Differential aluminium changes on nutrient accumulation and root differentiation in an Al sensitive vs. tolerant wheat

Aluminium (Al) toxicity is particularly evident under acid soil conditions limiting crop production, namely in wheat (Triticum aestivum). Although largely studied, the effects of Al on nutrition imbalances and putative correlations with Al tolerance degrees still remain inconclusive. We investigated the uptake of Al and transport to shoots in one wheat line and one cultivar differing in their tolerance to Al: ‘Barbela 7/72’ (Al-tolerant) and ‘Anahuac’ (Al-sensitive). Wheat seedlings were exposed for a short period to 185 μM AlCl3 and then grown in the absence of the metal. In general, Al inhibited root growth, mostly in the sensitive cultivar ‘Anahuac’, while water content decreased and organic matter increased in ‘Barbela 7/72’ line. Similar but less evident effects were found in leaves of both genotypes. The profiles of macro- (Ca, K, P, Mg) and micronutrients (Mn, Fe, Zn, B, Cu) accumulation in response to aluminium were analyzed in both genotypes: Al levels increased, mostly in ‘Anahuac’ cultivar. Overall, P, Mg and K levels decreased and Si and Ca increased in roots of both genotypes, while other nutrients had a more inconsistent behaviour. Histological data showed that ‘Barbela 7/72’ initiated endodermis differentiation more efficiently than ‘Anahuac’, at the hairy root zone. These data show that: (a) Al negatively interferes with P, Mg and K in wheat and (b) Al interactions with some nutrients depend on the level of plant tolerance. Finally, data also provide support to the hypothesis that endodermis differentiation may be stimulated limiting Al accumulation/allocation in roots of the tolerant wheat landrace.