Ask a Question forum: For the DB: botany question regarding disc flowers vs. ray flowers

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Name: Michele Roth
N.E. Indiana - Zone 5b
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chelle
Aug 5, 2013 7:13 PM CST
Could this be considered a good example of disc flowers?

Thumb of 2013-08-06/chelle/3d086f

It's this plant:



Are the long outer and brightly colored parts (the ones that fall off first) considered both ray flowers and tepals, or is it different for each type of plant?



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Name: Rick R.
near Minneapolis, MN zone 4a
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Leftwood
Aug 5, 2013 9:22 PM CST
Yes, a good example of disk flowers (or disk florets).
But I wouldn't enter it as an example without showing the entire flower head (including ray flowers). This is already a difficult concept to grasp.

Ray flowers (or ray florets) are not botanically comparable to tepals, and so could never be substituted, one for another, even in different flowers.
---- "Tepal" is a term used to encompass both petals and sepals, when the flower does not have a strong differentiation between the calyx and the corolla.
---- The term "ray flower" designates a type of individual flower that would include all parts that might be present: sepals, petals, ovaries, stamens, etc. Tepals, if they were present, would only be part of the ray flower.

In the case of Tithonia, there are no tepals, because the colorful part that most people would call an individual petal is actually the corolla (not a single petal or sepal) of one ray flower. Thus, the photo above shows 13 ray flowers (and about 90 disk flowers).

Nature creates huge variations in parts of flowers (indeed all parts of a plant). For instance, depending on the plant, a sepal can look like a petal, a leaf, a bristle, a nub, a cone, or be absent entirely. Most plants in the world do not have ray flowers. So while there can be similarities within groups of plants, each will be different.
[Last edited by Leftwood - Aug 5, 2013 9:24 PM (+)]
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Name: Michele Roth
N.E. Indiana - Zone 5b
I'm always on my way out the door..
I was one of the first 300 contributors to the plant database! Forum moderator Garden Sages Garden Ideas: Master Level Dog Lover Cottage Gardener
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chelle
Aug 6, 2013 5:22 AM CST
Thanks, Rick. Thumbs up


My thought was to enter it if it might be useful for a future article on this type of subject. It's not that often that I get enough pictures of any one plant showing different stages of development that individual parts of a bloom can be showcased. Smiling
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Name: woofie
NE WA (Zone 5a)
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woofie
Aug 6, 2013 10:21 AM CST
Trying to wrap my brain around this whole concept. So, would a zinnia be considered a disk flower? AND a ray flower? Or is it a ray flower that includes disk flowers? Sigh, we really need that glossary feature....
Confidence is that feeling you have right before you do something really stupid.
Name: Jay
Nederland, Texas (Zone 9a)
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Horntoad
Aug 6, 2013 10:40 AM CST
Look at this photo.
The yellow cluster in the middle is made up of many tiny flowers, these are the disc flowers. The yellow "petals" around the outside, are each individual flowers, these are the ray flowers.
wildflowersoftexas.com
texasnatureonline.com


Name: woofie
NE WA (Zone 5a)
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woofie
Aug 6, 2013 10:49 AM CST
So, what differentiates a ray flower from a petal?
Confidence is that feeling you have right before you do something really stupid.
Name: Michele Roth
N.E. Indiana - Zone 5b
I'm always on my way out the door..
I was one of the first 300 contributors to the plant database! Forum moderator Garden Sages Garden Ideas: Master Level Dog Lover Cottage Gardener
Native Plants and Wildflowers Plant Identifier Organic Gardener Keeps Horses Hummingbirder Hosted a Not-A-Raffle-Raffle
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chelle
Aug 6, 2013 10:58 AM CST
So, what's still showing in this picture, Jay?

chelle said:

Thumb of 2013-08-06/chelle/3d086f






Are they florets above ovaries?

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Name: Evan
Pioneer Valley south, MA, USA (Zone 6a)
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eclayne
Aug 6, 2013 11:05 AM CST

Plants Admin

woofie said:So, what differentiates a ray flower from a petal?

Leftwood said:---- "Tepal" is a term used to encompass both petals and sepals, when the flower does not have a strong differentiation between the calyx and the corolla.
---- The term "ray flower" designates a type of individual flower that would include all parts that might be present: sepals, petals, ovaries, stamens, etc. Tepals, if they were present, would only be part of the ray flower.


Rick, combine your post with those photos and you have a great Idea/article. Thanks for clear description.
Evan
[Last edited by eclayne - Aug 6, 2013 11:08 AM (+)]
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Name: Michele Roth
N.E. Indiana - Zone 5b
I'm always on my way out the door..
I was one of the first 300 contributors to the plant database! Forum moderator Garden Sages Garden Ideas: Master Level Dog Lover Cottage Gardener
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chelle
Aug 6, 2013 11:20 AM CST
eclayne said:


Rick, combine your post with those photos and you have a great Idea/article. Thanks for clear description.



I agree and I'd be happy to add several additional pictures to the DB for use in it. Smiling

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Name: Rick R.
near Minneapolis, MN zone 4a
I was one of the first 300 contributors to the plant database! Garden Sages The WITWIT Badge Garden Photography Region: Minnesota Plant Identifier
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Leftwood
Aug 6, 2013 12:48 PM CST
chelle said:So, what's still showing in this picture, Jay?

Thumb of 2013-08-06/chelle/3d086f

Are they florets above ovaries?


These are the disk florets (or disk flowers). The ovaries are part of the disk florets, not separate.

So you see, what most people think of as "the flower" can be very confusing when picked apart and separated into botanical parts. The flower that most people think of has one (or one set of) each part (corolla, petals, calyx, sepal, ovary(s), stamens, etc.). But natural variations are practically infinite. With some species like tithonia and zinnia (mainly those in the Asteraceae family), "the flower" as a regular person would understand is actually many individual flowers, botanically speaking. In this case, the many individual flowers are ray flowers and disk flowers.

A botanist isn't interested in how a flower looks; rather, the importance is what actually makes a flower look like it does. Dividing a flower (and all parts of a plant) into individual parts and analyzing where these parts arise in the evolutionary process is the key to discerning the relationships between different plant species or between other groupings of plants. This is why it is so critical for the botanist to differentiate a petal from a corolla, for instance. All these clues are used to support their taxonomic categorization of species. This is how they know, for instance, that a Pointsettia (Euphorbia pulcherrima) is related to a Candelabra cactus (Euphorbia lactea). Who else would've thunk it?


woofie said: So, would a zinnia be considered a disk flower? AND a ray flower? Or is it a ray flower that includes disk flowers?.

So if I have explained sufficiently, the answer should be obvious: a zinnia flower as a regular person would understand, is actually compose of many separate flowers. Some of these flowers are ray flowers and some are disk flowers.
Name: woofie
NE WA (Zone 5a)
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woofie
Aug 6, 2013 12:58 PM CST
Yes, it's starting to make a bit of sense. Another website I looked at (here: http://www.backyardnature.net/fl_comps.htm) described zinnias as a Composite flower, that includes both disk flowers and ray flowers, among other things. But I'm still wondering how you differentiate between ray flowers and petals.
Confidence is that feeling you have right before you do something really stupid.
Name: Michele Roth
N.E. Indiana - Zone 5b
I'm always on my way out the door..
I was one of the first 300 contributors to the plant database! Forum moderator Garden Sages Garden Ideas: Master Level Dog Lover Cottage Gardener
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chelle
Aug 6, 2013 1:15 PM CST
Now I think I've got the gist of it!! Hurray!

Where typical gardeners or gazers study a plant's (composite) blooms more from the outside-in, botanists study more from the inside-out; separating individual parts by their function and by their contribution to the whole.

So, if I added the very first picture to the DB it might be confusing to readers because parts of the disk flowers are missing, is that right?


woofie said: ...But I'm still wondering how you differentiate between ray flowers and petals.


From what's been said previously, Woofie, I think that the part we see and refer to as a petal sometimes isn't a complete ray flower, either, but just a section of it.

Yes, no?
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Name: Ginger
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gingin
Aug 6, 2013 2:34 PM CST
please pass the advil Blinking Confused
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Name: Rick R.
near Minneapolis, MN zone 4a
I was one of the first 300 contributors to the plant database! Garden Sages The WITWIT Badge Garden Photography Region: Minnesota Plant Identifier
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Leftwood
Aug 6, 2013 2:52 PM CST
Yes, you have the gist of it chelle.
[Botanists] separating individual parts by their function and by their contribution to the whole.
I couldn't say it better myself.
chelle said:So, if I added the very first picture to the DB it might be confusing to readers because parts of the disk flowers are missing, is that right?

If by "parts of the disk flower are missing" you mean "parts of the flower head are missing", then yes, you understand.
The first pic shows the entire head of disk flowers; all parts of the disk flowers that should be there are there. But no ray flowers present. Without them, I am afraid readers will be looking for a flower that looks just like that, and not realize that ray flowers are part of the whole package. They would be very disappointed.

chelle said:From what's been said previously, Woofie, I think that the part we see and refer to as a petal sometimes isn't a complete ray flower, either, but just a section of it.

Except more often, "petals" in the vernacular sense are botanically "petals". Your inference is that all flowers have (complete or incomplete) ray flowers. Only a subset of the world's flowers have ray flowers at all. So more accurately, your statement should read:
The part we see and refer to as a petal sometimes is part of a ray flower, and is actually the corolla. But more often, what we refer to as a petal is part of a standard flower make-up, and not a ray flower.

* * * * * * * * * * * * * * * * * * * * * * * * * *

To distinguish between ray flowers and petals, you would need to dissect the flower head, and realize that a petal attaches differently and/or is accompanied by other plant parts that give you clues that it is one or the other. Not always an easy thing to do. Often, plant parts that you might expect to accompany are only vestigial or even absent, thus complicating things even more.

* * * * * * * * * * * * * * * * * * * * * * * * * *

Regarding the link you offer, woofie, overall very good. But it does irk me that the otherwise accurate site continually switches back and forth from "disk" to "disc". You will find that most real botanist stick to the standard "disk" rather than the newer form "disc". But younger folk nowadays, only ever see the word "disc" with computers, etc., and I expect that "disk" will become obsolete as the language evolves. Sigh....

edit to correct grammar error
[Last edited by Leftwood - Aug 6, 2013 6:11 PM (+)]
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Name: woofie
NE WA (Zone 5a)
Charter ATP Member Garden Procrastinator Greenhouse Dragonflies Plays in the sandbox I was one of the first 300 contributors to the plant database!
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woofie
Aug 6, 2013 3:02 PM CST
Apparently, even in the computer world, there is controversy over the spelling of "disc" versus "disk!" "Discs" are removable optical media (like CDs and DVDs), while "disks" are magnetic media (like hard drives and floppy disks). Picky, picky, picky..... Hilarious!
Confidence is that feeling you have right before you do something really stupid.
Name: Evan
Pioneer Valley south, MA, USA (Zone 6a)
Charter ATP Member Plant Database Moderator Forum moderator Aroids Irises Celebrating Gardening: 2015
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eclayne
Aug 6, 2013 3:24 PM CST

Plants Admin

What made your description clear for me Rick was that first photograph of chelles with the flower head and disc flowers, combined with the second photo of the bloom in it's entirety. Maybe pasting them, side by side, into a single image with the appropriate caption?
Evan
Name: Rick Corey
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RickCorey
Aug 6, 2013 4:39 PM CST
Hmm, is this a situation where the image-set-with-multiple-tags and pop-up-text would be a teaching aid?

I'm following this thread eagerly, not that I ever expect to meet someone whom I could interest or impress with such esoterica. But I wish I could meet someone like that!

(They would probably explain to me how I misunderstood your explanation, which seems very clear - just detailed and precise.)
Name: Michele Roth
N.E. Indiana - Zone 5b
I'm always on my way out the door..
I was one of the first 300 contributors to the plant database! Forum moderator Garden Sages Garden Ideas: Master Level Dog Lover Cottage Gardener
Native Plants and Wildflowers Plant Identifier Organic Gardener Keeps Horses Hummingbirder Hosted a Not-A-Raffle-Raffle
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chelle
Aug 6, 2013 5:26 PM CST
Thank you again, Rick! I know there's much more to learn, but it's wonderful to have the first couple of items cleared up so very well. Thumbs up

Y'all let me know if and how you'd like pictures for future use. I can set them in one frame if it helps. Smiling I think I have plenty that would work well enough.


Thumb of 2013-08-06/chelle/77797b Thumb of 2013-08-06/chelle/0f5d68

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