A Preliminary Study On The Effects Of Hydrogen-rich Water On The Growth And Salt Tolerance Of Cucumber Seedlings

Cucumber is one of the main vegetables for cultivation.At present,soil salinization in facilities is becoming increasingly serious.Cucumbers are moderately salt-sensitive crops.In particular,seedlings have weak root systems and poor resistance.They are sensitive to the accumulation of salt in facilities and seriously affect their yield and quality.As a selective antioxidant and signal molecule,hydrogen is non-toxic and harmless.It has been widely studied because of the effects of participating in the regulation of plant growth and development and repairing of plant damage.Therefore,to study the effects of hydrogen on the growth and development of cucumber seedlings and the resistance to salt has great significance on improving plant growth status,increasing crop yield under soil salinization conditions,reducing pesticide pollution,and developing green agriculture.The paper clarifies the regulation effect of hydrogen-riched water on the growth,development and photosynthetic efficiency of cucumber seedlings.At the same time,the effects of hydrogen-rich water on physiological and biochemical characteristics of cucumber seedlings under salt stress were studied,as well the molecular mechanism of hydrogen-rich water increasing the salt resistance was discussed.The main findings are as follows:?1?Hydrogen-rich water has the effect of promoting the growth and development of cucumber seedlings and increasing the photosynthetic efficiency of the leaves.Among them,hydrogen water with a saturation of 50%works best.50%hydrogen-rich water can significantly increase the plant height,stem diameter,fresh weight,leaf area,soluble sugar and soluble protein content of cucumber seedlings.At the same time,hydrogen-rich water can regulate the photosynthesis of plants,but its regulation mechanism is not yet clear.After applying 50%hydrogen-rich water,the chlorophyll content and net photosynthetic rate?Pn?of cucumber leaves could be significantly increased.Hydrogen-rich water treatment had no significant effect on intercellular CO₂ concentration?Ci?,but it could significantly reduce stomatal conductance?Gs?.And transpiration rate?Tr?;Also,the initial fluorescence F₀,the maximum fluorescence F_m,and the PS?photochemical efficiency F_v/F_m decreased.It can be seen that the hydrogen-rich water may increase the photosynthetic rate by increasing the chlorophyll content and maintaining efficient of light energy absorption,transmission,and conversion so that the cucumber leaves capture more light energy.?2?Hydrogen-rich water pretreatment has a good promotion effect on the growth and development of cucumber seedlings under salt stress,and cucumber seedlings salt resistance was improved.The results showed that hydrogen-rich water could alleviate the inhibition of salt stress on cucumber seedling fresh weight,dry weight,root length,lateral root number and root-shoot ratio and increase the chlorophyll content and chlorophyll a/b value of cucumber seedlings under salt stress as well as enhance photochemical reaction efficiency and reduce energy dissipation.At the same time,hydrogen-rich water can increase soluble sugar,soluble protein and proline content in cucumber seedlings.?3?This resarch explores the physiological and molecular mechanisms of hydrogen-enriched water increasing the salt resistance of cucumber seedlings.Studies have shown that hydrogen-rich water can reduce the salt-induced superoxide anion,hydrogen peroxide,malondialdehyde content and lipid peroxidation and the activities of SOD,POD,CAT and the contents of ASA and GSH in cucumber seedlings under salt stress were increased.At the same time,qRT-PCR gene expression analysis showed that,pretreatment with hydrogen-riched water can inhibit the expression of protein kinase ROP1 in the plant-induced release of reactive oxygen species under salt stress and upregulate the expression of protein kinases LecRLK,transcription factor TGA5 involved in the regulation of osmotic stress,ionic stress and ROS clearance in plant under salt stress and NHX1 and SOS2 in SOS signaling pathway.And it significantly increased the expression of SOD,CAT and POD in the antioxidant enzyme system and key genes such as GR and APX in the ASA-GSH circulatory system of cucumber seedlings under salt stress.It can be seen that hydrogen-riched water can enhance the ability of cucumber seedlings to scavenge active oxygen,promote the balance of redox balance in cells,and reduce the oxidative damage of plants under salt stress by reducing the content of reactive oxygen species.