Reversibility of Chilling Injury to Corn Seedlings

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RESUMO

Seedlings of corn (Zea mays) were tested for recovery from chilling injury incurred at 0.3 ± 0.3 C. At 0.3 C visual leaf injury appeared in 36 hours, whereas stem and root injuries appeared later. Appearance of leaf injury was preceded by a rise in O2 uptake and a lessened effect of 2,4-dinitrophenol on O2 uptake by leaf segments and was accompanied by increased ion leakage from the leaves. These effects were reversible, in that transfer of seedlings to 21 C after 36 hours at 0.3 C produced a return of O2 uptake, 2,4-dinitrophenol stimulation, and ion leakage to the levels of unchilled leaves, as well as a disappearance of leaf symptoms, within 72 hours. For most seedlings, transfer to 21 C after 48 to 60 hours at 0.3 C reversed the chilling effects on O2 uptake, 2,4-dinitrophenol stimulation, and injury symptoms but not on ion leakage within 108 hours. However, some seedlings collapsed during 48 to 60 hours of chilling, and these never recovered. Transfer to 21 C after 72 hours at 0.3 C did not produce recovery from any symptom of chilling injury examined, and these seedlings soon died. No growth occurred at 0.3 C, but growth began soon after transfer to 21 C. Seedlings chilled 24 or 36 hours grew at reduced rates during the first 72 hours at 21 C, but within 96 hours at 21 C were growing at the same rate as nonchilled seedlings. These results demonstrate considerable capacity of growing plants to recover from short chilling treatments even though significant physiological changes occurred at low temperatures.

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