Drought Resistance of Four Species of Tree Saplings for Afforestation in Karst Regions

Physiological variation was studied of one-year-old saplings of Elaeocarpus sylvestris,Eurycorymbus cavaleriei,Platycladus orientalis and Koelrenteria paniculata exposed to different levels of drought stress imposed by watering the saplings once every 2(as control),4,6 and 8 days.Effects of the droughts on the saplings were evaluated by monitoring variation of the relative water content(RWC),relative membrane permeability(RMP),contents of malondialdehyde(MDA),free proline(Pro) and soluble sugar(SS),activity of peroxidase(POD) in their leaves.Results show that RWC decreased,and RMP and contents of MDA,free proline and soluble sugar increased with the intensifying drought stress,but POD activity varied differently.Integrated evaluation of the drought resistance of the four saplings was performed with the subordinate function method,revealing a decreasing order in drought resistance of Eurycorymbus cavaleriei Platycladus orientalis Koelrenteria paniculata = Elaeocarpus sylvestris.Correlation analysis of the 6 physiological indices of drought resistance indicates that MDA,POD and Pro are closely correlated with each other.Analysis of variance and multi-comparison using the SSR method of the measurements of the saplings show that RMP,MDA content,POD activity and Pro content are useful indicators of drought resistance of the four species of saplings.