Well Steve,
I must admit, that since I am leaving the University, and no longer
teaching or making captive audiences listen to my drabble on this stuff,
and I don't know when I will get to lecture or present next... I took
advantage of this forum to talk about the stuff that really excites me
;-).
I was not trying to substitute secretory for excretory... I was just
trying to toot my own horn ;-). However, I do have another comment on
the subject. To simplify things a bit in a macro kind of way, we
know that plants do utilize their leaves as "excretory" structures in a
sense (I use the word loosely, for the definition of excretory, at least in
botany, is the elimination of waste from the cells). We all know, that
accumulated wastes are frequently deposited and stored within the leaves,
and then lost or "dumped" during defoliation. Don't get me going here
guys... do you really want me to go to the "cellular" level on this? I
think you all have hashed this out pretty well already.
Ugh... not quite awake yet... need coffee... look forward to future
discourse!
Steffi
******************************************************************
Stefanie Galgon lab/message: (520) 523-7735
Department of Biology
Northern Arizona University smg4 at dana.ucc.nau.edu
"Life is a banquet, and most poor suckers are starving to death"
Auntie Mame
******************************************************************
On Tue, 13 Jul 1999, Steve Hinkson wrote:
> You did go on ! LOL But you missed the querry, Stefanie. The question posed was
> not how to plants distribute their defensive toxins, but excrete substances that
> are toxic to their own tissues.
> "The subcuticular cavity of mature peltate glandular trichomes house
> accumulated monoterpenes and other compounds". Yes, they do, but those compounds
> are produced by the plant, and are defensive, not excretory.
>> "GT's have a unicellular or multicellular head composed of
> secretory cells, usually sitting on top of a stalk of nonglandular cells.
> Essentially, capitate glandular trichomes consist of a unicellular or
> multicellular stalk and a unicellular or bicellular head. Peltate consist
> of a basal cell located within the epidermis and a single stalk cell
> subtending a head composed of encapsulated secretory cells."
> Got a kink reading that! That was botany I'm quite sure, if I ever knew, I only
> knew up to the exam. Is your implication that glandular trichomes are excretory,
> such as a kidney, or that they detoxify as does the liver?
> *wink*
> Steve
>> Stefanie Galgon wrote:
>> > Oooh... now we have tangented to the topic of secondary plant
> > metabolites! I love this stuff. Nobody has mentioned glandular
> > trichomes!!! Trichomes are epidermal outgrowths that can be found on all
> > plant organs. They vary in size and complexity, and include hairs,
> > scales, and other structures. Secondary metabolites are classified into
> > three main groups: phenolics, nitrogen containing compounds (e.g.
> > alkaloids), and terpenes. Secondary compounds (some toxic to animals, some
> > inhibit seed germination -- the allelopathy David brought up), tend to be
> > biosynthesized and localized in secretory structures at the surface of a
> > plant (primarily on the leaves). The foremost secretory organs of plants
> > in some families are glandular trichomes (may I be so bold as to make that
> > statement?), which are found on the abaxial and adaxial surface of the
> > leaves, varying greatly in structure between and within species (you'll
> > see many descriptions... capitate stalked and sessile, peltate).
> > GT's have a unicellular or multicellular head composed of
> > secretory cells, usually sitting on top of a stalk of nonglandular cells.
> > Essentially, capitate glandular trichomes consist of a unicellular or
> > multicellular stalk and a unicellular or bicellular head. Peltate consist
> > of a basal cell located within the epidermis and a single stalk cell
> > subtending a head composed of encapsulated secretory cells. My point is,
> > the subcuticular cavity of mature peltate glandular trichomes house
> > accumulated monoterpenes and other compounds (biosynthesized within the
> > plastids of the secretory cells, and transported to the subcuticular
> > cavity). If something munches on the leaves, the capsule ruptures and the
> > compounds are released. Let us say a deer decides to munch on some
> > Dugaldia... if the quantity of a particular toxic monoterpene is high
> > enough within the GT's, that deer will become ill. Various plants in the
> > Lamiaceae family have been investigated for toxic and deterrent effects
> > against insects. Extracts from Dracocephalum moldavica, Lavendula
> > angustifolia, Salvia plebilia, and S. sclarea have shown toxic effects on
> > the cotton aphid (McIndoo 1983), from Hyptis suavelobens had toxic effects
> > on Lipaphis erysimi when tested on cabbage leaf (Roy and Pande 1991), and
> > from Elsholtzia iriostachya retarded insect growth, including pupal
> > formation and adult emergence (Bhattacharya and Bordolsi 1986). The
> > leaves of some Artemisia species house compounds that inhibit seed
> > germination of other plants (but not their own!). The leaves are dropped,
> > the compounds leech into the soil....
> >
> > Boy, I sure am rambling here, aren't I? Did I just steer wayyyy off the
> > subject at hand? Anyone else?
> >
> > Steffi
> >
> > ******************************************************************
> > Stefanie Galgon lab/message: (520) 523-7735
> > Department of Biology
> > Northern Arizona University smg4 at dana.ucc.nau.edu> >
> > "Life is a banquet, and most poor suckers are starving to death"
> > Auntie Mame
> > ******************************************************************
> >
> > On Sat, 10 Jul 1999, David Hershey wrote:
> >
> > > If plants do produce organic compounds that are toxic, either as
> > > unintended byproducts or as allelochemicals (those used to inhibit
> > > growth of other plants) they may store them in vacuoles where they will
> > > not cause damage. Besides shedding of plant parts, woody species could
> > > possibly store waste materials in old, nonfunctional xylem although I do
> > > not know if there has been research on that.
> > >
> > > David Hershey
> > > dh321 at excite.com> > >
> > > Bill Williams wrote:
> > > >
> > > > I would love to hear a definitive answer to this question; my
> > > > introductory-biology students ask similar questions frequently. Here's my
> > > > answer:
> > > >
> > > > Toxic metabolic products arise because the food that organisms consume
> > > > doesn't precisely match the organisms' needs. Urea is an excellent
> > > > example: heterotrophs necessarily consume complete organisms, or at least
> > > > complete cells, but the ratio of calories to nitrogen *in* organisms is
> > > > much, much lower than the ratio of calories to nitrogen *needed* in food.
> > > > Thus, they have a constant excess-nitrogen problem and excrete urea (or
> > > > uric acid, or ammonia, or some other nitrogenous waste). But the world of
> > > > autotrophs is completely different: they obtain energy from the sun (which
> > > > creates is own problems and gives rise to numerous metabolic pathways for
> > > > dissipating excess energy) and materials from the air and soil solution.
> > > > In general, such organisms simply don't take in materials that they don't
> > > > need, or at least that they cannot use without poisoning themselves.
> > > >
> > > > So: if you don't want to bother with kidneys and livers, don't eat!
> > > >
> > > > -W2
> > > >
> > > > At 08:54 -0700 7/9/99, Santosh Baburao Mane wrote:
> > > > > I am pharmacy student , we study about plants ,and use of plant as
> > > > >sources of drugs
> > > > >
> > > > > So my question is," why plants are able to survive with out excretory
> > > > >system that is kidney or liver
> > > > >like organs ???" They do not need detoxification ?? why metabolic products
> > > > >are not able to give toxicity
> > > > >to plant and why they induced toxicity to animal cells only .
> > > > > plants cells having any mechanism for detoxification or is it
> > > > >natural???
> > > > >
> > > > >So pl help me to finding out answer of this
> > > > >
> > > > >
> > > > >pl mail me ans.
> > > > >
> > > > >Thanks
> > > > >Santosh
> > > > >San_dha at giaspna.vsnl.net.in> > > >
> > > > ________________________
> > > > William E. Williams
> > > > Biology Department
> > > > Saint Mary's College of Maryland
> > > > 18952 E. Fisher Rd.
> > > > Saint Mary's City, MD 20686-3001
> > > > (301)862-0365
> > > >
> > > > Summer: Botany Department
> > > > Aven Nelson Building
> > > > University of Wyoming
> > > > PO Box 3165
> > > > Laramie, WY 82071-3165
> > > > (307)766-6293
> > >
> > >
>>>
