|The effect of sulfite on barley seedlings was investigated through Chl content, the electron transport activity of the photosystem, and Chl fluorescence. Barley leaves were harvested every 12 hrs during greening periods, and were then treated with a sulfite solution in either light or dark conditions. In both cases, the Chl content decreased in comparison with the control at any greening period. After sulfite treatment in the light, the activity of PS Ⅰ decreased slightly. yet that of PS Ⅱ showed a decrease of about 15%. The values of Fv, qP and qE decreased. however the value of qI increased compared with the control. In addition, the value of qE decreased in leaves greened more than 12 hrs compared with that of the control. This indicates that the photosynthetic complex involved in energy dependent fluorescence quenching is undeveloped in a 12 hrs greened leaf, accordingly, it was a hardly affected by sulfite. After sulfite treatment in the dark, the activities of PS Ⅱ and PS Ⅰ decreased slightly. there was a small change in the value of Fv, qP decreased, and qE and the ratio of qNP/q increased in comparison with the control. As a result, PS Ⅱ and PS Ⅰ were not inhibited, however, the redox of Q_(A) was inhibited, and the excited energy was lost through the nonphotochemical pathway. The effects of sulfite in light or dark conditions were not remarkably different according to the PS Ⅰ and Ⅱ activity measurement method yet were considerably different with the Chl fluorescence quenching analysis method. In both light and dark conditions, the value of qP significantly decreased with sulfite compared to that of the control. This implies that the redox of Q_(A) was inhibited by sulfite in both light and dark conditions.