H2O2 and Embryogen ic Callus Induction of Phalaenopsis spp. H2O2 and Embryogen ic Callus Induction of Phalaenopsis spp. A Study on the Conditions of Genetic Transformation into Poa pratensis L. by Agrobacterium Tumefaciens The Mutagenic Effects of 60Co-γ Radiation on White Clover Callus Establishment of High Efficient Regeneration System of Perennial Ryegrass and PEPC Gene Transformation Mediated by Agrobacterium tumefaciens Screening of Embryogenic Callus from Hybrid F1 of Caucasian Clover×White Clover