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Fig 1: Thelymitra graminea (Photo credit: iStock/MichaelMajor)
The flower that follows the sun does so even on cloudy days
Seems that the orchids of Western Australia have never come across this quote, for they refuse to open on any day that is not warm and sunny. Cool weather? No, thanks. Overcast skies? Nope, not opening today. Sun down? Time to wrap up.
Smart move, actually. The pollinators will anyways be less active in cool weather and cloudy skies; hence, there is no point in opening the shop and waiting for customers who are not coming!
Fig 2: Thelymitra occidentalis (Photo credit: iStock/Anja Hennern)
The sun orchids belong to the genus Thelymitra, which consists of more than 100 species of terrestrial orchids endemic to Australia, including the Queen of Sheba orchid. Thelymitra’ literally means ‘woman’s hood.’ It is a nod to a fascinating adaptation in this plant, which is specifically designed to fool pollinators. Just like the Queen of Sheba orchid, every other sun orchid achieves pollination by deception. Even the script for executing the act of deceit is followed word-to-word. The naïve native bees head out, hoping to chance upon a native flower with abundance of pollen or nectar. While out there, they come across what looks like a flower of blue flax-lily (Dianella caerulea).
Fig 3: Dianella caerulea (Blue flax-lily) (Image credit: This image was taken by Harry Rose and is shared under license CC-BY-2.0)
The bees and the blue flax-lily have had a wonderful ‘give and take’ relationship for ages. In this flower, the pollen is hidden inside tubular, yellow anthers. The native bees grasp the anthers and dislodge the pollen by a special technique called buzz pollination or sonication. The technique is simple but ingenious: the bees contract their flight muscles and produce vibrations powerful enough to trigger a pollen shower. The delighted pollen-covered bees use their hind legs to comb pollen grains off their body and into their pollen baskets. The baskets will be taken to the beehive and converted into bee bread – the primary food source for the members of the hive. As for the flax-lily, the residual pollen will end up pollinating another flower – a ‘happily ever after’ end to a story of mutual benefit and trust.
Fig 4: A bee grasping the yellow anthers of a flower for buzz pollination. Notice the yellow pollen baskets attached to its hind legs. (Image credit: This image was taken by LadyDragonflyCC and is shared under license CC-BY-2.0)
Today, though, the bee will not have its happily-ever-after story. The flower it has landed upon is not a blue flax-lily, but its doppelgänger, the sun orchid. The blue coloration of petals and the yellow center exactly mimic a flax-lily flower.
Fig 5: Thelymitra vulgaris. Note the prominent yellow hood. (Photo credit: iStock/Samantha Haebich)
But the yellow center, the prominent ‘hood’ does not have any free pollen for the bees. The pollen is packed in masses with sticky pads, which will stick to the bee as it clings to the hood and tries out buzz pollination. However, once that’s done, there will no shower of pollen, or the filling up of pollen baskets. The dejected bee will walk away from the flower, yet again, without ever learning the lesson that everything that all that glitters is not gold, and every blue flower with a yellow center is not a blue flax-lily.
Fig 6: Thelymitra crinita (Photo credit: iStock/Anja Hennern)
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