Effect Of Hydrogen-rich Water On Maize Roots Under Salt Stress

In the present study,we studied the hydrogen’s effects on the growth andevelopment of maize roots and seedlings under salt stress.Zheng 58 cultivar（Zea mays L.）was adopted as the material and nutrient solution hydroponics was applied,and hydrogen-rich water（HRW）was used as the donor of H₂.Here,the biomass and physiological activity of maize seedlings under different treatments were compared,and the expression of root ATPase-related gene MHA1 and calcium-dependent protein kinase CDPK21 were analyzed.The aim of this study was to investigate the alleviation mechanisms of alleviate of hydrogen to plants under salt stress and thus to provide a basis research for improving the plants growth under salt stress.The main results are as follows:（1）Hydrogen-rich water treatment improved root development and seedlingbiomass of maize compared with the water treatment.（2）Salt stress significantly inhibited the growth and development of maize rootsand seedlings,resulting in a decreased biomass.Hydrogen-rich water alleviated the growth inhibition of NaCl(150 mmol·L^-1)on maize seedlings and roots.Analysis of root configuration and root anatomical observation showed that hydrogen-rich water treatment significantly increased total root length,total surface area,total volume,and root diameter of maize（P<0.05）.（3）Hydrogen-rich water significantly improved the chlorophyll content andstomatal opening of maize seedlings under salt stress,and thus enhanced the photosynthetic capability of maize seedlings.With the increased relative water content of seedlings,the metabolism of roots accelerated,and the soluble sugar was promoted;The larger diameter of the stele,especially the catheter in the metaxylem,promoted the transport of water and inorganic salts to the plant shoot,and thus increased the biomass of seedlings.（4）Analysis of histochemical staining and malondialdehyde content in maizeroots showed that hydrogen-rich water remarkably reduced accumulation of malondialdehyde and reactive oxygen species under salt stress.Antioxidant enzymes SOD and POD activity bioassay revealed that hydrogen-rich water obviuously enhanced the activity of above antioxidant enzymes.We speculated hydrogen-rich water treatment could reduce the excessive accumulation of peroxide and superoxide,thereby maintain the integrity of the membrane to some extent and alleviate the damage of salt stress to the membrane.（5）In hydrogen-rich water treatment group,the activities of plasma membraneH⁺-ATPase,tonoplast H⁺-ATPase and H⁺-PPase were significantly increased,and the expression of MHA1 gene and calcium-dependent protein kinase 21（CDPK 21）was up-regulated,which may cause changes in membrane potential and transmembrane pH gradient,and therefor reduce cell damages caused by ion osmosis imbalance.The upregulation of CDPK21 is conducive to Ca²⁺binding and further activates Kinase and phosphatase.More,affinity of the Ca²⁺binding site increasing is favorable for Ca²⁺efflux and growth inhibition alleviation caused by ion stress.In conclusion,the present study revealed that hydrogen-rich water could alleviatethe growth inhibition of maize roots and seedlings under salt stress by reconstituting the active oxygen homeostasis and ion homeostasis.