Tag Archives: lobelia

White Lobelia and Plunger Pollination

08 May

Lobelia paludosa

(M. de L’Obel was a Flemish herbalist. Paludosa means swampy.)

Campanulaceae (Lobeliaceae)

Oh so pretty,  White Lobelia is wetland wildflower worth soggy sneakers.   Those curvaceously symmetrical white flowers look like the work of a marble sculptor…or maybe a plumber, read on.   This is one of many Florida lobelias, mostly north of our region.  Lobelia overall has 400 species almost worldwide.  Gardeners love lobelias as commercial ornamentals.  Native plant enthusiasts know them as diversely colored wildflowers, especially in wet habitats.  Smokers may know them too:  Lobelia inflata, Indian Tobacco,  and some additional Lobelia species (as well as some non-lobelias) give forth the alkaloid lobeline used to wean smokers off of nicotine and for other historical medicinal “benefits.”  (Warning…alkaloids are dangerous.  Do not eat, smoke, or otherwise ingest the wildflowers. Lobeline has morbid toxic effects, including potentially death.)

See the slit?  The black unit is the tip of the stamen tube.

You can always recognize a Lobelia by a slit running the length of the flower tube.   More on that in a moment.

Lobelias have a crafty means of pollination that protects pollen from the elements and from pollen thieves, dispensing it gingerly onto the floral visitor only as needed.   To understand the pollen dispenser we must understand the flower.

It is bilaterally symmetrical with a tube made of petals.   The top of the petal tube has that weird slit you already know about.  On either side of the slit the top petals are curled back seemingly to guide the visitor to the business parts of the flower near the slit.  Now for the business parts:

The stamens are joined edge to edge to form a hollow stamen tube inside the petal tube.   The stamen tube bends upward and can rise forth through the slit.  The outer tip of the stamen tube is made of five anthers likewise joined edge to edge, releasing their pollen to the inside of the stamen tube.

You with me?  The anthers form a tube with loose pollen inside toward the outer end.

Slit and tube poking up through it. This flower is in the post-plunger female phase.  The stigma has popped to the left out of the end of the stamen tube. No more dispensing pollen…now it time to receive some from a different flower.

Now comes the female component…the style rises through the stamen tube with a broad stigma at its tip.  The rising stigma acts like a plunger pushing pollen out the end of the stamen tube.

The anther tube (right) sliced open and the style and stigma bent up for visibility (left).

Tip of the stamen tube isolated. A little bit of yellow pollen visible to the left.

At this point the stigma is not receptive to pollination.  That comes later after it has pushed all the way out of the stamen tube.   Back up a moment and consider the stigma in its plunger phase still inside the anther tube:

A bee comes along and probes the flower for nectar.  The tip of the stamen tube dispenses a dose of pollen onto the bee, like toothpaste dispensed out from the tip of its tube onto a toothbrush.  (See the diagram above.) Although I can’t prove it, it seems the bee pushing on the tip of the stamen tube and also maybe on the tube more basally helps squeeze the pollen out by narrowing the tube and/or by forcing the tube to shorten a little while the style-stigma plunger inside stays firm.  Think of wearing a loose long sleeve shirt with the cuff exactly at your wrist.  If you push on the shirtsleeve it will kink, fold, or narrow a bit so a bit of your wrist becomes exposed.   This can be simulated with the tip of your finger posing as a pushy bee.   Pollen release “on demand.”

John's and my blog this week

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Posted by George Rogers on May 8, 2020 in Lobelia paludosa, Uncategorized

 

Tags: lobelia, Lobelia paludisa, plunger pollination, White Lobelia

Glade Lobelia

06 Apr

Glade Lobelia

Lobelia glandulosa

Campanulaceae (Lobeliaceae)

 

Lobelia feayana (by John Bradford)

 

Yesterday John and George trekked under the hot sun down a dirt road in the large wetland area west of Jupiter, a zone of marshes, depression ponds, and wet pine woods.  There’s a special treat there—a flowing gurgling glimmering brook with clear water and tiny fish, lined with all your basic wetland plant species.  A natural garden of delight.  (The horseflies too were delighted to have some fresh meat. Come along.)

And no garden is completely delightful without a Lobelia, as lobelias are among the most widespread, diverse, colorful wildflowers and cultivated horticultural selections around the garden globe, over 350 species.  Today’s Glade Lobelia is a pretty blue wildflower reminiscent at a glance of last week’s Scutellaria.  And just as Scutellaria had a gimmick, the scute, lobelias have their own odd flower feature.

Lobelia glandulosa (by JB)

In lobelias, there are two linked oddities:  the flower tube is slit for most of its length, and the five stamens are fused into a tube encasing the style and stigma.   As the flower opens the stigmas are  hidden within the anther tube, making the flower effectively male (pollen producing) at first, then later the stigmas emerge past the end of the tube to render the flower female.    (These features are notably similar to similar structure in the Aster Family.)

This link shows the anther tube removed from a flower.  The style and stigmas are inside the tube  CLICK

Lobelias have hummingbirds, butterflies, and who knows what else, as pollinators, mostly bees no doubt.  In most other flowers the pollinator has to fit within the petal tube, like a car entering the garage.    But in Lobelia, the visitor pulls open the split petal  tube to gain access to inner flower, contacting the anthers or stigmas through the slit.   This link shows a hummingbird probing the slit flower while having its head tapped by the anther-stigma unit.  CLICK

As a student, I remember being wowed at a more northern species, Lobelia inflata, sometimes called Indian Tobacco.  (A dumb name since true tobacco itself was a Native American bad habit.)  The professor said, accurately, that people smoked this species and used it in medicines for the several alkaloid drugs it contains, most interestingly for smoking-cessation and for curbing other addictions.   That was in the 70s, and research has marched on. It turns out the dominant alkaloid, lobeline, interacts with more or less the same brain receptors as nicotine, although they are not similar chemically.  There’s perhaps something potentially useful going on there, and lobeline interferes with the neurotransmitter dopamine.

One of these days I’ve got to quit smoking!

John's and my blog this week

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Posted by George Rogers on April 6, 2014 in Glade Lobelia

 

Tags: dopamine, lobelia, tobacco

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