| In this paper,mangrove Avicennia marina hypocotyls were cultivated in sand with 15‰seawater.Some were treated with Cr(Ⅲ) once planted,and some were treated when growing 6 months.The influence of increasing concentrations of Cr (Ⅲ)(0,100,200,300,400,500,600,800 mg·L-1) on hypocotyls germination and growth,photosynethesis metabolism,water metabolism,salt contents and membrance protection system were observed to inquire into the ecophysiological responses of mangrove A.gymnorrhiza to Cr phytotoxicity.The results showed:1.The germination of A.marina seedlings was not obviously influenced by Cr (Ⅲ) pollution during the early germination period.But with the stress time extending and the stress concentrations increasing,the shooting rate and the survival rate were restrained.2.The number of roots was not influenced remarkable by Cr(Ⅲ) whenever stressed 45 days or 150 days,and there were negative effects on the length of roots, the height of stems,the size of leaves and the biomass.3.When hypocotyls were stressed(45 days or 150 days),Cr(Ⅲ) had effect on the water content of some parts,especially that of leaves dropped obviously.4.When hypocotyls were stressed 45 days or 150 days,the contents of chlorophyll a,chlorophyll b,and total chlorophyll of leaves were higher than CK; Treated 45 days when seedlings growthing 6 months,the contents were below CK remarkably.5.The content of soluble protein in roots and leaves were above CK whenever 45 days or 150 days hypocotyls treated;Stressed 45 days when seedlings growthing 6 months,the content of leaves climbed with the increasing of Cr(Ⅲ) concentration, and that in roots was changed unconspicuously.6.When hypocotyls were stressed 45 days,the SOD activity of roots and leaves all presented rose,when stress time reached 150 days,the SOD activity of roots was below CK,but that of leaves showed the dropped first and then rosing;Stressed 45 days when seedlings growthing 6 months,SOD in roots rose slowly,and the activity in leaves decreased above 600 mg·L-1Cr(Ⅲ).7.When hypocotyls were stressed(45 days or 150 days),the POD activity of roots and leaves all rising with the Cr(Ⅲ) concentration increasing;Stressed 45 days when seedlings growthing 6 months,the activity of roots was decreasing gradually and that of leaves was opposite.8.When hypocotyls were stressed(45 days or 150 days),the CAT activity of roots rose but the activity of leaves was decreasing with the Cr(Ⅲ) concentration increasing;Stressed 45 days when seedlings growthing 6 months,the change of CAT of roots was not clear,and CAT activity in leaves reached the peak at 100mg·L-1Cr (Ⅲ) concentration,and then dropped.9.The content of AsA in roots and leaves was rising whenever stressed 45 days or 150 days;Stressed 45 days when seedlings growthing 6 months,the content of AsA in roots was lower than CK,but the content of AsA in leaves was not influenced obviously.10.The effect of Cr(Ⅲ) on the MDA concentration in the roots and leaves was not abvious.11.When hypocotyls were stressed 45 days,the C1 contents of hypocotyls,stems and leaves were decreased with increasing Cr(Ⅲ) concentrations,otherwise the C1 content of roots rose first and then dropped,with the stress time prolonged to 150 days,the C1 contents of each part all rose first and then dropped;Stressed 45 days when seedlings growthing 6 months,the contents were not changed obviously.12.The tendency of Cr absorption in each parts of A.marina seedlings rose first and then dropped,and the content of Cr in roots was the highest.13.The rate of excreting salt on leaves was increasing with the Cr(Ⅲ) concentration rising.
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