The determination of activity of the phenylalanine ammonia-lyase (FAL) was conducted by colorimetric quantification of the transcinnamic acid released from the substrate phenylalanine,according to the methodology described by KUHN
(2007), where we used a sample of the leaves of each experimental unit, placed it in a porcelain pot and macerated with more 3.0 mL of buffer TRIS – HCl pH 8.0. This extract was conditioned in eppendorf tubes,properly marked and taken to the centrifuge for 10 minutes, at 4ºC and 6000 rpm. After, we transferred an aliquot of 200 μL to an identified test tube, adding more 3.0 mL of extraction buffer. The solution was stirred, obtaining, thus, the enzymatic extract. Of this extract, 1.5 mL was transferred to another test tube, with more 1.0 mL of extraction buffer and 0.5 mL of phenylalanine. Again, this solution was stirred for the homogenization. And after, the tubes were incubated in Bain Marie for 45 minutes at 40ºC. After removing from the Bain Marie, the tubes were placed in ice bath for 5 minutes in order to interrupt the reaction and thus be able to conduct the reading through the spectrophotometer at 290 nm.