Photosynthetic inhibition and ammonium accumulation in Palmer amaranth after glufosinate application

Abstract

Greenhouse experiments were conducted to determine the effects of glufosinate on ammonium accumulation and photosynthetic inhibition in Palmer amaranth. Glufosinate applied at 410 g ha−1 reduced glutamine synthetase activity and enhanced ammonium content 30 min after treatment. Glufosinate application resulted in rapid inhibitions of the photosynthetic rate and stomatal conductance during the first 2 h after treatment (HAT), whereas the ammonium concentration increased over the same time period. Ammonium content 6 HAT was 22 times higher in treated plants than in untreated plants, whereas the photosynthetic rate of treated plants decreased by 63%. At 24 HAT, the ammonium content was 53 times higher in treated plants than in untreated plants; however, no further inhibition of photosynthesis occurred. Photosynthetic inhibition in Palmer amaranth coincided with the rapid accumulation of ammonium and decrease in stomatal conductance shortly after glufosinate application.