Effects of growth regulators on nursery rooting and seedling growth of hybrid larch

Based on rooting experiments of summer semi-hardwood cuttings of hybrid larch(Larix leptolepis×L.olgensis) in the Dagujia Forest Farm,Liaoning Province,the authors analysed the effects of various plant growth regulators or commercially available rooting compound(ABT rooting promoter) on the rooting ability and growth of rooted cuttings using variance analysis and LSD tests. Suitable growth regulators or rooting compounds and their optimal concentrations are recommended.The results show that there was no significant difference in rooting ability among hybrid families and interaction effect between growth regulator treatments and hybrid families.Suitable treatments of growth regulator and concentration affected the rooting ability and significantly improved the root number per cutting and one-sided rooting rate of rooted cuttings.Although the concentrations of IBA had no significant effect on the survival rate of rooted cuttings,nursery tree heights and base diameters were all higher than those of water controlled treatments.The higher concentration of IBA(400 mg/L) and rooting compound,especially compound L₄,had significantly improved rooting ability and root quality;the percentage of rooted cutting was up to 93%,mean root number per cutting was 9.4,but the one-sided rooting rate of rooted cuttings was only 4.5%.