The aluminium response network inThemeda triandraFosk. III: Regulatory mechanisms and aluminium tolerance

Aluminium toxicity was investigated by analyzing the reaction of hydroponically-grown plants of two ecotypes of T. triandra to Al (0, 25, 50, 100 μM; pH 4.1; for 28 days). The Al-tolerant 'Berg ecotype responded to the Al treatments by increasing root extension growth, D.M. production and they also controlled water-use over the full range of Al stresses. In contrast, Al inhibited root growth and D.M. production in the Al-sensitive Zululand ecotype and they also failed to control water-use at 100 μM Al. Microscopical investigation showed that the root cells of both ecotypes were generally resistant to Al with cellular disorganization being confined to the Zululand plants at the highest Al stress. The root caps of both ecotypes responded to Al in ways (amyloplast numbers, cap volume, secretions) which coincided with the contrasting growth responses observed in 'Berg and Zululand plants. Aluminium tolerance involved the accumulation of Al in the roots of 'Berg plants and was coincident with increases in root...