بهناز پورمراد کلیبر

Recognition of Eryngium caeruleum germination biology can provide the possibility of forecasting the seed dormancy and germination level in various conditions. This study was conducted as factorial experiment based on completely randomized design with three replications in the laboratory of Agronomy and Plant Breeding Department, College of Agriculture and Natural Resources, University of Tehran, to understand Eryngium caeruleum seed dormancy and response of germination thermal parameters. The experimental factors were included three levels of gibberellic acid (0, 250, 500 mg/l), six chilling time (1, 3, 5, 10, 15, 30 days) and seven temperatures (5, 10, 15, 20, 25, 30, 35°c). Germination parameters were obtained by the segmented model under the influence of gibberellic acid and chilling treatments. The results of this study showed that, the best treatment for reducing dormancy level, cardinal temperatures for germination including base, optimum and ceiling temperatures was obtained 1.81, 22.31, and 34.10°c respectively. Increasing of the chilling time and the gibberellic acid concentration from 0 to 250 mg/l, decreased the base temperature, and increased optimum temperature. Ceiling temperature, at first was increased and then decreased.

A split-plot experiment was conducted during 2016 with 3 replications to determine the optimum time and dose of tank mixture of Nicosulfuron and Bromoxynil+MCPA for weed control in maize (Zea mays) in Karaj. Main plots were four application times (different maize growth stages: 2-3, 3-4, 4-6, and 6-8 leaves) and subplots were five doses of herbicide mixture (0, 25, 50, 75, and 100 % of the recommended dose). Doses of herbicides and weed biomass relations were described with the standard dose-response model at each application time. Parameter estimates suggested that delaying in herbicides application increased ED 50 parameter (herbicide dose required for 50 percent reduction in weed biomass) from 6 to 54. In general, parameter estimates showed that Chenopodium album was more sensitive to herbicide mixture compared to Solanum nigrum and Amaranthus blitoides. Relationship between the doses of herbicide mixture and maize yield and total dry matter were described with a linear model. Delaying in herbicides application decreased the effect of each percent of the recommended dose of herbicide mixture on increasing maize yield and total dry matter (parameter b 1 ). For example, in the case of maize forage yield, it was 0.45 at first application time and reached 0.15 at the last application time. In general delaying herbicide mixture application time to 6-8 leaf stage of maize reduced herbicide efficacy for weed control and there was a need for higher doses to achieve an acceptable yield.

Eryngium caeruleum L. is a perennial weed from Apiaceae family that grows in the farm and roadside. There is limited information on the reaction of this plant germination to temperature and light conditions. Germination is one of the most important processes for weed success, because it is the first step in competition beginning in an ecological niche. Recognition of E. caeruleum germination and emergence ecology has an important role in weed management and control. Different environmental factors, such as temperature and light, affect dormancy and germination of the seeds. Light requirement is an indicator showing the level of seed dormancy. Given the significance of seed dormancy in weed dispersal and management, this study aimed at determining the relation between light and temperature as the most effective environmental factors in germination stimulation of E. caeruleum. An experiment was conducted to estimate the effect of temperature and light on germination of Eryngium caeruleum seeds at agriculture and Natural Resources College, university of Tehran in 2016. A factorial experiment was undertaken based on completely randomized block design with three replications. Factors were germination temperatures (5, 10, 15, 20, 25, 30 and 35 °C), burial periods in 5 cm depth (30, 60, 90, 120, 150, and 180 days), and light conditions during germination test (Presence and absence of light). The seeds were buried in the soil under environmental conditions at depth of 5 cm and then removed from the soil at one month intervals and were placed at dark and light (Osram, L 18 W/77, 20 µmolm-2s-1) conditions under seven temperature treatments for 14 days. 25 seeds were placed in each petri dish and the germinated seeds were counted for 14 days in each month. Segmented model was used for studying the germination rate to temperature in light and temperature treatments. Thermal parameters of germination were calculated for light and temperature treatments. These parameters were Gmax for the maximum germination rate, Tb or base temperature for germination, To or optimum temperature for germination, and Tc or ceiling temperature for germination. The base and ceiling temperature parameters were also calculated. The findings of this study shed light on seed germination requirements of E. caeruleum and enhance our understanding of this species distribution. These results will be useful in selecting the best time and method for E. caeruleum control. Results showed that temperature and light conditions during germination test influenced germination rate. According to the analysis of variation, all simple effects and interactions were significant on germination rate. Germination rate increased with increasing temperature up to 20 °C. Germination rate, however, decreased when temperature increased up to 35 °C. Temperature parameters of base temperature, optimum temperature and ceiling temperature were affected by burial periods and light conditions during germination test. In general, base and optimum temperatures decreased and ceiling temperature increased with increasing of burial time. The burial time needed for 50 percent decrease of maximum base temperature in the lowest burial time was 117 days in light condition and 82 days in dark condition. The optimum temperature decreased from 23.5°C to 21.2°C in light condition and from 23°C to 21°C in dark condition. The ceiling temperature increased from 28°C to 42°C in light condition, but it had different process in dark condition. The Tc parameter was 30°C in 60 days of burial and was 28°C up to 120 days of burial and had no changes up to 180 days of burial. Parameters of Gmax and ai, which indicate the maximum germination rate and seed non-dormant index, respectively, rose linearly by increasing time of seed burial, irrespective of light condition during germination test. The same results were found in Circium arvense and Bidens pilosa, that their germination thermal parameters were higher in light condition than in dark. This can be attributed to the heat made by the light. The results of the experiment on Plygonum aviculare also showed the effects of light on cardinal temperatures of germination and the start of germination of this plant. The results showed that the thermal parameters of Eryngium caeruleum germination including base temperature (Tb), optimum temperature (To), and ceiling temperature (Tc) changed during the burial periods. The Gmax and awakeness index parameters increased linearly regardless of the presence or absence of light. It can be also concluded that Eryngium caeruleum L. has morphophysiological dormancy and dormancy breaking. Moreover, the optimum temperature range for germination mostly rises by increasing ceiling temperature.

This study was conducted to evaluate the effect of temperature and moisture on germination of Eryngium caeruleum seeds as factorial experiment in a completely randomized design with three replications at weed science laboratory, college of agriculture and natural resources, university of Tehran. Factors were seven temperatures (5, 10, 15, 20, 25, 30 and 35°c) and seven levels of moisture (0, -2, -4, -6, -8, -10 and -12 bar) and hydro thermal time model used for description of Eryngium caeruleum germination. Germination parameters including base temperature (Tb), optimum temperature (To), the minimum moisture needed for start of germination (Wpb), decreasing coefficient (b) and standard deviation (Sigma) were obtained 2.39, 23.52, -0.93, 0.13 and 0.34 respectively, affected by different levels of temperature and moisture by using hydro thermal time model. The results also showed that germination percentage and rate increased up to -4 bar in base temperature and these germination characteristics reached to their highest level in optimum temperature. According to the results of this study, it can be said that the seeds of Eryngium caeruleum do not have resistance to the water stress at very low and very high temperatures, and have the maximum resistance at 20°c

Allelopathic phenomenon is an interference method of weed on crops that can help to know crop-weed interaction. This experiment was conducted to evaluation of Sinapis arvensis and Cirsium arvense allelopathic effects on canola germination and nutrient uptake in 2007 at greenhouse of University of Mohaghegh Ardabili. Treatments were differential concentrates (0, 2.5, 5, 10, 20 and 40%) of fresh and dry residual extract of Sinapis arvensis and Cirsium arvense. The experiment was laid out as factorial in completely randomized design. Analyses shown that fresh and dry extract of two weeds reduced germination of canola in compared with control 1.5 to 2.5 times. Also fresh and dry extract of weeds reduced canola dry aboveground mass. Nitrogen and P uptake reduced under fresh extract, while dry extract of Sinapis arvensis increased p uptake in canola more than 4 times. Fresh and dry extract of Sinapis arvensis and Cirsium arvense increased canola K concentrate. The experiment results show that in addition to competing weeds, through release of chemicals can be also inhibit on growth and physiological processes of crop.

Presence of weeds and crops together in agro-ecosystems requires the much attention intheselection of agricultural practices. This experiment conduced in 2009 to determine nitrogen requirement to take maximum winter wheat yield with weed interference at agricultural research site in agricultural college، university of Mohaghegh ardabili. The experiment was laid out as split-plot in randomized complete block design with three replications. The treatments consisted of three nitrogen levels: [0 (control)، 75 & 150 kgNha-1] and duration of weed interference [interference during all season growth (T75)، interference for 50 days after April (T50) and weed control (T0)]. The experimental design was Split-plot design in randomized complete block with three replications. Results showed that in weed control plots، increasing the amount of nitrogen، grain yield increased from 2900 to 5128 kg ha-1. In weed interference، doubling the amount of nitrogen fertilizer increased yield loss more than 2 times. In plots without weed interference، doubling the amount of nitrogen increased nitrogen use efficiency from 1. 86 to 7. 43. While the interaction of weeds and wheat declined nitrogen use efficiency.

To study the effect of nitrogen application and 2-4-D on weed density and weed architecture in winter wheat an experiment was conducted at agricultural research site, university of Mohaghegh Ardabili, Ardabil in 2009. Treatments were two nitrogen levels (no fertilizer and 150 kgNha-1 application) with or without 2-4-D (1.5 kg ai ha-1). Results showed that nitrogen application had no significant effect on weed density. Nitrogen application has increased weed dry weight to two-fold. Nitrogen application increased weeds dry weight on top layers of wheat canopy. 2-4-D application decreased weed density and weed dry weight. 2.4. D decreased density of annual spring weed over 90%. Wheat yield increased to 44% when herbicide applied compare to no herbicide application. Wheat yield was not significantly affected by N application.

Crop residue is a non-chemical method of weed control in agricultural sustainable systems. This research was conducted at the Alarogh site of Ardabil to evaluate the effect of integrated use of mulch and herbicide on weed emergence and growth in potato in 2007. Treatments were four levels herbicide including: (1) Paraquat [N,N'-dimethyl-4,4'-bipyridinium dichloride] herbicide as pre-planting, (2) metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5-one] herbicide as pre-emergence, (3) Paraquat as pre-planting plus metribuzin as pre-emergence and (4) without herbicide (control) as main plots, and four levels crop mulch including: (1) wheat residue, (2) barley residue, (3) canola residue and (4) without mulch as subplots. Results showed that metribuzin application reduced weed density at the both stages (flowering and pre-harvesting) two times. Crop residue on the soil surface completely suppressed winter and early spring weed emergence and growth, but did not suppress on lately spring weed. In plots that was applied metribuzin herbicide plus crop residue redroot (Amaranthus retroflexus) and lambsquarters (Chenopodium album) density was reduced to lower than 3 plant m-2, and purslane (Purtolace olerace) density declined to lower than 8 plant m-2. These results show that: 1) crop residue can suppress winter weed growth specially to flowering stage of potato, 2) The effect of crop residue on soil surface decline after 4 to 6 weeks and weeds which emerged after need control by either practice.