The mitigating role of environmental factors in seedling injury and chill-dependent depression of catalase activity in maize leaves

In pot experiments performed on maize seedlings chilled at 5 A degrees C, leaf injury was diminished by the application of elevated temperature (1 or 5 h at 15 or 20A degrees C, warm breaks treatment) in a dose-dependent manner. The lower the injury count, the higher the catalase (CAT) activity. In a separate experiment, the application of 100 % relative humidity also protected the plants from chilling injury and water loss, increased their gas exchange and variable to maximum chlorophyll fluorescence ratio (F-v/F-m), but did not influence CAT activity. Another protective environmental factor, elevated atmospheric CO2 concentration [700 A mu mol(CO2) mol(-1)(air)] diminished CAT activity inhibition, but only in plants of chilling-resistant cultivar. The positive impact of specific environmental factors accompanying chilling is not obviously related to the suppression of the inhibition of CAT activity, although the enzyme is considered as chilling-sensitive.