In the rice paddy ecosystem, naproanilide is
biodegraded by the rice plant and organisms in the
paddy field and by soil organisms and is mainly
hydrolyzed to 2-(2-naphthoxy)propionic acid (NOP)
and its methyl ester (NOPM). In rice plants (Oryza
sativa L.) and Sagittaria pygmaea MIQ, naproanilide is
metabolized to phytotoxic NOP. In rice plants, NOP
subsequently undergoes hydroxylation and rapid
conjugation with glucose. Phytotoxic NOP is produced
only in a small amount. In S. pygmaea, the amounts
of NOP and NOPM are significantly greater than those
in rice plants. The difference in metabolites of
naproanilide shows a possible mechanism of their
herbicidal selectivity. Naproanilide and NOP in
aqueous solution are rapidly degraded under sunlight and UV light. The disappearance of naproanilide in the
paddy field is largely attributed to photochemical
degradation in the surface water.
