Apomictic Production of Fertile Seed in Arisaema - S. Wills, J. McClements, et al.

[George R Stilwell, Jr.]

Does anyone know, please, whether Arisaema sikokianum is monoecious,
dioecious or paradioecious?    We have a group of three flowering in the
garden, about 2 ft 6 inches high, which form seed heads but the berries
do
not swell, presumably because they have not been fertilised.   Do I need
to
introduce another, younger, tuber, which would presumably be male, or
look
for a male plant, or get busy with a small brush in spring?

I have been loath to attempt the latter because the flowers make a
striking
*accent* group, but I would dearly like to get some seed.

Simon Wills,  Clevedon UK  zone 9


Simon

I believe that Arisaema sikokianum is always dioecious, either completely
male or female, but is also "paradioecious", changing from male to female
as
the plant matures, and occasionally reverting to male if times are hard!

Guy Gusman believes that young female plants, with or without
pollination,
may produce INFERTILE seed, which explains what you have described, where
fruits are formed which start to develop but then fall over. The berries
do
often contain what appear to be rudimentary seed.

The recent discussion on Aroid-L as to whether apomictic production of
FERTILE seed can occur in Arisaema has yet to be completely resolved, but
Peter Boyce, Guy Gusman and Sue Thompson do not know of anything in the
literature which would confirm such goings-on, despite the fact the the
process can and does occur in other Araceae.

Stay tuned.

Jim McClements

I am happy to finally see some more input on this subject. When I tried
twice
to get something started last month, it was disappointing not to hear
from
some of the experts that I know are out there.

Diane's experience with A. flavum is probably due to the fact that it is
one
of the few species of Arisaema that are usually monoecious and therefore
self-fertile. A. tortuosum is another one, and other species may go
through a
bisexual phase during the transition from male to female.

Guy's observations are exactly what I was hoping to hear. He grows twice
as
many species of Arisaema as the rest of us put together, and if he hasn't
seen FERTILE seed produced by a female plant as yet, it must be rare, if
it
happens at all.

Guy's observation may also at least partly explain why we sometimes
receive
what appears to be perfectly healthy seed from a friend, exchange or
dealer
which fails to germinate, when most Arisaema seed usually germinates
easily
and readily.

I hope that Peter Boyce will find time to address this subject. It would
seem
that if true apomictic seed production does occur in Arisaemas, someone
would
have recorded the observation previously.

Personally, I would find further discussion of this subject much more
interesting that repeated postings about when the latest IAS newsletter
had
arrived!

Jim McClements

Dear Jim

I have no experience with apomixis in Araceae and am not aware of any
papers
dealing with it in Arisaema. However, what IS common in the Araceae (and
contrary to the often quoted 'strictly protogynous') is self pollination.
Here
at Kew the following species regularly (in some instances ALWAYS) set
viable
seed from a solitary inflorescence.

Anthurium bellum, salviniae, scandens

Arum alpinum, balansae, cyrenaicum, hygrophilum, idaeum, purpureospathum

Arisaema erubescens (syn. consanguineum), flavum

Biarum bovei ssp. crispulum, kotschyi

Epipremnum pinnatum

Pinellia pedatisecta

Stenospermation ulei


Peter Boyce