Genotypic variation in aluminum resistance, cellular aluminum fractions, callose and pectin formation and organic acid accumulation in roots of Populus hybrids

• Published in: Environmental and experimental botany Vol. 72; no. 2; pp. 182 - 193
• Main Authors: Smith, Ernest, Naik, Dhiraj, Cumming, Jonathan R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2011; Elsevier
• Subjects: Acidity; Aluminum tolerance; Aluminum tolerance, Aluminum toxicity, Organic acids, Poplar, Callose, Pectin; Aluminum toxicity; Biological and medical sciences; Callose; ENVIRONMENTAL SCIENCES; Fundamental and applied biological sciences. Psychology; Organic acids; Pectin; Poplar; Populus; Poplar; Pectin; Aluminum toxicity; Aluminum tolerance; Organic acids; Callose; Genetic variability; Toxicity; Plant ecology; Hybrid; Tolerance; Aluminium; Accumulation; Salicaceae; Resistance; Phytotoxicity; Dicotyledones; Angiospermae; Botany; Tree; Spermatophyta; Populus; Formation
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2011.03.003

► Aluminum resistance in hybrid poplar varies by genotype and hybrid cross. ► Resistant genotypes exclude Al from the symplast, but accumulate Al in the apoplast. ► Sensitive genotypes exhibit elevated cell wall callose and pectin upon Al exposure. ► Al sensitive genotypes accumulate high concentrations of organic acids in roots. Soil acidity and aluminum (Al) toxicity are major factors limiting crop yield and forest productivity worldwide. Hybrid poplar ( Populus spp.) was used as a model to assess genotypic variation in Al resistance and physiological stress responses to Al in a woody tree species. Eight hybrid crosses of P. trichocarpa, P. deltoides and P. nigra were exposed to Al in solution culture. Resistance to Al varied by genotype and hybrid cross, with P. trichocarpa × P. deltoides crosses being most resistant, P. trichocarpa × P. nigra being intermediate and P. deltoides × P. nigra being most sensitive to Al. Total root Al accumulation was not a good indicator of Al resistance/sensitivity. However, the partitioning of Al into apoplastic and symplastic fractions indicated that differences in sensitivity among genotypes were associated with Al uptake into the symplasm. Aluminum treatment increased callose and pectin concentrations of root tips in all genotypes, but more prominently in Al sensitive genotypes/hybrids. In Al sensitive genotypes, higher levels of symplastic Al accumulation correlated with elevated concentrations of citrate, malate, succinate or formate in root tips, whereas organic acid accumulation was not as pronounced in Al resistant genotypes. These findings suggest that exclusion of Al from the symplast is associated with Al resistance. Further screening of Al tolerant poplar genotypes could yield successful candidates to be utilized for sustainable reforestation/reclamation and carbon sequestration projects where soil acidity may limit tree growth.