Plantlet regeneration for hairy roots of Atropa belladonna by co-transformed PMT and H6H Expression pattern of genes involved in tropane alkaloids biosynthesis and tropane alkaloids accumulation in Atropa belladonna Establishment of the Exogenous Gene Expression System Based on Atropabelladonna Hairy Roots Cloning and expression analysis on arginine decarboxylase genes in Atropa belladonna Pharmacognostical study of Atropa belladonna Isolation of Embryo Sac with the Enzyme-Squash Technique Establishment of the Exogenous Gene Expression System Based on Atropabelladonna Hairy Roots