Phalaenopsis flower

Flowers differ enormously among flowering plants. A specific structure of the flower is determined by particular ways of sexual reproduction of the plant. Monoicous or dioicous? Self-pollination or cross-fertilization? Abiotic or by pollinators? Which pollinators exactly?… Evolution resulted in really huge variation.

One day I was lazily examining my Phalaenopsis. I was thinking something like: “Lower petal looks like landing for pollinators. Ok, “bee” is here, what is next? Where are male and female parts? An elongated part with something like dragon’s face might be pistil. All moth orchid’s flowers are the same, so there are bisexual, so should be stamen somewhere here. But where?…”.

After guessing quite some time I had to admit that I need Google to solve the puzzle. And Google surprised me: there is no separate male and female parts but the elongated part that I mistook for pistil is actually a fusion of a stamen and a pistil called column or gynostemium. This is a distinctive feature of an orchid family.

Phalaenopsis flower structure
Phalaenopsis flower structure

Orchid’s pollen is not powdery. It held in pellets as solid waxy masses. The masses called pollinia. Phalaenopsis flower has 2 pollinia. If you see dragon face just like me, dragons eyes are silhouettes of pollinia. They are covered by an anther cap. Phalaenopsis’s stigma is concave sticky surface located on the bottom of the column. The upper edge of the stigma is rostellum. Rostellum separates male and female parts to encourage cross-pollination. To enable pollinator to do its job Phalaenopsis has the following feature. Pollinia are attached to a sticky tab called viscidium by a thin stalk called caudicle. When an insect lands on the fancy lower petal (labellum or lip) and tries to reach potential nectar, it touches a viscidium that adheres to its body. It enables the pollinator to carry pollinia to another flower. While the insect is flying, the caudicle dries in such a way that when it enters into the next flower, pollinia are just in right position to stick to stigma surface. 

Moth orchid’s parts of a column

I detached anther cap and pollinia with viscidium and caudicle using a toothpick.

Phalaenopsis's detached anther cap and pollinia with viscidium and caudicle
Phalaenopsis’s detached anther cap and pollinia with viscidium and caudicle
Phalaenopsis flower after detaching anther cap and pollinia

Different orchids have very different design to attract specific pollinators and ensure pollination. For example, watch this short beautifully-made video about bucket orchid: link, or this nice one about bee orchid: link!

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