Department of Vegetable Crops, Cornell University, Ithaca, New York 14853.
Plant Physiol. 1978 Mar;61(3):348-53. doi: 10.1104/pp.61.3.348.
The intensity of "tuberization stimulus" in potato shoots (Solanum tuberosum L.) can be assessed from cuttings containing one or more leaves. Cuttings maintained in a mist chamber under long days will form tubers from underground buds if prior to taking the cutting the leaves received sufficient exposure to photoperiods less than the critical photoperiod. The greatest tendency to tuberize was found in cuttings that consisted of a single, fully expanded leaf and its subtended bud. Grafts showed that genetical differences in critical photoperiod resided in properties of the leaf. Short days before cutting tended to shift growth from above ground buds of two-node cuttings to below ground buds, even if the number of short days was insufficient for tuber induction. As few as 6 short days reduced growth of shoots at the upper bud and increased underground growth of shoots and stolons.
马铃薯（Solanum tuberosum L.）嫩枝的“结薯刺激”强度可以通过含有一片或多片叶子的插条来评估。在长日照下置于雾室中的插条，如果在取插条之前叶子接受的光照时间短于临界光周期，那么就会从地下芽形成块茎。在仅由一片完全展开的叶子及其下的芽组成的插条中，结薯的趋势最大。嫁接表明，临界光周期的遗传差异存在于叶子的特性中。在切割前的短日照会促使二节插条的地上芽的生长转移到地下芽，即使短日照的天数不足以诱导块茎形成。即使只有 6 个短日照，也会减少上部芽的枝条生长，增加地下枝条和匍匐茎的生长。
