Effect of Fertilization on Woody Characteristics of Betula platyphylla Sequence and Expression Analysis of MYB Family Genes in Betula platyphylla Suk. Construction of RNA interference vector carrying two genes of DS and CAS of Betula platyphylla Suk(Birch.) Effect of Ca2+ on Mediating the MeJA-induced Synthesis of Triterpenoid in Suspension Cells of Betula platyphylla Suk. Effect of Exogenous GA3 on Flowering Genes Expression of Betula platyphylla by Real-Time Fluorescent Quantitative PCR WATER METABOLISM AND CHANGES OF SEVERAL OSMOTICAIN LEAVES OF BETULA PLATYPHYLLA SEEDLINGS UNDER DROUGHT STRESS