Phytotoxic property of imazosulfuron to rice [Oryza sativa] plants

The factors affecting the phytotoxicity of imazosulfuron on rice plants such as an application time, flooding water depth, temperature after application, water leaching and transplanting depth were studied under greenhouse conditions. Applications of imazosulfuron ranging from 75g a.i./ha to 150g a.i./ha caused no significant difference in dry weight of rice plants irrespective of variation in application time between 1 day and 13 days after transplanting or in flooding water depth between 1cm and 5cm. No significant reduction in dry weight of rice plants transplanted at a depth of -0.5cm or 2cm was recognized irrespective of temperature (20°C/13°C, 26°C/19°C, 32°C/25°C; day/night) after treatment application of 100g a. i./ha. There was no significant difference in dry weight between the -0.5cm and the 2cm transplanting depths under any temperature condition, although the dry weight of rice plants transplanted at the -0.5cm depth under the highest temperature was significantly different from the untreated control. When either basal leaf sheaths or root tips of the rice plants were exposed to 90g a.i./ha of imazosulfuron, the dry weights of the shoots were significantly different from untreated control. With water leaching at the rate of 2cm/day for 3 days after applications, the dry weight of rice plants transplanted at the 1cm depth, which was significantly different from the untreated control, was reduced more than those transplanted at the 3cm depth by application of 150g a.i./ha.