The accumulation and transport of abscisic acid insoybean (Glycine max L.) under aluminum stress

Abscisic acid (ABA) plays an important role in mediating some biotic and abiotic stresses. In the present study, to better understand the relationship of ABA production and Aluminum (Al)-resistance in plants, Al-resistance genotype (Jiyu70) of soybean was adopted to investigate the accumulation and transport of ABA in plants exposed to Al. Results showed that exogenous application of ABA and ABA synthesis inhibitor-fluridone respectively increased and reduced endogenous ABA content in root apices of soybean, and results in the corresponding reduction and aggravation of Al toxicity. Increasing of either Al concentration (0-50 mu M) or treatment duration (0-12 h, 30 mu M Al) cause a higher inhibition of root elongation and ABA accumulation in root apices of soybean. Al-induced enhancement of endogenous ABA production not only was in roots but also in leaves, whereas La3+ (behaves similarly as Al3+ at the level of cell surface) only increased ABA accumulation in roots. In split-root experiments, Al treatment in two parts of roots (Part A, + Al; Part B, + Al) both decreased root elongation and increased ABA accumulation in root apices of soybean. Whereas when only part A of roots was exposed to Al (Part A, + Al; Part B, -Al), endogenous ABA content in root apices increased in part A but inversely in part B, but root elongation inhibition only was found in part A. Using [H-3]-ABA radioisotope technique, it was found that [H-3]-ABA can transport at the rate of more than 3.2 cm center dot min(-1) in the whole plants, and this can be accelerated by Al supply. In addition, [H-3]-ABA tended to distribute in the root part under Al stress. Together, these results suggest that ABA may play an important role in regulating Al resistance of soybean as an Al-stress signal.