影响喜树组织培养苗离体生根的因素

为了建立有效的喜树(Camptotheca acuminata)组培苗生根系统，提高其移栽成活率及适应性，用不同生长素种类及浓度、不同蔗糖浓度及不同培养基对喜树组培苗不定根形成影响以及移栽初期根系发育状况进行了研究。结果发现: 1)生长素种类和浓度明显影响喜树组培苗不定根形成，在含有IBA0.5 mg.L-1培养基中取得了最佳生根效果，生根率达到了98%，外植体平均生根数为5.9条/株; 2)不同浓度蔗糖对喜树组培苗生根也有一定影响，在10~30 g.L-1范围内，随着蔗糖浓度增加，生根百分率和生根数量都有增加，蔗糖浓度达到30 g.L-1时，生根百分率为95%，外植体平均生根数为5.4条/株; 蔗糖浓度在40 g.L-1时，表现出对生根抑制作用; 3)在基本培养基对喜树组培苗生根影响研究中发现，MS培养基对根形成表现出一定抑制作用；1/2MS和WPM培养基均适合喜树组培苗生根; 4)根系发育正常的喜树组培苗移栽后成活率可达96%，但组培苗根系根毛系统发育较差。组培苗单位叶面积根尖数量显著低于对照实生苗，而且此参数与叶片气孔导度呈显著正相关。这种较差根系发育导致叶片气孔导度过低可能是组培苗叶片光合能力较低的重要原因。

Factors Affecting in vitro Rooting of Camptotheca acuminata

For establishing an efficient in vitro rooting protocol of Camptotheca acuminata and improving the survival and acclimatization of the regenerated plantlets, the effects of auxins, sucrose concentration and different basal media on in vitro rooting and root development at ealier stage after transferred to soil were investigated in this study. We found that, firstly, the addition of auxins to the media can evidently promote rooting. The best rooting was found on the medium containing IBA 0.5 mg.L-1. In this medium, rooting frequencies reached 98%, which associated with a high number of roots, 5.9 roots per shoot. Secondly, root percentage and root number increased with the sucrose concentration from 10 g.L-1 to 30 g.L-1. On the medium containing 30 g.L-1 sucrose, root percentage was 95% with higher root number, 5.4 roots per shoot. Higher sucrose concentration (40 g.L-1) negatively affected rooting. Thirdly, of different medium for rooting, MS medium inhibited root formation. WPM or 1/2MS medium was the optimal medium for in vitro rooting of C. acuminata. Ninety-six precent of the in vitro rooted plantlets with well developed shoots and roots survived after transfer to soil. But root system was much worse than that of seedlings developed from seeds, and the ratio of root tip number to leaf area in regenerated plantlets were significantly lower. Moreover, this ratio was positively correlated with stomatal conductance. The worse root status and low stomatal conductance may be the important reason for the low photosynthetic capacity of regenerated plantlets.