Radish plants were grown in field plots and exposed to simulated rain at four levels of acidity: pH 5.6, pH 4.2, pH 3.5 and pH 2.8. Simulated rain solutions, containing background ions and acidified with a mixture of sulphuric and nitric acids, were applied intermittently between ambient rain events for 1-h periods. In order to test for the effect of the extra supply of water, the growth of plants that received only ambient rain was compared with that of those that received ambient rain & applications of simulated rain at pH 5.6. Applications of simulated rain at pH 5.6 did not affect the total accumulation of biomass but they did affect the distribution of dry matter among plant organs by increasing mass in the shoot and decreasing mass in the root.