Pollination of Citrus x microcarpa flowers

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Citrus x microcarpa is a natural hybrid, commonly known as Calamansi or Calamondin – or limau kesturi in Malay. The plant is grown for its small, round fruits whose juice is used in local cuisine or to make a sour drink. The flowers are white and fragrant.

Pollination of the flowers is by Stingless Bees (Trigona sp., family Apidae) and ants. The image above shows the anthers (pollen sacs) of the flower less the other parts. Note that the anthers have yet to pop and release their pollen. The images below show the anthers in the early stage of pollen release when the outline of the anthers are still intact (left) and a much later stage (right) when the outline is indistinct.

The image below shows the longisection of the flower with the various parts named. There is an ant near the ovary. In moving into the flower, it passed through the many anthers that have yet to release their pollen. In moving past the stigmatic head of the style, any pollen it picked up from an earlier visit to another flower will be transferred to the head, thus effecting cross pollination.

The Stingless Bees gather the pollen grains (below) that are rich in protein and fat to feed their larvae. At the flowers, these bees gather the pollen from the anthers and store them in the pair of pollen baskets located on the outer surface of the hind legs LINK.

The pollen baskets. known as corbicula, are the concave sections on the outer surface of the hind legs. In the case of the honey bee, it uses the forelegs and midlegs to scrape off pollen from its body, moves it to a special section of the hind legs, the pollen rake, after which it is compressed into a dense mass using a joint known as the pollen press. The compressed pollen, termed nuggets, are deposited into the pollen baskets. Check out this LINK for more details.

After a successful foraging trip (above), the two ‘baskets’ are tightly packed with large bulges of yellow pollen. These pollen loads (above) are brought back to the hive to be stored until needed.

The other visitor to these flowers are possibly ?Crematogaster ants. These ants wander among the stamens to seek out the flower nectar (above, below).

The ants as well as the Stingless Bees help in cross pollination when they transfer the pollen on their bodies from one flower to the stigma of the next.

YC Wee
Singapore
November 2015

One Response

  1. […] The bee lands on the anther (above), bites the end to force more pollen out (below). For details on how it uses its legs to comb the pollen grains from its body and stuff them into the pollen baskets, see this LINK. […]

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