The Effects Of Nitric Oxide On Cold Response And Polyamine Synthesis Of Poncirus Trifoliata

The hardiness is improved of trifoliate orange after cold acclimation, but its physiological mechanism remains unclear. Nitric Oxide (NO) is small molecule, involved in plant growth and development and stress tolerance. This study aims to study change in NO level during cold acclimation and investigate effect of exogenous SNP on freezing tolerance. Meanwhile effect of exogenous SNP on polyamine synthesis was analyzed. The main results are as follows:1. Plant grown for3d at4℃or25℃were treated at-6℃for2h, followed by recovery at25℃, survived rate of the plants from4℃was45.8%, while from25℃was8.3%, the results indicated that cold acclimation can improve chilling tolerance.2. NO content and NOS activity were significantly higher than untreated group. cold acclimation increased catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) activities.3. Exogenous addition of SNP or water was applied during cold acclimation before-6℃treatment, SNP significantly enhanced NO content and NOS activity and the survival rate after recovery were also higher than the control group. SOD activity was significantly increased but POD was not obviously changed.4. Addition of SNP under25℃for5d before-6℃treated for2h, the results showed that SNP treatment let to increase in NO level. The survival rate was increased, while cell membrane permeability was decreased. Exogenous SNP improve putrescine、spermidine and spermine elevated polyamine level.