This experiment was conducted to investigate the effects of constant temperatures and light on seed Germination of white pigweed (Amaranthus albus), smooth pigweed (Amaranthus chlorostachys), redroot pigweed (Amaranthus retroflexus), and green amaranth (Amaranthus viridis) in 2018 and 2019 at Gorgan University of Agricultural Sciences and Natural Resources. In the first year, Germination of different species of Amaranthus were studied monthly over a 12-month after-ripening period. In the fifth month of after-ripening, seed Germination of different Amaranthus species was studied at temperatures of 10, 15, 20, 25, 30, 35, 40, and 45 °C under light and darkness conditions. In the second year, seed Germination of the mentioned species was investigated at temperatures of 10, 15, 20, 25, 30 and 35 °C in four conditions: light with gibberellic acid, light without gibberellic acid, darkness with gibberellic acid and darkness without gibberellic acid. The Germination percentage of different species of Amaranthus increased during the after-ripening period,although the process were varied in different species. The application of gibberellic acid also improved Germination. Therefore, seed dormancy of the mentioned species is non deep physiologically. Germination percentage of different species of Amaranthus increased in temperatures of 30-35 °C, and gibberellic acid also improved their Germination percentage and rate. Also, the use of gibberellic acid reduced base temperature of Germination. Such responses to light and temperature ensure the Germination of these plants in spring and on the soil surface. A decrease in the base temperature of Germination may also cause the Germination of some species of Amaranthus before spring. Low Germination percentages, especially at low temperatures, are biologically important because small but significant populations of weeds may appear in the field and cause problems for farmers.

Evaluating of an appropriate model is critical for quantifying the response of Germination rate to temperature and determination of cardinal temperatures. This study was conducted to evaluate different nonlinear regression models to describe response of Germination rate to temperature in Salvia species. The regression models were dent-like, segmented and beta. Root mean squareof error, coefficient of determination, correlation coefficient and regression of predicted values versus observed ones were used to find the appropriate model(s). Dent-like and segment models were superior compared to the Beta model in Salvia species. It was concluded that these models can be used to quantify response of Salvia species Germination to temperature and to obtain cardinal temperature of Germination. These parameters are required to predict Salvia species Germination and emergence.

It is very important to find the best model to quantify seed Germination rate on the response of temperature which it can be used in determination of cardinal temperatures. This study was conducted to evaluation nonlinear regressions models for description wheat (cv. Morvarid) Germination rate response to temperatures and water potentials. Therefore, seeds Germination rate were evaluated in temperatures of 5, 10, 15, 20, 25, 30 and 37oC and water potentials of 0, -0.2, -0.4, -0.6 and -0.8 MPa. Four functions (Dent-like, Segmented, Beta (original) and Beta (Modified)) were evaluated to describe Germination rate on the response to temperature and water potentials. The results indicated that the best model was Dent-like which can better estimate Germination rate in response to temperature and water potential. The base, the lower and the upper and the ceiling temperatures were 1.5, 23.8, 33.0 and 41.0oC in the optimum conditions of water potential. Cardinal temperatures had no significantly change under different water potentials, except for base temperature. Biological time for Germination ranged from 34 to 51 h in different water potentials. Biological time increased about 20 h by decreasing 1 MPa. Estimated parameters and the relations can be used to prediction time to Germination or emergence in wheat under wide environmental conditions from normal to drought stress.

Prediction of Germination time is one of the main goals of seed researchers. Therefore in order to evaluation the cardinal temperatures and the investigation response of promising forage sorghum lines to temperature, this experiment was conducted as factorial in a completely randomized design with three replications, 15 forage sorghum lines and nine fixed temperatures 10, 15, 20, 25, 30, 35, 40, 45 and 50˚C at Seed Technology Laboratory of Islamic Azad University Shoushtar Branch in 2013.Results of analysis of variance showed that investigated Germination components for factor line, temperature and interaction line × temperature were significant. The maximum Germination percent-age in temperatures 20, 25 and 30oC and the most speed rate, uniformity of Germination and the minimum duration time till 95 percent the maximum Germination (D95) in temperature 40oC was obtained. With temperature drop from 40oC, Germination speed rate and D95 gradually decreased and increased, respectively.The base temperature (Tb) of forage sorghum lines from 9.36oC (KFS11) to 14.28oC (KFS2), optimum temperature (To) from 23oC (KFS2) to 37.2˚C (KFS11) and maximum temperature (Tc) from 40.7oC (KFS2) to 49.76oC (KFS15) varied. Cluster analysis with ward’s method in the basis 7 studied traits led to three clusters formation. Third cluster included the lines KSF6, KSF7, KSF9 and KSF10 with the maximum percentage, rate and uniformity of Germination and the minimum D95 jointly in temperatures 25oC, 30oC, 35oC and partially 40oC therefore these lines are recommended for supplementary researches.

Cold and tropical Vetch (Vicia villosa and Vicia pannonica) are an important plants which did not do any experiment about quantification of them Germination reaction to temperature. Thus, a CRD experiment performed in seed research laboratory of Urmia University with four replications which temperature treatment were eight levels of temperature as: 1, 3, 5, 10, 15, 20, 25, 30, 35 and 40oC. Results revealed that temperature had a significant effects on Germination rate and it’s percent and segmented model estimated greatly cardinal temperature (base, optimum and ceiling temperatures). Germination rate of Vicia. Pannonica in equal and less than -7.6 and equal and higher than 40.76oC stopped, though this thermal range for V. villosa was equal and less than -3.8 and equal and higher than 41.2oC, respectively. R max were 0.027 and 0.033 h-1 for V. pannonica and V. villosa respectively. Also, results emphasized that both of Vicia species can be geminate in less than zero temperature and in V. Pannonica the base temperature was fewer than V. villosa, so, Germination percent and its rate increased by upgrading in temperature to optimum temperature. Therefore, both Vicia species can geminate and emergence in extended range of environmental thermal from -7.6 to 40.76oC for V. Pannonica and -3.8 to 41.2oC in V. villosa and thus recognized as a forage crop with acceptable production for various season and climate.

Nowadays the improvement of agriculture and range lands to decrement soil erosion, productivity and forage production, to make by plants modifier species. One of the plants is annual medic that it has positive regression between up growths and propagations with climatic and edaphic factors. Annual medics by their potential benefits such as soil conservation, soil fertility improvement, weeds control and forage production can play a significant role in land improvement. Thus to reach successful improvement plan in an area, we must recognize stage of up growth in different temperatures. Six species were tested in four different temperatures during 21 days period and investigated due to number of hard seeds, number of abnormal seeds, cotyledon growth, and root growth parameters. The results indicated that there is significant between species in different temperature due to situation of generation. There is also alike reaction between species in different temperature. The increment of temperature caused decrement time of root growth in all of the species. Also the increment of temperature caused up percent of generation in species. The results show that there is no significant between temperature and percent of hard seed in species. Annual medics are part of the Iranian flora which 14 domestic species of them have been identified in native distribution regions by annual mean temperature between 5 to up20oc. In 5oc root growth make but in some of them cotyledon isn’t growth and this caused degeneration. Therefore the best situation for annual medic cultivation is areas with temperature up 5oc.

Germination response to temperature is different among plant seeds. Germination rate and percentage is maximal at optimum temperature (s), and then reach to zero at base and ceiling temperatures. The objective of this research was (1) to evaluate Germination response of snail medic seeds to temperature and (2) to determine cardinal temperatures of Germination rate and percentage. Therefore, seeds germinated at 10 to 400C by 50C interval. Results indicated that response of Germination percentage and rate adequately described with dent-like and segmented functions, continually. Base and ceiling temperatures were obtained 0.46 and about 40°C for both Germination rate and percentage. Optimum temperatures were 15-27.730C for Germination percentage and 22.220C for Germination rate.

In this study, Germination characters and growth of T.alexanderinum (berseem clover) at two levels of temperature regimes (250Cand 350C ) and five levels of salinity (distilled water, 3, 6, 9 and 12 ds/m) were studied using a completely randomized design with four replications. The results of the analysis of variance showed that the effects of different levels of salinity and temperature on Germination percentage, rate of Germination and length of hypocotyle were highly significant (p<0.01) but the effect of temperature on root length was not significant. Comparing Germination percentage means showed that rate of Germination decreased with increase in salinity. In comparing of control treatment the Germination percentage at 250Cand 12ds/m Nacl down to 57%. Maximum Germination rate was recorded at 350C temperature and control treatment and the minimum of this character was recorded at 350C and 12ds/m salinity. In both levels of treatment (25and 350C) with increase in salinity levels, differences between shoot and root lengths reached to minimum level.

Seed dormancy in Apiaceae family is one of the major obstacles for cultivation and domestication of these species. In this research, two separate experiments were conducted to determine the best treatment for breaking seed dormancy and improving Germination in Smyrnium cordifolium Bioss. In the first experiment, effects of three factors including 7 levels of gibberellic acid (0, 500, 1000 and 1500 mg L-1) with pre-treatment with gibberellic acid for 48 and 72 hours and 3 levels of stratification (4, 8 and 12 weeks) and different Germination temperatures (5, 10 and 15° C) were investigated in a factorial experiment based on a completely randomized design with four replications. In the second experiment, the effect of different levels of gibberellic acid (used in the first experiment) in different levels of stratification (0, 2, 4, 6, 8, 10 and 12 weeks) on the α-amylase activity and hydrogen peroxide content were studied. The results showed that in all three temperatures, 12 weeks stratification had the highest effect on most measured traits. Also, in most of the stratification periods, the amount of alpha-amylase activity and hydrogen peroxide content increased in pre-treatment with gibberellic acid. Among all the treatments, the combination of 12 weeks stratification along with 500 ppm gibberellic acid and Germination temperature of 5 ° C had the highest effect on breaking seeds dormancy of Smyrnium cordifolium Bioss.