Uptake of the Fresh and Aged Residues of Carbofuran by Rice Plants from Soil

침투성(浸透性) 살충제(殺蟲劑) Carbofuran 토양(土壤) 잔류물(殘留物)의 벼에 의(依)한 흡수(吸收)

In order to investigate the uptake of the systemic insecticide, carbofuran, 2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methyl(arbamate) residues, fresh and aged, by rice plants, they were grown for 42 days in soils containing freshly treated (T-1), 3-month-aged (T-2), and 6-month-aged residues (T-3). The amounts of $^{14}CO_2$ evolved from $^{14}C-carbofuran$ during the 3-and 6-month aging in soil (temp. $22{\pm}1^{\circ}C$ ; moisture, 50% of the maximum water-holding capacity) were 8.9 and 26.7% of the original radioactivity applied, respectively. Mineralization of $^{14}C-carbofuran$ in soil to $^{14}CO_2$ during 42 days of rice growing was 4.4% (T-1), 11.0% (T-2), and 15.7 (T-3). The methanol extract of the 3-and 6-month-aged soils revealed that 3-keto carbofuran phenol (2,3-dihydro-2,2-dimethyl-3-oxo-7-benzofuranol) was the major metabolite, where as 3-hydroxy carbofuran (2,3-dihydro-2,2-dimethyl-3-hydroxy-7-benzofuranyl-N-methylcarbamate) turned out to be the major metabolite in the shoots by the enzymatic cleavage of the possible conjugate present in the methanol extract. Volatilization of $^{14}C-carbofuran$ in soil during 3-and 6-month-aging, and 42 days of rice growing was 0.026, 0.05, and 0.012-0.018% of the applied radioactivity, respectively. The $^{14}C-radioactivity$ which was absorbed from the soils by rice plants during 42 days of the growing period and persisted in rice plant tissues was 26.8, 21.4, and 10.3% in T-1, T-2, and T-3, respectively. The non-extractable bound residues were 8.3, 37.9, and 54.6% of the originally applied carbofuran in T-1. T-2, and T-3, respectively. The small translocation of $^{14}C-radioactivity$ in T-3 upwards suggests that major metabolite 3-keto carbofuran phenol is conjugated in roots and the low recovery in T-1 indicates the loss of carbofuran from the shoots.

침투성 살충제 Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-lcarbamate)의 신생 (Fresh) 및 숙성 (Aged) 잔류물의 벼에 의한 흡수를 구명하기 위하여 벼 재배 직전에 Carbofuran을 처리한 토양(T-1), Carbofuran 을 처리하고 3개월간 숙성시킨 토양 (T-2) 및 Carbofuran 처리 후 6개월간 숙성시킨 토양 (T-3)에서 벼를 재배하였다. 토양(온도 $22{\pm}1^{\circ}C$ 최대 용수량의 50% 수분함량) 중에서 3개월 및 6개월간 숙성시키는 동안 $^{14}C-Carbofuran$ 으로 부터 방출된 $^{14}CO_2$의 량은 최초 처리량의 각각 8.9%와 26.7% 이 었다. 42일간 벼를 재배하는 동안 방출된 $^{14}CO_2$의 량은 4.4%(T-1), 11.0%(T-2) 그리고 15.7%(T-3)이었다. 3개월과 6개월간 숙성시킨 토양을 MeOH로 추출하여 Autoradiograph를 행한 결과 주대사 산물이 3-keto Carbofuran phenol(2,3-dihydro-2,2-dimethyl-3-oxo-7-benzofuranol)이었고 벼를 MeOH로 추출하고 Autoradiography를 행한 결과 3-hydroxy Carbofuran(2,3-dihydro-2,2-dimethyl-3-hydroxy-7-benzofuranyl-N-methylcarbamate) 이 주 대사산물로 판명되었다. 3개월과 6개월의 숙성 기간과 42일간의 벼 재배 기간중 토양의 $^{14}C-Carbofuran$ 으로부터 휘발된 량은 최초 처리량의 각각 0.026, 0.05, 그리고 0.012-0.018 %이었다. 42일간의 벼 재배 기간중 벼에 의하여 토양으로 부터 흡수 이행되고 잔류해 있는 $^{14}C$방사능의 량은 최초 방사능의 각각 26.8%(T-1), 21.4%(T-2), 그리고 10.3%(T-3)이었다. T-1, T-2 및 T-3 에서의 추출 불가 토양 잔류물의 량은 최초 처리 Carbofuran의 8.3%, 37.9% 그리고 54.6%이었다. T-3에서 $^{14}C$ 방사능이 지상으로 소량 이행된 것은 주 대사산물인 3-keto Carbofuran phenol이 뿌리에서 Conjugate를 형성했기 때문이며 T-1에서 특히 회수율이 낮은 것은 벼 조직의 표면으로부터 Carbofuran 이 휘발되었기 때문이라 생각된다.