Effects Of H₂O₂ On Mineral Element Accumulation And Sugar Metabolism In Rice Under Cadmium Stress

Cadmium（Cd）is one of the most toxic heavy metal elements,and excessive Cd accumulation in plants can hinder the plant growth and development,and cause abnormal physiological metabolism,resulting in serious harm to plants.Hydrogen peroxide（H₂O₂）is an endogenous signaling molecule mediating various physiological processes in plant,and it also involved in plant defense responses to heavy metals.In this paper,rice（Oryza sativa L.cv.‘Zhongyou No.169’）were taken as the materials to investigate the effects of H₂O₂ pretreatment on the growth,glucose metabolism,Cd and mineral nutrients accumulation of rice seedling under Cd stress by the means of nutritional cultivation.The main results showed as follows:1.150μmol/L Cd treatment significantly inhibited the increase of plant height,root length and biomass of rice seedlings,decreased chlorophyll and carotenoid content in rice leaves,and inhibited root vigor.Exogenous H₂O₂ treatment can significantly alleviate the inhibition of Cd on rice growth,improve root vigor and chlorophyll content,and decrease the H₂O₂ content.However,the addition of H₂O₂ scavenger,DMTU,further aggravated the inhibition of Cd on the growth of rice seedlings.2.Under Cd stress,Cd content and accumulation in rice seedlings significantly increased,especially the accumulation of Cd in root.Cd treatment significantly reduced the content and accumulation of Ca,Mn,Mg,Cu and Zn in the leaves and roots of rice seedlings,as well as Fe content and accumulation in the leaves,but increased Fe accumulation in the roots.However,H₂O₂treatment significantly decreased Cd content and accumulation in leaves and roots of rice seedlings,but improved the content and accumulation of Ca,Mg,Cu and Zn in varying degree.H₂O₂ treatment increased Fe content and accumulation in the leaves under Cd stress,but decreased the Fe content and accumulation in the roots.Moreover,H₂O₂ treatment significantly decreased the Mn content and accumulation in the roots and significantly increased of the Mn content and accumulation in leaves under Cd stress.In addition,the addition of H₂O₂ scavenger,DMTU,further increased the Cd content and accumulation in rice seedlings under Cd stress,and also influenced the content and accumulation of Ca,Mn,Mg,Fe,Cu and Zn in the rice seedlings under Cd stress.3.Cd treatment reduced the contens of soluble sugars,sucrose,fructose and glucose in the leaves and roots of rice seedlings,promoted the accumulation of starch in rice seedlings,and inhibited the activities of amylase,α-amylase andβ-amylase.Exogenous H₂O₂ treatment can significantly improve the contents of soluble sugars,sucrose,fructose and glucose in rice leaves and roots under Cd stress,increased the activities of amylase,α-amylase andβ-amylase,decreased the starch content.However,the addition of H₂O₂ scavenger,DMTU,resulted in further reduction of soluble sugar,sucrose,fructose and glucose contents in the leaves and roots of rice seedlings under Cd stress.4.Cd treatment markedly reduced the activities of SS and SPS in the leaves of rice seedlings and increased the activities of AI and NI.Exogenous H₂O₂ treatment significantly increase the activities of SS and SPS in the leaves under Cd stress and reduced the activities of AI and NI,but the addition of H₂O₂ scavengers significantly reduced the activities of SS and SPS in the rice leaves,but significantly increased the activities of AI and NI.