The Adaptive Characteristics Of Pyrus Sinkiangensis Yü Seedlings In Vitro

In this experiment, Pyrus sinkiangensis Yü, a woody tree with a poor rooting ability, was chosen as material. The effect of macro elements on rooting and propagation characteristics of Pyrus sinkiangensis Yüseedlings in vitro were researched and main factors were concluded. Through media adjustment and environmental optimization, this paper aimed to improve in vitro culture quality of this plant and conclude efficient in vitro culture solutions. The results were as follows:1. Rooting of pear was affected by many factors. Except environmental factors, such as temperature, light and moisture, the growth quality and hormone concentrations during propagation stages also influenced in vitro rooting. ANOVA indicated that different hormone concentrations and explants could have significant effect on rooting. Thus, in order to achieve a better rooting effect, seedlings should be cultured on media with a low concentration of hormones before in vitro rooting.2. Using path analysis, the effect of N, K, Ca, Mg on in vitro rooting of pear was studied. Macro elements had both direct effects and indirect effectes on rooting. Mg had significant correlation with rooting rate and Ca had extremely significant correlation with rooting rate. Among the four kinds of macro elements, Ca had the highest total effect. So during media optimization of woody plants with a poor rooting rate, the interactions among elements should be considered and special attentions should be paid on important macro elements.3. Morphologic and photosynthetic traits of rooting plantlets on media generated by uniform design, comparing and selecting approach, and nutrition analysis were compared and analyzed. The result showed that the photosynthesis was correlated to growth characteristics, such as the rooting rate, expanding leaves, stem length and so on. This indicated that different rooting medium could influence the photosynthetic capability apparently. Adjusting the component of basic medium was an efficient technique to improve photoautotrophic growth of plantlet. If connect with the photoautotrophic measures such increase CO2 concentration and enhance light density in current tissue culture, a further excellent result could be achieved.4. The influence of cytokinin and agar on vitrification was studied through setting different levels of their concentrations. The results indicated that MS medium supplemented with NAA0.5mg.L-1,6-BA2.0mg.L-1 and agar 7.0g.L-1 could reach a high multiplication rate and had a low vitrification rate. So it was suitable for multiplication of this kind of plant. Mechanism for appearance of vitrification was researched based on measurement of physiological parameters. Vitrified seedlings and normal seedlings in vitro had dramatic differences in SPAD value of chlorophyll content. Significant differences were observed in water content between the two kinds of seedlings. There was no significant difference in fluorescent parameters between the two kinds of seedlings in vitro. We concluded that PSⅡof vitrified seedlings in vitro was not impaired. The reason why vitrified seedlings had a low photosynthesis rate lied in their poor light absorption ability, rather than in the light transformation stage.5. Five macro elements(N,P,K,Ca,Mg) in three kinds of materials(a whole seedlings in vitro, leaves of field plants, a mixture of stems and leaves of field plants) were analyzed, respectively. Based on plant nutrient analysis methods proposed by Philippe and Gon?alves, several rooting media were optimized. Media optimized following different methods differed largely in total NH4+, NO3- and PO42-. Following Gon?alves's methods, G1 was derived from nutrient analysis of a mixture of stems and leaves of field plants. The rooting rate of G1 (92.7%) was significantly higher than P2, which was a medium optimized following Philippe's methods. In addition, materials had a great influence on rooting rates. Rooting rates of G1 was significantly higher than G2 (medium based on leaves nutrient analysis). So we concluded that both materials and methods affect rooting rates of seedlings in vitro. In order to achieve a satisfactory in vitro rooting rate for species with a poor rooting ability, methods proposed by Gon?alves could be adopted and functional stems and leaves should be chosen for nutrient composition analysis.From the aspect of medium optimization, this research analyzed the plastic variation of nutrition demands of in vitro seedlings. This study paid special attentions to the coordination between growth quality and culture efficiency, and optimized media based on adaptation. The results of this study could provide more efficient theoretic guidance for the development of in vitro propagation theories.