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  #1  
Old September 14th, 2005, 03:45 PM
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Junglekeeper Junglekeeper is offline
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Guttation?

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.
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  #2  
Old September 16th, 2005, 07:27 AM
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mr.shep mr.shep is offline
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Re: Guttation?

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
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  #3  
Old September 16th, 2005, 04:23 PM
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Re: Guttation?

Quote:
Originally Posted by mr.shep
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.
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.
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Old September 16th, 2005, 06:45 PM
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Re: Guttation?

FWIW, a tiny drop of sap can also be found underneath the leaf tips of my olive tree.
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Old September 17th, 2005, 08:53 AM
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mr.shep mr.shep is offline
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Re: Guttation?

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
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  #6  
Old September 17th, 2005, 12:02 PM
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Re: Guttation?

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.
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  #7  
Old September 21st, 2005, 03:56 PM
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Re: Guttation?

The sap probably goes unnoticed in plants in the wild. I gave the plant a shower and all the sap was washed away.
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  #8  
Old September 23rd, 2005, 03:01 PM
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Re: Guttation?

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'.
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Old October 1st, 2005, 08:03 AM
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Re: Guttation?

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
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  #10  
Old October 1st, 2005, 04:52 PM
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Re: Guttation?

Quote:
Originally Posted by mr.shep
can you post a photo of your plant?
Let me work on that.
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