Guttation?

Discussion in 'Plants: Science and Cultivation' started by Junglekeeper, Sep 14, 2005.

  1. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    One of my plants, Aglaia odorata, always has drops of clear sap on its stems and leaf surfaces. This appears to be a natural condition as much of the sap is exuded from the same places on the plant parts. The plant is healthy and free of pests and the sap stays on the tree, not the floor (thank goodness).

    The term 'guttation' is used to describe the appearance of drops of water on leaf tips caused by root pressure and the most common example given is that of water at the end of a blade of grass. A few sources also mention the presence of salts, minerals, and sugars in the water. Is this term applicable to what I'm seeing in my plant? I'm not worried about the condition, just wondering what it's called.
     
  2. mr.shep

    mr.shep Well-Known Member 10 Years of Activity

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    Junglekeeper, I am not sure I will be much
    help.

    Guttation used to be associated with the
    hydathodes, not necessarily used along
    with other external secretory structures
    such as glandular trichomes and the
    nectaries of which these can contain
    sugars, salts and minerals.

    Hydathodes, modified parts of leaves,
    discharge water originating from the
    interior of the leaf to the surface. The
    exudation of water originating from the
    xylem out through the leaves is called
    guttation.

    When the same or similar water droplets
    are also seen on the petioles and stems is
    where I do not feel comfortable thinking
    the term guttation applies to them also.

    Below is a link that gives rise to a conflict
    in that the hydathodes can have some salt
    content in the discharge but I don't remember
    them having sugar in them. The nectaries
    involve the phloem as well as the xylem
    and can transpire solutes, sometimes called
    salt glands. Nectariferous glands can be
    found on the petioles of a variety of plants.

    http://www.biologie.uni-hamburg.de/b-online/e05/05a.htm

    You may want to contact this person and
    ask if he feels guttation only involves the
    hydathodes or can also involve trichomes.

    http://www.botany.ubc.ca/people/french.htm

    Jim
     
  3. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    Hi, Jim. This is my feeling as well especially because the liquid is more sap than water. Google searches revealed two other possible explanations for what I'm seeing: 1) The sap is extrafloral nectar exuded by the plant, perhaps to attract ants in the wild in some sort of symbiotic relationship. However I do not see any specialized plant organs (e.g. nectaries); and 2) The plant is ridding itself of excess sugar.

    I'm hoping someone can tell me what this process is without getting too technical - it would be too much for this amateur's brain.
     
  4. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    FWIW, a tiny drop of sap can also be found underneath the leaf tips of my olive tree.
     
  5. mr.shep

    mr.shep Well-Known Member 10 Years of Activity

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    It may be better to have someone come in and be overly
    technical and then I can try to explain things in more
    simple terms. Sometimes people take an experimental
    process by someone else and run with it to use as a basis
    to conduct their own experiments on a particular plant,
    a family of plants or a wide range of unrelated plants.

    I think we have to take a look at what is going on with
    a specific plant on a plant by plant basis. With some
    plants seeing sap or ooze can be a natural phenomena
    and it can mean there is something wrong with the
    plant in that the plant sometimes is trying to slough
    off solutes, in this case, due to a chemical imbalance
    in its system. The process of guttation has been used
    as a means to test for pesticide residues in plants for
    just the above reason.

    Oils, resins, salts, sugars, minerals can be transpired
    to the surface of the plant by a variety of means. Some
    natural and some are not so natural in the case of a
    Pine oozing sap due to an injury caused by an insect,
    usually a boring insect. Even Citrus have oil cavities
    in their petioles to store essential oils needed for the
    plant. What happens when there is too much of this
    oil, too much to be stored and later used by the plant?
    The plant may try to slough off the excess oil and to
    do that means the plant has to force it out externally
    somewhere.

    No matter how we look at it, guttation as a subject
    is going to be technical. I am too far removed from
    Plant Anatomy and I am not a Botanist either to give
    the whole process a decent layman's view on it until
    someone gives me something to work with that I can
    relate to such as applying the term for a plant that I
    know well enough.

    I am not so sure that guttation is not being used as an
    all encompasing term for other processes going on in
    a plant in that even functions of the idioblasts may now
    be considered guttation by some people. I do know
    that in my fields of plant science that when we see
    water droplets emitted from a stem we felt that what
    we were seeing was not natural in many cases. Some
    plants will exude these droplets when they have been
    exposed to higher than wanted pesticide levels in the
    plant, even at times when the plant is telling us we
    gave it too much fertilizer (Grapes can do this). I
    believe some plants will emit water on the leaves, to
    ward off heat to try to prevent injury to the leaves.
    Then again some plants can use the exudations from
    the nectaries to intice a specific insect needed for
    pollination. Some carnivorous plants, I think off
    hand, a Venus Flytrap can emit nectar in order to
    entice an insect to come in and be trapped.

    I'll read up on the plant you mentioned Aglaia odorata
    and see what I can come up with a little later.

    Jim
     
  6. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    Thanks, Jim. I have not been able to find much information on this plant. The best source so far has been the book A Taxonomic Monograph of the Genus Aglaia by C.M. Pannell. I don't recall reading anything about this condition but then it was not on my mind at that time.
     
  7. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    The sap probably goes unnoticed in plants in the wild. I gave the plant a shower and all the sap was washed away.
     
  8. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    A review of Pannell's book reinforces the ant theory. They were specifically noted in a section on insects and Aglaia. "...ants are frequently found on all parts of the tree...A. elliptica have glands along the petiole, which secreted a sugary liquid. The function of these glands is unknown, but it may be that a young tree thereby attracts ants..."

    I guess it's safe to conclude the plant's exudation of this liquid is normal. I wonder if there is a term to describe it; 'extrafloral nectar' is a closer fit than 'guttation'.
     
  9. mr.shep

    mr.shep Well-Known Member 10 Years of Activity

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    Junglekeeper, can you post a photo of your plant?

    Sugars from the flowers are probably originating
    from the floral nectaries. A sugar containing liquid
    found on other vegetative parts such as stems and
    leaves and I am assuming the petioles also are from
    the extrafloral nectaries.

    I believe Meliaceae have secretory cells that have
    a resinous content found on the leaves, possibly
    due to secreting idioblasts. Droplets found on the
    hairs on the leaves are probably as a result of the
    trichomes.

    There may be some scent given off by the droplets
    that you described. From what little I've been able
    to learn of this plant there are a few aromatic
    compounds that have been isolated from this plant
    and not all of them came from the flowers either.

    Jim
     
  10. Junglekeeper

    Junglekeeper Rising Contributor 10 Years of Activity

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    Let me work on that.
     

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