Abstract
Eight species of crop were exposed to simulated acid rain (SO42-: NO3-: Cl-=2:1:2, equivalent ratio) at pH 5.6 (control), 3.0, 2.7 and 2.5 throughout their entire growing periods. Plant were subjected to acid rain treatment three times a week, for one hour with 7-13mm of precipitation at a time. Simulated acid rain at pH 3.0 or below produced foliar visible injury on leaves of all the tested plants in this study. Injury degree of the foliar visible symptoms was varied among plant species. In addition, injury degrees were different among leaf positions: injury was severer in lower lesf position, particularly cotyledons and primary leaves, than upper one. In many cases in this study, foliar visible injury was severer at the early stages of growth than the later stages. Dry weight of rice plants exposed to simulated acid rain at pH below 3.0 was reduced compared with pH 5.6 at early stage of growth. At the middle to late growth stage, however, acid rain treatment did not affect the growth of rice plants. The relationship between pH of simulated acid rain and yield loss in each crop suggested that acid rain at pH 3.0 or less acidity would not cause yield reduction at any crop. In the lower pH range less than 3.0, yield loss acidity in simulated acid rain varied among plant species. The yield of rice was not reduced even at pH 2.5.
