Photosynthetic Physiological Characteristics in F1 Progeny of Fraxinus mandshurica and Fraxinus americana under Drought Stress Relationship Between Heterosis and Endogenous Plant Hormones in Liriodendron Study on Use of Hybrid Vigor for Gingko Studies on the nutrition element contents of transgenic Bt cotton hybrid leaves and its relationship with yield STUDIES ON ESTERASE ISOZYME OF HYBRID RICE IN DEVELOPMENTAL PROCESS The Cross Compatibility and Hybrid Seed Vigor among Three Glycyrrhiza Species Analysis of Transcriptome Differences among Populus deltoides with Different Growth Potentials