Today's entry is written by Bryant, Botany Photo of the Day work-study student:
I would like to thank David Midgley (aka Petrichor@Flickr) for supplying today's image of Puya berteroniana. Puya berteroniana is one of the larger members of the Bromeliaceae, and it is native to the north-central region of the Andes (where it is known by the local residents as chagual). From a dense rosette of long and narrow leaves, a flower spike can emerge and grow to around 3m in height. The thin leaves have fishhook-shaped spines that cover the leaf margins. These spines have been known to entangle sheep, in some cases causing the animal to become trapped and die from starvation. Likely this is a defense mechanism to prevent foraging of its flowers/fruits, but perhaps it is predatory by adding nutrients to the soil near to the plant (there is no research to suggest this is the case, but it would be an interesting experiment). The species is commonly found in colonies on north-facing slopes, at elevations of 500m to 2500+m. The colours of the waxy petals can range from a bright turquoise to the deep blue so excellently pictured by David.
When I came across this image I was blown away by the unusual colour combination of the petals and stamens, the peculiarity of the morphology and the fact that it is a bromeliad. However, I was completely stunned to learn that this species and possibly other members of this genus (e.g., Puya chilensis and Puya raimondii) have been hypothesized to undergo the process of self-immolation or spontaneous combustion; see this earlier BPotD entry on a Puya by Eric La Fountaine. It does not appear that this hypothesis has been proven. However, there are frequent accounts of the charred remains of (typically) mature plants being encountered, with no fire damage in the surrounding vegetation. The why isn't known either, though it is speculated that it may be an aid in germination. On the other hand, the largest member of the genus, Puya raimondii, is known to be burned by local peoples for warmth during the winter as there are few woody species that grow in the near-xeric conditions. There are also accounts of a tradition where locals light individuals/colonies of Puya sp. on fire for celebration and/or during the winter solstice. Another account describes local herders lighting fires around Puya berteroniana to burn off the spines on the leaves to provide forage for their livestock (primarily goats). Whether the cause of isolated fire in Puya berteroniana is anthropogenic in nature and/or the result of complex chemical reactions, Puya berteroniana and other members of its genus still pose several mysteries to the botanical world.