Abstract: The ultrastructure of petal，pollen，stigma and ovule cells under chilling stress after SA
pretreatment was observed using the transmission electron microscopy. The results showed that the
ultrastructure of normal flower cells pretreated with H2O was damaged remarkably under –2 ℃ for 4 h.
The plasmolysis phenomenon occurred in the spetal cells，the cristae of mitochondria were damaged；
Obvious injury occurred in pollen exine；The cristae of mitochondria of stigma and nucellus cells were
disrupted and even became empty，the nucleus membrane was partly dissolved. In contrast，the
ultrastructure of petal，pollen，stigma and ovule cells pretreated with 100 μmol · L-1 SA still maintained
nearly integrated state after 4 h chilling stress. Therefore，the stability of flower organ cells under chilling
stress could be increased by SA pretreatment. The obtained results，to our knowledge，firstly offered the
cytological evidence for the chilling resistance increased by exogenous SA pretreatment in apricot flower.

Key words: apricot, flower organ, salicylic acid, ultrastructure, low temperature