ROLE OF LIGHT IN THE DEVELOPMENT OF POST-CHILLING SYMPTOMS IN MAIZE

The effect of light (250 mu mol m(-2) s(-1)) on the appearance of post -chilling symptoms was investigated in cold-treated maize (Zea mays L. hybrid Furio) seedlings using electrolyte leakage and chlorophyll flu orescence induction measurements as indicators. The longer the cold pr etreatment (0.5 degrees C) in complete darkness, the more rapid the de crease in F-v/F-m and the increase in electrolyte leakage during cold treatment in the light. The most important difference in the changes i n these two parameters is that the changes in F-v/F-m occur much earli er if the cold treatment is carried out in the light. These findings s uggest that chilling stress in cold sensitive maize plants led to an i ncreased susceptibility to photoinhibition at low temperatures. F-v/F- m and electrolyte leakage changed not only at low temperatures but als o after a certain cold pretreatment period at normal temperature. When the seedlings were returned to 25 degrees C after various chilling pe riods in the dark both parameters showed that post-chilling symptoms a ppeared much more rapidly in the light than in the dark. By contrast t o the change in F-v/F-m, where plants chilled for only two days exhibi ted differences in post-chilling changes in the light and dark, a subs tantial increase in electrolyte leakage was only observed after four d ays of cold pretreatment. These results suggest that photoinhibition h as a role not only during the chilling period, but also in the appeara nce of post-chilling symptoms.