Release Effects Of Exogenous SA,GSH,Ca And CA On Stachys Lanata Under Cd Stress

Soil heavy metal cadmium pollution control is a global hot issue in current research.Heavy metal Cd is a non-essential metal ion in plants,which has toxic effects on plants.To explore the physiological response mechanism of exogenous substances to Cd stress and the changes of Cd accumulation in plants,the mechanism of sustained release of exogenous substances on Cd toxicity in plants can be revealed.In this study,Stachys lanata,a herbaceous plant,was used as experimental material.After 10 days of Cd²⁺stress at 300 mg/kg,gradient concentrations of salicylic acid?SA?,glutathione?GSH?,calcium?Ca?and citric acid?CA?were sprayed on the leaves of the corresponding plants.with no Cd²⁺stress(0 mg/kg Cd²⁺)and 300 mg/kg Cd²⁺stress?CK?as control.The effects of four exogenous substances on the growth,leaf osmotic substance content,chlorophyll content,three antioxidant enzymes activity,AsA-GSH circulatory system and Cd accumulation in plants were studied.The results show that compared with 0 mg/kg Cd²⁺treatment,?1?CK inhibited the growth of Stachys lanata.Compared with CK,the treatment of four exogenous substances improved plant height,leaf color,leaf area and germination of the plants to a certain extent,and increased relative water content of leaves,dry matter accumulation in underground and aboveground parts,and promoted plant root activity.The dry matter accumulation of SA,GSH,Ca and CA reached 130.53%,138.17%,193.13%and170.23%of CK at concentrations of 1.0,0.4,2.0 and 1.0 mmol/L,respectively.?2?The MDA content in CK leaves increased by 83.47%on the 7th day of treatment.MDA content decreased after adding sustained-release agent,and decreased by 47.17%,53.28%and 50.32%on the 7th day of treatment with SA,GSH and Ca at 1.0,0.2 and 4.0mmol/L,respectively,compared with CK,whereas CA decreased by 22.40%on the 3rd day of treatment with 1.5 mmol/L.Under CK treatment,the contents of soluble sugar,soluble protein and free proline in leaves decreased by 26.15%,15.42%and 32.17%,respectively.Compared with CK,except for the decrease of soluble sugar content in the 3rd day of 0.4mmol/L GSH treatment,the other treatments were higher than CK.The highest content of soluble sugar and soluble protein appeared at the 3rd day of SA concentration 1.0 and 1.5mmol/L,respectively,which increased 16.06%and 14.13%compared with CK,and the highest content of free proline reached at the 7th day of SA treatment at 0.5mmol/L,which increased 311.39%compared with CK.The peak values of the three indicators appeared on the 7th day under the treatment of GSH,Ca and CA.The concentration of GSH was 0.3,0.3 and 0.1 mmol/L,which increased50.28%,12.77%and 313.77%respectively compared with CK.The concentration of Ca was4.0,3.0 and 1.0 mmol/L,which increased 78.76%,29.33%and 260.00%respectively compared with CK.The concentration of CA was 1.5,0.5 and 0.5 respectively,which increased 88.98%,12.71%and 313.77%compared with CK.The chlorophyll content of leaves decreased by 60.34%under CK treatment.Compared with CK,SA,GSH,Ca and CA increased chlorophyll content by 1.05-1.47 times,1.07-1.72times,1.08-1.15 times and 0.99-1.49 times,respectively.?3?Under CK treatment,SOD,POD and CAT activities increased.Compared with CK,the activities of SOD,POD and CAT increased with the treatment of four exogenous substances.The three indexes reached the highest values on the 1st,7th and 7th day of SA treatment,and increased by 57.39%,85.00%and 38.51%compared with CK.Under the GSH treatment,the maximum value of the three indicators appeared on the 1st day of 0.3mmol/L,the 7th day of 0.3mmol/L and the 7th day of 0.2mmol/L.Compared with CK,it increased by60.77%,26.81%and 50.21%.The maximum values of the three indexes increased by 98.33%,29.98%and 49.39%respectively on the 1st day of 4.0mmol/L,3rd day of 3.0mmol/L and 7th day of 3.0mmol/L respectively,under Ca treatment.Under CA treatment,the three indicators reached the maximum at the first day of 1.0mmol/L treatment,the third day of 1.5mmol/L treatment and the first day of 1.5mmol/L treatment.CK increased by 105.81%,40.78%and26.15%.?4?The content of AsA in the 7th day of CK treatment decreased by 47.08%,the content of GSH increased by 38.30%,and the activities of APX and GR increased by 193.00%and202.29%,respectively.Compared with CK,the changes of AsA,GSH,APX and GR were not consistent under the four exogenous substances treatment.The maximum content of AsA appeared on the 7th day of treatment with SA,GSH,Ca and CA.The concentration of AsA was 1.0,0.3,3.0 and 2.0 mmol/L,respectively,which increased 83.46%,144.26%,166.62%and 170.75%compared with CK.The maximum content of GSH appeared on the 3rd day of treatment with 1.5 mmol/L SA,0.2 mmol/L GSH,3.0 mmol/L Ca and 1.5 mmmol/L CA on the1st day,CK increased 158.03%,110.26%,110.26%,68.63%,68.63%and 13.97%respectively compared with CK;APX activity peak was 1.5mmol/L SA treatment for 3d,0.4mmol/LGSH,1.0mmol/L Ca,1.5mmol/LCA treatment for the 7th,respectively,1.58,1.72,1.54 and 1.93 times of CK;the peak of GR activity appeared at 1.5mmol/L SA and0.2mmol/L GSH treatment 1d,3.0mmol/L Ca and 1.5mmol/L CA 3rd day of treatment increased by 218.25%,213.83%,144.50%and 131.85%,respectively,compared with CK.?5?The absorption of cadmium mainly concentrated in the root.Exogenous SA had no significant effect on Cd uptake in plants.GSH inhibited Cd transport to shoots,Ca treatment inhibited Cd uptake in plants,while CA promoted Cd accumulation in roots and leaves of plants.In conclusion,exogenous SA,GSH,Ca and CA had a certain effect on slow-release of Stachys lanata under Cd stress,and the optimal concentration of slow-release were SA 1.0-1.5mmol/L,GSH 0.3-0.4 mmol/L,Ca 2.0-3.0 mmol/L and CA 1.5-2.0 mmol/L,respectively.