تأثیر فرمولاسیون‌های علف‌کشی دیالن، آتلانتیس و توتال بر پارامترهای مختلف فلورسانس کلروفیل علف‌هرز قاصدک (Taraxacum syriacum Boiss.)

Abstract
Considering the effect of stresses on photosynthesis, the investigation of chlorophyll fluorescence in plants is very important to evaluate the effect of herbicides on plants. This experiment was also conducted in order to study the effects of Dylan, Atlantis and Total herbicides on the dandelion fluorescence system in the green space of the Faculty of Agriculture and Natural Resources of Mohaghegh Ardabili University in 2021 For this purpose, different doses (0, 0.5, 1 and 2 times the recommended dose) of the herbicides Dylan, Atlantis and Total were applied. Fluorescence of dandelion was measured.1, 2, 3, 5, 7, 10 and 14 days after treatment with herbicides with a portable fluorometer. The results showed that Dylan and Atlantis reduced maximum fluorescence more severe than Total and irreversible. The application of high dose of Atlantis reduced the variable fluorescence of dandelion by 46% compared to the control. Also, the dry weight of dandelion decreased under the influence of different herbicide treatments compared to the control. The amount of reduction in the herbicide treatment of Dylan and Atlantis was more than total. In these herbicides, the dry weight of dandelion was 50% less than the control.
Introduction
Herbicides are one of the most effective agricultural tools in the fight against weeds, and the use of these chemicals has increased significantly in recent years, especially in developed countries in the field of agriculture. It is necessary to use non-destructive and high-speed methods to accurately and quickly investigate the effects of herbicides on plants and identify their mechanisms of action. Evaluation of chlorophyll a fluorescence is a quick and non-destructive method to determine the state of the plant's photosynthetic system in response to various stresses, such as herbicide stress. Chlorophyll a transfers the energy received from the light photon to the reaction center and these interactions cause the electron transfer chain to start in the chloroplast. Considering the effect of stresses on photosynthesis, the investigation of chlorophyll a fluorescence in plants is very important to evaluate the effect of herbicides on plants.
Materials and methods
This experiment was also conducted in order to study the effects of Dylan, Atlantis and Total herbicides on the dandelion fluorescence system in the green space of the Faculty of Agriculture and Natural Resources of Mohaghegh Ardabili University in 2020  in the form of a basic randomized complete block design with 3 replications. Different doses (0, 0.5, 1 and 2 times the recommended dose) of Dylan, Atlantis and Total herbicides were evaluated. Chlorophyll a fluorescence of dandelion was measured 1, 2, 3, 5, 7, 10 and 14 days after treatment with different herbicides with a portable fluorometer. For this purpose, fully developed leaves on the top of the plant were selected. The selected leaves were placed in the dark for 20 minutes using special clips so that all reaction centers of the photosynthetic apparatus were open and ready to transfer electrons. Then, a light pulse at a wavelength of 650 nm with an intensity of 3000 μmolphotons per square meter per second was irradiated to these leaves for four seconds, and parameters such as minimum fluorescence (F0), maximum fluorescence (Fm), variable fluorescence (Fv), maximum photochemical efficiency of photosystem II (Fv/Fm), efficiency of the water-decomposing complex as an electron donor of photosystem II (Fv/Fo), and heat loss (Fo/Fm) ) were studied. One month after application of different weed control treatments, in each plot dandelion were colected using a 25×25 cm square and then placed in an oven at a temperature of 72°C for 48 hours and their dry weight was measured.
Results and discussion
Results showed that application of herbicides decreased maximum fluorescence of Fm, variable fluorescence of Fv, maximum photochemical efficiency of photosystem II (Fv/Fm) and efficiency of water splitting complex as an electron donor to photosystem II (Fv/Fo) of dandelion and increased minimum fluorescence and Fo/Fm. Also, dry weight of dandelion weed decreased under the influence of different herbicide treatments compared to control (no herbicide). Results showed that maximum fluorescence reduction in Dylan and Atlantis was more severe and irreversible than Total. Application of a dose of 2 times recommended amount of Atlantis reduced variable fluorescence of dandelion by 46% compared to control. Also, dry weight of dandelion weed decreased under the influence of different herbicide treatments compared to control. The amount of reduction in Dylan and Atlantis herbicide treatment was more than total. In these herbicides, the dry weight of dandelion was 50% less than the control. The results of the effect of herbicides on dry weight were consistent with their effect on the fluorescence parameters of chlorophyll a. Total herbicide did not have much effect on chlorophyll a and dry weight parameters, on the contrary, Atlantis and Dylan herbicides increased Fo and Fo/Fm and decreased Fm, Fv and Fv/Fo, and as a result decreased dry weight of dandelion.
Conchusion
Overall, results showed that Atlantis herbicide had the greatest effect on fluorescence parameters of chlorophyll a and dry weight. Based on results obtained from the evaluation of chlorophyll a fluorescence parameters and the existence of a relationship between chlorophyll a fluorescence parameters and dandelion weed biomass calculated one month after the application of herbicide treatments, it can be concluded that chlorophyll a fluorescence is a quick method to study the effectiveness of herbicides and reduces the time required to study the plants response to herbicides.