Cutting Propagation Technique And Rooting Mechanism Of Taxodium Distichum(L.)

Taxodium distichum (L.) is a venerable and relic plant originating from North America, which now is introduced to being planted all over the world. It's excellent for the production of timber, shelter belt and ornamental purpose with many virtues, just like rapid growth, graceful shape of tree, widely adapted planting and excellent wood property. The cutting propagation technique and rooting mechanism of Taxodium distichum (L.) was studied. The main results were as follows:(1) There were significant differences among the different provenances of thirteen year-old Taxodium distichum (L.) and the different orientations, layers of tree crown in rooting characters of cuttings. The root effective indexes had a positive correlation with the rooting rate and the quantity of roots at 0.05 level. As a whole, the rooting ability of provenances 17, 10, 30 was stronger than the others, and the cuttings of the upper layer of tree crown in east and south was better for root-promoting.(2) The experiment using the cuttings which selected from one year-old parent plants indicated that the rooting characters of cuttings was significantly influenced by exogenous hormone, concentration and treatment time. The best root-promoting agent was IBA, ABT followed, and NAA was the poorest. The best treatment concentration was changed with exogenous hormone. Long treatment time was favorable for the rooting ability, but adverse to the growth of the root diameter. The optimal rooting mediums were ABT×200ppm×6h, IBA×150ppm×6h, and IBA×100ppm×6h. The cuttings which were made of the middle of and the base of current-year-old hardwood branches had higher rooting rate for hard wood cutting, and the ones that made of the upper of and the middle of current-year-old softwood branches were better for green wood cutting.(3) The rooting rate had a positive correlation with dissoluble sugar content, amylum content, carbohydrates content, dissoluble protein content, C/N value, but had a negative correlation with the total nitrogen content. The content of amylum could be a judgement standard for rooting ability of cuttings. Most of the content of nutritive substance declined with the emergence of callusing and rooting. The conventional rule of C/N value didn't suit for Taxodium distichum (L.).(4) Compared with CK, the content of IAA, GA3 and the value of IAA/ZR, IAA/ABA of cuttings which were treated by ABT ascended, but the content of ZR and ABA declined. The relative analysis indicated that the rooting rate had a positive correlation with the content of IAA and GA3, and the value of IAA/ZR and IAA/ABA, and had a negative correlation with the content of ZR and ABA. The value of IAA/ABA could be a judgment standard for rooting ability of cuttings.The accumulation of IAA and GA3 speeded the emergence of callusing and rooting. The higher content of ZR at prophase, and lower content of ZR at anaphase were beneficial to rooting. The declining of the value of IAA/ZR was beneficial to callusing, the other way around was beneficial to rooting. The higher value of IAA/ABA was better for root-promoting during the shape of rooting anlage and the emergence of root.(5) Exogenous hormone increased the activity of POD and PPO, and decreased the activity of IAAO. The rooting rate was positively correlated with POD and PPO, and negatively correlated with IAAO. IAAO and POD affected rooting rate through adjusting the content of IAA, but PPO affected rooting rate through creating "IAA-Hydroxybenzene-Acid".