Abstract:

Objective: The endogenous hormones, including auxin, gibberellins, and abscisic acid, play an important role in regulating the embryonic development. The dynamics of indole-3-acetic acid (IAA), gibberellic acid (GA₄), cis-abscisic acid (cABA), and trans-abscisic acid (tABA) were studied, in embryos and flesh at four important developmental stages of the same jujube (Ziziphus jujuba) variety, in order to reveal the relationship between the embryo abortion and the changes of endogenous hormones during fruit development and to provide evidence for clarifying the mechanism of jujube embryo abortion and theoretical guidance for salvage, germplasm innovation, especially cross breeding of jujube embryos. Methods: The development of fruit and immature embryos in 20-50 days of Z. jujuba 'Lengbaiyu' were observed during different development stages, including pro-embryo, small globular embryo, globular embryo and torpedo shaped embryo, and the concentration of IAA, GA₄, cABA, and tABA in embryo and flesh of normal embryo and aborted embryo during the four embryonic development stages was analyzed using liquid chromatography-mass spectrometry (HPLC-ESI-MSn). Results: 1) The IAA content was significantly higher in the embryo than in the flesh. The IAA content in the embryo increased gradually for the normal embryo, and gradually decreased for the aborted embryos. The IAA content in the flesh displayed an inverted V-shape for the normal embryo, and a normal V-shape for the aborted embryo. 2) The content of GA₄ was significantly lower in the embryo than in the flesh and it was at a lower level. The GA₄ content was lower in the normal embryos than in the aborted embryos. The GA₄ content in the flesh showed an increase earlier followed by a decrease later in both the normal and the aborted embryos. 3) cABA showed a gradual decrease in the development of flesh and embryo. The cABA content was greater in the normal embryos and lower in the aborted embryos respectively than in the flesh. 4) The content of tABA was higher in the embryo than in the flesh. The content of tABA displayed a tendency of gradual decrease in the normal embryos, and a tendency of gradual increase in the aborted embryos and even higher than that in the normal embryos at a later stage. The tABA content in the flesh for both the normal and the aborted embryos displayed an earlier decrease followed by a slow increase later. 5) The lower level of GA₄, higher level of IAA in the embryos, the lower levels of tABA, cABA and the high IAA/GA₄ were beneficial to the normal development of immature embryos. The decrease of IAA, the continuous increase of tABA, and the decrease of (GA₄+IAA)/ABA ratio in embryos were the important factors leading to embryo abortion. Conclusion: In the early stage of jujube embryo development, higher growth hormones are required, and the increase content of tABA in the embryo at the later stages may cause embryo abortion.

Key words: Ziziphus jujuba, embryo abortion, endogenous hormone