Abstract: With a Japanese salt-tolerant pumpkin cultivar ‘King Shintosa’(Cucurbita maxima × C. moschata) as rootstock and a cucumber (Cucumis sativus) cultivar ‘Xintaimici’ as cion, this paper studied the temporal dynamics of different form polyamines contents in the leaves of grafted and own-rooted cucumber plants under 100 mmol·L^-1 NaCl stress. The results showed that the free putrescence (Put) content of graftedplant leaves (G₂) was significantly higher than that of own-rooted plant leaves (O₂), except on the second day of NaCl stress. During the whole period of NaCl stress, the free spermidine (Spd) and spermine (Spm) contents of G₂ were significantly higher than those of O₂, and the total free polyamine content of G₂ peaked on the fourth day of stress. The free Put/PAs value of G₂ was significantly lower than that of O₂ except on the fourth day of stress, but (Spd+Spm)/Put value was significantly higher than that of O₂ during the whole period of stress. In the test period, the contents of conjugated and bound Put, Spd, Spm of G₂ were significantly higher than those of O₂. The total conjugated and bound polyamine contents of G₂ peaked on the sixth day of stress. Both conjugated Put/PAs and conjugated (Spd+Spm)/Put values had a similar changing trend to free polyamine. The bound Put/PAs value of G₂ was significantly lower than that of O₂ except on the sixth day of stress, while the bound (Spd+Spm)/Put value was significantly higher than that of O₂ during the whole period of stress. All of these demonstrated that grafted cucumber plant possessed a stronger salt tolerance.

Key words: enzyme activities., decomposition, leaf litter, microbial community, microbial quantity, root growth