Experiment on Cold Resistance of Several Willow Hybrid Strains in Songnen Plain
In order to explore the cold resistance of several willow hybrid strains,six shrub willow new strains(4#,8 #,15 #,16 #,18 #,25 #)with good growth traits in the experimental forest in recent years were tested by cryogenic freezing test and post-freezing growth recovery test to examine the cold resistance of hybrid varieties.With different time as the main treatment,four time gradients were set up at 5 d intervals,and with different strains(varieties)as sub-treatments,the cold resistance test of willow hybrid strain was carried out with Salix integra as the control.The results showed that the order of cold resistance was 18 #>4 #>Salix integra>16 #>25#>8 #>15 #.18 # had outstanding performance and strong cold resistance.When affected by low tempera-ture for a long time,the electrolyte seepage rate of 25 #,8 # and 15 # was higher than 50%,and different degrees of freezing damage appeared.During the period of 15-20 d,the electrolyte permeability of all the tested strains(varieties)in the experiment was above 50%,which would affect the growth and development of willow trees,but it had not yet reached the death time.