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Posted

While reading about Rhopaloblaste in one of my palm texts, I read that the prominent pulvinus is part of the genus description. 

Having zero botanical training I was not familiar with the word. 

From Wikipedia "A pulvinus (pl. pulvini) is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent (nyctinastic and thigmonastic) movement. Pulvini are common, for example, in members of the bean family Fabaceae (Leguminosae) and the prayer plant family Marantaceae."

I am familiar with prayer plants in Marantaceae for example that close up at night and the common weed called the sensitive plant that closes with a touch and others, but today headed to try to see and photograph the pulvini on my Rhopaloblaste elegans.

So below are many photos but I don't see anything unique looking. Can someone help please?

 

 

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Cindy Adair

Posted

For those who want to see the whole palm:

DSCN2005.thumb.jpg.31de49fe88f63c31919d178cd73ed651.jpg

Below is a nearby smaller one with a young Iriartea deltoid in the foreground.

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  • Like 1

Cindy Adair

Posted

Cindy, my understanding is that the pulvinus is at the base of of the petiole, on the top side, just above the leafbase.   (This location is not shown in your images.)  :)

San Francisco, California

Posted

https://palms.org/wp-content/uploads/2016/05/v14n3p75-92.pdf

 

The link above is to a 1970 article in the IPS journal on Rhopaloblaste that mentions the pulvinus.

  On 9/6/2021 at 9:11 PM, Darold Petty said:

Cindy, my understanding is that the pulvinus is at the base of of the petiole, on the top side, just above the leafbase.   (This location is not shown in your images.)  :)

Expand  

Thanks Darold! I guess I need to trek out there again.

I looked at the base of the petiole and at my glance it looked "ordinary" hence the leaflet photos.

The larger one is a bit hard to navigate to as it's on a slope and crowded with other palms, no surprise.  However the smaller one is not as far and in the shade!

Cindy Adair

Posted

With Darold's clarification and a revisit I MIGHT see the pulvini.

Could they be the little pair of triangles in each photo below?

If so, this could actually be useful for identification especially with lost labels.  I don't see anything like this on a nearby Euterpe in the sun that I did not photograph.

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I also see that the leaves are somewhat movable from the stem like a hinge, especially compared with a nearby Iriartea shown below.

DSCN2021.thumb.jpg.310540aa787513cb21b8c48be729d3c8.jpg

 

Cindy Adair

Posted

Cindy, those triangles are 'auricles' or 'ligules', not pulvini.  I have an old book with text that discusses this at length.  I will try to post this text later today. 

Cliff notes version,.... pulvini are seldom visible to the naked eyesight.   :)

San Francisco, California

Posted

I guess that would have been too easy! My hopes are dashed. 
 

Thanks for the information!

Cindy Adair

Posted

Here are selected paragraphs from   "The Natural History of Palms" by E.J.H. Corner,  University of California Press, 1966. 

 These organs are seldom visible, but I believe that I can observe them at the base of the leaflet where it attaches to the rachis on Howea forsteriana, wil try a photo later. 

pulvinus.pdfFetching info...

San Francisco, California

Posted

HA!   I actually am familiar with the term  / part as well, and  usually you don't see much of them as they are rather inconspicuous. It's funny because I discovered this while researching the ways plants achieve movements.  I find that fascinating as I have several species that do this including some Venus flytraps, and calatheas.  The calathea lancifolia (rattlesnake plant) is one of the more dramatic movers in that it folds up almost into a column every day around 4-6 pm, exposing the purple undersides of its long narrow leaves.  

  Occasionally  in some plants they  make the very base of a petiole bulge a bit.   They are also found at the base of leaflets along a rachis  as in the case of the sensitive plants.    I've circled the pulvinus in the photos below.   

 

 

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  • Like 1
Posted

Thanks DCA palm fan and Darold for the additional information!

I wish I could see something without magnification on my Rhopaloblaste that I could photograph and touch plus understand why this genus might even have pulvini when as far as I know the leaves don’t move independently.
 

Or at least they don’t move when I am watching them....

They could close and open and even dance during the night while I sleep. A palm party perhaps?

Yes I do have a vivid imagination.
 

 

  • Like 1

Cindy Adair

Posted

Cindy,  the pulvini are the means by which all spears unfold to fronds.   :)

  • Like 1

San Francisco, California

Posted


Live and learn! Thanks again Darold.

So maybe nothing really unique to Rhopaloblaste?

08ED5EAE-EB82-4F77-ACCF-16718E772559.thumb.jpeg.ee73257486b4fa11ec2de5df9fbbe322.jpeg
 

The source is a new to me 1994 text:

C5CA51C5-6F49-4EC2-8D36-FADD243C7386.thumb.jpeg.69571540b6c32d0104891fc93096de8a.jpeg
 

That led me to find the referenced Principes article linked earlier.

I clearly need to go back to school and take some botany courses, huh?

Cindy Adair

Posted
  On 9/9/2021 at 9:26 PM, Darold Petty said:

Cindy,  the pulvini are the means by which all spears unfold to fronds.   :)

Expand  

 You know, I wondered about this.  That makes total sense though!  Fascinating! 

Posted

Here are two examples of pulvini on Howea forsteriana.

IMG_0408.JPG

IMG_0410.JPG

San Francisco, California

Posted

Wow Darold those photos make total sense.

That was exactly what I tried to find on my Rhopaloblaste! I don’t have any Howea but next one I see I will look for the pulvini.

Thank you so much!

Cindy Adair

Posted

They are more prominent on Howea than many other genera, especially fan palms.  :)

San Francisco, California

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