Nectar production is anything but a cheap strategy. Indeed, you bet on a real increase of fitness (pollinators tend to remember those flowers that are rewarding most, that’s their business after all -and yours is ending up with more seeds). But on the other hand, the so precious potion may finish in bad hands legs: those of hexapodic visitors that will take the offer away (pollen, nectar) without contributing to pollination of any kind your kind*. Then the efforts of putting much into sugars or complex attractive addictive chemistry will be gone with the wind insect. A total waste instead of the increased pollen import/export that was hoped for (unless you don’t care at all about huge nectar loss but wish to protect yourself against the sun)…
Indeed, with nectar at pollinators’ disposal, plants face a non negligible risk of larceny. Nectar is a great resource to opportunistic wanderers, and because it is so costly to produce and maintain available to pollinators, one should expect tricky solutions to simple but unavoidable issues such as theft.
We already discussed a strange case where the plant ended up domesticating a nectar robber and turned it into its main pollinating agent. Today, we get another example, this time building on simpler ways of dealing with thieves: our plant found a quite basic solution [1]!
The cuty plant that retains my attention is the Purple Toothwort. Previously ascribed to the Scrophulariaceae family because of the floral structure, it has now moved into the Orobanchaceae (along with many other species). Orobanchaceae contains many parasitic plants, and Lathraea clandestina, our case today, completely lacks chlorophyll and is a fully accomplished parasite. It grows on roots of trees, and a few species can serve as hosts.
Compared to its sister Lathraea species, the Purple Toothwort also lacks any stalk, and its flowers are therefore completely grouped together. As a result, flowers barely sit above the ground, in a calling purple tuft that would rise the eyes of any organism with a decent visual system (you or birds), in addition to sweet scents of sugar (ants may not see them, but they smell it too easily). And that’s two good reasons to find a way to avoid being forayed by creepy thirsty things, especially when you grow at places where you really need to attract pollinators, that is, furnish them with a big reward (what would otherwise be a good reason to lurk in underwoods filled with dry leaves or decaying matters?)…
As usual when facing troubling threats, evolution provides you with ready-to-use tricks depending on what you have/who you are. Amino acids are classical components of nectar (note that we could generalise this to many secretions -venoms do as well!). Degrading them is no big deal, cells are already furnished with all necessary enzymes to deal with them one way or the other (building up or degrading these chems). So Purple Toothwort eventually found a straightforward answer to the issue of larceny: the nectar seems also provided with enzymes deaminating two common amino acids in the nectar, namely glutamate and serine. Ammonia is then released in the nectar where it behaves as a base and rises pH to around 10 (sometimes even eleven). An efficient deterent to almost any opportunistic thieves. In addition, this makes the nectar unpalatable to beasties with elaborate taste such as you or birds. Good deal!
Of course, the very basic solution only works if your favourite pollinator doesn’t care about alcaline nectar, or obviously because it has not evolved the ability to experience the very bad taste of ammonia. So are bumblebees, and that’s why Purple Toothworts have gone this way…
* Nope, Seeds Aside didn’t turn into creationist rhetorics, don’t worry!
[1]- O. E. Prys-Jones & P. G. Willmer (1992).The biology of alkaline nectar in the purple toothwort (Lathraea clandestina): ground level defences. Biological Journal of the Linnean Society 45(4): 373 – 388.
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[…] September marks a return to blogging by Laurent Penet, the founder of Berry Go Round. A fascinating post of nectar production in the Purple Toothwort (Lathraea clandestina) illustrates not only the general ideas behind nectar […]
[…] is finally blogging again – I adore his silly botany posts. Here’s a great one about how purple toothwort protects its nectar. Tags: animal rights, arizona, baucus, botany, […]