AbstractDeuterium, a stable isotope of tritium, was released into a vinyl house in autumn 1995 and summer 1996 to study the transfer of tritium from air to plant and soil. Temporal variation of D2O concentrations in plant and soil water, and plant physiological parameters such as transpiration rate and leaf temperature, were measured during these experiments. D2O concentrations of plants were fitted to a first order kinetic model: Cp = Cmax (1 – e–kt), where Cp is the D2O concentrations in plants at time t, Cmax is the steady-state concentration in plants and k is the rate constant. The rate constant was also calculated using measured plant physiological parameters for comparison. The D2O uptake by paddy rice was most rapid and the value of k was 3.63 ± 0.31 h–1 followed by radish, cherry tomato, Komatsuna and orange. The day/night concentration ratio for cherry tomato and orange was higher than that for radish and Komatsuna.