Ucar Turker A, Yucesan, B, and Gurel

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 cut them into pieces. 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 roots per shoot, 4.92 M. Of IBA was the auxin and the concentration which gave the best results. But in terms of the overall percentage of shoots that rooted, then 5.71M of IAA was the best auxin and concentration.

It turns out that the regeneration efficiency, the efficiency at which the different parts of the plant were able to regenerate both shoots and roots, was higher in the stem internode part of the plant than in the petiole part of the plant, but only when using the auxin IAA in conjunction with TDZ. The authors also discovered that an auxin was absolutely necessary as one of the growth regulators; and without the auxin IAA, the other regulators did not produce any results. Next they discovered that the regeneration of the roots supplemented with IBA had more roots per shoot, but, in terms of the percentage of shoots that actually rooted, the shoots that had been grown with IAA had a higher percentage. In other words, shoots grown in IAA had a better chance of rooting, but shoots grown in IBA gave the higher number of roots per shoot.

The purpose of this study was to discover a procedure for regenerating the plant Verbena officinalis. It was to discover what part of the plant was best for use in regeneration, as well as which combinations and concentrations of growth regulators were necessary. In this the authors were successful and have created an efficient protocol for doing so. It requires the stem internodes of Verbena officinalis grown in IAA to produce shoots, and then grown in IBA in order to produce roots.