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Fernando Rivadavia

Drosera resin??

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Hello everyone,

I am hoping somebody can help me with a question: How do you define a substance as resinous? And do Drosera produce resins?

Drosera have sessile glands which at least in some species seem to produce a clear droplet of a susbtance that I hesitate to call resinous simply because I am not sure what determines a substance as a resin.

This substance does not evaporate completely and can be seen even on the petioles and undersides of the leaves in dried herborized specimens of some species like D.meristocaulis as hardened little beads. Here are some pics from the CP Photofinder where you can see these glands:

P1050532aa.jpg

meristocaulis01.jpg

Thanks for the help,

Fernando Rivadavia

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Hi Fernando,

there is a book on google books called "Plant resins: chemistry, evolution, ecology and ethnobotany" by Jean H. Langenheim.

It defines resins as terpenoids and phenolic compounds which are lipid soluble.

Mucilages are defined as polysaccharides which are water soluble.

The secretions of Drosera are therefore mucilages.

However the secretions of Roridula are not water soluble so are presumably resins.

LeeB.

Hello everyone,

I am hoping somebody can help me with a question: How do you define a substance as resinous? And do Drosera produce resins?

Drosera have sessile glands which at least in some species seem to produce a clear droplet of a susbtance that I hesitate to call resinous simply because I am not sure what determines a substance as a resin.

This substance does not evaporate completely and can be seen even on the petioles and undersides of the leaves in dried herborized specimens of some species like D.meristocaulis as hardened little beads. Here are some pics from the CP Photofinder where you can see these glands:

P1050532aa.jpg

meristocaulis01.jpg

Thanks for the help,

Fernando Rivadavia

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Thanks Lee!

So water soluble X lipid soluble, that seems like it might be easy to test -- any volunteers wanna try this with their cultivated plants?! :) I guess a needle could be used to pick the liquid off the leaves and used to try and dissolve these in a drop of water and in a drop of vegetable oil.

Here are some more pics taken by others showing these yellowish secretions on petioles of D.s.p"Cipó" and on the back of the leaves of D.camporupestris:

2520-07cipo.jpg

glandulas026-Cpia.jpg

Thanks, Fernando

Edited by Fernando Rivadavia

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Hey Fernando,

I think we have spoken about this issue in the past already, haven't we? Allen pointed out these " sessile glands" on several Australian pygmy species to me, too ;).

Drosera have sessile glands which at least in some species seem to produce a clear droplet of a susbtance that I hesitate to call resinous simply because I am not sure what determines a substance as a resin.

This substance does not evaporate completely and can be seen even on the petioles and undersides of the leaves in dried herborized specimens of some species like D.meristocaulis as hardened little beads

Take care:

Glands and glandular trichomes are not the same!

What you are referring to as sessile "glands" are in fact glandular trichomes (i.e. homologes to the nonglandular hairs that many Drosera species have on leaves or scape, or the "glands" of scape and sepals. All of them are trichomes, not glands). Glands are always vascularized (for nutrient transport). In contrast, glandular trichomes are outgrowths of the epidermis, and they can consist of a variable number of cells and can have different shapes. Laenger et al., 1995 and Seine & Barthlott, 1993 did already distinguish 14 different types of glandular and non-glandular trichomes on the leaves (mainly the petioles) of Drosera species (all sections except for that of D. meristocaulis ;)). The mullberry-shaped glandular trichomes of D. hartmeyerorum are homolog to these glandular trichomes pointed out by you, and might add another "type 15".

I am not aware of the content of the glandular tip of these yellowish trichomes, but I can tell you why it is still visible in herborized specimens: it is secreted underneath the cuticule (!) of the trichome head cells! That means it is covered by a cuticule, thus cannot dry out! Whereas the water-based polysaccharid secretion of the carnivorous glands is a dropplet, thus evaporates when drying out! ;)

I have tested it many times using binoculars: these glandular trichomes of D. meristocaulis (and others) are not sticky at all! They are like tiny versions of the mullberry-shaped trichomes of D. hartmeyerorum. I have no idea what they are for, but at least they are not sticky!

You are right, in D. meristocaulis, these glands are relatively big and conspicuous.

It's all in our paper (the one which we have been writing for 2 years now! ;)) already: these glandular trichomes of D. meristocaulis have a multiseriate head on a biseriate stalk, and thus match the trichome type referred to as "Rorella-type" by Laenger et al. Thus is another morphological synapomorphy for ....... ;);).

Cheers,

Andreas

PS: Lee, you are right: the glue of Drosera, Drosophyllum, Triphyophyllum, Pinguicula, Byblis is mucilage (water-based with high sugar content. It has to be water based in order to dissolve enzymes in). In contrast, the glue of Roridula is a resin. It never evaporates and cannot be washed away by rain. But big disadavantage: no enzymes can be dissolved in the glue droplets of Roridula. That's why this plant needs its little helpers for prey digestion.

Edited by Andreas Fleischmann

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Interesting observations!

A nice pet theorum would be that the resinous droplets are a form of protection to protect the newly emerging leaf from insect/herbivore damage.

Has anyone seen insects caught on the backs of such leaves? It would be very interesting to see if they are indeed waterproof, as is the case with Roridula.

Best Wishes,

Brian.

Edited by Drosera5150

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Has anyone seen insects caught on the backs of such leaves? It would be very interesting to see if they are indeed waterproof, as is the case with Roridula.

Brian, as mentioned above, these trichomes are NOT sticky. They are just glistening, but not adhesive. Like the yellow trichomes of D. hartmeyerorum.

Andreas

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Very curious observations indeed! Is there any speculation on what these secretions might be used for to benefit the plant? Perhaps they are just some random manifestations of something that hasn't yet been fully realized in its evolutionary development. Still very curious indeed! - Rich

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Andreas,

Thanks for the lengthy reply, but... you missed the point! :) I'm not asking what the hairs/ glands are, I'm just trying to find out what sort of substance they're producing. Like Lee said, I guess it boils down to whether we can dissolve the secretion in water or in oil. That is, after we puncture with a needle the cuticle you mentioned! ;)

So who's got some of these plants in cultivation and is willing to do the experiment? :)

Thanks, Fernando

Edited by Fernando Rivadavia

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Hi all and happy new year,

really very interesting point/observation.

It would be really interesting to know what they are for.

And nice to see one of my babies (the first picture), it´s now much bigger and has also flowered.

Also interesting that some pygmies are also having these glands (trichomes) after they are closely related.

I´m growing a bigger number of this species (also seedlings from my collected seed), these glands (trichomes) are occuring nearly almost in my plants that have flowered till now, medium plants are having nearly none (really only a small number and nearly only on undersides of the leaves) and smaller plants absolutely none. Most of them seem to be on the surface of the petiole, some on the undersides of the leaves (but not at the petioles) and even on the leaf itself including the tentacles.

On the first sight they seem to be yellowish but for me they are looking more colourless and a few of them are even slightely pinkish.

I´ve tried to take some pictures (i know they are not the best but a few things are perhaps visible), especially about the stickiness of these glands (trichomes).

Andreas, why do you think that they are not sticky at all?

Here it´s visible that these glands are on the upper side of the petioles, the left part of the leaf is the upper side.

meristocaulis10a.jpg

here are visible these glands also on the tentacles

meristocaulis2a.jpg

here is also a pinkish gland visible (the small one)

meristocaulis3a.jpg

they are even on the part of the leaf with tentacles

meristocaulis4a.jpg

the lower side of the leaf

meristocaulis7a.jpg

meristocaulis6a.jpg

here is an older leaf, nearly completely dried

meristocaulis11a.jpg

They are glistering but for me it´s looking like these glands (trichomes) are in fact also sticky.

meristocaulis8a.jpg

And here is a picture of a leaf that has been cutted 2 days ago, here the stickiness of this substance is also visible in my opinion but it´s also visible that this substance is evaporing a little bit, but not completely.

meristocaulis9a.jpg

And sorry again for the picture quality, a better result was not possible with my equipment.

Best regards,

Dani

Edited by Daniel O.

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Wow, amazing pics Dani! Thanks so much! So it does seem like there is an actual secretion, that the liquid is not encapsulated by a membrane. BTW, which species is this?

Thanks,

Fernando

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Hey Dani,

Thanks for sharing those pics!

Their appearance reminds me of the sessile glands present on Byblis rorida. I'm wondering if the droplets are sweet or scented like nectar.

Maybe some sort of insect attractant? Ok, time to taste them... :whistling::thumbsup:

Hopefully, you won't see floating Disney characters afterwards... :smile:

Happy Growing,

Brian.

Edited by Drosera5150

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Brian, it really would be interesting to know if the secretion is sweet or scented like nectar. But it will be difficult to get out, these droplets are really small. And who knows about the effect they will have. :D

Fernando, these pictures are pictures of D. meristocaulis leafes i´ve cutted before. :wink:

Yes, it really seems so as if it´s an actual secretion and that the liquid perhaps (probably) is not encapsulated by a real membrane.

I´ve also cutted a leaf and put it into distilled water, than i´ve waited an hour to take a new picture, it seems so as if this secretion is not water soluble after one hour.

Here is a picture after one hour in distilled water. The left part of the leaf is the lower side of the petiole, the right side is the upper side with this secretion.

meristocaulis12a.jpg

I´ll let the leaf in water till tomorrow to see if this will change, but i don´t think so.

Best regards,

Dani

Edited by Daniel O.

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Hey Dani,

Thanks for the extra info! Maybe the droplets are too dense to dissolve on their own in water. How about if you heat some water to near boiling and then try dropping a leaf (or some drops of this secretion) in it? Or even mechanically (with a pin or tooth pick?) mix one of these secretion droplets in a small quantity of water?

Best wishes,

Fernando Rivadavia

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Hello Dani,

Fantastic photos and observations! But your photos and reports (which are very convincing, no doubt!) are quite the contrary than I observed in my cultivated specimens of D. meristocaulis. The reason why I thought that they are not sticky is that I was able to remove them as "beads" using tweezers under a binocular. They did neither stick to the tweezers, nor to a hairs or piece of paper. Nor was I able to pierce the bead with a pin to remove any putative liquid. To me, these structures appeared to be entirely cellular. Your photos however tell quite the contrary.

But what is striking that the trichome's heads/secretions on your excellent photographs are appearing white translucent and much bigger than the more yellow structures on my plants. Do you grow your plants in high humidity?

What these trichomes remind me of most are hydratodes, which are commonly found in various plants. This would explain why the secretions would be bigger in higher humidity. Maybe the serve for absorption or resorption from the air?

Because although the Neblina massiv lies within the Amazon rainforest, this tepui is by far not a "rainy desert" it is thought to be! Several plants there are adapted to seasonally dry conditions and fires! The long fibrous stipules of D. meristocaulis are another character to indicate an adaptation to dryer conditions.

Nothing evloves in organisms without having a special function! These strange trichomes are found in several species (mainly Australian pygmies and several unrelated South American taxa (very conspicuous in D. sessilifolia, too!), thus they have to create a certain advantage! They are not found in the most relic species (D. regia, D. arcturi), thus cannot represent an acient remainant, they are likely to have evolved for some special reason.

Any ideas?

Andreas

Edited by Andreas Fleischmann

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Hey Andreas,

When you removed the "beads" was this from live plants? Could Dani's plants simply have produced more secretion (due to higher humidity?) until rupturing the cuticle?

I agree that these trichomes are probably specialized structures for capturing moisture, especially as they seem to be most prominent on the Brazilian species which grow in the driest conditions: D.schwackei, D.sp.Cipó, D.graminiflia, D.chrysolepis, and D.camporupestris.

Best wishes,

Fernando

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Hey Fernando,

When you removed the "beads" was this from live plants? Could Dani's plants simply have produced more secretion (due to higher humidity?) until rupturing the cuticle?

Both live and dried plant parts. However my plants are kept in the greenhouse, where humidity varies a lot. I remember Daniel grows his plants indoors, however in an open setup. Dani, can you confirm this?

I especially like Dani's "picture 0021": look at the 3rd gland on the petiole lower surface (facing upwards on the photo): here you can see the yellowish trichome head surrounded by the translucent secretion dropplet. The yellowish structure is found in my plants, too, but I did not observe the secretion yet. However I will try to do some observations in the early morning now, when humitidiy is fairly high.

I agree that these trichomes are probably specialized structures for capturing moisture, especially as they seem to be most prominent on the Brazilian species which grow in the driest conditions: D.schwackei, D.sp.Cipó, D.graminiflia, D.chrysolepis, and D.camporupestris.

Maybe they serve for gathering moisture for the sticky dropplets of the carnivorous tentacles? The "dew" of the tentacles has to be permanently "refilled" as it is constantly evaporating water, depending on air humidity (already Darwin noticed this). This could be an explanation why these glands are found on the tentacle bases, too. And they are especially concentrated on the lower lamina surface, and on the lower petiole side. These are the regions where the water transporting vascular tissue is situated!

On the other hand, the high-sugar content of the viscous dew of the tentacles itself is strongly hygrophoric (easy to notice in cultivation: the higher the humidity is, the bigger the dew dropplets get). Thus why should they evolve additional (more?) hydrophoric structures?

And most puzzling: these tiny trichomes have a stalk consisting of few cells only, they are not vascularized. This means: they actually should not be able for fast and efficient water transport.

Strange little things. What are they for?

Andreas

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Hello Andreas,

I especially like Dani's "picture 0021": look at the 3rd gland on the petiole lower surface (facing upwards on the photo): here you can see the yellowish trichome head surrounded by the translucent secretion dropplet.

Hmmm, not sure I see which one you're talking about. Maybe I just have to find a bigger screen...

Maybe they serve for gathering moisture for the sticky dropplets of the carnivorous tentacles? The "dew" of the tentacles has to be permanently "refilled" as it is constantly evaporating water, depending on air humidity (already Darwin noticed this). This could be an explanation why these glands are found on the tentacle bases, too. And they are especially concentrated on the lower lamina surface, and on the lower petiole side. These are the regions where the water transporting vascular tissue is situated!

That wouldn't explain their presence on the flower scapes though... Either way, once humidity is absorbed by such glands, it's all within the plant and would end up difusing through the tissues sooner or later, right? But it would make more sense to have them closer to where they are most needed (near the tentacles which are constantly losing water from evaporation).

Undersides of the leaves may be a good place to have these glands simply because it's more shaded and possibly more humid. Petioles upper/lower surface may be good in species with large stipules like D.meristocaulis simply because a more humid microclimate may be present there.

All the best,

Fernando Rivadavia

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Hi Andreas and Fernando,

Fantastic photos and observations! But your photos and reports (which are very convincing, no doubt!) are quite the contrary than I observed in my cultivated specimens of D. meristocaulis. The reason why I thought that they are not sticky is that I was able to remove them as "beads" using tweezers under a binocular. They did neither stick to the tweezers, nor to a hairs or piece of paper. Nor was I able to pierce the bead with a pin to remove any putative liquid. To me, these structures appeared to be entirely cellular. Your photos however tell quite the contrary.

thanks, i would also like to remove them as "beads" using tweezers, but with my equipment it´s for sure not possible.

Really strange that you have made totally different observations.

But what is striking that the trichome's heads/secretions on your excellent photographs are appearing white translucent and much bigger than the more yellow structures on my plants. Do you grow your plants in high humidity?

Yes, you are absolutely right, to me they are also appearing white translucent.

When i´m looking onto the hole plant without a microscope they are indeed appearing yellowish, like in the first picture Fernando has posted. But under the microscope they are looking white translucent.

As you perhaps rember i´m growing my plants in open trays under artificial lights, not in a terrarium, so the humidity is not very high. The plants are growing in 7cm high pots and they are standing permanently in about 1-2cm water, also during winter. The humidity is about 70-90 percent in the moment because i´m closing the window from time to time because of the low temperatures outside.

All these pictures i´ve taken at the evening.

look at the 3rd gland on the petiole lower surface (facing upwards on the photo): here you can see the yellowish trichome head surrounded by the translucent secretion dropplet.

The third droplet that is facing upwards? In my opinion these are 2 droplets very close to each other (in front of each other), otherwise there should be visible more of these yellowish trichome heads surrounded by a translucent secretion dropplet, but this one is the only one.

And another thing, these droplets are on the upper side ot the petioles not on the petiole lower surface. On the petiole lower surface are absolutely none except under the part with the tentacles.

Fernando, i´ve left the cutted leaf for one day in water with the result that these droplets are not solving in water.

And i also putted a cutted leaf in nearly boiling water, but there was no solvation. I´ll try it also with a pin or tooth pick, but it will not be very easy because of the size of the droplets (these pictures have been taken with a magnification of about 200)

Here a picture after the try with boiling water (the green part of the petiole is the lower side, the red one with the droplets is the upper part):

meristocaulis13a.jpg

Best regards,

Dani

Edited by Daniel O.

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Hi Dani and others,

Really interesting topic. Mysterious little trichomes.

I have a usb-microscope since a few months , so this topic was a good reason for a test

with D.camporupestris ( also from Dani ;-) and other species.

I don't grow D.meristocaulis, so I can't compare my pics with those from Dani.

But I've found some interesting trichomes on D.camporupestris :

Both trichomes are visible , yellowish and white translucent.

The yellowish trichome looks not sticky and covered with a membrane ,but the translucent trichome

is too small for my needle. They reminds me to the glue dropplets on the stalks of

D.rupicola or the droplets on Nepenthes

A: yellowish B: translucent

120912696.jpg

A:translucent B: yellowish

120912693.jpg

Older parts or dead leaves have mostly yellowish trichomes :

120912692.jpg

120912695.jpg

120912694.jpg

120912697.jpg

Young leafs have white translucent trichomes and they "look" also sticky,

but ( just like Dani ) is it not possible with my equipment.

120912698.jpg

120912699.jpg

Dani , are they also translucent on dried leafs?

And here is my first test with D.hartmeyerorum,clearly other trichomes as the pygmies and

South american species :

Fresh :

120912823.jpg

120912824.jpg

Dried after 1 day :

120912825.jpg

120912826.jpg

I will try it with more species during the weekend.

Cheers,

Iggy

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Hello Iggy,

Thanks for the wonderful pictures!! :)

So it seems like we may have 2 kinds of trichomes/ glands:

1. A (larger? yellow?) "dry" one that looks like a smaller version of the mulberry-like ones found in D.hartmeyerorum.

2. A (smaller? white/translucid?) "wet" one that actually secretes mucilage/resin.

I imagine the structure of these two trichomes is different, have you started making cross-section slides for the microscope yet Anreas F.?? :)

Now we need to find out if this secretion is mucilaginous or resinous... :)

Thanks guys!

Fernando Rivadavia

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So nobody else has found the time to play around with their plants and try these tests??? :)

Fernando

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