| In this paper, sterile seedlings of Potamogeton crispus L. were cultured by tissue culture technique. Mercury(Hg) was selected as the stress factor. The seedlings were cultivated in solution containing different concentrations of Hg2+under lab condition. The changes of photo system, antioxidase system, and the relationship between Polyamines(PAs) levels and heavy metal stress as well as the mechanisms for the protection of aquatic plants were analyzed. The results are as follow:(1) The hale stems with buds have been proved to be easy to induce bud differentiation in Potamogeton crispus L. The results showed that:with the disinfection of5%hydrogen peroxide15min and10%sodium hypochlorite30second, sterilization consequent was the best, the survival rate was highest, and the microbiological contamination was the lowest. MS medium including6-BA (2.0mg/L) and IBA (0.5mg/L) was the most suitable for the bud differentiation. MS medium including6-BA (0.5mg/L) and IBA (2.0mg/L) was secondary culture medium.10%Hoagland sterile nutrient medium to induce the growth of root, which were cultured in the temperature of25℃, day light16h, light intensity1200～1500lx by the best sterilization methods and hormones.(2) Total chloroplyll content, chloroplyll autofluorescence and chloroplasts ultrastructure, the ATPase activity and mineral nutrition adsorption were analyzed under Hg2+stress. The results revealed that with increasing of Hg2+concentration, the intensity of chloroplyll autofluorescence and chlorophyll decreased gradually. Grana and stroma thylakoids of chloroplast were swollen. The Ca2+Mg2+-ATPase activity increased in5μmol/L Hg2+and then followed by a decline in the present of higher concentration of Hg2+. Both Na/K and Na+K+-ATPase decreased with the rise of Hg2+concentration. The absorbtion of Na, K, Ca, Mg was affected under Hg2+stress. It was concluded that photo system and normal physiological metabolism were disordered.(3) Using physiological and biochemical approaches we analysed the changes of reactive oxygen species (ROS), various antioxidant enzymes, the contents of low molecular antioxidant compound, and soluble protein. It was found herein that the accumulation of Hg both enhanced the generation rate of superoxide anion (O2·-) and the superoxide (SOD) activity. The peroxidase (POD) activity and soluble protein content gradually declined. The contents of ascobate (AsA) and reduced glutathione (GSH) decreased initially and then increased. However, aninitial rise in CAT activity was followed by subsequent decline. The study suggested that antioxidant enzymes, low molecular antioxidant compound could play a significant role in the adaptation mechanism of P.crispus sterile seedlings under Hg stress.(4) The toxic effect of various concentrations of Hg2+(0,5,10,15,20μmol/L) was studied on the contents of PAs, the activities of polyamine oxidase (PAO) and diamine oxidase (DAO), the activities of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), as well as the uptake of nutrient elements changes Potamogeton crispus. sterile seedlings. The results showed that Meantime, aninitial rise in Na, K, Zn content was followed by subsequent decline, and other elements contents gradually declined. Hg stress increased contents of free Put and Spd in lower contamination, and then decreased. Free Spm content and f(spd+spm)/fPut were gradually deccreased. Conjugated-Put and Spd had the same changes with free Put. Conjugated-Spm and Total Spm contents both increased.PS-bound PAs and Total-Spdchanged in the same with pattern as free PAs. In addition, the activity of ODC was increased, while that of, DAO and ADC was increased in lower contamination,and then decreased with the increase Hg concentration,with is different with PAO activity. |
PDF Full Text Request