Changes of Metabolites and Flower Bud Differentiation of Camellia azalea Karyological Study on the Endangered Species Camellia azalea (Theaceae) Genetic Diversity Analysis for Leaf Main Traits of Camellia azalea Extraction and Characterization of the Flower Pigment of Camellia azalea Cloning, Expression and Functional Analysis of CaAPX Gene from Camellia azalea