The Relationship between the Stoma Density of Eggplant Leaves and Their Resistance to Polyphagotarsonemus latus The Relationship between the Stoma Density of Eggplant Leaves and Their Resistance to Polyphagotarsonemus latus Leaf Epidermal Micro-morphology Characteristics of Wild Cerasus humilis(Bge.) Sok. of Yanshan Mountains The changes of water-use efficiency and stoma density of Leymus chinensis along Northeast China Transect