Rooting Approaches And Mechanism Of Populus Bachofenii×P.pyramidalis ROZ Microcuttings

Populus bachofenii×P,pyramidalis ROZ is a new cultivar hybridized by Populus bachofenii and P.pyramidalis,which is selected and cultured by scientists of Siberian arboretum in Russia.This cultivar has the characteristic of high adaptability,rapid growth,long life,beautiful shapes of trees and leaves,excellent timber and also the tolerance of low temperature(the lowest of -50℃),drought,and saline-alkali,which is suitable for city virescence and timber in north China and other high altitude area.We studied the effects of environmental factors on rooting of Populus bachofenii×P,pyramidalis ROZ microcutting in vitro and ex vitro and discussed the regulation mechanism of adventitious roots formation by studying changes of soluble sugar and protein content and related enzyme activity.The results were as follows:(1) The basal medium,auxins and their concentration,concentration of sucrose and agar and pH had no significant effects on rooting percentage of the microcutting not,but had significant effects on average rooting numbers,average root length and one-side rooting percentage.Culture temperature had significant effect on rooting percentage,average rooting numbers and average root length but had no significant effect on one-side rooting percentage not.Fuzzy comprehensive evaluation analysis suggested that the rooting quality of the microcuttings were best(higher rooting numbers,longer root length and lower one-side rooting percentage) and the rooting percentage reached 100%when rooting was conducted on WPM medium supplemented with IBA 0.50 mg·L^-1,sugar 25 g·L^-1,agar 7 g·L^-1,with adjusting its pH to 5.8 before autoclaving and maintaining culture temperature at 25℃.(2) The rooting medium,auxins and culture temperature had significant effects on rooting percentage,average rooting numbers,average root length and one-side rooting percentage of the cross clone,concentration of auxin,light intensity and substrate moisture had no significant effects on the rooting percentage but had significant effects on average rooting numbers, average root length and one-side rooting percentage.Fuzzy comprehensive evaluation analysis suggested that the rooting quality of the microcuttings were best(higher rooting numbers, longer root length and lower one-side rooting percentage) and the rooting percentage reached 100%when rooting was conducted on rooting medium of 25%peat moss+ 30%vermiculite+ 45%perlite,pre-treating microcuttings with IBA 300 mg·L^-1 for 3-5 s,maintaining culture temperature at 20℃,light intensity in 75μmol·m^-2·s^-1 and rooting medium moisture at 50%.(3) The PPO activity and soluble sugar content appeared to decrease first and then increase and the POD,IAAO activity and soluble protein content appeared to increase first and then decrease when microcutting were rooted in vitro.The indexes of those would be increased and then beneficial for rooting when treated by IBA.(4) The soluble sugar content appeared to decrease and the POD,PPO,IAAO activity and soluble protein content appeared to increase first and then decrease when microcutting were rooted ex vitro.The indexes of those would be increased and then beneficial for rooting when treated by IBA.