Duckweed Anatomy:
the Structure of Duckweed Fronds 
from the work of Elias Landolt
Details of a Lemna Plant Schematic Diagrams The Air Pockets of Lemna Fronds See inside the plant
  • The anatomy of a plant is shaped by cell walls that give the plant its structural framework.  Studying the framework of the plant will help you understand how it is organized and grows. 
  • The illustrations on this page show details of duckweed anatomy that cannot be seen by casual observation.
  • The first two sections have diagrams illustrating the relationships among the fronds in a typical cluster.  To understand these diagrams it is important to keep in mind that the duckweed plants consists of a cluster of fronds descended from a single mother frond.
  • You can view the hidden framework inside a duckweed plant using a simple chemical treatment. [ Read how. ]

Photo from Landolt, 1986, used with permission.
Click on any image for a magnified view.
Above Right:  Cleared specimen of Landoltia (Spirodela) punctata, stained to reveal the cell walls, photographed from below (ventral view).  A = tissue (prophyllum) covering the point of attachment of the roots, B = root cap.

 

Details of a Lemna plant.

The pattern of asexual reproduction:  As each new frond matures, it initiates the formation new fronds.  Each daughter frond initiates as a bud in the meristematic zone along the center axis of its mother.  It then emerges from the pouch on the side of the mother where it was initiated.  Each new frond is connected to its mother frond by a strip of tissue called a stipule or stipe.  The stipule elongates as the frond matures.  When the daughter frond reaches full maturity, the stipule breaks off to release a new cluster.  By that time in rapidly-growing duckweeds, the newly-released frond has already initiated new daughters.

Flowers buds are also initiated in the frond meristem, but their formation is not required for unlimited asexual reproduction.
 
 Lemna aequinoctialis Anatomy of Lemna aequinoctialis
Legend

Ap     apex 
B      base 
F0     mother frond 
Fl     daughter frond of the
       first generation 
F2     daughter frond of the
       second generation 
Fl     flower
Ne     nerve 
No     node 
Ov     ovary 
Pa     papule 
Po     pouch 
R      root 
RC root cap 
Sta    stamen

Figure and text from Landolt, E. The family of Lemnaceae - Monographic Study., Vol. 1, Veroff. Geobot. Inst. ETH, Stiftung Rubel, Zurich, 71. Heft (1986) Fig. 2.1.b, p. 15.


Interpretation of the Duckweed Frond:  Schematic Diagrams


Several plant anatomists have tried to interpret the anatomy of the duckweed frond in terms of the anatomy of related higher plants, from which the Lemnaceae probably evolved.  Elias Landolt has provided the most convincing recent interpretation.
 
Landolt's interpretation of Spirodela
Landolt's interpretation of Wolfiella
Landolt's interpretation of Wolffia
Legend:  left, Spirodela, center, Wolffiella, right, Wolffia.

The Lemna frond is organized very similarly to Spirodela, but there is no prophyllum at the base of the frond (the prophyllum at the base of the flower is present in Lemna).
F0     mother frond
F    daughter frond of the first generation
F    daughter frond on the second generation
a      first frond
b      second frond (accessory frond to a)
c      third frond  (accessory frond to b)
+      plus side
-      minus side
Fl     flower
L      leaf-like body
No     node
P      prophyllum
Po     pouch
Sti    stipe

Figures and text from Landolt, E. The family of Lemnaceae - Monographic Study., see above (1986) Fig. 2.10, p. 25.


 

The Air Pockets of Fronds in Lemna gibba:  How Duckweeds Float.


The air pockets (aerenchyma) of duckweeds provide buoyancy, much like the air spaces in a rubber raft.
 
Swollen (gibbous) fronds photographed from below.
Cross-sectional view of to show the air spaces (aerenchyma).
AS = air space, CL = layers of cells surrounding aerenchyma, LN = lateral nerve, MN = median nerve.
Figures and text from Landolt, E. The family of Lemnaceae - Monographic Study., see above (1986) Figs. 2.26 (left) and 2.25 , p. 55.



 

Glossary

aerenchyma A an air pocket in the duckweed frond lined with a smooth layer of cells.  The aerenchyma are present in vegetative fronds but absent in turions.
asexual reproduction Frond multiplication by budding of daughter fronds without flowering and fertilization of the ovary by pollen.
meristematic zone A site within the plant where an organized structure of dividing cells is located.
nerve Nerves are vascular tissue.  The consist of elongated cells that branch off from the node and run nearly to the tips of the fronds. Tracheary elements are found in the nerves and in roots.
prophyllum In Spirodela and Landoltia, a two-part scale of tissue covering the base of the frond.  It is alsothe point of attachment of the roots.
stipule A thread of tissue that connects daughter fronds to the pouch of the mother frond

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Revised:  December 20, 2005