| The color change of lips of KINRYOUHEN is a strategy for avoiding honeybees |
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Most KINRYOUHENs change colors after the pollination (it also happens when pollinia merely come off columns). It is thought that losing pollinia stimulates to secrete ethylene (a plant hormone), and then, anthocyanidins (a red pigment) are formed in the lips.
【C.hookerianum】Similar phenomenon can be seen in other flowers; especially Lantanas are famous for it. It changes colors of flower from yellow to red. Butterflies, the pollinators of this flower, do not visit the ones which have already been pollinated. This is because the pollinated flowers stop secreting honey, which attracts butterflies, with changing colors. Then, butterflies learn it and stop visiting the flowers with no honey. Not to let their pollinators waste the energies, the flowers have evolved.
As well as many other Cymbidiums, KINRYOUHENs change colors of lips after the pollination. The photographs show the change of lips' color, before and after the pollination. Not only they change colors but also bent their heads.
受粉前のキンリョウヘン 受粉後のキンリョウヘン A KINRYOUHEN usually has about ten flower stalks. To observe honeybees' behavior, I left two of the flower stalks and cut off the others. I took artificial pollination to one of them and left the other, made the number of flowers the same and faced them toward the same direction as possible.
The results show that the honeybees distinguish pollinated flowers and unpollinated ones. However, the two kinds are a little bit different in shape. In order to make them the same, I applied ethrell, an agricultural chemical which has the same effect as ethylene, to the lips. The flowers' shape remains the same although the lips' color turns red as if they are pollinated by the application of ethrell.
エスレル処理前 エスレル処理後 Using the ethrell treated flowers, I observed Japanese honeybees' behavior and found that more honeybees visited the treated flowers than before. This means the frequency of honeybees' visiting decreases when flowers change their shapes.
KINRYOUHENs give off a fragrance, which attracts honeybees, from their petals and calyxes. And let approaching bees to choose unpollinated flowers by changing the color of the lips. Of course, as plants have no intention, these mechanisms have developed through the long process of evolution.
