Studies On The Softwood Cutting Propagation Technique And Rooting Mechanism Of Ulmus Pumila Cv. Jinye

Ulmus pumila cv.Jinye was taken as test materials, with the upper part of one-year old branches as stem cutting, and each stem cutting retaining two leaves. In order to test the influence of different substrates on cutting, stem cuttings were treated with ABT of 1000 mg/Lsolution in 10s and inserted into eight soil substrates:river sand, perlite, vermiculite, peat, perlite:vermiculite=1:1, perlite:vermiculite=3:1 and perlite:peat=1:1, perlite:peat=3:1 (V/V) respectively. With the purpose of screening the best reagent concentration and the best treatment time for Ulmus pumila cv.Jinye cutting, experiments were conducted using three-factors three-level orthogonal tests:stem cuttings were treated with ABT, IB A, and NAA with three concentration gradients of 500 mg/L,1000 mg/L, and 1500 mg/L respectively in three periods of 10s,30s,60s and inserted into substrate of perlite:vermiculite=1:1 According to the change of endogenous hoemones, endogenous nutrient content and the ratio of the two parts as well as the observation of anatomical structure during cutting, we have a better understanding of the mechanism of Ulmus pumila cv.Jinye cutting, the results are shown as follows:(1) Vermiculite is the best soil substrate, the rooting rate of cuttings reached 89.17%, the average number of substrate on cuttings was 10, the length was 12.92cm, the longest root length was 38.5cm. Orthogonal tests showed that the rooting rate of stem cuttings treated with IB A of 500 mg/L in 30s reached 82.22% at most, the longest average root length reached 21.12 cm and the maximum average number of substrate on cuttings was 17. Using the method of multiple comparison by SPSS software, we concluded that the rooting rate of Ulmus pumila cv.Jinye cuttings could reach highest when their cutting bases were treated with IBA of 1500 mg/L in 30s.(2) The endogenous hormones during rooting changed as follows:IAA content decreased in callus formative period and increased in root primordia formative period, IAA content decreased in adventitious root formation and elongation period; low concentration of ABA was conducive to the formation of callus and adventitious roots; GA3 content increased in callus formative period; ZR content increased in callus formative period and adventitious root formation period. The ratio of IAA/ABA and rooting rate were positively correlated; low concentration of IAA/ZR was conducive to callus formation and root primordia elongation which could promote the formation of adventitious roots. During the process of rooting, endogenous nutrients of cuttings changed as follows:soluble sugar content decreased in callus formative period, root primordia formative period and in the period of adventitious root breaking through cortex and callus. The soluble sugar content increased during the period of starch hydrolyzation and adventitious root breaking through cortex and callus completely; soluble starch decreased in callus formation period and adventitious root formation period while increased when adventitious roots were formed completely, the soluble protein content increased during callus formation period while decreased during adventitious root formation period; the soluble nitrogen content decreased in callus formation period and adventitious root formation period; the soluble nitrogen content tended to be stable when adventitious roots were formed completely; high ratio of C/N could promote the growth and development of root primordial while the low ratio could promote the growth of branches. According to the change of endogenous hoemones and endogenous nutrient content, we concluded that the effects of cuttings using IBA and NAA together were better than using IBA only.(3) Observations of tissue sections showed that:there was no latent root primordia before cuttings were clipped, so was the situation in the callus. However, we found root primitive cells between phloem and cambium which would develop into root primordia in the future, and root primordia all extended from phloem. Therefore, Ulmus pumila cv. Jinye is phloem-initiation rooting species of inducible rooting type. When treated with IBA and NAA, root primordia formed in a short time and occurred at more sites, the number of adventitious roots was more, however, the roots were shorter than treated with IBA only. When treated with IBA, root primordia relatively formed in a long time, site occurrence was relatively less, the number of adventitious roots was less while the roots were longer than treated with IBA+ NAA.