Effect of drought stress in soil on morphology and physiological characteristics of Peristrophe japonica and Goldfussia pentstemonoides seedlings

Using weighting method for controlling relative water content in soil with( 85. 0±2. 5) %( the control),( 67. 5±2. 5) %( light drought),( 50. 0 ±2. 5) %( moderate drought) and( 32. 5 ±2. 5) %( heavy drought),changes of plant morphology and physiological characteristics of 2-year-old seedlings of Peristrophe japonica( Thunb.) Bremek. and Goldfussia pentstemonoides Nees under drought stress in soil were studied. The results show that after soil drought stress treating for 30 d,there are some changes in external morphology of two species,in which,the change in P. japonica is mainly leaf chlorosis,thinning and wilting,and branch weeping; that in G. pentstemonoides mainly stem lodging,leaf softening and petiole weeping. As increasing of soil drought stress degree,natural saturation deficit,critical saturation deficit,water requirement,bound water content,content ratio of bound water to free water,contents of proline and soluble sugar in leaf of two species all gradually increase and all are higher than those of the control, while, their free water content, maximum and minimum water potentials,and soluble protein content all gradually decrease and all are lower than those of the control. General,as compared with the control,there are extremely significant or significant differences in every physiological index of two species tested under heavy drought stress,while no significant difference in some physiological indexes under light and moderate drought stresses. There are obvious differences in change range of every physiological index between two species. Under the same drought stress,natural saturation deficit,water requirement,free water content,decreasing range of maximum and minimum water potentials,content of proline,and decreasing range of soluble protein content in leaf of P. japonica all are higher while its critical saturation deficit,bound water content,content ratio of bound water to free water and soluble sugar content all lower than those in leaf of G. pentstemonoides. Comprehensive analysis result indicates that two species tested possess a certain resistance to drought stress in soil,and G. pentstemonoides has a more advantaged physiological resistant mechanism to drought stress.