Effects Of Exogenous Glycine Betaine On Physiological Characteristics In Super Black Waxy Maize Under Cadmium Stress

Cadmium?Cd?is one of the most toxic environmental pollutants for plant,because it can interfere with various plant physiological and biochemical processes,such as the destruction of photosynthetic pigment,and the damage of green plant photosynthetic system,causing the moisture and nutrient imbalance,hormone imbalance,lipid peroxidation damage on cell membrane,the destroy of antioxidant enzyme system,as well as the burst of reactive oxygen species,etc..Glycine betaine has the functions of maintaining cell osmotic pressure,protecting the enzyme,resisting salt and affecting the distribution of inorganic ions.Glycine betaine can effectively alleviate the toxic effects of cadmium on plants.A great deal of research has been done on the physiological function,mechanism,chemical change and scavenging system of reactive oxygen species.However,there are few reports on the effects of exogenous Glycine betaine on the antioxidant system of super black waxy corn under cadmium stress.Super black waxy maize seedling was used as materials through soil culture and a completely randomized block design was used in this study.Tested materials were treated separately with Cd and with exogenous GB after Cd dress.Various parameters were tested including plant photosynthetic parameters,chlorophyll contentmaximum photosynthetic efficiency,reactive oxygen species?O₂^-,H₂O₂?,malondialdehyde?MDA?and antioxidant enzymes?SOD,POD,CAT?activityandosmotic adjustment substance?proline,soluble total sugar,soluble protein?and ascorbate glutathione cycle?ASA,GSH,APX,GR,DHAR,MDHAR?etc.Studying the effects of exogenous GB on photosynthesis,reactive oxygen species,antioxidant enzyme system and ascorbate glutathione cycle of super black waxy maize seedling under cadmium stress will provide theoretical basis for the study of breeding and resistance to heavy metal stress of super black waxy maize.The results showed as follow:1.In a separate Cd test processing,super black waxy maize seedling biomass decreased comparing with control group?CK?accumulation.Biomass accumulation of super black waxy maize seedling obviously increased after adding exogenous GB.GB had the greatest effect on the biomass accumulation when concentration was 25 mg/kg.Therefore,the exogenous GB could improve the super black waxy maize seedlings under Cd stress.2.Photosynthesis of the super black waxy maize seedling decreased compared with CK,and weakened with the increasing of Cd concentration.Photosynthesis of super black waxy maize seedling increased obviously and the net photosynthetic rate,intercellular CO₂ concentration,transpiration rate,stomatal conductance,Fv/Fm and chlorophyll SPDA of super black waxy maize seedlings were also improved after adding exogenous GB.GB had the greatest effect on the photosynthesis when concentration was 25 mg/kg.Therefore,the exogenous GB could promote photosynthesis of the super black waxy maize seedling under Cd stress.3.Reactive oxygen species and membrane lipid oxidation product content of super black waxy maize seedlings increased significantly under Cd stress.Activity of antioxidant enzymes?CAT,SOD,POD?were lower than those of the control group.Antioxidant enzyme activity of super black waxy maize seedling were increased significantly after adding exogenous GB,which degradated reactive oxygen species and membrane lipid oxidation product content of super black waxy maize seedlings.And small molecules?proline,soluble sugar,soluble protein?content of super black waxy maize seedlings was also raised.GB had the greatest adjustmenteffect on the antioxidant enzyme system and osmotic regulation substances when concentration was 50 mg/kg.4.Antioxidants?GSH and AsA?of super black waxy maize showed the trend of increased first and then dropped with the increasing of Cd concentration.The content of reducedGSH and As A were lower than CK,while the content of oxidation GSH and ASA were higher than CK.The content of GSH,GSSH,AsC and DHA of the super black waxy maize seedlings were improved,and the activity of APX,DHAR,MDHAR and GR were improved after adding exogenous GB.GB had the greatest effect on the AsA-GSH cycle when concentration was 25 mg/kg.The experimental results showed that the Glycine betaine could alleviate the toxicity and the active oxygen burst of cadmium stress on the super black waxy maize seedling.This study provide a theoretical basis for the resistance of super black maize on heavy metal stress.