Aphelandra and the big sex cell

Blooming now at the edge of a “tangled bank” of growth alongside our seasonal stream is an Aphelandra species, relative to the zebra plant, A. squarrosa.

It is a shrub with a candle-like flower-head or inflorescence. You can see in the next image its green bracts, which are tinged with yellow and orange, and its tubular, fuzzy, scarlet flowers.

The name, Aphelandra, comes from the Greek apheles, meaning simple, and andra, meaning male. The name could mean “sleek anther,” but it refers to the fact that the anther (the male, pollen-producing portion of the flower) consists of a single cell.

I’ll get back to that anther in a moment.

First, to continue the description.

Aphelandra is a genus in the family Acanthaceae, which consists of mostly tropical herbs, shrubs, or twining vines. The leaves are simple and opposite, with each pair of leaves at right angles to the pair below.

The flowers are usually arranged in an inflorescence which may be, like Aphelandra, a spike. The petals are usually tubular, and the fruit is a two-celled capsule which bursts open somewhat explosively.

The genus Aphelandra has 4 stamens; conspicuous and tightly overlapping bracts, and two-petaled flowers which are hummingbird pollinated. In the image below you can see glands on the bracts. These are extrafloral nectaries, which attract ants. The ants in turn protect the inflorescence and fruit.

This plant fits the description of Aphelandra scabra (as described in A Guide to the Tropical Plants of Costa Rica) except for one detail: the edges of the blades of A. scabra continue down the stems of the plant, according to the author.

I see no evidence of this characteristic in the plant at hand (see image of leaves). Neither can I see this characteristic in the image of A. scabra at the Smithsonian’s Trees, Shrubs, and Plants of Panama web site, so it’s most likely I’ve misinterpreted the author’s words. Nevertheless, I’ve been burned too often trying to apply a species name with insufficient data, so for now this Aphelandra shall remain Aphelandra sp.

Now for that big sex cell, the single-celled anther. Here’s one of the scarlet flowers, with the tip of its two tightly furled petals pulled off. The 4 stamens and slender stigma (barely visible) are tucked inside.

And here are the dissected parts of the flower. The stamens occur in pairs. One pair has been pulled apart. The other pair is wrapped around that slender stigma.

As a reminder, a stamen consists of the pollen-producing anther and a filament. The anther is that thick part at the end of the filament.

To understand why having an anther consisting of only one cell is amazing enough to name the genus after the feature, here’s a thumbnail image

and a link to an electron micrograph of a typical mature anther and its pollen, from the University of Sussex Centre for Advanced Microscopy. There are countless cells in this anther!

If you do a Google image search for “anther,” you’ll find many more microscopic images of anthers, clearly delineating their many, many cells.

So far I’ve been unable to discover any discussion of Aphelandra’s anthers, what are the implications of this uniqueness, or how many pollen grains a single cell can produce. It would be fascinating to learn.