Erect Dayflower and its sensitive pals

25 Jul

Commelina erecta


Yesterday John and George said phooey to 90 degrees and hoofed across the burning sands to warm up even more at a literally burning prescribed fire to examine the effect of heat stress on foliage (relevant to my plant physiology class), and to wonder how red widow spiders repopulate after fire.  (The red widow is one of John’s “pet” projects.)   It was hotter, spideryer, and smokier than Jerry Falwell’s preview for sinners.

I’ll bet Hell doesn’t have the super-cool blue blossoms of erect dayflower, so refreshing like a sky blue popsicle on a blazing July day.

Commelina erecta yesterday. Note the abortive 3rd petal, and that half the stamens are pollen-making (brown) while the others are pollenless and bright yellow.

Commelina erecta yesterday. Note the abortive 3rd petal, and that half the stamens are pollen-making while the others are pollenless and bright yellow. (By John Bradford)

The Spiderwort Family, Commelinaceae (com-ah-lynn-ACE-ee-ee), combines the world’s most ephermal flowers with the world’s toughest foliage. Everybody encounters Commelinaceae.   Gardeners know, for example, oyster plant (Tradescantia spathacea), basket plant (Callisia fragrans), and small leaf spiderwort (Tradescantia fluminensis).   Persons concerned with invasive exotics know, for example, oyster plant (Tradescantia spathacea), basket plant (Callisia fragrans), and small leaf spiderwort (Tradescantia fluminensis).

Commelina diffusa, superweed

Commelina diffusa, superweed

Neglectful yard owners are intimate with spreading dayflower (Commelina diffusa), a worldwide weed with an impressive claim to fame, having evolved herbicide resistance in the 1950s before resistance was cool.

Oyster plant

Oyster plant

Commelina brings us to yesterday’s item of beauty: erect dayflower.   How many true blue wildflowers are there?   Commelina demonstrates in multiple ways how things don’t always amount to their original potential, beginning with the genus name itself.   The genus is named for a Dutch family of the late 1600s and early 1700s, Jan and Caspar Commelin were prominent botanists, but Caspar’s son died young.   Most Commelina species have two large petals representing Jan and Caspar. The third petal is usually abortive, standing for the son’s premature death.

The third petal is not the only abortive organ. Although you’ll never notice it, Commelinas fundamentally have two inflorescences per stem, but one often fails to mature, it is “vestigial,” that is, left over and no longer amounting to anything, like my appendix and canine teeth.

To keep going with lost functions, Commelina has six stamens but only two make pollen.   The others quit making pollen, and became bright yellow flags attractive to pollinators.  Among these, one is larger than the others and even seems (?) maybe to make a little pollen.

Growing among the erect dayflowers yesterday was another species with its own odd vestigial parts. Cacti evolved from “normal” leafy plants. They still carry genes for making leaves. The leaf-making genes are usually suppressed.   But not 100%. As prickly pear stems first emerge, they have cute little leaves on them, soon to fall off leaving behind the familiar prickly pads.

Prickly pear with leaves

Prickly pear with leaves (by JB)

Now back to Commelina.   This week my biology teacher wife Donna shared with me an internet report (there exist several) showing purportedly mutated flowers from the Fukushima nuclear disaster. (Yes, we all know there could be other explanations, so please no condescending e-mails pointing out alternative possibilities.)

Roseling (Callisia ornata) showing htsoe delicate Commelinaceae radiation-sensitive hairs (by John Bradford)

Roseling (Callisia ornata) showing delicate Commelinaceae radiation-sensitive hairs (by John Bradford)

How does this tie to Commelina?   The name “dayflower” comes from the ability of the flowers in Commelinaceae to turn to mush at the end of the day interpretably as an adaptation to recover nutrients if pollination fails. Perhaps the most delicate part of Commelina and other Commelinaceae flowers is a tuft of ultra-fine hairs on the stamens.   The hairs are so fragile they mutate especially readily, sometimes visibly to the naked eye, with low radiation exposure.   The mutating hairs helped monitor radiation following the Chernobyl and Fukushima disasters.   I wonder if a few dayflowers in the gardens around town near a power plant work as a cheap early warning  system.  Or maybe try a Geiger-tree.



Posted by on July 25, 2015 in Uncategorized



8 responses to “Erect Dayflower and its sensitive pals

  1. FelicityRask

    July 25, 2015 at 4:34 pm

    Good to know you are not a vampire. But don’t you eat apples? Supposed to keep the doctor away …
    Yes, I am concerned about native exotics … It has not escaped notice that it is not a subject you like to touch. Probably too wise.

    Felicity Rask, in equally hot VA – Blue crabs are fat and delicious.

  2. George Rogers

    July 25, 2015 at 5:42 pm

    Felicity, I write about invasives if I think there is something biologically, aesthetically, or historically interesting to look into. As far as documenting their presence and spread goes, there are terrific web sites dedicated to keeping up with that. And as I passed age 60 I think I learned there’s not much sense ranting (much) about things you can’t control. Those crabs do sound tasty, but tonight dinner is leftovers from the back of the fridge.

  3. Laure Hristov

    July 25, 2015 at 5:53 pm

    Wow, how pretty. Where was this? Thanks for all you do in the name of Botany! Don’t know how you do it in this weather!

  4. George Rogers

    July 25, 2015 at 6:42 pm

    Hi Laure…Seabranch SP just S of Stuart. We do it by quitting early. Played GeoGuesser today and the place was in Bulgaria. I missed it but my son got it right! Going to campus tonight for theater performance. Hope all is terrific with you.

  5. Chris Lockhart

    July 25, 2015 at 9:32 pm

    Thanks for highlighting this delightful group of plants. The spiderling, Tradescantia ohiensis is a nice understory cluster of blue! One thing I’ve always found intriguing about this Day Flower family is that, true to their name, they flower early in the day then are gone by midday. In addition, the flowers don’t wilt, they melt and liquefy!! I vaguely recall something about an enzyme that causes them to do this but can’t remember much more than that. Any ideas? The cool thing is that the liquefied petals may leave a blue stain on your leg as you brush against it, but it’s water soluble and easy to wash off.

    Cool stuff!

    • George Rogers

      July 25, 2015 at 10:41 pm

      Right—an interpretation of the liquefying flower is that it self-destructs and is resorbed for recycling of the pigments…plausible…but I’ve not searched to see if anyone has actually demonstrated the physiology. I mean, pulling the pigments or their constituents back would be quite an anatomical-physiological-hormonal-enzymatic-internal transport feat for the delicate xylem and phloem in those ephemeral tissues. Xylem does not bring water back downstream (with rare exceptions), and phloem loading is complex. Vascular tissue doesn’t resorb things rapidly to my knowledge. How exactly does that “ink” re-enter the inflorescence stalk and get re-processed? A simple alternative hypothesis could be that the flower merely makes cheap throwaway blossoms with very high water content. I do not know if it is relevant, but a cut dayflower stem exudes watery sap with a “good bit” of pressure. I have a photo of that in my plant physiology class materials.

  6. Steve

    July 27, 2015 at 8:01 am

    Perhaps if you surround your house with leadplant or leadtree, you can thwart the radiation’s deadly effects? 🙂 Love the puns, Piers Anthony would be proud.Great fun, and great article.

  7. George Rogers

    July 27, 2015 at 8:33 am

    Most excellent idea Steve. That’s a total hoot! …I’m on it!


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