Thursday, 28 August 2014

Spontaneous Verbena bonariensis mutation



Earlier this year I grew some Verbena bonariensis plants from a free packet of seed that dropped out of a magazine. The seed grew very well but the plants have turned out to be an interesting mutated form of the more usual herbaceous border favourite.

To see the usual form of the plant have a look at the Wikipedia photo. As you can see the stems produce a large flat head with many many tiny pink flowers. The two photos below show one of these flat heads from the side and the top. 


Verbena bonariensis - the herbaceous border favourite.
The reproductive structures seen from the side. 

Verbena bonariensis - the herbaceous border favourite.
Reproductive structure seen from above. 

So much for the normal form. Now to this interesting mutant form. There are a couple of photo below showing the reproductive structures from the side.

Verbena bonariensis; un-named mutant form. Reproductive structure seen the from the side. 

Verbena bonariensis; un-named mutant form. Reproductive structure seen the from the side. 

So what's going on with these mutant plants? It seems to me that usual form of the plant produces a large flowering shoot, with a cluster of many short inflorescences at the top. Each inflorescence terminates in a large number of small flowers. (I'm tempted to give an analogy for the newcomer here, but fear that I would be toasted for over-simplifying the subject into nonsense.)

The mutant form, by contrast, has a flowering shoot that carries a smaller number of long inflorescences. Each inflorescence terminates in a smaller number of rather small flowers. 

This mutation seems to correspond, to some extent, with the floricaula mutant of Antirrhinum majus, which produces many inflorescences, but never makes the transition to producing actual flowers.

The floricaula mutant of Antirrhinum majus


This image shows the floricaula mutant and wild type forms of Antirrhinum majus

This image comes from the work of Enrico Coen and Rosemary Carpenter
at the John Innes Centre in Norwich.
 It shows the floricaula and wild type forms of Antirrhinum majus.
(The image comes from http://rico-coen.jic.ac.uk/index.php/File:Flo2s400.jpg)

The floricaula mutant plants are very conspicuously different from wild type when viewed from the side. The wild type plants produce large showy flowers, but in the place of these flowers the floricaula mutants produce only green inflorescences, with no flowers at all. 


Back to Verbena...


So does the Verbena bonariensis show a floricaula-type mutation? Well I don't know, and neither will anyone else, because no one funds this kind of research. Isn't it fun to wonder about it though? 

Keep wondering, all you itinerant botanists!