Tuesday, September 30, 2008

Bottled Gentian

Last Friday, prior to the Lake Erie Raptor Symposium described in the preceding post, I had a bit of time to nip into one of Ohio's most spectacular ecosystems, the Oak Openings. I never miss an opportunity to explore this region, and am never disappointed when I do. This whirlwind trip netted many interesting observations, not the least of which were some fine specimens of one of my favorite plants.

Bottled Gentian, Gentiana andrewsii, are outrageous in appearance. They are an indescribably rich cobalt blue, with a flower shape totally out of sorts with nearly all other of our plants. The appearance of these gentians, and most other gentians for that matter, indicate the imminent frost of fall. They are among our latest plants to bloom, not long before short days and cool nights put an end to another season's floral display.

The prairies of the Oak Openings look particularly showy in autumn, when a riot of fall-blooming asters and other late-comers paint the landscape. One must generally get out of the car to find Bottled Gentians. They lurk in damp swales, overshadowed by more robust vegetation.

The search effort will be well worthwhile if you strike pay dirt. Nestled amongst overshadowing plants are the odd blue grocery sack-like flowers of the bottled gentian. They can be surprisingly common, but typically are rather local and always noteworthy to stumble upon.

A closer view of the flower, in order that we might better learn how it works. The flower sits in a green cup known as the calyx, and it is crested with five lobes, seen clearly in this shot. The shape of these lobes aid in identification of the species. As those of us who have made a study of this sort of thing know, identification is not as straightforward as the Peterson or Newcomb's wildflower guides sometimes make it out to be. There are three species of bottled gentian in Ohio, with two possible in the Oak Openings. One is a mega-rarity, Soapwort Gentian, Gentiana saponaria. Among other techincal differences, it has linear, or much narrower, calyx lobes than does this species, A. andrewsii.

Dissection of a gentian flower reveals some very interested features. The flower is five-parted but the parts are joined together by folds of tissue known as plaits, thus creating the saclike structure of the flower. Bumblebees - those big fuzzy ones in the genus Bombus - are primary pollinators, and they force their way in via the tip of the flower, which has an opening but is virtually sealed up. I have seen them enter gentian flowers. They fly to the flower, and begin forcefully pushing at the tip, forcing their head into the flower, and eventually, their entire body. Then you basically have a bee in a bag. It bumbles about inside, thoroughly pollinating the stigma, probably with pollen from another plant.

How does the bee know to enter, or what entices it within? Opening the flower as above may reveal an answer. Bees see color spectra not visible to us, and it is possible that to them the bright blue stripes clearly visible above - on the inside of the flower - are obvious from the outside. These stripes clearly seem to be nectar guides, which are a flower's landing lights to guide in pollinators.

Here's the business end of the gentian flower - the parts that make new gentians. the thicker bowling pin-shaped column is the carpel, or pistil - the female parts. At the base is the ovary, which contains ovules within. Each ovule will become a seed. The little two-pronged unit at the top of the carpel is the stigma, which is the part that receives pollen during pollination.

The two slender appendages to the left are stamens - the male parts. The stalks are called filaments, and are capped by mushroom-shaped units called anthers. The latter contain the pollen, which must eventually get to the stigma, and preferably the stigma of another plant to ensure cross-pollination. This is where, in the case of the bottled gentian, those large fuzzy bumblebees come into play.

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