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Old 23-09-2003, 01:42 PM
mel turner
 
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In article ,
wrote...

Do you happen to know why one of them lives inside Ficus carica? It
supposedly fixes extra nitrogen, & in the process makes the tree smell like

you
forgot to clean the cat's litter pan.

I've not heard of this. Are you sure?

That is what I was told by a botany professor.


Okay, but even botany professors may make mistakes. I suspect that
this was just an error.

Where inside the plant are the blue-greens supposed to live?

In the leaves. I used to have a bonsai F. carica. When it was in the house,

the
smell got strong whenever the sun shone directly on the leaves.


Right. F. carica often has strongly-smelling leaves, but I doubt
it's due to any symbiotic organisms living in the leaves.

Cyanobacteria do live symbiotically in various plants [e.g., in some water
ferns (_Azolla_ spp.), in cycad "coralloid roots", inside the stems of
_Gunnera_] and do fix nitrogen, but I've never heard of any such role in Ficus
spp.. A web search and a try with Biological Abstracts both just turned up
nothing.

There are more things in heaven and earth, Horatio, than are met with on the
Web.


Of course. And it might be sad if all interesting biological phenomena
were very well-known and covered by numerous web pages.

But as for the "on the web" bit, BioAbstracts searches the primary
scientific literature. Nothing came up with regard to Ficus leaf
symbionts. On the other hand, other plants with nitrogen-fixing
symbiotic bacteria in the leaves are indeed known, and several
research papers on them did turn up in my search [e.g., some
_Psychotria_ spp. (Rubiaceae) and _Ardisia crenata_ have
nitrogen-fixing symbiotic bacteria living in "leaf nodules" that
may be functionally comparable to the root nodules of legumes,
etc.].

One might reasonably expect that if nitrogen-fixing leaf symbionts
actually existed in an economically-important crop plant such as F.
carica, there would be at least a few recent studies of the system.
There evidently aren't any. [Agricola and a few other databases also
came up dry]

_Ficus carica_ foliage is often noticeably aromatic, either fresh or dried,
but I've never noticed the smell to be at all offensive the way you

describe.

it is definitely an ammonia type smell. I got the same smell from fig trees in
Israel, and I also heard it occurs in Florida. When the tree is growing in the
ground outdoors, it is not that noticeable unless you walk right up to it.


I think we're talking about the same smell, but I suspect that it's
coming from the fig plant itself, not a symbiont. [Oddly, although
most other Ficus don't seem to share the smell, a few other Moraceae
(e.g., the small herbaceous Fatoua) do smell a lot like F. carica]

Perhaps some cats have been doing their business around the fig tree?

On the contrary. At the time I had the fig tree I didn't own a cat. A friend

of
mine compained that her neighbor's cat was "spraying" her fig tree, & had to
laugh when I told her it was the bacteria in the tree.


Or, it's the tree itself.

I gather that actually cyanobacteria are very busy in the higher plants.
This arrangement is not so strange when you stop to consider that F. carica is
the only really cold hardy member of the genus, and apparently the only one
with this symbiotic arrangement.


If the arrangement actually exists, which I seriously doubt.

Probably at some time during the Ice Age, F.
carica hit on this solution to the problem of a shorter growing season and

less
light than its fellow species. Any genus that can come up with an inside-out
inflorescence should have no difficulty capturing a bacterium to further its
own ends.


Such symbioses do indeed occur in other plants [but with no obvious
ice-age connections], but I've found nothing mentioning any in
leaves of F. carica or any other Ficus species.

A couple of nice older monographs of figs and fig culture,
etc. that I just checked:

Eisen, G. 1901. THE FIG; ITS HISTORY, CULTURE AND CURING. U.S. Dept. Agr. Div.
Pomol. Bul. 9, 317 pp.

Condit, Ira J. 1947. The fig. Waltham, Mass., Chronica Botanica Co.

also have no mention of any smelly symbiotic blue-greens in fig
leaves. I think the professor was simply mistaken.

Of course, I could be wrong about this. If anyone knows of
more information on this possible fig leaf symbiosis, I'd be
glad to learn about it.

cheers