Effects Of Exogenous Nitirc Oxide And Salicylic Acid On Physiological Characteristics Of Ryegrass Under Copper, Lead And Cadmium Stress

Perennial ryegrass （Lolium perenne L）, a plant of Lolium spp of Gramineae. It is usedextensively as both turf and forage. And, it has an important role in repairing heavy metalcontaminated areas. With the worsening of the heavy metal pollution, especially heavy metalscopper, lead, cadmium pollution has a serious impact on our lives. Therefore, it has animportant significance to research on the responding mechanism and alleviating measuresunder Cu, Pb, and Cd stress in ryegrass plants. Salicylic acid （SA） and nitric oxide （NO） aretwo plant growth regulators may be involved in plant growth, development, disease resistance,stress tolerance and other physiological processes. In this paper, solution culture experimentswere conducted to investigate the effects of NO and SA on physiological and biochemicalmetabolism in ryegrass under Cu, Pb, Cd stress. The main results were as follows:（1） Addition of50,100,200μmol SNP significantly decreased the transport of Cd from rootsto shoots, alleviated the inhibition of K, Ca, Mg and Fe, Cu, Zn absorption induced by Cd,reduced the toxicity symptoms and promoted the plant growth. The accumulation of reactiveoxygen species （ROS） significantly increased in ryegrass seedlings under Cd stress, andresulted in the lipid peroxidation, which was indicated by accumulated concentration ofthiobarbituric acid-reactive substances （TBARS）. Addition of addition of50,100,200μmolSNP significantly decreased the level of ROS and lipid peroxidation. Activities of antioxidantenzymes showed the same changes also, addition of50,100,200μmol SNP increasedactivities of superoxide dismutase （SOD）, peroxidase （POD）, catalase （CAT） and ascorbateperoxidase （APX） in ryegrass seedlings exposed to Cd. And100μmol SNP had the mostsignificantly alleviate effect to Cd toxicity, however, addition of400μmol SNP had nosignificant effect compared with Cd treatment.（2） Exogenous SA treatment with exogenous NO is similar to significantly increase netphotosynthesis and transpiration rate, the antioxidant enzyme activities, reduced H₂O₂content,O₂^·-generation rate, and contents of MDA in ryegrass, significantly enhanced absorption ofmineral elements, inhibit the transportation of Cd from root to shoot. The effect of alleviationof200μmol/L SA is slightly better than100μmol/L SNP under Cd stress.（3） Compared with the single addition of100μmol/L SNP or200μmol/L SA, adding100 μmol/L SNP+200μmol/L SA, the more obvious to alleviate the effects of ryegrass under Cdstress.The results show that NO+SA, significantly alleviated the stress damage on ryegrasswith100μmol/L CdCl2stress, and increased the growth amount, the contents of chlorophylland proline, the net photosynthetic rate （Pn）, the transpiration rate （Tr）, the stomatalconductance （Gs） and the antioxidant enzyme activities, reduced H₂O₂content, O₂^·-generationrate, intercellular CO₂concentration （Ci） and contents of MDA in ryegrass, significantlyenhanced absorption of mineral elements, inhibit the transportation of Cd from root to shoot,Significantly promote the growth of ryegrass under Cd stress.