State Key Laboratory of Crop Biology/College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’an Shandong, 271018, P. R. China.
We assessed changes in ultrastructure, membrane lipid peroxidation and
antioxidant systems for cucumbner seedlings subjected to low temperature stress
(day/night temperature of 8 oC /5 oC) that had been either pre-treated with 10%
PEG for 2 days or not. We found extensive cell structure damage in the non-treated
seedlings, whereas the seedlings pretreated with PEG to simulate drought remained
essentially undamaged, except for slight damage to plasma membrane lipids and
alveolation in the mitochondria. Low temperature stress increased electrolyte
leakage, MDA levels and H2O2; decreased the activities of SOD, CAT and
APX, and AsA and GSH content. An increase in POD activity was observed in the
PEG-pretreated seedlings during the chilling period, while non-treated seedlings
showed an increase in POD activity only in the early days of chilling stress. PEG
pre-treatment diminished the level of lipid peroxidation caused by chilling
compared to the non-treated seedlings, possibly due to a decrease in electrolyte
leakage and MDA content. Furthermore, PEG pre-treatment increased the activities
of SOD, POD, CAT and APX and AsA and GSH content in the chilling-stressed
seedlings. These results suggest that PEG pre-treatment stimulates the adaptation
of cucumber to low temperature. This could be due to stabilisation of the cell
structure, alleviation of lipid peroxidation as a result of the increased activity of
antioxidant enzymes and contents of antioxidant metabolites.
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