To obtain a better understanding on how non-human biota are affected by exposure to environmental radioactivity, it is essential to link observed effects to a correct estimate of absorbed ionising radiation dose. Current wildlife dose rate and risk assessment tools are not setup to assess changes in dose rate during organism development. This paper presents a dosimetry model for assessing dose rate and absorbed dose during seedling development of the model plant Arabidopsisthaliana. We included growth and radionuclide absorption dynamics into the dose calculations. This model was subsequently used to compare the dose and dose rate calculations for three radionuclides, 241Am (α-radiation), 90Sr (β-radiation) and 133Ba (γ-radiation), in a standard exposure scenario. We show that growth influences dose and dose rate and thatt his influence depends on theradionuclide and the organ involved. The use of dynamic dosimetry models greatly improves the dose calculations for effect studies.