Abstract:

Velvet ash（Fraxinus velutina）is widely planted in the coastal saline land for vegetation construction. Salt distribution in saline soil usually is un-uniform，so velvet is affected by the heterogeneous soil salinity due to its large root system. In this study，the growth character，photosynthesis parameters，root distribution and leaf ion accumulation of velvet ash seedlings were analyzed by the split root pots method under partial root-zone salt stress. The results showed that，growth of velvet ash seedlings under partial low salt stress was significantly higher than that of the uniform salt stress and partial high salt stress. There was no effect of partial high salt stress on the leaf water potential，but leaf stomatal conductance，net photosynthetic rate and transpiration rate were significantly lower than the control. Root biomass，especially the fine root biomass，in the salt-free stressed zone was significantly higher than that of the salt stress zone. Compared with uniform salt stress，partial salt stress had significantly reduced leaf Na+ content and increased the K+/Na+. The growth of velvet ash seedlings was inhibited with partial salt stress，and the higher of salinity in one part，the lower of growth rate，while biomass was significantly higher than the uniform salt stress. Under partial salt stress，the compensatory growth of fine root in the salt-free stress zone could abtain more water，reduce leaf Na+ accumulation and increase leaf K+ content to alleviate the salt stress.

Key words: velvet ash, Fraxinus velutina, split root, partial salt stress, biomass, root distribution, ion accumulation