The effect of Lomax alone or in combination with castor oil on chlorophyll a fluorescence of common cocklebure (Xanthium strumarium L.)

To study the effect of castor oil combination with different doses of Lumax (mesotrion + s-metolacholor + terbuthylazine) on physiological behavior of common cocklebure (Xanthium strumarium L.), a greenhouse factorial experiment was conducted in randomized complete block design with 3 replications in Agricultural Faculty of University of Tabriz in 2017. Results showed that by increasing the herbicide doses, area above the OJIP curve between minimum and maximum fluorescence, maximum Fluorescence, variable fluorescence, maximum quantum yield of photochemistry (Fv/Fm), water-splitting complex on the donor side of PSII and maximum electron transport flux per PSII reaction center, decreased 35, 15/6, 23/6, 11, 43 and 83%, respectively and minimum fluorescence and thermal dissipation quantum yield increased 14 and 60%, respectively. Castor oil had synergistic effect on Lomax and enhanced its efficacy on X. strumarium. A good relationship was observed between Fv/Fm parameter evaluated 2 days after herbicide spraying (DAHS) and dry weight measured 28 DAHS. The finding of this study showed that evaluating chlorophyll a fluorescence is a good, non-destructive and fast to survey the effect of Lomax, soon after spraying and before the visual symptoms appear in treated weed species.