Table I.

Root malate and phosphate exudation rates and root tip content for seedlings of the Al-tolerant maize cv Cateto-Colombia, exposed to different Al³⁺ activities

Al3+ Activity	Exudation Rate		Root Tip Content
	Malate	Phosphate	Malate+Phosphate
μm	nmol h−1 root−1		nmol g−1
0	0.15 ± 0.04	0.07 ± 0.02	9,140 ± 1,346
5	0.04 ± 0.01	0.06 ± 0.02	6,243 ± 1,228
10	0.15 ± 0.07	0.04 ± 0.00	5,955 ± 803
20	0.28 ± 0.07	0.05 ± 0.01	6,425 ± 130
40	0.27 ± 0.21	0.13 ± 0.08	5,648 ± 215
80	0.08 ± 0.07	0.17 ± 0.12	4,038 ± 397