Accumulation of nitrogen supplied as ammonium in the root tips of aluminum-stressed wheat cultivars differing in aluminum sensitivity

Ammonium labeled with N-15 was supplied for two days to two wheat (Triticum aestivum L.) cultivars treated with Al. At a low Al concentration, root el ongation was greatly inhibited by treatment for 24 hours in cultivar Chikus hikomugi, while in cultivar Shirosanjyaku, significant inhibition of root e longation required treatment for 48 hours. Decreases in pH values of nutrie nt solution were greater in Shirosanjyaku than Chikushikomugi and smaller a t a higher Al concentration in both the varieties. These results indicate t hat uptake of ammonium was more strongly inhibited by Al in Chikushikomugi than Shirosanjyaku. Accumulation of newly absorbed nitrogen (N-15) was decr eased at a low Al concentration in the apical part of root tip (0-12 mm) of Chikushikomugi. In Shirosanjyaku treated with a low concentration of Al, a ccumulation of N-15 increased rather than inhibited. At a high Al concentra tion, accumulation of N-15 Slightly decreased in the root tip of Skirosanjy aku. Accumulation of N-15 in four segments dissected from a root tip was di fferently affected between Shirosanjyaku and Chikushikomugi. It is consider ed that Shirosanjyaku is able to maintain active nitrogen metabolism in the root tip under Al-stress conditions compared to Chikushikomugi.