Roles of Polyamines in the Formation and Development of Plant Flowers Effects of Leaf Removal on Canopy Apparent Photosynthesis and Individual Leaf Photosynthetic Characteristics in Summer Maize under High Plant Density Trehalose-mediated signal transduction and stress tolerance in plants Effect of Low Nitrogen Rate Combined with High Plant Density on Grain Yield and Nitrogen Use Efficiency in Super Rice Ubiquitin/proteasome pathway and it‘‘‘‘s role in high plant sexual reproduction