askST: What is this fruit which looks like a cherry?

Reader Helen Lim Gek Ling sent in a snapshot of this fruit to askST and wrote: "Appreciate your advice on what fruit this is? I found the cherry looking fruit at Bukit Timah."

Environment writer Audrey Tan checked with plant experts for an answer.

Scientists usually examine the different parts of the plant - such as its leaves, fruits, flowers and stems - before it can be conclusively identified.

But based on the photograph of the fruit, plant expert Jean Yong said it could likely belong to the group of plants from the genus Cayratia.

The exact species could either be the Cayratia japonica, Cayratia mollissima or Cayratia trifolia, said Associate Professor Yong, who is from the biology faculty at the Singapore University of Technology and Design.

 "As a general safety guide, fruits are deemed edible (to humans) if birds have been seen eating them.Cayratia trifolia has edible purple fruits.The leaves, according to literature, are edible especially the young leaves.

"The other species, Cayratia mollissima; the leaves can be added to make tea, in addition to the regular tea."

He added that these are climbing plants, which means they use other plants, rocks or man-made structures for support. None of them are endangered in Singapore.

Flowers, and not fruits, are usually the best characteristics to confirm the identity of a plant.

"In the absence of flowers, leaves, stems and even fruits can be used as proxy characters to establish the taxonomic identity with good certainty," Prof Yong said.

The shape of the leaf, as well as the overall shape of the plant - referred to as the plant habit - can also give scientists a better idea of the growth environment and more information about the plant species.

For example, plants in the same group can sometimes have different types of leaves. Plants which grow under full sun conditions are usually thicker and smaller, to reduce water loss through leaves, while plants that grow in the shade are usually thinner and broader, Prof Yong said.

Plants from the Acanthus genus, also known as sea holly, have the most variable leaf shape in the world.

"We assess the relative amount of light reaching specific areas within a mangrove by using mangrove sea holly leaf shapes," Prof Yong said.

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