Cutting Propagation Technique And Rooting Mechanism Of Old Platycladus Orientalis

Old trees are special kind of landscape elements that create a unique landscape value. However, many factors makes the old trees’ growth vigor decline, so protecting the breeding and rejuvenation has important significance. Platycladus orientalis has a long history of cultivation in China. The cutting propagation of veteran oriental arborvitae tree characterized by low rooting rate, rooting time is long, that lead to the reproductive difficult. In order to improving the rooting rate of old tree of P.orientalis, and providing the theoretical basis and technical support of asexual reproductive technology, The paper conducted the cutting propagation experiments with different ages trees to select the best combination on cutting. Then we continued in-depth studies on the dynamic change such as nutrient content, enzyme activity, endogenous hormone content and endogenous inhibiting substance on the basis of the optimal combination in experimental results. The specific findings were as follows:(1) Cutting trials indicated that:Low concentrations of the exogenous hormone treatment for 5-year-old P.orentalis cuttings had the best effect, while middle concentrations of the hormone treatment were more suitable for 100-year-old, 300-year-old and 700-year-old P.orientalis cuttings. Meanwhile, the cuttings treated by 1000 mg.L-1 NAA: IBA(1:1) produced the highest rooting percentage. When we used the ASL instead of the exogenous hormones, the results showed that low concentrations for 5-year-old and 700-year-old P.orientalis cuttings effect was the best, while the rooting rate of cuttings in middle concentration was the highest for 100-year-old and 300-year-old cuttings. In a word, the treatment by ASL produced high rooting percentage value than NI on the rate of radication.(2) By observing the rooting process of adventitious roots, we could see that the adventitious were originated from callus tissue and lenticels. The formation of adventitious roots of the cuttings was divided into three stages:0-35 days for callus induction and formation stage; 35-65 days for adventitious roots formation stage; 65-95 days for adventitious roots elongation.(3) In the process of different age of trees cuttings, the level of soluble sugar, starch and soluble proteins presented differently, and there was no specific relationship with ages. Overall, the relationship between the change of nutrients and the energy needed of rooting was ebb and flow.(4) Before cutting, in addition to the 5-year-old cuttings,the others’ activity of PPO and POD decreased with the increasing ages, while the activity of SOD increased with the increment of age. MDA was viewed as the adversity physiological indexes, Its content increased with the increasing age.(5) The paper founded that the relationship between cuttings of different ages and endogenous hormone content were closely. At different stages of rooting, the roles of endogenous hormones were different. The increased of GA was more conducive to the formation of adventitious roots in callus induction period, IAA and ABA content and rooting ability showed a negative correlation, and the content of ZR and the rooting ability positively correlated. Besides, the IAA / ABA ratio was more conducive to rooting, and the larger the IAA / ZR ratio, the more conducive to the formation of adventitious roots.(6) Measured by high performance liquid chromatography before cutting, we could see that the content of phenols and flavonoids in five years old P. orientalis cuttings were higher in June than those in other months; The content of flavonoids in cuttings of P. orientalis of 100-year-old and 700-year-old in August were higher than those in other months, and the content of phenols had a maximum value in June; The content of flavonoids in 300 years old P. orientalis cuttings had a maximum value in June, while the content of phenols had a maximum value in August; Bioassay showed that with the increase of the concentration of leaching liquor, the inhibiting effect on sprouting of Brassica pekinensis increased. By comparison, the influence of endogenous inhibitors on the growth of Brassica pekinensis roots was higher in June; The leaching liquor from the middle of sunny side had the maximum inhibiting effect on the sprouting of Brassica pekinensis, whereas the leaching liquor from the top of night side had an bigger inhibitory effect on the growth of Brassica pekinensis.