Thin liquid weeping from tip?

satellitehead(z8 ATL Metro)April 21, 2010

Tonight, I had this Italian Honey cutting with thin liquid running out of the top cut - so much liquid that it was running down the entire 4" of the exposed cutting. A few months back, I had similar liquid running out of a Latarrula cutting, it was also running out near the terminal end, but that one had a terminal bud, and the weeping was coming from base of the bud, where the bud meets the cambium. That Latarulla cutting never did make it, even as strong and thick as it looked, even with all the amazing roots, it just shrivelled up and went limp, and the terminal buds never broke.

Even stranger, in the two minutes it took me to finish what I was doing and walk to get my Blackberry to take a picture of the liquid cascading down the cutting, the liquid evaporated, so I couldn't show you that there was a puddle the entire width of the cutting flowing from the clearly-soaked cut site on top. There was no residue left behind after evaporation. This wasn't sap.

This cutting has been subjected to no different amount of watering or other environmental variables than any other cutting I'm rooting right now (we talking ~50-60 cuttings or more in bins).

So, what exactly is it?

As you see below, the tip is still soaking wet in this picture - I didn't cut it recently, it came alread-cut like this several weeks ago. This cutting isn't super important to me because I have 6 backups of the same variety rooting just fine, with no liquid flow out of the top. I just want to know what this is for future reference, since I've never encountered it with other fruits and veggies I've propagated.

NOTE: A leaf or two is slightly mottled ad one is snapped off because the cutting sprouted in the bag prior to rooting. I never take my cuttings out until they're showing reasonable numbers of actual roots.

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tapla (mid-MI z5b-6a)

It's sap. Pressure that causes sap to rise through a plant stem to the leaves is called root pressure and is what causes the exudate you're observing. It's most prevalent at night when soil levels are high and plant turgidity at its peak, or when transpiration is low during the day. The low volume of leaves on the cutting would automatically mean o/a transpiration would be very low. When transpiration rates are high, xylem sap pressure is reduced to 0 or less because it is usually under tension instead of pressure, due to the sap being 'pulled' by transpiration.

Active transport of mineral nutrient ions into the xylem is what creates the pressure that causes the exudation. During periods of low transpiration, movement of ionic solutes is reduced and the ions become concentrated in root xylem tissues, which lowers the water potential gradient. Water can then diffuse from the soil into the root xylem via osmotic movement. The accumulation of water in the xylem actually causes a physical pressure, pushing on the rigid cells and thus moving water and nutrients up the stem.

This process usually occurs in short plants and in organs not too distal from roots. In this case, the truncated cutting is obviously rather short. ;o)

Al

    Bookmark   April 21, 2010 at 3:27PM
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gorgi(z7a_NJ)

>>> It's sap.
I tend to agree; I have seen this post on the other FF,
but I was not sure how to respond. It is like when
pruning trees in "late" sping - I had grapes actually
"dripping" off sap/water.

However, I have never experienced that with fig cuttings.
Usually the ends "seal" off by that (in)famous white-latex.
Man, those fig cuttings must have some good roots/plumbing
to "push-up" all that miosture...

    Bookmark   April 21, 2010 at 4:37PM
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tapla (mid-MI z5b-6a)

I should have said, "It's most prevalent at night when soil moisture levels are high and plant turgidity at its peak ...."

Sorry for the omission of the word 'moisture'.

Al

    Bookmark   April 21, 2010 at 4:43PM
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satellitehead(z8 ATL Metro)

I don't doubt that you are correct, but for what it's worth, this is nothing like the sap from cutting a branch. This evaporates quickly. It is not slippery or sticky, it's just watery. It is not milky, it is transparent. It has no scent, whereas normal fig sap has a cinammon-vanilla smell to me.

The roots of this thing are abundant and heavy. The gentleman that gave me these cuttings told me ahead of time that this one was a "heavy rooter", I've heard it before, but in this case, it's very true.

    Bookmark   April 21, 2010 at 9:34PM
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tapla (mid-MI z5b-6a)

Not all the trees cells/tissues are laticiferous (latex producing). The white milky 'latex-looking' exudate in evidence at wound sites originates as the cytoplasmic fluid of laticiferous cells and tissues only. The cells or vessels in which the milky latex you referred to is found make up what is called the the cutting's laticiferous system, which can form in 2 different ways. For figs, and many other plants, the system is formed from rows of cells laid down in the vascular meristem, which is a type of tissue in plants consisting of unspecialized/undifferentiated cells called meristematic cells (you know the term 'STEM cells'? It comes from an abbreviated version of 'meristematic cells'), found in plant parts where there is growth potential or where growth is occurring.

The cell walls of cells containing the 'latex' are dissolved so that continuous tubes, called latex vessels, are formed. Not much is known about WHY so many plants form this milky secretion, but it is thought that it is helpful for sealing wounds, repelling insects, etc.

Water and solutes dissolved in the water still move freely about the plant. We know that the milky material is not absorbed from the soil, and since it is centralized in the in the vascular cambium/laticiferous system, it's not difficult to picture the vascular cambium as being suberized and sealed off at the distal end of the truncated cutting (so no latex leakage), while water and dissolved solutes are still able to move freely upward through and finally out of the truncated xylem tissue.

I just recently lopped off an Echeveria (a succulent) so I could treat the top as a cutting. I usually seal the cut end of the old stem with waterproof wood glue so the stem doesn't dessicate & die back. Normally, I'll get up to a dozen breaks back on the old stem which I can in turn, propagate and turn into new plants to share (this is a particularly beautiful cultivar). I'm getting off track - sorry. This plant oozed clear sap like you describe every night for at least a week before I could finally reapply the glue so it would seal the wound. It has about 8 new plants breaking from the old stem now, after about another week of waiting.

I had a long day, so I hope what I said was understandable. ;o)

Al

    Bookmark   April 21, 2010 at 11:00PM
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satellitehead(z8 ATL Metro)

Made perfect sense! Thanks for the info.

    Bookmark   April 23, 2010 at 9:37PM
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