I had finally resolved the mystery shared in early August on the appearance of seed pods of the Centro vine (Centrosema molle) without seeing its flowers. This same phenomenon also took place with the Creeping Wood Sorrel (Oxalis corniculata), a small low-lying ground cover creeper, in my pot. At first, I thought I had missed the flowers when they were in bloom. In fact, there was no bloom. What actually happened was that both these plants were able to go through pollination in the unopened flowers, a biological trait known as cleistogamy. The opposite of cleistogamy is chasmogamy, which is what we normally would expect where flowers opened and get pollinated.

This observation was made possible because the vine was growing at my balcony area where I could make frequent check on it as well as watching it at close range. It helped when I was eager searching for the first flower in the midst of the thick and messy leaves. Moreover, I was quite eager to see the first flower. I was not aware that plant could actually pollinate itself in an unopened flower. This unusual trait had never cross my mind which made this observation rather exciting. The seed pods produced by unopened flowers appeared to be equally healthy judging from the length and size when compared to those from opened flowers seen in the wild. Apparently, unopened flower pollination is more efficient in term of energy saving since the plant did not have to utilise energy to put forward a full-bloom flower and is therefore an additional mean to help the plant to reproduce in sub-optimal environment; for the plants at my balcony, they were insufficient sunlight and small growth area in a pot.

Last Sunday, my Centro vine eventually showcase its first opened flower. The lone flower was located outside the balcony making it difficult to reach to take its picture. I had to stick my camera out of the balcony and take the picture without viewing it via my camera display screen. Fortunately, the images turned out quite well.

My observation concluded that flower buds that appeared inside the balcony under shade of the vine itself will undergo closed-flower pollination while those exposed to sunlight outside the balcony will go through the conventional opened-flower pollination.

Despite having observed this feature in the Creeping Wood Sorrel way back in time, it did not raise sufficient interest in me to search further for the answer until now. Another common plant that exhibit cleistogamy behaviour is the peanut plant (Arachis hypogaea).