Exogenous indole-3-acetic acid could reduce the accumulation of aluminum in root apex of wheat (Triticum aestivum L.) under Al stress

Abstract

Indole-3-acetic acid (IAA) is hormones in higher plants and participates in plant growth regulation and stress resistance including Al stress. The reduction of root apex aluminum (Al) content by exogenous IAA treatment was hypothesized to be effective in alleviating the adverse effect of high Al concentration in wheat root growth. To investigate the role of IAA in lowering root apex Al content, Al-tolerant wheat (ET8) was studied in Al solution (50 µM), co-treated with IAA (25 µM) and anion channel inhibitors (5 µM NIF or A9C) or IAA transport inhibitors (5 µM TIBA or NPA) under acidic condition for 24 h. Treatments were as fellows: control (0.5 µM CaCl 2 ), Al (50 µM), Al (50 µM) + IAA (25 µM), Al (50 µM) + IAA (25 µM) + NIF (or A9C, 5 mM), Al (50 µM) + NPA (or TIBA, 5 µM). Al content in root apex, rhizosphere pH and PM H + -ATPase activity were studied. The results showed that co-treatment with IAA reduced root apex Al content by 42% compared to Al treatment. Anion channel inhibitors enhanced the accumulation of Al in root apex by 27% (or 32%) (NIF or A9C), while addition of IAA neutralized its promoting effect. The co-treatment with IAA increased rhizosphere pH by alleviating the decrease of plasma membrane H + -ATPase activity, while IAA transport inhibitors (NPA or TIBA) suppressed the elevation of rhizosphere pH. The current results suggested that IAA could be effective in alleviating Al toxicity through reducing Al accumulation in wheat root apex.