نشریه دانش علفهای هرز
سال نوزدهم شماره 1 (بهار و تابستان 1402)

This research was carried out to estimate the cardinal temperatures of Ambrosia psilostachya seed germination and evaluation of some nonlinear regression models. The experiment was performed at Tehran University Weed laboratory in 2022. In this experiment, the seeds were exposed to 8 temperature treatments (5, 10, 15, 20, 25, 30, 35, and 40ºC) with 3 replications in a completely randomized design. The germination rate, seed germination percentage and mean germination time of seeds were measured. Cardinal temperatures of seed germination were estimated using four regression models including segmented, dent-like and beta (four and five parameters) models. The performance of models and statistical indices was compared by RMSE (root mean squared of error), R2 (coefficient of determination) and AICc (corrected Akaike Information Criterion). Highest germination percentage was obtained at 15, 20 and 25°C (60.3%, 63.7% and 63%, respectively). The Highest germination rate (0.13d-1) and the lowest mean germination time (7.48d) were obtained at 25°C. Due to lower AICc and RMSE, the beta model (five parameters) was the best model for predicting the response of germination percentage to temperature in A psilostachya. Generally, base, optimal and ceiling temperatures were estimated 5, 25.5 and 42.13°C respectively by beta five-parameter model.

White Morning Glory (Ipomoea lacunose L.) is one of the weeds that have recently spread in the fields of Golestan province. In this study, the effect of different environmental conditions, including constant temperature, alternating temperature, water potential, salinity, high temperature, waterlogging, and burial depth on the germination and emergence of three seed populations of this plant collected in 2017, 2018 and 2019 were investigated. The results showed that the response of germination to the studied environmental factors was different in seed populations. Germination percentage started at 10°C and increased with increasing temperature. Although the germination percentage was significant at 40°C, it was completely stopped at 45°C. The water potential required to reduce 50% of germination in the seeds of 2017, 2018, and 2019 was -0.83, -0.82 and -0.43 MPa, respectively. The tolerance of this species to salt stress was much higher than to water stress, and the increase of salinity up to the potential of -1.1 to -1.4 MPa reduced its maximum germination by 50%. Increasing the high temperature to 80 and 100 °C stimulated the germination, and no seeds survived at 120°C. By increasing the burial depth by 3 cm, the emergence increased and then decreased. Knowing the germination response of this species against the mentioned factors can help predict the germination and emergence of this plant to design suitable management strategies

Japanese brome (Bromus japonicus Thumb.) is known as the most important grass weed in the wheat fields of Sistan & Baloochestan. Using an additive series design we conducted field experiment over 2008-09 and 2009-10 growing seasons at Zahak, Zabol to characterize interference between wheat and Japanese brome. Wheat densities were considered at five levels of zero, 350, 400, 450, and 500 plants per m2 and Japanese brome at four levels of zero, 100, 200, and 300 plants per m2. Here, we estimated the intraspecies and interspecies competition coefficients, relative competitive ability and niche differentiation. For both years of experiment and in both stages of tillering and physiological maturation of wheat, the intraspecies competition coefficient of wheat ( ) was negative and the interspecies competition coefficient ( ) between wheat and Japanese brome was positive. The relative competitive ability of wheat ( ) showed that each Japanese brome plant was able to have a negative effect on the dry weight of a wheat plant equal to 2.5 wheat plants. The coefficient  showed that the competitive potential of each wheat plant in the tillering stage was 9.5 and 3.3 times more than a Japanese bromus plant in the first and second years of the experiment, respectively. In the interference of wheat and Japanese brome, wheat had a higher competitiveness, especially at the tillering stage. No niche differentiation observed between wheat and Japanese brome and their ecological niche strongly overlapped, which it was more at the tillering stage.

Disruption in the photosynthetic system is one of the reasons of reducing in plant growth and chlorophyll fluorescence a measurement is one of the methods of these disorders investigation, which shows the photochemical qualification of the plant. In order to study the effect of the combination of salicylic acid (SA) with mesosulfuron methyl + iodosulfuron methyl herbicides on the physiological behavior of wild oat, a factorial experiment was conducted in a completely randomized design with four replications, in the greenhouse of the Faculty of Agiculture and Natural Resources of Mohaghegh Ardabili University in 2020. The results showed a decrease in maximum fluorescence (Fm) and maximum quantum yield of primary photochemistry (Fv/Fm) and an increase in minimum fluorescence (Fo). The fresh and dry weights of wild oat decreased in all treatments except the control treatment (no herbicide) and the chlorophyll index slowly reduced one days after herbicide application compared to the control treatment. According to the results, all concentrations of herbicide reduced the dry weight of wild oat by more than 40%, and salicylic acid application did not affect the effectiveness of herbicide in the mentioned weed control.

In order to manage narrow-leaved weeds in wheat fields, an experiment was to investigate the effect of five adjuvants on the efficiency of different doses of Pinoxaden herbicide (EC 5%) in controlled of avena ludoviciana and Lolium rigidum accessions. experiment as a factorial experiment in a completely randomized design with four replications in greenhouse of Plant Protection Institute in 2020. Factors consists of five adjuvants (Ino Alg NPK, Ino Alg NPK (NG), Torpedo and amino acid leucine), 2-included different doses of pinoxaden (including doses of 37. 2, 46.2, 56.7 and 72 g.a.h-1 (Pinoxaden) 3- included of Avena ludoviciana and Lolium rigidum accessions (susceptible and resistant). Weed results showed that adjuvants used in this experiment with Pinoxaden did not show a negative effect on wet and dry weight loss of wheat. Also, with increasing dose of Pinoxaden , control of weed populations increased. Among Adjuvants the use of Ino AlgNPK (NG) adjuvants with fresh weight loss of 93.69 and 87.39% ( populations of Avena ludoviciana, respectively) and amino acid leucine with fresh weight loss of 96.48 and 80.78% (Lolium rigidum, respectively) with a dose of 72 g.a.h-1 had highest reduction in fresh weight loss compared to control. in terms of EWRC index and dry weight loss percentage, no significant difference was observed between doses and adjuvants used in control of these two weeds. results showed amino acid adjuvants leucine and Ino AlgNPK (NG) is recommended to increase effectiveness of Pinoxaden in controlling the weeds of Lolium rigidum and Avena ludoviciana, respectively.

Knotgrass)  Paspalum distichum L.) is a rhizomatous perennial narrow-leaf weed belonging to the Poaceae family. Widespread use of herbicides to manage paddy fields’ weeds and their ineffectiveness in knotgrass control, this weed is now considered the main constraint to producing rice in tens of thousands of hectares of paddy fields. Two open-air pot studies were conducted to evaluate the knotgrass response to paddy field selective herbicides. The results of the first experiment showed that 8 out of 16 rice selective pre-emergence herbicides were less than 44% effective in reducing the biomass of knotgrass. Molinate, 58%, pretilachlor + pyrazosulforoun-ethyl, 62%, oxadiargyl, 64%, penoxsulam, 73%, clomazone + pendimethalin, 87%, metazosulfuron, 92%, and triafamone+ethoxysulfuron, 96% reduced the biomass of knotgrass and halosulfuron increased the biomass of this weed by 20%. The results of the second experiment indicated that 9 out of 13 foliar applied herbicides, reduced the shoot biomass of knotgrass by less than 50%. Pre-packaged herbicides propanil + pretilachlor, 52%, triafamone + ethoxysulfuron, 71%, cyhalofop + penoxsulam, 71%, and glyphosate caused 93% reduction in its shoot biomass. According to the results of this study, all common herbicides of recent decades lacked efficiency to control knotgrass in paddy fields of Iran, but the new herbicides are more effective in this regard. Further field studies are necessary to provide practical recommendations for the chemical management of knotgrass.