Abstract:

Ovule abortion of tetraploid Robinia pseudoacacia was divided into 3 phases. Initial phase occurred between 5 days and 30 days after coronal opening, zygote in dormancy, and the average abortion rate was 51.9%. The abortion ovules had less volume without embryo and displayed deep yellow color, belonging to ovule abortion without embryo. This abortion could be related to physiological fruit drop. Middle phase abortion occurred between 30 days and 50 days after coronal opening, with spherical embryo and heart-shaped embryo formed. The average abortion rate was 30.2%, abortion ovules had less volume and displayed deep yellow part of surface with yellow-transparent liquid on the margin. Around 33.2% of the abortion ovules possessed embryo. Last phase abortion occurred after 50 days after coronal opening, with cotyledonary embryo having gradually formed, and the average abortion rate was 72.6%. The abortion ovule was shriveled, had less volume, and displayed deep yellow color. Approximately 70.8% for abortion ovules had embryo. Middle and last phase abortion belonged to the ovule abortion that was either with embryo or without embryo, and the abortion was mainly caused by death and abnormal of young embryo. In the ovule development period 15 days after coronal opening, the contents of growth-promoting endogenous hormones(GA₃, IAA) in abortion ovules were always lower than in normal ovules, and the content of growth-restraining endogenous hormone(ABA) and the ratio of ABA/(IAA+GA₃) for abortion ovules were always higher than that for normal ovules. The results suggested that the abnormal endogenous hormones were likely a cause of the ovule abortion of tetraploid Robinia pseudoacacia.

Key words: Robinia pseudoacacia, autotetraploid, ovule abortion, endogenous hormone