Factors affecting leakage from cucumber cotyledons during chilling stress

Detached cotyledons of cucumber seedlings (Cucumis sativus L. Bet Alfa) were exposed to non-chilling (25°C) or chilling (2°C) temperatures for 24 h under various moisture conditions. Relative leakage of cellular substances from the cotyledons increased progressively with the increase in loss of cell water. However, at any given level of cell water, the relative leakage from chilled cotyledons was higher than that of cotyledons which were not chilled. This indicates that chilling damage, as reflected by increased relative leakage, resulted from cellular dehydration as well as from the effect of low temperature on the cell membranes. Application of abscisic acid to the cotyledons 15 h prior to chilling markedly reduced the chilling-induced increase in relative leakage. There are indications that abscisic acid affected this decrease both by maintaining cotyledon water and by diminishing the direct damaging effect of the low temperature.