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Amorphophallus flower anatomy

May 28, 2010

As I wrote yesterday, it is time to look out for the Amorphophallus paeoniifolius flowers now in the early rainy season. But what are you really looking at?

Spathe. From a distance, you see the speckled outside of the sheath. In the Arum family (Araceae), such sheaths are called spathes. The inside of the spathe is reddish brown, like raw meat. The spathe is a bract, which is a leaf supporting the flowers.

Spadix. The spathe surrounds the flower spike, the inflorescence, which can be called spadix. The spadix has female flowers in the bottom. They contain no petals or sepals, just pistils. They are only active for one day. Once they have been pollinated, the male flowers open (the middle section of the spadix). They are composed of stamens, no petals or sepals are present. On top of the spadix, there is a twisted morel-like knob, called “appendix”. It is composed of sterile flowers.

Pollination. Insects are attracted to the carrion-like odours and colours, and if they do not go inside (this is what the plant wants), they will slip on the glossy surface of the knob or the spathe, and fall to the bottom. When climbing upwards, and if they have visited another flower before, they will pollinate the female flowers. The next day, the female flowers are no longer receptive, but busy with fruit formation. The male flowers have opened now. The insects will crawl over the male flowers, whose sticky pollen attach to the insects. When the insect finds a new flower, the circle starts again.

By keeping male and female flowers active different days, self-pollination is avoided. This is wise, as generally, cross-breeding resulting in genetical diversity, usually increases the chances for survival of at least some members of the next generation. Cloning, practiced by e.g. dandelions and aphids, is only sufficient in a stable situation.

The green leaves, which indeed resemble those of paeonias, emerge later. Their purpose is to make carbohydrates for next year’s blossom. The carbohydrates are stored in the underground tuber.

Eric Danell

Spadix morphology of Amorphophallus paeoniifolius:

Bottom: female flowers, Mid-section: male flowers, Top section: Slippery appendix.

The spadix is wrapped by the spathe, a flower-supporting leaf (bract). Its function is to funnel the pollinating insects.

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