Effect Of Cutting Age On The Biochemical Feature Of Rooting Process And The Growth Of New-born Seedlings In Populus

Cutting propagation technology is widely used in practical production and it had broad prospects for development.However,accumulation of age effect of vegetative propagation materials would lead to the degradation of varieties.Therefore,it is of great theoretical and practical significance to study the age-effect mechanism of poplar cutting materials and promote the development of poplar forests.In this research,we chose hardwood cuttings of different ages of poplar hybrid’Beilin Xiongzhu 2’ as experimental materials.The physiological and biochemical characteristics of cutting skin during rooting were firstly analyzed and compared.The results showed as follows:(1)The contents of nutrients and hormones(IAA and GA)in the skin decreased with the increase of cutting age,while the contents of inhibitory substances(total phenol,malondialdehyde,superoxide anion,and ABA)increased.It showed that the contents of nutrients,IAA and GA in the cuttings were reduced with the increase of cuttings age,and the content of inhibitory substances(total phenol,malondialdehyde,superoxide anion,and ABA)were accumulated;(2)The activities of antioxidant enzymes(POD,SOD,PPO,CAT)were reduced with the increasing of cuttings age,which resulted in the accumulation of inhibitory substances.Besides,The IAAO enzyme activity increased with the increase of cutting age,resulting in the decrease of endogenous IAA content of cuttings,which led in slower rooting of the cuttings;(3)The expression of rooting genes PtANTl,PtAIL7,and PtPLT1 were significantly inhibited with the increase of cutting age.As a result,the rooting rate of ageing cuttings were reduced.On the other hand,physiological and biochemical characteristics of new-born seedling were analyzed.The results showed as follows:(1)The morphology index,net photosynthetic rate(Pn),and root development characteristics of the new-born seedlings gradually decreased with the increase of cutting age.On the contrary,the anatomy of the cuttings revealed that the older cuttings with degree of lignification was greater than the younger cuttings.The results showed that the growth status of new-born seedlings in older cuttings was poor,and the cuttings had a tendency of lignification.(2)The contents of leaves nutrient and hormone(IAA,GA)decreased with the increase of cutting age,while the contents of proline(Pro)and abscisic acid(ABA)were increased.It was shown that the leaves of the older plug seedlings had weak metabolic capacity and easily accumulated growth-inhibiting substances.Comprehensive analysis showed that the contents of nutrients,auxin and gibberellin in the older cuttings were reduced,while the oxidative substances,secondary metabolites and abscisic acid were accumulated,and the antioxidant enzyme activity and rooting-related gene expression were reduced.The combination of these factors resulted in a decrease in rooting quality and rapid plant growth of the cuttings,showing an aging state of growth retardation.