Effects of EPTC, fluorodifen and monuron on transpiration and photosynthetic oxygen output in Eupatorium odoratum plants

The influence of foliar sprays of EPTC, fluorodifen and monuron on transpiration and photosynthetic oxygen output of Eupatorium odoratum plants is demonstrated. Foliar sprays with 100 ppm EPTC or monuron led to a significant decrease in transpiration for a continuous period of 14 days. Treatment with 100 ppm fluorodifen led to a noticeable increase in transpiration during the first eight days. All three herbicides significantly reduced photosynthetic oxygen output from the Eupaiorium plants. EPTC and monuron however, gave greatest effect. Reduction in transpiration from the plants was due to stomatal closure while reduction in photosynthetic oxygen output was due to both stomatal closure and probably also inhibition of the Hill reaction.