| In this paper,the soil-cultivated Kandelia candel(L.) Druce seedlings were treated with co-contamination of Cd(0,2.5,50 mg·kg-1)and Zn(0,100,500 mg·kg-1). Hypocoyl growth,water content,chlorophyll content,soluble protein,soluble sugar, proline,organic acid and mineral contents were observed to inquire into the ecophysiological responses of mangrove Kandelia candel to Zn,Cd co-contamination. The results were as follow:1 Under the same Zn treatments,the root biomass of Kandelia candel seedlings was reduced with Cd treatments,and the reduction was aggravated after longer time. The number of roots was decreased with the increasing Cd and Zn contents.Under 0 and 100 mg·kg-1 Zn concentration,the length of roots was promoted with Cd concentrations,but the stimulation was decreased after 140 days;under 500 mg·kg-1 Zn concentration,Cd treatments restrained the length of roots,and as the time went on, the reduction was aggravated.With the same Cd concentration,the root biomass showed differences with Zn treatments.Under 0 and 2.5 mg·kg-1 Cd concentration, the length of roots was promoted with Zn contents,while restrained under 50 mg·kg-1 Cd concentration.2 The overground biomasses(leaf,stem,hypocotyl) showed differences in different time,organ,and concentration of Zn-Cd treatments.Higher Cd and higher Zn concentration showed cooperative decrease.3 In the beginning of cultivation,Zn treatments decreased the reduction of the high growth of stems by Cd treatments.When the time went on,the high growth was restrained with the increasing Cd contents,and higher Cd and higher Zn concentration showed cooperation.4 The water content in roots was highest among the organs.The water content of Kandelia candel was decreased as the time went on.Under 0 mg·kg-1 Zn concentration,the water content in roots was reduced while the water in overground organs was increased with the increasing Cd concentrations.Under 100 mg·kg-1 Zn concentration,Zn treatments decreased the reduction of the water content by Cd treatments.Under 500 mg·kg-1 Zn concentration,the water content was decreased with Cd treatments.The water content in overground organs was decreased under higher Zn concentration.Higher Cd and higher Zn concentration also showed cooperative decrease.5 In 80 days,the area of leaves was increased with the Cd,Zn treatments, especially with lower Cd concentration.After 140 days,the stimulation reduced.6 Under the same Zn treatments,the synthesis of chlorophylls was increased with lower Cd concentration,while decreased with higher Cd concentration.Under the same Cd treatments,the content of chlorophyll was increased with the Zn concentrations.When the time went on,the content of chlorophylls and the ratio of Chl a/b decreased.7 The interaction effet of Cd-Zn combined stress on the content of soluble protein was mainly mutual.As the time went on,the content of soluble protein decreased.8 Under the same Zn treatments,lower Cd concentration increased the content of soluble sugar in leaves.Under 0 mg·kg-1 Zn concentration,the content of soluble sugar was also increased with the increasing Cd concentrations.The content of soluble sugar decreased with the addition of Cd while Zn concentration was 100 and 500 mg·kg-1.As the time went on,the content of soluble sugar decreased.9 In the beginning of cultivation,the content of proline decreased with the addition of lower Cd while Zn concentration was 0 and 100 mg·kg-1.Cd concentration increased the content while Zn concentration was 500 mg·kg-1.Under the same Cd treatments,Zn concentration decreased the content of proline.As the time went on, the content of proline decreased;separate Cd,Zn treatment increased the content, especially the higher concentration.10 In 80 days,the content of organic acid in leaves was increased with the increasing Cd concentrations.After 140 days,the content of organic acid was basically increased with the addition of Cd.It showed cooperation at high level of combined stress.As the time passed,the content of organic acid increased. 11 The content of Cl in every organ ranked as follow:root＞leaf＞hypocotyle＞stem.Under the same Zn treatments,lower Cd concentration showed stimulation in Cl content.Under the same Cd treatments,lower Zn increased while higher Zn decreased the content of Cl in overground organs.Higher Cd and higher Zn combined stress on the content of Cl was as mutual restriction.12 The content of Na in every organ ranked as follow:root＞leaf,stem＞hypocotyle.Cd treatments decreased the content of Na in roots,but increased the content in overground organs.Higer Zn concentration decreased the content of Na in every organ.The content of K ranked as:hypocotyle＞leaf,stem＞root.The Cd concentrations stimulated the transportation of K from roots to stems and leaves, especially under higher Cd concentration.The content of Mg ranked as:root＞leaf, stem＞hypocotyle.Cd treatments decreased the Mg content in roots,but lowed Cd concentration increased the content in overground organs.The content in roots and hypocotyles decreased with the addition of Zn,while the content in stems and leaves increased.The content of Ca ranked as:leaf＞stem,hypocotyle＞root.The content of Ca decreased with the addition of Zn,Cd concentrations.
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