Lemnaceae - Images of Lemna valdiviana

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Lemna valdiviana

Dorsal view showing several clonal clusters of transparent-green plants.

Lemna valdiviana

Dorsal view of clonal clusters of 7 transparent plants showing prominent single vein along midline.

The plant bodies (fronds) of Lemna valdiviana are often connected in clusters of four to seven, and the nerve (vein) typically extends 3/4 of the distance from the node (point of root attachment) to the apex. The closely related L. minuta has one faint nerve that only extends about 1/2 the distance from the node to the apex. When growing in full sunlight, plant bodies of L. minuta are often only 2 mm long and are connected clusters of two. One of the most difficult duckweeds to identify in the field is the growth form of Lemna minuta found in shady habitats. The plant bodies are often connected in clonal clusters of four and are slightly longer than typical L. minuta growing in full sunlight. The shade form of L. minuta can be separated from L. valdiviana by the extent of the nerve. The obscure nerve of L. minuta only extends about 1/2 the distance from the node to apex.

Dorsal view of Lemna valdiviana, showing extent of nerve (vein) in relation to node (point of root attachment) and apex of plant body. The single nerve extends beyond the midpoint to about 3/4 of the distance between the node and apex. In addition, the thin plant bodies are transparent green and connected in a clonal cluster of five. These characteristics rule out L. minuta, at least the typical form that grows in full sunlight.

Dorsal view of Lemna validiviana, showing extent of nerve (vein) in relation to node (point of root attachment) and apex of plant body. The single nerve extends beyond the midpoint to about 3/4 of the distance between the node and apex. The nerve clearly extends beyond the region of air spaces (aerenchyma tissue). These characteristics rule out L. minuta, at least the typical form that grows in full sunlight. In L. minuta, the nerve rarely extends beyond the aerenchyma tissue and only extends about half the distance from the node to apex. These may seem like relatively minor morphological differences, but DNA sequencing studies clearly separate these two closely-related species.

Three duckweeds from Pinnacles National Monument in central California. A. Lemna minor: Three veins arising from point of root attachment (n), without dorsal row of papules and reddish anthocyanin on ventral side (as in L. turionifera) and without winged root sheath (as in L. aequinoctialis). B. Lemna valdiviana: One faint vein extending more than 3/4 distance from root node (n) to apex (red arrow), plant body very thin and transparent throughout and floating on or just below water surface (slipping under plant bodies of L. minor and L. minuta in an observation dish). C. Lemna minuta: One vein extending less than 2/3 distance from root node (n) to apex, vein not extending beyond region of larger air spaces (red arrow), plant body slightly thicker in middle (not as uniformly thin and transparent as L. valdiviana), small size (only 1-2 mm long) or larger when growing in shade, floating on water surface (not submersed as in L.valdiviana). Photo taken with substage illumination.

Lemna valdiviana from Coyote Creek in the Anza-Borrego Desert. Ventral view showing a single vein that extends 3/4 of the distance between the node (point of root attachment) and apex of the plant body. According to Landolt, this is one of the most reliable characteristics to separate it from L. minuta because of the variability of these two species under different growing conditions.

Lemna valdiviana from Coyote Creek in the Anza-Borrego Desert. There is little doubt that the single vein extends 3/4 of the distance between the node (point of root attachment) and apex of the plant body.

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