Tree sap question

Broadback · Joined: 04 Aug 2007 Posts: 72

Just curious. As I understand it the evaporation of moisture is what
draws the sap from the toots up the tree. Does this mean that the sap
does not rise until the leaves unfurl? If so where do the leaves obtain
the energy to be "kick started"?

Archived from group: uk>rec>gardening

Nick Maclaren · Joined: 01 Aug 2007 Posts: 430

In article ,
Broadback writes:
|>
|> Just curious. As I understand it the evaporation of moisture is what
|> draws the sap from the toots up the tree. Does this mean that the sap
|> does not rise until the leaves unfurl? If so where do the leaves obtain
|> the energy to be "kick started"?

'Tain't so. Sounds plausible, until you think about it. If that
were so, how would the sap reach the top of a 50' tree? Even a
vacuum will raise water only 30'.

That explanation was proposed and debunked by early in the 19th
century - but, like all myths, cannot be killed by mere disproof.

Regards,
Nick Maclaren.

PK · Joined: 01 Jan 2008 Posts: 14

"Nick Maclaren" wrote in message $gbl$1@gemini.csx.cam.ac.uk...
>
> In article ,
> Broadback writes:
> |>
> |> Just curious. As I understand it the evaporation of moisture is what
> |> draws the sap from the toots up the tree. Does this mean that the sap
> |> does not rise until the leaves unfurl? If so where do the leaves obtain
> |> the energy to be "kick started"?
>
> 'Tain't so. Sounds plausible, until you think about it. If that
> were so, how would the sap reach the top of a 50' tree? Even a
> vacuum will raise water only 30'.
>
> That explanation was proposed and debunked by early in the 19th
> century - but, like all myths, cannot be killed by mere disproof.
>
>
> Regards,
> Nick Maclaren.

Interesting post on this at another forum:
http://www.city-data.com/forum/garden/53891-spring-tree-sap-rising.html

pk

Broadback · Joined: 04 Aug 2007 Posts: 72

PK wrote:
> "Nick Maclaren" wrote in message
> $gbl$1@gemini.csx.cam.ac.uk...
>>
>> In article ,
>> Broadback writes:
>> |>
>> |> Just curious. As I understand it the evaporation of moisture is what
>> |> draws the sap from the toots up the tree. Does this mean that the sap
>> |> does not rise until the leaves unfurl? If so where do the leaves
>> obtain
>> |> the energy to be "kick started"?
>>
>> 'Tain't so. Sounds plausible, until you think about it. If that
>> were so, how would the sap reach the top of a 50' tree? Even a
>> vacuum will raise water only 30'.
>>
>> That explanation was proposed and debunked by early in the 19th
>> century - but, like all myths, cannot be killed by mere disproof.
>>
>>
>> Regards,
>> Nick Maclaren.
>
>
>
> Interesting post on this at another forum:
> http://www.city-data.com/forum/garden/53891-spring-tree-sap-rising.html
>
> pk
>
Very interesting PK, does not answer my question though. OK Nick if that
theory is wrong what is the actual answer as to how sap gets up the tree?

Nick Maclaren · Joined: 01 Aug 2007 Posts: 430

In article ,
Broadback writes:
|>
|> >> |> Just curious. As I understand it the evaporation of moisture is what
|> >> |> draws the sap from the toots up the tree. Does this mean that the sap
|> >> |> does not rise until the leaves unfurl? If so where do the leaves
|> >> obtain
|> >> |> the energy to be "kick started"?
|> >>
|> >> 'Tain't so. Sounds plausible, until you think about it. If that
|> >> were so, how would the sap reach the top of a 50' tree? Even a
|> >> vacuum will raise water only 30'.
|> >>
|> >> That explanation was proposed and debunked by early in the 19th
|> >> century - but, like all myths, cannot be killed by mere disproof.
|> >
|> Very interesting PK, does not answer my question though. OK Nick if that
|> theory is wrong what is the actual answer as to how sap gets up the tree?

Well, it appears that I was wrong! Mostly.

It seems that the plant physiologists do regard evaporation of moisture
as being the driving force, but the books I looked at gloss over the
physics so badly as to make the explanation physical nonsense. And they
were undergraduate plant physiology references, too! My daughter
confirms that corresponds with what they were taught.

Reading between the lines, it seems that the mechanism is driven as
you might expect, but with surface tension of the hydrophilic cell walls
being a critical aspect. However, the way that solar energy is translated
into potential energy is still baffling the plant physiologists - after
over a century of studying the problem!

And neither book had even a hint of an answer to your question.

Regards,
Nick Maclaren.

Charlie Pridham · Joined: 27 Sep 2007 Posts: 262

In article , nmm1@cus.cam.ac.uk
says...
>
> In article ,
> Broadback writes:
> |>
> |> >> |> Just curious. As I understand it the evaporation of moisture is what
> |> >> |> draws the sap from the toots up the tree. Does this mean that the sap
> |> >> |> does not rise until the leaves unfurl? If so where do the leaves
> |> >> obtain
> |> >> |> the energy to be "kick started"?
> |> >>
> |> >> 'Tain't so. Sounds plausible, until you think about it. If that
> |> >> were so, how would the sap reach the top of a 50' tree? Even a
> |> >> vacuum will raise water only 30'.
> |> >>
> |> >> That explanation was proposed and debunked by early in the 19th
> |> >> century - but, like all myths, cannot be killed by mere disproof.
> |> >
> |> Very interesting PK, does not answer my question though. OK Nick if that
> |> theory is wrong what is the actual answer as to how sap gets up the tree?
>
> Well, it appears that I was wrong! Mostly.
>
> It seems that the plant physiologists do regard evaporation of moisture
> as being the driving force, but the books I looked at gloss over the
> physics so badly as to make the explanation physical nonsense. And they
> were undergraduate plant physiology references, too! My daughter
> confirms that corresponds with what they were taught.
>
> Reading between the lines, it seems that the mechanism is driven as
> you might expect, but with surface tension of the hydrophilic cell walls
> being a critical aspect. However, the way that solar energy is translated
> into potential energy is still baffling the plant physiologists - after
> over a century of studying the problem!
>
> And neither book had even a hint of an answer to your question.
>
>
> Regards,
> Nick Maclaren.
>
Trees do all sorts of clever stuff, I remember reading something about
Oak trees pumping water with their deep tap roots and pushing this out
into the soil near the surface where their feeder root system is in
prolonged dry weather. So they obviously have quite a degree of control
in the process are are not just at the mercy of the elements. I will try
and find the artical as it may shed some light on the way the system
works (which I always thought was mainly capillary, but then they must
be able to turn that off in winter?)
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea

Broadback · Joined: 04 Aug 2007 Posts: 72

Charlie Pridham wrote:
> In article , nmm1@cus.cam.ac.uk
> says...
>> In article ,
>> Broadback writes:
>> |>
>> |> >> |> Just curious. As I understand it the evaporation of moisture is what
>> |> >> |> draws the sap from the toots up the tree. Does this mean that the sap
>> |> >> |> does not rise until the leaves unfurl? If so where do the leaves
>> |> >> obtain
>> |> >> |> the energy to be "kick started"?
>> |> >>
>> |> >> 'Tain't so. Sounds plausible, until you think about it. If that
>> |> >> were so, how would the sap reach the top of a 50' tree? Even a
>> |> >> vacuum will raise water only 30'.
>> |> >>
>> |> >> That explanation was proposed and debunked by early in the 19th
>> |> >> century - but, like all myths, cannot be killed by mere disproof.
>> |> >
>> |> Very interesting PK, does not answer my question though. OK Nick if that
>> |> theory is wrong what is the actual answer as to how sap gets up the tree?
>>
>> Well, it appears that I was wrong! Mostly.
>>
>> It seems that the plant physiologists do regard evaporation of moisture
>> as being the driving force, but the books I looked at gloss over the
>> physics so badly as to make the explanation physical nonsense. And they
>> were undergraduate plant physiology references, too! My daughter
>> confirms that corresponds with what they were taught.
>>
>> Reading between the lines, it seems that the mechanism is driven as
>> you might expect, but with surface tension of the hydrophilic cell walls
>> being a critical aspect. However, the way that solar energy is translated
>> into potential energy is still baffling the plant physiologists - after
>> over a century of studying the problem!
>>
>> And neither book had even a hint of an answer to your question.
>>
>>
>> Regards,
>> Nick Maclaren.
>>
> Trees do all sorts of clever stuff, I remember reading something about
> Oak trees pumping water with their deep tap roots and pushing this out
> into the soil near the surface where their feeder root system is in
> prolonged dry weather. So they obviously have quite a degree of control
> in the process are are not just at the mercy of the elements. I will try
> and find the artical as it may shed some light on the way the system
> works (which I always thought was mainly capillary, but then they must
> be able to turn that off in winter?)
Thanks peeps, even though it does not answer my question. Makes me
wonder if they do resolve it they may have it on a solution to harbour
the sun's energy, then perhaps we can get rid of those ugly wind farms!

Mary Fisher · Joined: 01 Aug 2007 Posts: 271

"Broadback" wrote in message
....

> Thanks peeps, even though it does not answer my question. Makes me wonder
> if they do resolve it they may have it on a solution to harbour the sun's
> energy, then perhaps we can get rid of those ugly wind farms!

Not everyone thinks that they're ugly.

Mary

Amethyst Deceiver · Joined: 24 Jan 2008 Posts: 26

In article ,
mary.fisher@zetnet.co.uk says...
>
> "Broadback" wrote in message
> ...
>
> > Thanks peeps, even though it does not answer my question. Makes me wonder
> > if they do resolve it they may have it on a solution to harbour the sun's
> > energy, then perhaps we can get rid of those ugly wind farms!
>
> Not everyone thinks that they're ugly.

Indeed. We were quite delighted to spot a new windfarm on the way to
work recently.
--
Linz
Wet Yorks

Broadback · Joined: 04 Aug 2007 Posts: 72

Amethyst Deceiver wrote:
> In article ,
> mary.fisher@zetnet.co.uk says...

>> Not everyone thinks that they're ugly.
>
> Indeed. We were quite delighted to spot a new windfarm on the way to
> work recently.

No accounting for taste, I do know that I would not like them near me,
their noise pollution is tremendous. My AD they must have been erected
quickly! Wink

user · Joined: 01 Jan 2008 Posts: 105

On 26 Feb 2008 10:05:36 GMT, nmm1@cus.cam.ac.uk (Nick Maclaren) wrote
and included this (or some of this):

>In article ,
>Broadback writes:
>|>
>|> Just curious. As I understand it the evaporation of moisture is what
>|> draws the sap from the toots up the tree. Does this mean that the sap
>|> does not rise until the leaves unfurl? If so where do the leaves obtain
>|> the energy to be "kick started"?
>
>'Tain't so. Sounds plausible, until you think about it. If that
>were so, how would the sap reach the top of a 50' tree? Even a
>vacuum will raise water only 30'.

Then try Osmosis. It's very powerful, and not limited to 30'

http://en.wikipedia.org/wiki/Osmosis

--
®óñ© © ²°¹°-°²

David in Normandy · Joined: 10 Feb 2008 Posts: 43

Broadback says...
> Just curious. As I understand it the evaporation of moisture is what
> draws the sap from the toots up the tree. Does this mean that the sap
> does not rise until the leaves unfurl? If so where do the leaves obtain
> the energy to be "kick started"?
>

I think that at least part of the mechanism involves the
roots pumping the water upwards. I seem to remember from my
student days that this was sometimes with considerable
force which can actually made the leaves "bleed" - a
process called "gutation" if I remember correctly.

There are also other mechanisms such as capillary action to
draw water along very fine tubules.
--
David in Normandy. DavidinNormandy@yahoo.fr
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted.

Nick Maclaren · Joined: 01 Aug 2007 Posts: 430

In article ,
®óñ© © ²°¹°-°² writes:
|>
|> >'Tain't so. Sounds plausible, until you think about it. If that
|> >were so, how would the sap reach the top of a 50' tree? Even a
|> >vacuum will raise water only 30'.
|>
|> Then try Osmosis. It's very powerful, and not limited to 30'
|>
|> http://en.wikipedia.org/wiki/Osmosis

An old and good physical rule is that, if your explanation allows
you to construct a perpetual motion machine, your explanation is
wrong.

Osmosis still requires energy to drive it.

Regards,
Nick Maclaren.

user · Joined: 01 Jan 2008 Posts: 105

On 27 Feb 2008 17:06:46 GMT, nmm1@cus.cam.ac.uk (Nick Maclaren) wrote
and included this (or some of this):

>
>In article ,
>®óñ© © ²°¹°-°² writes:
>|>
>|> >'Tain't so. Sounds plausible, until you think about it. If that
>|> >were so, how would the sap reach the top of a 50' tree? Even a
>|> >vacuum will raise water only 30'.
>|>
>|> Then try Osmosis. It's very powerful, and not limited to 30'
>|>
>|> http://en.wikipedia.org/wiki/Osmosis
>
>An old and good physical rule is that, if your explanation allows
>you to construct a perpetual motion machine, your explanation is
>wrong.
>
>Osmosis still requires energy to drive it.

Osmosis is not perpetual motion. The attractant is fuelled by our
beneficent sun.

--
®óñ© © ²°¹°-°²

Charlie Pridham · Joined: 27 Sep 2007 Posts: 262

In article , ron@spamall.com
says...
> On 27 Feb 2008 17:06:46 GMT, nmm1@cus.cam.ac.uk (Nick Maclaren) wrote
> and included this (or some of this):
>
> >
> >In article ,
> >®óñ© © ²°¹°-°² writes:
> >|>
> >|> >'Tain't so. Sounds plausible, until you think about it. If that
> >|> >were so, how would the sap reach the top of a 50' tree? Even a
> >|> >vacuum will raise water only 30'.
> >|>
> >|> Then try Osmosis. It's very powerful, and not limited to 30'
> >|>
> >|> http://en.wikipedia.org/wiki/Osmosis
> >
> >An old and good physical rule is that, if your explanation allows
> >you to construct a perpetual motion machine, your explanation is
> >wrong.
> >
> >Osmosis still requires energy to drive it.
>
> Osmosis is not perpetual motion. The attractant is fuelled by our
> beneficent sun.
>
>
>
Can't be that alone, as if you prune something off it bleeds all night
long.
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea

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