Mechanism Of Hydrogen Peroxide And Nitric Oxide Regulating Somatic Embryogenesis In Fraxinus Mandshurica

The research was carried out to study the effect of hydrogen peroxide?H₂O₂?and nitric oxide?NO?content on the function of PCD regulation,and enzymes relayed to H₂O₂metabolism and NO synthesis,and to explore the NO synthesis pathway of H₂O₂ and NO signal network during somatic embryogenesis by changing exogenous H₂O₂ and NO content of explantation intracellular in Fraxinus mandshurica,The objective of this research was to state the mechanism of somatic embryogenesis and PCD with the regulation of H₂O₂ and NO.The main research results were as follows:?1?H₂O₂ and NO were important endogenous regulator factors influencing the PCD of somatic embryogenesis in F.mandshurica synergistically.H₂O₂ and NO could be used as the cells indicative signal of PCD during the somatic embryogenesis.?2?Exogenous H₂O₂ and NO regulated of intracellular H₂O₂ metabolism and NO synthesis of somatic embryogenesis in F.mandshurica,and changed the activity of enzymes of SOD,POD and PPO related to the intracellular H₂O₂ metabolism,and as well as the activity of enzymes of NOS and NR related to NO enzymes,and finally changed the content of intracellular H₂O₂ and NO.As the important endogenous signal factors,H₂O₂ and NO induced the PCD in F.mandshurica synergistically.NO maybe located in the upstream of H₂O₂signaling pathways.In order to maintain the balance of NO/H₂O₂ in F.mandshurica and relieve the stress of low oxygen or oxygen,both the enzymes of antioxidant and NO synthase and content of H₂O₂ should be regulated.?3?There were two ways to compound the intracellular NO in somatic embryogenesis of F.mandshurica through Nitric oxide synthase?NOS?and nitrate reductase?NR?.But the two ways varied in the times of each leading role and and functions in somatic embryogenesis.The NOS and NR played an important role in the early time of culture and somatic transformed to embryonic stage,respectively.Both NO inhibitors inhibited the somatic embryogenesis and the accumulation of intracellular NO and H₂O₂,and further improved the explant browning.NaN₃treatment had a stronger inhibitory effect on accumulation of intracellular NO and H₂O₂ than the L-NMMA.NaN₃ treatment inhibited the total cell death and promoted the proportion of PCD.However,L-NMMA prometed the total cell death and the proportion of PCD in the early time of culture.