Tuesday, August 25, 2009

Welwitschia Cones

Welwitschia mirabilis at the University of Connecticut.

Welwitschia mirabilis is a gymnosperm (cone bearing, non-flowering seed plant) endemic to the Namib Desert in southwestern Africa. Welwitschia is in a category of its own in the plant kingdom, morphologically speaking: seedlings produce exactly two foliage leaves before the shoot apex aborts. The resulting stubby trunk with pair of strap-like leaves can live for centuries, gradually expanding by growing from the region where the leaves are attached.

There is an extensive mythology surrounding the cultivation of Welwitschia, but the plants aren’t as difficult as one might be led to believe. They don’t actually need to be grown in tall, skinny drainpipes, and may in fact benefit from planting in a wide container (or in a ground bed in a greenhouse), which allows room for an extensive network of surface roots to develop. It is possible to transplant them, though Welwitschia roots are a bit on the delicate side. They can also grow fairly quickly: the large mature plants at the University of Connecticut in the photos are only about 12 years old. For the past several summers, these plants have produced cones.

plants are either male or female (i.e., they are dioecious). So far here at UConn, we only have had fully formed cones on male plants like the one in the photo above, but the production of seed should be possible, eventually, as more of our plants reach maturity.

Certain aspects of the reproductive biology of Welwitschia and its relatives in the plant order Gnetales are similar to reproduction in flowering plants, and for a time Welwitschia and the flowering plants were considered to be fairly closely related. More recent information on the evolutionary biology of the vegetable kingdom has pretty well sunk this idea, though, placing Welwitschia and friends much closer to pines and other conifers. Likely fossil relatives of Welwitschia, with similar leaves and reproductive structures, are known from North and South America. Some of the fossil species were apparently tree-like, with branches.

Monday, August 24, 2009

Organic Pest Control, the Mad Botany Way

So, there was an outbreak of fruit flies in the kitchen last week. The place looked like an introductory genetics lab in May, when the students start to get lazy about disposing of their old Drosophila cultures. After more prosaic control options--such as cleaning out the compost bucket--were exhausted, I starting thinking about the possibilities for mopping up the abundant fruit fly stragglers. If only I had something sticky like flypaper, with a sweet smell to draw the insect pests to their doom...

Then I remembered that I have access to Drosphyllum lusitanicum, the Portuguese Sundew or Dewy Pine, a large carnivorous plant from the western Mediterranean with leaves that drip with mucilaginous goo and smell strongly of honey.

Drosophyllum turns out to be brutally efficient at offing Drosophila. The first flies were caught before I even set the plant down by the sink, and within an hour it looked like the majority of the infestation was glued to the leaves and in the process of being digested. I brought the Drosophyllum back to its greenhouse lair after a couple of days: it's not the sort of plant that would survive in typical kitchen conditions for long. Besides, there wasn't anything left for it to eat.

For those tempted to try growing their own Drosophyllum, there are cultural notes at the ICPS website.