The influence of different Al concentrations, (0, 60 and 120 μM Al) on growth and internal concentrations of Al, Si and selected organic acids was analysed in plants of teosinte (Zea mays L. ssp. mexicana), a wild form of maize from acid soils from Mexico. The plants were grown in nutrient solutions (pH 4.0) with or without 4 μM silicon. Analysis with the GEOCHEM speciation program did not reveal differences between free activities of Al3+ in solutions with and without 4 μM Si, but solutions with Si yielded lower concentrations of monomeric Al species, [Al]mono, when analysed by a modified aluminon method. Plants grown on solutions with similar [Al]mono, but differing in silicon, showed highly significant differences in growth and tissue concentrations of Al and organic acids. Silicon prevented growth inhibition at [Al]mono concentrations as high as 35 μM, while plants grown without Si suffered severe growth reductions with 33 μM [Al]mono. In solutions with similar [Al]mono concentrations plants with Si had lower tissue Al concentrations and higher concentrations of malic acid than plants without Si. In view of both the significant influence of Si on the response of plants to Al toxicity and the fact that some soluble Si is always present in soil solutions, the addition of low Si concentrations to nutrient solutions used for Al-tolerance screening is recommended. © 1993 Kluwer Academic Publishers.
- organic acids
- Zea mays L. ssp. mexicana