MECHANISM OF FLURIDONE-INDUCED SEED GERMINATION OF CISTANCHE TUBULOSA

Our previous study disclosed that fluridone, a synthesis inhibitor of abscisic acid (ABA), could stimulate seed germination in the holoparasitic plant Cistanche tubulosa. Nonetheless, the underlying mechanisms have not been thoroughly elucidated. In the present study, an attempt was made to reveal the mechanism of fluridone breaking seed dormancy in C. tubulosa and to determine the contribution of hormones in this process. The ABA level in seeds initially decreased following fluridone treatment and was subsequently maintained at a concentration of 31 ng.g(-1) DW (dry weight) three days later. The contents of gibberellins (GAs) initially increased and subsequently were maintained at a level of 40 ng.g-1 DW after ten days. However, the increment of seed germination induced by fluridone was inhibited after the introduction of exogenous ABA or paclobutrazol (a synthesis inhibitor of GAs). Furthermore, inhibition from paclobutrazol was reversed by an additional treatment with exogenous GA3. When the ratio of endogenous GAs to ABA reached 4:3, C. tubulosa seeds initiated germination. By contrast, although the ratio of endogenous GAs to ABA content reached 2:1 by cold stratification, C. tubulosa seeds could not germinate unless exogenous GA3 was added. In summary, our current study revealed that (i) GAs and ABA play key roles for the seed germination of C. tubulosa, (ii) fluridone inhibited ABA biosynthesis but increased the concentration of GAs in seeds, and (iii) fluridone might initiate other processes associated with germination.Science and Technology Program for Public Wellbeing of China [2012GS650101]SCI(E)ARTICLEpengfeitu@bjmu.edu.cn3971-9764