Are there one-way check valves in trees?

John_KAYS

John_KAYS

Carpal tunnel level member
Location
Eastern PA
I kind of buried this question in another thread, so I thought I might dig it up for more to see.

Are there one-way check valves in trees?

I am familiar with the transpirational pull and that, while living, the tree’s water flow is pulled up through the xylem to the leaves and all, but is there perhaps a mechanism that helps fight the gravitational pull?

Here is why I have this inclination – When tipping a fresh cut log upside down (I most notice it during negative blocking) the sap seems to poor out while it hardly flows when hanging upright). There might not be anything to this, but I thought I would ask if any of you have noticed this happening or better yet if you know the biology behind it??? It seems to me that there is a one way check valve that encourages one way flow...what do you think?

Thanks.
 
If you search for redwoods, rain, fog, and the name Dawson, you will probably find several articles or research topics about redwoods being able to move moisture both directions. It may be most of, or part of an article, like this one ...

LINK >>> Article about redwoods, fog, rings, etc..

Some trees may be different, but that's the case with redwoods.

Keep in mind too, that foliar feeding of plants or trees could not work well without a two-way movement of water.
 
Oh yeah, I understand there is two-way movement and a lot of that is in the phloem with the carbohydrates, but the pull of evaporating molecules contributes largely to the current of upward water flow in the xylem - but that doesn't explain the log section after being removed from the tree still seeming to hold the water when upright and to empty when tipped over. I have not done much experimenting with this, so I don't even know how accurate it is...I just notice it especially with hard woods, I think.

And that is interesting about the redwoods absorbing moisture through their leaves. They also have a LONG haul to pull that water from the ground!
 
Okay, so nobody has experienced this? I just did a little google research and found this article using "check valves" to explain why trees don't bleed to death. Could this be the same mechanism at play that I have noticed when taking down a live tree, or maybe not? I couldn't decide if the check valve in the article was one-way or not.

Maybe someone with a better understanding of this subject could help me figure out if this could be related.
confused.gif
 
And here is on about Evergreens and check valves in the winter:

"Water forms solid crystals when it freezes. The crystals cannot move through plant xylem. The formation of ice crystals causes the release of gas. The gases cause bubbles in the water column, breaking the cohesive flow of water. So how can trees possibly survive cold winters?

Deciduous trees simply grow new xylem tubes in the spring. This new water transport system, along with all new phloem tissue creates the next annual growth ring in the trunk of broadleaf trees.

Because conifers have leaves that are steadily losing water out of their stomata, through transpiration, the water columns have to remain stable through freezing and thawing. This is accomplished by check valves between each transport tube. As the plant sap freezes, it expands. The expansion causes the valves between the tubes to close. The pressure, up to 900 psi, is held within the walls of the tubes until the crystals thaw. When the water returns to a liquid state, the check valves open and flow is restored. When active growth returns in the spring, conifers will produce new xylem and phloem." - http://www.ozarkfolkcenter.com/herbs/yarb_tales/12-16-13.aspx

Ok - so I am not spending time on validating sources, so take it as it is.

I swear I'm on to something.
 
Thanks JK for the link to the Virginia Tech article. I hadn't seen that interview with my friends and colleagues Jody Jellison and Barry Goodell (a husband and wife team). That paper (which I had seen) does give nice new details on a process that was described at least a hundred years ago.

Sure, bordered pits in conifers serve to block the flow of air into tracheids (the open pipes) that contain water under tension. Sort of similarly, tyloses do similar things for broadleaved tree vessels. Both processes are reactions to sudden changes from negative pressure (or suction) up to atmospheric pressure. So sure, those are check valves, in a manner of speaking. That's a big component of Wall 1 in the Shigo CODIT model.

But that is wholly different from what I took to be the initial question., that is, does xylem sap drain more quickly from one end of a stem segment than another end. I haven't observed that. That's why I didn't respond right away.

Like everything else in our thermodynamic world, stuff tends to move downhill, or down concentration gradients. Sure, if the pathway is blocked, it's blocked! But even water moving up to the top of a tree is still flowing "downhill" with respect to the concentration gradient. The greater "suction" from evaporation at the foliage surface lowers the water concentration, so it still is flowing down from where it is to where it isn't...even if it is up a tall tree.

Sure, stuff can roll uphill...if some external energy is supplied. Isn't the 2nd Law of Thermodynamics grand!
 
[ QUOTE ]
Isn't the 2nd Law of Thermodynamics grand!

[/ QUOTE ]

Is that the one about a group of workers tending toward longer lunch hours?
 
Kevin, Thanks for the response.

"But that is wholly different from what I took to be the initial question., that is, does xylem sap drain more quickly from one end of a stem segment than another end. I haven't observed that. That's why I didn't respond right away."

Kevin, you said it better than I did, you understand it better than I do, even though you haven't observed it before...and I don't even know if there is anything to really observe. I'm impressed.

After reading your friends paper, quite good I must say, my question was just that: Is it wholly different from my initial question? I am quite honored to have such a thorough response from you. I do not have the experience or knowledge that you do and am learning and benefiting from every post you share.

With the thermodynamic 'down hill' movement you brought up, is there anything to suggest that the xylem sap would drain more quickly from one end of a stem segment than another? Is the system broken when the segment is cut?
Does the 'top' of the stem segment maintain the greater suction or downhill movement?

When the opportunity presents itself - I will, of course, try to capture it on video.

Thanks for your guidance.
 
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