In this study, we investigated the roles of the plant hormones indole-3-acetic acid (IAA) and gibberellin (GA) in regulating Pinus massoniana Lamb. plantlet regeneration during long-term in vitro subculture. Six generations (1st, 5th, 10th, 20th, 30th and 40th with 40 days for each transfer cycle) of subcultured shoots derived from mature and juvenile explants were characterised for their different rooting capacities. In the present experiment, shoots were subcultured on rooting medium containing indole-3-acetic acid (IAA), naphthaleneacetic acid (NAA) or gibberellin (GA) inhibitor (paclobutrazol, PBZ). In addition, high-performance liquid chromatography (HPLC) was used to analyse endogenous hormone levels in shoots developed on medium with low concentrations of NAA. The concentration of endogenous IAA was highest in the 20th generation shoots, which also exhibited the strongest rooting ability. However, the highest GA concentration was observed in the 40th generation shoots, which exhibited a poor rooting capacity. For shoots subcultured for 40 generations, incubation on rooting medium containing IAA caused an enhanced root number, shoot length and survival rate. This suggested that the effects of IAA on shoot and root formation were positive. PBZ promoted plantlet regeneration from in vitro cultures but impaired shoot elongation at high levels. Furthermore, PBZ improved performance of in vitro cultures after long-term (3 to 4 y) subculture. These results suggest the inhibitory role of a high endogenous GA level in plant regeneration and the use of appropriate levels of PBZ for plant regeneration of P. massoniana.

在这项研究中，我们调查了植物激素吲哚-3-乙酸（IAA）和赤霉素（GA）在调控马尾松羔羊中的作用。长期体外植株再生亚文化。从成熟和幼小外植体衍生的六代（第1、5、10、20、30和40代，每个转移周期为40天）的特征在于其不同的生根能力。在本实验中，将芽在含有吲哚-3-乙酸（IAA），萘乙酸（NAA）或赤霉素（GA）抑制剂（paclobutrazol，PBZ）的生根培养基上传代培养。此外，高效液相色谱法（HPLC）用于分析在低浓度NAA培养基上发育的嫩芽中的内源激素水平。内源IAA的浓度在第20代芽中最高，也表现出最强的生根能力。然而，在第40代芽中观察到最高的GA浓度，这显示出较差的生根能力。对于传代培养40代的新芽，在含有IAA的生根培养基上孵育会增加根数，增加芽长和提高成活率。这表明IAA对芽和根形成的影响是积极的。PBZ促进了幼苗的再生体外培养，但在高水平下会损害枝条伸长。此外，PBZ在长期（3-4年）继代培养后提高了体外培养的性能。这些结果表明高内源GA水平在植物再生中的抑制作用和适当水平的PBZ用于马尾松的植物再生中。