Abstract: The changes of ultrastructure in leaves of Korean pine (Pinus koraiensis Sieb. et. Zucc) are different under soil drought stress and PEG drought stress. Under soil drought stress lamella structure of chloroplast wrenched obviously and there was a black area, which had high electron density in the middle of chloroplast. Under PEG drought stress chloroplasts were swollen but no black area. Under soil drought stress the membrane of mitochondria remained clear and intact. mitochondrial matrix became much more darker and thicker. While under PEG drought stress the quantity of mitochondrion increased but the numbers of mitochondria decreased and mitochondrial matrix became thinner. It can be seen that under the two methods of drought stress the mechanism of damage and its physiological meaning maybe different too.

Key words: Korean pine (Pinus koraiensis) seedling, drought stress, chloroplast, mitochondrion