Aluminium-inhibited NO ₃^- uptake is related to Al-increased H ₂ O ₂ content and Al-decreased plasma membrane ATPase activity in the root tips of Al-sensitive black soybean

In this study, Al-sensitive black soybean (Glycine max (L.) Merr.) specimens were treated in Hoagland solutions containing 50-400µM Al for 1-4 days. The measurement for NO3- uptake showed that the NO3- uptake decreased gradually as the Al concentration and treatment time increased, suggesting that Al stress significantly reduced the NO3- uptake by soybean. Under 100-µM Al stress for 4 days, the plasma membrane (PM) ATPase activity (inorganic phosphate (Pi) release), H+ pump activity, phosphorylation of PM ATPase and its interaction with 14-3-3 protein in soybean root tips were all smaller than those in the root tips of control plants. The addition of 150µM Mg2+ in Al treatment solutions significantly alleviated the Al inhibition of NO3- uptake in soybean. The presence of Mg2+ in a 100-µM Al solution pronouncedly enhanced PM ATPase activity, H+ pump activity, phosphorylation of PM ATPase and its interaction with 14-3-3 protein in soybean root tips. The application of 2mM ascorbic acid (AsA, an H2O2 scavenger) in Al treatment solutions significantly decreased Al-inhibited NO3- uptake in soybean. The cotreatment of soybeans with 2mM AsA and 100µM Al significantly reduced H2O2 accumulation and increased the PM ATPase activity, H+ pump activity, phosphorylation of PM H+-ATPase and its interaction with 14-3-3 protein in soybean root tips. The evidence suggested that Al-inhibited NO3- uptake is related to Al-increased H2O2 content and Al-decreased phosphorylation of PM ATPase and its interaction with 14-3-3 protein as well as PM ATPase activity in the root tips of soybean.