Study On Techniques For Softwood Cutting And Planting Stock Development Of Catalpa Bungei Under Automatic Controlled Environmental Condition

Catalpa bungei C.A.Mey. which belongs to lagerstroemia family, Catalpa genus, is a high-value timber wood species and good ornamental trees in landscapes and gardens. The propagation and application of the superior varieties of Catalpa bungei is restricted by its special biological character, i.e., self-sterility and poor rooting ability of cutting cuttage etc.. The main propagation method is grafting Catalpa bungei scions on Catalpa ovata stocks. Recently, softwood cutting is the main techniques to be researched for the propagation and planting stock development of Catalpa bungei. The rooting rate of softwood cutting on Catalpa bungei appeared very low in former researches. The main reason of it is the precise requirements on environmental factors during the rooting period while the traditional cultural facilities for cutting propagation can not reach it. In this paper, an automatic control greenhouse which has been constructed with the design and technology from New Zealand have been used in research on softwood cutting propagation of 5 varieties of Catalpa bunge, i.e. Yanjichangguo, Yuqiu-1, Yuqiu-2, Zhouqiu-2, Zhouqiu-3 in 2007²008. The operation and maintenance metheds of the automatic control greenhouse, softwood cutting production method, softwood cutting propagation method, as well as hardening treatment method, transplanting method and field culture methods of rooted cutting plants related to the techniques for softwood cutting propagation and palnting stock development of Catalpa bungei were researched within methodology of contrast experiments and from the summing up experiences. We expect to achieve an integrated technology about softwood cutting propagation and palnting stock development of Catalpa bungei by using of the automatic control greenhouse. This would be a key techniques for guiding the production practice of Catalpa bungei palnting stocks, which will promote the application of superior varieties of Catalpa bungei and their plantation development.The main results and conclusions were summarized as follows:(1) Using 1 year old grafted stems of Catalpa bungei varieties and burying them in sand beds for developing cutting shoots is a suitable way to produce softwood cuttings with the fast growth and high yield. In 20 days after stem buried, the 48.35% sprounts on the stems can grow up to the height for making cuttings. The highest yield of cutting shoots per unit length of stem can be 4.24 /m. The sprout's growth rate and yield varied among the varieties of Catalpa bungei. The order of sprouts growth rate of 5 varieties is: Yuanjichangguo > Zhouqiu-3 > Yuqiu-1 > Yuqiu-2 > Zhouqiu-2. The order of cutting shoots yield per unit lenghth stem of the 5 varieties is Zhouqiu-3 > Yuqiu-2 > Zhouqiu-2 > Yuqiu-1 > Yuanjichangguo.(2) Hormone treatment on cutting wood will promote the rooting in softwood cutting on Catalpa bungei. The high rooting rate and better rooting trait were achieved when softwood cutting woods were treated with quick dipping of 1000mg·kg^-1 ABT-1 or 1000mg·kg^-1 NAA hormone with talc powder mixture. These are the best hormone treatment for softwood cutting of Catalpa bungei.(3) The impact of different medium formulas on rooting is significant. The mixture of peat: perlite=1:1 is the best medium formula for softwood cutting of Catalpa bungei.(4) Using the combination of the best hormone treatment and medium formula for softwood cutting of Yuanjichangguo Catalpa, i.e. quick dipping of 1000mg·kg^-1 ABT-1 and medium formula of peat: perlite=1:1 can achieve a good rooting trait with rooting rate of 83% on average.(5) The rooting rate of Yuanjichangguo, Yuqiu-1, Yuqiu-2, Zhouqiu-2, Zhouqiu-3 of Catalpa bungei in softwood cutting appears significant different. For the cuttings made from buried stems, the order of the rooting rate of 5 varieties is: Yuanjichangguo > Zhouqiu-2 > Yuqiu-2 > Yuqiu-1 > Zhouqiu-3; for cuttings made from field cutting collection plants, the order of the rooting rate of 5 varieties is: Yuanjichangguo > Zhouqiu-2 > Yuqiu-1 > Yuqiu-2 > Zhouqiu-3. Yuanjichangguo had the highest rooting rate, 81.29% for cuttings made from buried stems and 62.70% for cuttings from field cutting collection plants. In average, the rooting of rate of cuttings made from buried stems is higher than that made from field cutting collection plants. Therefore, the cutting development method with buried stems in greenhouse is the preferable way for producing of softwood cuttings of Catalpa bungei.(6) For cuttings from field collection plants of Catalpa bungei, choosing the tpart of the 1 year shoots by cutting it from 0.5 cm above the node into 8～12cm long as cuttings, which can achieve the highest rooting rate. It should be the criteria for making the best for most satisfied cutting propagation results.(7) Two step hardening of rooted cuttings developed from the automatic control greenhouse, i.e. 14 days in the greenhouse and 14 days outside the greenhouse under shade, is a suitable way to accomplish hardening of rooted cuttings, which can achieve 95.93% of transplanting survival rate of the rooted cuttings. The transplanting and field management methods of rooted cuttings for this research were suitable for developing health and strong planting stocks. For example, the height and root collar diameter of rooted cutting of Yuanjichangguo Catalpa were 50cm and 1 cm in 60 days of the transplanting into the field, with height incremental of 34cm.