Studies on the Chemical Constituents of Pyrus Communis CLASSIFICATION AND NUTRITIOUS VALUE OF KOTUR AMUT(PYRUS COMMUNIS. L) Somatic Embryo Genesis from in Vitro Leaves of Pear Effect of Polyploidization of Pear(Pyrus communis L.)on Shoot Regeneration Ability from in vitro Leaf Explants Identification and Expression Analysis of the AQPs Gene Family in Pyrus communis