group and group under 5～20 mg/L Nap treatment.(8) In 45 days,the content of soluble protein,the activity of SOD and POD in roots and the activity of POD in leaves were obviously increased under 5～20 mg/L Nap treatment.In 90 days,the contents of MDA and ASA were increased under 5～20 mg/L Nap treatment while the content of soluble protein,the activity of SOD and POD in roots decrease.In 45 and 90 days,the content of Chlb was obviously decreased under Nap treatment.(9) In 90 days,the contents of Na,K,Mg in cotyledons were obviously increased under 10～20 mg/L Nap treatment,while the content of K in the neonatal leaves was decreased under 5～20 mg/L Nap treatment.(10)10 mg/L Nap enhance the Cd cumulation abilities of Avicennia marina organs except cotyledon in the group under co-contamination of 150 mg/L Cd.(11) The addition of 10 mg/L Nap aggravated the injury of 25 mg/L Cd to leaves, while lightened the injury of 150 mg/L Cd.The inhibition of Cd to the height of stems and the length of roots was aggravated by 10 mg/L Nap,and the cooperation was enhanced as the Cd concentration increasing and the time passing.10 mg/L Nap showed antagonism in the reduction of Cd on the biomass,and slowed the languishment of cotyledons.In 45 days,the content of chlorophyll was influenced more by 10 mg/L Nap.(12) Compared to the groups with single Cd treaments.the content of soluble protein,the activity of POD and SOD in leaves and roots enhanced by 10 mg/L Nap. But the effect of 10 mg/L Nap on the activity of SOD in leaves reduced as the Cd concentration increase and the time passed. |
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