Effect of electron transport rate on sugarcane submitted to pre-emergence application of atrazine and tebuthiuron

The objective of this work was to assess the photosynthetic efficiency of sugarcane crop, in pre-emergency application, of two herbicides inhibiting photosynthesis. For sugar cane cuttings planting (variety SP80-3280), pots with a capacity of 8 dm3 were used. Atrazine and tebuthiuron application was performed by using a stationary spray installed in laboratory conditions and after treatment application, plants were transported to a green house where were kept until the end of the trial. The reading of transport rate (ETR) was conducted in the middle portion of the youngest leaves of sugarcane with a portable fluorometer, with intervals for ETR assessment constituted by: 16, 17, 19, 25 and 30 days after herbicide application. It was also realized visual analysis of phytotoxiciy performed 30 days after application. The results showed that tebuthiuron herbicide caused greater reduction in the rate of electron transport than atrazine. In relation to herbicide symptoms, there was no significant difference between the studied herbicides. At the end of the work it could be verified that the chosen method using fluorometer to measure the rate of electron transport after herbicide application was adequate, allowing verifying sugar cane crop intoxication, even before any visual detection of herbicides performance in plants.