Abstract:

The spot experiments of Pteroceltis tatarinowii seedlings were carried out by simulating soil condition of drying-wetting alternation similar to karst region.The variation of physiological indexes,growth indexes and the restoration ability of seedlings after re-watering were studied.The results showed that the variation of physiological indexes was different with the times of soil drying-wetting alternation.The variation of water saturation deficit,xylem water potential of root and stem,net photosynthetic rate,transpiration rate,leaf plasm membrane permeability of seedlings changed greatly at one cycle,and relatively stable at two cycles,but the variation enlarged again at three cycles.These changes reflected a process from the reaction,and adaptation to inadaptation of the seedlings to soil drying-wetting alternation condition.After re-watering,the restoration degree of these indexes had a negative correlation with the cycle times.The compensatory effect was common in the restore process,especially for growth indexes,it is an adaptative strategy of seedlings to soil drying-wetting alternation condition.The effects of soil drying-wetting alternation on physiological indexes of P.tatarinowii seedlings were more serious at the early growth stage than at the rapid growth stage,but for the growth indexes were contrary.Therefore,the growth potential of seedlings would be restricted by repeated drying-wetting alternation condition at the rapid growth stage.

Key words: Pteroceltis tatarinowii, seedling, soil drying-wetting alternation, restoration ability, compensatory effect