The Alleviation Of Exogenous Salicylic Acid (SA) On Lemna Minor Cadmium (Cd) Toxicity

In the present study, alleviation of cadmium toxicity in Lemna minor by exogenous salicylic acid was researched by applying technology of plant physiology and biochemistry,histochemical staining, inductively-coupled plasma atomic emission spectrometry(IPC-MS), high performance liquid chromatography-mass spectrum (HPLC-MS/MS),Native-PAGE, combined with Western-blot technology. The results were as follows:(1) The photosynthetic pigments, proline (Pro), soluble protein, malondialdehyde(MDA), superoxide anion (O2·-) and antioxidant systems (antioxidative enzymes and antioxidants) of L. minor exposed to 10?M Cd and 10 ?M Cd combined with various concentration of SA (0, 25, 50, 75, 100 ?M) for 7 d were analyzed. The results showed that Cd reduced the contents of chlorophyll a (Chi a), chlorophyll b (Chi b), carotenoid (Car),soluble protein, respectly 35%?51 %.12% and 68% lower than the control; improved MDA,O2·- generation rate and proline accumulation, respectly 128%?120% and 168% of the control. At the same time, the antioxidant system was also affected to varying degrees,including decrease in superoxide dismutase (SOD) and peroxidase (GPX) activities. On the contrary, Cd increased small molecular protective substance such as ascorbic acid (AsA),glutathione (GSH) content. When exogenous SA was applied at 25-100 ?M concentration,contens of photosynthetic pigments, soluble protein were increased, MDA, O2·-generation rate and proline accumulation were decreased. The activities of SOD and GPX were increased and the contents of AsA and GSH were decreased. 25-100 ?M SA can alleviate the toxic effect of cadmium on L. minor in varying degrees. The results showed that 50 ?M SA is the best concentration to reduce Cd toxicity in L. minor.(2) The goal of this study was to assess the morphological, physiological and biochemical changes in L. minor upon exposure to 10 ?M Cd,10 ?M Cd plus 50 ?M SA,or 50?M SA for 7 d. Reversing the effects of Cd, SA decreased Cd accumulation in plants,improved accumulation of minerals (Ca, Mg, Fe, B, Mo) absorption, increased endogenous SA concentration, and phenylalanine ammonialyase (PAL) activity. Chlorosis-associated symptoms, the reduction in chlorophyll content, and the overproduction of reactive oxygen species induced by Cd exposure were largely reversed by SA. SA significantly decreased the toxic effects of Cd on the activities of SOD, GPX, CAT, APX and GR in the fronds of L.minor. Furthermore, SA reversed the detrimental effects of Cd on total ascorbate, and glutathione, and on the AsA/DHA and GSH/GSSG ratios, on lipid peroxidation, on MDA concentration, on the activity of LOX, on the accumulation of proline. SA induced the up-regulation of heat shock proteins (Hsp70) and attenuated the adverse effects of Cd on cell viability.