Research On Respiratory Physiology Mechanism Of γ Irradiated Fresh Walnuts During Germination

Fresh walnuts are popular with consumers because of their various nutrition,special flavour as well as antioxidant ability.However,fresh walnuts with more water content,higher enzyme activity and greater respiration rate are easy to germinate and decay,which could make bad effects on quality.Previous research in our team has found that ⁶⁰Cογirradiation had an remarkable effect on inhibition of walnuts germination.Meanwhile,germination is closely related to respiration metabolism.In order to provide theoretical basis for fresh walnuts storage,fresh walnuts in the research had been treated with 0.300kGy and 0kGy⁶⁰Cογirradiation,were storaged in sands at about 25℃for 24 days.During the storage period,some indicators about germination and respiration metabolism have been monitored.Conclusions in the research are as follows:（1）Irradiation delayed the germination date and decreased the rate of germination as well as suppressed the growth of buds.Therefore,⁶⁰Cογirradiation of 0.300kGy has a significant effect on inhibition of germination.（2）Respiration intensity is an important indicate of plant life movement,which are essential in the process of seed germination.Although irradiation raised the respiration in initial storage stage,suppressed that after15day after storage.（3）The research results about respiration terminal enzymes showed that irradiation decreased the activity of AAO and CCO both in kernel and buds,but only the activity of PPO in kernel.In conclusion,irradiation decreased respiration intense by inhibiting the activity of respiration terminal oxidase and reducing the transmission rate of electrons in redox reaction.（4）Futhermore,the results of the activity of NADK and the content of NADH,NADPH showed that irradiation strengthened PPP and weakened EMP-TCA.Therefore,respiration intense was cut down as a result of decrease of EMP-TCA,the respiration efficiency of which was supior to PPP.（5）Activity and gene expression of key enzymes in PPP were monitored in the research because of the importance of PPP on seed germination.The results showed that the irradiation increased the activity of G6PDH and 6PGDH,hightening PPP in respiration passway.（5）As the only way to convert oil into sugar,glyoxylate cycle is important in oil seed germination,the enzyme activity and gene expression of key enzymes in which is monitored in the research.The results showed that irradiation suppressed the ICL activity both in kernel and nut,decreased the efficiency of glyoxylate acid cycle,leading to the lack of respiratory substrate and decreased respiration intense.In conclusion,⁶⁰Cογirradiation hightened PPP,weakened EMP-TCA and glyoxylate cycle,reduced the activity of terminal enzymes and electron transfer rate.As a result,⁶⁰Cογirradiation reduced respiration metabolism and decreased germination.