BEN # 145

Adolf Ceska aceska at CUE.BC.CA
Thu Oct 3 10:34:09 EST 1996


                                                   
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BBBBB    EEEEE    NN N N             BOTANICAL
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No. 145                              October 3, 1996

aceska at freenet.victoria.bc.ca        Victoria, B.C.
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 Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
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DR. TADEUS REICHSTEIN (1897-1996)
From: Mary Gibby <M.Gibby at nhm.ac.uk>

Tadeus  Reichstein  was  born on 20th July 1897 in Wloclawek, at
that time in Russian Poland. The family moved to Switzerland  in
1906.  During  the  1920s  he  worked  on  the  isolation of the
volatile constituents of the flavour of roasted coffee,  and  in
the  1930s he developed a method for the commercial synthesis of
Vitamin C. For his work on  adrenal  cortical  hormones  he  was
awarded  the  Nobel  Prize  for Medicine and Physiology in 1950,
together with E.C. Kendall and Philippe Hench. Since being  made
Emeritus Professor in 1967 he has worked full-time on ferns. His
interests were wide-ranging and global. He was in correspondence
with  pteridologists  from many parts of the world. His fascina-
tion was for polyploid fern complexes, but  he  also  has  spent
many  years  working  on the pteridophytes for Flora Iranica. He
continued to use his  expertise  in  organic  chemistry  in  the
investigation  of phloroglucinols in Dryopteris. In all his fern
work he was a great collaborator, and practically all  his  fern
papers  have  been  multi-authored.  An exception is a favourite
subject, his 1981 paper on  "Hybrids  in  European  Aspleniaceae
(Pteridophyta)", Bot. Helv. 91: 89-139.

He died on 1st August 1996 at the age of 99.


MYCORRHIZAL LANDSCAPES (BOTANY BC LECTURE)
From: "Hugues B. Massicotte" <hugues at unbc.edu>

The  botanical landscape can be seen as a mycorrhizal landscape,
a landscape where the roots of most plant species form  interac-
tive  and  beneficial partners with a variety of fungal species.
In my talk I explored the astonishing structural complexity  and
hinted  at  the  ecological  significance of a variety of mycor-
rhizal symbioses found in B.C. and, indeed, worldwide. With  the
aid of a variety of microscopy techniques and numerous floristic
examples, I explored and compared the significant features which
make  vesicular-arbuscular,  ecto-,  ectendo-, arbutoid, ericoid, 
monotropoid and orchid mycorrhizae.

Fungi involved in mycorrhizal  relationships  range  from  being
very  specific to their host (usually one plant genus), to being
generalists, associating with an immense array of hosts, perhaps
a clue to their numerous ecological contributions.

For example, several important genera of trees in B.C., such  as
Pinus,  Picea,  Pseudotsuga,  but  also  smaller plants, such as
Dryas and Kobresia, form ectomycorrhizae with  their  respective
fungal  symbionts (mostly basidiomycetes and ascomycetes). These
ectomycorrhizae have a  Hartig  net  (the  functional  interface
between the fungus and the root cell) where presumably exchanges
of metabolites take place, and a fungal sheath (or mantle) which
surrounds   the  root  and  interfaces  with  the  soil  matrix,
facilitating the uptake of nutrients and  water  by  the  plant.
Worldwide,  it is estimated that over 5000 species of ectomycor-
rhizal fungi has been described.

Ectendomycorrhizae, monotropoid and arbutoid mycorrhizae, repre-
sent variations in some aspects of  the  ectomycorrhizal  theme!
Like ectomycorrhizae, ectendomycorrhizae have a Hartig net and a
mantle,  but  also  have intracellular coils, fungal hyphae that
exist inside the root  cells.  The  functional  significance  of
these  coils  is  unclear  (after  all,  a Hartig net is already
present). However, species, such as the genus  Wilcoxina,  is  a
fungus presumably involved worldwide with pine species. Arbutoid
mycorrhizae  are  very  similar  to ectendo structurally, except
that all fungal structures are restricted to the outer layer  of
root epidermal cells, as in other ericaceous plants (see below).
The  fungi  involved  with arbutoid plants are the same as those
forming ectomycorrhizae, a phenomenon that  could  theoretically
open  the doors for "linkages" between hosts involved in these 2
classes. Demonstration of these ecological linkages will  occupy
the researcher well into the 21st century!

In the case of vesicular-arbuscular (VA) mycorrhizae,  found  on
hundred  of  species  in  B.C., (from herbs to woody perennials,
Liliaceae, Rosaceae, Asteraceae, Juglandaceae to name a  few)  ,
it  is  the  "haustoria-like" arbuscule (i.e. a tree-like fungal
structure), which develop within root cells,  that  act  as  the
functional  interface  for  exchange  between  the plant and the
fungus.  The  vesicles  (i.e.  intracellular  flask-like  fungal
structures)  act  as the "warehouses" where the fungus can store
lipids. The fungi involved in VA relationships are not  diverse,
perhaps  200  species worldwide, and exhibit low specificity for
their hosts in general...one fungus can interact  with  most  VA
hosts.  To  date, no one has succeeded in growing these VA fungi
in pure culture, emphasizing the obligate nature of  these  sym-
biotic fungi.

The ericoid mycorrhizae involve numerous ericaceous hosts (Gaul-
theria,  Rhododendron,  Vaccinium,  Calluna, etc.) and usually a
"select" group of septate ascomycete fungi. They  appear  to  be
broad  host ranging among ericaceous hosts but are restricted to
them. Ericaceous host roots  are  very  minute  and  the  fungus
usually  interacts with the root epidermis, forming coils within
each colonized cell. The mutual transfer of metabolites  happens
there!

The   most   curious  mycorrhizae,  which  has  intrigued  plant
physiologists for decades, involve monotropoid hosts (Monotropa,
Pterospora, etc.) and possibly a subset of the  vast  ectomycor-
rhizal  fungi  pool.  These  plants are heterotrophic, obtaining
carbohydrates from other sources, therefore it is hard to under-
stand how fungi benefit by forming mycorrhiza with these plants.
It seems the fungi are involved in a tripartite  "contract",  in
which  they  first  derive carbohydrates from a true autotrophic
host (typically Picea, Pinus, etc.) and then  transfer  some  to
the monotropoid plant, apparently an "altruistic" transfer?!. It
is  unclear  what  the  fungus  gets  in  return but speculation
abounds!

The  last  intriguing  class,  the  orchid mycorrhizae, are even
lesser known. With  a  worldwide  diversity  of  orchid  species
exceeding   the  20  thousands,  and  with  a  select  group  of
basidiomycetes interacting with orchid tissues,  either  at  the
time of seed germination or at the time of symbiotic root forma-
tion,  we  find  ourselves  in the infancy of orchid mycorrhizae
research! Here too, fungal coils invading cells are the presumed
site of metabolite exchanges.

Our understanding of these complex mutualistic  associations  is
still  limited when one considers the vast undescribed diversity
of fungi actually inhabiting the soil with  their  plant  hosts!
The living soil is truly one of our last frontiers...

   Dr. Hugues B. Massicotte
   University of Northern British Columbia
   Prince George, B.C.
   Canada
   
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