Exogenous abscisic acid (ABA) could inhibit cadmium (Cd) accumulation in plants; however, its performance in an uneven iron (Fe) background remains unknown. Here, we found that the inhibitory effects of ABA on Cd accumulation in plants were optimal under nonlimiting Fe availability (25 and 50 µM), causing a reduction of 25–50 %, whereas only a 0–29 % decrease was observed in a Fe-free or -deficient (5 µM) medium. Although ABA significantly inhibited the expression of IRT1 under different Fe supplies, the inhibitory effects of ABA on Cd accumulation were lower (or absent) in irt1-mutants than in wild-type plants growing under nonlimiting Fe availability, whereas no significant difference was found under Fe deficiency. The mechanisms by which ABA reduces Cd accumulation under different Fe environments may differ. Furthermore, under Fe sufficiency, ABA increased Fe levels of root apoplasts by 91 % without changing the activity level of root ferric reductase (FCR). In contrast, ABA resulted in a 17 % decrease in Fe concentration in apoplasts and a 37 % decrease in FCR activity under Fe-deficient conditions. Thus, under Fe sufficiency, plants may show a reduced accumulation of Cd by accumulating more Fe in the apoplasts, which in turn inhibits the expression of IRT1. However, plants are more prone to redirect apoplastic Fe to prevent Cd accumulation under Fe deficiency. The different mechanisms of inhibition of Cd accumulation by ABA under different Fe supplies revealed in this study may provide guidelines for the precise regulation of Cd accumulation in crops via ABA-based strategies.

外源脱落酸（ABA）可以抑制植物体内镉（Cd）的积累；然而，它在不均匀的铁 (Fe) 背景中的表现仍然未知。在这里，我们发现 ABA 对植物中 Cd 积累的抑制作用在非限制性铁可用性（25 和 50 µM）下是最佳的，导致减少 25-50%，而在铁中仅观察到 0-29% 的减少。 - 游离或缺乏 (5 µM) 培养基。尽管 ABA 在不同的铁供应下显着抑制了IRT1的表达，但在irt1中 ABA 对 Cd 积累的抑制作用较低（或不存在）- 突变体比在非限制铁可用性下生长的野生型植物，而在铁缺乏下没有发现显着差异。ABA 在不同铁环境下减少镉积累的机制可能不同。此外，在铁充足的情况下，ABA 在不改变根铁还原酶 (FCR) 的活性水平的情况下将根质外体的铁水平提高了 91%。相比之下，ABA 导致质外体中 Fe 浓度降低 17%，在 Fe 缺乏条件下 FCR 活性降低 37%。因此，在铁充足的情况下，植物可能通过在质外体中积累更多的铁来减少镉的积累，从而抑制IRT1的表达. 然而，植物更容易重定向质外体铁以防止缺铁下镉的积累。本研究揭示的不同铁供应下 ABA 抑制 Cd 积累的不同机制可能为通过基于 ABA 的策略精确调控作物中 Cd 积累提供指导。