| In the present study, the callus of Alternanthera philoxeroides were selected as experimental material, and the two forms heavy metals were used as the stress factors. These callus were cultivated in solution containing different concentrations of Cr3+ and Cr6+ under lab condition. The changes of physiological characteristics, ultrastructure and random amplified polymorphic DNA (RAPD) profiles in the callus of Alternanthera philoxeroides. The results are as follow:(1) The medium of 1/2 MS+6-BA 3 mg·L-1+NAA 0.2 mg·L-1 was the ideal medium for induction of callus. The young items were chosen and cultivated on the medium. The Light culture room temperature was 25℃, keeping them 8 hours in light and 16 hours in darkness every day, light intensity was 1200-15001x.(2) With the increasing of Cr6+①total chlorophyll (Chl), chlorophyll a/b (Chl a/b) and total soluble protein contents showed the same trend, which increased firstly and then decreased.②Superoxide anion(O2-) and hydrogen peroxide(H2O2) content irritably increased compared to the control group, then decreased, however, it always higher than that of control.③The soluble sugar content enhanced with the increasing of Cr6+ concentration.④Activities of supeoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) and ASA and GSH contents all increased first and then decreased.⑤Transmission electron microscope observation indicated that Cr6+ also imposed injury action on ultrastructure of callus cells:thylakoid twisted, chloroplast envelope broke and large starch grain formed, mitochondria disappeared and formed vacuolization, nucleolus lost and chromatin condensed in nucleus, and endoplasmic reticulum vanished by means of vesiculation. The conclusion could be reached that toxic effects of Cr6+ on callus resulted in disorder of physiological and biochemical metabolism and destruction of ultrastructure of callus cells.(3) The callus of Alternanthera philoxeroides exposed to Cr6+(0.1-1.5 mM) were used to evaluate the alterations in superoxide anion (O2-) and total soluble protein content and random amplified polymorphic DNA (RAPD) profiles. A set of 12 random decamer oligonucleotides of 10 bp in length were used as single primers for the amplification of RAPD fragments. The results showed that the increase of superoxide anion and inhibition of total soluble protein content in callus were measured with the increase of Cr6+ concentration, the changes generating in RAPD profiles of the callus following Cr6+ treatment included alteration in band intensity, disappearance of normal bands and appearance of new bands compared with the control.Thus, DNA polymorphism detected by RAPD analysis could be used as a suitable biomarker assay for the detection of genotoxic effects of Cr6+ pollution on Alternanthera philoxeriodes.(4) Changes of H2O2 contents, activities of protective enzymes(CAT, POD, GR, APX and GR), ASA, GSH and Pro contents in the callus of Alternanthera philoxeriodes under different concentration of Cr3+(0,0.1,0.2,0.5,1.5 mmol·L-1). The results showed that:①H2O2 contents increased gradually.②ASA and GSH contents all increased first(0,0.1,0.2,0.5 mmol·L-1) and then decreased.③APX and GR activities enhanced progressively up to 0.5 mmol·L-1 Cr3+ and followed by a decline at the highest dose.④CAT activity increased first and decreased then, while POD activity enhanced with the increasing of Cr3+ concentration.⑤Pro content incresed gradually.⑥Transmission electron microscope observation indicated that Cr3+ also imposed injury action on ultrastructure of callus cells, swelling of chloroplast and breakage of chloroplast envelope, decreasing of quantity and vacuolization of mitochondria, and disruption and vanishing of nucleolus and nucleoplasm flowing into cytoplasm. |
PDF Full Text Request