Could the absence of aluminum (Al) impair the development of an Al-accumulating woody species from Brazilian savanna?

Vochysia tucanorum (Vochysiaceae) is an aluminum (Al)-accumulating tree species from the Cerrado vegetation in South America, known as `Brazilian savanna'. In the field, it may accumulate up to 20,000 mg Al kg(-1) dry leaf mass. The soils of this vegetation are acidic (pH < 5.0) with Al saturation higher than 70%, where trees of this species grow well under Al toxicity. However, what would happen if the Al disappeared from the root environment of this species? V. tucanorum seedlings were grown in pots with Cerrado soil and, after exhibiting about ten leaves, they were transferred to nutrient solution with 0 and 1110 mu M Al (30 mg L-1) for 60 days. Hypothesizing that their development and photosynthetic performance would be affected, plant biomass, biometric data, leaf gas exchange rates and photochemical parameters were assessed. After seven days in nutrient solution without Al, the plants did not produce new roots, and pre-existing roots became necrotic when compared to those exposed to Al. Until 60 days, plants not exposed to Al stopped growing, showed leaf chlorosis and shed their leaves. While plants exposed to Al showed healthy leaves and roots, increased their root length and biomass and maintained high gas exchange rates and photochemical performances, plants without Al decreased CO2 assimilation rates, explained by low stomatal conductance. This preliminary study suggests the roots as the first organ to sense the lack of Al, and the dysfunction of this organ to absorb water could explain their low photosynthetic responses. Further investigation in this regard is needed. (AU)