Aluminum tolerance and aluminum-induced deposition of callose and lignin in the root tips of Melaleuca and Eucalyptus species

Abstract

We exposed the roots of nine Myrtaceae species (Melaleuca bracteata F. Muell., Melaleuca cajuputi Powell, Melaleuca glomerata F. Muell., Melaleuca leucadendra [L.] L., Melaleuca quinquenervia [Cav.] S.T. Blake, Melaleuca viridiflora Sol. ex Gaertner, Eucalyptus camaldulensis Dehnh., Eucalyptus deglupta Bl., and Eucalyptus grandis W. Hill ex Maiden) to 1mM Al in a nutrient solution for either 24h or 20 days to evaluate their sensitivity to excess Al and to determine whether callose and lignin formation can be used as interspecific indicators of Al sensitivity. Inhibition of root elongation by Al varied among the species. Melaleuca leucadendra, M. cajuputi, E. grandis, M. quinquenervia, and E. deglupta were tolerant to 1mM Al, whereas M. viridiflora, E. camaldulensis, M. glomerata, and M. bracteata were sensitive to 1mM Al. We found that Al induced callose formation in the root tips of each species, but lignin was formed only in the root tips of the most sensitive species, M. bracteata. Root elongation at 1mM Al was negatively correlated with Al-induced callose formation but not with the Al-induced lignin formation in the root tips. These results suggest that Al-induced callose formation, rather than lignin formation, can be used as an interspecific indicator of Al sensitivity.

Key words:

• Aluminum toxicity
• Indicator of aluminum sensitivity
• Root elongation
• 1,3-β-d-glucan
• Myrtaceae