POSLUSZNY, USHER1* and P. BARRY TOMLINSON2. 1Department of Botany, University of Guelph, Guelph, Ontario, Canada, N1G 2W1; 2Harvard Forest, Harvard University, Petersham MA 01366, National Tropical Botanical Garden, Kalaheo HI 96741. - Early floral development in Amborella trichopoda Baill.
Amborella, a monotypic genus native to New Caledonia, has
received much attention recently because of its proposed status as the
basalmost clade of the angiosperms. The seemingly unisexual flowers of
this small and little known shrub have only recently been studied to
any great extent. To date, the documentation of the early stages of
floral development has proven to be an extremely difficult nut to
crack. There are two reason for this: 1) is the scarcity of material,
especially in the appropriate stages of development, and 2) the near
impossibility of dissecting the tiny floral buds. Not only are the
floral buds small and fragile, but also the young primordia are so
tightly packed that stages of initiation and early development are
totally obscured by the older primordia. An opportunity to look at
early floral development arose recently when the second author was
able to collect young flowering shoots from male and female plants of
Amborella trichopoda at the National Tropical Botanical Garden
in Kauai, Hawaii. Although difficult to dissect, the initial stages in
floral development clearly show a cup-like depression in the floral
meristem and the initiation of primordia on the inner wall of the
upgrowth in a tight spiral pattern. Very little of the floral meristem
survives and earlier reports of possible female remnants in male
flowers are rare. The early development of the carpel primordia is
particularly intriguing since there are no signs of either
horseshoe-like or peltate primordial development that is common to
other presumptive early angiosperm flowers. The consequences of these
observations will be discussed.
Key words: Amborella trichopoda, basalmost angiosperm, carpel, development, floral, meristem