油菜素内酯对巨桉组培中不定根诱导、苗木生长和茎基部细胞结构的影响

以巨桉优良无性系EG5和GL1组培苗为材料,在生根培养基中分别加入0、0.005、0.01、0.05、0.10、0.20 mg.L-1的油菜素内酯,研究其对桉树组培苗中不定根的诱导、茎的生长以及茎基部细胞分化的影响。结果表明：油菜素内酯对巨桉无性系EG5的生根率和苗高具有显著影响,无性系EG5在含有0.005 mg.L-1油菜素内酯的生根培养基中达到最高为76.6％的生根率,同时组培苗的苗高随着油菜素内酯浓度的增加而呈现出逐渐降低的趋势。对于巨桉无性系GL1,在生根培养基中添加0.05 mg.L-1油菜素内酯达到最高为88.3％的生根率,不同浓度的油菜素内酯对苗高没有显著影响。同时也发现油菜素内酯明显抑制了无性系EG5不定根的根长,随着其浓度的增加根长逐渐变短；而根条数表现为低浓度时无显著影响,在高浓度时显著性降低,且油菜素内酯对侧根的诱导和分化不起作用。另外通过对无性系EG5生根植株基部的组织切片和化学染色分析表明,油菜素内酯在0.10 mg.L-1时能促进桉树基部的形成层和木质部的分化,这可能是抑制不定根诱导和分化的原因之一。

Adventitious root induction, shoot height and cellular structure of basal stem by exogenous application of brassinosteriod in Eucalyptus grandis

Brassinosteroids(BRs)refer to a group of polyhydroxylated plant steroid hormones that are essential regulators of plant architecture, growth and development including embryogenesis, cell division, vascular system differentiation and stress tolerance processes. However, the effects of BRs in adventitious root induction of Eucalyptus have not been demonstrated. In this study, adventitious root induction, growth of shoots and histochemical staining of basal stem were analyzed by adding the exogenous brassinosteriod(Concentration: 0, 0.005, 0.01, 0.05, 0.10, 0.20 mg·L^-1,respectively)in the root inducing medium of E. grandis clones EG5 and GL1. The results showed that the height of shoot and induction frequency of adventitious root of E. grandis clone EG5 were significantly affected by adding the exogenous brassinosteriod. Induction frenquency of adventitious root was 76.6%. The length of adventitious root of E. grandis clone EG5 was the highest in the root inducing medium containing 0.005 mg·L^-1 brassinosteriod for. In the meantime. The height of shoot decreased significantly with the increasing concentration of exogenous brassinosteriod and it was reduced by 21.8% at 0.10 mg·L^-1 brassinosteriod concentration compared to control. The adventitious root induction frequency of E. grandis clone GL1 reached the highest level with 88.3% in the root inducing medium of adding 0.05 mg·L^-1 brassinosteriod concentration but the height of shoot showed no significant change by adding the exogenous brassinosteriod. It was interesting that the root elongation of E. grandis clone EG5 was significantly inhibited due to the addition of the exogenous brassinosteriod. Root length and number were reduced to 2.49 cm and 1.75 at 0.20 mg·L^-1 brassinosteriod from 4.64 cm and 3.02(control)respectively. However, the lateral root induction and differentiation were not affected by adding the exogenous brassinosteriod. Besides, the growth in xylary cells of basal stem was clearly promoted and the cambium cell number of basal stem increased at 0.10 mg·L^-1 brassinosteriod by way of the histochemical analysis. Together, brassinosteriods was necessary to adventitious root induction and shoot growth and increasing xylem was a primer cause of lower frenquency of adventitious root induction at a few extra brassinosteriod.