Relationship Between Photosynthetic Characteristics and Leaf Vein Density in Sorghum bicolor and Perilla frutescens Leaf Traits and Their Associations among Liana Species in Tropical Rainforest Changs laws of nutrient elements, veins density, physiological index in Camellia oleifera leaves with different tree ages and their correlation with yield Leaf venation functional traits and their ecological significance Stomatal Traits are Evolutionarily Associated with Vein Density in Basal Angiosperms