Silver Underneath

[Dypsisdean]

Although "why" might not be the correct question when it comes to evolution, there is usually a reason that things have evolved a certain way, even if we don't understand it.

For example, we have discussed possible reasons for why some new leafs have reddish color.

I have never read or heard of any theories as to why so many palms have silver or white on the underside of their leafs. Does anyone have any ideas?

[cryptobionic]

No scientist here, but merely by observation I've noticed that palms (and other plants) with white/silver/waxy undersides are much more resistant to small sucking insects like ahpids, scale, etc. Which makes sense, since most of these insects tend to lurk underneath leaves, sheltered from rain.

One theory is that this coating protects plants from pathogens splashed up from the soil, which is questionable, because bare soil (in general) is rare in plant communities and certainly doesn't apply to most palms which don't develop this coating till older.

[Bennz]

Breaking the first rule of polite conversation (ie avoid politics and/or religion), the simple answer is because the creator liked it that way!

How else are we supposed to recognise the difference between Archontophoenix cunninghamiana and alexandrae in our gardens?

Ok, no doubt there is another explanation, but I cant resist this sort of thing sometimes....

Also not a scientist, but silver plants tend to be better in drought or coastal locations. Also often in cold sites, take the large number of silver leaved Eucalyptus in higher altitude and arid parts of Aussie for example. Possibly this is totally unrelated to palms.

[BS Man about Palms]

(Dypsisdean @ Aug. 24 2006,19:14)

QUOTE

Although "why" might not be the correct question when it comes to evolution, there is usually a reason that things have evolved a certain way, even if we don't understand it.

For example, we have discussed possible reasons for why some new leafs have reddish color.

I have never read or heard of any theories as to why so many palms have silver or white on the underside of there leafs. Does anyone have any ideas?

Dean!  I think its when the lizards look up from the ground, they think they are looking at the sky....its cheaper than crack!.....  I dunno, maybe it helps reflect the ground heat back down......hows that for far fetched? ???

Bill

PS-Worked in the gated community with Mardy Darians home in it, today.   I figured I'd just drive around till I saw a "tropical paradise".....  Well, I found 3 places!!  all on the same street, one with a LOT of tropicals and quite dense, several things I'd never seen before....one with about half as much and a Ravena Rivularis with about 18' of clear trunk....and another with lots of tropicals and a GATE!

Can you guess which one I surmised, then my customer confirmed, was his??  :laugh:

[MattyB]

Also not a scientist, but silver plants tend to be better in drought or coastal locations. Also often in cold sites, take the large number of silver leaved Eucalyptus in higher altitude and arid parts of Aussie for example. Possibly this is totally unrelated to palms.

I think that's a good observation but dosen't seem to make sense with only the leaflet undersides being silver.  Maybe it's an insect repellant.  My Dypsis psamophila needed that yesterday when every leaf on one stem was completely eaten right down to the petioles.  Must have been a grasshopper.....arrrhhhhh

[Daryl]

Silver undersides evolved so that you can train a garden spotlight on them at night time and REALLY enjoy looking at them!

Daryl.

[tim_brissy_13]

To reduce moisture loss through the leaves?

[Neofolis]

I was thinking like Bill that it may be a camouflage thing to blend in with the sky.  In theory it would attract less crawling things that eat green stuff.

[Dypsisdean]

The blending in with the sky idea gave me another theory along the same line. Maybe the bugs that like to inhabit the underside of leafs like it darker. If they are trying to search out the dark side of the leaf, they would find a bright underside confusing. I had thought bugs camped out underneath the leafs to stay dry, out of the rain and dew. Maybe there are other reasons, like avoiding well lit areas.

[Gileno Machado]

(tim_brissy_13 @ Aug. 25 2006,06:18)

QUOTE

To reduce moisture loss through the leaves?

This is also my opinion Tim.

The champion wax pruducing palm is probably the Copernicia prunifera species Carnaúba , native to my region, inland. Carnauba leaves are industrialized and transformed into car polish wax, and they have been planted for that reason for decades, and compared with other brazilian and caribbean species at a test field in Ceará, by an american company called Johnson, which has large industrial wax plants in Brazil. That is a species that loves water, tolerating eventual floods, but in their natural habitat they have to be prepared to cyclic periods of severe drought (sometimes with no practical rainfall in a year) and high strong sunlight exposure. Maybe someone could explain this in scientific/botanic terms, but I think that slowing down the long term transpiration of the plant in the heat, could be the main reason for the coating (?).

[Dypsisdean]

Now I agree that the glaucous waxy coating on the crowns and leafs of many palms reduces the amount or water a palm may lose to it's environment.

However, I have been asking about the silver or white that is on the back side of the leaflets on a palm that is otherwise all green. This coloration, to me, apppears to be entirely different. If looked at closely it doesn't seem to be "waxy." In some palms it doesn't even appear "solid" or uniform when viewed under magnification. Hence not forming a barrier as does the waxy coating on parts of many palms from hot dry climates. In addition, many palms with this silver backside come from very wet humid locations, so I would assume perserving water is not a priority.

[Joe palma]

I agree w/ Dean here. Palm Leaflets/fans that have a green topside and a white underside do not seem to have that underside wax coated. Just my observation w/ Kerriodoxa elegans, Lytocarium weddellianum, Arenga engleri and Archotos (I'm going to take a closer look this eveing however).

As well, on my silver back med fan (which is awesome) the silvering does not completely cover the underside, almost like it is a fuzz or some thing. Not the best water retainer.

Here's a thought, don't know where it will lead, on the wind side a of a plant (the side in which the wind is coming from), when the wind is blowing strong, the bottom of the frond is generally what is exposed.

Helps w/ wind????

Having said that, I'm leaning toward the insect theories.

Joe

[Matt in SD]

The insect ideas are interesting, although I can think of a different reason from what you all have proposed.  Plant sucking bugs are easier to see against a white background, at least for us and probably also for the beneficial insect predators.  For example the easiest way to detect mights is to tap a leaf over a clean white sheet of paper and then look at the paper.  Mites are absolutely, positively easier to see on leaves with white undersides than green leaves.

That said, however, in my experience plants with very thick, smooth leaves (like most New Caledonian palms) seem to be the most resistant to insect pests (mites mainly).  I've had mite problems in a Ceroxylon and a Wallichia, both of which have white undersides on the leaves.

Matt

[Walter John]

In the cells of green leaves, photosynthesis takes place in molecules of a substance known as chlorophyll. Sunlight strikes the chlorophyll, then photosynthesis takes place.

Sunlight is made up of many colors. When sunlight falls onto a glass prism, the prism breaks the light into its rainbow of colors.

It happens that chlorophyll doesn't use all of sunlight's rainbow of colors. It absorbs only the red and blue part of the spectrum, so the light that's left, the light that reflects back to our eyes is green.

Green leaves are green because chlorophyll absorbs all of sunlight's rainbow of colors except the green part, which is reflected.

So.........if it ain't green brothers and sisters, it's simply that the nature of the palm in question is designed to be interested in those parts of the spectrum so the green is gone. This helps keep insects away because they would be seen on silver/white and become prey to other critters like Tyrannosaurus Rex.

Reminds me of the great tune by the aussie group Spectrum "I'll be gone".  I think I'll put the MP3 on now. Have a nice day folks and remember to send Gileno a birthday PM. There's another MP3 I've got Suzie Quatro's 48 crash

[DoomsDave]

Hmm.  INteresting question.

The answer might be that it's not a particular disadvantage . . . .

dave

[Alberto]

(Wal @ Aug. 25 2006,19:10)

QUOTE

In the cells of green leaves, photosynthesis takes place in molecules of a substance known as chlorophyll. Sunlight strikes the chlorophyll, then photosynthesis takes place.

Sunlight is made up of many colors. When sunlight falls onto a glass prism, the prism breaks the light into its rainbow of colors.

It happens that chlorophyll doesn't use all of sunlight's rainbow of colors. It absorbs only the red and blue part of the spectrum, so the light that's left, the light that reflects back to our eyes is green.

Green leaves are green because chlorophyll absorbs all of sunlight's rainbow of colors except the green part, which is reflected.

I read somewhere that some leaves of plants in dark forests are red on the undersides because the red collor is reflected the second time back through the leaves,so there is a maximum of effect with a minimum of light.

  White also reflects all the radiating energy of light  back, maybe that´s an answer.....?

[xerophyte_nyc]

Here's a thought-

While tender fronds are unfolding, the white and/or waxy covering helps deflect some sun and heat, helping to protect the young vulnerable growth...the coloring simply maintains itself as the leaf matures.

Many succulent species have adapted a similar mechanisms, along with hair and fuzz, to protect new leaves before they harden and mature.

x

[Trópico]

The best of both worlds. The leaf is both optimized for sunlight intake (top green portion) and at the same time moisture retention (silvery underside). When the wind blows upon the leaf the wind is hitting the underside directly. Probably an adaptation for places that can be humid but with seasonal dry winds. The third aspect, beauty, is our perception of the above traits.