Figure 5.

Stimulation of ³²Pi uptake by excised corn roots promoted by AlF_x or Pi starvation. Four-day-old seedlings were transferred to a nutrient medium containing Pi and supplemented additionally with 0.1 mm AlCl₃ and 1 mm NaF (AlF_x treatment), or to nutrient medium lacking KH₂PO₄ (Pi starvation). Seedlings were removed at times indicated and excised root segments were assayed for ³²Pi uptake in the presence of 0.1 mm Pi. Stimulation of ³²Pi uptake was calculated as a percentage of uptake by roots grown in complete nutrient medium and tested in the presence of 0.1 mm Pi. Values represent the means ± se of three independent experiments. There is no significant difference between column pairs (Student's t test, P ≤ 0.05). From 12 h onward, Pi uptake for each treatment is significantly different from the relevant control (100%, not shown; Student's t test, P ≤ 0.05).