Exogenous abscisic acid alleviates zinc uptake and accumulation in P opulus × canescens exposed to excess zinc

A greenhouse experiment was conducted to study whether exogenous abscisic acid ( ABA ) mediates the responses of poplars to excess zinc ( Z n). P opulus  ×  canescens seedlings were treated with either basal or excess Z n levels and either 0 or 10 μ m ABA . Excess Z n led to reduced photosynthetic rates, increased Z n accumulation, induced foliar ABA and salicylic acid ( SA ), decreased foliar gibberellin ( GA 3 ) and auxin ( IAA ), elevated root H 2 O 2 levels, and increased root ratios of glutathione ( GSH ) to GSSG and foliar ratios of ascorbate ( ASC ) to dehydroascorbate ( DHA ) in poplars. While exogenous ABA decreased foliar Z n concentrations with 7 d treatments, it increased levels of endogenous ABA , GA 3 and SA in roots, and resulted in highly increased foliar ASC accumulation and ratios of ASC to DHA . The transcript levels of several genes involved in Z n uptake and detoxification, such as yellow stripe‐like family protein 2 ( YSL2 ) and plant cadmium resistance protein 2 ( PCR2 ), were enhanced in poplar roots by excess Z n but repressed by exogenous ABA application. These results suggest that exogenous ABA can decrease Z n concentrations in P . ×  canescens under excess Z n for 7 d, likely by modulating the transcript levels of key genes involved in Z n uptake and detoxification.