Revista Brasileira de Milho e Sorgo (Dec 2005)
PHENOLICS CONTENTS IN MAIZE ROOTS UNDER ALUMINUM TOXICITY
Abstract
Aluminum (Al) tolerance mechanisms proposed in the literature can beclassified as exclusion and internal tolerance mechanisms. Exclusion mechanisms preventthe Al from crossing the plasma membrane and penetrating the simplast. Internal tolerancemechanisms immobilize, compartmentalize or detoxify Al that penetrates the simplast.It has been suggested that phenolic compounds act in both mechanisms, due to its capacityto chelate metals as Al and to act as a strong antioxidant in response to abiotic stresses.The objective of this work was to identify differences in the content of total solublephenolics and phenolic acids (ferulic acid, 5-5‘diferulic and para-cumaric), bounded tothe cell wall of maize roots between inbred lines contrasting in their tolerance to Al,Cateto 237 (tolerant) and L53 (sensitive), when exposed to Al toxicity. Seedlings were cultivated in nutrient solution in the absence (0 h period) and presence of Al (AlK(SO4)2)39 μM activity (12, 24, 48 and 72 h period). Total soluble phenolics were analyzed bythe Prussian Blue method, and phenolic acids bounded to cell wall were analyzed byHigh Performance Liquid Chromatography (HPLC). Results obtained suggested thatphenolics may participate in Al tolerance mechanisms, considering that the tolerant inbredline Cateto 237 was capable of maintaining total soluble phenolics concentration, andincreased the concentration of ferulic, 5-5‘diferúlic and p-cumáric acids under Al toxicity
