Soil conditions and evolution of aluminium resistance among cultivated and wild plant species on the Island of Madeira

Soil samples collected from different soil formations throughout the Island of Madeira were analysed for pH, aluminium and organic matter content. On average, the Madeira soils appeared to be acid with a mean pH of 5.01, containing 0.79 cmol/kg of ionic Al and 3.02% organic matter, which may create favourable conditions for the development of Al resistance among plant species inhabiting the island. Six plant species were evaluated for their resistance to Al using the erichrome cyanine R tests: three agricultural species: Triticum aestivum, Triticum turgidum and Zea mays, and three wild species from the genus Sinapidendron. Profound differences in adaptation to local edaphic parameters (Al content, acidity, organic matter, altitude) between cultivated and wild species were observed. Comparison of the distribution patterns of the cultivated and wild species on the island may indicate that the anthropogenic activities played a pivotal role in the development of enhanced Al resistance among the cultivated species, while edaphic conditions seem to be a secondary factor.