BPotD Work-Learn student Tamara Bonnemaison writes:
I have been ogling the photos that Sandy Steinman (aka Sandy Steinman@Flickr) has recently posted to the Botany Photo of the Day Flickr Pool. I was sure that one of my predecessors would have already featured Datura wrightii, and was pleased to see that I am the first to write about this fascinating species on BPotD. Thank you Sandy, for this photo, and for all of the images that are making me yearn to hike in Joshua Tree National Park. Keep them coming!
Datura wrightii, also known as sacred datura or jimsonweed, is a representative of a group of plants that mean many things to many different people. Fans of Carlos Castaneda will know of this genus from Castaneda's hallucinatory accounts of his journey through the teachings of shamanism. Ethnobotanists will know of the traditional uses of Datura spp.--that a number of species were used by people of every continent (except Antarctica) to perform religious rituals, poison enemies, and treat the ill. Gardeners will know Datura wrightii as a deer-resistant species with exceptionally large and sweet-smelling white trumpet flowers that bloom at night. ER doctors who have had to treat overdosing experimenters will be familiar with the toxic effects of this genus. Sandy's photo beautifully captures the spiritual, aesthetic, and even dangerous characteristics of this species.
Another group that has investigated Datura, and specifically Datura wrightii, are entomologists and insect ecologists. One particular area of interest for this group is the way that Datura wrightii's trichome dimorphism affects insect herbivory. Some jimsonweed plants feel velvety, because they have short, non-glandular trichomes (which are fine outgrowths or appendages on the plant, in this case hairs). Others feel sticky, as they have glandular trichomes that secrete acyl sugars, thus providing resistance to herbivorous insects. In a 2005 article published in Ecology, Daniel Hare and James Smith compared herbivory and seed production of Datura wrightii plants expressing either the "sticky trichomes" or the "velvety trichomes" trait. Hare and Smith conclude that producing glandular trichomes reduces seed production in the plant's first year, and that the herbivory resistance conferred by the glandular secretions never fully compensates for this initial setback. Although the glandular trichome gene is dominant, under the study conditions examined by Hare and Smith, it did not confer an overall evolutionary advantage.
One of the most studied aspects of Datura wrightii is this species' relationship to the hawk moth (Manduca sexta). Adult hawk moths pollinate datura flowers, but also lay their eggs on the plants. The hatched larvae then consume datura leaves. This mutualistic yet also antagonistic relationship has interested many an entomologist (for more details, consult Bronstein et al's 2009 article, Reproductive biology of Datura wrightii: The Benefits of A Herbivorous Pollinator (PDF)). A particularly amusing facet of this relationship is that some people have noticed that hawk moths become intoxicated after wallowing in sacred datura pollen. Rather than quickly visiting one flower and moving onto the next, some hawk moths arrive before the flower opens, and once allowed inside, will submerse themselves deep inside the corolla, beating their wings frantically until completely covered in pollen. It appears that datura's alkaloids affect moths and humans alike. Learn more about these "jimsonweed junkies" via the nonist.