Evidence that Natural Selection is the Primary Cause of the Guanine-cytosine Content Variation in Rice Genes Measurement of  Total Level of DNA Methylation in Phalaenopsis spp. PLB Dynamic Changes of Methylcytosine in Polarized Cell Growth and Their Response to GABA Signals EFFECT OF 5-AZACYTOSINE ON FLOWERING AND DNA METHYLATION LEVEL OF STEM APICES IN RADISH (Raphanus sativus L.) Determination of nine kinds of nucleosides in Spirodelae Herba from different habitats by UPLC-MS/MS