Role And Underlying Mechanisms Of Polyamine In Dehydration Tolerance Of Citrus

Polyamines(PAs),a ubiquitous low-molecular-weight aliphatic amines,play key protective role in aboitic stresses.In this research effort were made to identify the function of exogenous polyamines on dehydration tolerance and to investigate the underlying mechanisms,with the intention of providing foundation for applying PA in fruit production.The main results are as follows.1,Cleopatra(Citrus reshni Hort.ex tan) in vitro plantlets were pretreated with 1 mM putrescine,spermidine or spermine(Spm) solution for 5 days,followed dehydration for 12 h at room temperature.Based on the water loss,electrical conductivity,1 mM Spm was chosen for the following experiment.2,Red tangerine(Citrus reticulata Blanco) in vitro plantlets were pretreated with or without 1 mM sperminefor 5 days before they were dehydrated for 12 h.The plantlets pretreated with Spm were less wilted than the control,with the higher fresh weight at the same time point and lower electrical conductivity than that of the controls,indicating that exogenous Spm can enhance the tolerance of dehydration. 3,NBT and DAB staining indicated that O₂-and H₂O₂ contents in dehydrated plantlets increased as time extended.The activities of SOD,POD and CAT of both the treatment and control decreased,increased and fluctuated respectively,but the activities of the antioxidant enzymes were higher in the treatment.4,PAs content in dehydrated red tangerine leaves increased with the dehydrating time,but the content in the pretreated leaves was more than that in the controls;stomatal aperture reduced gradually after 12 h dehydration with less decrease in the pretreated leaves.Above results demonstrated that exogenous Spm may enhance dehydration tolerance in citrus via affecting stomatal movement and improving antioxidant enzymes' activities.