Chlorophyll a fluorescence of redroot pigweed (Amaranthus retroflexus L.) in response to mixture of Bromicide AM with Ammonium Sulphate, Cytogaite and Salicylic acid

To evaluate the effects of bromicide AM (bromoxynil + MCPA)alone or mixed by salicylic acid, cytogaite, and ammonium sulphate on chlorophyll a</em> fluorescence (ChlF) of redroot pigweed (Amaranthus retroflexus </em>L.), a greenhouse experiment was conducted in randomized complete block design with three replications in Agricultural Faculty of University of Tabriz in 2017. Bromicide AM, 16 hours after application, increased minimum fluorescence (F0</sub>) 84%, thermal dissipation quantum yield (F0</sub>/Fm) 89% and the rate of accumulation of closed reaction centers (∆V/∆to</sub>) 59% and decreased maximum fluorescence (Fm) 40%, maximum quantum yield of photochemistry (Fv/Fm) 71%, electron transport yield (φEo</sub>) 94%, normalized area (Sm) 97% and time needed to reach Fm (Tfm) 89%. Salicylic acid as a growth regulator had not negative effect on the efficacy of bromicide AM. 64 hours after herbicide application, synergistic effect on bromicide AM ammonium sulphate and cytogaite reduced 52% and 45% Fm, 62% and 37% Fv/Fm, 25% and 11% Fv/ F0</sub>, and enhanced 6% and 3.5% F0</sub>/Fm, 72% and 25% specific fluxes expressed per reaction centers (ABS/RC), 83% and 30% ratio – flux of dissipated energy per reaction center in t = 0, respectively. Results showed that assessment of chlorophyll a</em> fluorescence is a rapid and non-destructive technique for detecting photosynthetic apparatus response of plant to applied herbicide alone and or mixing with adjuvants.