intersected-lines model

Carrot is a particularly difficult crop to manage in terms of weed control. For weed management of carrot, seed germination is a key process because it determines both the number of weeds that could potentially emerge and the timing of their appearance in the carrot. This study was done to evaluate two nonlinear regression models (Intersected-lines and Dent-like) to describe response of germination rate to temperature in carrot (Daucus carota L.), common chickweed (Stellaria media (L.) Vill.), yellow foxtail (Setaria glauca (L.) P. Beauv.) and canada fleabane (Conyza canadensis (L.) Cronq.). This experiment was based on completely randomized design with 4 replications at Islamic Azad University, Science Research Branch, in 2015. The seeds were treated with different temperatures (2, 5, 10, 15, 20, 25, 30, 35, 40 and 45oC). The analysis of variance showed that temperature had a significant effect on all seed germination percentage and germination rates. Intersected-lines model was superior in carrot and Dent-like model was superior for common chickweed, yellow foxtail and canada fleabane. Base, optimum and maximum temperatures were predicted with appropriate model. Base, optimum and maximum temperatures were for carrot 1.67, 22.84, 43.16; common chickweed 3.58, 18.82-19.67, 42.75; yellow foxtail 14.17, 33.75-34.92, 44.86 and canada fleabane 13.74, 31.73-31.94, 44.21ºC, respectively. This results showed that carrot germinated earliest among the studied species, because it had the lowest base temperature, so sooner planting it was caused sooner carrot establishment and less weed competition.

Harvesting of medicinal plants from their natural habitats, put them in danger, hence their domestication is needed. In this context, knowledge of the properties of these plants, including the cardinal germination temperatures are necessary. In order to determine the cardinal temperatures and the effect of temperature on the percentage and rate of germination in Plantago major ecotypes (Birjand, Ghaen, Torbathydarieh, Mashhad, Kalat and Bojnord) an experiment was conducted based on factorial in a completely randomized design with 9 temperature levels (5, 10, 15, 20, 25, 30, 35, 40 and 45 °C) and four replications in Crop Physiology Laboratory, Ferdowsi University of Mashhad in 2013. To determine the cardinal temperatures Intersected-Lines Model and Five-Parameters Beta Model were used. Results showed that maximum germination percentage was obtained at 30 °C while maximum germination speed achieved at 35 °C in Bojnourd and Birjand ecotypes, respectively. The highest germination percentage was observed in Birjand ecotype at the temperature range of 20 to 35 °C. Based on models fitted depending on the ecotype, cardinal temperatures  (minimum, optimum and maximum) germination were determined (6.3 to 9.8, 1.8 to 5°C) ,(31.1 to 35.9, 28.6 to 35.2°C) and (43.3 to 45.1, 45 to 45.6 °C) of Intersected-lines and Five-Parameters Beta Model, respectively. Diversity in cardinal temperature of plantago major ecotypes could be due to different environmental conditions where they were evolved and adapted