Institute of Forest Genetics, North Central Forest Experiment Station, United States Department of Agriculture Forest Service, Rhinelander, Wisconsin 54501.
Plant Physiol. 1972 Jun;49(6):886-92. doi: 10.1104/pp.49.6.886.
Intact brittle willows (Salix fragilis L.) were treated so that developing adventitious root primordia in the stems would be subjected to elevated gibberellic acid or reduced endogenous auxin levels. Observations were made of primordia that were initiated during the experiments and of primordia that were established before the experiments began. The results indicated that as primordia became older and contained more cells, auxin basipetally transported in the stem seemed to be of less importance in determining cell number per primordium. Thus, established primordia depended upon this auxin to a lesser extent than primordia which were being initiated. These observations were explained on the basis of differential contributions during primordium development of cell division in the cambium of the stem and in the primordia themselves. As opposed to the effects of reduced auxin levels, applied gibberellic acid reduced the cell number per primordium most in established primordia. Initiating primordia were least affected by gibberellic acid treatment. Gibberellic acid treatment seemed mainly to reduce intraprimordium cell division, on which continued development of established primordia most depends. Seemingly, at least in brittle willow, applied gibberellic acid blocks the action of auxin in primordium development subsequent to the initiation phase.
完整的脆柳（Salix fragilis L.）被处理，以使茎中正在发育的不定根原基受到高水平赤霉素或低内源性生长素水平的影响。观察了实验期间开始的原基和实验开始前建立的原基。结果表明，随着原基变得越来越老，包含更多的细胞，生长素在茎中向基运输似乎对每个原基的细胞数量的决定作用较小。因此，与正在开始的原基相比，已建立的原基对生长素的依赖性较小。这些观察结果是基于茎的形成层和原基本身在原基发育过程中细胞分裂的差异贡献来解释的。与降低生长素水平的作用相反，施加赤霉素酸在已建立的原基中对每个原基的细胞数量的减少影响最大。启动原基受赤霉素酸处理的影响最小。赤霉素酸处理似乎主要减少了原基内的细胞分裂，这是已建立的原基持续发育最依赖的。表面上，至少在脆柳中，施加的赤霉素酸阻断了生长素在起始阶段之后的原基发育中的作用。
