**Effect of 5-Aminolevulinic Acid (ALA) on Leaf Diurnal Photosynthetic Characteristics and Antioxidant Activity in Pear (***Pyrus Pyrifolia* **Nakai)**

 Ming Shen, Zhi Ping Zhang and Liang Ju Wang *College of Horticulture, Nanjing Agricultural University, Nanjing China* 
