Atrazine Metabolism in Resistant Corn and Sorghum

Abstract

Abstract. The metabolism of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) in the resistant species, corn (Zea inays L.) and scrghum (Sorghum vulgare Pers.) was not the same. In corn, atrazine was metabolized via both the 2-hydroxylation and N-dealkylation pathways while sorghum metabolized atrazine zvia the N.dealkylation pathway. Atrazine metabolism in corn yielded the metabolites, 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine (hydroxyatrazine), 2-hydroxy-4-amino-6-isopropylamino-s-triazine (hydroxycompound I), and 2-hydroxy-4-amino-6-ethylamino-s-triazine (hydroxycompound II). None of these hydroxylated derivatives appeared as metabolites of atrazine in sorghum.Hydroxycompounds I and II were formed in 2 ways in corn: (1) by benzoxazinone-catalyzed hydrolysis oif 2-chloro-4-amino-6-isopropylamino-s-triazine (compound I) and 2-chloro.4-aminc-6-ethylamino-s-triazine (compound II) that were formed by N.deadkylation of atrazine and (2) by N-dealkylation of hydroxyatrazine, the major atrazine metabolite in corn. The interaction of the 2-hydroxylation and N-detilkylation pathways in corn results in the formation of the 3 hydroxylated non-phytotoxic derivatives of atrazine.Metabolism of 2-chloro-4-ethl-laiinio-6-isopropylamiiino-s-triazine (atrazine) in hligher plants was shown to be an important factor in herbilcidal selectivity. Detoxication of atrazine was reported to occur via the 2-hydroxylation and N-dealkylation pathways in higher plants (12). Corn is resistant to atrazine and 2-chloro-4,6-bis (ethylamino) -s-triazine (simazine) largely because of its ability to convert the 2 herbicides rapidly to non-phytotoxic, 2-hydroxv -4 -ethylamino-6-isopropyl-amino-s-triazine (hydroxyatrazine), and 2-hydroxy-4,6-bis (ethylamino)-s-triazine (hydroxysimazine) (1,2,5,10,12). The conversion of the 2-chlorotriazines to their 2-hydroxy derivatives is catalyzed non-enzymatically by a cyclic hydroxamate, 2,4-dihydroxy-3-keto-7-methoxy-1,4-benzoxazine (benzoxazinone) present in corn plants ( 1, 5, 9). The hydroxylation reaction appears to be correlated with the presence of benzoxazinone in different species (4,12). N-Dealkylation of atrazine occurred in higher plants to form 2-chloro-4-amino-6-isopropylamino-striazine (compound I) and 2-chloro-4-amino-6-ethylamino-s-triazine (compound II) (12,13,14). In resistant sorghum, only the N-dealkylation pathway was reported to be active, but in, corn both hydroxylation and N-dealkylation pathways were active.Autoradiographic evidence indicated that after a 48-hr atrazine treatment period, corn and sorghum yielded at least 1 common water-soluble metabolite of atrazine, but corn produced 2 other metabolites, neither of which was hydroxyatrazine (12).Hydroxylation of compounds I and II to fornm hydroxycompounds I and II (fig 1) is pos-sible in benzoxazinone-containing corn, but not in sorghum. N-Dealkylation of hydroxvatrazine (fig 1) could also occuir in corn to give hydroxyconu ounds I ande II. Such a reaction would not occur in sorghumi since atrazin.e is not conve...

HETEROGENEOUS PHOTO-FENTON REACTION OF A HERBICIDE ATRAZINE BY USING Fe(III)-TREATED HYDROXYAPATITES

“…[1][2][3][4] Although usage of ATZ has merits for enhancing grow and amount of crops and for facilitating being in good states of ground surfaces, relatively high chemical and biological stability of ATZ in soils and aquifers [5][6][7][8] potentially affords negative effect to crop contamination, 9 aquatic ecosystems, 10,11 and human health. [12][13][14][15] For keeping safety of natural waters, it is important to control ATZ usage amount 16 and to remove ATZ from natural waters.…”

Growth responses of inbred maize lines with high and low DIMBOA (benzoxazinone) contents to atrazine

“…Significant differences in the concentration of DlMBOA were found to exist between 27 maize inbred lines (Malan, Visser & van de Venter, in press)_ The non-enzymatic hydroxylation of atrazine in the presence of DlMBOA (Hamilton, 1964;Shimabukuro, 1967;1968) is the main detoxifying mechanism in the roots of maize plants (Shimabukuro et al, 1970), implying a certain threshold DIMBOA concentration, below which damage owing to unmetabolized atrazine could occur_…”

Screening for DIMBOA (benzoxazinone) concentration among South African inbred maize lines and sorghum cultivars

“…N-dealkylation is responsible for the detoxification of a small percentage of atrazine in maize plants, whilst glutathione (peptide) conjugation represents the main detoxifying mechanism in leaves of maize plants (Shimabukuro, 1967;1968;Shimabukuro & Swanson, 1969;Shimabukuro et al_ 1970).…”

“…Hydroxylation of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in the presence of DIMBOA (benzoxazinone) (2,4-dihydroxy-7 -methoxy-l ,4-benzoxazine-3-one) or its 2-glucoside to hydroxyatrazine, is the main detoxifying mechanism of the roots of pre-emergence treated maize plants (Shimabukuro, 1967;1968;Shimabukuro, Swanson & Walsh, 1970). N-dealkylation is responsible for the detoxification of a small percentage of atrazine in maize plants, whilst glutathione (peptide) conjugation represents the main detoxifying mechanism in leaves of maize plants (Shimabukuro, 1967;1968;Shimabukuro & Swanson, 1969;Shimabukuro et al_ 1970).…”