Modeling germination and shoot-radicle elongation ofAmbrosia artemisiifolia

Abstract

Laboratory studies were conducted to describe germination and seedling elongation ofAmbrosia artemisiifoliaL. (common ragweed) seed. The germination process was tested for the interaction of temperature and water potential across eight thermo-periods (7.5, 12.5, 17.5, 22.5, 27.5, 32.5, 37.5, and 42.5 C) and 12 water potentials (0, −0.03, −0.06, −0.1, −0.2, −0.4, −0.6, −0.9, −1.2, −1.5, −1.8, and −2.1 mPa). The rate of seedling shoot and radicle elongation was described as a function of temperature and tested for eight day: night temperature treatments (10: 5, 15 : 10, 20 : 15, 25 : 20, 30 : 25, 35 : 30, 40 : 35, and 45 : 40 C). The rate of germination was mathematically modeled by a Weibull function. Probit analysis was used to determine the cardinal temperatures (base, optimum, and maximum) and base water potential (αb). The base temperature (Tb), optimum temperature (Topt), maximum temperature (Tmax), and αbforA. artemisiifoliagermination were estimated as 3.6, 30.9, and 40 C and −0.8 mPa, respectively. The rates of shoot and radicle elongation were described by regression models. TheTb,Topt, andTmaxfor shoot and radicle elongation were estimated as 7.7 and 5.1, 29.5 and 31.4, and 43.0 and 44.3 C, respectively. A mathematical model describing the process ofA. artemisiifoliaseed germination in terms of hydrothermal time (θHT) was derived. The θHTmodel described the phenology ofA. artemisiifoliaseed germination using a single curve generated from the relationship of temperature and water potential. This model can help in predicting germination and emergence ofA. artemisiifoliaunder field conditions.