Abstract:

In order to probe the relationship between terminal bud death and endogenous hormones in Paulownia, ELISA was adopted to measure the content changes of endogenous hormones in the terminal buds from top shoots, the upper lateral branches, the middle lateral branches and the lower lateral branches of one-year-old P. tomentosa ×P. fortunei ‘33’. The results are as follows: 1) IAA in all different terminal buds had similar change trend of "drop-rise-drop", with only except for what IAA in terminal bud from upper lateral branch delayed to decline after reaching its peak; 2) The change of GA₃ content of terminal buds from top shoots, the upper lateral branches and the lower lateral branches showed a basically same trend, namely, "rise-drop-rise-drop" with two peaks; but GA₃ content from the middle lateral branches presented a " drop-rise-drop"; 3) The changes of ABA content from all different terminal buds elevated at first, then reduced and finally stabilized in the low level; 4) The changes of ZR content from different terminal buds showed different trends, with an overall downward trend. There existed competition relations and inhibition among terminal buds from different branches positions; 5) From Aug-15 to Sept-15, IAA,GA3,ZR,ABA and (IAA+GA₃+ZR)/ABA presented a downward trend, which indicated that the hormones of growth promotion and dormancy induction were lower. The terminal bud had no competitive advantage compared with other adjacent tissue, and the dynamic balance of endogenous hormones was broken. This study illustrated a clear relationship between terminal bud death and endogenous hormones in Paulownia, and laid a foundation for further study of the terminal bud death mechanism in Paulownia.

Key words: Paulownia, endogenous hormones, ELISA, terminal bud death