海带硫酸多糖对镉毒害甜瓜幼苗的保护作用

以＂二叶一心＂期甜瓜（Cucumis melo L.）为材料,研究了沙培条件下不同浓度（0、0.1、0.25、0.35、0.7、1.1、2.2 g.L^-1）的海带硫酸多糖对150 mg.kg^-1氯化镉（CdCl2.2.5H2O）毒害下甜瓜幼苗的保护作用。结果表明,甜瓜幼苗的镉积累量、叶绿素含量、生物量、蛋白质含量、丙二醛（MDA）含量、膜透性以及抗氧化酶活性均与海带硫酸多糖浓度的变化具有相关性。随灌施海带硫酸多糖浓度的升高,甜瓜叶片和根系中镉积累量和渗透势持续下降,0.25 g.L^-1和0.35 g.L^-1的海带硫酸多糖水平下无显著差异,与其他浓度水平差异显著（P〈0.05）;叶绿素含量、生物量、蛋白质含量、超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）等抗氧化酶活性呈先上升后下降趋势,0.35 g.L^-1海带硫酸多糖水平下含量最高;MDA和膜透性则表现为先下降后上升趋势,且0.35 g.L^-1海带硫酸多糖水平下含量最低。综合来看,当海带硫酸多糖的浓度低于0.35 g.L^-1时,对镉毒害下的甜瓜幼苗有一定保护作用,高于0.35 g.L^-1时,不仅没有缓解镉毒害的作用,反而加重对甜瓜幼苗的伤害。

Protective Effects of Laminaria Polysaccharide Sulfate on the Cadmium Poisoned Melon Seedlings

Laminaria polysaccharide sulfate（LPS）prepared in our laboratory was used to spray＂2-leavies-1-heart＂stage cadmium（Cd） poisoned melon（Cucumis melo L.）seedlings.Protective effects of LPS levels（0、0.1、0.25、0.35、0.7、1.1、2.2 g.L-1）on the cadmium poisoned melon seedlings were studied.The results showed that LPS concentration had certain relations with Cd accumulation,the contents of chloro-phyll,biomass,contents of soluble proteins,content of malonaldehyde（MDA）,membrane permeability,activities of superoxide dismutase（SOD）,peroxidase（POD）and catalase（CAT）in melon seedling leaves and roots.With the LPS concentration increasing,cadmium content and osmotic potential in melon seedling leaves and roots declined continuously.It was no significant difference between 0.25 g.L-1 and 0.35 g.L-1 LPS leve（lP0.05）.Chlorophyll content,biomass accumulation,protein content and the activities of SOD,POD and CAT increased firstly and then decreased.The values were highest at 0.35 g.L-1 LPS level.MDA content and membrane permeability firstly decreased and then went upward,and they reached the lowest values at 0.35 g.L-1 LPS level.In general,less than 0.35 g.L-1 of LPS had some protective effects on the cadmium poisoned melon seedlings,but did some damage to the melon seedlings above 0.35g.L-1 LPS level instead.