Aluminium long-term stress differently affects photosynthesis in rye genotypes

The ability of crops to overcome Al toxicity varies among crop species and cultivars. Among the Triticeae genus, rye (Secale cereale) is considered the most Al-tolerant species. In the present work, two rye genotypes differing in Al tolerance ('Riodeva': Al-sensitive and 'Donkowsky Zlote': Al-tolerant) were exposed to 1.11 and 1.85 mM Al during three weeks. Growth, water status and photosynthesis related parameters were assessed. After three weeks of Al exposure, both genotypes presented similar decrease in leaf growth. Al-induced RWC decreased in both genotypes, but was more remarkable in 'Riodeva'. Al toxicity induced a decrease in net photosynthetic rate only after three weeks of exposure. In 'D. Zlote', A decrease was accompanied by stomatal closure, Chl a content and q(p) reduction, but no alterations in RuBisCo or sFBPase activity were observed. In 'Riodeva' plants exposed to 1.11 mM Al, A decrease was accompanied by C(i)/C(a) increase whereas in plants exposed to 1.85 mM Al C(i)/C(a) was not affected. Nevertheless, for both conditions RuBisCo activity decreased. A decrease did not limited glucose accumulation in neither of the rye genotypes. This study revealed that Al-induced earlier damages in the 'Riodeva' genotype, but both genotypes showed long-term high susceptibility to Al. Furthermore, the photosynthetic parameters proved to be a good tool to monitor Al-sensitivity and long-term exposure showed to be crucial to evaluate Al-sensitivity.