Ucar Turker a, Yucesan, B, and Gurel E. 2010. Adventitious shoot regeneration from stem internode explants of Verbena officinalis L., a medicinal plant. Turkish Journal of Biology. 34: 297-304. Scientists have discovered that new plants can be grown from pieces of old plants through a process called "plant tissue culture." In this process, pieces of plants are placed in a media containing specific growth regulating chemicals, and from this a whole new plant can be grown. And the new plant will be a genetic duplicate of the old plant. The authors of this study tested whether different parts of a specific plant, called Verbena officinalis, could be better at producing a whole new plant through the process of plant tissue culture. By taking different parts of the plant, and growing them on media containing a different amounts and concentrations of plant growth regulating chemicals, the authors were able to determine which parts of the plant, grown under which conditions, would be best able to produce new plants.

The experiment was divided into two parts: the growth of the shoots, and the growth of the roots. The authors first experimented with the shoot regeneration process by sprouting Verbena officinalis seeds and letting them grow for a number of weeks. They then took the young Verbena plants divided them into leaves, petioles (the part between the stem and the leaf), and internode sections (part of the stem); and...

The pieces of each part were then place in a specific growth inducing media containing IAA (indole-3-acetic acid) combined with one of the following growth regulators: BA (benzyladenine) or TDZ (thidiazuron), all at varying concentrations.
The results indicated that the stem internodes were the best part of the plant to generate shoots from while using TDZ in conjunction with IAA. The auxin IAA seems to be a necessary component, however, the authors do not state whether BA or TDZ was the better for what and leave it up to the reader to scan the data charts to discover that IAA used with BA increased the percentage of petiole explants forming shoots, but IAA used with TDZ increased the percentage of internode explants actually forming shoots. And, since overall it was the internode explants that performed the best, the authors chose them for the next part of the experiment. Leaves did not produce any results at any concentrations of growth regulators, and were therefore discarded.

The authors then seem to jump to the conclusion that since IAA seemed to be the important component and since it was an auxin, then perhaps other auxins would be as effective or better. In this part of the experiment they used the different auxins IAA, IBA (indole-3-butyric acid) and 2,4-D (2,4 dichlorophenoloxyacetic acid), and NAA (naphthalene acetic acid), and discovered that when it came to the number of…