Detoxification of Atrazine in Three Gramineae Subfamilies

Abstract

Inhibition and subsequent recovery of net CO2exchange (NCE) by single leaves of 53 grass species of the subfamilies Festucoideae, Panicoideae, and Eragrostoideae was monitored following limited root uptake of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Rates of NCE recovery were correlated with rates of14C-atrazine metabolism in leaf sections of festucoid and panicoid grasses but not eragrostoid grasses. Rates of NCE recovery among the nine festucoid and 12 eragrostoid species tested did not exceed 0.2 and 1.1 mg CO2per dm2per hr/hr, respectively, whereas for the 31 panicoid species, it ranged from 0.2 to 2.4 mg CO2per dm2per hr/hr. Selected species exhibiting NCE recovery rates exceeding 1.2 mg CO2per dm2per hr/hr were tolerant to 1.0 kg/ha preemergence and 1.25 kg/ha postemergence atrazine applications. These panicoid species included a number of common weed species belonging to the generaDigitaria, Panicum, andSetaria, as well as species belonging toBracharia, Pennisetum, Sorghum, andZea.Unchanged14C-atrazine accounted for 11.3 to 92.7% of the total14C-radioactivity extracted from14C-atrazine infiltrated leaf sections following an 8-hr incubation period. N-dealkylation, hydroxylation, and peptide conjugation occurred in all species, although rates of these metabolic pathways varied widely among species. Recovery of NCE was correlated with formation on the glutathione-atrazine conjugate, and conjugation was the major detoxification pathway in species exhibiting tolerance to atrazine.

Recovery of duckweed from time‐varying exposure to atrazine

“…Photosynthesis, measured as the rate of CO 2 uptake, was found to recover gradually in maize after being removed from simazine exposure [4]. These results were further verified in several grass species exposed to atrazine by measuring CO 2 uptake in whole leaves [6]. These results were further verified in several grass species exposed to atrazine by measuring CO 2 uptake in whole leaves [6].…”

Spatial and temporal variation of algal assemblages in six Midwest agricultural streams having varying levels of atrazine and other physicochemical attributes

“…Atrazine acts by inhibiting photosystem-II of photosynthesis through competitive and noncovalent binding of the QB site of the D1 protein (Jensen et al, 1977;Jursinic and Stemler, 1983;Shimabukuro et al, 1970). Consequently, inhibition is reversible immediately upon removal of atrazine, and recovery of both terrestrial and aquatic plant communities under a variety of conditions has been demonstrated (Jensen et al, 1977;Shimabukuro et al, 1970;Klaine et al, 1996;Brain et al, 2012aBrain et al, , 2012bBrockway et al, 1984;Hughes et al, 1988;Jones et al, 1986;Juttner et al, 1995;Teodorović et al, 2012;Mohammad et al, 2008Mohammad et al, , 2010Stay et al, 1989;Vallotton et al, 2008). In a variety of algal species, both biochemically and physiologically, recovery of photosynthesis and growth rate occur immediately, reaching control levels within hours following exposure to atrazine at concentrations much higher than typically encountered in situ (250-1000 μg/L) (Vallotton et al, 2008;Brain et al, 2012aBrain et al, , 2012bHughes et al, 1988).…”

Sensitivity of a green alga to atrazine is not enhanced by previous acute exposure

“…Atrazine inhibits photosynthesis by blocking the flow of electrons between photosystem II (PSII) and plastoquinone (Forney and Davis, 1981); however, the binding interaction is competitive, noncovalent, and reversible (Jensen et al, 1977;Jursinic and Stemler, 1983). Consistent with the mode of action, several studies have documented rapid recovery of aquatic plants from atrazine exposure when it is removed from the aquatic medium (Brain et al, 2012;Hughes et al, 1988;Vallotton et al, 2008).…”