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Category Archives: Agalinis

False-Foxgloves and the Angle of the Dangle (revisited)

05 Sep

Agalinis linifolia and close kin

(Agalinis translates roughly as “much flax” because the foliage resembles flax, having linear (linifolia) leaves.)

Orobanchaceae, a family of parasitic plants

In the places where the mud is ankle deep lives a pretty wildflower, or should I say a few, as there are about 17 lookalike Agalinis species in Florida, perhaps three in our immediate area.  They are tall, thin, delicate and attractive, not to mention partly parasitic, swiping nutrients from neighbor’s roots.

Agalinis by John Bradford

The flowers have a weird life history, possibly not 100% true, yet documented for Agalanis species in other regions and seemingly applicable locally.  Each flower lasts only a day or less,  so hurry…get pollinated!  

  

by JB

The blossoms open early in the morning, releasing pollen before the pollen-receiving stigma is ready to go.  Any bee who happens along picks up that fresh pollen and takes it to a different flower ready to receive.  This delay holds the door open to cross-pollination as opposed to self-pollination, the ultimate form of inbreeding. Spoiler:  Selfing may follow.

The long light violet dohicky is the style, the stigma at its tip. The pollen-filled anthers are horizontal at the top of the entrance.

As the day progresses the originally short style grows and grows while its stigma tip becomes pollen-receptive.  The style attains a ridiculous length, bending down across the entrance to the flower so that an incoming bee must push under its stigma-tip and dust it with pollen to access the interior.

No bees today?  No problem…then comes backup:  The style ultimately grows into the shape of a J curling up under the pollen-releasing anther.  With luck gravity may drop pollen from the anther onto stigma tip curled under it.

Corolla dragging pollination.

Last chance to pollinate.

But a pollen sprinkle is iffy, and the flower has an even better finale.  Late in the day the petal tube and attached pollen-shedding anthers begin to drop free.    The hooked style is attached to the plant, not to the tube.    As the funnel-shaped tubes begins to  fall, its inner anthers slide past the hook, maybe even snag on it.  The passing stigma scrapes pollen from the anthers and/or mops pollen out of the narrow end of the funnel.   Wind motion may help the scouring process. Another name for the petal tube is the corolla, and this type of last-ditch self-pollination is called “corolla dragging.”    On other species of Agalinis dangling in the wind can last an hour.

It worked. Fruits.

 
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Posted by on September 5, 2020 in Agalinis, Uncategorized

 

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False-Foxglove, Pretty tho a Little Sneaky

27 Oct

Agalinis linifolia and related species (about 11 species in Florida)

(Agalinis comes from Greek for “resembling flax,” linifolia refers to the linear leaves.)

Orobanchaceae (traditionally Scrophulariaceae)

Heavenly weather today, at long last, so I helped John with his megacool photo guide to local natural areas.  An opportunity to visit Jonathan Dickinson State Park near Hobe Sound, Florida that was.

JD Park

Jonathan Dickinson State Park.

Plenty in flower now, with the fairest of them all being False-Foxgloves with polka-dotted,  yellow-streaked, ticklefuzz-enhanced, purplish blossoms all through a meadow.  What red-blooded bee could resist?

Agalinis looking in

The white rod sticking out is the style and stigma, responsible for incoming pollen.  Behind it you can see 3 (4th one hidden) downturned points. Those are the stamens in two pairs.

The inner flower structure reveals a feature known as didynamous (dye-DYE-neh-mus) stamens, which is a botanical way of saying four stamens in two pairs of different lengths, the members of each pair clinging edge to edge.   Stamens are the pollen-making organs.   The two different-length stamen pairs apparently cater to different types and sizes of bees, and if you look closely the longer pair  is a little different from the shorter pair.    Having the two members of a pair linked side to side demonstrably improves pollen delivery.

agalinis stamens

Flower with petals removed. The long hairless white bar on top is the style.  The two shorter hairy units are the stamen pairs stuck together edge to edge, and of two different lengths and different orientations.

You can’t dig up the prettiest wild flowers in a State Park, so take the next part on faith.   These plants are hidden root parasites on neighboring plants.   The parasitic  root tips grab  victim roots and suck their vital juices just as a tick steals mine.

Gotcha! Agalinis root attacks its prey.    Photo by William Vance Baird.

Now all this begs the question of how the little sucker finds a root to attack, answered in part by recent plant hormone research.  The number of known plant hormones is expanding, and each new hormone has complex roles linked to other hormones.

A hormone family just discovered in the 21st Century is called strigolactones, part of a hormonal-genetic control system with remarkable duties.   This system detects smoke, switching on genes to kickstart seed germination upon passage of a fire.  (This suggests some low-tech experiments, although inconveniently complex variables may strike.)

Continuing the topic of underground detection, how does a plant root beckon beneficial soil fungi, “here I am ready to hook up” in a symbiotic relationship?    Answer:  Roots secrete strigolactone hormones into the dirt to entice fungal partners.    And, yep you guessed it, as biologist Caitlin Conn and collaborators documented in 2015, parasitic interlopers such as Agalinis intercept those hormonal solicitations, exploiting them to find the neighbor who was expecting a friendly fungus, not a sap-sucking parasite.

Agalinis linifolia 1

Agalinis linifolia by John Bradford.

Agalinis clump

 
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Posted by on October 27, 2017 in Agalinis, False Foxglove, Uncategorized