Thursday, September 30, 2010

Those crazy gentians

A cluster of odd saclike flowers bristles from the summit of a robust Yellowish Gentian, Gentiana alba. A few weekends back, while plumbing the depths of Adams County in southernmost Ohio for rare flora, the inimitable Daniel Boone showed us this station of gentians. Yellowish Gentian is quite the rarity here - listed as an Ohio threatened species - and I'd seen it only a few times prior.

I'd concede that Yellowish Gentian is rather bland in coloration, but that's no reason to refer to it as the "Plain Gentian", as the USDA Plant Database does. Any deficiency of bright hues is more than compensated for by the outrageous floral structure. I mean, this is it - the flowers don't open. They are like little paper bags, and this strange morphology serves them well in weeding out unwanted pollinators, as we shall see.

Sometimes Yellowish Gentian flowers do open a bit, and I helped tease this one apart a bit so we could cast a look inside into the pollinary chamber. We can now clearly see the bowling pin-like carpels capped with their stigmas - the pollen receptacles. Off to the sides of the carpels and not really visible are the stamens and anthers, which contain the pollen.

If you are this flower, the whole idea is to get someone to bring you new pollen - pollen from another plant. Those lime-green stripes on the interior of the petals - petals are known as plaits in gentian-speak - help to lure in the pollen-delivering insect version of the UPS man.

This is another fall-blooming gentian, and it's looking good right now. Bottle Gentian, Gentiana andrewsii, is considerably brighter than the aforementioned species, and has a higher WOW factor. The blue stripes, or nectar guides, are much bolder on this species, but again, they are on the INTERIOR of the flower.

Bottle Gentian is a truly gorgeous species, and I can't imagine anyone not fawning over it for at least a few seconds if they were lucky enough to happen into some. The flowers in this photo are perfectly mature. Note how the flower's summit is tightly closed, and the blue nectar guides so clearly visible on the dissected flower can't really even be discerned, by our eyes at least.

But we don't have the eye-power of a bumblebee.
Bottle-type gentians have evolved an intimate relationship with large, fuzzy bumblebees of the genus Bombus, and these insects have vision that transcends ours in some respects. The bumbles undoubtedly see through the flower, a la Superman X-ray vision, and those showy-looking blue stripes jump out to them. And once a bumble has spotted those lovely azure strips, it must have them, at all costs!

The photo above and the next two were taken by my friend Ethan Kistler, and show the process of a bumblebee invading a Closed Gentian, Gentiana clausa. In the first shot, the bee desperately seeks a path of entry into the flower, and quickly realizes that it must push itself into the tiny gap at the flower's summit. These are brutish, powerful insects, and that's what it takes to penetrate the gentian's defenses.

A bit of prying and prodding, and it's in. This is an outstanding example of a botanical lure - an immobile piece of vegetation that is able to successfully pull in an animal, and make it complete the plant's reproductive cycle.

One just couldn't design a more effective pollinator system than has this gentian. The bumblebee is now completely inside the flower, and what we've got here is the equivalent of a fuzzy pipecleaner tightly shoved into a tube and being twisted about. Not only is the bee thoroughly dousing the stigmas with pollen it has brought over from the last gentian visited, thus cross-pollinating this plant, its fuzzy body is also getting totally dusted with fresh pollen to take to yet another gentian.

Just another of the scores of fascinating plant-insect relationships.


John said...

A question: You mention that the last photos are of G. clausa but have the files labeled G. andrewsii. Did you mislabel or mistype?

Jim McCormac said...

Mislabeled, apparently.

Keith said...

Reminds me of Turtlehead flowers and bee pushing to get into them

Abraham Lincoln said...

I like the photography.

A.L. Gibson said...

You beat me to it, Jim! I found a small patch of the G. alba blooming a few weeks back on the Edge of Appalachia preserve and just yesterday discovered a large colony of G. andrewsii in full bloom along my road. Working for the EOA preserve this summer and following your blog has inspired me to take my nature photography and start a blog of my own. These two species of Gentians were to be my first post haha. As always excellent info, always enjoy reading your posts!

Andrew Gibson

Buford Nature said...

Thanks for the mutualism explanation. Darwin would be (was?) pleased.