Comparative studies on different germplasms of Platycodon grandiflorum -their intercross and new types and differentiation of flower and seed color Effects of Salt-drought Intercross Stress on Physiological and Biochemical Characteristics of Ammodendron argenteum (Pall.) Kuntze Seedlings Physiological responses of two native shrub seedlings to drought and salt stress Growth,Physiological and Biochemical Characteristics of Tamarix chinensis Seedlings under Salt-drought Intercross Stress