Photosynthetic characteristics of three tree species seedlings in Changbai Mountain under different CO2 concentrations STUDIES ON THE NUTRITION RELATIONSHIP OF PHOSPHORUS BETWEEN \%LARIX OLGENSIS\% HENRY AND \%FRAXINUS MANDSHURICA\% RUPR qRT-PCR Analysis of Gene Expression of AG and SOC1 During Flower Development of Fraxinus mandshurica Rupr.