Whether Lemnoids have a single flower or a composed
inflorescence cannot be determined at this point.
Traditionally “Lemnaceae” have been interpreted as
having an inflorescence. I emphasize here ”interpretation”, and the
extremely reduced Wolffia is not the right starting point for a comparison with
One reason for the inflorescence interpretation is the un-equal
development of stamens in Lemna and Spirodela: Stamen-carpel-Stamen. This
sequence is unusual for flowers, where the organs of one identity tend to develop
together, but not unusual for inflorescences, if each organ (or a group of not
more than two) is considered a strongly reduced flower. The other reason is
just tradition – or burden – from the past, when Lemoids were
compared with Pistia (which is now rejected, see below).
1) Blurred Distinction:
Buzgo & Endress (2000) and Buzgo (2001) described that
strong unidirectional development of flowers can lead to a mixed up sequence of
flower organ development; particularly in reduced inflorescences. Buzgo et al
(2006) described that the distinction of meristem identity of flower and
inflorescence can be blurred in reduced flowers, and the debate whether reduced
structures represent a flower or inflorescence is not serving anybody.
2) Phylogeny and Ancestral Character States:
Looking at the molecular phylogeny of Araceae (Cabrera et al.
2008), we see that the Lemnoideae clade inserts at the second node of the grade
of basal Araceae, between the basal most node to the sister clade with
Orontioideae and Gymnostachys, and the third node to Pothoideae (+Anthurium)
and Monsteroideae. That is, Lemnoideae are “surrounded” by clades
with bisexual and pethal-bearing flowers! It is plausible that the ancestor
of all Lemnoideae also had bisexual, petal-bearing flowers. It is not
necessary (not parsimonious) to assume that the structures in Lemanoideae
represent several distinct flowers.
3) The Pistia Legacy
The reason for sticking with the interpretation of Lemnoid
reproductive structures as inflorescence is a legacy or burden from the past,
when Pistia was often proposed to be related to Lemnoids (Engler, Stockey et al.
1997). This relation of Pistia to Lemnoids has been rejected now several times
(rev. Cabrera et al. 2008; also Renner et al. 2004), and no longer bears
significance for the interpretation of the flower in Lemnoids. Just drop
As a conclusion, the structure may well represent a single flower,
possibly as the result of a strongly reduced inflorescence (point 1 above),
with the tubular membrane in some representing a bract (spathe) or a perianth
organ (since it lacks an axillary meristem, “perianth” would be
Below some Literature – I hope this helps.
Matyas Buzgo, PhD
Dept. of Biological Sciences, LSUS
One University Place
Shreveport, LA 71115, USA
(318) 797 5120 office
(318) 797 5222 fax
+ Arber, A. 1919. The vegetative morphology of Pistia and the
Lemnaceae. Proc. Roy. Soc. London 91 B: 96-103
+ Bogner, J. 2000. Friedrich Hegelmaier (1833-1906) and the
Lemnaceae. Aroideana 23: 4-8
+ Buzgo, M. 1994. Inflorescence development of Pistia stratiotes
(Araceae). Bot. Jahrb. Syst. 115 (4): 557-570
+ Buzgo, M., Endress, P.K. 2000. Floral structure and
development of Acoraceae and its systematic relationships with basal
angiosperms. Int. J. Plant Sci. 161 (1): 23-41
+ Buzgo, M. 2001. Flower structure and development of Araceae
compared with alismatids and Acoraceae. Bot. J. Linn. Soc. 136
+ Buzgo, M. Soltis, D.E., Soltis, P.S., Kim, S., Ma, H., Hauser,
B.A., Leebens-Mack, J. Johansen, B. 2006. Perianth development in the
basal monocot Triglochin maritima (Juncaginaceae). - In: Columbus, J.T., Friar,
E.A., Porter, J.M., Prince, L.M., Simpson, M.G. (eds), Monocots: Comparative
Biology and Evolution, (excluding Poales). ALISO 22: 107-125 (Claremont, CA,
USA: Rancho Santa Ana Botanic Garden, ISSN:0065-6275)
+ Cabrera, L.I., Salazar, G.A., Chase, M.W., Mayo S.J., Bogner,
J., Davila, P. 2008 Phylogenetic Relationships of Aroids and Duckweeds
(Araceae) inferred from coding and non-coding plastid DNA. Am. J. Bot. 95 (9):
+ Caldwell, O.W. 1899. On the life-history of Lemna minor. Bot.
Gaz. 27: 37-66
+ Landolt, E. 1980a. Biosystematische Untersuchungen in der
Familie der Wasserlinsen (Lemnaceae). Veröff. Geobot. Inst. ETH
Rübel 70 (1): 5-247
+ Landolt, E. 1980b. Biosystematic investigations in the family
of duckweeds (Lemnaceae), vol2. The family of Lemnaceae - A monographic study.
Veröff. Geobot. Inst. ETH Rübel 71: 7-566
+ Landolt, E. 1986. The family of Lemnaceae - a monographic
study. Vol. 1 of the monograph: Morphology, karyology; ecology; geographic
distribution; systematic position; nomenclature; descriptions. Veröff. Geobot.
Inst. ETH Rübel 71 (2): ??
+ Landolt, E. Kandeler, R. 1987. Biosystematic investigations in
the family of duckweeds (Lemnaceae), vol. 4. The family of Lemnaceae - A
monographic study. Veröff. Geobot. Inst. ETH Rübel 95 (1):
+ Renner, S.S., Zhang, L.-B. 2004. Biogeography
of the Pistia clade (Araceae): Based on chloroplast and mitochondrial DNA
sequences and Bayesian divergence time inference. Syst. Biol. 53 (3): 422-432
+ Stockey, R.A., Hoffman, G.L., Rothwell, G.W. 1997 The fossil
monocot Limnobiophyllum scutatum: Resolving the phylogeny of Lemnaceae. Am. J.
Bot. 84 (3): 355-368