Abstract: Morphological and hormonal changes during the shoot development of weeping peach ( Prunus persica var. pendula) were studied. The basal crotch and extended angles of shoots for the weeping form were 51.7°and 92.9°,respectively; as compared to 52.5°and 52.0°for the standard peach. This shows that the shoots of the two peaches started growth in similar angles, but the branches of the weeping form wept down as shoots get longer. The roots of weeping peach also grew downward with a crotch angle of 42.5°, compared to 78.3°for the standard form. When weeping peach trees were placed up side down, the braches also grew down to the earth, indicating that the growth direction is dictated by gravity. The lignin content in the standard form is higher than in the weep ing form which has much more lignin in the upper shoot than in the lower part. This suggests that the mechanical tissue of weeping peach hasweaker support ability for its branches. Similar to the
lignin distribution, GA₃ content measured by ELISA increased from the base to the tip of a weep ing branch where the gibberellins content is higher than the tip of a standard branch. This may result in that the tips of weeping branches grow faster than the development of second xylem, so the branches can't support their weight and weep downward. Treatment of braches ofweep ing peach by GA₃ changed the GA₃ content and distribution,increased IAA /GA₃ and CTK/GA₃ ratio, and promoted the cell division and development of xylem in branches, resulting in up right growth.

Key words: peach, Prunus persica var. pendula, shoot, development, hormone