Propagation Techniques And Rooting Mechanism Of Soft Cutting Of Betula Costata And Betula Pendula

Betula costata has the characteristics of long natural tree age,extreme cold resistance,rapid growth and excellent material.Betula pendula is a medium-sized deciduous tree.Its leaf color changes with seasons.It is a good timber tree and landscaping tree species.The semi lignified twigs of 2-3-year-old Betula costata and Betula pendula were used as cutting materials.The cutting propagation technology and rooting mechanism of Betula costata and Betula pendula were studied from the aspects of matrix,sampling position,hormone species,hormone concentration,treatment time and putrescine.The cutting propagation of two tree species was preliminarily explored.The results were as follows:（1）The results of five factors and three levels orthogonal test showed that each factor had a significant impact on the cutting rooting of Betula costata and Betula pendula,and the influence of the cutting position was the largest.Among the Betula costata cuttings,the cutting effect of treatment 16[substrate 3（Vermiculite+fine river sand+peat soil）+slight cuttings+500 mg·L^-1 ABT+treatment for 30 min]in Betula costata was the best,and the rooting rate was 38.89%;Among Betula pendula cuttings,treatment 4[substrate 2（Vermiculite+coarse sand+peat soil）+slight cuttings+500 mg·L^-1 IBA+treatment for 30 min]had the best rooting effect,with a rooting rate of 47.78%.（2）The results of putrescine experiments showed that different concentrations of putrescine treatments had significant effects on the rooting of Betula costata and Betula pendula.The rooting effect of Betula costata cuttings in treatment 1(500 mg·L^-1putrescine+500 mg·L^-1ABT)was the best,and the rooting rate was 26.67%.The best rooting effect of Betula pendula cuttings in treatment 2(500 mg·L^-1 putrescine+500 mg·L^-1IBA)was the highest root rate of 42.67%.（3）Rooting types of Betula costata cuttings were mostly originated from cortex,small number cuttings were originated from the mixed rooting type.Rooting types of Betula pendula cuttings were mostly originated from cortex,small number cuttings were originated from the callus and the mixed rooting type.The formation process of adventitious roots in cuttings could be roughly divided into three stages:callus formation stage（0-12 days）,adventitious root expression stage（12-24 days）,and adventitious root elongation period（after24 days）.（4）The use of exogenous hormones had a significant effect on the endogenous hormones of Betula costata and Betula pendula cuttings.ABT treatment of Betula costata cuttings increased the values of IAA,GA₃,IAA/ABA and IAA/ZR,but decreased the contents of ABA and ZR.IBA treatment of Betula pendula cuttings increased the values of IAA,IAA/ABA,IAA/ZR,and decreased the contents of ABA,GA₃ and ZR.The lower concentration of ABA was beneficial to the formation of adventitious roots,and the gentler IAA/ZR value was beneficial to root growth.（5）During the rooting process of Betula costata cuttings,IBA treatment increased the PPO activity of the control group,the enzyme activity of the treatment group reached a peak at the root development stage,and the change of the control enzyme activity was later than that of the treatment group.The activities of SOD showed an increase-decrease trend,SOD activity continued to increase before adventitious roots,and hormone treatment increased SOD activity.During the rooting process of Betula pendula,the activities of PPO showed an increase-decrease trend,and the change of SOD activity was increase-decrease.（6）During the rooting process of Betula costata,the change trend of soluble sugar content was decrease-increase-decrease,and the starch content in the treatment group showed a decrease-increase trend.The soluble protein content in the treatment group values showed a“down-up-down-up”trend,and the control group values showed a“down-up-down”trend.The content of soluble protein was much lower than that of soluble sugar and starch,and the rooting and growth of cuttings mainly depended on soluble sugar and starch for energy.During the rooting process of Betula pendula,the change trend of soluble sugar content showed a“down-up-down”trend.The starch content in the treatment group showed a“down-up”trend as a whole during the rooting process,and the control group showed a decreasing trend.The change trend of soluble sugar and starch was similar.Soluble protein content decreased during root formation.The changes in the treatment groups of the three nutrients were greater than those in the control group,and exogenous hormones promoted the metabolism of the nutrients.To sum up,through the cutting experiment of 2-3-year-old Betula costata and Betula pendula,combined with a variety of analysis methods,this study explored the effects of cutting medium,cutting position,hormone type,hormone concentration,treatment time and putrescine concentration on the rooting of cuttings.In the future,it is necessary to further study the cutting of Betula costata and Betula pendula in different seasons,different number of leaves left and different cutting length.