| Chinese pine(Pinus tabuliformis) is a member of Pinus, Pinaceae. It is endemic to China, mainly distributed in Jilin, Liaoning, Henan, Hebei, Shanxi, Shandong, Inner Mongolia and other 15 provinces (municipalities and autonomous regions). It is one of the most important afforestation tree species in the area of northern China. In addition, it can keep the water and soil and beautify the environment because of the strong adaptability, developed root system, magnificent attitude and lush foliage.The objective of this study was to establish a model system with high frequency of adventitious rooting in P. tabuliformis. The adventitious buds and hypocotyl cuttings were used as materials and plant tissue culture as principal technology, by adjusting the medium (auxin as a main factor). On this basis, morphological, histological and physiological changes during adventitious rooting in this species were investigated. It aimed to provide an experimental basis for exploring the internal physiological mechanism of adventitious rooting in conifers. The results are as follows:(1) Hypocotyl was more suitable for adventitious rooting in P. tabulaeformis than adventitious bud. It took as adventitious buds and hypocotyls cuttings from this species for materials. The result showed that, under the same conditions, the rooting percentage, average rooting numbers and length of the longest root were obvious higher in hypocotys than in adventitious buds. The rooting rate of hypocotyls was significantly higher than that of adventitious buds, reaching up to 83.33%.(2) The rooting rate of hypocotyls with all cotyledon was significantly higher than those removed of part cotyledon under the same condition. In 1/2 DCR medium containing 4 mg/L IBA, the rooting rate of hypocotyls with all cotyledon was the highest, to 76.67%, however, the rooting rate of hypocotyls removed of part cotyledon was only 26.67%.(3) The rooting situation of 2-week old hypocotyls was significantly better than 6-week old ones. The hypocotyls at 2-week and 6-week old were cultured in the same medium containing different concentration of IBA. It was found that the rooting situation of 2-week old hypocotyls was significantly better than 6-week old ones. The rooting rate of the former was as high as 86.67%, nevertheless, the latter was only 20.00%.(4) IBA promoted the adventitious rooting of p. tabulaeformis hypocotyls, but BA suppressed the adventitious rooting. When adding different concentration of IBA in culture, the hypocotyls formed adventitious roots in different degrees. And the rooting rate was significantly higher than that of control, up to 87.50%. When 4 mg/L BA was added in the culture medium, whether or not to cooperate with IBA, it was failed to induce adventitious roots.(5) When the medium was added 4 mg/L IBA, and pretreat for 15 days, the rooting rate was significantly higher than all other treatments, as high as 96.67%.The hypocotyls were respectively cultured in the medium containing different concentration of IBA for 5 days,10 days and 15 days, then transferred to the same medium removed hormones. The results showed that under the condition of containing the same concentration of IBA, the root situation through 15 days pretreatment was better than other treatments.(6) The time of different phase in adventitious rooting was established. Through the process of adventitious root morphological observation and anatomy study, it was found that the induction phase was from 0 to 6 days, initiation phase was during 6-8 days and development phase was from 9 to 15 days for culturing. There was not latent root primordia in hypocotyls cuttings in P. tabulaeformis, and adventitious roots developed from the induced root primordia, which originated from cortex parenchyma cells around resin canal right facing xylem ridges.(7) It was investigated that dynamic changes of physiological substance during adventitious rooting. The content of total soluble sugar firstly increased and then decreased during induction phase, always declined during initiation phase and continuously rised during development phase. The content of soluble protein showed up-down-up during induction phase, always increased during initiation phase and showed up-down during development phase. The activity of peroxidase (POD) displayed up-down during induction phase, increased during initiation phase and down-up during development phase. The activity of polyphenoloxidase (PPO) showed up-down during induction phase, no significant fluctuation during initiation phase and early no significant fluctuation, later gradually increased during development phase. The activity of indoleacetic acid oxidase (IAAO) showed down-up during induction phase, always declined during initiation phase and firstly increased then decreased slightly during development phase. |
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